Patent Publication Number: US-2022212520-A1

Title: Air conditioner for vehicle

Description:
TECHNICAL FIELD 
     The present invention relates to an air conditioner for a vehicle, and more particularly, to a two-layer air conditioner for a vehicle, which can secure defogging performance and maintain a high-performance heating during heating. 
     BACKGROUND ART 
     In general, an air conditioner for a vehicle is an apparatus for cooling or heating the interior of the vehicle by cooling or heating through the process of introducing outdoor air into the interior of the vehicle or circulating indoor air of the vehicle. Such an air conditioner for a vehicle includes an evaporator for a cooling action and a heater core for a heating action inside an air-conditioning case, and selectively blows the air cooled by the evaporator or heated by the heater core toward parts of the interior of the vehicle. 
     Especially, in order to secure defogging performance and maintain a high-performance heating during heating, a two-layer air conditioner has been developed. In order to defrost windshields while driving with heat in winter, cold outdoor air with low humidity is effective, but it causes drop of indoor temperature. 
     The two-layer air conditioner substantializes a two-layer air flow of indoor air and outdoor air by supplying outdoor air to the upper part of the vehicle and by circulating indoor air to the lower part of the vehicle, so as to effectively defrost using fresh outdoor air with low humidity supplied to the upper part and to maintain high-performance heating by providing fresh outdoor air to passengers and providing warm indoor air to the lower part. 
       FIG. 1  is a sectional view illustrating a conventional two-layer air conditioner for a vehicle. Referring to  FIG. 1 , the conventional two-layer air conditioner for a vehicle includes an air conditioning case  10 . The air conditioning case  10  includes an air passage  14  of a predetermined form formed therein, an indoor air inlet  14   a  and an outdoor air inlet  14   b  which are formed at an entrance of the air passage to be partitioned by a partition wall  40 , and a plurality of air outlets formed at an exit thereof. The air outlets are a defrost vent  16 , a face vent  17 , a floor vent  18 , and a console vent  19 . 
     The air conditioning case  10  includes a blower unit disposed at the entrance thereof, and an evaporator  2  and a heater core  3  mounted inside the air conditioning case  10  to be spaced apart from each other at a predetermined interval. An electric heater  4 , such as a PTC, may be further disposed downstream of the heater core  3 . The air passage of the air conditioning case  10  is partitioned into an upper passage and a lower passage by the partition wall  40 . The air introduced into the indoor air inlet  14   a  flows to the lower passage, and the air introduced into the outdoor air inlet  14   b  flows to the upper passage. Meanwhile, a warm air passage has a baffle  45  disposed to prevent heat pickup by the heater core  3  and the electric heater  4 . 
     The upper passage has a first temperature door  11  disposed to adjust the volume of the air passing through the heater core  3  and the volume of the air bypassing the heater core  3 , and the lower passage has a second temperature door  12  disposed to adjust the volume of the air passing through the heater core  3  and the volume of the air bypassing the heater core  3 . The air outlet has a defrost door  21  for adjusting the degree of opening of the defrost vent  16 , and a face door  22  for adjusting the degree of opening of the face vent  17 . Moreover, the air outlet further has a floor door  23  for adjusting the degree of opening of the floor vent  19 , and a console door  24  for adjusting the degree of opening of the console vent  19 . 
       FIG. 2  is a view illustrating a vent mode of the conventional two-layer air condition for a vehicle. Referring to  FIG. 2 , in the vent mode, the first temperature door  11  and the second temperature door  12  closes the warm air passage. Furthermore, the floor door  23  closes the floor vent  18 , and the console door  24  closes the console vent  19 . Cold air passing through the evaporator  2  bypasses the heater core  3 , some of the air is discharged to the interior through the face vent  17  after passing through the upper passage, and the other is discharged to the interior through the face vent  17  after rising while passing through the lower passage. 
     In the vent mode of the conventional two-layer air conditioner for a vehicle, the air passing through the evaporator  2  is divided into an upper layer and a lower layer by bypassing the heater core  3 , and moves toward the face door  22 . In this instance, the moved air is not directly discharged to the face vent  17 , and the upper layer air and the lower layer air introduced into a mixing part collide with each other to generate a vortex. So, the conventional two-layer air condition for a vehicle has a disadvantage in that the air volume is decreased because of an increase of resistance. 
       FIG. 3  is a view illustrating a floor mode of the conventional two-layer air condition for a vehicle. Referring to  FIG. 3 , in a floor mode, the first temperature door  11  and the second temperature door  12  opens the warm air passage. Furthermore, the floor door  23  opens the floor vent  18 , and the console door  24  closes the console vent  19 . Some of the warm air passing the heater core  3  and the defrost vent  16  after passing the evaporator  2  is discharged to the defrost vent  16  through the upper passage, and the other is discharged to the floor vent  18  through the lower passage. 
     Because the conventional two-layer air conditioner for a vehicle has a restriction in the package size, a part (A) of the passage gets narrower due to the baffle  45 , which is formed in the warm air passage to prevent heat pickup. Accordingly, the air volume gets weak since the air of the upper warm air passage passing the heater core  3  cannot smoothly flow to the defrost vent  16  in a mixing zone (B). Finally, the conventional two-layer air conditioner for a vehicle has another disadvantage in that there is an excessive top and bottom temperature difference in the temperature evaluation of the floor mode. 
     DISCLOSURE 
     Technical Problem 
     Accordingly, the present invention has been made in an effort to solve the above-mentioned problems occurring in the prior arts, and it is an object of the present invention to provide an air conditioner for a vehicle which has an improved guide structure that can increase air volume by preventing collision of air moving through an upper passage and a lower passage. 
     It is another object of the present invention to provide an air conditioner for a vehicle, which can effectively improve the top and bottom temperature difference by inducing warm air passing a heater core toward a defrost vent and by inducing cold air passing an evaporator toward a defrost vent. 
     Technical Solution 
     To achieve the above objects, the present invention provides an air conditioner for a vehicle, which includes an air conditioning case having an air passage formed therein and air outlets which include a defrost vent and a face vent, and a heat exchanger for cooling and a heat exchanger for heating, which are provided in the air passage of the air conditioning case, the air conditioner including: a temperature door arranged between the heat exchanger for cooling and the heat exchanger for heating in order to adjust the degree of heating of cold air, which passed the heat exchanger for cooling, by the heat exchanger; a cold air passage through which cold air that passed the heat exchanger for cooling bypasses the heat exchanger for heating; a warm air passage through which the cold air that passed the heat exchanger for cooling passes the heat exchanger for heating; a cold air guide unit for guiding the cold air downstream of the heat exchanger for cooling; and a warm air guide unit for guiding the warm air downstream of the heat exchanger for heating. 
     Moreover, the air passage in the air conditioning case is partitioned into an upper passage and a lower passage by a partition wall. The warm air guide unit changes a flow path of the air, which will head toward the face vent after passing the heat exchanger for heating, to be guided to the defrost vent. 
     Furthermore, the warm air guide unit includes a bypass part that makes a flow path of the air guided to the defrost vent bypass so that the air is directly discharged to the face vent. 
     Additionally, a baffle for preventing heat pickup is disposed in the warm air passage downstream of the heat exchanger for heating in order to block heat of the heat exchanger for heating from influencing on cold air. The warm air guide unit extends integrally from an end portion of the baffle for preventing heat pickup. 
     In addition, the cold air guide unit guides the air passing the heat exchanger for cooling to the face vent, which adjoins the defrost vent, so that a mixing zone between the cold air and the warm air is moved toward the defrost vent. 
     Moreover, the warm air guide unit includes: a vertical part extending toward the face vent along the warm air passage downstream of the heat exchanger for heating; and a curved part curved toward the defrost vent from the upper end portion of the vertical part. 
     Furthermore, the war air guide unit has an opening part formed in the vehicle width direction. 
     Additionally, the air passage of the air conditioning case is formed to be partitioned in the vehicle width direction by a separator. The warm air guide unit is formed on both sides of the separator and on the inner surfaces of both sides of the air conditioning case in the vehicle width direction, and an opening part is formed between the warm air guide unit of the air conditioning case and the warm air guide unit of the separator. 
     In addition, the cold air guide unit has a streamlined surface formed on the surface facing the cold air passage, includes a vent door for adjusting the degree of opening of the face vent, and an extension line of the end portion of the streamlined surface is formed side by side with the vent door at an angle that the vent door fully opens the face vent. 
     Moreover, a surface rib for reinforcing rigidity protrudes from the outer face of the air conditioning case, and the warm air guide unit is on the inner wall surface of the air conditioning case to correspond to the surface rib of the air conditioning case so as to perform a guide function and a rigidity reinforcing function. At least one inclined part is disposed on the inner wall surface of the air conditioning case to make the air conditioning case protrude in the form of a surface rib, and the warm air guide unit extends in contact with the inclined part. 
     Furthermore, the warm air guide unit is formed to be closer to the face vent than the extension line of a heat exchanger support part on the upper portion of the heat exchanger for heating. The warm air guide unit is located between the extension line of a heat exchanger support part on the upper portion of the heat exchanger for heating and an extension line of the cold air guide unit. The cold air guide unit extends from a temperature door seating part to the heat exchanger support part on the upper portion of the heat exchanger for heating so as to be arranged above and in front of the heat exchanger for heating. 
     Additionally, air conditioner for a vehicle further includes a vent door for adjusting the degree of opening of the face vent, and the cold air guide unit and the warm air guide unit change the point, where the cold air of the cold air passage and the warm air of the warm air passage are mixed, to approach the face vent. 
     In addition, the cold air guide unit and the warm air guide unit are formed at the top of the rear surface of the heat exchanger for heating. 
     Moreover, the cold air guide unit and the warm air guide unit guide air to head in a range of the opening part formed by the vent door and the face vent. 
     Furthermore, the air conditioning case is partitioned into an upper passage and a lower passage by a partition wall, and includes: a first temperature door disposed in the upper passage to adjust an amount of air passing the heat exchanger for heating and an amount of air bypassing the heat exchanger for heating; and a second temperature door disposed in the lower passage to adjust an amount of air passing the heat exchanger for heating and an amount of air bypassing the heat exchanger for heating. The cold air guide unit and the warm air guide unit guide the air to face a rotary shaft of the vent door. 
     Additionally, the vent door is a center pivot type door of which both ends rotate around the rotary shaft, and the face vent has a first opening area formed at one side based on the rotary shaft and a second opening area formed at the other side based on the rotary shaft. 
     Moreover, the cold air guide unit guides the air to the first opening area, and the warm air guide unit guides the air to the second opening area. 
     Furthermore, the first opening area is wider than the second opening area. 
     Additionally, the upper passage includes an upper cold air passage and an upper warm air passage, the lower passage includes a lower warm air passage and a lower cold air passage, and the upper cold air passage, the upper warm air passage, the lower warm air passage, and the lower cold air passage are formed in order from the top. The upper passage and the lower passage communicate with each other. The cold air guide unit guides the air, which flows in the upper cold air passage, to the first opening area, and the warm air guide unit guides the air, which flows in at least one among the upper warm air passage, the lower warm air passage and the lower cold air passage, to the second opening area. 
     Advantageous Effects 
     The air conditioner for a vehicle according to an embodiment of the present invention can increase air volume by preventing collision of air moving through the upper passage and the lower passage, and is favorable to manufacturability and assemblability by optimizing the form and position of the air conditioner. 
     Additionally, the air conditioner for a vehicle according to an embodiment of the present invention can reduce top and bottom temperature difference in the floor mode because of a rise of temperature at the outlet of the defrost vent in a temperature control evaluation, enhance mixing performance since cold air and warm air are concentrated in the same direction, is favorable for temperature evaluation, and enhance dynamic stiffness of the air conditioning case by optimizing the form and position of the guide unit. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a sectional view illustrating a conventional two-layer air conditioner for a vehicle. 
         FIG. 2  is a view illustrating a vent mode of the conventional two-layer air condition for a vehicle. 
         FIG. 3  is a view illustrating a floor mode of the conventional two-layer air condition for a vehicle. 
         FIG. 4  is a sectional view illustrating a two-layer air conditioner for a vehicle according to a first preferred embodiment of the present invention. 
         FIGS. 5 and 6  are enlarged sectional views of a guide unit according to the first preferred embodiment of the present invention. 
         FIG. 7  illustrates an air volume evaluation result of a two-layer air conditioner for a vehicle to which the guide unit is not applied. 
         FIG. 8  illustrates an air volume evaluation result of the two-layer air conditioner for a vehicle according to the first preferred embodiment of the present invention, to which the guide unit is applied. 
         FIG. 9  is a view illustrating a modification of  FIG. 4 . 
         FIG. 10  is a sectional view illustrating a two-layer air conditioner for a vehicle according to a second preferred embodiment of the present invention. 
         FIG. 11  is a partially enlarged sectional view of  FIG. 10 . 
         FIG. 12  is a perspective view illustrating the inside of a part of an air conditioning case according to the second preferred embodiment of the present invention. 
         FIGS. 13 and 14  are sectional views illustrating operational examples of  FIG. 11 . 
         FIG. 15  is an enlarged perspective view illustrating a third guide unit and the inside of the air conditioning case according to the second preferred embodiment of the present invention. 
         FIG. 16  is a sectional view taken along the line A-A of  FIG. 15 . 
         FIG. 17  is a view illustrating a vent mode of the air conditioner for a vehicle according to the second preferred embodiment of the present invention. 
         FIG. 18  is a view illustrating a floor mode of the air conditioner for a vehicle according to the second preferred embodiment of the present invention. 
         FIG. 19  is a view illustrating a mixing mode of the air conditioner for a vehicle according to the second preferred embodiment of the present invention. 
     
    
    
     MODE FOR INVENTION 
     Hereinafter, an air conditioner for a vehicle according to preferred embodiments of the present invention will now be described in detail with reference to the attached drawings. 
       FIG. 4  is a sectional view illustrating a two-layer air conditioner for a vehicle according to a first preferred embodiment of the present invention,  FIGS. 5 and 6  are enlarged sectional views of a guide unit according to the first preferred embodiment of the present invention,  FIG. 7  illustrates an air volume evaluation result of a two-layer air conditioner for a vehicle to which the guide unit is not applied,  FIG. 8  illustrates an air volume evaluation result of the two-layer air conditioner for a vehicle according to the first preferred embodiment of the present invention, to which the guide unit is applied, and  FIG. 9  is a view illustrating a modification of  FIG. 4 . 
     In the description of the present invention, the right-and-left direction of  FIG. 4  is the back-and-forth direction of the vehicle. 
     Referring to  FIGS. 4 to 9 , the two-layer air conditioner for a vehicle according to the first preferred embodiment of the present invention includes an air conditioning case  110 . The air conditioning case  110  has an air passage of a predetermined form therein. The air conditioning case  110  has an air inlet formed at an entrance of the air passage, and a plurality of air outlets formed at an exit of the air passage. The air outlets are a defrost vent  116 , a face vent  117 , a floor vent  118 , and a console vent  119 . The air conditioning case  110  includes doors disposed therein. The doors are configured to open and close the air outlets, and include a defrost door  121  for adjusting the degree of opening of the defrost vent  116 , a vent door  122  for adjusting the degree of opening of the face vent  117 , a floor door  123  for adjusting the degree of opening of the floor vent  118 , and a console door  124  for adjusting the degree of opening of the console vent  119 . 
     The air conditioning case  110  further includes a blower unit disposed at the entrance, and heat exchangers mounted therein. The heat exchangers are configured to exchange heat with air passing through the air conditioning case, and include a heat exchanger for cooling and a heat exchanger for heating, which are arranged in the air passage of the air conditioning case  110  in order. The heat exchanger for cooling is an evaporator  102 , and the heat exchanger for heating is a heater core  103 . The evaporator  102  and the heater core  103  are mounted in order in the air flow direction to be spaced apart from each other at a predetermined interval. 
     The air passage of the air conditioning case  110  is partitioned into an upper passage  141  and a lower passage  142  by a partition wall  140 . The air introduced into an indoor air inlet flows into the lower passage  142 , and the air introduced into an outdoor air inlet flows into the upper passage  141 . The partition wall  140  extends to the upstream side of the evaporator  102 , between the evaporator  102  and the heater core  103 , and downstream of the heater core  103 . 
     A first temperature door  111  is disposed on the upper passage  141  to adjust the volume of the air passing through the heater core  103  and the volume of the air bypassing the heater core  103 , and a second temperature door  112  is disposed on the lower passage  142  to adjust the volume of the air passing through the heater core  103  and the volume of the air bypassing the heater core  103 . 
     That is, the upper passage  141  includes an upper cold air passage and an upper warm air passage, and the lower passage  142  includes a lower warm air passage and a lower cold air passage. The upper cold air passage, the upper warm air passage, the lower warm air passage, and the lower cold air passage are arranged in order from the top. The upper passage  141  and the lower passage  142  are disposed to communicate with each other. The floor door  123  is located on the rear surface of the heater core  103  to face the heater core. The floor door  123  touches the partition wall  140  when rotating to the maximum in the clockwise direction. 
     Rotating to the maximum in the clockwise direction, the floor door  123  touches the partition wall  140  to function as the partition  140 , which partitions the upper passage  141  and the lower passage  142  from each other. On the contrary, When the floor door  123  rotates to the maximum in the counterclockwise direction, the floor vent  118  is closed, and the upper passage  141  and the lower passage  142  communicates with each other. 
     Moreover, the air conditioner for a vehicle includes a guide unit  200 . The guide unit  200  includes a cold air guide unit for guiding cold air downstream of the evaporator  102 , and a warm air guide unit for guiding warm air downstream side the heater core  103 . The guide unit  200  functions to make the point, where two kinds of air to adjust temperature are mixed, approach the air outlet. That is, the guide unit  200  guides the air to be in a range of an opening part formed by the door and the air outlet. Furthermore, the guide unit  200  guides the cold air passage and the warm air passage to face a rotary shaft  1221  of the vent door  122 . Therefore, the air of the cold air passage and the air of the warm air passage flow toward the rotary shaft  1221  of the vent door  122 . 
     So, the air conditioner for a vehicle can prevent a vortex generated by collision of the air flowing in the cold air passage and the air flowing in the warm air passage, thereby increasing the volume of the air flowing toward the face vent  117 . 
     The vent door  122  is a center pivot type door which rotates around the rotary shaft  1221 . The vent door  122  includes a main plate extending from the rotary shaft  1221  in a radial direction, and a tail plate extending in the opposite direction from the main plate. The main plate covers an area which is wider than an area covered by the tail plate. 
     The face vent  117  includes a first opening area  1171  formed at a side based on the rotary shaft  1221 , and a second opening area  1172  formed at the other side based on the rotary shaft  1221 . The first opening area  1171  is the front side of the vent door  122 , and is an area covered by the main plate of the vent door  122 . The second opening area  1172  is the rear side of the vent door  122 , and is an area covered by the tail plate. The first opening area  1171  is formed to be wider than the second opening area  1172 . 
     The guide unit  200  includes a first guide unit  210  and a second guide unit  220 . The first guide unit  210  is a cold air guide unit, and the second guide unit  220  is a warm air guide unit. The first guide unit  210  guides the air to the first opening area  1171 , and the second guide unit  220  guides the air to the second opening area  1172 . 
     In the vent mode, an amount of the air flowing through the upper passage  141  is more than an amount of the air flowing through the lower passage  142 . Because the first opening area  1171  is wider than the second opening area  1172 , the air of the upper passage  141  guided by the first guide unit  210  is discharged to the first opening area  1171  which is relatively wider, and the air of the lower passage  142  guided by the second guide unit  220  is discharged to the second opening area  1172  which is relatively narrower, so that total volume of the discharged air can be increased. 
     An extension line  2101  of the first guide unit  210  and an extension line  2201  of the second guide unit  220  are formed to face the rotary shaft  1221  of the vent door  122 . That is, the extension line  2101  of the first guide unit  210  and the extension line  2201  of the second guide unit  220  meet each other at the rotary shaft  1221  of the vent door  122 . 
     Through the above configuration, the first guide unit  210  guides the air flowing in the upper cold air passage to the first opening area  1171 . In addition, the second guide unit  220  guides the air flowing in at least one among the upper warm air passage, the lower warm air passage and the lower cold air passage to the second opening area  1172 . 
     In the mixing mode, some of the air passing the evaporator  102  passes the heater core  103 , and the other bypasses the evaporator  102 . Such an air flow can occur in the upper passage  141  and in the lower passage  142  at the same time. The air passing the upper cold air passage after passing the evaporator  102  is guided to the first opening area  1171  by the first guide unit  210 , and the air passing the lower cold air passage after passing the evaporator  102  rises and is guided to the second opening area  1172  by the second guide unit  220 . 
     In more detail, the air passing the upper cold air passage is essentially guided by the first guide unit  210 , and the air passing at least one among the upper warm air passage, the lower warm air passage, or the lower cold air passage is essentially guided by the second guide unit  220 . In this instance, depending on the operation of the floor door  123 , it is determined that the upper passage  141  and the lower passage  142  communicate with each other, and it is also determined that the air of the lower warm air passage and the air of the lower cold air passage flow to the second guide unit  220 . 
     In other words, the first guide unit  210  is formed at a rear upper end portion  2015  of the heater core  103  to face the rotary shaft  1221  of the vent door  122 , so that the flow of upper passage  141  faces the front surface of the vent door  122 . In more detail, the first guide unit  210  is curved to be streamlined toward the rotary shaft  1221  of the vent door  122  from the rear upper end portion  2015  of the heater core  103 . 
     The air of the upper cold air passage which passes the evaporator  102 , bypasses the heater core  103  and flows the upper passage  141  flows approximately horizontally up to the upper portion of the heater core  103 . The first opening area  1171  of the face vent  117  is located directly above the rear upper end portion  2015  of the heater core  103 . The streamlined first guide unit  210  softly converts the direction of the air horizontally flowing in the upper cold air passage into an upward direction. Therefore, the air is guided to the first opening area  1171  of the face vent  117  without any increase of resistance so as to increase the air volume. 
     Moreover, the second guide unit  220  makes the flow of the lower passage  142  face the rear surface of the vent door  122  so that the flow of the lower passage  142  faces the rotary shaft  1221  of the vent door  122  at a lower flow end  2205 . In more detail, the second guide unit  220  extends from the lower flow end  2205  to be inclined toward the rotary shaft  1221  of the vent door  122 . 
     The air of the lower cold air passage which passes the evaporator  102 , bypasses the heater core  103  and flows in the lower passage  142  flows approximately horizontally up to the lower portion of the heater core  103 , and then, flows upwards along a communication path between the upper passage and the lower passage opened by the floor door  123 . The second opening area  1172  of the face vent  117  is located approximately diagonally above the lower flow end portion  2205 . The second guide unit  220  which extends to be inclined softly converts the direction of the air flowing upwards in the lower cold air passage so that the air flows diagonally upwards to be in a range of the second opening area  1172 . Therefore, the air is guided to the second opening area  1172  of the face vent  117  without any increase of resistance so as to increase the air volume. 
     The guide unit  200  is formed at the top of the rear surface of the heater core  103 . Additionally, the guide unit  200  includes a connection part  230  which connects the first guide unit  210  and the second guide unit  220  with each other. The first guide unit  210 , the connection part  230 , and the second guide unit  220  extend integrally from a heat exchanger support part  225  of the air conditioning case  110  to support the heater core  103 . 
     In the meantime, as illustrated in  FIG. 9 , it is also possible that the connection part is not formed and the first guide unit  210  and the second guide unit  220  are formed to be spaced apart from each other. However, as illustrated in  FIG. 4 , if the first guide unit  210 , the second guide unit  220 , and the connection part  230  are formed integrally on the air conditioning case  110 , it is favorable in manufacturability since a mold design is simplified, and can improve structural intensity since the connection part  230  supports the first guide unit  210  and the second guide unit  220 . 
     Moreover, the air conditioner for a vehicle according to the preferred embodiment of the present invention can increase intensity by a space surrounded by the first guide unit  210 , the second guide unit  220 , and the connection part  230 , and enhance assemblability since the first guide unit  210 , the second guide unit  220 , and the connection part  230  serve as a support part when right and left cases are assembled. 
     Meanwhile, referring to  FIG. 7 , in case of a two-layer air conditioner, to which the guide unit is not applied, it is confirmed that the air volume of the left side vent (LH) is 88.5, the air volume of the left center vent (LC) is 99.9, the air volume of the right center vent (RC) is 97.8, the air volume of the right side vent (RH) is 92.2, and the total air volume is 435.3. 
     Meanwhile, referring to  FIG. 8 , in case of a two-layer air conditioner, to which the guide unit is applied, it is confirmed that the air volume of the left side vent (LH) is 92.3, the air volume of the left center vent (LC) is 106.8, the air volume of the right center vent (RC) is 100.1, the air volume of the right side vent (RH) is 95.2, and the total air volume is 455.1. As described above, it was confirmed experimentally that the air volume of each outlet and the total air volume were increased when the guide unit was applied. 
       FIG. 10  is a sectional view illustrating a two-layer air conditioner for a vehicle according to a second preferred embodiment of the present invention,  FIG. 11  is a partially enlarged sectional view of  FIG. 10 ,  FIG. 12  is a perspective view illustrating the inside of a part of an air conditioning case according to the second preferred embodiment of the present invention, and  FIGS. 13 and 14  are sectional views illustrating operational examples of  FIG. 11 . 
     Hereinafter, the right-and-left direction in  FIG. 10  is the back-and-forth direction of the vehicle. Compared with the first preferred embodiment, in the second preferred embodiment, like components are referenced by like reference numerals and description thereof is not repeated. 
     Referring to  FIGS. 10 to 14 , the two-layer air conditioner for a vehicle according to the second preferred embodiment of the present invention includes an air conditioning case  110 , an evaporator  102 , a heater core  103 , a first temperature door  111 , and a second temperature door  112 . Air outlets of the air conditioning case  110  include a defrost vent  116 , a face vent  117 , a floor vent  118 , and a console vent  119 . An electric heater  104 , such as a PTC, is disposed downstream of the heater core  103  in the air flow direction. The air outlet includes a defrost door  121 , a vent door  122 , a floor door  123 , and a console door  124  disposed to adjust the degree of opening of the vents. An air passage of the air conditioning case  110  is partitioned into an upper passage  141  and a lower passage  142  by the partition wall  140 . 
     The air conditioner for a vehicle includes a third guide unit  310  and a fourth guide unit  320 . The third guide unit  210  is a warm air guide unit, and the fourth guide unit  220  is a cold air guide unit. The third guide unit  310  guides warm air downstream of the heater core  103  to the defrost vent  116 . The fourth guide unit  320  guides cold air downstream of the evaporator  102  to the face vent  117 . 
     That is, the third guide unit  310  guides a flow path of the air of the upper passage  141 , which passes the heater core  103  to head toward the face vent  117 , to the defrost vent  116 . In addition, the third guide unit  310  includes a bypass part which bypasses the flow path of the air guided to the defrost vent  116  so that the air is discharged to the face vent  117 . 
     Moreover, the fourth guide unit  320  is disposed between the evaporator  102  and the heater core  103 . The fourth guide unit  320  guides the air passing the evaporator  102  to the face vent  117  adjacent to the defrost vent  116 . That is, the defrost vent  116  and the face vent  117  are formed on the upper surface of the air conditioning case  110  to be side by side from the front of the vehicle to the rear. The fourth guide unit  320  moves the mixing zone between the cold air and the warm air toward the defrost vent. 
     In detail, a baffle  145  for preventing heat pickup is disposed in the warm air passage downstream of the heater core  103 . The baffle  145  for preventing heat pickup partitions between the passage downstream of the heater core  103  and the passage bypassing the heater core  103  in order to block the heat pickup phenomenon that heat of the heater core  103  influences on cold air. The third guide unit  310  extends integrally from an end portion of the baffle  145  for preventing heat pickup. 
     The baffle  145  for preventing heat pickup has good function to prevent the heat pickup phenomenon, but has adverse effect that makes the upper warm air passage passing the heater core  103  get narrower. Finally, because of the baffle  145  for preventing heat pickup, warm air passing the heater core  103  gets weaker when the warm air flows toward the defrost vent  116  from the mixing zone. 
     In order to solve the above problem, the third guide unit  310  guides the warm air of the upper warm air passage passing the heater core  103  to fully move toward the outlet of the defrost vent  116  after passing the mixing zone. Therefore, in the temperature control evaluation, temperature of the outlet of the defrost vent  116  rises, so that the top and bottom temperature difference between the defrost vent  116  and the floor vent  118  can be improved in the floor mode. 
     As described above, the third guide unit  310  has good function to increase warm air volume toward the defrost vent  117 , but has adverse effect that the air volume toward the face vent  117  is decreased. The fourth guide unit  320  can prevent a decrease of the air volume toward the face vent  117  by the third guide unit  310  by guiding cold air toward the face vent  117 , and improve mixability between cold air and warm air by moving the mixing zone toward the defrost vent  116 . 
     In more detail, the third guide unit  310  includes a vertical part  312 , a curved part  311 , and an opening part  315 . The vertical part  312  extends toward the face vent  117  along the warm air passage downstream of the heater core  103 . The curved part  311  extends from the upper end portion of the vertical part  312  toward the defrost vent  116  to be curved. The opening part  315  is formed at a predetermined portion of the third guide unit  310  in the vehicle width direction. The opening part  315  serves the function of the bypass part. 
     Due to the configuration of the opening part  315 , the flow path of the air guided toward the defrost vent  116  is bypassed, and the air of the war air passage passing the heater core  103  is directly discharged to the face vent  117 . Through the above, the third guide unit can minimize a loss of air volume and prevent deterioration in air-conditioning performance while carrying out the guide function sufficiently. 
     The third guide unit  310  extends integrally from the inner wall surfaces of the left case and the right case. In this instance, the third guide unit of the left case and the third guide unit of the right case are spaced apart from each other at a predetermined interval in the vehicle width direction, and the opening part  315  is formed between the third guide units. Due to the above structure, the third guide unit can be formed integrally in a rib shape when the left case and the right case are injection-molded without any additional boring process. The opening part  315  is effectively formed without increase of manufacturing costs. 
     In more detail, the air conditioning case  110  is formed by the combination of the left case, the right case, and a separator. The air passage of the air conditioning case  110  is partitioned into the left and the right in the vehicle width direction by the separator. The third guide unit  310  is formed on both sides of the separator and on both inner surfaces of the air conditioning case  110  in the vehicle width direction. That is, the opening part  315  is formed between a third guide unit  310   a  of the air conditioning case and a third guide unit  310   b  of the separator. Therefore, when the left case and the right case are assembled, since the third guide unit  310   a  of the air conditioning case and the third guide unit  310   b  of the separator are not directly assembled, assemblability is improved. 
     The baffle  145  for preventing heat pickup is formed in the upper passage  141  of the warm air passage downstream of the heater core  103 . Moreover, the baffle  145  for preventing heat pickup horizontally extends at the middle part of the warm air passage of the upper passage  141  in the vertical direction. The third guide unit  310  extends upwards from the baffle  145  for preventing heat pickup, and then, is curved toward the defrost vent  116 . 
     Referring to  FIG. 11 , the extension line of the end portion of the curved part  311  is formed to face the bottom surface of the entrance of the defrost vent  116 . So, warm air passing the heater core  103  is guided by the curved part  311  and is smoothly guided to the entrance of the defrost vent  116 . 
     Furthermore, at an angle that the vent door  122  fully opens the face vent  117 , the end portion of the vent door  122  meets or intersects the extension line of the end portion of the curved part  311 . That is, the end portion of the main plate of the vent door  122  meets or intersects the extension line of the end portion of the curved part  311 . The main plate of the vent door  122  serves as a resistive barrier of the air facing the defrost vent  116  by the curved part  311  so as to guide some of the air facing the vent door  122  toward the face vent  117 . Therefore, in the vent mode that the vent door  122  opens the face vent  117 , some of the air facing the defrost vent  116  is guided toward the face vent  117  so as to prevent the air volume toward the face vent  117  from lowering. 
     Meanwhile, the heater core  103  is fixed and supported by the support part formed on the air conditioning case  110 . The heat exchanger support part  225  which supports the heater core  103  is formed integrally with the air conditioning case  110 . In this instance, the fourth guide unit  320  extends integrally from the support part  25 . The air guided by the third guide unit  310  and the air guided by the fourth guide unit  320  are concentrated in the same direction, so that the mixing zone is moved toward the defrost vent  116 . 
       FIG. 13  illustrates a flow of the air in the floor mode. Referring to  FIG. 13 , the air passing the heater core  103  is guided by the vertical part  312  and the curved part  311  of the third guide unit  310  so that the flow direction is changed to the defrost vent  116 . 
     Additionally,  FIG. 14  illustrates a flow of the air in the mixing mode. Referring to  FIG. 14 , some of the air passing the evaporator  102  bypasses the heater core  103  and flows above the heater core  103 . The air above the heater core  103  is guided to the left of the face vent  117 , the front side of the vehicle, by the fourth guide unit  320 . In addition, the other of the air passing the evaporator  102  is guided toward the defrost vent  116  by the third guide unit  310  after passing the heater core  103 . 
     Therefore, if the third guide unit and the fourth guide unit are not disposed, the mixing zone is formed at a “C (dotted line)” part, but as described in the present invention, if the third guide unit and the fourth guide unit are disposed, the mixing zone is moved and is formed at a “D (solid line)” part. In other words, the mixing zone is moved to the left top, the top of the front side of the vehicle, by the third guide unit  310  and the fourth guide unit  320 . Therefore, the mixing zone between the cold air and the warm air is fully moved toward the defrost vent  116  to improve mixing performance. 
     In the meantime, the fourth guide unit  320  includes a streamlined surface  321 . The streamlined surface  321  is formed on the surface facing the cold air passage. The fourth guide unit  320  continuously extends from the inner wall surface of the left case to the inner wall surface of the right case in the vehicle width direction. As illustrated in  FIG. 4 , the extension line of the end portion of the streamlined surface  321  is formed side by side with the vent door  122  at an angle that the vent door  122  fully opens the face vent  117 . 
     That is, the fourth guide unit  320  is formed on both sides of the separator and on the inner surfaces of both sides of the air conditioning case  110  in the vehicle width direction. The fourth guide unit of the air conditioning case and the fourth guide unit of the separator are coupled with each other, so that the fourth guide unit  320  continuously extends from the inner wall surface of the left case to the inner wall surface of the right case in the vehicle width direction. Therefore, the fourth guide unit  320  performs the function to guide the air and the function to support the left case, the right case and the separator when they are assembled, so as to improve assemblability and intensity. 
     The air passing the evaporator tends to move straight approximately in the horizontal direction. Because the extension line of the end portion of the streamlined surface  321  formed on the fourth guide unit  320  is formed side by side with the vent door  122 , in the vent mode, the air passing the evaporator  102  is directly guided to the face vent  117  so as to increase the air volume toward the face vent  117 . 
     In more detail, referring to  FIG. 13 , the third guide unit  310  is formed to be closer to the face vent  117  than an extension line (L 1 ) of the heat exchanger support part  225 . That is, the third guide unit  310  is located between the extension line (L 1 ) of the upper heat exchanger support part  225  of the heater core  103  and the extension line (L 2 ) of the fourth guide unit  320 . Moreover, the fourth guide unit  320  extends from a temperature door seating part  228  to the upper heat exchanger support part  225 . The fourth guide unit  320  is arranged above or in front of the heater core  103 . 
     Through the above configuration, the warm air of the warm air passage can be guided smoothly toward the defrost vent  116 . In this instance, because the third guide unit  310  is located between the extension line (L 1 ) of the heat exchanger support part  225  on the upper portion of the heater core  103  and the extension line (L 2 ) of the fourth guide unit  320 , the third guide unit  310  is located above the extension line (L 1 ) to fully perform its guide function toward the defrost vent  116 , and the fourth guide unit  320  prevents a drop of the air volume by the third guide unit  310  to secure sufficient air volume in the vent mode. 
     Additionally, compared with the structure that the third guide unit  310  is located below the extension line (L 1 ) of the heat exchanger support part  225  on the upper portion of the heater core  103 , even though there is no additional means, such as a hot channel, the third guide unit and the fourth guide unit can sufficiently guide the air toward the defrost vent  116 . 
       FIG. 15  is an enlarged perspective view illustrating a third guide unit and the inside of the air conditioning case according to the second preferred embodiment of the present invention, and  FIG. 16  is a sectional view taken along the line A-A of  FIG. 15 . 
     Referring to  FIGS. 15 and 16 , the air conditioning case  110  has a surface rib formed on the outer face thereof. The surface rib protrudes from the outer face of the air conditioning case  110  to reinforce rigidity of the air conditioning case  110 . The third guide unit  310  is formed on the inner wall surface of the air conditioning case  110  to correspond to the surface rib of the air conditioning case  110  to perform a guide function and a rigidity reinforcing function. 
     In more detail, at least one inclined part  110   a  is formed on the inner wall surface of the air conditioning case  110 . The air conditioning case  110  protrudes in the form of the surface rib by the inclined part  110   a.  The third guide unit  310  extends in contact with the inclined part  110   a.  That is, a straight part  212  and the curved part  311  of the third guide unit  310  come into contact with the inclined part  110   a  of the air conditioning case  110  and extends inwards integrally from the air conditioning case  110 . 
       FIG. 17  is a view illustrating a vent mode of the air conditioner for a vehicle according to the second preferred embodiment of the present invention. 
     Referring to  FIG. 17 , in the vent mode, the first temperature door  111  and the second temperature door  112  respectively close the upper warm air passage and the lower warm air passage. Moreover, the console door  124  opens the console vent  119 . The floor door  123  closes the floor vent  118 . The cold air of the upper passage  141  passing the evaporator  102  bypasses the heater core  103 , passes the upper cold air passage, and then, is discharged to the interior through the face vent  117 . The cold air of the lower passage  142  passes the lower cold air passage, and then, is discharged to the interior through the console vent  119 . 
     In this instance, the cold air passing the evaporator  102  is directly guided to the face vent  117  by the streamlined surface  321  of the fourth guide unit  320  to increase the air volume of the face vent  117 . 
       FIG. 18  is a view illustrating a floor mode of the air conditioner for a vehicle according to the second preferred embodiment of the present invention. 
     Referring to  FIG. 18 , in the floor mode, the first temperature door  111  and the second temperature door  112  respectively close the upper cold air passage and the lower cold air passage. Moreover, the console door  124  closes the console vent  119 , and the floor door  123  opens the floor vent  118 . The warm air of the upper passage  141  passing the heater core  103  after passing the evaporator  102  passes the warm air passage, and then, is discharged to the interior through the defrost vent  116 . The warm air of the lower passage  142  passing the heater core  103  after passing the evaporator  102  passes the lower warm air passage, and then, is discharged to the interior through the floor vent  118 . 
     In this instance, the warm air passing the heater core  103  is directly guided to the defrost vent  116  by the curved part  311  of the third guide unit  310  to increase discharge temperature of the defrost vent  116 . 
       FIG. 19  is a view illustrating a mixing mode of the air conditioner for a vehicle according to the second preferred embodiment of the present invention. 
     Referring to  FIG. 19 , in the mixing mode, the first temperature door  111  opens all of the upper warm air passage and the upper cold air passage, and the second temperature door  112  opens all of the lower warm air passage and the lower cold air passage. The console door  124  opens the console vent  119 . The floor door  123  opens the floor vent  118 . 
     Some of the air of the upper passage  141  passing the evaporator  102  bypasses the heater core  103  and passes the upper cold air passage. The other of the air passes the upper warm air passage after passing the heater core  103 , and then, is discharged to the interior through the face vent  117  or the defrost vent  116 . Some of the air of the lower passage  142  passing the evaporator  102  bypasses the heater core  103  and passes the lower cold air passage. The other of the air passes the lower warm air passage after passing the heater core  103 , and then, is discharged to the interior through the floor vent  118  and the console vent  119 . 
     In this instance, the cold air passing the evaporator  102  is directly guided to the face vent  117  by the streamlined surface  321  of the fourth guide unit  320  to increase the air volume of the face vent  117 . Moreover, the warm air passing the heater core  103  is directly guided to the defrost vent  116  by the curved part  311  of the third guide unit  310  to raise discharge temperature of the defrost vent  116 . 
     Furthermore, the mixing zone between the cold air passing the evaporator  102  and the warm air passing the heater core  103  is moved toward the defrost vent  116  so that the mixing area between the cold air and the warm air in the air conditioning case is increased, and the cold air and the warm air are not directly discharged to the face vent  117  but stay in the mixing zone for a long time so as to improve mixing performance. 
     As previously described, in the detailed description of the invention, having described the detailed exemplary embodiments of the invention, it should be apparent that modifications and variations can be made by persons skilled without deviating from the spirit or scope of the invention. Therefore, it is to be understood that the foregoing is illustrative of the present invention and is not to be construed as limited to the specific embodiments disclosed, and that modifications to the disclosed embodiments, as well as other embodiments, are intended to be included within the scope of the appended claims and their equivalents.