Air conditioning system for an automobile

An automobile air conditioning system including a fan unit for generating an air flow. The air flow is directed to the passenger compartment of the automobile through a first air duct which is provided downstream of the fan unit. A second air duct branches from the first air duct which extends over and in parallel to the first air duct. A filter is provided between the first and second air ducts for cleaning the air flow to the second air duct from the first air duct through the filter. Further, the air conditioning system is provided with means for selectively directing the air flow from the fan unit to the passenger compartment through the first air duct or through the first and second air ducts.

BACKGROUND OF THE INVENTION 
(1) Field of the Invention 
The invention relates to a duct arrangement for a filter, which is used in 
an automobile air conditioning system, for removing smells from the air. 
(2) Description of the Related Art 
Japanese Unexamined Patent Publication (Kokai) No. 57-172817 describes an 
automobile air conditioning system which comprises a deodorization filter 
for removing odors and dust from the air within the passenger compartment. 
The deodorization filter comprises an energized charcoal for removing 
odorous substances such as Nox and CH, which are contained in exhaust gas 
from automobiles and are introduced into the passenger compartment. In 
addition to the malodor, such substances are bad for the health of 
passengers within the passenger compartment. The deodorization filter is 
provided downstream of an evaporator within an air duct. A damper assembly 
is arranged within the air duct to switch the air between normal mode, in 
which the air from the evaporator directly distributed into the passenger 
compartment without passing through the deodorization filter, and 
deodorization mode, in which the air from the evaporator passes through 
the deodorization filter for removing the odorous substances. When the 
deodorization mode is selected, the air, which has passed through the 
evaporator, is directed to the deodorization filter. 
In the air system of JPP '817, the deodorization filter in the air duct 
hinders the air flow to increase the flow resistance during the normal 
mode, which results in decrease in the flow rate, increase in noise of the 
air flow, and increase in power consumption of the fan motor. 
Japanese Unexamined Patent Publications (Kokai) No. 4-271916 and No. 5-2718 
describe an automobile air conditioning system which comprises main and 
by-pass air ducts and a deodorization filter, which is provided in the 
by-pass air duct, for removing odors and dust from the air within the 
passenger compartment. Provided within the main air duct is a valve or a 
door for switching the air flow between the main and by-pass air ducts. 
The deodorization filter is provided within the by-pass air duct to be 
oriented substantially perpendicular to the direction air flow in the main 
air duct. Thus, the deodorization filter and the by-pass air duct which 
encloses the deodorization filter extend outwardly from the main air duct 
into the passenger compartment of the automobile. 
The invention is directed to solve the prior art problems described above, 
and to provide an air conditioning system improved to minimize the space 
required for installation as well as the flow resistance during the normal 
mode. 
SUMMARY OF THE INVENTION 
According to the invention, an automobile air conditioning system is 
provided. The air conditioning system includes a fan unit for generating 
an air flow. The air flow is directed to the passenger compartment of the 
automobile through a first air duct which is provided downstream of the 
fan unit. A second air duct branches from the first air duct which extends 
over and in parallel to the first air duct. A filter means is provided 
between the first and second air ducts for cleaning the air flow to the 
second air duct from the first air duct through the filter means. Further, 
the air conditioning system is provided with means for selectively 
directing the air flow from the fan unit to the passenger compartment 
through the first air duct or through the first and second air ducts. 
The air conditioning system can reduce the space required for installation 
in the automobile since the second air duct branches from the first air 
duct and extends over and in parallel to the first air duct. 
In another feature of the invention, the filter means comprises a 
deodorization filter which removes odorous substances in the air flow 
through the deodorization filter. Preferably, the deodorization filter is 
formed into a flat plate which extends substantially in a horizontal plane 
between the first and second air ducts. The horizontal placement of the 
deodorization filter between the first and second air ducts reduces the 
space required for installation of the air conditioning system. 
According to another feature of the invention, the air conditioning system 
includes means for directing the air flow from the fan unit to the 
passenger compartment through the first air duct or the first and second 
air duct. A normal mode of air conditioning is selected when the air flow 
is directed to the passenger compartment of the automobile through the 
first air duct. On the other hand, a deodorization mode of air 
conditioning is selected when the air flow is directed to the passenger 
compartment through the first and second air ducts. 
According to another feature of the invention, the fan unit includes a 
centrifugal fan, and a scroll casing which contains the centrifugal fan. 
The first air duct includes a bottom wall which faces the filter means. 
The bottom wall is formed substantially into a trapezoidal shape. The 
first air duct further includes a pair of side walls connected to the 
bottom wall along the oblique sides of the bottom wall. The oblique sides 
of the bottom wall symmetrically diverge in the downstream direction 
within the first air duct. The scroll casing includes an outer wall which 
extends spirally. The end of the outer wall is connected to the bottom 
wall at the top side of the trapezoid. The diverged bottom wall and the 
side walls of the first air duct minimize the pressure loss due the sudden 
expansion of the first air duct.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
With reference to FIGS. 1-8, the first embodiment of the invention will be 
described. 
FIG. 1 illustrates a partial section of an air conditioning system 
according to the first embodiment of the invention. The air conditioning 
system comprises a fan unit 1, an air conditioning unit 5, and a 
deodorization filter unit 6 between the fan unit 1 and the air 
conditioning unit 5. 
With reference to FIG. 5, the air conditioning system is mounted under a 
car dashboard 8 and, in particular, within a glove box. FIG. 5 is a 
schematic sectional illustration of the air conditioning system along line 
V--V in FIG. 1 with an automobile constitution around the system. In FIG. 
5, 7 denotes a passenger compartment; 9 denotes a front window glass; 10 
denotes an engine compartment; 11 denotes an engine compartment hood; and 
12 denotes a front door of the glove box. In this embodiment, the air 
conditioning system is adapted to be mounted under the car dashboard 8 in 
front of the front passenger seat, that is, under the right side portion 
of the car dashboard 8 (in this embodiment, the air conditioning system is 
used in an automobile with the steering wheel on left side). 
The fan unit 1 comprises a fan 3 which is disposed within a enclosure of 
the fan unit 1 so that its rotational axis is substantially vertical. The 
fan 3 comprises a centrifugal fan 3a, drive motor 3b for the centrifugal 
fan 3a, and a scroll casing for supporting the fan motor 3b and for 
enclosing the centrifugal fan 3a. The scroll casing 3b is formed to draw 
air from a top opening (not shown) in the top wall of the scroll casing 
3c, and to direct an air flow generated by the centrifugal fan 3a to the 
air conditioning unit 5 through a connecting duct 100 and a deodorization 
filter unit 6, as described hereinafter. 
Provided above the fan 3 is a switching box 2 for switching a suction port 
between an interior port, from which air in the passenger compartment is 
drawn into the fan 3, and an exterior port, from which air outside of the 
automobile is drawn into the fan 3. In particular, as shown in FIG. 2, the 
switching box 2 comprises a housing 2b substantially in the form of a half 
cylinder. The housing 2b includes a first opening 2a as the interior 
suction port and a second opening as the exterior port. The first opening 
2a is fluidly connected to the passenger compartment, and the second 
opening 2c is fluidly connected to the outside of the automobile. A door 
(not shown) is provided for rotation about a pivot 2e between a first 
position where the door closes the first opening 2a and a second position 
where the door closes the second opening 2c. 
Within the housing 2b of the switching box 2, a dust filter assembly 4 is 
provided for removing dust contained in the air introduced into the air 
conditioning system. The dust filter assembly 4 comprises three filter 
elements 4a, 4b and 4c which close the top opening of the fan 3. The 
filter elements 4a, 4b and 4c are supported by a support 2f which is 
formed into a trapezoidal shape as shown in FIG. 2 to increase the 
filtration surface of the dust filter assembly 4, and to increase the life 
time of the dust filter elements 4a, 4b and 4c. The dust filter elements 
4a, 4b and 4c can be made of, for example, an electret nonwoven fabric. 
The air conditioning unit 5 is disposed on the left side of the fan unit 1 
with the deodorization filter unit 6 therebetween. The air conditioning 
unit 5 comprises a casing 5b and a heat exchanging unit which is disposed 
within the casing 5b. The heat exchanging unit comprises an evaporator 5a 
and a heater core (not shown) which is disposed downstream of the 
evaporator 5a. 
The evaporator 5a is connected to a refrigerant circuit (not shown) to 
receive a refrigerant medium, as is well known in the art. The refrigerant 
medium is expanded through an expansion valve (not shown) provided at the 
inlet of the evaporator 5a. The expanded refrigerant gas reduces the 
temperature of the evaporator 5a. Thus, the temperature of the air which 
passes through the evaporator 5a decreases. 
The heater core is a conventional type that is connected to a cooling 
system of the automobile engine (not shown) to receive the heated cooling 
water, as is well known in the art. The heated water introduced into the 
heater core increases the temperature of the heater core. Thus, the 
temperature of the air which passes through the heater core increases. The 
heater core comprises means for controlling the temperature of the heated 
air, for example, a valve for controlling the flow rate of the heated 
water from the automobile engine, and a discharge mode switching door (not 
shown) for switching the positions where the air is discharged into the 
passenger compartment of the automobile. 
The deodorization filter unit 6 comprises a housing 6c which defines first 
and second air ducts 6a and 6b. The second air duct 6b branches from the 
first air duct 6a and extends over and substantially in parallel to the 
first air duct 6a. Provided between the first and second air ducts 6a and 
6b is a deodorization filter 6d to separate the first and second air ducts 
6a and 6b from each other. The bottom surface of the deodorization filter 
6d faces the first air duct 6a, and the top surface of the deodorization 
filter 6a faces the second air duct 6b. In particular, the deodorization 
filter 6e extends between the inlet of the first air duct 6a and the 
switching door 6e to provide a passage 6h between the first and second air 
ducts downstream of the switching door 6e. As in the prior art, the 
deodorization filter 6d comprises energized charcoal for removing odorous 
substances, such as Nox and CH, which are contained in exhaust gas from 
automobiles and are introduced into the passenger compartment. Addition to 
the odors, such substances are bad for the health of the passengers within 
the passenger compartment. 
A switching door or valve 6e is provided within the first air duct 6a 
substantially under the bottom surface of the deodorization filter 6d, in 
particular, in this embodiment, at the downstream end of the deodorization 
filter 6a. The switching door 6e is rotatable about the shaft 6f between a 
first or normal position, which is shown in FIG. 1, and second or 
deodorization position which is shown in FIG. 3. A air flow from the fan 
unit 1 is directed to the air conditioning unit 5 through the first air 
duct 6a and the switching door 6e as shown by a flow line FL in FIG. 1 
when the switching door is at the first position to provide a normal mode 
of air conditioning. On the other hand, when the switching door 6e is at 
the second position, the switching door 6e obstructs the air flow through 
the first air duct 6a to direct it from the fan unit 1 to the air 
conditioning unit 5 through the deodorization filter 6d, the second air 
duct 6b and the passage 6h as shown by a flow line FL in FIG. 3. Thus, a 
deodorization mode of air conditioning is provided. 
The shaft 6f is horizontally supported within the first air duct 6a for 
rotation. The shaft 6f is connected to a drive shaft of a servo-motor 6g 
(FIG. 5) which is provided outside of the housing 6c. The servo-motor 6g 
is electrically connected to a control unit as described hereinafter. As 
described in detail hereinafter, provided within the first air duct 
upstream of the switching door 6e is a smell sensor which is electrically 
connected to the controller 15 to control the servo-motor 6g based on 
concentration of the odorous substances in the air flow within the first 
air duct 6a. 
With reference to FIG. 6, the deodorization filter 6d is formed into a flat 
plate with a sealing portion 6i which extends along the periphery on the 
bottom surface of thereof. The deodorization filter 6d is supported by a 
frame 6j, which is integrally formed with the housing 6c, to extend in 
substantially a horizontal plane between the first and second air ducts 6a 
and 6b. The frame 6j defines top and bottom openings through which air 
flows when the deodorization mode is selected. The frame 6j further 
includes a front opening 6k through which the used deodorization filter 6d 
is removed, and a fresh one is inserted into the frame 6j, thus the 
filters are exchanged. 
The deodorization filter unit 6 further comprises a cover 6m, a 
substantially rectangular plate, for enclosing the front opening of the 
frame 6j. The cover 6m includes a pair of protrusions 6r at the top edge 
of the rectangular plate and a pair of mounting tabs 6p at the bottom edge 
of the rectangular plate as shown in FIG. 6. A pair of slots 6q for 
receiving the mounting tabs 6p and a pair of resilient hooks 6s for 
engagement with the protrusions 6r are provided on the housing 6c of the 
deodorization filter unit 6 to mount and to secure the cover 6m on the 
housing 6c at the front opening. In order to change the used deodorization 
filter 6d, the front door 12 of the glove box is opened to remove the 
cover 6m from the housing 6c. Thus, the deodorization filter 6c can be 
exchanged in the direction shown by arrow Z in FIG. 4. 
FIG. 6 illustrates the controller 15 for controlling the servo-motor 6g for 
rotating the switching door 6e. The controller 15 can be formed by a micro 
computer which includes a read only memory (ROM) 15a, a random access 
memory (RAM) 15b, central processing unit (CPU) 15c, an output port 15d, 
an input port 15e, which are connected by a bi-directional bus 15f. The 
servo-motor 6g is connected to the output port 15d through a motor driver 
15h. A smell sensor 14 is connected to the input port 15e through an A/D 
converter 15i. Further, connected to the input port 15 through A/D 
converters 15j and 15k are a main switch 13a for the air conditioning 
system and a deodorization selecting switch 13b. The smell sensor 14, the 
main switch 13a, and the deodorization mode selecting switch 13b are 
connected to an electrical power source 16 to apply a voltage as signals 
to the controller 15 from the respective input elements. 
The smell sensor 14 is a type of an oxidation semiconductor gas sensor 
which sends an electric voltage signal corresponding to concentration of 
the odorous substances, such as Nox and CH, which are contained in the 
exhaust gas from an automobile and are introduced into the passenger 
compartment, in the air flow within the first air duct 6a upstream of the 
switching door 6e. 
With reference to FIG. 8, the control of the servo-motor 6g will be 
described. FIG. 8 illustrates a routine for controlling the servo-motor 
6g. 
Once the main switch 13a is on, the routine for controlling the servo-motor 
6g starts and goes to step S10, in which it is determined whether the 
deodorization mode selecting switch 13b is on or not. If the deodorization 
mode selecting switch 13b is not on, the routine is ended in step S12. If 
the deodorization mode selecting switch 13b is on, the routine goes to 
step S14, in which the signal Sv from the smell sensor 14 is input into 
S1. 
In step S14, it is determined whether S1 is equal to or smaller than a 
predetermined value S0. If S1 is equal to or smaller than S0, it is 
determined that substantially no odorous substances exist in the air flow 
within the first air duct 6a, and the routine goes to step S18. In step 
S18, the normal mode of air conditioning is selected, and the servo-motor 
is energized to rotate the switching door 6e to the first position. Thus, 
air flow from the fan unit 1 is directed to the air conditioning unit 5 
through the first air duct 6a and the switching door 6e. 
In the normal mode of air conditioning, air from the fan unit 1 flows along 
the first air duct 6a which is defined by bottom wall, side walls of the 
housing 6c of the deodorization filter unit 6 and the bottom surface of 
the deodorization filter 6d. That is, the deodorization filter 6d does not 
extend into the first air duct 6a. Thus, the deodorization filter 6d does 
not obstruct the air flow to minimize the flow resistance of the air 
conditioning system. This increases the flow rate during the normal mode, 
and decreases the noise of the fan unit 1 and the power consumption of the 
drive motor 3b. Addition to this, the deodorization filter 6d, which 
defines the first air duct 6a, can provide a sound absorption effect which 
reduces the propagation of noise of air flow. 
If S1 is greater than S0, it is determined that odorous substances exists 
in the air flow within the first air duct 6a, and the routine goes to step 
S20. In step S20, the deodorization mode of air conditioning is selected 
and the servo-motor is energized to rotate the switching door 6e to the 
second position. Thus, air flow from the fan unit 1 is directed to the air 
conditioning unit 5 through the deodorization filter 6d, the second air 
duct 6b and the passage 6h. When the air flow passes through the 
deodorization filter 6d, the odorous substances are remove from the air 
flow by the energized carbon in the deodorization filter 6d. 
The above mentioned routine for controlling the servo-motor 6g is executed 
at a time interval preferably within the range of 0.5-1 sec. 
With reference to FIGS. 9 and 10, the second embodiment of the invention 
will be described. 
The second embodiment is substantially the identical to the first 
embodiment, except that in the second embodiment, a timer means is 
provided instead of the smell sensor 14. Thus, the second embodiment does 
not comprise any sensors for detecting the concentration of the odorous 
substances as shown in FIG. 9. In FIGS. 9 and 10, the elements identical 
to those of the first embodiment are indicated by the same reference 
numbers. 
With reference to FIG. 10, the control of the servo-motor 6g according to 
the second embodiment will be described. FIG. 10 illustrates a routine for 
controlling the servo-motor 6g. 
Once the main switch 13a is on, the routine for controlling the servo-motor 
6g starts and goes to step S30 in which zero is input into T. Then, the 
routine goes to step S32, in which it is determined whether the 
deodorization mode selecting switch 13b is on or not. If the deodorization 
mode selecting switch 13b is not on, the routine is ended in step S34. If 
the deodorization mode selecting switch 13b is on, the routine goes to 
step S36, in which the deodorization mode of air conditioning is selected, 
that is, and the servo-motor is energized to rotate the switching door 6e 
to the second position. Thus, air flow from the fan unit 1 is directed to 
the air conditioning unit 5 through the deodorization filter 6d and the 
second air duct 6b. When the air flow passes through the deodorization 
filter 6d, the malodorous substances are removed from the air flow by the 
energized carbon in the deodorization filter 6d. 
Then, the routine goes to step S38 and T+1 is input into T. In step S40, it 
is determined that T is equal to or greater than a predetermined value T0. 
If T is smaller than T0, the routine goes back to step S32. Thus, the 
routine repeats steps S32-S40 until T satisfies the condition of 
T0.ltoreq.T in step S40. While the routine repeats steps S32-S40, the mode 
of air conditioning is kept in the deodorization mode, that is, the 
servo-motor 6g is energized to rotate the switching door 6e at the second 
position. The predetermined value T0 is selected so that a sufficient time 
period to remove the odorous substances is obtained. 
When T satisfies the condition of T0.ltoreq.T in step S40, the routine goes 
to step S42, in which the normal mode of air conditioning is selected, and 
the servo-motor is energized to rotate the switching door 6e to the first 
position. Thus, air flow from the fan unit 1 is directed to the air 
conditioning unit 5 through the first air duct 6a and the switching door 
6e. 
The above mentioned routine for controlling the servo-motor 6g is executed 
at a time interval preferably within the range of 0.5-1 sec. 
With reference to FIG. 11, the third embodiment of the invention will be 
described. 
The third embodiment of the invention is substantially identical to the 
first and second embodiments, except for the dimension of the 
deodorization filter within the housing of, the deodorization filter unit 
and the position of the switching door within the first air duct. Thus, in 
FIG. 11, the elements identical to those in the first and second 
embodiments are indicated by the same reference numbers. 
In this embodiment, the deodorization filter 6d extends to separate the 
second air duct 6b completely from the first air duct 6a while, in the 
first and second embodiments, the same extends between the inlet of the 
first air duct 6a and the switching door 6e to provide the passage 6h 
between the first and second air ducts downstream of the switching door 
6e. Thus, in this embodiment, the passage 6h of the first and second 
embodiments is not provided. Further, the switching door 6e is provided 
within the first air duct 6a under the deodorization filter 6d 
substantially at the center of the filter along the flow direction in the 
first air duct 6a while the switching door is positioned at the downstream 
edge of the deodorization filter in the first and second embodiments. 
The switching door 6e is rotatable between the first and second positions 
about the shaft 6f. When the switching door 6e is at the first rotational 
position as shown by the solid line in FIG. 11, the air flow from the fan 
unit 1 is directed to the air conditioning unit 5 through the first air 
duct 6a and the switching door 6e which is shown by flow line FL, as in 
the preceeding embodiments. On the other hand, when the switching door 6e 
is at the second position as shown by the dashed line in FIG. 11, air flow 
is obstructed by the switching door 6e at the second position and directed 
to the second air duct 6b. The air flow which enters the second air duct 
6b is directed to the air conditioning unit 5 through the deodorization 
filter 6d again, as shown by the dashed curve FL'. Thus, according to the 
third embodiment, the air is filtered twice by the deodorization filter 6d 
when the deodorization mode is selected. This allows the deodorization 
filter 6d to be reduced in thickness. 
Thus, according to the third embodiment, the overall dimensions of the 
deodorization filter unit 6 can be reduced. 
With reference to FIGS. 12-19, the fourth embodiment of the invention will 
be described. 
In this embodiment, the fan is positioned so that its rotational axis is 
oriented to a horizontal direction as shown in FIGS. 12, 13 and 16 instead 
of, as in the preceeding embodiments, being positioned so that its 
rotational axis is oriented to the vertical direction. Further, in this 
embodiment, the configuration of the first air duct is different from that 
of the preceeding embodiments. In FIGS. 12, 13, 14, 15 and 16, the 
elements which correspond to those in the preceeding embodiments are 
indicated by the same reference numbers with primes. FIGS. 17 and 18 
illustrate an example of the housing 6c of the deodorization filter unit 
6, in which the first air duct does not include a duct configuration of 
according to the invention. In FIGS. 17 and 18, the elements which 
correspond to those in the embodiments of the invention are indicated by 
the same reference numbers with double primes. 
In case that the dimension Ws of the exit of the connecting air duct 100, 
lateral to the flow direction within the first air duct 6a, is remarkably 
smaller than that Wf of the deodorization filter 6d, as shown in FIG. 17, 
air flow introduced into the first air duct 6a expands and the flow 
velocity decreases from V.sub.1 to V.sub.2 (V.sub.1 &gt;V.sub.2) suddenly, 
which results in pressure loss .DELTA. P of the air flow. The pressure 
loss .DELTA. P of the air flow is defined as follows. 
##EQU1## 
Where, .zeta. : flow resistance coefficient 
.xi. : coefficient 
.rho. : density of air (Kg/m3) 
In the above equations, .xi. is a coefficient shown in FIG. 19. .xi. is 1.0 
when the angle .theta. is greater that 60 degrees. 
It will be understand that smaller the angled smaller the pressure loss 
.DELTA. P is obtained. However, this is not practical way for solving the 
above problem since, if the angle .theta. is simply reduced as shown in 
FIG. 18, the area for mounting the deodorization filter 6d is reduced so 
that the performance of the filter is deteriorated. 
In order to prevent the pressure loss of the air flow, the first air flow 
to diverge gradually in the flow direction, as shown in FIG. 8. However, 
as described above, the deodorization filter 6d defines the top inner 
surface of the first air duct 6a. Therefore, if the first air duct is 
formed into the shape in FIG. 18, the deodorization filter 6d must be 
reduced in volume. 
Thus, in this embodiment of the invention, the filter unit 6 includes a 
first air duct 6a' improved to reduce the pressure loss while the area for 
the deodorization filter is maintained. 
In particular, with reference to FIG. 15, the first air duct 6a' includes a 
bottom wall 60a which is substantially formed into a trapezoid E-F-G-H-E 
which has a top side F-G, a bottom side E-H which are parallel to each 
other, and two oblique sides F-E and G-H which are symmetrically apart to 
each other along the flow direction shown by an arrow in FIG. 15 so that 
an angle .theta. is provided therebetween. The deodorization filter 6d' is 
provided to cover the rectangular top opening A-B-C-D-A. 
On the other hand, the switching door is provided so that the door closes a 
rectangular opening A-D-H-E-A when the deodorization mode is selected. In 
particular, in this embodiment, the rotational shaft 6f' is provided along 
one edge of the switching door 6e as shown in FIG. 12. The switching door 
6e' is provided so that the rotational shaft 6f' extends substantially 
along the top side A-D of the rectangular opening A-D-H-E-A. 
Between the bottom wall 60a and the top opening, a pair of side walls are 
provided. The side walls include three triangular walls 60b, 60d and 60f; 
60c, 60e and 60g respectively. The first triangular wall 60b and 60c are 
connected to the bottom wall 60a perpendicular to each other along the 
oblique sides F-E and G-h of the bottom wall 60a. The third triangular 
walls 60f and 60g are parallel to each other to define the rectangular to 
opening A-B-C-D-A where the deodorization filter is positioned. 
The second triangular walls 60d and 60e are connected to the first and 
third triangular walls 60b and 60f; 60c and 60g. A pair of front 
triangular walls 60h and 60i are connected to the second triangular walls 
60d and 60e perpendicular to the bottom wall 60a along the oblique sides 
B-J and C-L of the second triangular walls 6d and 60e. In particular, the 
front triangular walls 60h and 60i are connected to the second triangular 
walls 60e and 60e so that the sides J-F and L-G of the first triangular 
walls 60b and 60c are aligned to the sides I-J and K-L of the front 
triangular walls 60h and 60i, and a rectangular opening I-K-G-F-I is 
formed between the front triangular walls and the first triangular walls. 
The rectangular opening I-K-G-F-I provides the inlet port of the first air 
duct 6a', that is, the connection air duct (not shown in FIG. 15), which 
is provided between the fan unit and the deodorization filter unit, is 
connected to the rectangular opening I-K-G-F-I. In particular, in this 
embodiment, the fan unit 3' is connected to the first air duct 6a' so that 
the end of the outer wall, which extens spirally, of the scroll casing 3a 
is connected to the top side F-G of the trapezoidal bottom wall 60a. 
Air flow is introduced into the first air duct 6a' through the inlet 
opening I-K-G-F-I, directed to the deodorization filter through the top 
opening A-B-C-D-A when the deodorization mode is selected, and directed to 
the air conditioning unit through the opening A-D-H-E-A when the normal 
mode is selected. 
According to this embodiment, while the area for the deodorization filter 
6d' is not reduced because of the rectangular to opening A-B-C-D-A, the 
pressure loss .DELTA. P can be reduced by making the angle.theta. smaller 
than 60 degrees, at which the flow resistance coefficient .zeta. is equal 
to or smaller than 0.9 as shown in FIG. 19. 
According to the invention, the deodorization filter 6d and 6d' is 
positioned at a horizontal position relative to the evaporator 5a, as 
shown in FIGS. 1, 3 and 10, that is, the deodorization filter 6d is not 
positioned at substantially a vertical position lower that that of the 
evaporator 5a. This prevents the deodorization filter 6d from receiving 
condensation from the evaporator 5a. Therefore, no odor, due to water 
applied to the deodorization filter, will be generated. 
In the preceeding embodiment, the switching door 6e and 6e' is actuated by 
the servo-motor 6g. However, the switching door can be moved between the 
first and second operational positions, by hand, by a driver or a 
passenger. In this case, a lever or a handle for operating the switching 
door can be provided on the front face (not shown) of the car dashboard 8. 
The lever may be connected to the shaft 6f and 6f' through a link or a 
cable. 
In the preceeding embodiment, the air conditioning system includes both a 
deodorization filter and a dust filter. However, the invention can be 
applied to an air conditioning system which includes only a dust filter 
which is provided between the first and second air duct, where the 
deodorization filter is positioned in the embodiment. 
It may be further understood by those skilled in the art that the forgoing 
description is a preferred embodiment of the disclosed device and that 
various changes and modifications may be made without departing from the 
spirit and scope of the invention.