U.S. patent application number 09/756381 was filed with the patent office on 2002-01-10 for air conditioning system and method of controlling same.
Invention is credited to Gielda, Thomas P., Harte, Shane A., Huang, Yong, Klapp, Andrew J..
Application Number | 20020002833 09/756381 |
Document ID | / |
Family ID | 26875136 |
Filed Date | 2002-01-10 |
United States Patent
Application |
20020002833 |
Kind Code |
A1 |
Klapp, Andrew J. ; et
al. |
January 10, 2002 |
Air conditioning system and method of controlling same
Abstract
An air conditioning (A/C) system and method of controlling same
is provided for a vehicle. The A/C system includes an evaporator, a
desiccant dryer located downstream of the evaporator, and a
compressor fluidly connected to the evaporator. The A/C system also
includes a plurality of sensors to provide inputs relating to
temperature of the evaporator and relative humidity of an occupant
compartment of the vehicle. The A/C system further includes an
electronic control unit electrically connected to the sensors to
receive the inputs therefrom and electrically connected to the
desiccant dryer and the compressor to turn the desiccant dryer and
the compressor On and Off to control the temperature and relative
humidity of air to the occupant compartment.
Inventors: |
Klapp, Andrew J.; (Trenton,
MN) ; Harte, Shane A.; (Farmington, MI) ;
Gielda, Thomas P.; (Brighton, MI) ; Huang, Yong;
(Ann Arbor, MI) |
Correspondence
Address: |
Daniel H. Bliss
Bliss McGlynn, P.C.
Suite 600
2075 West Big Beaver Road
Troy
MI
48084
US
|
Family ID: |
26875136 |
Appl. No.: |
09/756381 |
Filed: |
January 8, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60179236 |
Jan 31, 2000 |
|
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|
Current U.S.
Class: |
62/203 |
Current CPC
Class: |
B60H 3/024 20130101;
F25B 1/02 20130101; B60H 1/00785 20130101; F24F 3/1411 20130101;
B60H 2003/028 20130101 |
Class at
Publication: |
62/203 |
International
Class: |
F25B 041/00 |
Claims
What is claimed is:
1. An air conditioning (A/C) system for a vehicle comprising: an
evaporator; a desiccant dryer located downstream of said
evaporator; a compressor fluidly connected to said evaporator; a
plurality of sensors to provide inputs relating to temperature of
said evaporator and relative humidity of an occupant compartment of
the vehicle; and an electronic control unit electrically connected
to said sensors to receive the inputs therefrom and electrically
connected to said desiccant dryer and said compressor to turn said
desiccant dryer and said compressor On and Off to control the
temperature and relative humidity of air to the occupant
compartment.
2. An A/C system as set forth in claim 1 wherein said compressor is
a variable displacement compressor.
3. An A/C system as set forth in claim 1 wherein said sensors
include a sunload sensor disposed in the occupant compartment.
4. An A/C system as set forth in claim 1 wherein said sensors
include a blend door position sensor.
5. An A/C system as set forth in claim 1 wherein said sensors
include an ambient temperature sensor.
6. An A/C system as set forth in claim 1 wherein said sensors
include an interior temperature sensor disposed in the occupant
compartment.
7. An A/C system as set forth in claim 1 wherein said sensors
include a relative humidity sensor disposed in the occupant
compartment.
8. An A/C system as set forth in claim 1 wherein said sensors
include an evaporator temperature outlet sensor.
9. An A/C system as set forth in claim 1 wherein said sensors
include a blower fan sensor.
10. An A/C system as set forth in claim 1 including a pulse width
modification valve connected to the compressor and electrically
connected to said electronic control unit.
11. A method of controlling an air conditioning (A/C) system for a
vehicle comprising: providing an evaporator, a desiccant dryer
located downstream of the evaporator, and a compressor fluidly
connected to the evaporator; receiving a plurality of sensed inputs
from sensors relating to temperature of the evaporator and relative
humidity of an occupant compartment of the vehicle; and controlling
the temperature and relative humidity of air to the occupant
compartment based on the received inputs by turning the desiccant
dryer and the compressor On and Off.
12. A method as set forth in claim 11 including the step of
calculating a thermal load on the vehicle prior to said step of
controlling.
13. A method as set forth in claim 12 including the step of
calculating an evaporator temperature outlet of the evaporator and
deriving a humidity ratio out of the evaporator.
14. A method as set forth in claim 13 including the step of
calculating the humidity ratio of the occupant compartment of the
vehicle.
15. A method as set forth in claim 14 including the step of
calculating a difference in the humidity ratio between the
evaporator and the occupant compartment.
16. A method as set forth in claim 15 including the step of
determining whether the difference in the humidity ratio is greater
than zero.
17. A method as set forth in claim 16 including the step of turning
the desiccant dryer Off and the compressor On if the difference in
the humidity ratio is greater than zero.
18. A method as set forth in claim 16 including the step of
determining whether the difference in the humidity ratio is less
than a humidity ratio maximum value.
19. A method as set forth in claim 18 including the step of turning
the desiccant dryer On and the compressor On if the difference in
the humidity ratio is less than the humidity ratio maximum
value.
20. A method as set forth in claim 19 including the step of
recalculating the evaporator outlet temperature of the evaporator.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] The present invention claims the priority date of copending
U.S. Provisional Patent Application Ser. No. 60/179,236, filed Jan.
31, 2000.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to air conditioning
systems and, more specifically, to an air conditioning (A/C) system
and method of controlling the A/C system.
[0004] 2. Description of the Related Art
[0005] It is known to provide an air conditioning (A/C) system for
a vehicle. Typically, the A/C system is used to control cooling in
an interior, cabin, or occupant compartment of the vehicle. The A/C
system generally includes a condenser, compressor, evaporator, and
expansion valve to remove heat from air and cool the air to the
occupant compartment. The A/C system may include a desiccant dryer
to remove moisture from the air.
[0006] It is also known to provide a mechanism to regenerate
desiccant materials in the desiccant dryer by heating them and
boiling off water vapor. An example of desiccant air conditioning
for a motorized vehicle is disclosed in U.S. Pat. No. 6,029,462 to
Denniston. In this patent, a complicated array of desiccant wheels
and enthalpic wheels are required to regenerate the desiccant
materials. However, this is difficult to achieve from a packaging
standpoint in a motor vehicle. Also, in these systems, the only
heat source sufficient to burn off the water vapor is engine
exhaust, which is undesired.
[0007] An alternative to heating the desiccant materials of the
desiccant dryer is to use vacuum to boil off the water vapor. A
motor vehicle has vacuum available for most operating conditions.
However, in a vacuum strategy, an important factor is the
regeneration frequency. In order to boil off the water vapor, it is
necessary to cycle rapidly between adsorption and desorption
stages. This is necessary because desorption is an endothermic
process. In a near vacuum, there is no mechanism to provide the
heat required. As a result, it is necessary to cycle the system
according to the equation: 1 f = m H2O * h vaporisation m desiccant
* Cp dessicant * ( T evap - 32 )
[0008] Otherwise, the water present in the desiccant dryer will ice
up and prevent further desorption. Therefore, there is a need in
the art to provide an air conditioning system and method of
controlling the air conditioning system to cycle the desiccant
dryer.
SUMMARY OF THE INVENTION
[0009] Accordingly, the present invention is an air conditioning
(A/C) system for a vehicle. The A/C system includes an evaporator,
a desiccant dryer located downstream of the evaporator, and a
compressor fluidly connected to the evaporator. The A/C system also
includes a plurality of sensors to provide inputs relating to
temperature of the evaporator and relative humidity of an occupant
compartment of the vehicle. The A/C system further includes an
electronic control unit electrically connected to the sensors to
receive the inputs therefrom and electrically connected to the
desiccant dryer and the compressor to turn the desiccant dryer and
the compressor On and Off to control the temperature and relative
humidity of air to the occupant compartment.
[0010] One advantage of the present invention is that an A/C system
having a desiccant dryer is provided to control relative humidity
of air in an occupant compartment of a vehicle. Another advantage
of the present invention is that the A/C system also includes a
variable displacement compressor. Yet another advantage of the
present invention is that a method is provided for regeneration of
a desiccant dryer of the A/C system. Still another advantage of the
present invention is that the A/C system receives inputs from a
plurality of sensors such as a humidity sensor, sunload sensor,
temperature sensors, etc. and provides outputs to cycle the
desiccant dryer On and Off to regenerate the desiccant
materials.
[0011] Other features and advantages of the present invention will
be readily appreciated, as the same becomes better understood,
after reading the subsequent description taken in conjunction with
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a diagrammatic view of an air conditioning (A/C)
system for a vehicle controlled by a method, according to the
present invention.
[0013] FIG. 2 is a diagrammatic view of sensors of the A/C system
of FIG. 1 controlled by the method, according to the present
invention.
[0014] FIG. 3 is a perspective view of a desiccant dryer, according
to the present invention, for the A/C system of FIG. 1.
[0015] FIG. 4 is a perspective view of another embodiment,
according to the present invention, of a desiccant dryer for the
A/C system of FIG. 1.
[0016] FIG. 5 is a perspective view of yet another embodiment,
according to the present invention, of a desiccant dryer for the
A/C system of FIG. 1.
[0017] FIG. 6 is a flowchart of a method, according to the present
invention, of controlling the A/C system of FIG. 1.
[0018] FIG. 7 is a psychometric chart used in conjunction with the
method and A/C system of FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
[0019] Referring to the drawings and in particular FIGS. 1 and 2,
one embodiment of an air conditioning (A/C) system 10 is shown for
a vehicle (not shown) such as a motor vehicle. In general, control
of air temperature and air flow (and, to a lesser extent, humidity)
within the vehicle is accomplished using various actuators to
effect the temperature and flow of air supplied to an interior,
cabin, or occupant compartment 46 of the vehicle. The A/C system 10
includes an air handling case or housing 12 and a variable speed
blower motor or fan 14 for moving air through the housing 12. The
A/C system 10 also includes an evaporator 16 disposed in the
housing 12 and spaced from the fan 14 to receive moving air
therethrough from the fan 14 and to cool the air. The A/C system 10
also includes a desiccant dryer 18 spaced after or downstream from
the evaporator 16 to receive moving air therethrough from the
evaporator 16. The desiccant dryer 18 removes moisture or water
vapor from the air. The A/C system 10 includes a heater core 20
disposed in the housing 12 and spaced after or downstream from the
desiccant dryer 18 to heat the air and a door 22 to allow or
prevent moving air from the desiccant dryer 18 from passing through
the heater core 20. It should also be appreciated that the
desiccant dryer 18 is located after the evaporator 16 because it is
the position of highest relative humidity in the A/C system 10 and
the absorption rate of water vapor by standard desiccant materials
(e.g., silica gels) is a stronger function of relative humidity
than any other parameter (temperature or ambient pressure).
[0020] The A/C system 10 also includes an expansion valve 22
fluidly connected to the evaporator 16 and a receiver dryer 24
fluidly connected to the expansion valve 22. The A/C system 10
includes a condenser 26 fluidly connected to the receiver dryer 24
and a compressor 28 fluidly interconnecting the condenser 26 and
the evaporator 16. The compressor 28 is preferably a 160 cc
variable displacement swashplate compressor. The A/C system 10
includes an electronically controlled valve 30 connected to the
compressor 28 to alter the capacity of the compressor 28 by varying
the pressure in the crankcase of the compressor 28. The
electronically controlled valve 30 is preferably a pulse width
modified (PWM) 0.7 Amp solenoid device that allows discharge
pressure to bleed into the crankcase of the compressor 28. It
should be appreciated that by varying the PWM signal properties
increased bleed will cause the crankcase pressure to increase. It
should also be appreciated that changing the crankcase pressure
adjusts the angle of the swashplate, thus reducing the displacement
of the compressor 28. It should further be appreciated that
refrigerant flows through the condenser 26, compressor 28,
evaporator 16, expansion valve 22, and receiver dryer 24.
[0021] The A/C system 10 includes an electronic control unit 32
electrically connected to the electronically controlled valve 30.
The electronic control unit 32 includes a microprocessor (not
shown) having an analog input section (not shown), digital input
section (not shown), digital output section (not shown), and pulse
width module (PWM) section (not shown). The electronic control unit
32 is electrically connected to an ignition switch (not shown),
which is in turn, electrically connected to a power source (not
shown) such as a battery of the vehicle. The electronic control
unit 32 receives several inputs such as control setting input 34,
temperature input 36, relative humidity (rh) input 38, and sun load
input 40. It should be appreciated that the electronic control unit
32 preferably continually monitors the state of the ignition switch
and the state of the A/C system 10. It should also be appreciated
that the A/C system 10 further includes an arrangement of air flow
doors that may be driven by vacuum motors (not shown) between their
various vacuum, partial vacuum and no vacuum positions or by an
electric servomotor (not shown) in a conventional manner. It should
further be appreciated that each of the above components is in
communication with the housing 12 and associated ducting (not
shown) in order to control temperature, the direction of air flow
and the ratio of fresh or intake air to recirculated air.
[0022] Referring to FIG. 2, the A/C system 10 includes a plurality
of sensors for monitoring the A/C system 10 and providing signals
to the electronic control unit 32. The sensors include a plurality
of temperature sensors to provide the temperature input 36 and sun
load input 40. The temperature sensors include an ambient
temperature sensor 42a, an evaporator temperature sensor 42b, an
outlet temperature sensor 42c, and an occupant or cabin temperature
sensor 42d, which are representative of ambient (outside) air
temperature, evaporator outlet temperature, discharge air
temperature, and interior (cabin) temperature. The sensors also
include a relative humidity sensor 44 to provide the rh input 38.
The relative humidity sensor 44 is located in the occupant
compartment or cabin 46 of the vehicle. The sensors include a
plurality of door position sensors to provide input to the
electronic control unit 32. The door position sensors include a
rear door position sensor 48a and a blend door position sensor 48b.
The sensors also include a blower flow rate sensor 49 to provide
input to the electronic control unit 32. The sensors are
electrically connected to the analog section of the electronic
control unit 32. It should be appreciated that the sensors provide
an analog input to the electronic control unit 32.
[0023] The A/C system 10 includes a plurality of buttons (not
shown) set manually by the operator of the vehicle to provide the
control setting input 34 which is representative of power (off),
desired temperature (temp), air conditioning (a/c), automatic
control (auto), fan, defrost (def), mode, and recirculation
(recirc). The buttons are located in the occupant compartment 46 of
the vehicle and are electrically connected to the digital input
section of the electronic control unit 32. It should be appreciated
that the buttons provide a digital input to the electronic control
unit 32.
[0024] The A/C system 10 also includes a display (not shown) to
display information from the electronic control unit 32 such as
temperature, mechanisms on or actuated, etc. The display is
electrically connected to the digital output section of the
electronic control unit 32. The display may include a plurality of
lights (not shown) such as light emitting diodes (LEDs) to indicate
which buttons are on.
[0025] The A/C system 10 also includes a plurality of mechanisms
(not shown) such as actuators, motors, clutches and solenoids to
control various components of the A/C system 10 such as air flow
doors, blower, a/c clutch, etc. The mechanisms are electrically
connected to the electronic control unit 32. It should be
appreciated that the electronic control unit 32 controls the doors
and the blower or fan 14 to regulate the temperature and flow of
air into the cabin or occupant compartment 46 of the vehicle. It
should be appreciated that, for automatic control of the
temperature and flow of air in the occupant compartment 46 of the
vehicle, the A/C system 10 monitors conditions within and outside
the occupant compartment 46 and generates signals to control the
plant actuators according to the conditions as indicated by the
sensors.
[0026] Referring to FIG. 3, the desiccant dryer 18 may be of a
carousel type having a carousel 50 with a plurality of, preferably
two, active chambers 52 and a regeneration chamber 54. The
desiccant dryer 18 includes a rotary motor (not shown) to move the
carousel 50 around to the regeneration position. The desiccant
dryer 18 is located in the housing 12 of the A/C system 10 and
connected to a source of vacuum for the regeneration chamber 54. It
should be appreciated that the motor is controlled by the
electronic control unit 32. It should also be appreciated that the
desiccant dryer 18 is compact and lightweight. It should further be
appreciated that the desiccant dryer 18 is able to cycle rapidly
and hold a partial vacuum.
[0027] Referring to FIG. 4, another embodiment of the desiccant
dryer 18 is shown. Like parts of the desiccant dryer 18 have like
reference numerals increased by one hundred (100). In this
embodiment, the desiccant dryer 118 may be of a plate type having a
plurality of plates 156 forming a plurality of, preferably four,
active chambers 158 and two regeneration chambers 160. The airflow
is closer to the regeneration chambers 160. The desiccant dryer 118
includes a linear motor (not shown) to move plates 162 to have heat
transfer from the active chambers 158 to the regeneration chambers
160. The desiccant dryer 118 is located in the housing 12 of the
A/C system 10 and connected to a source of vacuum for the
regeneration chambers 160. It should be appreciated that the motor
is controlled by the electronic control unit 32. It should also be
appreciated that the desiccant dryer 118 is compact and
lightweight. It should further be appreciated that the desiccant
dryer 118 is able to cycle rapidly and hold a partial vacuum.
[0028] Referring to FIG. 5, yet another embodiment of the desiccant
dryer 18 is shown. Like parts of the desiccant dryer 18 have like
reference numerals increased by two hundred (200). In this
embodiment, the desiccant dryer 218 may be of a plate and tube type
having a plurality of tubes 264 forming a plurality of, preferably
four, active chambers and a plurality of tubes 266 forming a
plurality of, preferably four, regeneration chambers. The desiccant
dryer 218 is located in a cavity (not shown) in the ceiling or roof
(not shown) of the vehicle or under the seats (not shown) of a
driver and passenger occupant (not shown). The desiccant dryer 218
may include a perforated ceiling 268 if mounted in the roof of the
occupant compartment 46. It should be appreciated that, although
efficiency is lost due to the lower relative humidity in the
vehicle, the cabin or occupant compartment 46 has more room to
accommodate the desiccant dryer 218. It should also be appreciated
that the tubes 266 are connected to a source of vacuum. It should
further be appreciated that the desiccant dryer 218 is able to
cycle rapidly and hold a partial vacuum.
[0029] Referring to FIG. 6, a method, according to the present
invention, of controlling the A/C system 10 is shown. The method
starts or begins in block 300. The temperature sensors, in car
humidity sensor, the blend/fresh air door position sensors, blower
motor speed sensor, and sun load sensors are used by the method to
calculate the total thermal or heat load in block 300. The thermal
load can be approximated by direct calculation, but it is more
common to calculate a pseudo-load number, termed the Valavg, as
follows:
Valavg=Offset-K1*Sun+K2*T.sub.set+K3*T.sub.amb+K4*T.sub.cabin
[0030] The method advances to block 302 and the total heat load on
the A/C system 10 is used by the method to calculate a target
evaporator outlet temperature (T.sub.evap) in block 302. This can
be done, again by direct calculation from the thermal load, or more
commonly by a look-up table based on the Valavg as follows:
1 Valavg Tevap 50 35 100 80 130 85 195 160
[0031] In block 304, the target evaporator outlet temperature is
used to calculate HRevap. Using the dew point from a psychometric
chart as illustrated in FIG. 7, it is possible to deduce the
corresponding humidity ratio:
HR.sub.Tevap=.function..sub.psych-chart (T.sub.evap)
[0032] In block 306, the method calculates the humidity ratio
(HR.sub.cabin) in the cabin or occupant compartment 46. The
humidity ratio (HR.sub.cabin) in the occupant compartment 46 can
also be determined from psychometric calculations or appropriate
approximations:
HR.sub.cabin=.function..sub.psych-chart (T.sub.cabin,
Rh.sub.cabin)
[0033] If the humidity ratio calculated for the occupant
compartment 46, as illustrated in FIG. 7, is greater than 0.009
kg.sub.water/kg.sub.air, there is a need to reduce the humidity in
the occupant compartment 46. This is achieved by conditioning the
air into the occupant compartment 46. A simplified method is as
follows (an offset humidity ratio of 0.008 is used to ensure
convergence around 0.009):
HR.sub.desired=0.008-(HR.sub.actual-0.009)
[0034] Comparing the two humidity ratios, it is possible to
determine whether or not the desiccant dryer 18, 118, 218 is
required. If HR.sub.Tevap is greater that HR.sub.desired, then the
desiccant dryer 18, 118, 218 needs to be activated. If the
difference is greater than the desiccant dryer 18, 118, 218 is
capable of, then the evaporator exit temperature (T.sub.evap) needs
to be reduced.
[0035] In block 308, the method calculates the difference in
humidity ratio (.DELTA.HR) between blocks 304 and 306 as
follows:
.DELTA.HR=HR.sub.desired-HR.sub.evap
[0036] The method then advances to block 310 and determines whether
.DELTA.HR is greater than a predetermined value such as zero. If
so, the method then advances to block 312 and turns the desiccant
dryer 18, 118, 218 Off and the compressor 28 On.
[0037] If not, the method advances to diamond 314 and determines
whether .DELTA.HR is less than a maximum predetermined value
(.DELTA.HRmax). .DELTA.HRmax is a value determined from the
capacity of the desiccant dryer 18,118,218 as follows:
.DELTA.HRmax=(dm.sub.H20/dt)/(dm.sub.air/dt)
[0038] Where: dm.sub.H20/dt=Humidity removal capacity of the
desiccant dryer/hr; and
dm.sub.air/dt=Air flow rate.
[0039] If so, the method then advances to block 316 and turns the
desiccant dryer 18, 118, 218 On and the compressor 28 On.
[0040] If not, the method advances to block 118 and recalculates
the evaporator outlet temperature (T.sub.evap). The new evaporator
outlet temperature is determined by the dewpoint of the sum of
HR.sub.desired and .DELTA.HRmax as follows:
T.sub.evapmodifid=.function..sup.-1.sub.pych-chart
(HR.sub.desired+.DELTA.- HRmax)
[0041] The method then advances to block 320 and turns the
desiccant dryer 18, 118, 218 On and the compressor 28 On. It should
be appreciated that the electronic control unit 32 turns the
compressor On and Off via an electromagnetic clutch, which controls
the outlet evaporator temperature via the valve 30. It should also
be appreciated that by turning the desiccant dryer 18, 118, 218 On,
the regeneration chambers are connected to vacuum to boil off the
water vapor from the desiccant materials therein. It should further
be appreciated that, as illustrated in FIG. 7, using a standard A/C
loop, the A/C system 10 with the compressor 28 can cool the air to
point #4 and then using the desiccant dryer 18, 118, 218 to
isothermally dehumidify the air to point #1.
[0042] The present invention has been described in an illustrative
manner. It is to be understood that the terminology, which has been
used, is intended to be in the nature of words of description
rather than of limitation.
[0043] Many modifications and variations of the present invention
are possible in light of the above teachings. Therefore, within the
scope of the appended claims, the present invention may be
practiced other than as specifically described.
* * * * *