Automotive heating and air conditioning assembly with improved air flow and temperature control

An improved film type air temperature control valve for an automotive HVAC assembly has a flexible, apertured belt that wraps closely around both faces of a heater core case internal to the HVAC housing. Winding and unwinding of the belt around the heater core case, and across a heater core bypass passage, simultaneously opens up more of the bypass passage as it closes off more of the heater core faces, and vice versa. Because of the close conformance of the belt to and across the heater core faces, both faces of the always hot heater core can be completely closed to direct or indirect air flow, preventing any undesired incidental heating of the air flow.

TECHNICAL FIELD 
This invention relates to automotive heating and air conditioning 
assemblies in general, and specifically to such an assembly that improves 
the air temperature control efficiency by use of a extensible and 
retractable belt than interacts with the heater core in a novel fashion to 
better control the air flow through and around the heater core. 
BACKGROUND OF THE INVENTION 
Heating, ventilation and air conditioning assemblies in automobiles 
typically include a large, molded plastic housing, often called an HVAC 
housing, which serves to duct and control forced air flow, as well as to 
contain various heat exchangers and controls therefor. Three different 
control systems interact to control air flow through the housing and the 
temperature thereof. Furthest upstream, a fresh air/recirculated air 
control determines whether a blower pulls in outside air, or recirculates 
internal air, or some combination thereof. A greater proportion of 
recirculated air speeds up the heating or cooling process. Furthest 
downstream, a so called mode control determines whether forced air is 
ultimately directed through air outlets upwardly at the windshield, 
straight forward at the occupant, downward at the feet, or some 
combination thereof. Between the air inlet and outlet, a pair of separate 
heat exchangers contained within the housing serve to temper the drawn in 
air, cooling it, heating it, or both, as determined by a separate 
temperature control. Typically, all three sets of controls have been 
simple flapper doors which rotate back and forth to open up or close off 
various passages and openings, or to direct air flow in one direction or 
the other, or both. Recently, designs have been proposed which replace the 
flapper door with a mechanism similar to a window shade, generally called 
a film valve, that shifts back and forth to cover or uncover various 
openings and passages. This presents obvious advantages of compactness, 
and also allows a more finely adjustable opening and closing. Replacement 
of the downstream air inlet control and of the upstream air outlet control 
with film valves is fairly straightforward. The intermediate control 
system used to determine the air temperature presents unique challenges, 
however, because of the way in which the air flow must be controlled 
through and around the two heat exchangers involved. 
Air temperature is controlled and determined with two heat exchangers 
carried within the housing, including an evaporator core, which can be 
turned on and off along with the rest of the air conditioning system, and 
a heater core, which is generally always activated and hot. The heater 
core traditionally has diverted engine coolant flowing through it whenever 
the engine is running, since heater core shut off valves represent an 
added expense, and also since the heater core can in fact be used in the 
summer to partially reheat refrigerated air that would otherwise be too 
cold for the desired interior temperature. The evaporator core typically 
is large enough in area to fill the entire cross sectional area internal 
to the housing, and is located downstream of the heater core. Therefore, 
all forced air passes through the evaporator core first, regardless of 
whether the evaporator core is activated. This is not a drawback, since 
the evaporator can be turned off when it is not desired to cool the air. 
Furthermore, having the evaporator core permanently sitting in the air 
flow path can present a benefit, even in winter, since it allows outside 
air to be cooled and dried before being heated, which is useful when 
defrosting the windshield. On the other hand, having the heater core 
always active can present a drawback. Known air temperature control 
systems do not completely isolate or insulate the air flow from the heater 
core, even when it is not desired to heat the air at all, as when the 
system is set for rapid cooling. Both older, flapper door temperature 
valves, and newer, proposed film type temperature valves controls, leave 
the downstream face of the heater core exposed to the cooled air flow 
leaving the evaporator core. This is generally true even when the cooled 
air flow is blocked from flowing directly through the heater core. Air can 
still flow or "scrub" across the exposed downstream face of the core, 
picking up some significant heat, when it would be preferable that it pick 
up little or none. 
A good example of a conventional arrangement of evaporator core, heater 
core, and temperature door can be seen in U.S. Pat. No. 4,978,061, in FIG. 
1 of that patent. An upstream evaporator core fills the whole cross 
sectional area of the housing, while a downstream heater core fills only 
about half, leaving a bypass passage around the heater core. A flapper 
door between the two cores moves from a down position, for full cold, to 
an up position, for full heat, and can also take up intermediate positions 
to divide the air flow up partially through, and partially around the 
heater core. In the down, full cold position, the upstream face only of 
the heater core is covered, and the bypass passage is left fully open. 
This is enough to block direct air flow through the heater core, but does 
not cover the downstream heater core face or prevent some of the bypassed 
air flow from swirling down and "scrubbing" across the exposed heater core 
back face to pick up some heat. Furthermore, as the door rotates between 
intermediate angular positions, it is not as precise or "linear" in its 
division of air flow between the heater core and the bypass passage as 
would be ideal for the best temperature control. The room needed for a 
door to swing in an arc also occupies a good deal of housing volume. 
Proposed film valve designs for air temperature modulation have the 
potential for improved compactness and more precise air flow division, but 
still leave the downstream face of the heater core undesirably exposed to 
air flow. Examples may be seen in U.S. Pat. Nos. 5,326,316 and 5,162,020. 
Each uses a film valve to progressively cover or uncover the front face of 
the heater core, thereby determining how much air flows directly through 
it. The design disclosed in U.S. Pat. No. 5,564,979 does not use the film 
belt itself to directly block or unblock the bypass passage around the 
heater core, using a separate flapper type valve located upstream of the 
heater core instead. U.S. Pat. No. 5,162,020 does use the film valve to 
directly open and close the bypass passage, but basically replicates a 
conventional flapper door by pivoting one edge of a film sheet in front of 
the heater core and sliding its other edge back and forth, so that the 
film becomes a traveling leg of a triangle, in effect, moving over 
approximately the same pattern that a flapper door would follow. Again, 
neither design blocks the rear face of the heater core. Essentially the 
converse is disclosed in another patent, U.S. Pat. No. 5,154,223, where a 
continuous belt is located in front of the downstream face of the heater 
core, between the heater core and the air outlets, rather than behind the 
upstream face of the heater core. The heater core sits in a mid point 
position in the case, defining two bypass passages around the heater core. 
The one belt does double duty as a temperature control and air outlet 
control, acting both to progressively block off the downstream face of the 
heater core, while concurrently opening or closing the bypass passages and 
the various air outlets. Here, in so called full cold mode, it is the 
downstream face of the core that is blocked to prevent direct air flow 
through the heater core, while the bypass passages around the heater core 
are opened. However, the front face of the heater core instead is exposed 
straight on to the forced air flow. The only way to prevent the air 
directly impacting the heater core front face from being substantially 
heated would be to shut the heater core off with a separate coolant flow 
shut off valve. 
SUMMARY OF THE INVENTION 
The invention provides a film type temperature valve that has the 
capability, with a single flexible belt, to completely cover and block 
both faces of the heater core, when the full cold mode desired, as well as 
to directly block the bypass passage and completely open both faces of the 
heater core when the full hot mode is desired. In addition, at 
intermediate temperature positions, the belt progressively uncovers the 
heater core faces while blocking the bypass passage, and vice versa, in 
inverse proportion, so as to precisely control air flow through the heater 
core and thereby control the air temperature. 
In the preferred embodiment disclosed, an evaporator core and heater core 
are contained within a hollow housing in a typical configuration, with the 
evaporator core filling the entire cross section of the housing. The 
heater core occupies less area, leaving a bypass passage around the side. 
A flexible belt extends across the bypass passage and wraps closely around 
both faces of the heater core, running between a pair of rollers that 
allow it to be extended and retracted. The belt contains a plurality of 
open windows separated by solid intervals that are sized and oriented 
relative to the bypass passage and the heater core faces so as to allow 
them to be selectively opened and closed as the belt extends and retracts. 
Specifically, in a first limit position of the belt, a so called full cold 
mode, both faces of the heater core are completely closed and blocked off 
by solid intervals of the belt, while the bypass passage is registered 
with a belt window, and fully open. Therefore, no forced air will flow 
either directly through the heater core, from face to face, or indirectly 
across either heater core face. At the same time, however, forced air can 
flow without restriction through the bypass passage. In a second limit 
position of the belt, a so called full hot position, the converse is true. 
That is, the bypass passage is totally blocked by a belt solid interval, 
and both heater core faces are registered with a belt window and 
completely open to direct flow through of forced air. At any intermediate 
belt position between the two belt limit positions, the bypass passage is 
progressively opened, and the heater core faces progressively closed off, 
or vice versa, in inverse proportion. This allows the air temperature to 
be closely and precisely controlled. 
Additional features of the preferred embodiment disclosed include a heater 
core module internal to the housing. The module provides both a 
substantially rigid case for the heater core, and a partition that crosses 
the bypass passage. Two openings in the heater core case provide for air 
flow through the heater core, while another opening in the partition 
provides for bypass air flow. The belt is conveniently mounted to rollers 
on the module, and slides around and on the rigid portions of the back and 
front of the heater core case as the belt extends and retracts.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring first to FIG. 1, a typical automotive heating and air 
conditioning assembly includes a hollow, rigid, molded plastic housing, 
indicated generally at 10, which is generally formed of two or more main 
sections that are screwed or snapped together. Upstream of the housing 10, 
a standard, non illustrated blower pulls air in and forces it downstream 
through housing 10. At the most downstream end of housing 10, within the 
vehicle interior, are a plurality (generally three) of air outlets, 
including a windshield defrost 12, mid level outlet 14, and lower or foot 
outlet 16. The air pulled in by the blower is selected by a suitable 
control valve, to be fresh, recirculated, or a combination of the two. 
Generally, recirculated interior air is chosen when a rapid heating or 
cooling is required. Likewise, the air outlet through which forced air 
exits to the interior is independently selected by any conventional 
control. What is most relevant to the subject invention is the control 
means by which the air pulled in to the system is tempered before it exits 
to the interior. Besides serving as a hollow plenum for the direction of 
forced air, several components are mounted within or on the housing 10. 
The most important of these to the subject invention are a conventional 
evaporator core 18, and a conventional heater core, indicated generally at 
20. Evaporator core 18 is large enough in area to fill and otherwise block 
substantially the entire cross sectional or internal area of housing 10, 
so that all forced air entering will be forced to pass through it. Since 
evaporator core 18 can be deliberately turned on and off along with the 
compressor of the basic air conditioning system, its constant presence in 
the forced air flow presents no problem, apart from an inevitable slight 
pressure drop. Evaporator core 18 can even be activated in winter, to dry 
the air before it is heated by heater core 20. Located downstream of 
evaporator core 18, the standard heater core 20 is smaller in size, with 
an upstream face 22 generally opposed to the evaporator core 18, and a 
downstream face 24 generally opposed to the air outlets 12-16. Given its 
smaller area, heater core 20 leaves a bypass passage around the top (top 
from the perspective of FIG. 1), indicated at 26. Unlike evaporator core 
18, heater core 20 is always active, which is to say that diverted engine 
coolant constantly circulates through it, even in summer. This, too, 
presents no problem, since the temperature control of the invention allows 
the effect of heater core 20 on the forced air to be essentially 
completely controlled. The temperature control valve that allows this more 
precise control of the effect of heater core 20 is described next. 
Referring next to FIGS. 2 and 3, a heater core module, indicated generally 
at 28, is designed to both contain heater core 20, as well as to control 
air flow through it cooperation with a flexible belt, indicated generally 
at 30. Module 28 is a rigid plastic molding, which slide fits within 
housing 10 before housing 10 is closed. Module 28 has two basic sections, 
including a case 32 that holds heater core 20, and a partition wall 34 
that bridges the bypass passage 26. Case 32 case has a pair of opposed 
openings, an upstream opening 36 facing the evaporator core 18, and a 
downstream opening 38 facing the air outlets 12-16, but is solid and 
uninterrupted otherwise. The case openings 36 and 38 are large enough to 
expose a substantial percentage of the area of the heater core faces 22 
and 24 to air flow, but need not be large enough to expose all of the area 
of the heater core faces 22 and 24. Partition wall 34 has an opening 40 
that takes up most of its width, so to open up most of the bypass passage 
26 when it is unblocked. Belt 30 is formed of any suitably flexible and 
durable material (with limited stretch), such as Kevlar.RTM., and has a 
pair of windows, an upper window 42 and lower window 44 separated by solid 
intervals of the belt 30. The end edges of belt 30 run from an upper 
roller 46 mounted above wall opening 40 to a lower roller 48 mounted above 
downstream heater case opening 38, so that belt 30 runs across wall 
opening 40 and closely around both side of case 32 and closely over both 
case openings 36 and 38. "Upper" and "lower," of course, imply only the 
reference frame of the Figures, and do not require such a vehicle 
orientation. The entire module 28, with core 20 and belt 30, can be 
assembled as shown in FIG. 2 and then conveniently installed into the 
larger housing 10. Heater core 20, of course, would thereafter be 
connected to inlet and outlet lines for engine coolant, which flow through 
it at all times that the engine is running. Belt 30 is configured, 
relative to the heater core module 28, so as to operate in a fashion 
described next. 
Referring next to FIGS. 3 and 4, belt 30 is pulled back and forth around 
case 32 as at least one roller 46 or 48 is actively wound back and forth 
to take up and pay out one edge of belt 30. The other roller 48 or 46 may 
be simply spring biased to act as a take up roller for the other edge of 
belt 30, or it may be active as well, and coordinated so as to move in 
concert with the other active roller. The details of the electric motor(s) 
or other power source that would actually wind either roller 46 and 48, 
and the sensor(s) and control system that would determine the position of 
belt 30 at any point and feed that information back to the rollers 46 and 
48 are not part of the subject invention. Such motors, sensors and control 
systems are known to those skilled in the art. The subject invention 
relates instead to the relationship of the various openings in the module 
28 and belt 30 and how they can be coordinated, in response to 
pre-determined temperature selections made by an operator within the 
vehicle, so as to efficiently control the flow and temperature of the 
forced air within housing 10. More specifically, as shown in FIG. 4, the 
operator may select a so called "full cold" or maximum cooling mode, 
through the operation of conventional instrument panel controls. Although 
not separately illustrated, selecting for most rapid cooling would cause 
the air conditioning system controls to activate the compressor and 
evaporator core 18, and would also generally switch the air intake valve 
to re-circulated air. The forced air drawn into housing 10 downstream 
would all pass through the cold evaporator core 18, and be cooled. The 
ultimate downstream air outlet, which would be independently selected, 
would most likely be either outlet 14 or 16. The purpose of the invention 
is to assure that the forced air cooled by the evaporator core 18 is not 
thereafter reheated by the heater core 20, which would be counter 
productive. To that end, as seen in FIG. 4, the belt control system would, 
when the vehicle occupant selected maximum cooling mode would, wind the 
belt 30 up or down as necessary until it was sensed that the upper belt 
window 42 was fully aligned or registered with the wall opening 40. The 
bypass passage 26 for air around heater core 20 is thereby fully opened. 
At the same time, the relation of the total length of belt 30 to the 
circumference of case 32 and the relative location of the case openings 36 
and 38 assures that solid intervals of the belt 30 closely overlay the 
case openings 36 and 38, while the lower belt window 44 concurrently 
overlies a solid portion of the case 32, between the case openings 36 and 
38. Consequently, both heater core faces 22 and 24 are completely and 
closely covered and shut off from either direct or indirect air flow, and 
the forced air cooled by evaporator core 18 is not reheated before it 
reaches the selected air outlet 12-16. 
Referring next to FIG. 5, the other "extreme" air tempering mode is so 
called full hot or maximum heating mode, where the converse air flow path 
is chosen. When the operator chooses maximum heating, evaporator core 18 
would be deactivated by the control system, and, just as in full cold 
mode, recirculated air would likely be chosen, so as to speed the 
temperature change. Belt 30 is moved to a position where sensors indicate 
that a solid belt interval overlays the partition opening 40, while the 
belt openings 42 and 44 are fully aligned or registered with respective 
case openings 36 and 38. The bypass passage 26 is fully blocked, and the 
heater core faces 22 and 24 are fully exposed to forced air flow. All 
forced air passing through the deactivated evaporator core 18 is forced 
directly through the fully opened and always activated heater core 20, and 
ultimately out the independently selected air outlet 12-16. It should be 
kept in mind, however, that the belt position shown in FIG. 5 simply 
assures that the air coming through evaporator core 18 passes all through 
heater core 20, and none through the bypass passage 26. However, that 
position of belt 30, per se, does not necessarily require that evaporator 
core 18 be deactivated, although it normally would be, in winter. Even in 
winter, however, the evaporator core 18 might be turned on to dry out the 
forced air, through condensation, in which case it would be desired to 
reheat it by directing it through the heater core 20 before it reached 
outlet 12 and the windshield. And, most likely, it would be desired to 
reheat the air to the maximum extent, as the belt position shown in FIG. 5 
would do. Nevertheless, belt positions between the two extremes of FIGS. 4 
and 5 can be selected, so as to heat (or reheat) the air that has passed 
through the evaporator core 18 to a lesser extent, regardless of whether 
evaporator core 18 is active. This is described next. 
Referring next to FIG. 6, an intermediate mode between the two extremes 
could be selected by the vehicle occupant when it was desired to level off 
a previously selected rapid cooling or heating process, or to simply 
choose a less extreme air temperature in the first instance. For example, 
in winter, when the evaporator core 18 is normally deactivated, it might 
not be desired to heat the air as hot as the heater core 20 is capable 
when fully open. Conversely, in summer, an air temperature might be 
desired that was higher than what the fully active and always fully open 
evaporator core 18 would produce by itself. In any case, when a moderated 
or intermediate air temperature was desired, the operator would simply 
move a typical mechanical temperature control between the extreme cold and 
hot positions, as desired, or choose a specific desired interior 
temperature on a conventional electronic digital display. This would, in 
turn cause the rollers 46 and 48 to wind the belt 30 to any of an almost 
infinite number of intermediate positions, a possible one of which is 
shown in FIG. 6. In general, in any intermediate position, some of the 
forced air that has flowed already through the evaporator core 18, active 
or not, flows through the partition opening 40, without passing through 
the heater core 20, and some portion flows through the always active 
heater core 20, to be heated. 
Referring next to FIGS. 4 and 6, and comparing them, the situation where it 
is desired to level off a rapid cooling process can be understood. From 
the rapid cooling position of FIG. 4, belt 30 is wound counterclockwise 
around case 32 to pull upper belt window 42 down by a certain increment 
(be it a half inch, one inch, or any given distance) and out of 
registration with partition opening 40 in substantially inverse proportion 
to the degree to which, concurrently, upper belt window 42 moves partially 
into registration with upstream case opening 36 and lower belt window 44 
moves simultaneously off of a solid interval of case 32 and into partial 
registration with downstream case opening 38. Stated differently, the flow 
around heater core 20 is decreased by the same belt motion that increases 
the flow through the heater core 20. The greater the increment by which 
bypass passage 26 is closed off, the greater the increment by which the 
heater core faces 22 and 24 are concurrently opened up, and vice versa. 
Consequently, the cold air coming off of evaporator core 18 has a net 
re-heat that is a function of how much bypasses the heater core 20, and 
how much passes through heater core 20. And this net flow can be carefully 
and precisely controlled by the motion of belt 30 back and forth, onto and 
off of the rollers 46 and 48, across the partition 34 and around the case 
32. It should be kept in mind that the FIG. 6 position of belt 30, also 
with an active evaporator core 18, could come into play even in winter, 
for defrosting the windshield. However, it is more likely that the FIG. 5 
position of belt 30 would be preferred for defrost, since it would likely 
be desired to reheat the air coming off of evaporator core 18 to the 
maximum extent possible. 
Referring next to FIGS. 5 and 6, and comparing them, a situation where it 
is desired to level off a rapid heating process can be understood. 
Evaporator core 18 would be off. From the belt position of FIG. 5, the 
rollers 46 and 48 wind the belt 30 clockwise, thereby moving the upper 
belt window 42 up and out of complete registration with upstream case 
opening 36 while simultaneously moving lower belt window 44 down and out 
of complete registration with downstream case opening 38, to the same 
degree. Concurrently, the partition opening 40 is opened up by upper belt 
window 42 moving upwardly and away from upstream case opening 36. The 
partition opening 40 is opened up to a degree inverse to the degree that 
the case openings 36 and 38 are blocked off. Therefore, less air will flow 
through the heater core 20, and proportionately more will flow through the 
bypass passage 26. Again, any other intermediate belt position similar to 
that shown that in FIG. 6, but with the three openings 36, 38 and 40 
opened and closed to different degrees, could be achieved. It should also 
be kept in mind that any such intermediate belt position might be selected 
initially, and not just as a pull back from one of the belt limit 
positions of FIGS. 4 or 5. 
Variations in the preferred embodiment could be made. The bypass passage 26 
could be located on the other side (or "bottom") of the heater core 20, or 
the heater core 20 could be placed more or less in the center of housing 
10, leaving a smaller bypass passage to either side. The module 28 could 
theoretically be eliminated as a separate part, and separate rollers 
mounted directly to the housing 10 could be used to run the belt 30 over 
the same path, directly across the bypass passage 26 and directly wrapped 
around the heater core 20. The belt windows 42 and 44 would likely have to 
be sized differently, however, because the lack of a case like 32 
surrounding the heater core 20 would preclude the ability, as shown in 
FIG. 4, to have the lower belt window 44 "parked" over a solid part of the 
case 32 and, therefore, not creating an opening through the core 20. 
Furthermore, having the separately assembled unit of module 28, core 20 
and belt 30 that can be slid at once inside of housing 10 is a 
convenience, and allowing the belt 30 to slide over the outer surface of 
case 32 helps to support the smooth motion of the belt 30 and eliminates 
the needs for some other guide surfaces or rollers. It is also convenient 
to be able to fix the rollers 46 and 48 to the module 28, although they, 
too, could be mounted directly within the housing 10 itself. Therefore, it 
will be understood that it is not intended to limit the invention to just 
the preferred embodiment disclosed.