U.S. patent application number 13/124142 was filed with the patent office on 2011-08-25 for condenser fan control system.
This patent application is currently assigned to AGCO SA. Invention is credited to Gabriel Menier.
Application Number | 20110203538 13/124142 |
Document ID | / |
Family ID | 40133723 |
Filed Date | 2011-08-25 |
United States Patent
Application |
20110203538 |
Kind Code |
A1 |
Menier; Gabriel |
August 25, 2011 |
CONDENSER FAN CONTROL SYSTEM
Abstract
A method of controlling a fan for cooling a condenser in an air
conditioning system is provided. A compressor serves to drive a
refrigerant around a fluid circuit which includes the condenser.
The duty cycle of the compressor is measured over a period of time
to determine a utilisation ratio which reflects the demand on the
air conditioning system at that time. The fan is driven at a speed
which is no lower than a minimum fan speed which is associated with
the calculated utilisation ratio and ambient temperature.
Therefore, the demand on the system is determined and exploited
without any additional pressure sensors.
Inventors: |
Menier; Gabriel; (Beauvais,
FR) |
Assignee: |
AGCO SA
BEAUVAIS
FR
|
Family ID: |
40133723 |
Appl. No.: |
13/124142 |
Filed: |
October 13, 2009 |
PCT Filed: |
October 13, 2009 |
PCT NO: |
PCT/EP09/63357 |
371 Date: |
April 14, 2011 |
Current U.S.
Class: |
123/41.11 ;
62/89 |
Current CPC
Class: |
F25B 49/027 20130101;
F25B 2600/0251 20130101; F25B 2700/21175 20130101; B60H 1/00828
20130101; F25B 2600/111 20130101 |
Class at
Publication: |
123/41.11 ;
62/89 |
International
Class: |
F01P 7/02 20060101
F01P007/02; F25D 17/06 20060101 F25D017/06 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 24, 2008 |
GB |
0819471.4 |
Claims
1. A method of controlling a cooling fan in an air conditioning
system which comprises a fluid circuit having a compressor and a
condenser cooled by the fan, the method comprising measuring the
ratio of the time that the compressor is active to the time that
the compressor is inactive over a predetermined period of time, and
operating the fan at a speed which is no lower than a predetermined
minimum fan speed associated with said ratio.
2. A method according to claim 1, wherein measuring said ratio
includes sensing an electrical current supplied to the
compressor.
3. A method according to claim 1, wherein operating the fan
includes obtaining the predetermined minimum fan speed from a
lookup table.
4. A method according to claim 1, wherein the air conditioning
system further comprises a temperature sensor located in the volume
to be cooled by the system.
5. A method according to claim 1, wherein the air conditioning
system further comprises a temperature sensor located in the fluid
circuit downstream of an evaporator.
6. A method according to claim 4, further comprising the steps of:
activating the compressor in response to the sensed temperature
exceeding an upper temperature threshold; and deactivating the
compressor in response to the sensed temperature falling below a
lower temperature threshold.
7. An air conditioning system operating according to the method of
claim 1.
8. A tractor comprising an air conditioning system according to
claim 7, wherein the fan also serves to cool an engine cooling
radiator and/or a oil cooling device.
Description
[0001] The invention relates to air conditioning systems and in
particular, but not exclusively so, to a closed loop method of
control of a cooling fan for blowing relatively cool air over a
condenser within a fluid circuit of an air conditioning system.
[0002] Air conditioning systems for use in buildings and vehicles
are well developed and typically comprise a thermodynamic heat pump
which removes heat from a low temperature source and expels it to a
high temperature sink with the help of external mechanical work. A
more detailed explanation of the principle behind air conditioning
systems can be found at the web page
www.en.wikipedia.org/wiki/refrigeration cycle.
[0003] Air conditioning systems typically comprise a condenser in a
fluid circuit through which a refrigerant flows such as Freon. Air
is passed over the condenser so as to exchange heat from the fluid
circuit to the air. The air is driven through the evaporator by a
fan which, in modern systems is driven by an electric motor or, in
the case of vehicle applications, by a viscous friction coupling to
the engine drive shaft.
[0004] The fan often serves also to pass air over a water-filled
radiator for the cooling of an engine and/or over an oiled-filled
radiator for cooling of transmission oil for example. Therefore,
depending on the operating conditions of the vehicle the demands on
the various cooling systems can vary enormously.
[0005] It is known to sense the various operating parameters of the
vehicle and drive the cooling fan at a predetermined minimum fan
speed dictated by the cooling system element with the greatest
demand.
[0006] It is an object of the invention to provide an improved
method of controlling a cooling fan in an air conditioning system
which can be implemented with little or no further cost to the
existing hardware.
[0007] In accordance with the invention there is provided a method
of controlling a cooling fan in an air conditioning system which
comprises a fluid circuit having a compressor and a condenser
cooled by the fan, the method comprising the steps of: [0008]
measuring the ratio of the time that the compressor is active to
the time that the compressor is inactive over a predetermined
period of time; [0009] operating the fan at a speed which is no
lower than a predetermined minimum fan speed associated with said
ratio.
[0010] The invention includes the recognition that the utilisation
ratio of the compressor within the air conditioning system is
directly representative of the air conditioning demand on the
cooling fan which forces air through a cooling package. Therefore,
by calculating the on-to-off ratio of the compressor over a preset
duration the minimum fan speed requirement for the air conditioning
system can be determined
[0011] Preferably, the ratio can be measured by sensing an
electrical current supplied to the compressor. The current supplied
to the compressor is representative of the activity state, that is
whether the compressor is on or off. Therefore, by simply
monitoring this current the periods of activation and deactivation
can be determined and thus the utilisation ratio can be
calculated.
[0012] For each ratio, or range of ratios, the corresponding
minimum fan speed can be stored in a look up table.
[0013] Any air conditioning system may operate to the method of the
invention. In particular a vehicle such as tractor comprising an
air conditioning system can implement the method in accordance with
the invention. In this case the fan may also serve to cool the
engine cooling radiator and/or an oil cooling device.
[0014] Further advantages of the invention will become apparent
from the reading the following description of a specific embodiment
with reference to the figures in which:
[0015] FIG. 1 is a tractor; and
[0016] FIG. 2 is a schematic diagram of an air conditioning system
fitted to the tractor of FIG. 1 and operating in accordance with
the method of the invention.
[0017] A tractor 10 comprises a cab 11 in which the driver sits
during operation. The tractor comprises an air conditioning system
which serves to cool the air within the volume of the cab 11.
[0018] The tractor further comprises a hood 12 which encloses an
engine (not shown) together with a cooling system.
[0019] With reference to FIG. 2, the tractor cooling system
comprises the air conditioning system 14, an oil cooler 15 and an
engine cooling radiator 22. A fan 18, driven by electric motor 19
forces air in the direction represented by the arrow 20 in through
the front grill of the tractor and in a rearward direction.
[0020] It will be appreciated that the fan may alternatively be
driven by other propulsive means which can vary the output speed.
For example, a viscous clutch may replace the electric motor
19.
[0021] Turning to the air conditioning system 14 in FIG. 2, a fluid
circuit 21 filled with a refrigerant material comprises a condenser
16. The refrigerant is passed through the fluid circuit in the
direction of arrow 24 and through the condenser 16 under a pressure
created by compressor 25.
[0022] The condenser 16 serves to cool and condense super heated
vapour passing there through. The fan 18 serves to draw air from
the front of the tractor 10, in through the engine cooling radiator
22, the oil cooling radiator 15 and the condenser 16.
[0023] Continuing on from the condenser, the refrigerant passes
through the fluid circuit on to an expansion valve (not shown) and
an evaporator (also not shown), the latter being located within the
roof structure of the cab 11. The relatively cool liquid vapour
mixture which passes through the evaporator is heated by the
relatively warm air of the cab 11 thereby cooling the operator's
environment.
[0024] Heated vapour exiting the evaporator is then passed on to
the compressor 25 where the fluid circuit continues over.
[0025] It should be appreciated that the hardware of the air
conditioning system 14 is well known and that the invention relates
to a method of driving the fan 18.
[0026] In accordance with known air conditioning systems the
compressor operates periodically so as to maintain the cab
temperature within a predetermined desired range set by the driver.
A temperature sensor 30 which is physically located within the
fluid circuit senses the temperature of the heated vapour which
exits the evaporator. This is representative of the thermal load on
the AC circuit 14. Alternatively, the temperature sensor 30 may be
located in within the cab.
[0027] The temperature readings are communicated to a compressor
control unit 40.
[0028] A control dial (not shown) is adjusted by the driver to set
a desired temperature. This dictates upper and lower threshold
temperatures at which the compressor switches on and off
respectively. For example, if the drive sets the target temperature
at 20.degree. C., the compressor control unit 40 activates the
compressor 25 when the sensed temperature exceeds 21.degree. C. and
deactivates the compressor 25 when the sensed temperature falls
below 25.degree. C.
[0029] By continual monitoring of the temperature and appropriate
operation of the compressor 25, and thus the air conditioning
system 14, the temperature within the cab 11 can be maintained
within the desired range.
[0030] The rate at which energy can be dissipated from the
condenser 22 is dependant upon the relative temperature of the air
in the flow and upon the speed of the air flow driven by the fan
18. The former is affected by the temperature of the
environment.
[0031] The fan speed is controlled by a fan control unit 50. The
speed set is sufficient to deliver the rate of cooling demanded by
the various elements to be cooled.
[0032] The inventor has recognised that the activity of the
compressor 25 is directly related to the cooling requirements
demanded by the air conditioning system 14. The heat dissipation
achieved by the condenser 16 is dependent upon the temperature and
speed of the air being forced over the condenser by the fan 18. The
heat dissipation required from the condenser is dependent upon the
activity of the compressor and the temperature within the cab
driving the heat transfer into the AC system 14.
[0033] Therefore, in accordance with the invention, the utilisation
ratio of the compressor 25 is calculated and exploited by the fan
control unit 50. By measuring the electrical current supplied to
the compressor 25, the fan control unit 50 measures the ratio of
the time that the compressor is active to the time that the
compressor is inactive over a predetermined period of time.
[0034] For each ratio, or range of ratios, there is associated a
minimum fan speed requirement of the air conditioning system 14.
For example if the utilisation ratio of the compressor is 20% then
the fan speed requirement may be 1500 rpm. In another case wherein
the utilisation ratio is 80% the fan speed requirement may be 2200
rpm. These values are stored in a lookup table.
[0035] The demands of the oil cooling radiator 15 and water cooling
radiator 22 may also be taken into account by appropriate sensing
of the parameters involved, for example oil and water temperature.
Therefore the fan control unit 50 operates motor 19 at a speed
which is dependant upon a number of sensed parameters. In this
example the component which demands the greatest air flow from the
fan 18 dictates the speed at which the fan is actually driven.
[0036] In one example in which the tractor is hauling a heavy load
on a cold day the cooling demands of the air conditioning system 14
are low whereas the cooling demands of the engine cooling radiator
22 are high. Therefore fan 18 is driven at a speed to sufficiently
cool the water in radiator 16.
[0037] In another example the tractor is hauling a light load on
hot day in which the cooling demands of the air conditioning system
are high and the cooling demands of the oil and engine coolers 15,
22 are relatively low. In this case the fan 18 is driven at a speed
determined in accordance with the invention.
[0038] Although the invention is described above in relation to a
tractor it should be appreciated that the invention is equally
applicable to any vehicle comprising an air conditioning
system.
[0039] Furthermore the invention is equally applicable to air
conditioning systems not related to vehicles.
[0040] In summary there is provided a method of controlling a fan
for cooling a condenser in an air conditioning system without any
additional hardware measuring fluid pressure for example. A
compressor serves to drive a refrigerant around a fluid circuit
which includes the condenser. The duty cycle of the compressor is
measured over a period of time to determine a utilisation ratio
which reflects the demand on the air conditioning system at that
time. The fan is driven at a speed which is no lower than a minimum
fan speed which is associated with the calculated utilisation
ratio. Therefore, the demand on the system is determined and
exploited without any additional sensors.
[0041] From reading the present disclosure, other modification will
be apparent to persons skilled in the art. Such modifications may
involve other features which are already known in the field of air
conditioning control systems and component parts therefore and
which may be used instead of or in addition to features already
described herein.
* * * * *
References