Automatic temperature and humidity regulation – Thermostatic – Hot and cold
Reexamination Certificate
1999-12-07
2001-05-22
Tanner, Harry B. (Department: 3744)
Automatic temperature and humidity regulation
Thermostatic
Hot and cold
C236S09100C, C062S131000, C062S133000
Reexamination Certificate
active
06234398
ABSTRACT:
TECHNICAL FIELD
This invention relates to the control of an automatic Heating-Ventilation-Air-Conditioning (HVAC) system for a motor vehicle, and more particularly to a control that does not include a cabin air temperature sensor.
BACKGROUND OF THE INVENTION
With a motor vehicle automatic HVAC control, the operator sets a desired temperature for the vehicle cabin, and an electronic control module controls the blower speed, air discharge temperature and air delivery mode based on the set temperature and a number of parameters including outside air temperature, solar loading, and a measure of the actual air temperature in the cabin.
A typical prior art control is illustrated by the block diagram of
FIG. 1A
, the calculation diagram of
FIG. 1B
, and the control output diagram of FIG.
1
C. As indicated in
FIG. 1A
, a calibrated constant K and a number of terms based on the ambient or outside air temperature (Tamb), solar loading (Tsolar), desired temperature setting (Tset), and in-car temperature (Tin-car) are developed from sensor information and calibrated gains F
1
-F
4
, and combined at summing junction
10
to form a Program Number. The Program Number is applied to a Table
12
which outputs control settings for blower speed (BLOWER), air discharge temperature (DISCHARGE) and air delivery mode (MODE). The control settings are applied to the HVAC controller
14
, which in turn, is connected to the CABIN
16
by a number of air delivery ducts
18
. The HVAC controller
14
measures the actual air discharge temperature with one or more duct temperature sensors
20
, and controls a refrigerant compressor and temperature mix doors (not shown) to satisfy the commanded discharge temperature(s). Such controls, in turn, influence the temperature in the CABIN
16
, which is detected by the in-car temperature sensor
22
. As indicated in
FIG. 1B
, the Tin-car, Tsolar and Tamb terms are considered as corrections, and oppose the sum of K and the Tset terms in computing the Program Number. As indicated on the horizontal axis of
FIG. 1B
, increasingly lower Program Numbers correspond to increased cooling demand, and increasingly higher Program Numbers correspond to increased heating demand.
FIG. 1C
illustrates in general how the Table
12
derives the control settings for BLOWER, DISCHARGE and MODE, based on the Program Number. In the illustration, MODE comprises two control settings: one for air inlet source (RECIRC or OUTSIDE) and one for air outlet location (PANEL, BI-LEVEL or FLOOR). The blower speed (BLOWER) varies between high and low settings, as does the air discharge temperature (DISCHARGE).
While the outside air temperature and the solar loading can be determined with a fair degree of accuracy, the cabin (in-car) temperature is difficult to accurately determine because the temperature sensing element has to be hidden and aspirated with cabin air, and typically ends up being installed in a less than ideal location from a sensing performance standpoint. For these and other reasons, in-car temperature measurements frequently exhibit a lagging response time and drift, which can degrade the performance of the overall control system, possibly requiring repeated operator adjustment of the temperature setting in order to achieve the desired comfort level. Furthermore, in-car temperature sensing significantly adds to the hardware, calibration and installation cost of the system.
Accordingly, it has been proposed to eliminate the conventional in-car temperature sensor. For example, the U.S. Pat. No. 5,810,078, issued Sep. 22, 1998, discloses a control system which calculates a theoretical in-car temperature by solving a coupled set of ordinary differential equations, and then adjusts the system control variables in closed-loop fashion based on the deviation of the calculated in-car temperature from the desired in-car temperature. However, such an approach necessitates additional sensors, is subject to the usual closed-loop stability concerns, and requires a relatively high degree of computational capability by the system controller.
Accordingly, what is desired is a control system which eliminates the conventional in-car temperature sensor and the performance degradation due to its lagging response time and drift, while not increasing the overall cost and complexity of the system.
SUMMARY OF THE INVENTION
The present invention is directed to an improved performance and cost-effective control for an automatic motor vehicle HVAC system in which the system variables are controlled without regard to a measured in-car temperature during steady-state conditions, and in which the steady-state control is modified during transient conditions by a time-dependent open-loop compensation term, referred to herein as INCAR. The initial value of INCAR, a target value and a time rate of change are initialized as a function of environmental and system conditions at the onset of the transient condition. At ignition key-on, INCAR is initialized in accordance with an estimate of the in-car temperature, and exponentially adjusted toward a predetermined reference temperature (target) corresponding to the expected cabin air temperature at the conclusion of the transient, and at a rate corresponding to the expected rate of change of cabin air temperature. Preferably, INCAR is also adjusted for door opening and closing. At ignition key-off, INCAR is initialized at its current value, and exponentially adjusted toward a target temperature based on ambient air temperature and solar loading, to form a basis for in-car temperature initialization at the next ignition key-on. For extended key-off periods, an average of the temperature readings of the air discharge temperature sensors may be used to initialize INCAR.
REFERENCES:
patent: 4345714 (1982-08-01), Kojima
patent: 5003785 (1991-04-01), Petri et al.
patent: 5209398 (1993-05-01), Drees
patent: 5810078 (1998-09-01), Knutsson et al.
patent: 5944256 (1999-08-01), Arai et al.
patent: 6012295 (2000-01-01), Isobe et al.
patent: 6055817 (2000-05-01), Wieszt
patent: 6123146 (2000-09-01), Dias
Kelly Sean Michael
Pawlak, III John Lawrence
Delphi Technologies Inc.
Griffin Patrick M.
Tanner Harry B.
LandOfFree
Motor vehicle automatic HVAC control with open loop... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Motor vehicle automatic HVAC control with open loop..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Motor vehicle automatic HVAC control with open loop... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2551571