Abstract:
An apparatus ( 100 ) controls a temperature of air flow from a temperature control system ( 10 ). The apparatus ( 100 ) includes a blend door ( 150 ), an output gear ( 140 ), and a biasing mechanism ( 124 ). The blend door ( 150 ) blocks air flow and has a plurality of positions, each blocking different amounts of air flow. The blend door ( 150 ) is rotatable about a first axis ( 142 ) between each of the plurality of positions. The output gear ( 140 ) is secured to the blend door ( 150 ) and is rotatable about the first axis ( 142 ) to rotate the blend door ( 150 ) between each of the plurality of positions. The biasing mechanism ( 124 ) facilitates rotation of the output gear ( 140 ) in a first rotation direction ( 136 ) and impedes rotation of the output gear ( 140 ) in a second rotation direction ( 138 ) opposite the first rotation direction ( 136 ) such that the torque necessary to rotate the output gear ( 140 ) in the first rotation direction ( 136 ) is substantially equal to the torque necessary to rotate the output gear ( 140 ) in the second rotation direction ( 138 ). The biasing mechanism ( 124 ) includes a ramping surface ( 132  or  332 ) and a projecting member ( 126, 226,  or  326 ) biasingly engaging the ramping surface ( 132  or  332 ).

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to an automotive temperature control system and, more particularly, to an apparatus for balancing the torque necessary to adjust the temperature of the air flow produced by the automotive temperature control system.  
         BACKGROUND OF THE INVENTION  
         [0002]    A conventional apparatus controls the output temperature of an automotive temperature control system by controlling the position of a mechanical blend door that resides within the automotive temperature control system. This blend door determines the amount of air flow that passes through a heater core and the amount of air flow that bypasses the heater core. The most economical control apparatus for the blend door is a completely mechanical actuator that requires no electrical or pneumatic assistance. The source of power for the conventional mechanical actuator is the human hand. A person may operate this mechanical actuator by rotating a temperature control knob that is typically mounted on an instrument panel of a vehicle.  
           [0003]    Since a human hand powers the mechanical actuator, the output torque produced by the mechanical actuator is very low. Also, the human hand is sensitive to the variations of torque required to adjust the position of the blend door. For a conventional automotive temperature control system, the weight of the blend door is the main cause of the torque variations that the human hand feels.  
         DESCRIPTION OF THE PRIOR ART  
         [0004]    This problem has been previously addressed by attaching a counterweight to the blend door so that the torque necessary to move the door upward or downward is balanced. However, this small torque requirement also leads to undesirable vibration and even significant movement of the blend door due to the vibration and inertial forces created by an operating vehicle.  
           [0005]    To create a cost efficient mechanical actuator that provides a consistent torque effort throughout the adjustment range of the blend door in both rotation directions, a counter-balancing mechanism in accordance with the present invention may be integrated into the design of the temperature control system. The counter-balancing mechanism offsets the weight of the blend door without undesirable vibration or movement of the blend door. As a result, the counter-balancing mechanism removes the input torque variations that the person feels as he or she adjusts the blend door in the pursuit of adjusting the output temperature of the temperature control system.  
         SUMMARY OF THE INVENTION  
         [0006]    In accordance with one feature of the present invention, an apparatus controls a temperature of air flow from a temperature control system. The apparatus includes a blend door, an output gear, and a biasing mechanism. The blend door blocks air flow and has a plurality of positions, each blocking different amounts of air flow. The blend door is rotatable about a first axis between each of the plurality of positions. The output gear is secured to the blend door and is rotatable about the first axis to rotate the blend door between each of the plurality of positions. The biasing mechanism facilitates rotation of the output gear in a first rotation direction and impedes rotation of the output gear in a second rotation direction opposite the first rotation direction such that the torque necessary to rotate the output gear in the first rotation direction is substantially equal to the torque necessary to rotate the output gear in the second rotation direction. The biasing mechanism includes a ramping surface and a projecting member biasingly engaging the ramping surface.  
           [0007]    In accordance with another feature of the present invention, an apparatus controls an output temperature of a temperature control system. The apparatus includes an output gear, an input gear, and a biasing mechanism. The output gear is rotatable about a first axis between a plurality of rotation positions. The input gear drives the output gear. The input gear is rotatable about a second axis parallel to the first axis to rotate the output gear to each of the plurality of rotation positions. The biasing mechanism facilitates rotation of the input gear in a first rotation direction and impedes rotation of the input gear in a second rotation direction opposite the first rotation direction such that the torque necessary to rotate the input gear in the first rotation direction is substantially equal to the torque necessary to rotate the input gear in the second rotation direction. The biasing mechanism includes a ramping surface on the input gear and a resilient structure for engaging the ramping surface.  
           [0008]    In accordance with still another feature of the present invention, a method controls a temperature of air flow from a temperature control system. The method includes the following steps: rotating a first gear about a first axis in a first rotation direction; imparting rotation to a second gear and a blend door about a second axis parallel to the first axis in a second rotation direction opposite the first rotation direction by the rotating of the first gear in the first rotation direction; applying resistance to rotation of the first gear in the first rotation direction by biasing a projecting member against a ramping surface; rotating the first gear about the first axis in a third rotation direction opposite the first rotation direction; imparting rotation to the second gear and the blend door about the second axis in a fourth rotation direction opposite the second rotation direction by the rotating of the first gear in the third rotation direction; and applying assistance to rotation of the first gear in the third rotation direction by biasing the projecting member against the ramping surface such that the torque necessary to rotate the first gear in the first rotation direction is substantially equal to the torque necessary to rotate the first gear in the third rotation direction. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    The foregoing and other features of the present invention will become apparent to those skilled in the art to which the present invention relates upon reading the following description with reference to the accompanying drawings, in which:  
         [0010]    [0010]FIG. 1 is a schematic view of an apparatus in accordance with the present invention;  
         [0011]    [0011]FIG. 2 is an enlarged schematic view of part of the apparatus of FIG. 1;  
         [0012]    [0012]FIG. 3 is a perspective view of the part of the apparatus of FIG. 1;  
         [0013]    [0013]FIG. 4 is a detailed perspective view of part of the apparatus of FIG. 3;  
         [0014]    [0014]FIG. 5 is a schematic view of a temperature control system for use with the apparatus of FIG. 1;  
         [0015]    [0015]FIG. 6 is a schematic view of one feature of the apparatus of FIG. 1;  
         [0016]    [0016]FIG. 7 is a schematic view of another feature of the apparatus of FIG. 1; and  
         [0017]    [0017]FIG. 8 is a schematic view of still another feature of the apparatus of FIG. 1. 
     
    
     DESCRIPTION OF PREFERRED EMBODIMENT  
       [0018]    In accordance with the present invention, FIG. 1 illustrates an apparatus  100  for use with an automotive temperature control system  10  (FIG. 5). The apparatus  100  controls the temperature of air flow from the temperature control system  10 . The apparatus  100  includes a climate control unit  110 , a mechanical actuator  120 , and a blend door  150  (FIG. 5).  
         [0019]    As viewed schematically in FIG. 1, the climate control unit  110  interfaces with an occupant of a vehicle. The climate control unit  110  is typically mounted on an instrument panel of the vehicle. The climate control unit  110  includes a manually rotatable temperature control knob  112 . The occupant controls the output temperature of the temperature control system  10  by rotating the temperature control knob  112  between the positions of Full-Cool  114  and Full-Warm  116 . The temperature control knob  112  typically has detent mechanisms (not shown) that provide a tactile feel so that the occupant may position the temperature control knob at distinct 10° increments. The increments are indicated by the lines  118 . The rotation of the temperature control knob  112  creates a linear motion of cables (not shown) that move within a conduit  119  (as is known in the art). The cables are attached to the mechanical actuator  120  and transfer the rotation of the temperature control knob  112  to the mechanical actuator  120 .  
         [0020]    As viewed in FIG. 2, the mechanical actuator  120  includes a housing  122 , an input gear  130  secured in the housing and rotatable about an input axis  131  in the housing, an output gear  140  secured in the housing and rotatable about an output axis  141  parallel to the input axis, and a biasing mechanism  124 ,  224 , or  324  (FIGS.  6 - 8 ). The input gear  130  is rotated by the cables of the conduit  119  when the temperature control knob  112  is similarly rotated (as is known in the art). The input gear  130  has teeth  134  in meshing engagement with teeth  144  on the output gear  140 . The input gear  130  imparts opposite rotation to the output gear  140  as the input gear rotates and drives the output gear.  
         [0021]    When rotated, the input gear  130  transmits torque to the output gear  140 . The output gear  140  is attached to an output shaft  149 . The output gear  140  rotates the output shaft  149 . The output shaft  149  is attached to a blend door shaft  152  of the blend door  150  (FIG. 5).  
         [0022]    As viewed in FIG. 5, the temperature control system  10  includes a system housing  12 , a heater core  14 , and an evaporator core  16  for use with the blend door  150  of the apparatus  100 . An air flow enters the system housing  12  at an entrance  18 . The air flow passes through the evaporator core  16 . The evaporator core  16  cools and dehumidifies the air flow. The position of the blend door  150  determines whether and how much of the air flow is blocked and/or passes through the heater core  14 . Cold air flow  22  and hot air flow  24  are mixed together at an exit  20  of the temperature control system  10 .  
         [0023]    As viewed in FIGS. 3, 4,  6 , and  7 , the biasing mechanism  124  or  224  may have a ramping surface  132  along the outer diameter of the input gear  130 . The ramping surface  132  defines an annular surface that is axially sloped relative to the input axis  131  and extends tangentially around the circular perimeter of the input gear  130 . The shape of the ramping surface  132  may be determined by mathematical calculation for optimum control of the apparatus  100 . As viewed in FIGS. 6 and 7, the ramping surface  132  is slightly concave and curved toward the body of the input gear  130 .  
         [0024]    As viewed in FIG. 6, the biasing mechanism  124  may further include a resilient structure such as a projecting plunger-type member  126  axially biased against the ramping surface  132  such that the torque necessary to rotate the input gear  130  in a first rotation direction  136  is substantially equal to the torque necessary to rotate the input gear in a second rotation direction  138  opposite the first rotation direction. The plunger-type member  126  and a compressed spring member  128  are secured in a portion  123  of the housing  122  and provide a continuous axial biasing force against the ramping surface  132  as the input gear  130  rotates about the input axis  131 . The curvature and slope of the ramping surface  132  convert the axial biasing force into components of axial force against the body of the input gear  130  and rotational force against the input gear about the input axis  131 .  
         [0025]    As viewed in FIG. 7, an alternative biasing mechanism  224  may include a resilient structure such as a projecting cantilever-type member  226  resiliently biased against the ramping surface  132  such that the torque necessary to rotate the input gear  130  in the first rotation direction  136  is substantially equal to the torque necessary to rotate the input gear in the second rotation direction  138 . The deflected cantilever-type member  226 , acting as a flexure spring, is secured to a portion  223  of the housing  122  and provides a continuous axial biasing force against the ramping surface  132  as the input gear  130  rotates about the input axis  131 . The curvature and slope of the ramping surface  132  convert the axial biasing force into components of axial force against the body of the input gear  130  and rotational force against the input gear about the input axis  131 .  
         [0026]    As viewed in FIG. 8, another biasing mechanism  324  may include a resilient structure such as a projecting pivoting-type member  326  biased against a radially curved ramping surface  332  (instead of the ramping surface  132 ) such that the torque necessary to rotate the input gear  130  in the first rotation direction  136  is substantially equal to the torque necessary to rotate the input gear in the second rotation direction  138 . The shape of the ramping surface  332  may be determined by mathematical calculation for optimum control of the apparatus  100 . The ramping surface  332  is curved around the input axis  131  and extends axially away from the body of the input gear  130 .  
         [0027]    The L-shaped pivoting-type member  326  is rotatable about a pivot axis  331  and is rotatably secured to a portion  323  of the housing  122 . The pivot axis  331  is typically parallel to the input axis  131  and the output axis  141 . A stretched spring member  328  is secured to another portion  325  of the housing  122  and provides a continuous rotational biasing force against the pivoting-type member  326  about the pivot axis  331  and thereby a continuous radial biasing force against the ramping surface  332  as the input gear  130  rotates about the input axis  131 . The curvature of the ramping surface  332  converts the radial biasing force into components of radial biasing force against the center of the input gear  130  and rotational force against the input gear about the input axis  131 .  
         [0028]    In operation, the weight of the blend door  150  creates a torque T door  about the output axis  141 . The torque T door  is generated at the center of gravity  151  of the blend door  150  (FIG. 5). Due to the weight of the blend door  150 , the torque T door  causes the required input torque at the temperature control knob  112  to be greater when it is rotated from Full-Cool  114  to Full-Warm  116  (a first rotation direction  136 ) than in the opposite direction from Full-Warm to Full-Cool (a second rotation direction  138 ).  
         [0029]    When the temperature control knob  112  is rotated in the first rotation direction  136 , the blend door  150  is pivoted upward, or lifted. When the temperature control knob  112  is rotated in the second rotation direction  138 , the blend door  150  is pivoted downward, or lowered. The heavier the blend door  150 , the greater the difference of torque between the two opposite rotational directions  136  and  138 . This situation occurs whenever a blend door moves in the vertical direction, regardless whether it is the pivoting door  150  of FIG. 5 or a sliding door (not shown).  
         [0030]    Since the temperature control knob  112  is operatively engaged with the blend door  150 , the human hand can feel the torque difference when rotating the temperature control knob in each direction. A temperature control system that has drastic temperature control knob torque differences between opposite rotational directions may give a vehicle occupant the impression of a low quality temperature control system.  
         [0031]    To compensate for the weight of the blend door  150 , the ramping surface  132  or  332  has been added to the input gear  130 . The projecting member  126 ,  226 , or  326  contacts the ramping surface  132  or  332  and exerts a force on the ramping surface due to the spring member  128  or  328  or the projecting member  226  itself. As discussed above, the shape of the ramping surface  132  or  332  may be generated by a mathematical equation that allows control of the resultant forces at the interface of the ramping surface  132  or  332  and the projecting member  126 ,  226 , or  326 .  
         [0032]    Each increment of rotation of the temperature control knob  112  may impart a proportional amount of same direction rotation to the input gear  130  through the conduit  119 . As the temperature control knob  112 , and thereby the input gear  130 , are rotated in the first rotation direction  136  (i.e., clockwise as viewed in FIG. 1), the required input torque to the temperature control knob is governed by the following equation: 
         
       T 
       knob 
       =T 
       detent 
       +T 
       friction 
       +T 
       door 
       −T 
       bias1 
     
         [0033]    where:  
         [0034]    T knob =input torque at the temperature control knob;  
         [0035]    T detent =torque caused by the detent mechanisms;  
         [0036]    T friction =torque generated by the actuator due to internal friction;  
         [0037]    T door =torque generated by the weight of the blend door; and  
         [0038]    T bias1 =resultant torque due to the biasing mechanism.  
         [0039]    The detent torque T detent  is a constant torque that one of the detent mechanisms generates to ensure that the blend door  150  remains stationary once the occupant releases the temperature control knob  112 . The friction torque T friction  is the unavoidable torque that is added to the input torque requirements of any mechanical actuator due to friction forces generated at all contact surfaces within the mechanical actuator  120 , the climate control unit  110 , and the conduit  119 .  
         [0040]    The biasing mechanism torque T bias1  is the resultant torque due to the biasing mechanism  124 ,  224 , or  324  when the blend door  150  is being raised (i.e., pivoted counterclockwise as viewed in FIG. 5). As the blend door  150  pivots upward, the ramping surface  132  or  332  moves away from the projection member  126 ,  226 , or  326 . The forces generated at the projecting member-to-ramping surface interface thereby assist rotation of the input gear  130  and generate the resulting torque T bias1 . The magnitude of T bias1  is typically small compared to the other torque values discussed above.  
         [0041]    When the temperature control knob  112 , and thereby the input gear  130 , are rotated in the second rotation direction  138  (i.e., counterclockwise as viewed in FIG. 1), the blend door  150  is lowered (i.e., pivoted clockwise as viewed in FIG. 5) and the directions of the torques T detent  and T friction  are reversed. The directions of T detent  and T friction  are always opposite of the rotational direction of the temperature control knob  112  and the input gear  130 . The direction of T door  is in the same direction as before, however, since T door  is created by gravity.  
         [0042]    Now the ramping surface  132 ,  332  is moving toward the projecting member  126 ,  226 ,  326  and is causing the spring member  128  to be compressed more, the cantilever-type member  226  to be deflected more, or the spring member  328  to be stretched, or extended, more. The compression/deflection/extension of the spring members  128 ,  226 ,  328  generates a force on the ramping surface  132 ,  332  that resists rotation of the input gear  130 . The resulting force at the projecting member-to-ramping surface interface creates the resulting torque of T bias2 . The magnitude of T bias2  is typically much larger than T bias1  and has the opposite direction of T bias1 .  
         [0043]    As the temperature control knob  112 , and thereby the input gear  130 , are rotated in the second rotation direction  138 , the required input torque to the temperature control knob is governed by the following equation: 
         
       T 
       knob 
       =T 
       detent 
       +T 
       friction 
       −T 
       door 
       +T 
       bias2 
     
         [0044]    where:  
         [0045]    T knob =input torque at the temperature control knob;  
         [0046]    T detent =torque caused by the detent mechanisms;  
         [0047]    T friction =torque generated by the actuator due to internal friction;  
         [0048]    T door =torque generated by the weight of the blend door; and  
         [0049]    T bias2 =resultant torque due to the biasing mechanism.  
         [0050]    By controlling the mechanical parameters of the spring members  128 ,  226 ,  328 , the weight of the blend door  150  may be compensated for in a way that the human hand cannot feel a difference in input torque T knob  between the opposite rotation directions  136  and  138  of the temperature control knob  112 . The weight of the blend door  150  is essentially balanced by mathematically manipulating the relative magnitudes of T bias1  and T bias2  so that the final input torque T knob  in both directions is substantially equal.  
         [0051]    The projecting members  126 ,  226 ,  326  and spring members  128 ,  226 ,  328  are one way of providing a controlled force on the ramping surfaces  132 ,  332 . There are many ways to provide a controlled force on the ramping surface  132 ,  332 . As viewed in FIG. 6, the spring biased plunger-type member  126  may provide the force on the ramping surface  132 . As viewed in FIG. 7, the flexible cantilever-type member  232  may provide the force on the ramping surface  132 . As viewed in FIG. 8, the spring biased pivoting-type member  326  may provide the force on an alternative ramping surface  332 . A flexible cantilever-type member (not shown) similar to the member  226  may also provide the force on the ramping surface  332 .  
         [0052]    As described above, the detent mechanisms maintain the blend door  150  in a fixed position once the human hand releases the temperature control knob  112 . Due to the motion of the vehicle and the associated vibration, the weight of the blend door  150  may cause the blend door to start moving downward despite the detent mechanisms. The temperature control knob  112  would then rotate on its own as the blend door  150  “drifts” downward. This situation is known as “door walk”. The heavier the blend door (i.e., a metal blend door), the more pronounced the door walk. Door walk can be mitigated with a biasing mechanism having a viscous damper. As viewed in FIG. 8, a viscous damper  329  may be included with the biasing mechanism  324 . The viscous damper is connected in series with the spring member  328  at one end and the pivoting-type member  326  at the other end.  
         [0053]    Alternatively, the viscous damper  328  may be connected in parallel with the spring member  328  with the portion  325  of the housing  122  at one end and the pivoting-type member  326  at the other end (not shown). Additionally, a damping device may be utilized with the biasing mechanisms  124 ,  224  of FIGS. 6 and 7.  
         [0054]    A method in accordance with the present invention controls a temperature of air flow from the temperature control system  10 . The method includes the steps of: rotating a first gear  130  about a first axis  132  in a first rotation direction  136 ; imparting rotation to a second gear  140  and a blend door  150  about a second axis  142  parallel to the first axis  132  in a second rotation direction  138  opposite the first rotation direction  136  by the rotating of the first gear  130  in the first rotation direction  136 ; applying resistance to rotation of the first gear  130  in the first rotation direction  136  by biasing a projecting member  126 ,  226 , or  326  against a ramping surface  132  or  332 ; rotating the first gear  130  about the first axis  132  in a third rotation direction  138  opposite the first rotation direction  136 ; imparting rotation to the second gear  140  and the blend door  150  about the second axis  142  in a fourth rotation direction  136  opposite the second rotation direction  138  by the rotating of the first gear  130  in the third rotation direction  138 ; and applying assistance to rotation of the first gear  130  in the third rotation direction  138  by biasing the projecting member  126 ,  226 , or  326  against the ramping surface  132  or  332  such that the torque necessary to rotate the first gear  130  in the first rotation direction  136  is substantially equal to the torque necessary to rotate the first gear  130  in the third rotation direction  138 .  
         [0055]    The biasing steps of the method may further include axially biasing the projecting member  126  against the ramping surface  132  with the projecting member  126  extending axially toward the ramping surface  132 . Alternatively, the biasing steps of the method may further include axially biasing the projecting member  226  against the ramping surface  132  with the projecting member  226  extending tangentially about the first gear  130 .  
         [0056]    From the above description of the invention, those skilled in the art will perceive improvements, changes and modifications. Such improvements, changes and modifications within the skill of the art are intended to be covered by the appended claims.