Abstract:
A ventilation system ( 20 ) made up of a wiring harness ( 22 ), a power source ( 21 ), a fan motor ( 23 ), a resistance circuit ( 70 ), and a selector switch ( 30 -or  40 ) is taught. The selector switch ( 30  or  40 ) has five or six positions, and determines a different current through the fan motor ( 23 ) for each position. The resistance circuit ( 70 ) limits the current in three or four of the positions. A control apparatus ( 25 ) is mechanically coupled to the selector switch ( 23 ) and configured to allow a user to select one of the positions. One of the positions is an “off” position passing zero current through the fan motor ( 23 ), and one of the positions is a “maximum” position passing a maximum current through the fan motor ( 23 ). Each of the other positions is intermediate and passes a current through the fan motor ( 23 ) and a resistance in the resistance circuit ( 70 ) to limit the current.

Description:
TECHNICAL FIELD OF THE INVENTION  
         [0001]    The present invention relates to the field of ventilation systems. More specifically, the present invention relates to the field of fan motor control in automotive ventilation systems.  
         BACKGROUND OF THE INVENTION  
         [0002]    In the manufacture of automobiles and other vehicles, otherwise-identical vehicles are often-differentiated solely by peripheral or “luxury” items. For example, the “standard” and “luxury” models of a given car may be identical except for an option package, wherein the “standard” package contains a given engine, manual windows, manual door locks, and a four-speed air-conditioner/ventilation fan, while the “luxury” package contains a larger engine, electric windows, electric door locks, and a five-speed air-conditioner/ventilation fan.  
           [0003]    It is desirous that the basic vehicle contains as few model-differentiated components as possible. For example, if the vehicle were to be designed so that all model-differentiated components may be installed during the final stages of assembly, then the “raw” vehicles may be held at the non-model-specific stage until a given model is called for. This results in finer control over production, leading to improvements in distribution and inventory control, and ultimately may result in significant cost benefits.  
           [0004]    In the area of heating, ventilation, and air-conditioning (HVAC), different models often have different controls. These differences may be exemplified by the number of speeds in a ventilation fan, with more luxurious models having finer fan control, i.e., more fan speeds. Unfortunately, this typically required the use of a differentiated wiring harness for the variant fan-control connections.  
           [0005]    Since wiring harnesses are typically installed early in vehicle production, the use of different wiring harnesses for different models requires model-level commitment at an early production stage. This is both costly and inefficient.  
           [0006]    Alternatively, wiring harnesses may be used that have multiple-model wiring, i.e., extra wires in the harness to allow for the more luxurious models. This, too, poses problems. Not only is the inclusion of the extra wires an unnecessary expense for the less luxurious models, but the possibility exist of confusion between and/or misapplication of connectors during manufacturing quality control, and during downstream repairs and maintenance.  
         SUMMARY OF THE INVENTION  
         [0007]    Accordingly, it is an advantage of the present invention that a fan motor control for a ventilation system is provided.  
           [0008]    It is another advantage of the present invention that a single wiring harness is used with either a four-speed or five-speed fan motor control.  
           [0009]    It is another advantage of the present invention that a single resistor network is used with either a four-speed or five-speed fan motor control.  
           [0010]    The above and other advantages of the present invention are carried out in one form by a control assembly for a fan motor in a ventilation system. The control assembly incorporates a resistor network comprising a plurality of resistors, and a selector switch electrically coupled to the fan motor and the resistor network, where the switch has 5 or 6 positions, determines a different current through the fan motor for each of the 5 or 6 positions, and the resistor network limits the current in 3 or 4 of the 5 or 6 positions, respectively.  
           [0011]    The above and other advantages of the present invention are carried out in another form by a method of controlling a fan motor in an automotive ventilation system. The method includes setting a selector switch to one of 5 or 6 positions, establishing a current through the fan motor in response to the setting of the selector switch, and operating the fan motor as a function of the established current. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    A more complete understanding of the present invention may be derived by referring to the detailed description and claims when considered in connection with the Figures, wherein like reference numbers refer to similar items throughout the Figures, and:  
         [0013]    [0013]FIG. 1 shows a schematic view of an automotive ventilation system having a six-position selector switch in a first “off” position in accordance with a preferred embodiment of the present invention;  
         [0014]    [0014]FIG. 2 shows a schematic view of the automotive ventilation system of FIG. 1 demonstrating current flow when the selector switch is in a second “low” position in accordance with a preferred embodiment of the present invention;  
         [0015]    [0015]FIG. 3 shows a schematic view of the automotive ventilation system of FIG. 1 demonstrating current flow when the selector switch is in a third “medium-low” position in accordance with a preferred embodiment of the present invention;  
         [0016]    [0016]FIG. 4 shows a schematic view of the automotive ventilation system of FIG. 1 demonstrating current flow when the selector switch is in a fourth “medium” position in accordance with a preferred embodiment of the present invention;  
         [0017]    [0017]FIG. 5 shows a schematic view of the automotive ventilation system of FIG. 1 demonstrating current flow when the selector switch is in a fifth “medium-high” position in accordance with a preferred embodiment of the present invention;  
         [0018]    [0018]FIG. 6 shows a schematic view of the automotive ventilation system of FIG. 1 demonstrating current flow when the selector switch is in a fifth “high” position in accordance with a preferred embodiment of the present invention;  
         [0019]    [0019]FIG. 7 shows a schematic view of an automotive ventilation system having a five-position selector switch in a first “off” position in accordance with an alternative preferred embodiment of the present invention;  
         [0020]    [0020]FIG. 8 shows a schematic view of the automotive ventilation system of FIG. 7 demonstrating current flow when the selector switch is in a second “low” position in accordance with an alternative preferred embodiment of the present invention;  
         [0021]    [0021]FIG. 9 shows a schematic view of the automotive ventilation system of FIG. 7 demonstrating current flow when the selector switch is in a third “medium-low” position in accordance with an alternative preferred embodiment of the present invention;  
         [0022]    [0022]FIG. 10 shows a schematic view of the automotive ventilation system of FIG. 7 demonstrating current flow when the selector switch is in a fourth “medium-high” position in accordance with an alternative preferred embodiment of the present invention; and  
         [0023]    [0023]FIG. 11 shows a schematic view of the automotive ventilation system of FIG. 7 demonstrating current flow when the selector switch is in a fifth “high” position in accordance with an alternative preferred embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]    [0024]FIGS. 1 through 6 show schematic views of an automotive ventilation system  20  having a six-position selector switch  30  in a first “off” position  31  (FIG. 1), and demonstrating current flow when selector switch  30  is in a second “low” position  32  (FIG. 2), a third “medium-low” position  33  (FIG. 3), a fourth “medium” position  34  (FIG. 4), a fifth “medium-high” position  35  (FIG. 5), and a sixth “high” position  36  (FIG. 6) in accordance with a preferred embodiment of the present invention. Similarly, FIGS. 7 through 11 show schematic views of automotive ventilation system  20  having a five-position selector switch  40  in a first “off” position  41  (FIG. 7), and demonstrating current flow when selector switch  40  is in a second “low” position  42  (FIG. 8), a third “medium-low” position  44  (FIG. 9), a fourth “medium-high” position  45  (FIG. 10), and fifth “high” position  46  (FIG. 11) in accordance with an alternative preferred embodiment of the present invention. The following discussion refers to FIGS. 1 through 11.  
         [0025]    Ventilation system  20  may be used as a part of an automotive heating, ventilation, and air-conditioning (HVAC) system as found in cars, truck, boats, aircraft, and other vehicles. Those skilled in the art will appreciate that system  20  is not limited to vehicular use, however, and may be used wherever flexible ventilation control is desired and a resistive fan speed control is appropriate.  
         [0026]    Ventilation system  20  consists of a power source  21 , a wiring harness  22 , a fan motor  23 , and a control assembly  24 . Control assembly  24  is in turn made up of selector switch  30  or  40 , a resistor network  50 , and a control apparatus  25 . Control apparatus  25  is made up of a selector and linkages necessary to set selector switch  30  or  40  to any desired position.  
         [0027]    Selector switches  30  and  40  have N positions, where N=6 for selector switch  30  (FIGS. 1 through 6), and N=5 for selector switch  40  (FIGS. 7 through 11). Since one of these positions is an “off” position, selector switches  30  and  40  are five-speed and four-speed selector switches, respectively.  
         [0028]    Control apparatus  25  is depicted in FIGS. 1 through 6 as a knob having N=6 positions, labeled “0”, “1”, “2”, “3”, “4”, and “5”, and coupled to six-position selector switch  30 . Through the use of control apparatus  25 , selector switch  30  may be positioned to an “off” position P (1)    31  (FIG. 1), a “low-speed” position P (2)    32  (FIG. 2), a “medium-low-speed” position P (N−3)  (where N−3=6−3=3)  33  (FIG. 3), a “medium-speed” position P (N−2)  (where N−2=6−2=4)  34  (FIG. 4), a “medium-high-speed” position P (N−1)  (where N−1=6−1=5)  35  (FIG. 5), and a “high-speed” or “maximum” position P (N)  where N=6) 36 (FIG. 6).  
         [0029]    Similarly, control apparatus  25  is depicted in FIGS. 7 through 11 as a knob having N=5 positions, labeled “0”, “1”, “2”, “3”, and “4”, and coupled to five-position selector switch  40 . Through the use of control apparatus  25 , selector switch  40  may be positioned to an “off” position P (1)    41  (FIG. 7), a “low-speed” position P (2)    42  (FIG. 8), a “medium-low-speed” position P (N−2)  (where N−2=5−2=3)  44  (FIG. 9), a “medium-high-speed” position P (N−1)  (where N−1=5−1=4)  45  (FIG. 10), and a “high-speed” or “maximum” position P (N)  where N=5)  46  (FIG. 11).  
         [0030]    Those skilled in the art will appreciate that the speed labels discussed hereinbefore are relative only to the speed of fan motor  23  when used in conjunction with that particular selector switch  30  or  40 . That is, the labels “low-speed,” “medium-low-speed,” “medium-speed,” “medium-high-speed,” and “high-speed” used in conjunction with six-position selector switch  30  are germane only in relation to each other when fan motor  23  is used with six-position selector switch  30 , and the labels “low-speed,” “medium-low-speed,” “medium-high-speed,” and “high-speed” used in conjunction with five-position selector switch  40  are germane only in relation to each other when fan motor  23  is used with five-position selector switch  40 .  
         [0031]    On the other hand, the labels “off” and “maximum” represent absolute speed terms of zero and maximum speed of fan motor  23  regardless of whether selector switch  30  or  40  is used.  
         [0032]    Referring to FIGS. 1 and 7, setting selector switch  30  or  40  to position P (1)    31  or  41 , respectively, an “off” setting, interrupts the circuit to fan motor  23  from power source  21 . This establishes a current I (1)    61  through fan motor  23  to be zero, and fan motor  23  operates as off (i.e., attain a speed of zero).  
         [0033]    Referring to FIGS. 6 and 11, setting selector switch  30  or  40  to position P (N)    36  or  46 , respectively, a “maximum” setting, places fan motor  23  directly across power source  21 . This establishes a current I (N)    66  through fan motor  23  to be a maximum current, and fan motor  23  operates at a maximum speed.  
         [0034]    Referring to FIGS. 1 through 11, resistor network  50  is made up of resistors R 1    51 , R 2    52 , R 3    53 , R 4    54 , and R 5    55 . Together, resistors R 1    51 , R 2    52 , R 3    53 , R 4    54 , and R 5    55  form a resistance circuit  70 . Resistor network  50  and resistance circuit  70  are the same regardless of whether six-position selector switch  30  (FIGS. 1 through 6) or five-position selector switch  40  (FIGS. 7 through 11) is used. Each current path through resistance circuit  70  encounters a different resistance.  
         [0035]    Referring to FIGS. 2 and 8, setting selector switch  30  or  40  to position P (2)    32  or  42 , respectively, establishes a current I (2)    62  through fan motor  23  and a resistance R (2)    72  of resistance circuit  70 . Resistance R (2)    72  is made up of resistors R 1    51  and R 4    54  in series. That is:  
           R   (2)   =R   1   +R   4   (1)  
         [0036]    Since current I (1)    61  (FIGS. 1 and 7) is zero, current I (2)    62  is greater than current I (1)    61  (FIGS. 1 and 7).  
         [0037]    Referring to FIG. 3, setting selector switch  30  to position P (N−3)    33  establishes a current I (N−3)    63  through fan motor  23  and a resistance R (N−3)    73  of resistance circuit  70 . Resistance R (N−3)   73  is made up of resistor R 1    51  in series with a combination of resistor R 4    54  in parallel with a combination of resistors R 2    52  and R 3    53  in series. That is:  
           R   (N−3)   =R   1 +[( R   4 ) −1 +( R   2   +R   3 ) −1 ] 1   (2)  
         [0038]    Resistance R (N−3)    73  is less than resistance R (2)    72  (FIG. 2), therefore current I (N−3)    63  is greater than current I (2)    62  (FIG. 2).  
         [0039]    It will be noted that there is no current I (N−3)    63  for five-position selector switch  40 , i.e., there is no five-position Figure corresponding to six-position FIG. 3. In the preferred embodiments, it is current I (N−3)    63 , and its corresponding fan-motor speed, that has been removed to accommodate five-position selector switch  40 .  
         [0040]    Those skilled in the art will appreciate that, while any current and corresponding speed may be removed without affecting the spirit of the present invention, it is desirable that a current representing a “medium” fan speed be removed, i.e., one of currents I (N−3)    63 , I (N−2)    64 , or I (N−1)    65  (currents I (N−2)    64  and I (N−1)    65  discussed hereinafter). It will readily be appreciated that several functions in an HVAC system require some air movement, but a minimal air movement is advantageous. For this reason, it is desirable that the lowest fan speed be retained, i.e., current I (2)    62 . It will also be appreciated there will often be conditions under which a maximum movement of air is advantageous. Therefore, it is desirable that the highest fan speed be retained, i.e., current I (N)    66 . In the preferred embodiment depicted in FIGS. 7 through 11, current I (N−3)    63  has been eliminated, but either of currents I (N−2)    64  or I (N−1)    65  may be eliminated instead without departing from the spirit of the present invention.  
         [0041]    Referring to FIGS. 4 and 9, setting selector switch  30  or  40  to position P (N−2)    34  or  44 , respectively, establishes current I (N−2)    64  through fan motor  23  and a resistance R (N−2)    74  of resistance circuit  70 . Resistance R (N−2)    74  is made up of resistors R 1    51 , R 2    52 , and R 3    53  in series. That is:  
           R   (N−2)   =R   1   +R   2   +R   3   (3)  
         [0042]    Resistance R (N−2)    74  is less than resistance R (N−3)    73  (FIG. 3) or resistance R (2)    72  (FIG. 8), therefore current I (N−2)    64  is greater than current I (N−3)    63  (FIG. 3) or current I (2)    62  (FIG. 8).  
         [0043]    Referring to FIGS. 5 and 10, setting selector switch  30  or  40  to position P (N−1)    35  or  45 , respectively, establishes current I (N−1)    65  through fan motor  23  and a resistance R (N−1)    75  of resistance circuit  70 . Resistance R (N−1)    75  is made up of resistors R 1    51 , R 2    52 , and R 5    55  in series. That is:  
           R   (N−1)   =R   1   +R   2   +R   5   (4)  
         [0044]    Resistance R (N−1)    75  is less than resistance R (N−2)  (FIGS. 4 and 9), therefore current I (N−1)    65  is greater than current I (N−2)    64  (FIGS. 4 and 9).  
         [0045]    In summary, the present invention teaches a speed control assembly  24  for a ventilation system  20 . A single wiring harness  22  and a single resistor network  50  is used with either a five-position (four-speed) selector switch  40  or a six-position (five-speed) selector switch  30 .  
         [0046]    Although the preferred embodiments of the invention have been illustrated and described in detail, it will be readily apparent to those skilled in the art that various modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.