Abstract:
An air conditioner unit comprises a case having a plurality of air passages defined therein; two pivotal mode doors pivotally arranged in the case to provide various operation modes of the air conditioner unit when assuming given angular positions, each of the mode doors having a pivot shaft of which leading end is exposed to the outside from a wall of the case; and a mode door actuating mechanism attached to an outer surface of the wall of the case to actuate the two pivotal mode doors. The mode door actuating mechanism comprises a base structure adapted to be mounted to the outer surface of the wall; two operation levers pivotally held at respective hub portions thereof by the base structure, each operation lever having a cam opening and being coaxially connected to the leading end of the pivot shaft of corresponding one of the two mode doors; a slider member slidably held on the base structure; two engaging pins provided on the slider member and slidably engaged with the cam openings of the two operation levers respectively; and an actuator member for sliding the slider member relative to the base structure.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates in general to air conditioner units, and more particularly to the air conditioner units for a motor vehicle. 
     2. Description of Related Art 
     In order to clarify the task of the present invention, one known air conditioner unit for a motor vehicle will be described with reference to FIG. 12 of the accompanying drawings, which is shown in Japanese Patent First Provisional Publication 9-20128. 
     The known air conditioner unit “a” comprises a case “b” in which many air passages are defined. The case “b” has a ventilation air blow opening “c”, a defroster air blow opening “d” and a foot air blow opening “e” from which conditioned air is discharged to the outside of the case “b”. 
     A first mode door “f” is arranged at the ventilation air blow opening “c” for adjusting the rate of air blown outward from the opening “c”. That is, the first mode door “f” is pivoted between a close position to close the ventilation air blow opening “c” while opening the air passage directed to the defroster air blow opening “d” and the foot air blow opening “e”, and an open position to open the ventilation air blow opening “c” while closing the air passage directed to the defroster air blow opening “d” and the foot air blow opening “e”. 
     In the air passage directed to the defroster air blow opening “d” and the foot air blow opening “e”, there is arranged a second mode door “g” which can adjust both the rate of air blown outward from the defroster air blow opening “d” and the rate of air blown outward from the foot air blow opening “e”. That is, this second mode door “g” is pivoted between a foot position to open the foot air blow opening “e” while closing the defroster air blow opening “d” and a defroster position to open the defroster air blow opening “d” while closing the foot air blow opening “e”. 
     In the unit case “b”, there is arranged a mode door actuating mechanism “h” which actuates the first and second mode doors “f” and “g” to their desired positions under a given mode. That is, the mode door actuating mechanism “h” comprises a first actuating lever “h 1 ” fixed to a pivot shaft of the first mode door “f”, and a second actuating lever “h 2 ” fixed to a pivot shaft of the second mode door “g”. The mechanism “h” further comprises a rotatable main link “h 4 ” which is engageable with the first actuating lever “h 1 ” and engageable with the second actuating lever “h 2 ” through an intermediate link “h 3 ”. Although not shown in the drawing, the mechanism “h” further comprises a drive cable which pulls the main link “h 4 ” to a desired position under a given mode. 
     The intermediate link “h 3 ” is pivotally connected to the unit case “b” and comprises two arm portions which extend radially outward from its pivoted center portion. One of the arm portions has at its leading end a pin “j” slidably engaged with a cam slot “i” formed in the second actuating lever “h 2 ”, and the other arm portion is formed with a cam slot “k”. The intermediate link “h 3 ” functions to turn the second mode door “g” in a direction opposite to the direction of the first mode door“f”. 
     The main link “h 4 ” comprises three, viz., first, second and third arm portions which extend radially outward from its pivoted center portion. The first arm portion has at its leading end a pin “n” slidably engaged with a cam slot “m” formed in the first actuating lever “h 1 ”, the second arm portion has at its leading end a pin “p” slidably engaged with a cam slot “k” formed in the intermediate link “h 3 ”, and the third arm portion has at its leading end a connecting opening “q” to which the drive cable (not shown) is connected. 
     In the air conditioner unit “a” having the above-mentioned construction, for achieving a ventilation mode of the unit “a”, the main link “h 4 ” is pivoted to a given position by the drive cable, so that the first mode door “f” opens the ventilation air blow opening “c” while closing the air passage directed to the defroster air blow opening “d” and foot air blow opening “e”. While, for achieving a defroster mode of the unit “a”, the first mode door “f” is pivoted to open the air passage directed to the defroster air blow opening “d” and foot air blow opening “e” while closing the ventilation air blow opening “c” and the second mode door “g” is pivoted to open the defroster air blow opening “d” while closing the foot air blow opening “e”. While, for achieving a foot mode of the unit “a”, the first mode door “f” opens the air passage directed to the defroster air blow opening “d” and foot air blow opening “e” while closing the ventilation air blow opening “c”, and the second mode door “g” opens the foot air blow opening “e” while closing the defroster air blow opening “d”. 
     SUMMARY OF THE INVENTION 
     In the above-mentioned known air conditioner unit “a”, the mode door actuating mechanism “h” includes the rotatable main link “h 4 ” and the intermediate link “h 3 ” which are relatively large in size. Due to usage of such larger parts, the layout of the three openings “c”, “d” and “e” and the two mode doors “f” and “g” is highly limited, which causes a difficulty with which the air conditioner unit “a” is made compact in size. 
     It is therefore an object of the present invention to provide an air conditioner unit which can be compact in size due to usage of a compact mode door actuating mechanism. 
     According to a first aspect of the present invention, there is provided an air conditioner unit which comprises a casing having a plurality of air passages defined therein; pivotal mode doors pivotally arranged in the case to provide given operation modes of the air conditioner unit when assuming given angular positions, each mode door having a pivot shaft of which leading end is exposed to the outside of a wall of the case; and a mode door actuating mechanism arranged on the wall of the case to actuate the pivotal mode doors, the mode door actuating mechanism comprising operation levers which are pivotal relative to the wall of the case, each operation lever having a cam opening and being connected to the exposed leading end of the pivot shaft of the corresponding mode door to pivot therewith; a slider member which is slidable relative to the wall of the case; engaging pins provided on the slider member and slidably engaged with the cam openings of the operation levers respectively; and an actuator member for sliding the slider member relative to the wall of the case. 
     According to a second aspect of the present invention, there is provided an air conditioner unit which comprises a case having a plurality of air passages defined therein; at least two pivotal mode doors pivotally arranged in the case to provide various operation modes of the air conditioner unit when assuming given angular positions, each of the mode doors having a pivot shaft of which leading end is exposed to the outside from a wall of the case; and a mode door actuating mechanism attached to an outer surface of the wall of the case to actuate the two pivotal mode doors, the mode door actuating mechanism comprising a base structure adapted to be mounted to the outer surface of the wall; two operation levers pivotally held at respective hub portions thereof by the base structure, each operation lever having a cam opening and being coaxially connected to the leading end of the pivot shaft of corresponding one of the two mode doors; a slider member slidably held on the base structure; two engaging pins provided on the slider member and slidably engaged with the cam openings of the two operation levers respectively; and an actuator member for sliding the slider member relative to the base structure. 
     According to a second aspect of the present invention, there is provided an air conditioner unit which comprises a case having a plurality of air passages defined therein; two pivotal mode doors pivotally arranged in the case to provide various operation modes of the air conditioner unit when assuming given angular positions, each of the mode doors having a pivot shaft of which leading end is exposed to the outside from a wall of the case; and a mode door actuating mechanism detachably attached to an outer surface of the wall of the case to actuate the two pivotal mode doors, the mode door actuating mechanism comprising an elongate housing detachably mounted to the outer surface of the wall, the housing having first and second holding portions at upper and lower walls thereof; first and second operation levers pivotally held at respective hub portions thereby by the first and second holding portions respectively, each operation lever having a generally L-shaped cam opening and being coaxially connected to the leading end of the pivot shaft of corresponding one of the two mode doors; a slider member slidably held in the housing; two engaging pins provided by the slider member and slidably engaged with the L-shaped cam openings of the first and second operation levers respectively; an elongate lid member attached to the housing; and an actuator member for sliding the slider member in the housing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings, in which: 
     FIG. 1 is a side view of an air conditioner unit according to the present invention; 
     FIG. 2 is a sectional view of the air conditioner unit of the invention; 
     FIG. 3 is an exploded view of a mode door actuating mechanism which constitutes an essential portion of the air conditioner unit of the invention; 
     FIG. 4 is an enlarged front view showing a rotation shaft of a mode door; 
     FIG. 5 is an enlarged sectional view showing but partially an operation lever that is about to be engaged with the rotation shaft; 
     FIGS. 6A and 6B are views showing the operation condition of two operation levers and two mode doors under ventilation mode of the air conditioner unit of the invention; 
     FIGS. 7A and 7B are views similar to FIGS. 6A and 6B, but showing the operation condition of the operation levers and mode doors under bi-level mode of the air conditioner unit; 
     FIGS. 8A and 8B are views similar to FIGS. 6A and 6B, but showing the operation condition of the operation levers and mode doors under heat mode of the air conditioner unit; 
     FIGS. 9A and 9B are views similar to FIGS. 6A and 6B, but showing the operation conditions of the operation levers and mode doors under defroster-foot mode of the air conditioner unit; 
     FIGS. 10A and 10B are views similar to FIGS. 6A and 6B, but showing the operation condition of the operation levers and mode doors under defroster mode of the air conditioner unit; 
     FIG. 11 is a perspective of a modification of the mode door actuating mechanism, which can be employed in the air conditioner unit of the present invention; and 
     FIG. 12 is a side view of a known air conditioner unit. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following, the present invention will be described in detail with reference to the accompanying drawings. 
     For ease of understanding, various directional terms such as right, left, upper, lower, rightward, etc., are used in the description. However, such terms are to be understood with respect to only a drawing or drawings on which the corresponding part or parts are illustrated. 
     Referring to FIGS. 1 to  10 B, particularly FIGS. 1 and 2, there is shown an air conditioner unit according to the present invention. 
     As is seen from FIGS. 1 and 2, the air conditioner unit  100 A of the invention comprises a case  2  which is to be mounted below an instrument panel of an associated motor vehicle. The case  2  comprises a front wall  2   a  facing toward an engine room of the vehicle and a rear wall  2   b  facing toward a passenger room. 
     As is seen from FIG. 2, within the case  2 , there is defined a scroll chamber  11  just behind an upper part of the front wall  2   a . That is, in the scroll chamber  11 , there is installed a scirocco fan  3   a . From the scroll chamber  11 , there extends an air passage  4  through which air flow produced by the scirocco fan  3   a  runs downstream. The air passage  4  comprises a down-passage  12  through which the air flow from the fan  3   a  goes down along the front wall  2   a , an up-passage  13  through which the air flow from the down-passage  12  goes up along the rear wall  2   b  and a lower-passage  14  by which the down-passage  12  and the up-passage  13  are connected. The lower passage  14  extends along a bottom wall  2   c  of the case  2 , as shown. 
     As will be described hereinlater, the up-passage  13  comprises a warm air passage  16  in which the heater unit  6  is actually installed, a bypass passage  15  which bypasses the warm air passage  16  and an air mix chamber  18  to which respective downstream ends of the warm air passage  16  and the bypass passage  15  are connected. 
     In the down-passage  12 , there is disposed an evaporator  5  for cooling air flowing therethrough. While, in the up-passage  13 , there is disposed heater unit  6  for heating air that has passed through the evaporator  5 . As shown, upon assembly, the evaporator  5  is inclined by about 10 to 30 degrees relative to a horizontal line having its front (or left) end positioned lower than its rear (or right) end. The air passing through the evaporator  5  runs through the lower-passage  14  along the bottom wall  2   c  of the case  2 . 
     As shown in FIG. 2, in the lower-passage  14 , there are arranged air guide plates  7  for smoothly guiding the air flow toward the up-passage  13 . As shown, the bottom wall  2   c  of the case  2  comprises inclined parts which constitute a lowermost portion with a drain opening  2   c ′. That is, any water condensed on the outer surface of the evaporator  5  flows down along the inclined parts of the bottom wall toward the lowermost portion and discharges into the outside through the drain opening  2   c′.    
     In the case  2 , there is formed an internal wall  2   d  by which the scroll chamber  11  and the up-passage  12  are separated from each other. The inner wall  2   d  has, at a position between the scroll chamber  11  and the down-passage  12 , a depressed part  2   e  that is depressed toward the down-passage  12 . As shown, the heater unit  6  has a left end neatly received in the depressed part  2   e  and is arranged generally in parallel with the evaporator  5  in the down-passage  12 . 
     The up-passage  13  comprises the bypass passage  15  which extends along the rear wall  2   b  of the case  2  bypassing the heater unit  6 . The up-passage further comprises the warm air passage  16  in which the heater unit  6  is actually installed. At an upstream section of the up-passage  13 , there is pivotally installed an air mix door  21  which adjusts an air flow rate between the bypass passage  15  and the warm air passage  16 . That is, the air mix door  21  pivots between a terminal position to close the bypass passage  15 , an intermediate position to partially open both the bypass passage  15  and the warm air passage  16  and another terminal position to close the warm air passage  16 . 
     In the case  2 , there is further formed another internal wall  2   f  which extends around the zone of the scroll chamber  11  to define therebetween a foot air passage  17 . That is, the foot air passage  17  and the up-passage  13  are separated from each other by the internal wall  2   f . A downstream end of the bypass passage  15  and that of the warm air passage  16  are mated to constitute the air mix chamber  18 . 
     A top wall  2   g  of the case  2  is formed with a ventilation air blow opening  31  and a defroster air blow opening  32  from which conditioned air in the air mix chamber  18  is blown outward to respective given outside portions. As shown, the ventilation air blow opening  31  is positioned near an upper portion of the rear wall  2   b  of the case  2 , and the defroster air blow opening  32  is positioned near an upper portion of the front wall  2   a  of the case  2 . An upper part of the inner wall  2   f  which faces the defroster air blow opening  32  is formed with a foot air connecting opening  33  through which the up-passage  13  and the foot air passage  17  are connected. 
     As is understood from FIG. 1, each side wall  2   h  of the case  2  is formed with a foot air blowing opening  34  which forms an end of the foot air passage  17 . In operation, air flowing in the foot air passage  17  is blown into a lower portion of the vehicle cabin from the foot air blowing opening  34 . 
     Referring back to FIG. 2, at the ventilation air blow opening  31 , there is arranged a first mode door  22  which adjusts air flow toward the ventilation air blow opening  31 . The first mode door  22  pivots together with a pivot shaft  22   a  pivotally connected to the case  2  between an open position to close the up-passage  13  directed to the defroster air blow opening  32  and the foot air blowing opening  33  and open the ventilation air blow opening  31  and a close position to open the up-passage  13  and close the ventilation air blow opening  31 . 
     At a branched portion between the defroster air blowing opening  32  and the foot air blowing opening  33 , there is arranged a second mode door  23  which adjusts both air flow toward the defroster air blowing opening  32  and air flow toward the foot air blowing opening  33 . The second mode door  23  pivots together with a pivot shaft  23   a  pivotally connected to the case  2  between a defroster air position to open the defroster air blow opening  32  and close the foot air blow opening  33  and a foot air position to close the defroster air blow opening  32  and open the foot air blow opening  33 . 
     Referring back to FIG. 1, on one of the side walls  2   h  of the case  2 , there is arranged a mode door actuating mechanism  8  which actuates the first and second mode doors  22  and  23  in given manners. That is, as will become apparent as the description proceeds, upon need of a certain operation mode of the air conditioner unit  100 A, the first and second mode doors  22  and  23  are pivoted to desired positions by the mode door actuating mechanism  8 . 
     Referring to FIGS. 1 and 3, there is shown the detail of the mode door actuating mechanism  8  in an exploded manner. 
     The mode door actuating mechanism  8  comprises a housing  70  which is mounted to the side wall  2   h  of the case  2  and a slider member  80  which is slidably received in the housing  70 . The mode door actuating mechanism  8  further comprises a first operation lever  50  which is fixed to the pivot shaft  22   a  of the first mode door  22  and formed with a L-shaped cam opening  51  and a second operation lever  60  which is fixed to the pivot shaft  23   a  of the second mode door  23  and formed with a L-shaped cam opening  61 . These L-shaped cam openings  51  and  61  are applied with a suitable amount of grease. 
     As is seen from FIG. 3, the slider member  80  has at its right end a first engaging pin  81  slidably engaged with the L-shaped cam opening  51  of the first operation lever  50  and at its left end a second engaging pin  82  slidably engaged with the L-shaped cam opening  61  of the second operation lever  60 . Due to presence of grease, the sliding movement of the pin  81  or  82  along the corresponding opening  51  or  61  is smoothly made. 
     The mode door actuating mechanism  8  further comprises an actuating means  90  which can slide the slider member  80  to a desired position shifting the first and second engaging pins  81  and  82  to their desired positions. The actuating means  90  comprises a flexible wire  91  and a flexible guide tube  92  through which the flexible wire  91  slidably moves. One end of the flexible wire  91  is connected to a control knob of a controller (not shown). The other end of the flexible wire  91  is connected to a stud member  85  formed on the slider member  80 . Thus, upon manipulation of the control knob of the controller, the flexible wire is slid in the guide tube  92  thereby to slide the slider member  80  to a desired position. 
     The engagement between the L-shaped cam opening  51  of the first operation lever  50  and the first engaging pin  81  is so made that, under a certain mode of the air conditioning unit  100 , the first operation lever  50  is turned to a position to cause the first mode door  22  to take a certain angular position. The engagement between the L-shaped cam opening  61  and the second engaging pin  82  is so made that, under a certain mode of the air conditioning unit  100 , the second operation lever  60  is turned to a position to cause the second mode door  23  to take a certain angular position. 
     As shown, the first operation lever  50  comprises a lever portion  52  with the cam opening  51  and a cylindrical hub portion  53  coaxially fixed to the pivot shaft  22   a  of the first mode door  22 . That is, the cylindrical hub portion  53  is formed with a non-circular bore  54  into which a non-circular terminal end of the pivot shaft  22   a  is inserted to achieve a united rotation therebetween. 
     The second operation lever  60  comprises a lever portion  62  with the cam opening  61  and a cylindrical hub portion  63  coaxially fixed to the pivot shaft  23   a  of the second mode door  23 . That is, the cylindrical hub portion  63  is formed with a non-circular bore  64  into which a non-circular terminal end of the pivot shaft  23   a  is inserted to achieve a united rotation therebetween. 
     The housing  70  comprises an elongate housing proper  71  which is shaped to receive therein the slider member  80 , and an elongate lid member  72  which is attached to the housing proper  71 . The housing proper  71  comprises an elongate bottom wall  71   a  having a longitudinally extending slot  73 , two elongate side walls raised from side ends of the bottom wall  71   a  and two end walls  71   b  raised from longitudinal ends of the bottom wall  71   a . The slider member  80  has projections  83  slidably engaged with the elongate slot  73  of the bottom wall  71   a  of the housing proper  71 , so that the movement of the slider member  80  in the housing proper  71  is guided by the projections  83  and the slot  73 . 
     The lid member  72  of the housing  70  has a rear surface to which tops of the first and second engaging pins  81  and  82  slidably contact. Due to provision of the lid member  72  attached to the housing proper  71 , the first and second operation levers  50  and  60  are suppressed from dismantling from the respective engaging pins  81  and  82 . 
     The two elongate side walls of the housing proper  71  are formed with two cuts  74  respectively from which the first and second operation levers  50  and  60  are freely projected outward. The upper side wall of the housing proper  71  has at its right part a first holding portion  75  which is formed with a circular opening  75   a  to rotatably support an annular portion  55  of the first operation lever  50 . While, the lower side wall of the housing proper  71  has at its left part a second holding portion  76  which is formed with a circular opening  76   a  to rotatably support an annular portion  65  of the second operation lever  60 . 
     As is seen from FIG. 3, the side wall  2   h  of the case  2  is formed with an oval rib  41  for positioning the housing proper  71  and six resilient holding pieces  42  for holding the housing proper  71 . Each holding piece  42  is formed with a catching hole  43 . 
     Although not shown in FIG. 3, the bottom wall  71   a  of the housing proper  71  is formed at its rear surface with an oval projection which is snugly mated with the oval rib  41  of the side wall  2   h  of the case  2  thereby to achieve the positioning of the housing proper  71  relative to the case  2 . Furthermore, the upper and lower side walls of the housing proper  71  are formed with projections  78  which are mated with the catching holes  43  of the above-mentioned holding pieces  42  in a snap action manner. As shown, each projection  78  is in the shape of wedge for assuring the snap action connection of the housing proper  71  relative to the case  2 . 
     As shown, the slider member  80  is formed at its generally middle part with an oval projection  84  from which the stud member  85  projects. The elongate lid member  72  of the housing proper  71  is formed with an elongate slot  72   a  with which the stud member  85  is slidably engaged. As has been described hereinabove, the flexible wire  91  is connected to the stud member  85 . The lid member  72  is formed with a clamp portion  72   b  by which the guide tube  92  for the flexible wire  91  is clamped. 
     The housing  70 , the slider member  80 , the first and second operation levers  50  and  60  are assembled in the above-mentioned manner to constitute a unit. The unit is mounted to the side wall  2   h  of the case  2  in the above-mentioned manner. In the unit, the slider member  80  is slidably installed in the housing  70 , and the first operation lever  50  is rotatably held by the first holding portion  75  having the first engaging pin  81  of the slider member  80  slidably engaged with the L-shaped cam opening  51  of the first operation lever  50 . Furthermore, in the unit, the second operation lever  60  is rotatably held by the second holding portion  76  having the second engaging pin  82  of the slider member  80  slidably engaged with the L-shaped cam opening  61  of the second operation lever  60 . 
     Referring to FIGS. 4 and 5, there is shown the detail of the connection between the first operation lever  50  (or second operation lever  60 ) and the pivot shaft  22   a  of the first mode door  22  (or the pivot shaft  23   a  of the second mode door  23 ). That is, FIG. 4 is an enlarged end view of the pivot shaft  22   a  (or  23   a ), and FIG. 5 is an axially sectional view of the end of the pivot shaft  22   a  (or  23   a ) mated with the operation lever  50  (or  60 ). 
     As is seen from FIGS. 3,  4  and  5 , the pivot shafts  22   a  and  23   a  of the first and second operation levers  50  and  60  have each an axially extending groove  22   b  or  23   b . As is best seen from FIGS. 3 and 5, two resilient arms  44  and  45  are projected from the side wall  2   f  of the case  2 , each having a latching pawl having a sloped lower surface  46  as is seen from FIG.  5 . As is seen from FIG. 3, before complete assembly of the mode door actuating mechanism  8 , the latching pawls of the resilient arms  44  and  45  are kept engaged with the grooves  22   b  and  23   b  respectively for keeping the corresponding mode doors  22  and  23  at their given angular positions. 
     As is seen from FIG. 5, the annular portion  55  or  65  of the first or second operation lever  50  or  60  is formed with a conical outer surface  56  or  66 . As is seen from this drawing, the conical outer surface  56  or  66  is constructed and shaped to incorporate with the sloped lower surface  46  of the latching pawl of the resilient arm  44  or  45  of the side wall  2   h  of the case  2 . 
     It is to be noted that the conical outer surface  56  or  66  serves as a canceling means for canceling the latched engagement between the latching pawl of the resilient arm  44  or  45  and the groove  22   b  or  23   b . That is, as is seen from FIG. 5, when the first or second operation lever  50  or  60  is thrust onto and about to be engaged the corresponding pivot shaft  22   a  or  23   a  of the first or second mode door  22  or  23 , the conical outer surface  56  or  66  gets under the latching pawl of the resilient arm  44  or  45  and thus raises the same thereby to cancel the latched engagement between the latching pawl of the resilient arm  44  or  45  and the groove  22   b  or  23   b . With this, the first or second operation lever  50  or  60  becomes united with the pivot shaft  22   a  or  23   a  of the first or second mode door  22  or  23  to pivot together therewith. 
     As is seen from FIG. 4, the end of the pivot shaft  22   a  or  23   a  of the first or second mode door  22  or  23  is formed with spaced cuts  22   c  or  23   c  between which the groove  22   b  or  23   b  is defined with interposition of walls (no numerals) therebetween. These cuts  22   c  and  23   c  serve as positioning means for positioning the first or second operation lever  50  or  60  relative to the first or second mode door  22  or  23 . 
     In FIGS. 6A and 6B, there is shown an operation condition of the operation levers  50  and  60  and mode doors  22  and  23  under VENTILATION mode. As is seen from FIG. 6A, under this mode, the first engaging pin  81  of the slider member  80  is at the inflection part of the L-shaped cam opening  51  of the first operation lever  50 , and the second engaging pin  82  is at a left end of the upper part of the L-shaped cam opening  61  of the second operation lever  60 . As shown, in this mode, the upper part of the L-shaped cam opening  61  is arranged in parallel with the slider member  80 . As is seen from FIG. 6B, under the VENTILATION mode, the first mode door  22  takes an open position, that is a position to close the passage directed from the up-passage  13  toward both the defroster air blow opening  32  and the foot air blow opening  33  and open the ventilation air blow opening  31 , and the second mode door  23  takes a foot air position closing the defroster air blow opening  32  while opening the foot air blow opening  33 . Thus, under this VENTILATION mode, conditioned air flowing in the up-passage  13  is blown into the vehicle cabin through only the ventilation air blow opening  31  as is indicated by the arrow. 
     In FIGS. 7A and 72B, there is shown the operation condition under BI-LEVEL mode. As is seen from FIG. 7A, for achieving this mode, the slider member  80  is somewhat shifted rightward in the drawing as compared with the case of the above-mentioned VENTILATION mode. Accordingly, the first operation lever  50  is pushed rightward by the first engaging pin  81  and thus pivoted slightly in a counterclockwise direction, while the second operation lever  60  is left unmoved because of inoperative movement of the second engaging pin  82  in the upper horizontal part of the L-shaped cam opening  61  of the second operation is lever  60 . Accordingly, as is seen from FIG. 7B, under the BI-LEVEL mode, the first mode door  22  takes a half-open position partially opening the passage directed toward the foot air blow opening  33  and the ventilation air blow opening  31 . Of course, the second mode door  23  is kept in the foot air position. Thus, under this BI-LEVEL mode, conditioned air flowing in the up-passage  13  is blown into the vehicle cabin from both the ventilation air blow opening  31  and the foot air blow opening  33  as is indicated by the arrows. 
     In FIGS. 8A and 8B, there is shown the operation condition under HEAT mode. As is seen from FIG. 8A, for achieving this mode, the slider member  80  is further shifted rightward in the drawing. Accordingly, the first operation lever  50  is further pushed rightward by the first engaging pin  81  and thus further pivoted counterclockwise. As shown, upon achieving this mode, the lower part of the L-shaped cam opening  51  of the lever  50  becomes in parallel with the slider member  80 . For achieving this HEAT mode, the second operation lever  60  is pushed rightly by the second engaging pin  82  and thus pivoted slightly in a clockwise direction in the drawing. Upon achieving this mode, the second engaging pin  82  comes to the inflection part of the L-shaped cam opening  61  of the second operation lever  60 , as shown. Accordingly, as is seen from FIG. 8B, under the HEAT mode, the first mode door  22  takes a close position closing the ventilation air blow opening  31  while opening the passage directed toward both the defroster air blow opening  32  and foot air blow opening  33 , and the second mode door  23  takes a first half-open position partially opening both the defroster air blow opening  32  and the foot air blow opening  33 . As shown, in the first half-open position of the second mode door  23 , the open degree of the foot air blow opening  33  is larger than that of the defroster air blow opening  32 . Under this HEAT mode, conditioned air flowing in the up-passage  13  is blown into the vehicle cabin from both the defroster air blow opening  32  and the foot air blow opening  33 , as is indicated by the arrows. Of course, the amount of air from the foot air blow opening  33  is larger than that from the defroster air blow opening  32 . 
     In FIGS. 9A and 9B, there is shown the operation condition under DEFROSTER-FOOT mode. As is seen from FIG. 9A, for achieving this mode, the slider member  80  is further shifted rightward in the drawing. During this shifting, the first engaging pin  81  slides without effect in the lower part of the L-shaped cam opening  51  of the first operation lever  50 , and thus the first operation lever  50  is kept unmoved. However, due to the further rightward shifting of the slider member  80 , the second engaging pin  82  pushes the second operation lever  60  rightward and thus the second operation lever  60  is further pivoted clockwise. Accordingly, as is seen from FIG. 9B, under the DEFROSTER-FOOT mode, the first mode door  22  keeps the close position closing the ventilation air blow opening  31  while opening the passage directed toward both the defroster air blow opening  32  and the foot air blow opening  33 , and the second mode door  23  takes a second half-open position partially opening both the defroster air blow opening  32  and the foot air blow opening  33 . As shown, in the second half-open position of the second mode door  23 , the open degree of the defroster air blow opening  32  is larger than that of the foot air blow opening  33 . Thus, under this DEFROSTER-FOOT mode, a larger amount of conditioned air is blown into the vehicle cabin from the defroster air blow opening  32 , and a smaller amount of conditioned air is blown into the vehicle cabin from the foot air blow opening  33 . 
     In FIGS. 10A and 10B, there is shown the operation condition under DEFROSTER mode. As is seen from FIG. 10A, for achieving this mode, the slider member  80  is further shifted rightward in the drawing. During this shifting, the first engaging pin  81  still slides without effect in the lower part of the of the L-shaped cam opening  51  of the first operation lever  50 , and thus the first operation lever  50  is kept unmoved. However, due to the further rightward movement of the slider member  80 , the second engaging pin  82  further pushes the second operation lever  60  rightward and thus the second operation lever  60  is pivoted further in a clockwise direction in the drawing. Accordingly, as is seen from FIG. 10B, under the DEFROSTER mode, the first mode door  22  keeps the close position closing the ventilation air blow opening  31  while opening the passage directed toward both the defroster air blow opening  32  and the foot air blow opening  33 , and the second mode door  23  takes a defroster air position opening the defroster air blow opening  32  while closing the foot air blow opening  33 . Thus, under this DEFROSTER mode, conditioned air flowing in the up-passage  13  is blown into the vehicle cabin from only the defroster air blow opening  32  as is indicated by the arrow. 
     As is understood from the above description, when the slider member  80  (see FIG. 3) is pulled or pushed by the flexible wire  91  upon manipulation of the control knob of the controller (not shown) by a driver or passenger, the first and second mode doors  22  and  23  are pivoted to their given angular positions for achieving a desired mode of the air conditioning unit  100 . 
     In following, various advantages of the present invention will be described with the aid of the drawings. 
     First, the pivot shafts  22   a  and  23   a  of the first and second mode doors  22  and  23  are arranged at opposite sides with respect to the slider member  80 . Due to this arrangement, the sliding movement of the slider member  80  induces pivoting of the first and second mode doors  22  and  23  in opposite directions about their pivot shafts  22   a  and  23   a . That is, the above-mentioned five air distribution modes, that is, VENTILATION, BI-LEVEL, HEAT, DEFROSTER-FOOT and DEFROSTER modes, can be readily provided by a compact construction which includes the first and second mode doors  22  and  23 . Furthermore, the mode door actuating mechanism  8  for actuating the two mode doors  22  and  23  is made compact in size. In other words, in the present invention, there is no need of using bulky members such as the rotatable main link “h 4 ” and intermediate link “h 3 ” used in the known air conditioner unit of FIG.  12 . Thus, the air distribution unit including the two mode doors  22  and  23  and the mode door actuating mechanism  8  can be made compact, and thus, the entire construction of the air conditioner unit  100  can be made compact in size. 
     Second, as is described hereinabove, the mode door actuating mechanism  8  can be assembled as a unit. Thus, mounting the mechanism  8  to the case  2  is easily and speedily carried out which brings about reduction in cost of the air conditioner unit  100 . 
     Third, due to provision of the positioning rib  41  and holding pieces  42  by the case  2 , the mounting of the mode door actuating mechanism  8  to the case  2  is further facilitated. 
     Fourth, the air conditioner unit  100  is arranged so that the rear wall  2   b  (see FIG. 1) thereof is positioned near a front panel of an instrument panel on which the control knob of the controller is mounted. In the invention, the clamp portion  72   b  (see FIG. 1) is positioned on the side panel, which facilitates the arrangement of the flexible wire  91  extending between the control knob and the clamp portion  72   b . Furthermore, such positioning provides the flexible wire  91  with a suitable length smoothly transmitting the operation force of the control knob to the slider member  80 . This advantage will be clarified from the following supplementary explanation. That is, if the clamp portion  72   b  (see FIG. 3) is provided on the rear wall  2   b , the distance between the clamp portion  72   b  and the control knob becomes very short, which makes arrangement of the wiring ( 91 ) therebetween very difficult. Furthermore, in assembly, due to the short distance, the flexible wire  91  is curved with a small radius of curvature, which causes a larger operation force needed by the control knob for moving the wire  91 . While, if the clamp portion  72   b  is provided on or near the front wall  2   a  of the case  2 , the flexible wire  91  and the guide tube  92  need longer length which causes increase in cost of the air conditioner unit  100 . 
     Fifth, due to provision of the resilient arms  44  and  45  of the case  2  which are engageable with the grooves  22   b  and  23   b  (see FIG. 3) of the pivot shafts  22   a  and  23   a  to achieve a latched engagement therebetween, the first and second mode doors  22  and  23  can be fixed to the case  2 . Thus, mounting of the mode door actuating mechanism  8  to the side wall  2   h  of the case  2  is readily achieved. More specifically, mounting of the first and second operation lever  50  and  60  to the pivot shafts  22   a  and  23   a  of the doors  22  and  23  is readily carried out. 
     Sixth, due to provision of the conical annular portions  55  and  65  by the first and second operation levers  50  and  60 , thrusting the hub portions  53  and  63  of these levers  50  and  60  onto the ends of the pivot shafts  22   a  and  23   a  automatically cancels the latched engagement between the resilient arms  44  and  45  and the grooves  22   b  and  23   b . This facilitates the mounting of the levers  50  and  60  to the pivot shafts  22   a  and  23   a.    
     Seventh, due to provision of the spaced cuts  22   c  and  23   c  by the pivot shafts  22   a  and  23   a , positioning of the first and second operation levers  50  and  60  relative to the first and second mode doors  22  and  23  is established upon coupling of the hub portions  53  and  63  with the pivot shafts  22   a  and  23   a.    
     Referring to FIG. 11, there is shown a modification  8 ′ of the above-mentioned mode door actuating mechanism  8 . 
     In this modification, both the first and second operation levers  50  and  60  are entirely concealed in the housing, as will become apparent from the following description. 
     As is seen from FIG. 11, the modified mechanism  8 ′ comprises a housing  170  which is to be mounted to the side wall  2   h  of the case  2  in the above-mentioned manner. As shown, the housing  170  is formed with both first and second expanded portions  171  and  172  for spacedly receiving therein the lever portions  52  and  62  of the first and second operation levers  50  and  60  respectively. A suitable amount of grease is applied to the L-shaped cam openings  51  and  61  for smoothing the movement of the first and second engaging pins  81  and  82  in and along the openings  51  and  61 . 
     In this modification, the work for mounting the mechanism  8 ′ to the side wall  2   h  of the case  2  is readily and much safely achieved because the lever portions  52  and  62  applied with grease are entirely installed in the housing  170 . 
     In the foregoing description, the mode door actuating mechanism  8  or  8 ′ is described to have the housing  70  or  170 . However, if desired, such housing  70  or  170  may be integrally formed on the side wall  2   h  of the case  2 . 
     The entire contents of Japanese Patent Application 2000-225887 (filed Jul. 26, 2000) are incorporated herein by reference. 
     Although the invention has been described above with reference to the embodiment of the invention, the invention is not limited to such embodiment as described above. Various modifications and variations of such embodiment may be carried out by those skilled in the art, in light of the above description.