Patent Publication Number: US-2020298660-A1

Title: Blow unit of air conditioner for vehicle

Description:
BLOWER UNIT OF AIR CONDITIONER FOR VEHICLE 
     This application claims priority from Korean Patent Application No. 10-2018-0156646 filed on Dec. 7, 2018. The entire contents of this application is incorporated herein by reference in its entirety. 
     The patent or application file contains two drawings executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a blower unit of an air conditioner for a vehicle, and more particularly, to a blower unit of a two-layered air conditioner for a vehicle, which can selectively inhale indoor air or outdoor air into an air-conditioning case, thereby securing defogging performance and maintaining high heating performance during heating. 
     Background Art 
     In general, an air conditioner for a vehicle is a device for heating or cooling the interior of the vehicle by introducing outdoor air to the interior of the vehicle or circulating indoor air to heat or cool. The air conditioner for a vehicle includes a blower unit for introducing and blowing indoor air or outdoor air, and an air-conditioning unit for conditioning the air blown from the blower unit and discharging the air to the interior of the vehicle. 
     Especially, a two-layered air conditioner has been developed in order to secure defogging performance and maintain high heating performance during heating. Cold outdoor air of low humidity is effective to defrost windows during traveling in a heating state, but it results in lowering indoor temperature. 
     The two-layered air conditioner realizes a two-layer air flow of indoor air and outdoor air to supply outdoor air to an upper part of a vehicle and circulate indoor air to a lower part of the vehicle in order to defog in the heating state, thereby effectively defrosting using fresh outdoor air of low humidity supplied to the upper part, offering fresh air to passengers, and maintaining high heating performance by supplying warm indoor air to the lower part. 
       FIG. 1  is a sectional view showing an air-conditioning unit of a conventional two-layered air conditioner for a vehicle. Referring to  FIG. 1 , the air-conditioning unit  5  of the conventional two-layered air conditioner for a vehicle includes an air-conditioning case  10 . The air-conditioning case  10  includes an air passageway of a predetermined shape formed therein, and the air passageway is partitioned into an upper passageway  21  and a lower passageway  22  by a separation wall  23 . The air-conditioning case  10  has a plurality of air outlets formed at an exit of the air-conditioning case  10 . The air outlets include a defrost vent  16 , a face vent  17 , a front seat floor vent  18 , and a rear seat floor vent  19 . 
     A blower unit is combined with an air inlet  15  of the air-conditioning case  10 , and an evaporator  2  and a heater core  3  are disposed in the air passageway of the air-conditioning case  10  to be spaced apart from each other at a predetermined interval. Outdoor air is introduced into the upper passageway  21  and flows in the upper passageway  21 , and indoor air is introduced into the lower passageway  22  and flows in the lower passageway  22 . A first temp door  11  for adjusting an amount of air passing the heater core  3  and an amount of air bypassing the heater core  3  is disposed in the upper passageway  21 . A second temp door  12  for adjusting the amount of the air passing the heater core  3  and the amount of the air bypassing the heater core  3  is disposed in the lower passageway  22 . 
     A defrost door  24  and a face door  25  are respectively disposed at the air outlets in order to adjust an amount of air discharged to the defrost vent  16  and the face vent  17 . A floor door  26  for adjusting an amount of air discharged to the front seat floor vent  18  and a rear seat mode door  27  for adjusting an amount of air discharged to the rear seat floor vent  19  are respectively disposed at the air outlets. A bypass door  28  for controlling communication between the upper passageway  21  and the lower passageway  22  is disposed so that the indoor air of the lower passageway  22  can flow to the upper passageway  21 . 
       FIG. 2  is a sectional view showing a blower unit of the conventional two-layered air conditioner for a vehicle. Referring to  FIG. 2 , the blower unit  7  of the conventional two-layered air conditioner for a vehicle includes a blower case, a blower wheel, a blower motor  76 , and an air filter  75 . 
     The blower case includes an intake case  82  and a scroll case  70  joined to a lower portion of the intake case  82 . The intake case  82  includes an indoor air inlet  72  for introducing indoor air and an outdoor air inlet  71  for introducing outdoor air. The indoor air inlet  72  and the outdoor air inlet  71  are formed at an upper portion of the intake case  82 . An indoor air door  74  adjusts the degree of opening of the indoor air inlet  72 , and an outdoor air door  73  adjusts the degree of opening of the outdoor air inlet  71 . 
     The blower wheel and the blower motor  76  are disposed in the scroll case  70  and send the air introduced through the indoor air inlet  72  and the outdoor air inlet  71  to the interior of the vehicle. The air filter  75  is disposed at the upstream side of the blower wheel in an air flow direction. The air passageway of the scroll case  70  is divided into a first air passageway  79 , in which outdoor air flows, and a second air passageway  80 , in which indoor air flows, by a separation wall  81 . The blower wheel includes a first blower wheel  77  disposed in the first air passageway  79  and a second blower wheel  78  disposed in the second air passageway  80 . 
     The outdoor air introduced into the outdoor air inlet  71  flows to the first air passageway  79  through a first inlet  86  and is blown to the upper passageway  21  of the air-conditioning unit  5 . Moreover, the indoor air introduced into the indoor air inlet  72  flows to the second air passageway  80  through the second inlet  85  and is blown to the lower passageway  22  of the air-conditioning unit  5 . 
       FIG. 3  is a perspective view showing the scroll case of the blower unit of the conventional two-layered air conditioner for a vehicle,  FIG. 4  is a perspective view showing a state where the scroll case of the blower unit of the conventional two-layered air conditioner for a vehicle is separated, and  FIG. 5  is a plan view showing the scroll case of the blower unit of the conventional two-layered air conditioner for a vehicle. 
     Referring to  FIGS. 3 to 5 , the scroll case  70  includes an upper scroll case  83 , and a lower scroll case  84  joined to a lower portion of the upper scroll case  83 . The first air passageway  79  is formed in the scroll case  83 , and the first blower wheel  77  is disposed in the upper scroll case  83 . The second air passageway  80  is formed in the lower scroll case  84 , and the second blower wheel  78  is disposed in the lower scroll case  84 . 
     The upper scroll case  83  and the lower scroll case  84  have a spiral form of which a diameter gets larger on the basis of the blower wheels. That is, the scroll case is formed by a predetermined scroll expansion angle applied along the “11” line indicated by the chain line of  FIG. 5  from the “cut off” point which is a start point of the spiral form. 
     The scroll case  70  of the blower unit of the conventional air conditioner for a vehicle has different ventilation resistance between the passageway (the first air passageway) of the upper scroll case  83  and the passageway (the second air passageway) of the lower scroll case  84 , but the conventional air conditioner for a vehicle has a disadvantage in that air-conditioning performance since the same scroll expansion angle is applied to the upper scroll case  83  and the lower scroll case  84 . 
     In the meantime,  FIG. 6  is a front view showing the scroll case of the blower unit of the conventional two-layered air conditioner for a vehicle is separated. Referring to  FIG. 6 , the upper scroll case  83  and the lower scroll case  84  have scroll development parts that the air passageways are expanded downstream toward the air outlets in the air flow direction. The scroll development parts of the conventional upper scroll case  83  and lower scroll case  84  have the same start point. That is, a length (a) from the start point of the scroll development part of the upper scroll case to the air outlets is equal to a length (b) from the start point of the scroll development part of the lower scroll case to the air outlets. 
     The scroll case  70  of the blower unit of the conventional air conditioner for a vehicle has different ventilation resistance between the passageway of the upper scroll case  83  and the passageway of the lower scroll case  84 , but the conventional air conditioner for a vehicle has a disadvantage in that air-conditioning performance since the scroll development parts of the upper scroll case  83  and the lower scroll case  84  have the same start point. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior arts, and it is an object of the present invention to provide a blower unit of an air conditioner for a vehicle, which can enhance air-conditioning performance through uniform upper and lower pressure control since compensating and supplementing different air resistances between an upper scroll case and a lower scroll case. 
     To accomplish the above object, according to the present invention, there is provided a blower unit of a two-layered air conditioner for a vehicle, which separates and blows indoor air and outdoor air, including: a first scroll in which a first blower wheel is disposed and a first air passageway is formed; and a second scroll arranged below the first scroll, and having a second blower wheel and a second air passageway, wherein a diameter of the second blower wheel and a diameter of the first blower wheel are different from each other. 
     Moreover, the diameter of the second blower wheel is larger than that of the first blower wheel. 
     Furthermore, a scroll expansion angle of the first scroll and a scroll expansion angle of the second scroll are different from each other. 
     Additionally, the scroll expansion angle of the second scroll is larger than that of the first scroll. 
     In addition, a height of the first blower wheel is greater than a height of the second blower wheel. 
     Moreover, the scroll expansion angles of the first scroll and the second scroll are formed in such a way that a distance between the center of the blower wheel and the outer wall surface gets farther from a “cut off” point. 
     Furthermore, the scroll expansion angle of the first scroll is 5.2° to 5.8°, and the scroll expansion angle of the second scroll is 6.0° to 6.6°. 
     In another aspect of the present invention, there is provided a blower unit of a two-layered air conditioner for a vehicle, which separates and blows indoor air and outdoor air, including: a first scroll in which a first blower wheel is disposed and a first air passageway is formed; and a second scroll arranged below the first scroll, and having a second blower wheel and a second air passageway, wherein a start point of a scroll development part of the first scroll and a start point of a scroll development part of the second scroll are different from each other. 
     Additionally, the start point of the scroll development part of the first scroll in the air flow direction is formed to be further back than the start point of the scroll development part of the second scroll. 
     In addition, the air passageway of the second scroll is more complicated than the air passageway of the first scroll. 
     Moreover, the air passageway of the second scroll is larger in air resistance than the air passageway of the first scroll. 
     Furthermore, the first scroll includes an upper scroll case, and the second scroll includes a lower scroll case joined below the upper scroll case. The upper scroll case receives the air which is introduced into the blower unit and directly flows downwards, and the lower scroll case receives the air which is introduced into the blower unit, flows downwards and bypasses and flows upwards. 
     The blower unit of the air conditioner for a vehicle according to the present invention can enhance air-conditioning performance, make speed distribution uniform, and improve a noise problem through uniform upper and lower pressure control. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments of the invention in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a sectional view showing an air-conditioning unit of a conventional two-layered air conditioner for a vehicle; 
         FIG. 2  is a sectional view showing a blower unit of the conventional two-layered air conditioner for a vehicle; 
         FIG. 3  is a perspective view showing a scroll case of the blower unit of the conventional two-layered air conditioner for a vehicle; 
         FIG. 4  is a perspective view showing a state where the scroll case of the blower unit of the conventional two-layered air conditioner for a vehicle is separated; 
         FIG. 5  is a plan view showing the scroll case of the blower unit of the conventional two-layered air conditioner for a vehicle; 
         FIG. 6  is a front view showing the scroll case of the blower unit of the conventional two-layered air conditioner for a vehicle is separated; 
         FIG. 7  is a sectional view showing an air conditioning unit of a two-layered air conditioner for a vehicle according to an embodiment of the present invention; 
         FIG. 8  is a sectional view showing a blower unit of the two-layered air conditioner for a vehicle according to the embodiment of the present invention; 
         FIG. 9  is a perspective view showing a scroll case of the two-layered air conditioner for a vehicle according to the embodiment of the present invention; 
         FIG. 10  is a perspective view showing a state where the scroll case is separated; 
         FIG. 11  is a plan view showing the scroll case of the two-layered air conditioner for a vehicle according to the embodiment of the present invention; 
         FIG. 12  is a view showing a blower wheel of the two-layered air conditioner for a vehicle according to the embodiment of the present invention; 
         FIG. 13  is a graph for explaining a scroll expansion angle of the two-layered air conditioner for a vehicle according to the embodiment of the present invention; 
         FIG. 14  is a graph for explaining an air-conditioning performance improvement result according to the scroll expansion angle; 
         FIG. 15A  is a graph for explaining an air-conditioning performance improvement result according to the scroll expansion angle, showing a non-uniform speed distribution. 
         FIG. 15B  is a graph for explaining an air-conditioning performance improvement result according to the scroll expansion angle, showing a relatively uniform speed distribution. 
         FIG. 16  is a front view showing a state where the scroll case is separated; and 
         FIG. 17A  is a graph for explaining an air-conditioning performance improvement result according to a start point of a scroll development part according to the embodiment of the present invention, showing a non-uniform speed distribution. 
         FIG. 17B  is a graph for explaining an air-conditioning performance improvement result according to a start point of a scroll development part according to the embodiment of the present invention, showing a relatively uniform speed distribution. 
         FIG. 18  is a graph for explaining an air-conditioning performance improvement result according to a start point of a scroll development part according to the embodiment of the present invention. 
         FIG. 19  is a graph for explaining an air-conditioning performance improvement result according to a start point of a scroll development part according to the embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Hereinafter, with reference to the attached drawings, a technical structure of a blower unit of an air conditioner for a vehicle according to a preferred embodiment of the present invention will be described in detail. 
     A two-layered air conditioner for a vehicle according to an embodiment of the present invention is a device for heating or cooling the interior of the vehicle by introducing outdoor air into the interior of the vehicle or circulating indoor air, and includes a blower unit for introducing and blowing indoor air or outdoor air, and an air-conditioning unit for conditioning the air blown from the blower unit and discharging the air to the interior of the vehicle. The two-layered air conditioner for a vehicle divides and blows the indoor air and the outdoor air in order to secure defogging performance and maintain high heating performance during heating. 
       FIG. 7  is a sectional view showing the air conditioning unit of the two-layered air conditioner for a vehicle according to the embodiment of the present invention. Referring to  FIG. 7 , the air-conditioning unit  100  of the two-layered air conditioner for a vehicle according to the embodiment of the present invention includes an air-conditioning case  110 . The air-conditioning case  110  includes an air passageway of a predetermined form therein, and the air passageway is partitioned into an upper passageway  121  and a lower passageway  122  by a separation wall  123 . The air-conditioning case  110  has a plurality of air outlets formed at an exit thereof. The air outlets include a defrost vent  116 , a face vent  117 , a front seat floor vent  118 , and a rear seat floor vent  119 . 
     The blower unit  110  is combined with an air inlet  115  of the air-conditioning case  110 , and an evaporator  102  and a heater core  103  are disposed in the air passageway of the air-conditioning case  110  to be spaced apart from each other at a predetermined interval. Outdoor air is introduced into the upper passageway  121  and flows in the upper passageway  121 , and indoor air is introduced into the lower passageway  122  and flows in the lower passageway  122 . A first temp door  111  for adjusting an amount of air passing the heater core  103  and an amount of air bypassing the heater core  103  is disposed in the upper passageway  121 . A second temp door  112  for adjusting the amount of the air passing the heater core  103  and the amount of the air bypassing the heater core  103  is disposed in the lower passageway  122 . 
     A defrost door  124  and a face door  125  are respectively disposed at the air outlets in order to adjust an amount of air discharged to the defrost vent  116  and the face vent  117 . A floor door  126  for adjusting an amount of air discharged to the front seat floor vent  118  and a rear seat mode door  127  for adjusting an amount of air discharged to the rear seat floor vent  119  are respectively disposed at the air outlets. A bypass door  128  for controlling communication between the upper passageway  121  and the lower passageway  122  is disposed so that the indoor air of the lower passageway  122  can flow to the upper passageway  121 . 
       FIG. 8  is a sectional view showing the blower unit of the two-layered air conditioner for a vehicle according to the embodiment of the present invention. Referring to  FIG. 8 , the blower unit  200  of the two-layered air conditioner for a vehicle according to the embodiment of the present invention includes a blower case, a blower wheel, a blower motor  276 , and an air filter  275 . 
     The blower case includes an intake case  282 , and a scroll case  270  joined to a lower portion of the intake case  282 . The intake case  282  includes an indoor air inlet  272  for introducing indoor air and an outdoor air inlet  271  for introducing outdoor air. The indoor air inlet  272  and the outdoor air inlet  271  are formed at an upper portion of the intake case  282 . An indoor air door  274  adjusts the degree of opening of the indoor air inlet  272 , and an outdoor air door  273  adjusts the degree of opening of the outdoor air inlet  271 . 
     The blower wheel and the blower motor  276  are disposed in the scroll case  270  and send the air introduced through the indoor air inlet  272  and the outdoor air inlet  271  to the interior of the vehicle. The air filter  275  is disposed at the upstream side of the blower wheel in an air flow direction. The air passageway of the scroll case  270  is divided into a first air passageway  279 , in which outdoor air flows, and a second air passageway  280 , in which indoor air flows, by a separation wall  281 . The blower wheel includes a first blower wheel  277  disposed in the first air passageway  279  and a second blower wheel  278  disposed in the second air passageway  280 . 
     The outdoor air introduced into the outdoor air inlet  271  flows to the first air passageway  279  through a first inlet  286  and is blown to the upper passageway  121  of the air-conditioning unit  100 . Moreover, the indoor air introduced into the indoor air inlet  272  flows to the second air passageway  280  through the second inlet  285  and is blown to the lower passageway  122  of the air-conditioning unit  100 . 
       FIG. 9  is a perspective view showing a scroll case of the two-layered air conditioner for a vehicle according to the embodiment of the present invention,  FIG. 10  is a perspective view showing a state where the scroll case is separated, and  FIG. 11  is a plan view showing the scroll case of the two-layered air conditioner for a vehicle according to the embodiment of the present invention. 
     Referring to  FIGS. 9 to 11 , the scroll case  270  includes a first scroll and a second scroll. The first scroll includes an upper scroll case  283 , and the second scroll includes a lower scroll case  284 . The lower scroll case  284  is joined to a lower portion of the upper scroll case  283 . The first air passageway  279  is formed in the upper scroll case  283 , and the first blower wheel  277  is disposed in the upper scroll case  283 . The second air passageway  280  is formed in the lower scroll case  284 , and the second blower wheel  278  is disposed in the lower scroll case  284 . 
     The air passageway of the second scroll, namely, the second air passageway  280  is more complicated than the air passageway of the first scroll, namely, the first air passageway  279 . That is, the second air passageway  280  is greater in air resistance than the first air passageway  279 . In detail, the upper scroll case  283  receives the air which is introduced into the blower unit and directly flows downwards. Moreover, the lower scroll case  284  receives the air, which is introduced into the blower unit, flows downwards and bypasses and flows upwards. 
     In more detail, the outdoor air introduced through the outdoor air inlet  271  passes the air filter  275  to be filtered, moves downwards, and then, flows into the first scroll case  283  through the first inlet  286 . The outdoor air flowing into the first air passageway  279 , which has flown in a vertical direction, flows in a radial direction by rotation of the first blower wheel  277 , and then, flows into the air-conditioning unit  100  through a scroll development duct of the first scroll case  283 . 
     Furthermore, the indoor air introduced through the indoor air inlet  273  passes the air filter  275  to be filtered, moves downwards, and continuously moves downwards along the outer face of a side wall of the scroll case through the second inlet  285 , and then, makes a U-turn to move upwards. After that, the indoor air moves into the second scroll case  284 . The outdoor air flowing into the second air passageway  280 , which has flown in the vertical direction, flows in the radial direction by rotation of the second blower wheel  278 , and then, flows into the air-conditioning unit  100  through a scroll development duct of the second scroll case  284 . 
     The upper scroll case  283  and the lower scroll case  284  have a spiral form of which a diameter gets larger on the basis of the blower wheels. That is, the first scroll case and the second scroll are is formed by a predetermined scroll expansion angle applied along a path of an outer wall surface of the scroll case from the “cut off” point which is a start point of the spiral form. The expansion angles of the first scroll and the second scroll are formed in such a way that a distance between the center of the blower wheel and the outer wall surface gets farther from the “cut off” point which is the start point. 
     Especially, the scroll expansion angle of the first scroll and the scroll expansion angle of the second scroll are different from each other. Preferably, the expansion angle of the second scroll is larger than the expansion angle of the first scroll. It is preferable that the expansion angle of the first scroll be 5.2° to 5.8° and the expansion angle of the second scroll be 6.0° to 6.6°. More preferably, the expansion angle of the first scroll is 5.5° and the expansion angle of the second scroll is 6.3°. 
     If the expansion angle of the lower scroll case  284  is larger than the expansion angle of the upper scroll case  283 , as shown in  FIGS. 9 and 11 , a scroll development duct upper surface  287  of the lower scroll case  284  protrudes outwards from the upper scroll case  283  in a state where the upper scroll case  283  and the lower scroll case  284  are combined with each other. 
       FIG. 12  is a view showing the blower wheel of the two-layered air conditioner for a vehicle according to the embodiment of the present invention. Referring to  FIG. 12 , a diameter (d 2 ) of the second blower wheel  278  and a diameter (d 2 ) of the second blower wheel  278  are different from each other. Preferably, the diameter (d 2 ) of the second blower wheel  278  is larger than the diameter (d 1 ) of the first blower wheel  277 . Because the second scroll (lower scroll) is more complicated and narrower in an introduction path of air than the first scroll (upper scroll), the second scroll is high in pressure and resistance and is deteriorated in air-conditioning performance. The blower wheel supplements insufficient air volume of the second scroll and air-conditioning performance since the diameter (d 2 ) of the second blower wheel  278  is larger than the diameter (d 1 ) of the first blower wheel  277 . 
     Additionally, a height (h 1 ) of the first blower wheel  277  is larger than a height (h 2 ) of the second blower wheel  278 . A height of the blower unit  200  must be lower than a predetermined height in an aspect of a package standard. Therefore, the first blower wheel  277  or the second blower wheel  278  is formed to be low. Because the height (h 2 ) of the second blower wheel  278  is lower than the height (h 1 ) of the first blower wheel  277 , a package height of the blower unit becomes lower and the blower wheel structure that the diameter is greater than the height is favorable to inhale and blow the air of the vertical direction in the radial direction. 
       FIG. 13  is a graph for explaining a scroll expansion angle of the two-layered air conditioner for a vehicle according to the embodiment of the present invention, and  FIGS. 14 and 15  are graphs for explaining an air-conditioning performance improvement result according to the scroll expansion angle. 
     Referring to  FIGS. 13, 14, 15A and 15B , the scroll case expands the scroll while the distance between the center of the blower wheel and the outer wall surface is varied according to angles from the “cut off” point in  FIG. 11 , and the scroll case can be divided as shown in  FIG. 13  according to expansion methods of angles. The blower unit according to the embodiment of the present invention adopts an “exponential” expansion method, and can optimize a scroll design since the expansion angle of the first scroll is 5.5° and the expansion angle of the second scroll is 6.3°. 
     Referring to  FIG. 13 , a formula of a “linear’ scroll development of the scroll case is defined as He=Rw×(1+tan(α)). 
     In addition, a formula of an “exponential’ scroll development of the scroll case satisfies 
         He=Rw× (1+2π×tan(α)) θ÷2π ,(0≤θ≤2π)
 
         He′=Rw ′× (1+2π×tan(α′)) θ′÷2π ,(0≤θ′≤2π−θ c,θ′=θ−θc ).
 
     Referring to  FIG. 14 , line A is that the expansion angle of the first scroll is equal to the expansion angle of the second scroll, and line B is that the expansion angle of the first scroll is 5.5° and the expansion angle of the second scroll is 6.3°. In case of line A, it is confirmed that pressure drops sharply in a flow rate zone of about 400 to 500 [CMH]. On the other hand, line B shows a relatively uniform pressure distribution according to the flow rate and compression is better. 
     Moreover, referring to  FIG. 15B , compared with  FIG. 15A , shows a relatively uniform speed distribution. Especially,  FIG. 15A  which is the scroll case having the same expansion angle at upper and lower sides near to the air outlet of the scroll case indicated by a red circle shows that blue color is partially shown at several parts, and it shows that speed distribution is not uniform. On the other hand,  FIG. 15B  which is the scroll case of which a lower expansion angle is larger than an upper expansion angle does not show blue color and shows a relatively uniform speed distribution. 
     Meanwhile,  FIG. 16  is a front view showing a state where the scroll case is separated. 
     Referring to  FIG. 16 , a start point of the scroll development part of the first scroll and a start point of the scroll development part of the second scroll are different from each other. Preferably, the start point of the scroll development part of the first scroll in the air flow direction is formed to be further back than the start point of the scroll development part of the second scroll. That is, a distance (c) between the start point  291  of the scroll development part of the upper scroll case  283  and an end portion of the air outlet is shorter than a distance (d) between the start point  292  of the scroll development part of the lower scroll case  284  and the end portion of the air outlet. Furthermore, a height (g 1 ) of the upper scroll case  283  is higher than a height (g 2 ) of the lower scroll case  284 . 
     The lower scroll case  284  is deteriorated in air-conditioning performance since being more complicated in air introduction path and being narrower than the upper scroll case  283 . Therefore, if the upper scroll case and the lower scroll case are designed in such a way that the scroll development part of the upper scroll case and the scroll development part of the lower scroll case are located at the same position, air-conditioning performance is deteriorated since the upper scroll case is not compressed sufficiently. Like the embodiment of the present invention, since the scroll development start point of the upper scroll case  283  is later than that of the lower scroll case  284 , the scroll case has two air introduction paths so as to effectively overcome shortcomings of the conventional air conditioner. 
       FIGS. 17A, 17B, 18 and 19  are graphs for explaining an air-conditioning performance improvement result according to the start point of the scroll development part according to the embodiment of the present invention.  FIG. 17A  shows that the start point of the scroll development part of the first scroll is equal to the start point of the scroll development part of the second scroll, and  FIG. 17B  shows that the start point of the scroll development part of the first scroll is formed to be further back than the start point of the scroll development part of the second scroll. 
     Referring to  FIG. 17B , compared with  FIG. 17A  shows that the speed distribution is relatively uniform. Especially,  FIG. 17A  shows that blue color is partially shown at several parts near to the air outlet of the scroll case of  FIGS. 17A and 17B , and it shows that speed distribution is not uniform. On the other hand,  FIG. 17B  does not show blue color and shows a relatively uniform speed distribution. 
     Referring to  FIG. 18 , line A compared with line B shows that pressure according to the flow rate is relatively low, and referring to  FIG. 19 , line A compared with line B shows that noise is relatively bigger. 
     While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various modifications and equivalents may be made without deviating from the spirit or scope of the invention. Therefore, it would be understood that the technical and protective scope of the present invention shall be defined by the technical idea as defined by the following claims and the equivalences.