Air conditioning system for vehicles

In a vehicular air conditioning system, an air-distribution ratio control range is determined in accordance with a set rotational speed of a blower and the air distribution ratio is controlled in accordance with a solar radiation direction within the control range, whereby more comfortable air conditioning can be realized. The system may be arranged in such a way that the correction amount of air discharge in the case where the direction of the solar radiation is not within the a prescribed range is less than that in the case where the direction is within the perscribed range, in order to prevent unnecessarily large amount of air discharge.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an air conditioning system for vehicles 
capable of controlling the air-distribution in accordance with the 
direction of the sun. 
2. Description of the Prior Art 
There have been proposed various air conditioning systems for vehicles of 
the type in which the ratio between the amounts of air discharged to the 
left and right sides of the passenger compartment (hereinafter referred to 
as the air-distribution ratio) is changed depending upon the amount of 
solar radiation striking the left and right sides of the passenger 
compartment, for keeping the passenger compartment in a properly 
air-conditioned state. 
Japanese Patent Application Public Disclosure No. Hei 1-190520, for 
example, discloses an air conditioning system for vehicles, in which an 
air-distribution door for regulating the air-distribution ratio is 
controlled in response to an output signal generated by a solar radiation 
detector and at least a certain lower limit amount of air is supplied to 
each side of the passenger compartment by the air-distribution control 
operation irrespective of the direction of the sun relative to the 
traveling direction of the vehicle. 
In this conventional system in which the air-distribution ratio is 
controlled in response to the direction of the sun, the air-distribution 
door is controlled so as to supply a greater amount of air to the side of 
the passenger compartment receiving more solar radiation than to the other 
side. Although this arrangement can eliminate imbalances in heat quantity 
within the passenger compartment, it does not give adequate consideration 
to controlling such factors as the flow pattern and flow volume of the air 
blowing on the occupants so as to increase their comfort. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide an improved air 
conditioning system for vehicles which is capable of directing appropriate 
amounts of air toward the occupant(s) in the case where the 
air-distribution ratio is controlled in response to the direction of the 
sun. 
It is another object of the present invention to provide an air 
conditioning system for vehicles, in which the air-distribution ratio 
control range is adjusted in relation to the amount of air discharge. 
It is a further object of the present invention to provide an air 
conditioning system for vehicles which is capable of avoiding excessive 
air discharge during the air-distribution ratio controlling operation. 
According to the present invention, in a vehicular air conditioning system 
in which an air flow produced by a blower is conditioned and discharged 
into a passenger compartment, the system comprises a regulating member for 
regulating the air-distribution ratio, a plurality of solar radiation 
quantity detectors for detecting the quantities of solar radiation at a 
plurality of points in the passenger compartment, a calculating means 
responsive to the solar radiation quantity detectors for calculating the 
direction of the solar radiation relative to the traveling direction of 
the vehicle, a first setting means for setting the rotational speed of the 
blower, a second setting means responsive to the first setting means for 
setting the air-distribution ratio control range, and a control means for 
controlling the regulating member to obtain an air-distribution ratio 
suitable for the calculated solar radiation direction within the control 
range. Thus, the air-distribution ratio control range is limited in 
accordance with the amount of air supplied by the blower, whereby more 
comfortable air conditioning can be realized. 
According to another feature of the present invention, in a vehicular air 
conditioning system in which an air flow produced by a blower is 
conditioned and discharged into a passenger compartment, the system 
comprises a regulating member for regulating the air-distribution ratio, a 
plurality of solar radiation quantity detectors for detecting the 
quantities of solar radiation at a plurality of points in the passenger 
compartment, a calculating means responsive to the solar radiation 
quantity detectors for calculating the direction of the solar radiation 
relative to the traveling direction of the vehicle, a first control means 
responsive to the calculating means for controlling the regulating member 
to obtain a suitable air-distribution ratio for the calculated direction 
of the solar radiation when the calculated direction of solar radiation is 
outside a prescribed range, a detecting means responsive to the 
calculating means for detecting the current control condition of the 
air-distribution ratio, and a second control means responsive to the 
detecting means for controlling the blower in such a way that the 
correction amount of air discharge in the case where the direction of the 
solar radiation is not within the prescribed range is less than that in 
the case where the direction of the solar radiation is within the 
prescribed range. This arrangement effectively prevents unnecessarily 
large amount of air discharge. 
The invention will be better understood and other objects and advantages 
thereof will be more apparent from the following detailed description of 
preferred embodiments with reference to the accompanying drawings.

DESCRIPTION OF PREFERRED EMBODIMENTS 
FIG. 1 diagrammatically shows an air conditioning system for vehicles. The 
air conditioning system includes an air-flow duct 1 having an outside air 
intake 3 and a recirculating air intake 2 disposed at an upstream end 
thereofin a bifurcated fashion. A selecting door 4 is disposed at the 
junction between the two air intakes 2, 3 and is actuated by an actuator 
45a driven by a driving circuit 47a so as to select between an air intake 
mode in which recirculated air is introduced into the air-flow duct 1 and 
one in which outside air is introduced thereinto. 
A blower 5 driven by a driving circuit 47b is disposed in the air-flow duct 
1 adjacent to the air intakes 2, 3 for blowing air through the air-flow 
duct 1 in the direction of a passenger compartment. The duct 1 also 
includes an evaporator 6 disposed downstream of the blower 5. The 
evaporator 6 is connected by piping with a compressor 46 driven by a 
driving circuit 47c to jointly constitute a well-known refrigeration 
system or cycle. 
A heater core 7 is disposed downstream of the evaporator 6, and an air-mix 
door (a temperature control damper) 8 is disposed upstream of the heater 
core 7. The angular position of the air-mix door 8 (i.e. the opening of 
the air-mix door 8) is regulated by an actuator 45c driven by a driving 
circuit 47e so that the ratio between the air flowing through the heater 
core 7 and the air bypassing the heater core 7 is changed to thereby 
control the temperature of the air discharged from the air conditioning 
system. 
The air-flow duct 1 has at its downstream end a defroster outlet 11, a vent 
outlet 9 and a lower outlet 10, which are provided in branched fashion and 
all open into the passenger compartment. Three mode doors, namely, a vent 
door 12, a foot door 13 and a defroster door 14, are disposed adjacent to 
the respective outlets 9, 10 and 11. The mode doors 12 to 14 are 
controlled by an actuator 45d driven by a driving circuit 47f to establish 
a desired air-discharge mode. 
The vent outlet 9 has a left upper air outlet 15 opening to the left side 
of the passenger compartment, a right upper air outlet 16 opening to the 
right side of the passenger compartment, and a central upper air outlet 17 
opening to the center of the passenger compartment disposed centrally 
between the right and left upper air outlets 16 and 15. A partition plate 
18 is disposed at the junction between these air outlets 15 to 17 in such 
a way that the opening of the central upper air outlet 17 is divided into 
two. An air-distribution door 19 is disposed in front of the partition 
plate 18 and controlled by an actuator 45e driven by a driving circuit 47g 
to adjust the air-distribution ratio. 
The air conditioning system further includes a bypass duct 20 communicated 
with the air-flow duct 1 in such a way that one end of the bypass duct 20 
opens at the portion between the evaporator 6 and the air-mix door 8 and 
the other end opens at the portion between the vent door 12 and the 
air-distribution door 19. A bypass door 21 is disposed at one end of the 
bypass duct 20 and cool air is supplied appropriately to the vent outlet 9 
by regulating the position of the bypass door 21 by means of an actuator 
45b driven by a driving circuit 47d, whereby fine adjustment of the air 
discharge in temperature can be carried out. 
The system has a microcomputer 22 of well-known design, including a central 
processing unit (CPU), a read only memory (ROM), a random access memory 
(RAM), an input/output port (I/O), and the like (none of which are shown). 
A signal selected by a multiplexer (MPX) 23 is applied to an 
analog-to-digital (A/D) converter 24 for converting it into a digital form 
and the obtained digital signal is supplied to the microcomputer 22. The 
microcomputer 22 also receives various signals from a console panel 25, as 
described later on. The console panel 25 is equipped with a mode setter 26 
for setting air-discharge modes, an intake mode setter 27 for setting the 
intake mode, an air-compressor (A/C) switch 28 for activating the 
compressor 46 in the refrigeration cycle, a blower intensity setter 29 for 
setting the intensity of the blower 5, an AUTO switch 30 for activating 
automatic air conditioning operation, and an OFF switch 31 for stopping 
the automatic air conditioning operation. All the switches and setters 
sent output signals to the microcomputer 22. 
The MPX 23 is connected with integral type solar radiation sensors 32 and 
33 which are installed on the left and right sides of the upper surface of 
the vehicle's instrument panel, inside air temperature sensors 34 and 35 
installed at upper and lower parts of the passenger compartment for 
detecting the temperatures of the upper and lower portions of the 
passenger compartment, an outside air temperature sensor 36 for detecting 
the temperature of the outside air, a duct sensor 37 for detecting the 
temperature of the air at the evaporator 6, and a water temperature sensor 
38 for detecting the temperature of the engine coolant which supplies heat 
to the heater core 7, an air-distribution switch 39 for controlling the 
air-distribution door 19 manually, and a temperature setter 40 disposed on 
the console panel 25, for setting the target temperature of the inside 
air. The MPX 23 is further connected with first to fourth position sensors 
41 to 44 for supplying MPX 23 with feedback signals indicating the current 
positions of the air-distribution door 19, the mode doors 12 to 14, the 
air-mix door 8, and the bypass door 21. 
The microcomputer 22 executes a control program stored therein for 
controlling operations of the actuator 45a for actuating selecting door 4, 
the blower 5, the compressor 46, the actuator 45b for actuating the bypass 
door 21, the actuator 45c for actuating the air-mix door 8, the actuator 
45d for actuating the mode doors 12 to 14, and the actuator 45e for 
actuating the air-distribution door 19. To achieve the control operations, 
the microcomputer 22 produces control signals on the basis of the input 
signals supplied from the A/D converter 24 and the console panel 25, and 
the control signals are applied to the driving circuits 47a to 47g. 
The air-distribution control operation and the air discharge control 
operation which is carried out in relation to the air-distribution control 
will now be described with reference to the flowchart shown in FIG. 2. 
The microcomputer 22 starts executing the control program from step 100, 
and the operation moves to step 102 in which the output signals supplied 
from the A/D converter 24 and the console panel 25 are read in. 
After data input in step 102, a solar radiation quantity T.sub.S based on 
the output signals T.sub.SL, T.sub.SR of the left and right solar 
radiation sensors 32, 33 is calculated in step 104. The solar radiation 
quantity calculation of step 104 is conducted in accordance with the 
subroutine shown in FIG. 3. 
Referring to FIG. 3, an interpolated value (T.sub.SR +T.sub.SL)/K.sub.2 as 
indicated by the dotted line in FIG. 4 is calculated in step 60, based on 
the output signal T.sub.SL from the left solar radiation sensor 32 and the 
output signal T.sub.SR from the right solar radiation sensor 33. The 
interpolated value is a control value T.sub.S. The interpolated value is 
needed because the respective solar radiation sensors 32 and 33 have 
different directivities as indicated by the solid lines in FIG. 4 and 
hence the outputs from the solar radiation sensors 32, 33 have to be 
compensated in order to obtain a constant output irrespective of the 
direction of the sun. K.sub.2 is a calculation constant determined such 
that the interpolated value has a peak which is equal to the peaks of the 
output signals T.sub.SL and T.sub.SR. In the succeeding steps, the control 
value T.sub.S is replaced by the largest of the three values T.sub.SL, 
(T.sub.SR +T.sub.SL)/K.sub.2 and T.sub.SR (steps 62 to 70). 
Returning to FIG. 2, after the calculation of the solar radiation quantity 
T.sub.S in step 104, the procedure advances to step 106 for calculating 
the solar radiation direction T.sub.D. This calculation is performed in 
accordance with the subroutine shown in FIG. 5. In this case, the solar 
radiation direction T.sub.D is represented by the angle of the sun with 
respect to the traveling direction of the vehicle as illustrated in FIG. 
6. 
Referring to FIG. 5, in step 80 the magnitude of the output signal T.sub.SL 
of the left solar radiation sensor 32 is compared with the output signal 
T.sub.SR of the right solar radiation sensor 33. If T.sub.SL is greater 
than or equal to T.sub.SR, the procedure goes to step 82 in which a left 
side coefficient T.sub.DL is calculated as 
##EQU1## 
where K.sub.1 is a calculation constant. 
Conversely, if T.sub.SR is greater than T.sub.SL, the control advances to 
step 84 to obtain a right side coefficient T.sub.DR as 
##EQU2## 
In step 86 the solar radiation direction T.sub.D is determined from the 
coefficient T.sub.DL obtained in step 82 or the coefficient T.sub.DR 
obtained in step 84. 
Returning to FIG. 2, after the execution of step 106, the operation moves 
to step 108, wherein discrimination is made as to whether or not the 
air-discharge mode is vent mode, that is, whether or not the door 12 is 
open. 
When it is found that the vent outlet 9 is closed, the result in step 108 
is NO and the operation moves to step 110, wherein control of the 
air-distribution door 19 is discontinued. This is because, in general, 
there is no need to conduct right-to-left air-distribution control when 
little or no air is not being discharged from the vent outlet 9. With this 
arrangement, the actuator 45e need be used less often, prolonging its 
service life, and, moreover, the noise made by driving the 
air-distribution door 19 is avoided during operation in which no 
air-distribution control is needed. 
On the other hand, the result of the discrimination in step 108 is YES when 
it is found that the vent mode is selected, and the operation moves to 
step 112, wherein discrimination is made on the basis of the position of 
the switch 39 for switching between manual and automatic air-distribution 
control for determining whether or not the automatic control mode is 
selected. Alternatively, the discrimination in step 112 can be carried 
out, for example, on the basis of the temperature of the passenger 
compartment and the solar radiation quantity. When it is found in step 112 
that the switch 39 is set to the manual operation mode, the result of the 
discrimination in step 112 is NO, and the operation moves to step 110. In 
this case, a desired air-distribution ratio can be manually set by means 
of a setting lever (not shown). 
On the other hand, if it is found in step 112 that the automatic control 
mode has been selected, the operation moves to step 114, wherein the range 
over which air-distribution control is allowed is determined in accordance 
with the the blower intensity setting. 
How the air-distribution control range is set will now be described with 
reference to FIGS. 7 to 9. 
The automatic air-distribution control, which will be described in detail 
later, is carried out in accordance with the characteristic curve 
illustrated in FIG. 7. Specifically, when the solar radiation direction 
T.sub.D is within the range between -30.degree. and +30.degree., the 
right-to-left air-distribution ratio, namely, the ratio between the amount 
of air discharge from the outlet(s) to the right of the partition 18 and 
the amount of air discharge from the outlet(s) to the left thereof, is 
fixed at 1:1. As the solar radiation direction T.sub.D changes from 
-30.degree. to -70.degree., the air-distribution to the left side of the 
passenger compartment increases progressively. When the solar radiation 
direction T.sub.D exceeds -70.degree., the left-to-right air-distribution 
ratio is fixed at 5:1 (the lower limit value of .beta.). Conversely, the 
air-distribution to the right of the passenger compartment increases 
progressively as the solar radiation direction T.sub.D changes from 
+30.degree. to +70.degree.. When the solar radiation direction exceeds 
+70.degree., the left-to-right air-distribution ratio is fixed at 1:5 (the 
upper limit value of .alpha.). In the following description, the range of 
solar radiation directions T.sub.D between -30.degree. to +30.degree. is 
referred to as the "A zone", and the remaining range of solar radiation 
directions T.sub.D is referred to as the "B zone", as illustrated in FIG. 
7. 
In step 114 the upper and lower limit values .alpha. and .beta. of the 
air-distribution ratio are determined in response to the set rotational 
speed BS of the blower 5 in accordance with the characteristic curves 
shown in FIGS. 8 and 9, respectively. Thus the range of allowable 
air-distribution control is set in accordance with the amount of air 
discharged from the blower 5. 
In the next step 115, the air-distribution is controlled automatically in 
accordance with the characteristic curve shown in FIG. 7. The values of 
.alpha. and .beta. determined in step 114 are used in step 115. After the 
execution of step 115, the operation moves to step 116, wherein necessary 
control other than that of the air-distribution is executed. The operation 
moves to other routine through step 117. When the result of the 
discrimination in step 108 or 112 is NO, the operation moves step 110. 
After the execution of the step 110, the operation moves to step 116, 
skipping the execution of steps 114 and 115. 
According to the control program shown in FIG. 2, since the range of 
allowable air-distribution control is expanded as the set rotational speed 
BS of the blower 5 is lowered, the interior of the passenger compartment 
is uniformly air-conditioned when the amount of air discharge is large, 
while a large change in the amount of air discharge can be suppressed 
during the air-distribution control when the amount of air discharged by 
the blower 5 is small, whereby discomfort to the occupant(s) can be 
reduced. Thus, it is possible to realize a smooth transition in the amount 
of air discharge in accordance with the variation of the feeling of the 
occupant(s), and also to maintain an excellent temperature balance inside 
the passenger compartment. 
FIG. 10 is a flowchart showing another type of control operation, in which 
the amount of air discharge is controlled on the basis of the 
air-distribution. Since the operations in steps 100 to 112 are the same as 
those in the flowchart shown in FIG. 2, they will not be described again 
here. 
When it is found in step 112 that automatic air-distribution control is 
selected, the operation moves from step 112 to step 120, wherein the 
air-distribution is automatically controlled on the basis of the solar 
radiation direction T.sub.D obtained by the calculation in step 106. 
The automatic air-distribution control is carried out in step 120 in 
accordance with the characteristic curve shown in FIG. 11. Specifically, 
when the solar radiation direction T.sub.D is within the range of 
-30.degree. and +30.degree., the air-distribution ratio is fixed at 1:1. 
However, the air-distribution ratio changes linearly in the case when the 
solar radiation direction T.sub.D changes between -30.degree. and 
-70.degree., or between 30.degree. and 70.degree.. In the range of the 
solar radiation direction T.sub.D below -70.degree., the lower limit value 
of the air-distribution ratio is fixed at 5:1 (20%). In the range of the 
solar radiation direction T.sub.D exceeding +70.degree., the upper limit 
value of the air-distribution ratio is fixed at 1:5 (80%). In the 
following description, the range of solar radiation directions T.sub.D 
between -50.degree. to +50.degree. will be referred to as the "X zone", 
and the remaining range of solar radiation directions T.sub.D will be 
referred to as the "Y zone". 
In the next step 122, discrimination is made as to whether the solar 
radiation direction T.sub.D is within the X zone or within the Y zone. 
When it is found in step 122 that the solar radiation direction T.sub.D is 
within the X zone, in which the air-distribution ratio is small enough to 
avoid a local air conditioning problem, the operation moves to step 124, 
in which the rotational speed of the lower 5 is controlled so as to 
increase as the solar radiation quantity increases, whereby the amount of 
air discharge is corrected. After this, the operation moves to step 126, 
wherein the target temperature T.sub.1 of the discharged air is calculated 
as 
EQU T.sub.1 =A.multidot.T.sub.d -B.multidot.T.sub.r -C.multidot.T.sub.a 
-D.multidot.T.sub.s +E (3) 
wherein, A, B, C and D are calculation coefficients, E is a correction 
value, T.sub.d is the set temperature, T.sub.r is the temperature in the 
passenger compartment, and T.sub.a is the temperature of the outside air. 
As will be understood from FIG. 10, the operation moves to step 126 after 
the execution of step 110 in the case where the determination in either 
step 108 or 112 is NO. 
In the next step 128, the amount of air discharge is determined in the 
well-known conventional manner on the basis of the value of T.sub.1 
calculated in step 126 in accordance with the basic characteristic pattern 
shown by the solid line in the graph in step 128. A lower limit amount J 
of air discharge in the basic characteristic pattern is set to be equal to 
the amount of discharge air determined in step 124 in accordance with 
solar radiation quantity. 
On the other hand when it is found in step 122 that the solar radiation 
direction T.sub.D is within the Y zone, the operation moves to step 130, 
wherein the lower limit amount J of air discharge is determined in 
accordance with the solar radiation quantity. In this embodiment, as will 
be understood from the graph indicated in step 130, the lower limit amount 
J of air discharge is fixed at a certain constant value irrespective of 
changes in the solar radiation quantity when the solar radiation direction 
T.sub.D is within the Y zone. As will be easily understood from a 
comparison of the characteristic curves of steps 124 and 130, the lower 
limit J is smaller in the case where the solar radiation direction T.sub.D 
is within the X zone, wherein the right-to-left air-distribution ratio is 
within the range of 35% and 65%, than in the case where the solar 
radiation direction T.sub.D is within the Y zone, wherein the 
right-to-left air-distribution ratio is not within the aforesaid range. 
The operation then moves to step 132, wherein a discharged air target 
temperature T.sub.2 for the Y zone is calculated as 
EQU T.sub.2 =A.multidot.Td-B.multidot.Ta-K.multidot.Ts+E (4) 
wherein, K is a calculation constant, which is set to be larger value than 
the calculation coefficient D of formula (3). Accordingly, the discharged 
air target temperature T.sub.2 for the Y zone is lower than the target 
temperature T.sub.1 for the X zone. The correction amount of air discharge 
determined in step 128 on the basis of the temperature T.sub.2 represented 
by the formula (4) is smaller than that used in the X zone. 
After the execution of step 128, the operation moves to step 134, wherein 
other control operations are carried out, and the operation advances 
through step 132 to other routine. 
According to the arrangement shown in FIG. 10, the amount of air discharge 
is controlled in accordance with the air-distribution control, and the 
correction amount of air discharge determined in the case where the 
right-to-left air-distribution ratio is within the predetermined range (X 
zone) is smaller than that determined in the case where the right-to-left 
air-distribution ratio is not within the predetermined range. Therefore, 
it is possible to prevent an excessive amount of air from being discharged 
during the air-distribution control, which enhances the comfort of the 
occupants. On the other hand, since the amount of correction is increased 
when the air-distribution control is carried out in the Y zone outside the 
X zone, an appropriate total amount of air discharge from all of the 
outlets can be obtained. As a result, better air conditioning can be 
realized than is possible with the conventional air conditioning system.