HVAC system having linkage rod with mid-point movement control

The present teachings provide for a vehicle heating, ventilation, and air conditioning (“HVAC”) assembly including a drive member, a driven member, a connecting member, a guide member, a first door, and a second door. The connecting member can be rotatably coupled to the drive member and the driven member and can be configured to be moved by the drive member to rotate the driven member. The guide member can be in cooperation with the connecting member and configured to restrict movement of the connecting member as the connecting member is moved by the drive member. The first door can be configured to be rotated by the drive member between a first position and a second position. The second door can be configured to be rotated by the driven member between a third position and a fourth position.

FIELD

The present disclosure relates to a vehicle heating, ventilation, and air conditioning (“HVAC”) system having a linkage rod with mid-point movement control.

BACKGROUND

Vehicles are known to include a heating, ventilation, and air conditioning (“HVAC”) system to improve the comfort of the people within the passenger compartment of the vehicle. The HVAC system can heat and cool air blown through the HVAC system using a heating heat exchanger and/or a cooling heat exchanger. The heating heat exchanger, or heater core typically utilizes the engine coolant as a source of heat for heating the air. The cooling heat exchanger is typically an evaporator which is part of an air conditioning system in the vehicle.

Vehicle HVAC systems typically have internal passages, or ducts for routing air through various components of the system, such as the evaporator, or the heater core for example, before the air is expelled into the passenger compartment. These ducts can also route the air to different locations in the vehicle, such as to be directed toward the left, right, front, or rear of the vehicle for example.

Generally, HVAC systems can include doors, or gates within these ducts, that can be moved between opened and closed positions to selectively control airflow through the individual ducts. The position of these doors can be generally controlled by devices, such as servo motors, or linear actuators. It can be desirable to selectively control the operation of more than one of these doors simultaneously, to allow more than one duct to open, or close simultaneously.

For example, in a system with a first duct that directs airflow to a first zone of the passenger compartment, and a second duct that directs airflow to a second zone of the passenger compartment, it can be desirable to use a single motor to simultaneously control individual doors within the two ducts to selectively block airflow through the two ducts. It can be desirable to operate the two doors such that they both open the same amount to allow the same amount of air to flow to both zones. By way of another example, a first duct may direct cool air toward the passenger compartment, while a second duct directs air through the heat exchanger before directing it toward the passenger compartment. In such a system, the temperature of the air directed toward the passenger compartment can depend on the relative amounts of air directed through the first and second ducts. It can be desirable to use a single motor to simultaneously control individual doors within the two ducts to selectively regulate airflow through each duct.

Current mechanisms for actuating multiple doors from a single motor generally include a linkage rod for coupling the operation of the two doors to the single motor. These linkage rods, are typically formed of a thermoplastic material to minimize weight and cost of the components. It has been found that the linkage rod can bend or flex during operation, which can lead to incomplete sealing of the doors, or undesirable differences in the door positions. Such bending can become more pronounced when the linkage rod becomes heated, such as due to the vehicle sitting in the sun on a hot day for example. Accordingly, there exists a need for a device that reliably and accurately articulates multiple HVAC duct doors with a single motor.

SUMMARY

The present teachings provide for a vehicle heating, ventilation, and air conditioning (“HVAC”) assembly including a drive member, a driven member, a connecting member, a guide member, a first door, and a second door. The connecting member can be rotatably coupled to the drive member and the driven member and can be configured to be moved by the drive member to rotate the driven member. The guide member can be in cooperation with the connecting member and configured to restrict movement of the connecting member as the connecting member is moved by the drive member. The first door can be configured to be rotated by the drive member between a first position and a second position. The second door can be configured to be rotated by the driven member between a third position and a fourth position.

The present teachings also provide for a vehicle heating, ventilation, and air conditioning (“HVAC”) assembly including a drive member, a driven member, a connecting member, a guide member, a first flue set, a second flue set, a first door, and a second door. The connecting member can be rotatably coupled to the drive member and the driven member and can be configured to be moved by the drive member to rotate the driven member. The guide member can be in cooperation with the connecting member and configured to restrict movement of the connecting member as the connecting member is moved by the drive member. The first door can be configured to be rotated by the drive member between a first position and a second position. The second door can be configured to be rotated by the driven member between a third position and a fourth position. When the first door is in the first position and the second door is in the third position, air is permitted to flow through the first flue set and prevented from flowing through the second flue set. When the first door is in the second position and the second door is in the fourth position, air is prevented from flowing through the first flue set and permitted to flow through the second flue set.

The present teachings also provide for a vehicle heating, ventilation, and air conditioning (“HVAC”) assembly including a heater exchanger, an evaporator, a housing, a flue door mechanism, a guide member, and a channel. The housing can define a first flue set and a second flue set. The first flue set can be configured to direct air received from the evaporator through the heat exchanger. The second flue set can be configured to direct air received from the evaporator to bypass the heat exchanger. The flue door mechanism can include a drive member, a driven member, a connecting rod, a first door, and a second door. The drive member can be rotatably coupled to the housing. The driven member can be rotatably coupled to the housing at a location spaced apart from the drive member. The connecting rod can have a first end rotatably coupled to the drive member, a second end rotatably coupled to the driven member, and a mid-section extending between the first and second ends. The first door can be disposed within the housing and can be coupled for rotation with the drive member between a first position and a second position. The second door can be disposed within the housing and can be coupled for rotation with the driven member between a third position and a fourth position. The guide member can be coupled to one of the housing and the mid-section of the connecting rod. The channel can be defined by the other of the housing and the mid-section. The guide member can be received in the channel. The channel and the guide member can cooperate to restrict movement of the connecting rod to a path defined by the channel. When the first door is in the first position and the second door is in the third position, air is permitted to flow through the first flue set and prevented from flowing through the second flue set. When the first door is in the second position and the second door is in the fourth position, air is prevented from flowing through the first flue set and permitted to flow through the second flue set.

DETAILED DESCRIPTION

With reference toFIG. 1, a vehicle10is shown having a passenger compartment14, a heating, ventilation, and air conditioning (“HVAC”) system18, an engine compartment22, a firewall26, and a dashboard, or instrument panel30. The passenger compartment14is configured for vehicle occupants (not shown) to operate, ride in, or otherwise occupy the vehicle10. The passenger compartment14can generally be divided into a first zone34and a second zone38. In the example provided, the first zone34generally includes the front portion of the passenger compartment14, and the second zone38generally includes the rear portion of the passenger compartment14. However, it is understood that alternative, or additional divisions of the passenger compartment can be used, such as the left, or right portions for example. The engine compartment22can generally include an engine (not shown), an engine coolant system (not shown), and a compressor (not shown). The engine coolant system can typically include a radiator and water pump configured to circulate a coolant fluid through a plurality of conduits in the engine to remove heat from the engine for example. The firewall26can generally separate the passenger compartment14and instrument panel30from the engine compartment22. The instrument panel30can generally be between the passenger compartment14and the firewall26. The instrument panel30can generally house a plurality of instruments (not shown), such as dials, displays, or controls for operating, viewing, or accessing navigation, entertainment, communications, or vehicle operational information for example. While the vehicle10in the example provided is shown as a car, it is understood that the HVAC system18can be used in other vehicles, such as a truck, or an agricultural, or military vehicle for example.

The HVAC system18can include an HVAC main unit42, an intake duct46, a first zone duct50, a second zone duct54, and any suitable number of additional ducts (such as lower duct58). The main unit42can be located within the vehicle10, such as generally between the instrument panel30and the firewall26. The main unit42can generally be configured to supply air to anyone or more of the ducts50,54,58.

The main unit42can include a main housing62, a refrigerant supply line66, a heater supply line68, a refrigerant return line70, a heater return line72, and a blower housing74. The main housing62can define an intake port78, a first air port82, a second air port86, and can also define additional ports, such as a lower port90. The blower housing74can house a blower (not shown) configured to draw air from within the passenger compartment14, and/or from outside the vehicle10, through the intake duct46by way of the intake port78, and blow the air through the main housing62, as will be described below. The intake duct46can be configured to receive the air from the passenger compartment14and/or outside the vehicle10. The refrigerant supply line66and refrigerant return line70can be fluid conduits that extend through the firewall26into the engine compartment22. The refrigerant supply line66can supply refrigerant to the main unit42, from the compressor (not shown). The refrigerant return line70can allow the refrigerant to return from the main unit42, to the compressor. The main unit42will be described in greater detail below.

The first zone duct50can extend from the first air port82, to the first zone34of the passenger compartment14, and can be configured to supply air from the main unit42to the first zone34. The first zone duct50can be generally disposed within the instrument panel30, or between the instrument panel30and the firewall26, and can extend through the instrument panel30to expel air through one or more first vents94mounted in the instrument panel30. While the example shows the first vents94located in the instrument panel30, it is understood that the first vents94can alternatively, or additionally be located in other locations proximate to the first zone34, such as below the instrument panel30to provide air toward an occupant's feet for example.

The second zone duct54can extend from the second air port86, to the second zone38of the passenger compartment14, and can be configured to supply air from the main unit42to the second zone38. The second zone duct54can extend from the second air port86, to the second zone38to expel air through one or more second vents98proximate to the second zone38. In the example provided, the second zone duct54extends along the lower portion of the passenger compartment, such as through a center console (not shown) for example. However, it is understood that the second zone duct54can extend to the second zone38along other paths, such as through a headliner of the vehicle10for example.

With additional reference toFIGS. 2, 3A, and 3B, the main unit42is illustrated in greater detail. The main unit42can further include a cooling heat exchanger or evaporator102, a heating heat exchanger or heater core106, and a flue door mechanism110. The main housing62can define an air supply flue114, a hot air flue118, a cool air flue122, and a main flue126, each configured to convey air through the main housing62. The main housing62can also define a lower flue130.

The evaporator102can be any type of heat exchanger, such as a radiator for example. The evaporator102can be located within the main housing62and in line with the air supply flue114. The evaporator102can be coupled to the refrigerant supply line66and the refrigerant return line70and can have a series of tubes (not shown), configured for the refrigerant fluid to pass through while flowing from the refrigerant supply line66to the refrigerant return line70. The evaporator102is configured such that air flowing through the air supply flue114can flow across the tubes. The refrigerant fluid can generally absorb heat from the air as the air passes across the tubes of the evaporator102, to lower the temperature of the air and remove moisture from the air. The heated refrigerant fluid can then return to the compressor via the refrigerant return line70.

The heater core106can be any type of heat exchanger, such as a radiator for example. It is understood that the heater core106can alternatively, or additionally include an electrical heating element. The heater core106can be located within the main housing62and in line with the hot air flue118. The heater core106can be coupled to heater supply and return lines68,72, which can be configured to supply the heater core106with a heating fluid, such as engine coolant that has been heated by the engine for example. Similar to the refrigerant supply and return lines66,70, the heater supply and return lines68and72can pass through the firewall26and into the engine compartment22, where the heating fluid is heated by the engine. The heating fluid can pass through a series of tubes (not shown) within the heater core106, while flowing from the heater supply line to the heater return line. The heater core106is configured such that air flowing through the hot air flue118can flow across the tubes. The heating fluid can generally release heat to the air as it passes across the heater core106tubes.

The air supply flue114can be fluidly coupled with the blower housing74and intake port78to receive air therefrom. The hot air flue118can have an inlet134and an outlet138. The inlet134can be proximate to the air supply flue114, to receive air therefrom. The outlet138can be proximate to the main flue126, such that air can flow from the hot air flue118to the main flue126through the outlet138. The cool air flue122can be proximate to the air supply flue114and the main flue126, such that air can flow from the air supply flue114, through the cool air flue122, to the main flue126without flowing through the hot air flue118. The main flue126can be fluidly coupled to the first air port82and the second air port86to provide air to the first and second zones ducts50,54. The main flue126can also be fluidly coupled to the lower port90by the lower flue130. In this configuration, additional mechanisms142can be included to selectively provide air from the main flue126to one or more of the first air port82, the second air port86, and the lower port90. The lower port90can be coupled to the lower duct58, which can direct air to the lower portion of the first zone34.

With particular reference toFIG. 2, for example, the flue door mechanism110can include a drive link146, a driven link150, a connecting link154, and an actuator158. A first door162and a second door166of the flue door mechanism110are illustrated inFIGS. 3A and 3Bfor example. SinceFIGS. 3A and 3Billustrate a cross-sectional view of the main unit42, the actuator158, drive link146, connecting link154, and driven link150are illustrated in dashed lines to indicate their locations and general positions relative to the main unit42and the first and second doors162,166. The flue door mechanism110can also include a link cover170. The drive link146can have a first, or drive pivot174, and a second pivot178. The drive pivot174can be rotatably coupled to the main housing62. In the example shown, the drive pivot174is a pin non-rotatably coupled to the drive link146and rotatably received in an aperture182of the main housing62, though other configurations can be used. The second pivot178can be spaced radially apart from the drive pivot174and configured to rotate about the drive pivot174.

The driven link150can have a third, or driven pivot186, and a fourth pivot190. The driven pivot186can be spaced apart from the drive pivot174and rotatably coupled to the main housing62. In the example shown, the driven pivot186is a pin non-rotatably coupled to the driven link150and rotatably received in an aperture194of the main housing62, though other configurations can be used. The fourth pivot190can be spaced radially apart from the driven pivot186and configured to rotate about the driven pivot186.

The connecting link154can be formed of a thermoplastic material and can have a first end198, a second end202, and a central rod206extending between the first and second ends198,202. In the example provided, the connecting link154is a rigid, linear rod, though other configurations can be used. The central rod206can have a guide member or support member210and the main housing62can define a groove214. It is understood that the main housing62can include or can be constructed of a plurality of individual pieces and that the groove214can be defined by one of such pieces mounted to or integrally formed with the other(s) of such pieces. The groove214can have a generally arcuate path coinciding with the movement of the support member210, as will be discussed below.

The support member210can generally be located toward the middle of the central rod206, and can be integrally formed with the central rod206. The support member210can be received within the groove214and can slide along the groove214as the connecting link154is moved between positions, as will be discussed below. The groove214can be generally arcuate in shape to coincide with the path of the connecting link154and support member210. The drive link146can be rotatably coupled to the first end198of the connecting link154at the second pivot178, and the driven link150can be rotatably coupled to the second end202of the connecting link154at the fourth pivot190. In this way, the connecting link154couples the drive link146and driven link150as a four-bar linkage, such that rotation of the drive link146at the drive pivot174causes rotation of the driven link150at the driven pivot186. The degree of rotation of the driven link150relative to the drive link146depends on the relative lengths of the drive link146and driven link150. In the example provided, the relative lengths are generally similar, though other lengths can be used. The support member210and groove214cooperate to prevent the connecting link154from flexing, or bending perpendicular to the path of the groove214.

With reference toFIGS. 2 and 4, the link cover170can have a first flange218and a second flange222, a cap226and can define a link cavity230. The link cover170can be coupled to the main housing62at the first and second flanges218,222by any suitable means, such as a fastener (not shown), or adhesive for example. At least a portion of the central rod206can be received in the link cavity230between the cap226and the main housing62. The link cover170can cover at least the portion of the central rod206and main housing62such that the connecting link154can translate between the link cover170and the main housing62when the drive link146rotates. The cap226can prevent the central rod206from moving along axis234, thus preventing the connecting link154from bending away from the main housing62, and preventing the support member210from disengaging the groove214. In this way, the link cover170and main housing62prevents the connecting link154from bending along axis234, while the support member210and groove214cooperate to prevent the connecting link154from bending in the direction perpendicular to the path of the groove214, as indicated by axis238. In the example provided, the link cover170covers a middle section of the central rod206, however it is understood that the link cover170could also cover the entire connecting link154, the drive link146, the driven link150, and/or the actuator158.

With reference toFIG. 5, a section view of another configuration of a connecting link242, and a link cover246for use with the flue door mechanism110and the main housing62is shown. Connecting link242can be substantially similar to connecting link154, having first and second ends (not shown), substantially similar to first and second ends198,202, and a central rod250, substantially similar to central rod206, except central rod250includes a first guide member or first support member254and a second guide member or second support member258. The main housing62can define a first groove262. As described above, it is understood that the main housing62can include or can be constructed of a plurality of individual pieces and that the first groove262can be defined by one of such pieces mounted to or integrally formed with the other(s) of such pieces. The first support member254can be substantially similar to support member210and first groove262can be substantially similar to groove214such that first support member254rides in first groove262in a similar manner. The second support member258can be substantially similar to the first support member254, except the second support member258extends from a side of the connecting link242opposite the first support member254. The link cover246can be substantially similar to link cover170, having a first flange266, a second flange270, and a cap274, and defining a link cavity278, except the cap274can define a second groove282. The second groove282can be arcuate in shape and can be substantially similar to the first groove262formed in the main housing62. The second support member258can be received in the second groove282and can slide along the second groove282as the connecting link242is moved between positions. The first support member254and first groove262, as well as the second support member258and second groove282cooperate to prevent the connecting link242from flexing, or bending perpendicular to the path of the second groove282, as indicated by axis286. The cap274and main housing62cooperate to prevent the connecting link242from bending in the direction away from the main housing62, as indicated by axis290. While the example provided includes the first support member254and first groove262, it is understood that the first support member254and first groove262could alternatively be eliminated, such that only the second support member258and second groove282are used.

With reference toFIGS. 6 and 7, another configuration of a connecting link294and a main housing298is shown. The main housing298is substantially similar to main housing62, except that instead of the groove214, the main housing298defines a guide member or support member302. The support member302can extend from an outer surface306of the main housing298. It is understood that the main housing62can include or can be constructed of a plurality of individual pieces and that the support member302can extend from one of such pieces mounted to or integrally formed with the other(s) of such pieces. The connecting link294can be substantially similar to connecting link154, having a first end310, a second end314, and a central rod318, except that instead of support member210, the central rod318defines a groove322. The groove322can be generally arcuate in shape. The support member302can be received in the groove322and can slide along the groove322as the connecting link294is moved between positions. The groove322and support member302cooperate to prevent the connecting link294from flexing, or bending in the direction perpendicular to the path of the groove322, indicated by axis326. The support member302can also be configured to receive a pin330. The pin330can have a generally cylindrical body334and a head338. The body334can be received through the groove322and engage the support member302. The body be fastened to the support member302by a plurality of threads (not shown) or other means. The head338can be configured to hold a washer342between the head338and the connecting link294. The washer342can be a diameter larger than the diameter of the groove322, such that the head338and washer cooperate to prevent the connecting link294from bending in the direction along axis346. It is understood that the head338and washer342can be integrally formed together.

With reference toFIG. 8, another configuration of the connecting link294and main housing298is shown. A link cover350, substantially similar to link cover170, can have first and second flanges354,358, a cap362, and defines a link cavity366. The first and second flanges354,358can be coupled to the main housing298by any suitable means, such as fasteners (not shown) or adhesive for example. The link cover350acts similarly to link cover170to prevent connecting link294from bending, in the direction along axis370, while the support member302and groove322prevent the connecting link294from bending in the direction perpendicular to the groove322, indicated by axis374.

Returning toFIGS. 2, 3A and 3B, the actuator158can be coupled to the drive link146to drive rotation of the drive link146at the drive pivot174. In the example provided, the actuator158is a servo motor having an output shaft (not shown) coupled to the drive pivot174, though other actuator types can be used, such as a linear actuator with a rack and pinion for example.

With specific reference toFIGS. 3A and 3B, the first door162can be disposed within the main housing62and can be rotatably coupled to the main housing62at the drive pivot174, while being non-rotatably coupled to the drive link146for common rotation at the drive pivot174. The first door162can have a first damper portion378and a second damper portion382, each extending radially outward from the drive pivot174. The second door166can be disposed within the main housing62and can be rotatably coupled to the main housing62at the driven pivot186, while being non-rotatably coupled to the driven link150for common rotation at the driven pivot186. The second door166can have a third damper portion386and a fourth damper portion390, each extending radially outward from the driven pivot186. In this way, the first and second doors162,166are both articulated when the actuator158rotates the drive link146.

The first door162and second door166can be configured to rotate between a closed position (FIG. 3A) and an open position (FIG. 3B). In the closed position, the first damper portion378can be positioned to block part of the inlet134, while the second damper portion382can be positioned to block the outlet138to prevent air from flowing through the outlet138of the hot air flue118. In the closed position, the third damper portion386and fourth damper portion390can block the remainder of the inlet134of the hot air flue118to prevent cool air from the evaporator102from entering the hot air flue118and coming in contact with the heater core106. The third damper portion386can sealingly engage the first damper portion378to prevent air from flowing through the inlet134between the first and second doors162,166. The cool air flue122is open, and generally all of the air is directed to flow directly from the evaporator102and air supply flue114, through the cool air flue122, and to the main flue126, in order to provide maximum cool air to the passenger compartment.

In the open position ofFIG. 3B, the first damper portion378can block the cool air flue122to prevent cool air from flowing from the air supply flue114, through the cool air flue, to the main flue126. The first damper portion378can be positioned to allow air to flow from the air supply flue114, through the inlet134, and to the heater core106. In the open position, the second damper portion382can be positioned to allow air to flow through the outlet138and to the main flue126. In the open position, the second door166can be positioned to allow air to flow from the evaporator102, through the inlet134, to the heater core106, and through the outlet138, to the main flue126. In this position, generally all of the air flow received by the main flue126is heated by the heater core106to provide maximum heating of the air.

With reference toFIGS. 9A and 9B, cross-sectional views of a second configuration of the main unit42are shown. The reference numbers similar to the reference numbers ofFIGS. 1-3Bdenote similar components. Similarly, the actuator158, drive link146, connecting link154, driven link150, and support member210are shown in dashed lines to indicate their locations and general positions relative to the main unit42and the components illustrated within the main unit42. Accordingly, only the differences will be described in detail, and the descriptions of the similar components ofFIGS. 1-3Bare incorporated by reference with respect to the similarly numbered components. In this configuration, the main housing62adefines an air supply flue114a, a first hot flue910, a second hot flue914, a first cool flue918, a second cool flue922, a first main flue926, and a second main flue930. The first hot flue910can have a first inlet934and a first outlet938. The first inlet934can be proximate to the air supply flue114, to receive air therefrom. The first outlet938can be proximate to the first main flue926, such that air can flow from the first hot flue910to the first main flue926through the first outlet938. The first cool flue918can be proximate to the air supply flue114and the first main flue926, such that air can flow from the air supply flue114, through the first cool flue918, to the first main flue926without flowing through the first or second hot flues910,914. The first main flue926can be fluidly coupled to the first air port82to provide air to the first zone duct50.

The second hot flue914can have a second inlet942and a second outlet946. The second inlet942can be proximate to the air supply flue114, to receive air therefrom. The second outlet946can be proximate to the second main flue930, such that air can flow from the second hot flue914to the second main flue930through the second outlet946. The second cool flue922can be proximate to the air supply flue114and the second main flue930, such that air can flow from the air supply flue114, through the second cool flue922, to the second main flue930without flowing through the first or second hot flues910,914. The second main flue930can be fluidly coupled to the second air port86to provide air to the second zone duct54.

The heater core106acan be located within the main housing62aand in line with the first and second hot flues910,914. The first and second hot flues910,914can divide the heater core106ainto two portions950,954, such that air passing through the heater core106avia the first hot flue910remains separate from air passing through the heater core106avia the second hot flue914. The evaporator102acan be located within the main housing62aand in line with the air supply flue114a. The air supply flue114can be fluidly coupled with the blower housing74aand intake port78to receive air therefrom.

The flue door mechanism110acan be generally similar to the flue door mechanism110, having drive link146, driven link150, connecting link154, actuator158, a first door958, and a second door962. While the present example shows the flue door mechanism110aas having connecting link154shown inFIG. 2, it is understood that flue door mechanism110acan alternatively use a connecting rod configured similar to connecting links242, or294, shown inFIG. 5, andFIGS. 6-8, in conjunction with the respective configurations of the main housings298, and/or link covers170,246,350, or pin330. The first door958can be disposed within the main housing62aand can be rotatably coupled to the main housing62aat the drive pivot174, while being non-rotatably coupled to the drive link146for common rotation at the drive pivot174. The first door958can have a first damper portion966extending radially outward from the drive pivot174. The second door962can be disposed within the main housing62aand can be rotatably coupled to the main housing62aat the driven pivot186, while being non-rotatably coupled to the driven link150for common rotation at the driven pivot186. The second door962can have a second damper portion970and a third damper portion974, each extending radially outward from the driven pivot186. In this way, the first and second doors958,962are both articulated when the actuator158rotates the drive link146.

The first door958and second door962can be configured to rotate between a closed position (FIG. 9A) and an open position (FIG. 9B). In the closed position, the first damper portion966can be positioned to block the first inlet934to prevent air from flowing from the air supply flue114, through the first hot flue910. In this position, the first damper portion966is positioned such that the first cool flue918is open to allow air to flow from the air supply flue114a, through the first cool flue918, and to the first main flue926. In this position, maximum cool air can be provided to the first zone34. The second damper portion970can be positioned to block the second inlet942to prevent air from flowing from the air supply flue114a, through the second hot flue914. In this position, the third damper portion974can be positioned such that the second cool flue922is open to allow air to flow from the air supply flue114a, through the second cool flue922, and to the second main flue930. In this position, maximum cool air can be provided to the second zone38.

In the open position, the first damper portion966can block the first cool flue918to prevent cool air from flowing directly from the air supply flue114a, to the first main flue926, through the first cool flue918. The first damper portion966is positioned such that the first inlet934is open to allow air to flow from the air supply flue114a, through the first hot flue910, to the first main flue926. In this position, maximum heating of the air directed to the first zone34is achieved. The second damper portion970can be positioned such that the second inlet942is open to allow air to flow from the air supply flue114a, through the second hot flue914, to the second main flue930. The third damper portion974can block the second cool flue922to prevent cool air from flowing directly from the air supply flue114a, to the second main flue930, through the second cool flue922. In this position, maximum heating of the air directed to the second zone38is achieved.

Thus, the present teachings provide for an HVAC system with a mechanism that can use a single linkage rod to accurately actuate multiple doors spaced apart within HVAC flues. The HVAC system of the present teachings overcomes the limitations of prior HVAC door mechanisms by mechanically preventing the linkage rod from flexing or bending outside of its desired movement path with minimal additional components or complexity. The present HVAC system thus allows the use of lighter weight materials in a four-bar linkage mechanism while maintaining consistent articulation of the flue doors, even when the mechanism components become heated.