Information
-
Patent Grant
-
6668917
-
Patent Number
6,668,917
-
Date Filed
Monday, January 10, 200024 years ago
-
Date Issued
Tuesday, December 30, 200320 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 165 42
- 165 43
- 165 201
- 165 202
- 165 203
- 165 204
- 165 240
- 165 222
- 165 288
- 454 93
- 454 121
- 062 156
- 237 2 A
- 237 2 R
- 236 91 C
- 236 91 D
-
International Classifications
-
Abstract
An energy-saving method for operating a climate control system includes reporting an ambient outside temperature from a first temperature sensor to a controller unit and reporting a climate control air temperature from a second temperature sensor to the controller unit. The control unit performs an algorithm to define a control criterion value in response to the ambient outside temperature. A non-refrigeration cycle based heating element is activated to provide heated air to an interior surface of a windshield if the climate control air temperature is above the control criterion value. Moreover, a refrigeration cycle based cooling element and the non-refrigeration cycle based heating element are activated to provide the heated air to the interior surface of the windshield if the climate control air temperature is at or below the control criterion.
Description
The present invention is related to an automobile defrost/deice operation.
BACKGROUND
Passenger comfort and fuel efficiency have set forth increasing demands on automotive heating, ventilating and air-conditioning (HVAC) systems. It is a primary goal of most HVAC systems to detect and avoid internal climate conditions that will result in windshield/window fogging.
As a result, newer and improved automotive HVAC systems are configured to communicate with a plurality of sensors and control actuators. For example, an automotive HVAC system may have a plurality of temperature sensors for measuring the internal temperature of the automobile, the outside temperature and the temperature at various locations within the ductwork of the HVAC system.
In addition, the system will also have user manipulated control settings for varying air temperature, fan speed, direct airflow, vary air recirculation ratio and other relevant settings.
Accordingly, and in order to prevent undesired fogging conditions, the HVAC system must be able to prevent and/or rectify such a condition. Moreover, the relationship of the factors causing such a condition varies significantly.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an operational protocol for an automotive HVAC system.
Another object of the present invention is to provide an energy-saving defrost/deice operation for use in automobile.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will now be described, by way of example only, with reference to the accompanying drawings in which:
FIG. 1
is a graph illustrating condensation and non-condensation zones;
FIG. 2
is a graph illustrating possible air manipulation scenarios for providing heated air in response to a defog request;
FIG. 3
is a graph illustrating a fogging prediction algorithm;
FIG. 4
is a graph illustrating an application of the fogging prediction algorithm illustrated in
FIG. 3
;
FIG. 5
is an illustration of a schematic for a climate control system utilizing the fogging prediction algorithm of
FIG. 4
;
FIG. 6
is a block diagram of the automatic defog control loop illustrated in
FIG. 5
;
FIG. 7
is a graph illustrating refrigeration and nonrefrigeration operating zones for a defog control system;
FIG. 8
is a block diagram of the energy-saving defog control loop employed by the climate control system illustrated in
FIG. 5
; and
FIG. 9
is a flowchart illustrating an exemplary embodiment of a command sequence for the climate control system illustrated in FIG.
5
.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The fogging of the interior surfaces of an automobile's windshield and/or windows is a result of moisture condensing on the interior surfaces of the windows. Water vapor will condensate on a surface whose temperature is below the dew point of the air.
The dew point is the temperature of saturated moist air at the same pressure and humidity ratio as the given mixture.
Referring now to
FIG. 1
, a graph
10
illustrates the relationship between surface temperature, air moisture or humidity and points where the moisture will condensate on the surface creating fog.
Graph
10
defines a “saturation line”
12
the limits or boundary defining a fogging situation for a given temperature and humidity. Graph
10
defines a condensation zone
14
and a non-condensation zone
16
.
Accordingly, and in order to prevent or rectify a fogging situation, the temperature and/or the humidity must be manipulated to a point which will avoid and reduce the occurrence of an undesired fogging situation.
The heating ventilating and air conditioning system (HVAC) and climate control system of current automobiles are arranged to alter the air temperature, humidity and air flow direction in response to a defog request.
In response to a defog request, incoming air is first cooled and then heated prior to directing it to the windshield surface. This process may lead to unnecessary cooling and subsequent re-heating of the air which results in an increased load upon the vehicles HVAC system, namely, the unneeded activation of the air-conditioning system and subsequent reheating of the cooled air.
Referring now to
FIG. 2
, an example of such a situation is illustrated by a graph
18
. In a first scenario, air at point A is 32 degrees Fahrenheit with a 100 percent relative humidity. The air is then heated to 90 degrees Fahrenheit which changes its relative humidity to 12 percent. This is illustrated by point B. Note point B is now in the non-condensation zone
16
.
In a second scenario, the air at point A is cooled by the vehicles HVAC system to a temperature of to 25 degrees Fahrenheit with a relative humidity of 100 percent. This air is illustrated by point C. Then the air at point C is heated to 90 degrees Fahrenheit, which changes its relative humidity to 9 percent which and illustrated by point D.
In comparing scenario
1
to scenario
2
there is only a 3% difference in the relative humidity of the air at points B and D. However, scenario
2
requires the activation of the air-conditioning system as well as an additional heating requirement to reach 90 degrees. This results in a higher energy load upon the vehicles HVAC system that also affects the vehicles fuel efficiency.
Moreover, if the automobile is an electric vehicle or hybrid electric vehicle (HEV) where energy conservation is critical, the needless activation of the air-conditioning system adversely affects the vehicles energy load.
Currently, automobile control systems are configured to activate the cooling system in response to a defog/deice request in order to reduce the humidity of the air.
However, and as illustrated in
FIG. 2
, the more efficient response is to only heat the fresh air without activating the air-conditioning system (scenario
1
). Moreover, and in most cases, the ambient air in winter conditions is very dry.
In accordance with the present invention, a criterion γ for determining whether or not to activate the automobiles air-conditioning system in response to a defog or deice request, has been developed. Criterion γ can be defined as a function of ambient air temperature, ambient humidity, discharge air temperature and discharge humidity which yields the following equation:
γ=
f
(
T
ambient
, φ
ambient
, T
air
, φ
air
) Equation 1
Equation 1 can be further simplified if there is only one humidity sensor in the HVAC air duct wherein a fogging prediction algorithm is utilized.
Referring now to
FIGS. 3-6
, a fogging prediction algorithm for use with the instant application is illustrated. Here, the humidity ratio is defined as ω, the degree of saturation is defined as μ, and the saturation humidity ratio is defined as ω
s
.
A dew point prediction model yields the following equations:
ω=μω
s
ω
s
=f
(
T
)
μ=φ/{1+(1+φ)ω
s
/0.62198}
The saturation humidity ratio (ω
s
) with respect to temperature is defined using predetermined reference values. For example, the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) provides a publication wherein the thermodynamic properties of moist air are available.
In addition, and for the convenience of programming, the following correlation between the saturation humidity ratio (ω
s
) and temperature (T) was developed for use in the instant application:
ω
s
=0.004+2.84121×10
−4
T
+6.92664×10
−6
T
2
+1.75612×10
−7
T
3
+4.61324×10
−9
T
4
Referring now to
FIGS. 3 and 4
, the air humidity ratio is determined by measuring the temperature T and the humidity φ. Then using the above equations the ratio at saturation is calculated. The degree of saturation μ is derived and the humidity ratio ω is determined.
Then the temperature at the windshield must be determined.
FIGS. 5 and 6
illustrate one possible implementation of a HVAC system employing the dew point prediction model previously discussed wherein a temperature sensor
50
is positioned on the inside surface of the windshield.
Alternatively, an approximate algorithm of estimating windshield temperature T
w
can be defined as follows: T
w
=g(T
ambient
, T
cabin
, V) where V is the vehicle speed, and T
w
=(1−x)T
ambient
+xT
cabin
. Here, x is a weight factor and is a function of the vehicle speed as defined by the equation x=h(V).
The next step in the sequence is to determine the humidity ratio ω′
s
=f(T
w
)
Finally, the fogging criterion is determined by the following equation:
γ=ω′
s
/ω Equation 2
Criterion γ is now defined and is used to determine whether the climate of an interior passenger compartment of an automobile is in a fogging, a fogging warning or a non-fogging zone. A constant value which is based upon a calibration that is dependent upon the vehicles design defines the boundary values for fogging zones. For purposes of illustration the constant value used herein to define the fogging boundary zones is 0.8. It is, of course, contemplated in accordance with the present invention that the constant value may vary as it is dependent upon the vehicles design.
For example, and using a constant value of 0.8, γ≧1 defines a fogging zone, 0.8<γ<1 defines a fogging warning zone and γ<0.8 defines a no fogging zone.
Referring now to
FIGS. 5 and 6
, an automotive HVAC system
20
using the above fogging prediction algorithm is illustrated. Here system
20
receives an air input from a fresh air passage
22
and a recycled air passage
24
. An air circulation door
26
controls the mixture of the fresh to recycled air that is inputted into the system. A blower or fan
28
forces the fresh and or recycled air into a main HVAC unit
30
that contains an evaporator
32
for cooling the air. Blower
28
is controlled by either a user manipulated control switch or command signals received from a controller.
A heating element
34
is positioned down stream from evaporator
32
. A blend door
35
is positioned to direct the air to and/or away from heating element
34
.
A temperature sensor
36
and a humidity sensor
38
are positioned to take air temperature and humidity readings. The location of humidity sensor
38
may vary in order to provide the most accurate humidity reading of the passenger compartment of an automobile. A mode door
40
is positioned to direct the air or a portion thereof to a defog pathway
42
, a panel pathway
44
or a floor pathway
46
.
Defog pathway
42
is positioned to deliver forced air to an automobile windshield
48
.
A second temperature sensor
50
is positioned to take temperature readings at or around the windshield surface. Alternatively, and as previously discussed, the temperature of the windshield may be estimated using an empirical equation wherein sensor
50
is no longer necessary. An ambient air temperature sensor
52
is positioned to provide exterior or fresh air temperature readings.
Sensors
36
,
38
,
50
and
52
provide readings to a thermal controller
54
. Thermal controller
54
controls the positioning of air circulation door
26
, blend door
35
and mode door
40
. In addition, thermal controller
54
also activates evaporator
32
and heating unit
34
.
A humidity set point
56
also provides an input into controller
54
. In addition, a defog/deice request
58
is also inputted into thermal controller
54
.
Accordingly, and once a defog or deice request is received, controller
54
determines through the application of criterion γ whether to activate the air-conditioning
32
and heating system
34
or the heating system only. As discussed, γ is determined by a control algorithm and accordingly, the activation of the heating and/or refrigeration systems is based upon the ambient condition, namely, heating of air and or dehumidification of the air. Once γ is determined, a control algorithm of controller
54
manipulates system
20
.
If γ≧1 controller
54
actuates mode door
40
into a defog position. If, 0.8>γ<1, controller
54
actuates mode door
40
into a defog and floor position. Moreover, and in response to the value of γ, controller
54
will also adjust recirculation door
26
and, if necessary, adjust the speed of blower
28
.
Referring back now to Equation 2: γ=ω′
s
/ω it is noted that If γ>0.8 then the air-conditioning system of the automobile needs to be activated to cool the air prior to its being heated and directed towards the windshield surface.
On the other hand, if γ<0.8 then the air-conditioning system of the automobile is not required and the air only needs to be heated prior to it being directed to the windshield surface.
As an alternative, Equation 1 can also be simplified if there is no humidity sensor in the system yielding the following equation:
γ=
f
(
T
ambient
, T
air
) Equation 3
Finally, an empirical equation can be applied as follows:
T
air
=0.5
T
ambient
+55 (all temperatures are in Fahrenheit) Equation 4
Accordingly, equation 4 provides a graph
60
as illustrated in FIG.
7
. Graph
60
defines a criterion line Beta that defines a boundary, based upon ambient and discharge air temperatures, between a non-refrigeration or no AC operating zone
62
and a refrigeration or AC operating zone
64
.
Therefore, the temperature reading from sensor
36
can be utilized in the following manner.
If the temperature reading from sensor
36
(the air temperature at discharge) is less than or equal to 0.5T
ambient
+55, then the system is in refrigeration operating zone
64
and the air-conditioning system should be activated in response to a defog or deice operation request.
Conversely, if the temperature reading from sensor
36
is greater than 0.5T
ambient
+55, then the system is in non-refrigeration operating zone
62
and accordingly, there is no need for the air-conditioning system to be activated in response to a defog or deice request; therefore, only the heating system should be activated.
Accordingly, a thermal controller of a climate control system in an automobile can be preprogrammed to activate or not activate the air-conditioning system in response to a defog or deice request. Moreover, the thermal controller is programmed to utilize an energy-saving algorithm wherein activation of the air-conditioning system can be controlled in response to air temperature readings exclusively. Therefore, there is no need for humidity sensors in the energy-saving algorithm.
Moreover, since there is no requirement for a humidity sensor there is less sensor and electrical interface required between a controller and the HVAC system of an automobile. In addition, the software required to operate the controller is also made less complicated. Here a controller algorithm simply applies two temperature readings to a simplistic equation to define a refrigeration and non-refrigeration zones.
In accordance with the present invention, the climate control system operates under a criterion that determines whether or not to activate the air-conditioning system in response to a defog or deice request. Moreover, the determination of the criterion is based upon two temperature readings.
Simply put, and based upon temperature input, if criterion γ exceeds a given value, then the system will not activate the air-conditioning system in response to a defog or deice request. This prevents unnecessary cooling and subsequent reheating of the discharge air, which, in turn, prevents unnecessary power consumption. Similarly if criterion γ is less than the given value, the air-conditioning system will be activated in response to such a request.
Referring now to
FIG. 8
, a block diagram
66
illustrates the energy-saving defog/deice operation strategy and control scheme in accordance with the present invention. Thermal controller
54
receives temperature inputs (T
ambient
and T
discharge
) and using equation for which defines Beta, non-refrigeration operating zone
62
and refrigeration operating zone
64
(FIG.
7
), thermal controller
54
determines whether or not to activate the cooling system.
Moreover, and referring now to
FIG. 9
a flowchart
68
illustrates an automatic defog control logic for use with controller
54
and with the energy-saving algorithm of the instant application. A first step
70
receives the following inputs: the current status of the AC unit (on/off); the current status of the auto defog (on/off); the current blower status (on/off); Ta the ambient temperature reading from sensor
52
(FIG.
5
); Tc the cabin temperature from sensor
50
(FIG.
5
); Td the discharge temperature from sensor
36
(FIG.
5
); vehicle speed in mph; and the relative humidity from sensor
38
.
A second step or decision node
72
determines if the blower unit is on, if so, a third step
74
calculates ω
s
(the saturated humidity ratio at temperature sensor
50
(Tc)) wherein ω
s
=f(Tc).
A fourth step
76
calculates the humidity ratio ω based upon ω
s
and using the equations:
ω=μω
s
ω
s
=f
(
T
)
μ=φ/{1+(1+φ)ω
s
/0.62198}
A fifth step
78
estimates the windshield temperature Wt. (Wt=(1−x)Ta+xTd). Wherein x is a weighted factor that can be calibrated, for example, if vehicle speed (V) is less than or equal to 5 mph x=0.5; if V is greater than 70 mph x=0.9; and if 5<V=<70 mph, then x=0.5+28/V. In addition, and at higher vehicle speeds the ambient air temperature has a greater effect upon windshield temperature.
Alternatively, the windshield temperature can be determined from a temperature sensor position on, in or near windshield
48
.
A sixth step
80
calculates ω′
s
.
A seventh step
82
Calculates γ=ω′
s
/ω
An eighth step
84
determines whether or not γ is less than 0.8. If so, a ninth step
86
determines whether the air-conditioning has been manually activated. If so, the current status is maintained. If not, a next step
88
determines whether the auto defog is on. If so, a next step
90
turns auto defog off. If the auto defog is off already, status is maintained.
If on the other hand, gamma (γ) is greater than or equal to 0.8 a decision node
92
determines whether or not the air-conditioning system is on. If yes, the current status is maintained. If not, an energy-saving algorithm
94
, as contemplated for use in accordance with an exemplary embodiment of the present invention, is employed.
A first step
96
of energy-saving algorithm
124
calculates Beta the air-conditioning system actuation criterion that defines non-refrigeration operating zone
62
and refrigeration operating zone
64
. (FIG.
7
).
A next step
98
determines whether the temperature reading from sensor
50
is greater than Beta. If so, the non-AC operating zone is maintained. If on the other hand, the temperature rating from sensor
50
is less than or equal to Beta, then the AC operating zone is maintained.
Alternatively, and in order to alter the control characteristics and or software which is utilized to operate the control systems and or command sequences for automotive HVAC system
20
, a disk drive
100
is coupled to thermal controller
54
wherein a software upgrade may be installed into the system of thermal controller
54
. This will allow improvements to the operation strategy and or software to be easily installed into the vehicles operational system. Moreover, upgrades may be mailed to a consumer negating the need for the owner to bring their vehicle into an authorized dealer for a service upgrade. Such an implementation may also negate the need for the vehicle being brought in for factory recalls which are primarily due to new software and or control systems.
While the invention has been described with reference to a preferred embodiment, 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 adapt 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 embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
Claims
- 1. A method of providing heated air to a windshield surface, said method comprising:a) reporting an ambient outside temperature from a first temperature sensor to a controller unit having an algorithm; b) reporting a climate control air temperature from a second temperature sensor to said controller unit; c) defining a control criterion value with said algorithm in response to only said ambient outside temperature; d) activating a heating element to provide said heated air if said climate control air temperature is above said control criterion value; and e) activating a cooling element and said heating element to provide said heated air if said climate control air temperature is at or below said control criterion value.
- 2. The method as in claim 1, wherein said control criterion value is equal to one half of said ambient outside temperature plus a constant value of fifty-five where said ambient outside temperature and said constant value are in degrees Fahrenheit.
- 3. The method as in claim 1, further comprising:controlling said controller unit to provide a first portion of the heated air from fresh air and a second portion of the heated air from recycled air in response to said control criterion value.
- 4. The method as in claim 1, further comprising:controlling said controller unit to adjust a blower speed in response to said control criterion value.
- 5. The method as in claim 1, further comprising:controlling said controller unit to control a blend door to control an amount of the heated air exposed to said heating element in response to said control criterion value.
- 6. An energy-saving method for operating a climate control system for providing heated air to an interior surface of a windshield of a vehicle, said method comprising:a) receiving a plurality of inputs, wherein said plurality of inputs includes an ambient outside temperature, a climate control discharge temperature, and an operational status of a defogging control system; b) determining a first control criterion value, said first control criterion value being dependent only upon said ambient outside temperature; c) activating a heating element in response to said operational status and if said first control criterion value is less than said climate control discharge temperature; and d) activating an air-conditioning system and said heating element in response to said operational status and if said first control criterion value is greater than said climate control discharge temperature.
- 7. The method as in claim 6, wherein said first control criterion value is equal to one half of said ambient outside temperature plus a constant value of fifty-five where said ambient outside temperature and said constant value are in degrees Fahrenheit.
- 8. The method as in claim 6, further comprising:providing a first portion of the heated air from fresh air and a second portion of the heated air from recycled air in response to said first control criterion value.
- 9. The method as in claim 6, further comprising:adjusting a speed of said fan in response to said first control criterion value.
- 10. The method as in claim 6, further comprising:controlling an amount of the heated air exposed to said heating element in response to said first control criterion value.
- 11. An energy-saving method for use with a climate control system for providing heated air to an interior surface of a windshield of a vehicle, said method comprising:a) receiving an ambient outside temperature from a first temperature sensor; b) receiving an interior air temperature from a second temperature sensor positioned at a point in an air passage, said point being positioned downstream from a heating element, and said heating element being positioned down stream of a cooling element; d) determining a criterion value, said criterion value being dependent upon only said ambient outside temperature; e) controlling said heating element to add heat to said heated air if said interior air temperature is greater than said criterion value; and g) controlling said cooling element to cool said heated air before said heating element adds heat to the heated air if said interior air temperature is less than or equal to said criterion value.
- 12. The method as in claim 11, further comprising:providing a first portion of the heated air from fresh air and a second portion of the heated air from recycled air in response to said criterion value.
- 13. The method as in claim 11, further comprising:adjusting a blower speed in response to said criterion value.
- 14. The method as in claim 11, further comprising:adjusting a blend door to control an amount of the heated air exposed to said heating element in response to said criterion value.
- 15. The method as in claim 11, wherein said criterion value is equal to one half of said ambient outside temperature plus a constant value of fifty-five where said ambient outside temperature and said constant value are in degrees Fahrenheit.
US Referenced Citations (25)