Cooling unit and drain case for air conditioners

A drain case 4 is disposed between the bottom wall of a unit case and the lower end of refrigerant passage pipes 15 of a stacked type refrigerant evaporator. The drain case 4 is W-shape in cross section, and comprising two pieces of outside inclined walls 32 contacting the side ends of two pieces of tank parts 16 and 17 formed at the lower end side of the refrigerant passage pipes 15, a chevron type protruded wall 33 contacting a recessed part 28 formed at the bottom end of the part between the adjacent two pieces of tank parts 16 and 17, and inside inclined walls 34 having a drain hole 36. In this arrangement, the condensed water flows from the side ends of the two pieces of tank parts 16 and 17 and the part between the two pieces of tank part 16 and 17 into the lower ends thereof reaches the two pieces of outside inclined walls 32 and protruded wall 33 of the drain case 4 before reaching the bottom end of the two pieces of tank parts 16 and 17, and then is efficiently drained therefrom. Localized corrosion that may occur at the lower end part of refrigerant passage pipes is prevented by not allowing the condensed water to stay at the lower end side of the refrigerant passage pipes.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention generally relates to such a cooling unit for air 
conditioners that is furnished with a drain case suitable for efficiently 
draining the condensed water generated on the surface of a refrigerant 
evaporator housed within a unit case, by way of examples. More 
particularly, the present invention is related to the drain case for the 
cooling unit for air conditioners. 
2. Description of the Related Art 
As illustrated in FIGS. 26 and 27, there has conventionally been an air 
conditioner which houses a refrigerant evaporator 102 within a recessed 
part 101 of a unit case 100 serving as a duct for sending the air into a 
vehicle compartment. In this air conditioner, a drain port 103 is formed 
at the bottom wall part of the recessed part 101, which drain port 103 
being opened under the refrigerant evaporator 102, to drain the condensed 
water adhered to the surface of the refrigerant evaporator 102 from the 
unit case 100 to outside. 
On the other hand, as illustrated in FIG. 28, the refrigerant evaporator 
102 has been composed by stacking a plurality of plural pairs of formed 
plates 106 with which refrigerant passage pipes 104 and two pieces of tank 
parts 105 are integrally formed at the end part side of the refrigerant 
passage pipes 104. A core part 107 of the refrigerant evaporator 102 is so 
composed that fins 108 are disposed between the adjacent refrigerant 
passage pipes 104. 
The air side heat transmission surface of the refrigerant evaporator 102 
(the surface to which the condensed water adheres) is formed from the 
surfaces of the fins 108 and the surfaces of the refrigerant passage pipes 
104. As illustrated in FIG. 29, the condensed water adhered to the surface 
of the fins 108 flows along the fins 108 to the side of the refrigerant 
passage pipes 104. On the other hand, as illustrated in FIG. 30, a 
plurality of inclined ribs 109 are formed in the protruded state at the 
inside of the refrigerant passage pipes 104 (in the recessed state at the 
air side heat transmission surface) to improve the heat transmission 
efficiency. The condensed water flows along the inclined ribs 109 to the 
lower end side of the core part 107. Based on the principle of draining 
the condensed water as described in the above, the condensed water adhered 
to the surfaces of the fins 108 and refrigerant passage pipes 104 is 
drained to the lower end side of the core part 107. Incidentally, a folded 
part 113 prevents the fins 108 from buckling. 
There are two types of surface treatments for refrigerant passage pipes 104 
formed by a pair of plates 106 and the fins 108; one is hydrophilic 
treatment, and the other is water repellent treatment. Hitherto, the 
hydrophilic treatment has generally been employed for two reasons; there 
has been no water repellent treatment liquid which can withstand the 
operational environment of the refrigerant evaporator 102, and when the 
water repellent treatment is applied to the surface of the refrigerant 
passage pipes 104 and fins 108, water drops are generated on the surfaces 
of the refrigerant passage pipes 104 and fins 108. As illustrated in FIG. 
31, when the fins 108 are provided with louvers 110, the water drops may 
be repelled by and between the louvers 110 and stay there or may not flow 
downwards from the surfaces of the fins 108 but may splash towards the lee 
side of the unit case 100. 
When the hydrophilic treatment is applied to the surfaces of the 
refrigerant passage pipes 104 and fins 108, water films are formed on the 
surfaces of the refrigerant passage pipes 104 and fins 108, which serves 
to supplement the above-described draining principle. As a result, there 
is no excessive stay of the condensed water, though a water film of 
approximately 0.1 mm in thickness is formed at the upper end side of the 
core part 107 due to the effects of the hydrophilic treatment. In the 
refrigerant evaporator 102 including two pieces of tank parts 105 as 
illustrated in FIG. 26 at the upper end side of each refrigerant passage 
pipe, even if the condensed water stays at the lower end part of the 
refrigerant passage pipes 104, corrosion which may occur at the lower end 
side of the refrigerant passage pipes 104 is not so significant due to the 
effects of the sacrificially corroded fins 108. 
However, in the refrigerant evaporator 102 in which two pieces of tank 
parts 105 illustrated in FIG. 27 are formed at the lower end side of the 
refrigerant passage pipes 104, as there is no fin 108 provided at the 
lower end side of the refrigerant passage pipes 104 where the condensed 
water stays, there would be no effect of the sacrificially corroded fins 
108. For this reason, localized corrosion which may occur at the lower end 
side of the refrigerant passage pipes 104 due to the stay of the condensed 
water is importantly pointed out. 
In other words, as illustrated in FIGS. 32 and 33, at the lower end side of 
the core part 107 or tank parts 105 of the conventional refrigerant 
evaporator 102, there has been a problem that the drainage of the 
condensed water adhered to the surfaces of the refrigerant passage pipes 
104 and fins 108 is so low that the condensed water stays there. 
Furthermore, when the refrigerant evaporator 102 in this arrangement is 
inserted into the unit case 100, the drainage of the refrigerant 
evaporator 102 is worsened by the water contained in an insulator 111 
disposed between the unit case 100 and the lower end part of the 
refrigerant evaporator 102, by way of examples. 
The reason for the above is, as illustrated in FIG. 34, the condensed water 
flowed from the lee side end part A of the lower end parts of the two 
pieces of tank parts 105 easily flows along the unit case 100 into a drain 
port 103, while the condensed water flowed from the windward side end part 
B of the lower end parts of the two pieces of tank parts 105 bridges the 
clearance between the lower end parts of the tank parts 105 and the 
insulator 111 and stays there (water stay part 112). 
When the condensed water flowed from the lower end part center C between 
the two pieces of tank parts 105 flows to the windward side end part B 
side of the lower end parts of the two pieces of tank parts 105, the 
condensed water joins the water drops in bridging and is held at the stay 
part 112. Alternatively, when the same condensed water flows to the lee 
side end part A side of the lower end parts of the two pieces of tank 
parts 105, the condensed water stays at the stay part 114 due to no 
guiding means available into which the condensed water falls. 
In the water drops staying at the stay parts 112 and 114, (water retention 
force due to surface treatment)+(structural difficulty in dropping of 
water drops)&gt;(gravity on water drops) is established. Therefore, the water 
drops are held at the stay parts 112 and 114, and drops downwards as the 
water drops grow. 
As described in the above, in the refrigerant evaporator 102 in which the 
two pieces of tanks 105 are formed at the lower end side of the 
refrigerant passage pipes 105, there has been a problem that the condensed 
water easily stays and localized corrosion is easily occur at the lower 
end side of the refrigerant passage pipes 104 where corrosive elements 
(Cl, NOx, etc.) in the atmosphere are easily condensed. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a cooling unit and drain 
case for an air conditioner which can prevent localized corrosion which 
may occur at the lower end side of refrigerant passage pipes of a 
refrigerant evaporator with mainly two pieces of tank parts formed at the 
lower end side of the refrigerant passage pipes by preventing the stay of 
the condensed water at the lower end side of the refrigerant passage 
pipes. 
A preferable embodiment of the present invention employs a technical means 
including a plurality of stacked refrigerant passage pipes with two pieces 
of tank parts formed at the lower end side of the refrigerant passage 
pipes, a refrigerant evaporator composed of fins disposed between the 
adjacent refrigerant passages, a windward side inclined parts contacting 
the windward side end parts of the two pieces of tank parts, lee side 
inclined parts contacting the lee side end parts of the two pieces of the 
tank parts, a protruded part contacting the lower end part of the part 
between the two pieces of tank parts, and a drain case with a drain hole 
for draining the condensed water generated by the refrigerant evaporator. 
The drain case may be composed of two pieces of side wall parts contacting 
the windward side ends and lee side ends of the two pieces of tank parts, 
two pieces of outside inclined walls forming the windward side inclined 
parts and lee side inclined parts, a chevron type protruded wall 
contacting the lower end part of the part between the two pieces of tank 
parts and forming the protruded part, and two pieces of inside inclined 
walls connecting the two pieces of outside inclined walls and the 
protruded wall. Furthermore, the drain hole may be made at the inside 
inclined wall. 
The drain case may also be composed of two pieces of side wall parts 
contacting the windward side ends and lee side end of the two pieces of 
tank parts, two pieces of inclined walls forming the windward side 
inclined parts and the lee side inclined parts, and a pillar type wall 
extended upwards from the connecting part of the inclined walls, 
contacting the lower end part of the part between the two pieces of tank 
parts and forming the protruded part. 
Furthermore, the drain case may also be composed of two side walls 
contacting the windward side ends and lee side ends of the two pieces of 
tank parts, two inclined walls forming the windward side inclined parts 
and the lee side inclined parts, the bottom wall part connecting the 
bottom ends of these inclined walls to each other and separated from the 
lower end parts of the two pieces of tank parts by the specified distance, 
and a pillar type wall extended upwards from the center of this bottom 
wall, contacting the lower end part of the part between the two pieces of 
tank parts and forming the protruded part. The drain hole may also be made 
at the bottom wall part. 
Hydrophilic treatment may be applied to the formed plate and fins of the 
refrigerant evaporator. The bottom ends of the presence of the fins 
between the adjacent formed plates may be disposed under the upper end of 
the drain case. Furthermore, an engagement part for positioning the drain 
case may be provided in the unit case by disposing the drain case between 
the lower end of the refrigerant evaporator and the bottom wall of the 
unit case. 
The present invention in preferred mode employs a technical means including 
a refrigerant evaporator with tank parts bulged outwards from the other 
parts at the lower end side of refrigerant passage pipes to the surfaces 
of which hydrophilic treatment is applied, and a unit case having a drain 
port for draining the condensed water under the refrigerant evaporator, 
whereas either of the refrigerant evaporator or the unit case has a 
guiding means for guiding the condensed water from the bottom ends of the 
tank parts or the side ends of the tank parts into the drain port. 
The present invention in another preferred mode employs a drain case 
disposed under a refrigerant evaporator composed of plural pairs of formed 
plates forming two pieces of tank pars at the lower end side of the 
refrigerant passage pipes to drain the condensed water generated by the 
refrigerant evaporator, and employs a technical means including windward 
side inclined parts contacting the windward side end parts of the two 
pieces of tank parts, lee side inclined parts contacting the lee side 
parts of the two pieces of tank parts, a protruded part contacting the 
lower end part of the part between the two pieces of tank parts, and a 
drain hole for draining the condensed water generated by the refrigerant 
evaporator. 
The condensed water generated on the surface of the refrigerant evaporator 
with the two tank parts formed at the lower end of the refrigerant passage 
pipe falls due to gravity to the windward side end parts of the two pieces 
of tank parts, to the lee side end parts of the two pieces of tank parts, 
and to the lower end part of the part between the two pieces of tank 
parts. The condensed water reached the windward side end parts of the two 
pieces of tank parts flows along the windward side inclined parts into the 
drain case and then is drained from the drain hole. The condensed water 
reached the lee side end parts of the two pieces of tank parts flows along 
the lee side inclined parts into the drain case and then is drained from 
the drain hole. Furthermore, the condensed water reached the lower end of 
the part between the two pieces of tank parts flows along the protruded 
part into the drain case and then is drained from the drain hole. In this 
arrangement, the condensed water can not stay at the bottom ends of the 
two pieces of tank parts, and therefore localized corrosion which may 
occur at the lower end side of the refrigerant passage pipes can be 
prevented. 
In other preferred mode in the present invention, the condensed water 
generated on the surface of the refrigerant evaporator with the tank parts 
formed at the lower end side of the refrigerant passage pipes provided 
with hydrophilic treatment falls due to gravity. Then, the condensed water 
flows from the bottom end or side ends of the tank parts into the guiding 
means and then is drained into the drain port of the unit case. In this 
arrangement, the condensed water can not stay at the bottom end of the 
tank parts, and therefore localized corrosion which may occur at the lower 
end side of the refrigerant passage pipes can be prevented.

DETAILED DESCRIPTION OF THE EMBODIMENTS 
A plurality of preferred embodiments of a cooling unit for air conditioners 
according to the present invention will now be described with reference to 
FIGS. 1 to 26 inclusive. 
[Composition of the First Embodiment] 
FIGS. 1 to 4 illustrate the structure of the first embodiment according to 
the present invention, whereas FIG. 1 illustrates a cooling unit for air 
conditioners for use in automobiles. The cooling unit 1 is provided with a 
unit case 2 constituting a duct for leading the air into the vehicle 
compartment, a stacked type refrigerant evaporator 3 for cooling the air 
flowing through the unit case 2, and a drain case 4 disposed between the 
unit case 2 and the stacked type refrigerant evaporator 3. 
The unit case 2 is cylindrically shaped, made of polypropylene (PP), for 
example, and has a top wall 5 recessed upwards at the top part and a 
bottom wall 6 recessed downwards and at the bottom part facing the top 
wall 5. The bottom wall 6 is inclined downwards with respect to the 
horizontal direction, and includes a drain port 7 at the bottom part 
thereof for draining the condensed water from the inside of the unit case 
2 to the outside thereof. 
FIG. 2 illustrates the stacked type refrigerant evaporator 3, while FIG. 3 
illustrates the stacked type refrigerant evaporator 3 and the drain case 
4. The stacked type refrigerant evaporator 3 comprises a joint block 8 for 
the connection thereof to the downstream side of an expansion valve (not 
illustrated) and also for the connection thereof to a refrigerant 
compressor (not illustrated), a refrigerant-refrigerant heat exchange part 
9 for making heat exchange between two different flows of the refrigerant, 
a refrigerant-air heat exchange part 10 for making heat exchange between 
the refrigerant and the air, and a pressure reducing part (not 
illustrated) disposed between the refrigerant-refrigerant heat exchange 
part 9 and the refrigerant-air heat exchange part 10. 
The joint block 8 includes an inflow port 11 for permitting the refrigerant 
in the gas-liquid two phase state flowed out of the expansion valve to 
flow into the inside of the stacked type refrigerant evaporator 3, and an 
outflow port 12 for permitting the refrigerant to flow from the stacked 
type refrigerant evaporator 3 to the refrigerant compressor side after 
being subjected to heat exchange. 
The refrigerant-refrigerant heat exchange part 9 comprises a plurality of 
stacks of refrigerant passage pipes 13, each of which being composed of a 
pair of thin flat formed plates formed by brazing or other means, and the 
surfaces of the pair of formed plates are coated with a precoat material 
(C513), a hydrophilic polymeric material or a hydrophilic porous material 
as a hydrophilic treatment. 
The inside of the refrigerant-refrigerant heat exchange part 9 is so formed 
that an inlet side refrigerant passage (not illustrated) for feeding the 
refrigerant from the inflow port 11 to the refrigerant-air heat exchange 
part 10 and an outlet side refrigerant passage (not illustrated) for 
feeding the refrigerant from the refrigerant-air heat exchange part 10 
into the outflow port 12 meander therethrough. The inlet side refrigerant 
passage and the outlet side refrigerant passage are disposed in proximity 
to each other over the specified distance so that heat exchange can be 
made between the refrigerant flowing through the inlet side refrigerant 
passage and the refrigerant flowing through the outlet side refrigerant 
passage. 
The refrigerant-air heat exchange part 10 comprises a plurality of stacks 
of corrugated fins 14 and refrigerant passage pipes 15, whereas the 
corrugate fins 15 function for improving the refrigerant-air heat exchange 
efficiency and the refrigerant passage pipes 15 are formed by brazing or 
other means. The surfaces of the corrugated fins 14 and the pair of formed 
plates are coated with a precoat material (C513), a hydrophilic polymeric 
material or a hydrophilic porous material as a hydrophilic treatment. 
As partly illustrated in FIG. 4, the formed plate forming the refrigerant 
passage pipe 15 is formed by pressing a thin aluminum alloy plate. A tank 
part 16 is formed on the windward at the lower end of the refrigerant 
passage pipe 15, while a tank part 17 is formed on the lee side at the 
lower end of the refrigerant passage pipe 15. The two pieces of tank parts 
16 and 17 formed at the lower ends of the refrigerant passage pipes 15 are 
connected with each other through a roughly U-shaped refrigerant 
evaporation passage 18 formed thereabove, and bulged to be roughly 
bowl-shaped in the direction of stacking so as to be joined by brazing or 
other means at the lower ends of the adjacent refrigerant passage pipes 
15. Furthermore, link holes 19 and 20 which are roughly elliptic are 
formed at the two pieces of tank parts 16 and 17 to link the two pieces of 
tank parts 16 and 17 to the adjacent refrigerant passage pipes 15. 
The refrigerant evaporation passage 18 of a plurality of the refrigerant 
passage pipes. 15 form a core part 21 of the stacked type refrigerant 
evaporator 3 together with a plurality of the corrugated fins 14. The 
refrigerant evaporation passage 18 includes a numerosity of inclined ribs 
22 which are formed so as to protrude towards the inside thereof. On the 
other hand, joint walls 23 and 24 are formed at the central part and outer 
periphery of the refrigerant passage pipes 15 so as to protrude towards 
the inside thereof as a means for joining the pair of formed plates to 
each other by brazing or other means. Furthermore, a fold part 25 for 
preventing the buckling of the corrugated fins 14 extends from the top end 
of one of the pairs of formed plates in the direction of stacking of the 
refrigerant passage pipes 15. 
The drain case 4 is a guiding means according to the present invention. As 
illustrated in FIGS. 3 and 4, the drain case 4 is made of PP, for example, 
and W-shaped in cross sectional, and disposed between the bottom wall 6 of 
the unit case 2 and the lower end of the stacked type refrigerant 
evaporator 3. This drain case 4 is designed to guide the condensed water 
generated over the surface of the stacked type refrigerant evaporator 3 
from the bottom end center of the refrigerant passage pipes 15 (13) and 
the side ends of the two tank parts 16 and 17 (the windward side end and 
lee side end of the stacked type refrigerant evaporator 3) into the drain 
port 7 of the unit case 2. 
This drain case 4 comprises two pieces of side wall parts 31, two pieces of 
outside inclined walls 32, a chevron type protruded wall 33, two pieces of 
inside inclined walls 34, and two pieces of closing wall 35 for closing 
the width ends of these walls 31, 32, 33 and 34. The two pieces of side 
walls 31 are arc-shaped in cross section, and serves as a means for 
preventing air leakage at the lower end of the stacked type refrigerant 
evaporator 3 by closing the side ends of the two pieces of tank parts 16 
and 17 formed at the lower end of the refrigerant passage pipes 15 (13). 
The inside surfaces of the two pieces of side wall parts 31 contact the 
side ends of the two pieces of tank parts 16 and 17, and the outside 
surfaces thereof contact the inside surfaces of the bottom wall 6 of the 
unit case 2. 
In the two pieces of outside inclined walls 32, the outside inclined wall 
32 on the windward is a side inclined part on the windward according to 
the present invention, while the other outside inclined wall 32 on the lee 
is a side inclined part on the lee according to the present invention. The 
two pieces of outside inclined walls 32 are inclined downwards from the 
lower ends of the two pieces of side wall parts 31, and the bottom ends 
thereof contact the bottom surface of the bottom wall 6 of the unit case 
2. The protruded wall 33 is a protruded wall according to the present 
invention, and contacts a squarely recessed part 28 formed at the central 
bottom end of the refrigerant passage pipe 15 (13). The recessed part 28 
is formed at the bottom end of the part between the adjacent two pieces of 
tank parts 16 and 17. The two pieces of inside inclined walls 34 are parts 
connecting the outside inclined walls 32 and the protruded wall 33, and 
include drain ports 36 respectively. The drain ports 36 are drain ports 
according to the present invention, and formed so as to be inclined and 
open at the bottom end of the drain case 4. 
[Mode of Operation of the First Embodiment] 
The mode of operation of the first embodiment will now be described 
referring to FIGS. 1 to 6. FIG. 4 illustrates the principle of draining 
the condensed water according to an art in which the drain case 4 is 
contacted to the lower end of the stacked type refrigerant evaporator 
(first embodiment). FIG. 5 illustrates the principle of draining the 
condensed water according to an art in which the drain case 4 is not 
disposed at the lower end of the stacked type refrigerant evaporator 3 
(first comparative example). FIG. 6 illustrates the principle of draining 
the condensed water according to an art in which a conventional unit case 
100 is disposed under the stacked type refrigerant evaporator 3 (second 
comparative example). 
The stacked type refrigerant evaporator 3 with the surfaces of the 
corrugated fins 14 and refrigerant passage 15 provided with hydrophilic 
treatment cools the air by having the air flowing through the unit case 2 
and the refrigerant flowing through the refrigerant passage pipe 15 make 
heat exchange with each other. When the air is cooled by the stacked type 
refrigerant evaporator 3 to be below the dew point, the moisture contained 
in the air is condensed and adheres to the surfaces of the corrugated fins 
14 and refrigerant passage pipe 15, forming a water film of approximately 
0.1 mm thick over the surfaces. 
The condensed water adhered to the surfaces of the corrugated fins 14 flows 
along the corrugated fins 14 to the refrigerant passage pipe 15, while the 
condensed water adhered to the surfaces of the refrigerant passage pipe 15 
falls along the inclined ribs 22 and the joint walls 23 and 24, both of 
which being recessed from the other part of the refrigerant passage pipes. 
In the case of the first comparative example as illustrated in FIG. 5, the 
condensed water flowed from the side ends of the two pieces of tank parts 
16 and 17 of the refrigerant passage pipes 15 and from between the two 
pieces of tank parts 16 and 17 into the lower end sides of the two pieces 
of tank parts 16 and 17 stays at the lower ends A and B (horizontal parts) 
of the two pieces of tank parts 16 and 17, due to no drain case 4 or 
guiding means available therefrom. 
In the case of the second comparative example as illustrated in FIG. 6, the 
condensed water flowed from the side end of the tank part 17 into the 
lower end side thereof easily flows along the bottom wall of the unit case 
100, while the condensed water flowed from the side end of the tank part 
16 bridges the clearance between the tank part 16 and an insulator 111 in 
a form of water drops, and, as a result, stays at the lower end A 
(horizontal part) of the tank part 16. When the condensed water flowed 
from between the two pieces of tank parts 16 and 17 into the lower end 
side of the tank parts 16 and 17 flows into the lower end side of the tank 
part 16, the condensed water joins the bridging water drops and stays 
there being held by the bridging water drops. When the condensed water 
flowed into the lower end side of the tank 17, the condensed water stays 
at the lower end B (horizontal part) of the tank part 16, due to no 
guiding means available therefrom. 
In contrast with the above examples, when the drain case 4 which is W-shape 
in cross section is arranged so as to contact the lower end of a plurality 
of the refrigerant passage pipes 15, as illustrated in FIG. 4, the 
condensed water flowed from the side end of the tank part 16 and the side 
end of the tank part 17 flows to the side wall parts 31 of the drain case 
4 before reaching the lower ends of the tank parts 16 and 17, and guided 
from the side wall parts 31 to the outside inclined walls 32, to the drain 
holes 36, to the bottom wall 6, and then to the drain port 7, and then 
efficiently drained therefrom. 
The condensed water flowed from between the lower ends of the two pieces of 
tank parts 16 and 17 into the lower end sides of the tank parts 16 and 17 
flows to the protruded wall 33 of the drain case 4 before reaching the 
lower ends of the tank parts 16 and 17, and is guided from the protruded 
wall 33 to the inside inclined wall 34, to the drain holes 36, to the 
bottom wall 6, and to the drain port 7, and then efficiently drained 
therefrom. 
[Effect of the First Embodiment] 
FIGS. 7 and 8 illustrates experimental data of (water retention 
amount)/(surface area) at each part of the first and second comparative 
examples in the vertical direction. It can be understood from FIG. 7 that, 
in the first comparative example, there is the localized stay of the 
condensed water at the lower ends A and B of the tank parts 16 and 17. In 
contrast, it can be understood from FIG. 8 that, in the second comparative 
example, the localized stay of the condensed water is restrained, and 
therefore, the localized corrosion that may be caused to the lower end 
side of the refrigerant passage pipes 15 (13) due to some corrosive 
elements (Cl, NOx, etc.) can be restrained. 
[Composition of the Second Embodiment] 
FIGS. 9 and 10 illustrate the structure of the second embodiment according 
to the present invention, particularly the structure of the stacked type 
refrigerant evaporator and drain case thereof. 
Round through holes 19 and 20 are formed in the two pieces of tank parts 16 
and 17 formed at the lower end side of formed plate composing the 
refrigerant passage pipes 15 of the stacked type refrigerant evaporator 3 
of this embodiment to link the two pieces of tank parts 16 and 17 to the 
adjacent refrigerant passage pipes 15. The corrugated fins 14 disposed 
between the adjacent refrigerant passage pipes 15 are joined from the 
upper ends of the two pieces of tank parts 16 and 17 to the upper sides 
thereof by brazing or other means as illustrated by an alternate long and 
short dash line in FIG. 10. 
The drain case 4 of this embodiment is disposed between the bottom wall 6 
of the unit case 2 and the lower end of the stacked type refrigerant 
evaporator 3 through an insulator 73 made of styrene paper or PE-lite. 
This drain case 4 comprises two pieces of upright wall parts 74 disposed in 
parallel with each other, two pieces of arc walls 75 inclined downwards 
from the upright walls 74 respectively, a comparatively long protruded 
wall 76 contacting groove parts 29 formed at the central bottom end of the 
refrigerant passage pipes 15 (13), two rows of bottom walls 77 connecting 
the arc walls 75 and the protruded wall 76 respectively, and closing walls 
78 for closing the width ends of these walls 74, 75, 76 and 77. 
The outside surfaces of the two pieces of upright wall parts 74 are in 
contact with the inside surface of the bottom wall 6 of the unit case 2. 
The two pieces of arc walls 75 are in closure with the side ends of the 
two pieces of tank parts 16 and 17 formed at the lower end of the 
refrigerant passage pipes 15 (13). Two rows of edge parts 80 spherical in 
cross section are formed at the rear surface of the two pieces of arc 
walls 75 to protect the insulator 73 from damage. The two rows of edge 
parts 80 are caulked against positioning grooves 79 formed at the bottom 
wall 6 of the unit case 2. 
These edge parts 80 is designed to position the stacked type refrigerant 
evaporator 3 and the drain case 4 to the unit case 2 and also to prevent 
air leakage at the lower end side of the stacked type refrigerant 
evaporator 3. Drain passages 81 are formed between the lower end of the 
stacked type refrigerant evaporator 3 and bottom walls 77 to drain the 
condensed water. Furthermore, a plurality of drain holes 82 are 
longitudinally arranged in parallel with each other at the two rows of 
bottom walls 77 to drain the condensed water to the top of the bottom wall 
6 of the unit case 2. 
[Mode of Operation of the Second Embodiment] 
The effect of this embodiment will now be described referring to FIGS. 9 
and 10. The condensed water adhered to the surfaces of the refrigerant 
passage pipes 15 (13) and corrugated fins 14 of the stacked type 
refrigerant evaporator 3 flows through the inclined ribs 22, converges at 
the joint walls 23 and 24, and then flows downwards. The condensed water 
flowed from the side ends of the tank parts 16 and 17 into the lower end 
sides thereof reaches the arc walls 75 of the drain case 4 before reaching 
the lower ends of the tank parts 16 and 17. Then, the condensed water is 
guided from the arc walls 75 to the bottom walls 77, to the drain holes 
82, to the bottom wall 6 (insulator 73) and to the drain port 7, and then 
efficiently drained therefrom. 
The condensed water flowed from the two pieces of tank parts 16 and 17 into 
the lower end sides of the tank parts 16 and 17 reaches the protruded wall 
76 of the drain case 4 before reaching the lower ends of the tank parts 16 
and 17. Then, the condensed water is guided from the projected wall 76 to 
the bottom walls 77, to the drain holes 82, to the bottom wall 6 
(insulator 73) and to the drain port 7, and then efficiently drained 
therefrom. 
[Effect of the Second Embodiment] 
As illustrated in FIG. 11, the shape of the drain case 4 of the first 
embodiment requires the formation of a drain passage 83 under the stacked 
type refrigerant evaporator 3, This arrangement, however, may make the 
whole system of the cooling unit 1 bulky, and furthermore, make the 
insulator 73 disposed between the drain case 4 and the bottom wall 6 of 
the unit case 2 exposed to the danger of being damaged due to an 
acute-angle edge part 84. 
As opposed to the above, this embodiment can protect the insulator 73 from 
damage or fracture by forming the edge parts 80 spherical (obtuse-angle). 
Furthermore, the lower end of the presence range of the corrugated fins 14, 
which are to be present between the adjacent refrigerant passage pipes 15, 
is positioned lower than the upper end surface of the two pieces of 
upright walls 74 of the drain case 4 and the end surfaces of the lower 
walls 2a. In this arrangement, the air flowing through the unit case 2 is 
guided to the above side of the stacked type refrigerant evaporator 3 
comparatively easily, and there is a little air which flows through a 
clearance between the lower end of the stacked type refrigerant evaporator 
3 and the drain case 4 and leaks without being subjected to heat exchange. 
[Third Embodiment] 
FIG. 12 illustrates the structure of the third embodiment according to the 
present invention, particularly the structure of the stacked type 
refrigerant evaporator and drain case thereof. 
The drain case 4 of this embodiment comprises side wall parts 51 closing 
the side ends of two pieces of the tank parts 16 and 17 of the refrigerant 
passage pipes 15 respectively, two pieces of inclined walls 52 inclined 
downwards from the two pieces of side wall parts 51, and a pillar type 
wall 53 contacting the squarely recessed part 28 formed at the bottom end 
of the central part of the refrigerant passage pipes 15. 
[Fourth Embodiment] 
FIGS. 13 to 15 illustrate the structure of the fourth embodiment according 
to the present invention, whereas FIGS. 13 and 14 illustrate the stacked 
type refrigerant evaporator and drain case thereof. 
In this embodiment, groove parts 66 and 67 are formed by machining or other 
means at the outside inclined walls 32 and inside inclined walls 34 of the 
drain case 4 to collect the condensed water dropped from the stacked type 
refrigerant evaporator 3. As illustrated in FIG. 15, the groove parts 66 
and 67 are formed to be square in cross section. 
In this embodiment, even when the refrigerant compressor is in the OFF 
state or the switch of the air conditioner is in the OFF state, in other 
words, even when there is no generation of water drops on the drain case 
4, the water drops on the drain case 4 are collected into the groove parts 
66 and 67. As the water drops then are generated and guided through the 
drain holes 36 and along the bottom wall 6 into the drain port 7, this 
embodiment allows more efficient draining in comparison with the first 
embodiment. 
[Fifth Embodiment] 
FIG. 16 illustrates the structure of the fifth embodiment according to the 
present invention, particularly the structure of the drain case thereof. 
Gently inclined surfaces 68 are formed around the grooved parts 66 and 67 
of the drain case 4 of this embodiment. In this embodiment, in comparison 
with the fifth embodiment, water drops over the outside inclined walls 32 
and inside inclined walls 34 of a wider area of the drain case 4 can be 
collected into the groove parts 66 and 67. 
[Sixth Embodiment] 
FIG. 17 illustrates the structure of the sixth embodiment according to the 
present invention, particularly the structure of the drain case thereof. 
In this embodiment, flat parts 70 and a groove part 69, which is reverse 
trapezoidal in cross section and disposed between the flat parts 70, are 
formed at the outside inclined walls 32 and inside inclined walls 34 of 
the drain case. 
[Seventh Embodiment] 
FIG. 18 illustrates the structure of the seventh embodiment, particularly 
the structure of the stacked type refrigerant evaporator and drain case 
thereof. In this embodiment, groove parts 72 square in cross section are 
formed at the outside inclined walls 32 and inside inclined walls 34 of 
the drain case 4 along the brim parts 71 of the refrigerant passage pipes 
13 of the stacked type refrigerant evaporator 3. 
[Eighth Embodiment] 
FIGS. 19 and 20 illustrate the structure of the eighth embodiment according 
to the present invention, particularly the structure of the stacked type 
refrigerant evaporator and unit case thereof. The drain case 4 of this 
embodiment comprises the two pieces of upright walls 74 disposed in 
parallel with each other, the two pieces of arc walls 75 inclined 
downwards from the upright walls 74 respectively, the comparatively short 
projected wall 76 contacting the squarely recessed part 28 formed at the 
bottom end of the central part of the refrigerant passage pipes 15 (13), 
the two rows of bottom walls 77 connecting the arc walls 75 and the 
projected wall 76 respectively, and the closed walls 78 closing the width 
end parts of these walls 74, 75, 76 and 77. 
In this embodiment, in the same way as the second embodiment, as the edge 
part 80 is formed spherical (obtuse-angle) in cross section, the insulator 
73 is protected from damage or fracture. 
Furthermore, the drain case 4 can be lowered and hence the whole body of 
the cooling unit 1 can be downsized by narrowing the space of the drain 
passages 81 provided under the stacked type refrigerant evaporator 3 
without sacrificing the efficiency of draining the condensed water from 
the stacked type refrigerant evaporator 3. For the stacked type 
refrigerant evaporator provided with hydrophilic treatment, if the height 
of each drain passage, or a clearance a, is 3 mm or more, the condensed 
water will not stay between the stacked type refrigerant evaporator 3 and 
the drain case 4, which depends on the surface treatment agent though. 
[Ninth Embodiment] 
FIG. 21 illustrates the structure of the ninth embodiment according to the 
present invention, particularly the structure of the stacked type 
refrigerant and unit case thereof. Two pieces of bottom walls 85 of the 
drain case 4 of this embodiment have arc surfaces. 
[Tenth Embodiment] 
FIG. 22 illustrates the structure of the tenth embodiment according to the 
present invention, particularly the structure of the stacked type 
refrigerant and unit case thereof. A bottom wall 86 of the drain case 4 of 
this embodiment has an arc surface which gently connects the two pieces of 
arc walls 75. 
[Eleventh Embodiment] 
FIGS. 23 and 24 illustrate the structure of the eleventh embodiment 
according to the present invention, particularly the structure of the 
stacked type refrigerant evaporator and drain case thereof. 
The drain case 4 of this embodiment comprises two pieces of side walls 41 
closing the side ends of the two pieces of tank parts 16 and 17 for the 
refrigerant passage pipes 15 respectively of the stacked type refrigerant 
evaporator 3, two pieces of contact wall parts 42 contacting the bottom 
ends of the two pieces of tank parts 16 and 17 respectively, two pieces of 
inclined walls 43 inclined downwards from the inside end parts of the two 
pieces of contact wall parts 42 respectively, a bottom wall part 44 
separated by the specified distance from the bottom end of the refrigerant 
passage pipes 15, and two pieces of closing walls 45 closing the width end 
parts of these walls 42, 43 and 44. The inclined wall parts 43 and the 
bottom wall part 44 include a drain hole 46 to drain the condensed water 
to the top of the bottom wall 6 of the unit case 1. 
In this embodiment, as illustrated in FIG. 24, the condensed water flowed 
from the side ends of the tank parts 16 and 17 into the lower end side 
thereof reaches from the lower ends of the tank parts 16 and 17 to the 
contact wall parts 42, and is guided to the inclined wall parts 43, to the 
bottom wall part 44, to the drain hole 46 and to the drain port 7, and 
then drained therefrom. 
The condensed water flowed from between the two pieces of tank parts 16 and 
17 to the lower sides of the tank parts 16 and 17 joins the condensed 
water from the side ends flowed along the contact wall parts 42 of the 
drain case 4 before reaching the lower ends of the tank parts 16 and 17, 
and then flows into the inclined wall parts 43. 
[Twelfth Embodiment] 
FIG. 25 illustrates the structure of the twelfth embodiment according to 
the present invention, particularly the structure of the stacked type 
refrigerant evaporator and unit case thereof. 
In this embodiment, the bottom wall 6 of the unit case 2 is so transformed 
not to allow the condensed water to stay at the lower ends of the 
refrigerant passage pipes 15. The bottom wall 6 of the unit case 2 
comprises two pieces of arc side wall parts 61 closing the side ends of 
the two pieces of tank parts 16 and 17 respectively of the refrigerant 
passage pipes 15, two pieces of contact wall parts 62 contacting the 
bottom ends of the two pieces of tank parts 16 and 17 from the two pieces 
of side wall parts 61, two pieces of inclined wall parts 63 inclined 
downwards from the inside end part of these contact wall parts 62, and a 
bottom wall part 64 separated by the specified distance from the bottom 
end of the refrigerant passage pipes 15 and connecting the bottom ends of 
these inclined wall parts 63. 
[Modified embodiment] 
In this embodiment, the present invention is applied to the stacked type 
refrigerant evaporator 3 with the two pieces of tank parts 16 and 17 
formed at the lower end side of the refrigerant passage pipes 15. The 
present invention, however, may be applied to a refrigerant evaporator 
with three or more pieces of tank parts formed at the lower end of the 
refrigerant passage pipes. Alternatively, the present invention may also 
be applied to a refrigerant evaporator with a tank part formed on the 
upper end part of the refrigerant passage pipes, as well as at the lower 
end of the refrigerant passage pipes.