Ventilation system for an automotive vehicle instrument panel

A ventilation system for circulating cooling air through the instrument panel of an automotive vehicle whereby electronic components within the instrument panel, such as the radio, tape deck and audio components which may include power transistors, are cooled thereby improving the durability and reliability of the electronic components, the system including portions that are common to the vehicle air conditioning and ventilation system, wherein provision is made for establishing a cooling air flow path through a circuitous air flow passage in the vehicle instrument panel to instrument panel components, including the radio chassis, which are packaged in a compact fashion in a restricted space.

TECHNICAL FIELD 
The invention relates generally to instrumentation for an automotive 
vehicle, particularly a ventilation system for electrical components 
within an automotive vehicle instrument panel. 
BACKGROUND OF THE INVENTION 
The passenger compartment of an automotive vehicle typically includes an 
instrument panel that is essentially a plastic structure with air flow 
ducts and components with electronic elements that generate heat, such as 
power transistors for radios. The components in the instrument panel 
include, in addition to a radio or tape deck, a cluster of direct reading 
sensor displays, control circuitry, air conditioning and cooling vent 
controls, and other vehicle control components arranged in a compact 
assembly. The components, which are assembled with economy of space, 
create a heat build-up in the interior of the instrument panel. Air 
surrounding the components typically is prevented from circulating freely 
through the instrument panel. 
The need for preventing an uncontrolled heat build-up in a restricted 
environment for electronic elements has been recognized, not only in the 
automotive industry but also in the aircraft industry. A cooling system 
for electronic components is required in order to avoid deterioration and 
to improve reliability. 
A cooling system adapted especially for aircraft is described in U.S. Pat. 
No. 5,253,484. Avionic equipment in the system of the '484 patent can be 
cooled notwithstanding the close proximity of the avionic elements, one 
with respect to the other, in an aircraft pilot's compartment. The system 
provides air flow ducts that form a part of a cooling system using a 
redundant cooling air flow supply, the flow being powered by electric 
fans. Each cooling air source has a back-up auxiliary fan in the event of 
failure of the primary fan. In this way, cooling air flow for critical 
avionic equipment necessary for safe flight is ensured. 
A typical example of a cooling system for controlling a temperature 
build-up for electronic control devices for an automotive vehicle is 
described in U.S. Pat. No. 4,616,693. Electronic components, such as power 
transistors, thermistors, and power resistances capable of generating 
significant amounts of heat can be cooled by arranging these elements on 
an air mixing baffle that controls the direction of flow of air from an 
air blower in an air conditioning system for the vehicle. The components 
are located on the baffle at a location where they are proximate to the 
exit air flow of the blower. 
BRIEF DESCRIPTION OF THE INVENTION 
Our invention comprises an improved plenum assembly adapted to be installed 
within the instrument panel of an automotive vehicle. The assembly 
comprises an intake air duct that receives fresh air from a fresh air 
inlet. An air blower powered by an electric motor in the engine 
compartment is adapted to transfer inlet air from an air inlet port to the 
upstream side of a heater core assembly. A blend door is located in the 
air flow path between the blower and the heater core assembly so that air 
can be directed either to the heater core assembly or to an air discharge 
port located in the vehicle engine passenger compartment. When the blend 
door or baffle is positioned to direct air from the blower to the heater 
core assembly, the air passes through the heater core and then is directed 
to a discharge opening in the vehicle passenger compartment. An air flow 
directing door or baffle controls the distribution of air to the interior 
of the passenger compartment or to the vehicle defroster air flow 
passages. 
Our improved assembly includes a flexible air flow conduit that 
communicates with the intake air flow path at a point upstream of the 
heater core assembly so that air may be transferred from a cold air 
portion of the air conditioning vent system of the vehicle to restricted 
areas within the instrument panel. Cool air then is delivered to confined 
areas occupied by electrical and electronic heat producing components such 
as the automotive radio. A pressure gradient in the air flow ducts creates 
a natural air flow through a flexible tubing or conduit. That pressure 
differential, of course, is increased when the blower is operative. 
If the automotive air conditioning system is operative, the outside fresh 
air enters the plenum assembly of the instrument panel after it passes 
through the evaporator of the air conditioning system. The air that passes 
through the flexible tubing or conduit then cools the radio chassis.

TICULAR DESCRIPTION OF THE INVENTION 
In FIG. 1, an air conditioning blower 10, powered by an electric motor 12, 
is adapted to be mounted on the fire wall 14 of an automotive vehicle. The 
wall 14 separates the engine compartment in the front of the vehicle from 
the vehicle passenger compartment. Air discharged by the blower passes 
through an air duct 16 and is delivered to a discharge opening 18 in the 
fire wall 14. 
In the perspective view of FIG. 1, the front of the vehicle is indicated by 
the directional arrow 20. 
Air enters the blower through an opening 22 formed in the fire wall 14, as 
seen in FIG. 1. 
A plenum assembly is generally indicated in FIG. 1 by reference numeral 24. 
It comprises a housing, usually formed of molded plastic, which defines an 
air entry port 26. Air is directed by the plenum assembly toward the front 
of the vehicle through opening 28, which is adapted to register with 
opening 22 when the plenum assembly is attached by bolts to the fire wall 
14. 
For purposes of illustration, the blower assembly and the plenum assembly 
are separated from the fire wall 14. The plenum assembly includes an air 
intake opening 30, which is adapted to register with the opening 18 on the 
fire wall when the plenum assembly is bolted to the fire wall. 
Located between the air entry port 26 and the opening 30 is a heater core 
32. Heater core supply and return tubes, shown at 34 and 36, extend toward 
the front of the vehicle and through opening 38 in the fire wall 14. 
Coolant from the engine circulates through the heater core tubes 34 and 36 
in known fashion. 
Air that is transferred by the blower to the opening 30 is directed by a 
blend door 40 to the air intake side of the heater core 32. The direction 
of the air flow path is indicated by the dotted directional arrow 42. 
Air passes from the outlet side of the heater core, as indicated by the air 
flow path designated by directional arrows 44. The heated air then is 
discharged through opening 46 formed in the plenum assembly. A flow 
directing door, not visible in FIG. 1, directs air either to the opening 
46 or to a heated air flow passage 48 extending to the vehicle defroster. 
The opening 46 can be seen best in FIG. 6. The flow directing door that 
controls the passage of air through the opening 46 is indicated in FIG. 6 
by reference numeral 52. The door 52 is adapted to be mounted for 
oscillation about a vertical axis along its inboard end. The angularity of 
the blend door with respect to its vertical axis is controlled by a lever 
assembly schematically shown at 54. The angularity of the lever assembly 
54 is controlled by a cable assembly 56, which may be driven by an 
actuator motor or by a driver-operated lever (not shown). 
In FIG. 5, the position of the heater core assembly, relative to the inlet 
opening and the discharge opening, can be seen. The blend door for 
controlling the opening 30 is diagrammatically illustrated in phantom as 
shown at 58. When it is in position "A", as shown in FIG. 5, inlet air is 
directed from the opening 30 to the inlet side of the heater core 32 
through internal passage structure defined by the plenum assembly. The 
flow path, which was indicated in FIG. 1 at 42, directs the intake air 
toward the right as seen in FIG. 5. When the blend door 58 is adjusted to 
position "B", as shown in FIG. 5, intake air flow to the inlet side of the 
heater core is blocked and air is directed to discharge opening 46. 
The blend door that controls the opening 46 is activated by a lever 
assembly as shown in FIG. 6 at 60. The defroster duct can be seen in FIG. 
6 at 62. It is in communication with the air flow stream through the 
opening 30 when the blend door 52 interrupts flow through the discharge 
opening 46. Lever assembly 60 is actuated by a cable assembly 64. Like the 
cable assembly 56, the cable assembly 64 can be actuated by a control 
motor or by a driver-operated lever. 
The flexible tube or conduit that conducts cooling air through the plenum 
assembly to the radio chassis is shown in FIG. 1 at 66. It is secured to 
an opening formed in the plenum wall 68 seen in FIG. 6. The flexible tube 
is adapted to be entrained through the restricted interior of the 
instrument panel assembly of the vehicle. Its output end is positioned, as 
shown schematically in FIG. 1, at the top of radio/tape deck/tape cassette 
chassis 70. Thus, cooling air from the blower passes through the flow path 
illustrated schematically at 42 in FIG. 1 and enters the inlet of the 
flexible conduit 66 at a point upstream from the heater core 32. Cooling 
air flows through the flexible conduit regardless of the position of door 
48. 
FIG. 3 shows the relationship between temperature rise in the vicinity of 
the radio and tape deck for a typical installation. Degrees Celsius is 
indicated on the ordinate and time in minutes is indicated on the 
abscissa. At a time of 15 minutes following initial operation, the 
temperature rises, as seen in FIG. 3, to about 75.degree. C. In contrast, 
the passenger compartment temperature, as indicated at 72, remains 
relatively constant at approximately 40.degree. C. 
After the instrument panel assembly has been modified to incorporate the 
improvements of our invention, the temperature versus time characteristic 
curve, which is indicated in FIG. 4, shows a temperature drop to a maximum 
value of about 56.degree. C. at an operating time of 15 minutes. This is 
in contrast to a temperature of about 37.degree. C. in the passenger 
compartment, as indicated at 72' in FIG. 4. 
FIG. 6 shows a vacuum servo motor 74, which has a vacuum pressure line 76 
and an actuator rod 78 connected to a lever assembly for an air flow 
directing door for the air inlet 26. FIG. 6 also shows a cover assembly 80 
for the defroster duct 62, which extends generally vertically, to conduct 
heated air to the vehicle windshield. Intake air enters the intake air 
duct 26 through openings formed in the vehicle cowl assembly at the base 
of the glass windshield. The lower margin of the windshield is 
schematically illustrated in FIG. 6 at 82. 
We have found that the flexible conduit 66 is capable of transferring cool 
air from the upstream air flow region of the heater core if it has a 
diameter of about 5/8 to 3/4 inch. It may be formed of a variety of 
commercially available plastic materials and it can be routed through the 
restricted interior of the instrument panel assembly without crimping. 
If desired, provision may be made for connecting the interior of the plenum 
assembly to a negative pressure region through a vacuum pressure conduit. 
The vacuum pressure conduit can be connected to the air conditioning vent 
system at a point that is subjected to a pressure lower than ambient 
pressure. This has the potential of improving ventilation inside the 
entire instrument panel as well as concentrating cooling at specific 
locations, such as at the location of the radio chassis. Installation 
testing shows that temperatures of a radio chassis have been lowered from 
a temperature range of about 170.degree. F. to 180.degree. F. to about 
140.degree. F. even without the presence of a low pressure conduit for 
ventilating the entire interior of the instrument panel assembly. 
It will be apparent to persons skilled in the automotive art that 
modifications to the embodiment we have disclosed may be made without 
departing from the scope of our invention. 
Having described a preferred embodiment of our invention what we claim and 
desire to secure by U.S. Letters Patent is: