Automobile air conditioner

An automobile air conditioner of a reheat air mix type, having an evaporator disposed in a duct and a heater core disposed in the duct at the downstream side of the evaporator. Chilled air passages are formed between both sides of the heater core and the surfaces of opposing walls of the duct. The chilled air passages are extended to form a first duct leading to an upper air outlet to the room of automobile and a second duct leading to a lower air outlet opening to the room. A part of the warmed air coming from the heater core is delivered to the first duct while the other part is delivered to the second duct. The air conditioner further has a first air mix damper for controlling the ratio between the flow rate of chilled air flowing into the heater core and the flow rate of the chilled air flowing into the first duct, and a second air mix damper for controlling the ratio between the flow rate of chilled air introduced into the second duct and the flow rate of warmed air flowing from the heater core into the second duct.

BACKGROUND OF THE INVENTION 
The present invention relates to an air conditioner for automobiles and, 
more particularly, to an automobile air conditioner having an air 
conditioning system of the reheat air mix type and provided with two air 
outlets for blowing the heated or cooled air to the upper section and 
lower section of the compartment, i.e. to the upper part and lower part of 
the driver, respectively. 
The conventional air temperature controller of the air conditioner of this 
kind could not provide a temperature difference between the air blown out 
from the upper air outlet and the air blown out from the lower air outlet. 
To obviate this problem, Japanese Utility Model Publication No. 9704/1977, 
for example, discloses a system in which the conditioned air is discharged 
from an upper air outlet (chilled air outlet) and a lower air outlet (warm 
air outlet) at a suitable ratio of flow rate, wherein a part of the 
chilled air which has passed an evaporator of refrigeration cycle is 
directly introduced into the duct leading to the upper air outlet to mix 
the chilled air to the conditioned air flowing through the duct to thereby 
obtain a temperature difference between the flows of air from both air 
outlets. 
Also, Japanese Utility Model Publication No. 9781/1973 discloses a system 
in which a chilled air passage is provided at the upstream side of a 
heater core. The chilled air passage is adapted to introduce a part of the 
chilled air supplied by a blower to the upper air outlet. A part of the 
heated air is introduced into the chilled air passage so as to be mixed 
with the chilled air flowing through the latter to thereby establish the 
temperature difference of the air discharged from the upper and lower air 
outlets. 
These known arrangements, however, suffer the following disadvantages. 
Namely, in the air conditioning system of the first mentioned type, it is 
necessary to employ three dampers for controlling the temperatures of the 
air from the upper and lower air outlets, i.e. a mix damper, air outlet 
section damper and a chilled air damper. Consequently, the size of the 
unit is increased impractically and the construction of the system as a 
whole is complicated. 
The second type of air conditioning system mentioned above is also 
inconvenient in that it requires four dampers, namely a temperature 
controlling valve for adjusting the temperature of warm air after flowing 
through a heat exchanger, two chilled air temperature control valves for 
controlling the temperature of air discharged from the chilled air outlet 
and an air shut-off valve. In addition, this arrangement cannot provide 
such an operation mode that the whole of the chilled air is discharged 
from the chilled air outlet. This point is a fatal disadvantage for the 
air conditioner having cooling function. 
SUMMARY OF THE INVENTION 
Accordingly, an object of the invention is to provide a small-sized 
automobile air conditioner in which the temperature difference between the 
controlled air discharged from the upper air outlet and the controlled air 
discharged from the lower air outlet can be controlled as desired by only 
a pair of dampers. 
To this end, according to one aspect of the invention, an automobile air 
conditioner is provided which includes a heater core, a main chilled air 
passage, and a sub-chilled air passage disposed around the heater core so 
as to by-pass the heater core. A main warm air passage are and a sub-warm 
air passage connected to the outlet side of the heater core, with the main 
chilled air passage and the sub-warmed air passage joining each other and 
leading to an upper air outlet, while the sub-chilled air passage and the 
main warm air passage join each other and lead to a lower air outlet. A 
first air mix door is adapted to control the ratio between the flow rate 
of chilled air flowing into the main chilled air passage and the flow rate 
of the chilled air flowing into the heater core, and a second air mix door 
is adapted to control the ratio of mixing of the chilled air coming from 
the sub-chilled air passage and the warm air coming from the main warm air 
passage. 
Another object of the invention is to provide an automobile air conditioner 
capable of maintaining a predetermined temperature difference between the 
conditioned air discharged from the upper air outlet and the conditioned 
air discharged from the lower air outlet. 
To this end, according to another aspect of the invention, an automobile 
air conditioner is provided which includes a controlling mechanism adapted 
to control the second air mix door in accordance with the state of control 
of the first air mix door. 
Yet still another object of the invention is to provide an automobile air 
conditioner of the kind described, in which two air mix doors for 
controlling the controlled air flowing in an upper outlet duct and the 
controlled air flowing in a lower outlet duct are disposed in a compact 
manner within a unit case. 
To this end, according to a further aspect of the invention, an automobile 
air conditioner is provided which includes a heater core having an air 
inlet surface and an air outlet surface respectively spaced from the inner 
surfaces of a duct by a first gap and a second gap, with the first gap 
constituting a first chilled air passage while the second gap constitutes 
a second chilled air passage. First and a second warm air passages are 
disposed at the outlet side of the heater core such that the flow of air 
coming out of the heater core is branched into the first and second warm 
air passages. The first chilled air passage and the second warm air 
passage join each other and lead to an upper air outlet while the second 
chilled air passage and the first warmed air passage join each other and 
lead to a lower air outlet. A first air mix door is disposed in the first 
gap and adapted to control the ratio between the flow rate of chilled air 
flowing into the first chilled air passage and the flow rate of chilled 
air flowing into the heater core, with a second air mix door being 
disposed in the second gap and being adapted to control the ratio of 
mixing between the chilled air coming from the second chilled air passage 
and the warm air coming from the first warm air passage. 
Other objects, features and advantages of the invention will become clear 
from the following description of the preferred embodiments taken in 
conjunction with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the drawings wherein like reference numerals are used 
throughout the various views to designate like parts and, more 
particularly, to FIG. 1, according to this figure, an evaporator 2 is 
adapted to chill the ambient air, room air or the mixture of ambient air 
and room air which is supplied thereby by a blower not shown. A heater 
core 3 is adapted to heat the air chilled and dehumidified by the 
evaporator 2. The evaporator 2 and the heater core 3 are disposed in a 
duct A in the mentioned order. The heater core 3 is supported by walls 31 
and 32 provided in the duct A. A main chilled air passage 9a is formed 
between the wall 31 and the inner surface of the duct, while a sub-chilled 
air passage 9b is formed between the wall 32 and the inner surface of the 
duct. The chilled air passages 9a and 9b are so sized and arranged that, 
when the chilled air which has passed through the evaporator 2 bypasses 
the heater core 3, the chilled air is distributed to the main and 
sub-chilled air passages 9a and 9b at a ratio of 8:2. 
A first air mix door 5a is adapted to control the ratio between the flow 
rate of chilled air flowing into the heater core 3 and the flow rate of 
the chilled air flowing into the main chilled air passage 9a. 
The first air mix door 5a is fixed to a shaft 51 rotatably secured to the 
end of the chilled air inlet surface of the heater core 3 adjacent to the 
main chilled air passage 9a, and is swingable between a first position 
(shown by full line) fully closing the main chilled air passage 9a and a 
second position (shown by broken line) fully closing the inlet surface of 
the heater core 3. 
A control door 5b is adapted to control the ratio of distribution of the 
warm air coming out from the heater core 3 to the main and sub-warm air 
passages 8a and 8b. The control door 5b is mounted on a shaft 52 rotatably 
carried by the duct A. 
The control door 5b is rotatably between the position shown by full line 
and the position shown by broken line to control the areas of the main and 
sub-warm air passages 8a and 8b within the region of rotation thereof. 
A second air mix door 5c is adapted to control the ratio of mixing between 
the warm air coming from the main warm air passage 8a and the chilled air 
coming from the sub-chilled air passage 9b. The second air mix door 5c is 
mounted on a shaft 53 rotatably secured to the end of the warm air outlet 
surface of the heater core adjacent to the sub-chilled air passage 9b. The 
second air mix door 5c is swingable between the position shown by full 
line and the position shown by broken line to control the ratio of mixing 
of the warm air coming from the main warm air passage 8a and the chilled 
air coming from the sub-chilled air passage 9b. 
A chilled air duct 7a is adapted to mix the chilled air from the main 
chilled air passage 9a and the warm air from the sub-warm air passage 8b 
and to introduce the mixture to an upper air outlet 20. A warm air duct 7b 
is adapted to mix the warm air from the main warm air passage 8a and the 
chilled air coming from the sub-chilled air passage 9b and to introduce 
the mixture to a lower air outlet 21. 
The operation of the air conditioner of the invention having the described 
construction is as follows. 
When the first and second air mix doors 5a and 5c and the control door 5b 
take the positions shown by full lines, the air conditioner is in the 
condition for the strongest warming of the passenger compartment 
automobile. Namely, a door (not shown) for introducing external and 
internal air takes the position for introducing the external air, and the 
blower is rotating at the highest speed. The refrigeration cycle does not 
operate in this state. 
The external air which has passed through the evaporator 2 now having no 
chilling effect is introduced into the heater core 3 so as to be heated 
thereby. The heated air is then discharged through both of the main and 
sub-warm air passages 8a and 8b and is distributed to the lower air outlet 
21 and the upper air outlet 20 through the warm air duct 7b and the 
chilled air duct 7a, respectively. 
Assume that the first air mix door 5a is gradually shifted toward the 
position shown in broken line while fixing the control door 5b and the 
second air mix door at the positions shown by full line. As a result, the 
flow rate of chilled air coming into the chilled air duct 7a through the 
main chilled air passage 9a is increased gradually, so that the 
temperature of the conditioned air discharged from the upper outlet 
gradually becomes lower than the temperature of the warm air discharged 
from the lower air outlet. It is, therefore, possible to warm up the whole 
part of the passenger compartment while supplying properly chilled air 
from the upper air outlet. 
In the above described embodiment, it is possible to lower the temperature 
of the chilled air from the upper air outlet while maintaining the flow 
rate of air of chilled air in the main chilled air passage 9a constant, by 
moving the control door 5b towards the position shown by broken lines. 
The temperature difference between the air discharged from the upper air 
outlet 20 and the air discharged from the lower air outlet 21 is maximized 
when the control door 5b fully closes the sub-warm air passage 8b. 
When the driver wishes to slightly lower the air temperature in the leg 
area of the vehicle, it is only necessary to simply move the second air 
mix door 5c towards the position of broken line, so that the flow rate of 
warm air coming from the main warm air passage 8a is gradually decreased 
while the flow rate of the chilled air from the sub-chilled air passage 9b 
is gradually increased to lower the temperature of the conditioned air 
discharged from the lower air outlet 21. 
When the driver wishes to lower the temperature in the whole passenger 
compartment, it is only necessary to move the first air mix door 5a 
further towards the position of broken line and lower the speed of the 
blower correspondingly. 
By so doing, the flow rate of the chilled air flowing into the heater core 
3 is decreased to lower the flow rate of warm air delivered to the main 
and sub-warm air passages from the heater core, while the flow rate of 
chilled air discharged from the upper air outlet past the main chilled air 
passage 9a is increased. Consequently, the heating effect is suppressed to 
lower the temperature of whole space in the room. 
In the dehumidifying warming mode of the air conditioner, the room air and 
the ambient air are sucked substantially at an equal rate. Even in this 
state, the temperature of the conditioned air from the upper air outlet 20 
and the lower air outlet 21 are controlled by controlling the opening 
degrees of the first and the second air mix doors 5a and 5c. 
It is also possible to control simultaneously the temperatures of 
conditioned air from the upper and lower air outlets 20 and 21, by 
controlling the opening degree of the control door 5b while fixing the 
first and the second air mix doors 5a and 5c at intermediate positions. 
In the cooling mode of operation of the air conditioner, the circulation of 
hot water through the heater core 3 is stopped, and the first air mix door 
5a is moved to the position shown by the broken line. Therefore, the whole 
part of the chilled air chilled by the evaporator 2 is discharged from the 
upper air outlet 20 via the main chilled air passage 9a. 
However, as the second air mix door 5c is moved to the position shown by 
broken lines, a part of the chilled air is discharged also from the lower 
air outlet 21 via the sub-chilled air passage 9b. 
The first and the second air mix doors 5a and 5c may be controlled 
independently of each other or the opening degree of the second air mix 
door 5c may be controlled in accordance with the opening degree of the 
first air mix door 5a. It is also possible to control both air mix doors 
5a,5c electrically in accordance with the temperature difference between 
the air discharged from the upper air outlet and the air discharged from 
the lower air outlet, so as to maintain a constant temperature difference. 
These ways of control of the first and second air mix doors 5a, 5c will be 
explained more fully hereinbelow. It is further possible to control the 
control door 5b independently or in relation to the opening degree of at 
least one of the first and second air mix doors 5a and 5c. 
As shown most clearly in FIG. 2, the air conditioner, includes a fan motor 
1 having a fan 101, a door 4 for switching the suction of air between 
ambient air and passenger compartment air and a passenger compartment air 
introduction port 41 and an ambient air introduction port 42 leading to 
the duct A. 
The heater 3 is disposed in the duct A such that the inlet and outlet 
surfaces thereof are opposed to the inner surfaces of the duct A. The 
inlet surface and the opposing inner surface of the duct constitutes a gap 
serving as the main chilled air passage 9a while another gap formed 
between the outlet surface and the opposing inner surface constitutes a 
sub-chilled air passage 9b. 
The first air mix door 5a has a shaft 51 fixed to the corner of the heater 
core 3 adjacent to the outlet side of the main chilled air passage 9a so 
that it is able to rotate between the inlet surface of the heater core 3 
and the inner surface of the wall of the duct A. 
The second air mix door 5c has a shaft 53 fixed to the corner of the heater 
core 3 adjacent to the inlet side of the sub-chilled air passage 9b and is 
rotatable between the outlet surface of the heater core 3 and the inner 
wall of the duct. By arranging the two air mix doors 5a, 5c in the 
described manner, it is possible to control the flow rate of air in 
respective chilled air passages 9a, 9b without necessitating an increase 
in the rotation angles of the air mix doors 5a, 5c, so that the air 
conditioner as a whole can be made compact. 
A partition wall 50, provided at the outlet surface of the heater core 3, 
is adapted to divide the channel of the air from the heater core 3 into a 
main warm air passage 8a and a sub-air passage 8b. 
The control door 5b has a shaft 52 supported by the duct at the outlet of 
the sub-warm air passage 8b so as to be able to rotate between the end of 
the partition wall 50 and the corner of the heater core 3 facing the warm 
air passage 8b. 
A shunting port D leading to a defroster 22 opens into the warm air duct 
7b. A switching door provided at the shunting port D is adapted to switch 
the flow of warm air between first mode in which the warm air flows to the 
defroster 22 and a second mode in which the warm air flows towards the 
lower air outlet 21. 
An actuator 31 is adapted to actuate the first air mix door 5a, with the 
actuator 31 including a diaphragm (not shown) operated by vacuum, an 
actuating rod 311 connected at one end to the diaphragm and a vacuum 
control valve 312 for controlling the vacuum applied to the diaphragm. 
Another actuator 32 for actuating the second air mix door 5c has a 
diaphragm chamber (not shown) defined by a diaphragm, an actuating rod 321 
fixed to the diaphragm and a vacuum control valve 322 adapted for 
controlling the vacuum applied to the diaphragm. 
The vacuum control valves 312 and 322 are provided with solenoid valves 
S.sub.1 and S.sub.3 adapted to effect a switching between a state in which 
the atmospheric pressure is applied to the diaphragm chamber and a state 
in which the vacuum is applied to the diaphragm chamber. More 
specifically, vacuum is applied to the diaphragm chamber as the solenoids 
S.sub.1 and S.sub.3 are energized, so that the doors 5a and 5c are pulled 
towards the actuators 31,32 by the rods 311 and 321. 
As the solenoids S.sub.1 and S.sub.3 are de-energized, the vacuum which has 
been applied to the diaphragm chamber is vented to the atmosphere, so that 
the spring which has been compressed by the diaphragm under application of 
vacuum is relieved to force the doors 5a and 5c through rods 311 and 321 
to a normal position. 
When the doors 5a and 5c come to take predetermined positions, the solenoid 
valves S.sub.2 and S.sub.4 are activated to close both to the atmospheric 
passage and the vacuum passage leading to the diaphragm chamber, so that 
the pressure in the diaphragm chamber is maintained at a constant level to 
fix the doors 5a and 5c at these positions. 
An actuator 33 is adapted to actuate the control door 5b, with the actuator 
33 including a diaphragm (not shown), a rod 331 fixed to the diaphragm, 
and a vacuum control valve 332 adapted to control the vacuum to be applied 
to the diaphragm. The vacuum control valve 332 has a solenoid-operated 
change-over valve S.sub.5. When the valve S.sub.5 is not energized by the 
power source, the diaphragm is deflected to the upper position as viewed 
in FIG. 2 by the force of a spring (not shown) so that the door 5b is 
moved to the broken line position through the rod 331. However, as the 
solenoid valve S.sub.5 is energized, the diaphragm is deflected downward 
as viewed in FIG. 2 by the force of the vacuum applied thereto, so that 
the door 5b is reset to the full line position in FIG. 2 through the rod 
331. 
A an actuator 34 actuates the door 4 for switching the suction of air 
between the ambient air and room air. The actuator 34 has a diaphragm (not 
shown), a rod 341 fixed to the diaphragm and a vacuum change-over valve 
342 adapted to control the vacuum applied to the diaphragm. The vacuum 
change-over valve 342 has solenoid valves S.sub.6 and S.sub.7 and two 
diaphragms spaced from each other in the axial direction of the rod 341. 
When both of the solenoid valves S.sub.6 and S.sub.7 are de-energized, both 
diaphragms are deflected to the left as viewed in FIG. 2 by springs, so 
that the door 4 is moved to the broken-line position through the rod 341. 
However, as the solenoid valve S.sub.6 is energized, one of the diaphragms 
has vacuum applied thereto and is deflected to the right, as viewed in 
FIG. 2 while compressing one of the springs, so that the door 4 is pulled 
to the position shown by one-dot-and-dash line in the drawings by the rod 
341. Then, as the solenoid S.sub.7 is energized, both diaphragms are moved 
to the right while compressing another spring, so that the door 4 is moved 
to the full line position. 
The operation of the solenoid valves S.sub.1 to S.sub.7 is controlled by 
the control output from a control circuit C including a microcomputer. 
The command temperature Tso of the passenger compartment air is calculated 
in accordance with the following formula (1) stored in a ROM of the 
microcomputer, from the set temperature Ts which is adjustable by a driver 
through a restart resistance SP, ambient air temperature T.sub.A sensed by 
an ambient air temperature sensor SA, and the heat input Q by the sunshine 
detected by the sunshine sensor SF. 
##EQU1## 
The unit of the command temperature Tso and ambient air temperature T.sub.A 
is [.degree.C.]. A constant .alpha. takes a value of 1/5 when the ambient 
air temperature T.sub.A is higher than 25.degree. C. and 1/15 when the 
same temperature is below 25.degree. C. The heat input Q [Kcal/h] is 
calculated on the assumption that a heat of 20 Kcal/h is inputted to the 
passenger compartment per 1.degree. C. of difference between the 
temperature T.sub.Q detected by the sunshine sensor SF and the temperature 
T.sub.R of room air detected by the compartment air sensor S.sub.R. 
The command warm air temperature Td.sub.Lo of the warm air in the warm air 
duct 7b is calculated in accordance with the following formulae (2) to 
(4), from the command temperature T.sub.SO, ambient air temperature 
T.sub.A, leg space temperature T.sub.L detected by a lower compartment air 
temperature sensor Sc and the temperature TdL detected by a sensor SE in 
the warm air duct 7b. 
##EQU2## 
where, T.sub.soL represents the command temperature of air in the leg 
space. 
EQU .DELTA.T.sub.L =T.sub.SOL -T.sub.L (3) 
##EQU3## 
Note, however, that the Td.sub.Lo is assumed to be Td.sub.Lo =0.degree. C. 
when Td.sub.Lo is equal to or lower than 0.degree. C. and to be Td.sub.Lo 
=60.degree. C. when the same is equal to or higher than 60.degree. C. 
Then, the command opening degree .theta..sub.L of the second air mix door 
5c for obtaining the command warm air temperature Td.sub.Lo is calculated 
by the following formulae (5) and (6): 
EQU .DELTA.Td.sub.Lo =Td.sub.Lo -Td.sub.L (5) 
EQU .theta..sub.L =3.times..DELTA.Td.sub.Lo +15 (6) 
Note, however, that the angle .theta..sub.L is assumed to be .theta..sub.L 
=0.degree. when the calculated .theta..sub.L is equal to or smaller than 
0.degree. and to be .theta..sub.L =30.degree. when the same angle is equal 
to or greater than 30.degree.. It is also assumed that the angle 
.theta..sub.L is 30.degree. when the air conditioner operates in the 
defrosting mode. The opening degree of the door 5c is defined as 0.degree. 
when the door takes the position shown by full line. 
The present opening position of the door 5c is detected by a potentiometer 
PM2 and is compared with the command opening degree .theta..sub.L. The 
door 5c is moved from the present position in either direction depending 
on the result of the comparison, and whether the solenoid valve S.sub.3 is 
to be energized or not is determined depending on the direction of 
movement of the door 5c. 
For instance, assuming that the judgement is made to reduce the opening 
degree of the door 5c from the present opening shown by broken line, at 
first the solenoid valve S.sub.3 is de-energized and then the solenoid 
valve S.sub.4 is de-energized. Consequently, the vacuum which has been 
applied to the diaphragm is vented to the atmosphere so that the door 5c 
is moved towards the heater core. The change of opening degree of the door 
5c is detected momentarily by the potentiometer PM2 and is stored in a 
writable and erasable memory RAM in the microcomputer. A comparison is 
made periodically between the instant opening degree and the command 
opening degree and, when both opening degrees coincide with each other, 
the solenoid valve S.sub.4 is energized to fix the door 5c at this 
position. 
To the contrary, when the judgment is made to demand a greater degree of 
opening from the present opening degree, at first the solenoid valve 
S.sub.3 is energized and then the solenoid valve S.sub.4 is de-energized. 
Consequently, the vacuum is applied to the diaphragm so that the door 5c 
is pulled towards the actuator. As the opening degree of the door 5c 
reaches the command opening degree, the solenoid valve S.sub.4 is 
energized while the solenoid valve S.sub.3 is de-energized to fix the door 
5c at the instant position. 
Meanwhile, the command chilled air temperature Td.sub.UO in the chilled air 
duct 7a is calculated in accordance with the following formulae (7) to 
(9), from the command temperature T.sub.so, ambient air temperature 
T.sub.A upper body air temperature T.sub.U detected by an upper room air 
temperature sensor S.sub.B and the chilled air temperature T.sub.du in the 
chilled air duct 7a detected by a sensor SD in that duct 7a: 
##EQU4## 
where, T.sub.SOU represents the upper body air temperature command value. 
EQU .DELTA.T.sub.U =T.sub.SOU -T.sub.U (8) 
##EQU5## 
Note, however, that the command value Td.sub.Uo of chilled air is assumed 
to be Td.sub.Uo =0.degree. C. when this temperature is equal to or lower 
than 0.degree. C. and to be Td.sub.Uo =30.degree. C. when this temperature 
is equal to or greater than 30.degree. C. Then, the command opening degree 
.theta..sub.U of the first air mix door 5a for attaining the command 
temperature Td.sub.Uo of chilled air is determined in accordance with the 
following formulae (10) and (11). 
EQU .DELTA.Td.sub.Uo =Td.sub.Uo -Td.sub.U (10) 
EQU .theta..sub.U =3.times..DELTA.Td.sub.Uo +15 (11) 
Note, however, that the opening degree .theta..sub.U is assumed to be 
.theta..sub.U =0.degree. when this angle .theta..sub.U is equal to or 
smaller than 0.degree. and to be .theta..sub.U =30.degree. when this angle 
.theta..sub.U equals to or greater than 30.degree.. It is also assumed 
that, in the defrosting mode, the angle .theta..sub.U equals to 
30.degree.. 
The opening degree of the door 5a is defined as being 0.degree. when the 
door 5a takes the position shown by full line. The instant opening 
position of the door 5a is detected by the potentiometer PM1 and is 
compared with the command opening degree .theta..sub.U. The direction of 
movement of the door 5a is determined in accordance with the result of the 
comparison. Whether the solenoid valve S.sub.1 is to be energized or not 
is determined according to the thus determined direction of movement of 
the door 5a. 
For instance, in the case where the demand is for reducing the opening 
degree from the instant position shown by broken line, at first the 
solenoid valve S.sub.1 is de-energized and then the solenoid valve S.sub.2 
is de-energized. In consequence, the vacuum which has been applied to the 
diaphragm is leaked to the atmosphere, so that the door 5a is moved 
towards the heater core. The changing opening degree of the door 5a is 
momentarily detected by the potentiometer PM1 and is stored in a writable 
erasable memory RAM in the microcomputer. 
A periodical comparison is made between the instant opening degree stored 
in the RAM and the command opening degree, and the microcomputer gives an 
instruction, when a coincidence is obtained, to make the control circuit C 
issue a control output for energizing the solenoid valve S.sub.2. The door 
5a is stopped at the instant position as the solenoid S.sub.2 is 
energized. 
Consequently, the chilled air discharged from the chilled air outlet 20 
adjacent to the upper half part of the driver's body and the warm air 
coming out of the warm air outlet 21 adjacent to the legs of the driver 
are controlled to have desired temperatures in accordance with the set 
temperature, i.e. the command compartment temperature. 
When the command opening degree .theta..sub.L of the second air mix door 5c 
read in the RAM of the microcomputer comes to take a value equal to or 
greater than 25.degree. or when the operation mode is switched to the 
defroster mode, the control circuit C issues a control output for 
deenergizing the solenoid valve S.sub.5 in accordance with the instruction 
given by the microcomputer. As the solenoid valve S.sub.5 is de-energized, 
the control door 5b is moved to the position shown by broken line so that 
the warm air outlet surface of the heater core wholly opens to the warm 
air duct 7b. 
The microcomputer delivers an instruction to the control circuit C to make 
the latter issue a control output for energizing the solenoid valves 
S.sub.6 and S.sub.7, when the condition expressed by the following formula 
(12) is met by the instant values of the room air temperature TR detected 
by the room air temperature sensor SR and written in the RAM of the 
microcomputer, command room air temperature T.sub.so and the command 
opening degree .theta..sub.U of the first air mix door 5a. As a result, 
the door 4 is switched to permit the sucking of the room air. 
EQU T.sub.R .gtoreq.T.sub.so and .theta..sub.U =0.degree. (12) 
Also, when the following conditions are met by the above-mentioned values, 
the control circuit C issues a control output for energizing the solenoid 
valve S.sub.6 while de-energizing the solenoid valve S.sub.7, in 
accordance with the instructions given by the microcomputer. Consequently, 
the door 4 is moved to an intermediate position where it permits the 
introduction of both of ambient air and the compartment air at the 
substantially equal rate. 
EQU (a) T.sub.R &lt;T.sub.so and .theta..sub.U =0.degree. (13) 
EQU (b) .theta..sub.U .noteq.0.degree. and T.sub.so &lt;T.sub.R (14) 
Furthermore, the microcomputer delivers an instruction to make the control 
circuit C issues a control output for de-energizing both of the solenoid 
valves S.sub.6 and S.sub.7 when the following condition is met by the 
above-mentioned values so that the door 4 is switched for introduction of 
the ambient air. 
EQU (a) .theta..sub.U .noteq.0.degree. and T.sub.so &gt;T.sub.R (15) 
(b) When the compressor is stopped. 
(c) In the defrosting mode. 
Furthermore, the control circuit C issues an output in accordance with an 
instruction given by the microcomputer to control the voltage applied to 
the fan motor 1 to control the air flow rate and start and stop of the fan 
in accordance with the condition shown in Table 1 below. 
TABLE 1 
______________________________________ 
Condition Voltage 
______________________________________ 
(1) (T.sub.R - T.sub.so) .ltoreq. -5[.degree.C.] 
10[V] 
(2) -5[.degree.C.] .ltoreq. (T.sub.R - T.sub.so) .ltoreq. -2[.degree.C.] 
(T.sub.so - T.sub.R) .times. 2[V] 
(3) -2[.degree.C.] .ltoreq. (T.sub.R - T.sub.so) .ltoreq. 5/3[.degree.C.] 
4[V] 
(4) 
5/3[.degree.C.] .ltoreq. (T.sub.R - T.sub.so) .ltoreq. 5[.degree.C.] 
##STR1## 
(5) 
5[.degree.C.] .ltoreq. (T.sub.R - T.sub.so) 
12[V] 
(6) Within 10 .+-. 2 seconds 
Voltage increased 
after start up gradually from 4[V] 
to 12[V] 
(7) Cooling water temp. below 
Zero 
35.degree. C. 
T.sub.R &lt; T.sub.so 
(8) Defroster mode 12[V] 
(9) 5 minutes after start up 
Lowered from 12[V] 
to 8[V] 
______________________________________ 
Also, the control circuit C effects the control of start and stop of the 
refrigerator (compressor) in a manner shown in Table 2 below, in 
accordance with an instruction given by the microcomputer. 
TABLE 2 
______________________________________ 
Condition State of control 
______________________________________ 
(1) (T.sub.so - T.sub.A) &gt; 15[.degree.C.] 
Stop 
and (T.sub.s - T.sub.R) &gt; 0 
(2) T.sub.A &lt; 5[.degree.C.] 
Stop 
(3) Blower motor stopped 
Stop 
(4) 20 seconds after stopping 
Restart and stop 
______________________________________ 
Also, the state of a hot water valve is controlled in a manner shown in 
Table 3 below by the control output from the control circuit C in 
accordance with the instruction given by the microcomputer. 
3 
______________________________________ 
Condition State 
______________________________________ 
(1) Cooling water temp. above 
35.degree. C. and all of following 
conditions met 
T.sub.R &gt; T.sub.so 
T.sub.A &gt; T.sub.s Open 
.theta..sub.L .noteq. 0.degree. C. 
(2) Defroster mode Open 
______________________________________ 
In the embodiment of the invention described hereinabove, the opening 
degrees of the first and second air mix doors 5a, 5c are controlled to 
follow up command values which are calculated from independent formulae 
programmed in the microcomputer, in accordance with the set temperature 
(command passage or compartment temperature T.sub.so) and various other 
temperature information. 
The air conditioner of the invention, however, can be embodied in such a 
form that the first and the second air mix doors 5a, 5c are operatively 
connected to each other mechanically so that the temperatures of air 
coming out from the chilled air outlet and warm air outlet are controlled 
while maintaining a constant temperature difference therebetween by the 
operation of a single control lever, as will be understood from the 
following description of FIG. 3. 
As shown in FIG. 3a connecting wire 11 is connected at its one end to the 
first air mix door 5a and at its other end to a control lever 13 provided 
on a control panel. The arrangement is such that the opening degree 
.theta..sub.U of the first air mix door 5a is increased to decrease the 
passage area of the main chilled air passage 9a as the control lever 13 is 
moved toward the WARM side. To the contrary, when the lever 13 is operated 
toward the COOL side, the area of the main chilled air passage is 
increased. The connecting wire 11 is clamped by a pair of clamp members 
12a and 12b. 
A link mechanism 10 is rotatably connected at its one end to the first air 
mix door 5a. A lever 5d strongly fixed to the shaft 53 of the second air 
mix door 5c extends to the opposite side of the shaft to the door. The 
other end of the link mechanism 10 is rotatably connected to the end of 
the lever 5d. 
Therefore, as the control lever 13 is operated in a direction for 
increasing the angle .theta..sub.2 of the first air mix door 5a, the 
second air mix door 5c is also moved to increase the angle .theta..sub.L. 
Namely, the point P of connection between the link 10 and the first air mix 
door 5a is moved along an arcuate path upwardly around the axis of 
rotation of the shaft 51. In consequence, the other end of the link 10 
pulls the end of the lever 3d upwardly. Since the lever 5d is fixed to the 
shaft 53, the shaft 53 is rotated clockwise as the end of the lever 5d is 
pulled upward, so that the second air mix door 5c fixed to the shaft 53 is 
rotated downwardly as viewed in the drawings around the axis of the shaft 
53. Consequently, the second air mix door 5c is controlled to an opening 
degree corresponding to the opening degree of the first air mix door 5a. 
FIG. 4 shows experimental data showing the change of the temperatures of 
air at the upper chilled air outlet 20 and the lower warm air outlet 21, 
in relation to the change in the opening degrees .theta..sub.U and 
.theta..sub.L. 
In FIG. 4, the axis of ordinate represents the temperature .degree.C. while 
the axis of abscissa represents the angle of opening .theta..sub.U and 
.theta..sub.L of the first and second air mix doors assuming that the 
positions of doors shown by broken lines correspond to opening degree 
0.degree.. 
A curve HIN shows the air temperature at the heater inlet, while HOUT shows 
the change of temperature at the heater outlet. The curve DOWN shows the 
change of temperature of controlled air comining out of the lower warm air 
outlet, while the curve UP shows the temperature change of the controlled 
air coming out of the upper warm air outlet. 
The curve S/V shows the temperature change of the conditioned air 
discharged from side vents provided at both ends of the instrument panel 
of the automobile, while C/V shows the change of the temperature of 
conditioned air discharged from a center vent provided at the central 
portion of the instrument panel. Finally, the curve EV shows the chilled 
air temperature at the outlet side of the evaporator. It is assumed here 
that no supply of hot water is made to the heater core 3 but the 
refrigerator operates solely when the opening degrees of both air mix 
doors 0.degree. and 5.degree. fall within the ranges of between 5a and 5c. 
In this range of operation, the door 4 has been switched for the 
introduction of passenger compartment air. 
The supply of hot water to the heater core 3 is commenced as the opening 
degrees of the air mix doors 5a and 5c are increased beyond 5.degree. and, 
at the same time, the door 4 is switched to the position where it permits 
the introduction of both of ambient air and the compartment air 
substantially at an equal flow rate. 
In this range, a part of the chilled air chilled by the refrigerator is 
heated again by the heater core 3 and the larger part of the heated warm 
air is introduced into the warm air duct 7b through the main warm air 
passage 8a while the other part is introduced into the chilled air duct 7a 
through the sub-warm air passage 8b. 
A part of the chilled air is introduced directly through the sub-chilled 
air passage 9b into the warm water duct 7b so as to be mixed with the warm 
air flowing therethrough, and the warm air as the mixture is discharged to 
the space around the driver's legs through the warm air outlet 21. On the 
other hand, a part of the warm air is introduced into the chilled air duct 
7a into which the major part of the chilled air is also introduced through 
the main chilled passage 9a. The chilled air as the mixture is then 
discharged towards the upper half part of the driver's body through the 
chilled air outlet 20. 
While the opening degrees of the air mix doors 5a and 5c are small, the 
flow rates of chilled air introduced into respective ducts 7a and 7b are 
comparatively large, so that the temperatures of conditioned air 
discharged from the outlets 20 and 21 are 10.degree. to 12.degree. C. and 
22.degree. to 23.degree. C., respectively. 
As the opening degrees of the air mix doors 5a and 5c are increased, the 
rate of the supply of chilled air into the heater core 3 is increased 
while the rate of introduction of chilled air into the ducts 7a and 7b is 
decreased. Consequently, the temperatures of the conditioned air from the 
air outlets 20 and 21 are raised as shown in FIG. 4. 
As the opening degree of the air mix doors 5a and 5c is increased beyond 
25.degree., the refrigerator or evaporator 2 is stopped and the door 4 is 
switched for the introduction of ambient air. 
Therefore, when the air mix doors 5a and 5b are controlled in the opening 
region exceeding 25.degree., fresh ambient air is introduced into the main 
and sub-chilled air passages 9a and 9b so that the warm air is mixed in 
the ducts 7a and 7b with the fresh ambient air and the mixtures are 
discharged through respective air outlets 20 and 21. 
The rate of introduction of the fresh ambient air is extremely small in 
this state as compared with the flow rate of the warm air, so that the air 
outlet temperatures are increased drastically as shown in FIG. 4. 
Provided that the speed of the fan is maintained constant, the rate of 
discharge of conditioned air from the cold air outlet is increased as the 
opening degrees of the air mix doors 5a and 5c approach 0.degree. and, to 
the contrary, the flow rate of the air from the air outlet 21 is increased 
as the opening degrees approach 30.degree.. 
In the described embodiment, the speed of the fan is maximized when the 
opening degrees of both air mix doors 5a and 5c are less than 5.degree. 
and more than 25.degree., and is minimized when the opening degrees fall 
within the range of between 12.5.degree. and 17.5.degree.. Within the 
ranges of between 5.degree. and 12.5.degree. and between 17.5.degree. and 
25.degree., the speed of the fan is gradually dcreased as the opening 
degrees approach 12.5.degree. and 17.5.degree., respectively. 
Therefore, as the opening degrees of the doors 5a and 5c approach 
5.degree., the flow rate of chilled air from the air outlet 20 is 
increased whereas, when the opening degrees approach 25.degree., the flow 
rate of air from the air outlet 21 is increased to impart a stronger feel 
of cooling and heating while maintaining an effect of keeping the head 
cool and the feet warm. 
The total air flow rate is decreased as the opening degrees of the doors 5a 
and 5b approach the range of between 12.5.degree. and 17.5.degree.. When 
the opening degrees of both doors 5a and 5c take values between 
12.5.degree. and 17.5.degree., air flows at small rates from the air 
outlets 20 and 21 with a suitable temperature difference of, for example, 
15.degree. C. therebetween. It is thus possible to obtain a sufficient 
effect of keeping the head cool and the feet warm, although the air flow 
rate is small. 
As has been described, according to the first embodiment of the invention, 
a part of the warm air is introduced into the chilled air duct leading to 
the upper air outlet opening in the upper part of the room space, and the 
rate of introduction of chilled air into the chilled air duct is 
controlled by a first air mix door. At the same time, a part of chilled 
air is introduced into the warm air duct leading to a lower air outlet 
opening to the lower part of the room space and the rate of supply of 
chilled air into the warm air duct is controlled by means of a second air 
mix door 5c. It is, therefore, possible to control the temperatures of air 
discharged from the upper and lower air outlets while realizing a desired 
temperature difference therebetween and, accordingly, to obtain an ideal 
effect of keeping the head cool and the feet warm. 
According to another embodiment of the invention, the opening degree of the 
second air mix door 5c is controlled in accordance with the opening degree 
of the first air mix door 5a. It is, therefore, possible to maintain a 
suitable temperature difference between the air discharged from the upper 
air outlet and the air discharged from the lower air outlet. 
According to still another form of the invention, the heater core 3 is 
disposed in a duct A such that the chilled air inlet surface and the warm 
air outlet surface of the heater core 3 extend substantially in parallel 
with the inner surfaces of the walls of the duct A. The first air mix door 
5a is disposed between the chilled air inlet surface of the heater core 3 
and the opposing wall surface of the duct A, while the second air mix door 
is disposed in the space between the warm air outlet surface of the heater 
core 3 and the opposing wall surface of the duct A. It is, therefore, 
possible to control the temperatures of chilled air and warm air 
discharged from the upper and lower air outlets, simply by changing the 
opening degrees of the air mix doors 5a, 5c only slightly. Although two 
air mix doors 5a, 5c were employed, the volume of the air conditioner as a 
whole was not increased substantially.