Abstract:
A vehicle heating, air conditioning and ventilation system comprises a housing ( 10 ) within which an evaporator ( 12 ) and heater ( 14 ) are arranged generally in a diverging V shape enclosing a mixing space (M) between. All forced air passes through the evaporator ( 12 ) first, after which it is can go straight through to the mixing space (M), or be diverted down under the heater ( 14 ) to flow through the heater ( 14 ) and into the mixing space (M), or some combination of the two. The combination of cold and hot flows into the mixing space (M) is determined by a solid dividing wall ( 30 ), which partially blocks the evaporator ( 12 ) and heater ( 14 ) from one another, and a pair of separate rolling film belts ( 32, 34 ), one between the evaporator ( 12 ) and the dividing wall upstream side ( 36 ) and the other located between the dividing wall downstream side ( 38 ) and the heater ( 14 ). Each belt ( 32, 34 ) has respective windows ( 48, 56 ) and solid areas ( 50, 58 ) which can be shifted to selectively block or unblock flow into the mixing space (M). The two belts ( 32, 34 ) in conjunction with the solid dividing wall ( 30 ), prevent any air that has passed through the evaporator ( 12 ) from by passing the heater ( 14 ). In addition, the individuality of the two belts ( 32, 34 ) allows a wide combination of temperatures and air flows to be achieved, and also allows the respective windows ( 48, 56 ) to be staggered to promote mixing.

Description:
TECHNICAL FIELD 
     This invention relates to air conditioning systems in general, and specifically to dual film belt temperature control system with improved temperature and air flow control. 
     BACKGROUND OF THE INVENTION 
     Vehicle air conditioning systems (broadly defined to include both heating and cooling the air) are often referred to by the shorthand acronym of “HVAC” system. The heart of such a system is a box shaped housing containing an evaporator and heater, which are spaced apart, with inner faces that face one another and outer faces that face away from one another. Fan forced air flow is selectively directed through the two heat exchangers, cold and hot, to attain a final, mixed air stream of a desired temperature and flow rate. In essentially all commercially available systems, the evaporator is located upstream of the heater, and is the physically larger of the two heat exchangers, so that all of the forced air stream passes through it initially. However, the evaporator can be deliberately turned off, so the fact that all air passes through it all the time does not jeopardize the ability to control final temperature. The heater, however, typically operates all the time, so that the system must be able to route or block air selectively through the heater, in order to achieve a desired final, mixed temperature. Older mechanisms for blocking or unblocking the air flow through the heater used a swinging flapper door located in the space between the evaporator and heater, which would admit more or less air through the heater depending on its angular position. The final temperature, mixed air stream would finishes downstream of the beater. Such systems obviously require enough space between the evaporator and heater for the door to swing, limiting how compact the entire system can be made. In addition, swinging door systems tend to lack linearity. That is, they tend to be all on, or all off, but are far less adept at attaining. mid range settings. 
     More recent designs, attempting to attain both improved packaging and better linearity, have incorporated a rolling film belt to selectively block or unblock air flow through the heater. An example may be seen in U.S. Pat. No. 5,653,630. The design disclosed there uses a single belt (temperature belt) wrapping around the entire inner face of the heater, and which also extends up beyond the heater inner face and partially over, but only partially over, the inner face of the evaporator. The portion of the inner face of  10  the larger evaporator not covered by the single film temperature belt is selectively blocked or unblocked by a swinging door of conventional design. Air that has passed the evaporator is let through, or by passed around, the heater by a combined action of the moving belt and the swinging door, to mix together downstream of the heater. An entirely separate belt (mode belt) moves independently to admit the mixed, final temperature air into the passenger compartment. 
     The single belt temperature control disclosed, and any single belt design, suffers from an inevitable shortcoming, however. A single belt, as it moves, inherently shifts solid areas to locations where open areas of the belt previously were, and vice versa. Open and blocked areas are not independently achievable, in other words, which means that not every desired combination of final temperature and air flow rate can achieved. A temperature change created by allowing more or less air through the heater core inevitably affects total final air flow rate, as well. The extra by pass door in the design disclosed in U.S. Pat. No. 5,653,630 noted above which needs its own actuator and swinging room which negates much of the advantage of using a film belt in the first instance. 
     SUMMARY OF THE INVENTION 
     A vehicle air conditioning system in accordance with the present invention is characterized by the features specified in claim  1 . 
     In the embodiment disclosed, a box shaped system housing contains a conventionally sized evaporator and heater, the evaporator being the larger of the two and located upstream of the heater. The evaporator and heater are preferably arranged in a V shape, with opposed inner faces diverging upwardly from opposed lower edges toward conventional vehicle interior air outlets, creating an air mixing space between the two heat exchangers and below the air outlets. An air flow diversion passage extends from the lower edge of the heater&#39;s inner face down and around to its outer face, so that forced air can be routed in a reverse flow through the heater and into the mixing space. Air flow into the diversion passage is assisted by a dividing wall that extends up from the heater lower edge and partially into the mixing space, blocking a portion of the inner faces of the evaporator and heater from one another. 
     The dividing wall cooperates with a pair of separate film belts to provide improved handling, sealing and mixing of the flow through the two heat exchangers. A first rolling film belt is located between the inner face of the evaporator and the upstream side of the dividing wall. The first film belt extends from a lower roller across the remainder of the inner face of the evaporator to an upper roller. A second rolling film belt is located between the inner face of the heater and the downstream side of the dividing wall. The second belt, oriented roughly in a V shape relative to the first, extends from a lower roller across the remainder of the inner face of the heater to an upper roller. Each belt contains a solid area as well as one or more elongated windows, which, in the embodiment disclosed, may be staggered relative to one another. 
     The two separate belts, with independently movable solid and open areas, provide the capability for better control of total air flow rate and final temperature mix than would a single belt wrapped around a single lower roller in a similar V shape. For example, each belt can be set to present the same basic degree of open area to the heat exchanger face that it covers, one fifth open each, one third open each, three quarters open each, etc, and thereby achieve the same basic mixed temperature, but with different total air flow rates. A single belt, wrapped around a common central idler roller into a similar V shape, would require basically an inverse relationship of open and blocked areas, (one fifth-four fifths, one third-two thirds, etc). This is because a single window would be shared across the two heat exchanger faces as the single belt moved. In the invention, mixing of the two air streams is also assisted by the staggered relationship of the two belts′ windows, which would also not be possible with a single belt. A single belt wrapping around a central, shared roller would also require a wiping belt seal to prevent air which had passed through the evaporator from leaking directly around the shared roller and in front of the heater, without passing through the heater. But a wiping seal, if forcefil enough to really be effective, would resist free belt movement. Such leakage in the invention is prevented by the fact that the lower heater belt is sheltered on the downstream side of the dividing wall, without the necessity for a belt to pass through an interface between the cold and hot side. The system also has the capability of completely closing off both heat exchanger faces, thereby eliminating the need for a separate external valve door to block off ram air flow through the ventilation system at high vehicle speeds. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other features of the invention will appear from the following written description, and from the drawings, in which: 
     FIG. 1 is a sectional side view of a vehicle HVAC housing incorporating a preferred embodiment of the invention; 
     FIG. 2 is a partially broken away flat view of the evaporator belt; 
     FIG. 3 is a partially broken away flat view of the heater belt; 
     FIG. 4 is a perspective view of the two belts alone moved to a mid temperature setting, at a low total flow rate; 
     FIG. 5 is a view similar to FIG. 4, showing the belts at the same mid temperature setting, but with a higher total flow rate; 
     FIG. 6 is a view similar to FIG. 5, showing the belts again at the same mid temperature setting, but at an even higher total flow rate; 
     FIG. 7 is a view similar to FIG. 4, but showing both belts rolled to a solid position, blocking all air flow; 
     FIG. 8 is a view similar to FIG. 7, but showing only the vaporator belt open, and only to a small degree; 
     FIG. 9 is a view similar to FIG. 8, but showing only the eater belt open, to a moderate degree. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring first to FIG. 1, an HVAC housing, indicated generally at  10 , is a typical, hollow, molded plastic box, more compact than many conventional units, but no untypical in general shape and material. Outside air (or recirculated air, or a combination of the two) is pressurized by a conventional, non illustrated centrifugal blower and forced through housing  10 , generally in the direction shown by the arrows, which is covered in more detail below. Ultimately, air exits a selected outlet into a passenger space indicated generally at P (one of three outlets, typically, defrost D, air conditioning A/C, and/or heater H). Before reaching its ultimate destination, however, the air is either cooled, or heated, or, often, both, as determined by a pair of heat exchangers and an air routing structure described in detail below. 
     Still referring to FIG. 1, housing  10  includes a conventionally sized evaporator, indicated generally at  12 , and heater, indicated generally at  14 . Both heat exchangers are generally box shaped as well, evaporator  12  having flat outer and inner faces  16  and  18  respectively, and heater  14  having flat outer and inner faces  20  and  22  respectively. The two are arranged in a general V shape within housing  10 , with the respective inner faces  18  and  22  facing each other to define what may be referred to as a mixing space M between. Evaporator  12  and heater  14  could be arranged in any relative location that created a mixing space in between the inner faces  18  and  22 . Heater  14  is mounted securely within a open mesh frame  24  within housing  10 , and a lowermost edge  26  thereof, as well as outer face  20 , sit slightly above an upwardly slanted lowermost wall  28  of housing  10 . Wall  28  defines what may be terned an air diversion passage extending from the heater lower edge  26  up and under the heater outer face  20 . Evaporator  12  is considerably larger than heater  14 , enough so to span the entire inner area of housing  10 . Consequently, all forced air passes first through evaporator  12 , upstream of heater  14 . Evaporator  12 , may, of course, be activated or not. The air passing evaporator  12 , cooled or not, is then routed through the always hot heater  14 , or not, to a degree determined by other structure described in detail next. 
     Referring next to FIGS. 1 and 2, the selective routing of air through evaporator  12  and heater  14  is achieved by a central dividing wall  30 , and a pair of rolling film belts, a first belt, indicated generally at  32 , and second rolling film belt, indicated generally at  34 . Dividing wall  30  is, preferably, but not necessarily, a molded plastic piece, and extends with a basic sinuous shape from the heater lower edge  26  up between the heat exchanger opposed inner faces  18  and  22 , partially covering both of them. That is, the upstream side  36  of wall  30  faces and covers part of evaporator inner face  18 , but by no means all of it, as the downstream side  38  of faces and covers part of heater inner face  22 . Above wall  30 , a first upper flange  40 , in conjunction with wall  30 , creates an opening from evaporator inner face  18  into the mixing space M. Likewise, above wall  30 , a second upper flange  42 , in conjunction with wall  30 , creates an opening from heater inner face  22  into mixing space M. First belt  32  rolls back and forth from a lower roller  44  onto, or off of, an upper roller  46  in a run that is located between the evaporator inner face  18  and the dividing wall  30 , close to and in abutment with the upstream side  36  thereof. The lower roller  44  is sheltered beneath a bend in the central wall  30 , and it is the logical roller to be “live” or powered, by a conventional motor or other actuator, so as to actually wind up or wind out the belt  32 . The upper roller  46  sits behind the upper flange  40 , and is the more logical roller to be a passive, take up roller, with a take up spring or other bias means to maintain a tension in the belt  32 . That roller function could be reversed, of course, or each roller could be actively powered and synchronized with the other to maintain belt tension, but that would be a costly option. First belt  32  is cut with a pair of elongated windows  48  at the bottom, and an equally long solid area  50  at the top. As first belt  32  is rolled back and forth, the windows  48  either register with the opening into the mixing space M, or are wound up completely onto lower roller  44  to leave the opening into the mixing space M completely blocked, or some combination thereof. Air passing through evaporator inner face  18  either enters the mixing space M, or is diverted down along lower housing wall  28 , accordingly. The force of air hitting the inside of belt  32  will press it against the dividing wall upstream side  36 , providing a seal of sorts, but that seal need not be rigorous. This is because any air that passes through the mid- upper or center area of evaporator inner face  18 , and which does not go directly into mixing space M, will impinge on the dividing wall upstream side  36  and be forced down below heater outer face  20 . (So, too, for air that passes through the lower part of evaporator inner face  18 ) Air impinging on the solid dividing wall upstream side  36  will not be able to by pass the heater  14  to leak instead directly in front of the heater inner face  22 . Such by pass leakage would prevent the final temperature within the mixing space M from being as hot as it would otherwise be. Such by pass leakage prevention would not be possible if the otherwise solid dividing wall  30  were interrupted by a slot through it that would allow a single, continuous belt to pass through it and in front of heater inner face  22 . 
     Such a slot would have to be covered by a seal wiping on the surface of such a single, continuous belt, which would greatly retard belt motion. 
     Referring next to FIGS. 1 and 3, the second, separate belt  34  is of similar material and general configuration to belt  32 , winding back and forth between a lower roller  52  and an upper roller  54  in a run that is located between the heater inner face  22  and the dividing wall  30 , close to and in abutment with the downstream side  38  thereof. The lower roller  52  is also sheltered beneath a bend in the central dividing wall  30 , and is also the logical roller to be powered. This also creates the ability to power the two lower rollers  44  and  52 , which are near one another, concurrently and with a single geared actuator, as described in more detail below. The upper roller  54  sits beneath the upper flange  42 , and is also the more logical roller to be a passive, take up roller. Second belt  34  is cut with three, narrower elongated windows  56  at the bottom, and an equally long solid area  58  at the top. As second belt  34  is rolled back and forth, the windows  56  either register with the opening into the mixing space M, or are wound up completely onto lower roller  52  to leave the opening into the mixing space M completely blocked, or some combination thereof. Air flowing up from above wall  28  and through heater  14  forces belt  34  against the dividing wall downstream side  38  and exits the windows  56 . The air tempered by flowing through heater  14  is also blocked from flowing back in front of the evaporator inner face  18  by the solid dividing wall  30 . 
     Referring next to FIG. 4, one of the temperature and air flow combinations possible is illustrated. Central dividing wall is partially broken away to give a better view of the belts  32  and  34 , as are the upper flanges  40  and  42 . Both belts  32  and  34  are moved so as to put small, and roughly equal lengths of their respective windows  48  and  56  in registration with the respective heat exchanger inner faces  18  and  22 . Most of the potential air flow area is blocked by the belt solid areas  50  and  58 , but the air streams that are allowed through are enough to create a total air flow into the mixing space M of approximately 50 cubic feet per minute, and at a final, mixed temperature of approximately 65 degrees F. Mixing of the hot and cold air streams to a final temperature is assisted by the staggered relationship of the windows  48  and  56 , which creates a swirling action. From the mixing area M, of course, tempered air can be admitted to the passenger P through any or all of the outlets D, A/C or H, as determined by any suitable valve or belt type mode control device, such as a mode belt indicated generally at the dotted line  60 . Were the two belts  32  and  34  not in fact separate, but, instead, two legs of a single belt wrapped around a single, common idler roller at the bottom of the V, this combination of temperature and air flow would not be possible. With such a single belt, the belt windows would be forced into an inverse relationship across the two legs of the V, for example, ⅓ on one side, and ⅔ on the other. Moreover, an unslotted, solid dividing wall like  30  would not be available, or even possible, to prevent air that had passed through evaporator  12  from leaking over and in front of heater inner face  22 , instead of being forced through heater  14 . That kind of by pass leakage would interfere with attaining the kind of mid range final temperature that equal belt openings could otherwise attain. 
     Referring next to FIG. 5, another possible air flow and temperature combination is illustrated. Here, more total length and area of the espective belt windows  48  and  56  has been rolled into an open position, but till in roughly equal proportion. Again, this is not a combination of open areas, or even a total open area, that would be possible with a single belt. Now, total air flow into the mixing space M is greater, approximately 100 cubic feet per minute, the final temperature, determined by the by the substantial equality of open areas, is still 65 degrees F. 
     Referring next to FIG. 6, yet another possible air flow and temperature combination is illustrated. Now, essentially all of the total length and area of the respective belt windows  48  and  56  has been rolled into an open position, and still in roughly equal proportion. As before, neither this combination of open areas, nor certainly not this large a total open area, would be possible with a single belt that was forced to share a single window across two adjacent runs of the single belt. Here, the total air flow rate can be very high, approximately, 200 cubic feet per minute, while the temperature remains at around 65 degrees F. The invention can do a great deal more than simply maintain a given temperature over a range of air flow rates, as will be described next. 
     Referring next to FIG. 7, the two belts  32  and  34  are shown rolled down onto the respective lower rollers  44  and  52  to the point where only respective belt solid areas  50  and  58  are exposed. Consequently, air passing through both the evaporator  12  and heater  14  will be blocked from entering the mixing area M, or from reaching any of the outlets D, A/C or H. This belt position provides a great advantage when the vehicle is moving at high speed, in that it prevents ram air from being forced into the passenger space P, without the need for a separate, external shut off valve upstream of the heat exchangers  12  and  14 . Air forcibly impinging on the belts  32  and  34  simply pushes the respective belt solid areas  50  and  58  more strongly into the dividing wall&#39;s upstream and downstream sides  36  and  38 , assisting in the sealing action, and eventually creating a pressure dead head that prevents outside air from ramming into the housing  10 . Elimination of a ram air control valve represents a considerable potential saving. 
     Referring next to FIGS. 8 and 9, two other of many possible belt positions are illustrated. Evaporator belt  32  is moved to expose only a small area of its windows  48 , while the heater belt  34  completely blocks heater  14 . This would allow a very low flow rate of air that was not tempered by the heater  14 , be it ambient temperature air, or air that has been cooled by an active evaporator  12 . FIG. 9 shows essentially the converse. The evaporator  12  is completely blocked by belt  32 , while the windows  56  of heater belt  34  are open to a moderate degree. This would provide air warmer than that resulting from the positions illustrated in FIGS. 4-6 above, but at a much lower total flow rate. With totally independently powered and individually movable belts  32  and  34 , an essentially limitless possible combinations of temperature and flow rate could be achieved. 
     Variations in the disclosed embodiment could be made. For example, while still keeping the two belts  32  and  34  individual and separate, they could be moved in tandem by a single actuator geared to each lower roller  44  and  52 . Although doing so would eliminate many possible combinations of belt openings, many would still be possible. For example, all of the positions shown in FIGS. 4 through 7 would still be possible, while saving the expense of a second actuator. The belt windows  48  and  56  need not be staggered, as shown, although doing so is cost free and promotes a swirling and mixing action that would not be possible with a single belt. Or, the windows  48  and  56  could be shaped very differently, for example, slanted in opposing directions, so as to promote air mixing even more vigorously. Again, differing shapes, locations, and sizes of belt windows would not be possible with a single belt. The separate belts  32  and  34  could instead be arranged as multiple separate, adjacent pairs (or threes, or fours) of belts facing each heat exchanger  12  and  14 , with zone walls dividing the mixing space M into an equivalent number of separate temperature zones, one zone for each pair of belts. One wall would create two zones, two would yield three, and so on. Then, the pair of belts located in each zone (regardless of the number of zones) could be moved just as the single pair of belts in the single zone were described as moving above. This presumes, of course, a suitable means to actuate the adjacent multiple pairs of belts. But, because the pair of belts in each zone would be separate, each zone could have its own temperature controlled as described above. And, because of the fact that the cold and hot air are routed into the mixing zone M as described above, with the cooperation of the solid dividing wall  30  and the diversion passage below the heater  14 , it would only be necessary that the zone walls engage the inner surfaces of the belt pairs to create good temperature division, with no so called “cross talk” between individual zones. The zone walls would not, as in a conventional zoned system, have to extend all the way in to the faces of the heat exchangers to create a good zone division.