Method and apparatus for controlling a motor actuator under drive mode, and a recording medium storing a program for carrying out the method

When a difference in opening angle of an air-mixing door between a target position and an actual position is larger in value than a width of an insensitive band area, a mixing door actuator is driven to a heating side or a cooling side depending on the amount of the difference so as to have the air-mixing door reach its target position in a condition in which the insensitive band area is eliminated. When the difference is smaller than the predetermined band width, i.e., when a drive position of the mixing door actuator is in the insensitive band width, this band width is effected so that the mixing door actuator is stopped in operation to stabilize the operation.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a method and apparatus for controlling a 
motor actuator under drive mode, and to a recording medium storing a 
program for carrying out the method, and more particularly to improvements 
in accuracy of the control of motor actuators for driving air-conditioning 
doors used in a vehicle air-conditioning equipment and the like. 
2. Description of the Relate Art 
A conventional method of this kind is disclosed, for example, in Japanese 
Patent Publication No. Sho 59-43326 as a method for controlling a 
air-mixing door by means of a motor actuator of a vehicle air-conditioning 
equipment. The conventional method includes the steps of providing a 
so-called insensitive band area in the vicinity of a target opening angle 
and de-energizing the motor actuator when the air-mixing door reaches the 
in sensitive band area. 
On the other hand, for example, Japanese Patent Laid-Open No. Sho 61-287809 
discloses another method for controlling the air-mixing door by means of 
the motor actuator of the vehicle air-conditioning equipment. That method 
includes the steps of providing a so-called insensitive band area and a 
target opening angle in each of opposite sides of a standard opening angle 
of the air-mixing door and preventing the motor actuator from "hunting" in 
the vicinity of the standard opening angle of the air-mixing door to 
improve in control accuracy the motor actuator. 
There is further another conventional method of this kind, as disclosed in 
Japanese Patent Publication No. Hei 8-2200. That method includes steps of 
detecting a difference between the number of drive pulses required by a 
drive circuit for a stepping motor forming a motor actuator and that of 
actual pulses received by the stepping motor, judging the difference in 
size with reference to a pair of standard values, and driving the stepping 
motor with a predetermined number of pulses depending on the result of 
this judgment. The number of the drive pulses is reduced when the number 
of the drive pulses required by the drive circuit varies violently, which 
improves the service life of the stepping motor. 
As for the above-mentioned conventional method Patent Publication No. Sho 
59-43326, when the motor forming the motor actuator is of a type suffering 
from a so-called overrunning so that the motor cannot stop immediately 
after the supply of a drive signal to the motor is cut, such overrunning 
makes it possible for the motor to reach its target position in a 
condition in which the supply of the drive signal to the motor is cut at a 
time when the motor reaches the insensitive band area of the target 
position. However, when the motor is of a type with no overrunning after 
the supply of the drive signal to the motor is cut, as with a stepping 
motor, the motor immediately stops when it reaches the insensitive band 
area, which produces a difference between the target position and its 
actual position. Since this difference corresponds in size to the 
insensitive band area, the motor cannot reach its target position. This is 
a problem inherent in the above one of the conventional methods. 
On the other hand, as to the Japanese Patent Laid-Open No. Sho 61-287809 
disclosing another conventional method, it is necessary to provide both 
the target opening angle and its insensitive band area in each of opposite 
sides of the standard target opening angle, which makes the entire system 
complicated. Further, in the case of the above-mentioned Japanese Patent 
Publication No. Sho 59-43326, its controlling accuracy depends on the 
overrunning properties of the motor actuator, which causes many problems 
when the motor actuator is constructed of a stepping motor. 
This Japanese Patent Laid-Open No. Sho 61-287809 also discloses an 
apparatus for controlling the air-mixing door by means of the motor 
actuator of the vehicle air-conditioning equipment. In this apparatus, in 
order to avoid the problems described above, the motor actuator may be of 
a "no overrun" type. However, in this case, the insensitive band area is 
extremely reduced in width to substantially "zero", which forces the motor 
actuator to operate without stopping. Because, even, the slightest change 
in a signal representing the thermal environment, calculated in the 
vehicle air-conditioning equipment produces the drive signal being 
supplied to the motor actuator. Such restless operation (i.e., "hunting") 
of the motor actuator considerably reduces its services life, and produces 
harsh mechanical noise. 
On the other hand, in an apparatus for carrying out the method disclosed in 
the Japanese Patent Publication No. Hei 8-2200, in contrast with the two 
above-mentioned conventional techniques, the motor actuator is controlled 
so as to gradually approach its target position. Consequently, the motor 
actuator requires much more time to reach the target position than the 
others, which impairs the apparatus in responsibility. Further, since this 
apparatus has no insensitive band area in contrast with the others, the 
apparatus has poor stability in operation. In order to improve the 
apparatus in this respect, a timer is used to prevent the apparatus from 
operating for a predetermined period of time so as to improve the 
apparatus in stability in operation. However, the use of such timer 
complicates the apparatus in construction. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a method and apparatus 
for controlling a motor actuator, wherein the motor actuator is 
substantially free from overrunning in operation and excellent in 
controlling accuracy, stability in controlling operation, and in speed to 
reach its target position. 
It is another object of the present invention to provide a recording medium 
storing a program for carrying out the method of the present invention for 
controlling the motor actuator, wherein the motor actuator is 
substantially free from overrunning in operation and excellent in 
controlling accuracy, stability in controlling operation, and in speed to 
reach its target position. 
It is still further another object of the present invention to provide the 
method and apparatus for controlling the motor actuator, and a recording 
medium storing the program for carrying out the method, wherein the 
provision of the insensitive band area may be selectively effected and 
undone. 
According to a first aspect of the present invention, the above objects of 
the present invention are accomplished by providing a method as follows. 
An insensitive band area having a predetermined band width in the vicinity 
of a target position of the motor actuator is provided. Such provision of 
the insensitive band area is undone when the motor actuator is driven in 
an area outside the insensitive band area, which permits the motor 
actuator to be driven to the target position. The provision of the 
insensitive band area is effected after the actuator motor reaches the 
target position. The motor actuator is stopped from being driven when a 
drive position of the motor actuator is inside the insensitive band area. 
In the above method of the present invention in which the motor actuator is 
constructed of a motor with a minimum overrun, for example, a stepping 
motor, it is possible for the motor actuator to stop at its desired 
position without overrunning and is stable in operation thereafter. When 
the drive position of the motor actuator is in the the insensitive is 
driven in an area, which permits insensitive band area having the 
predetermined band width of the target position, the motor actuator is not 
driven as it is in the conventional methods, which stabilizes the motor 
actuator in operation. On the other hand, when the drive position of the 
motor actuator is out of the insensitive band area, the motor actuator is 
driven even when it enters the insensitive band area until it reaches its 
target drive position, which improves the controlling accuracy of the 
motor actuator. 
According to a second aspect of the present invention, the above objects of 
the present invention are accomplished by providing an apparatus for 
controlling a motor actuator under drive mode, provided with a drive means 
for driving the motor actuator in accordance with an input signal supplied 
from outside. The apparatus includes a position judging means for judging 
a drive position of the motor actuator and an actuation control means for 
controlling the motor actuator in operation. The actuation control means 
operates the drive means when the position judging means judges that the 
motor actuator is out of a predetermined range of a target drive position, 
and stops operation of the drive means when the position judging means 
judges that the motor actuator comes within the predetermined range of the 
target drive position. 
According to a third aspect of the present invention, the above objects of 
the present invention are accomplished by providing the apparatus for 
controlling the motor actuator under drive mode, as set forth in the 
second aspect of the present invention, wherein the motor actuator is 
operable for rotatably driving an air-mixing door used in a vehicle 
air-conditioning equipment. The position judging means is provided with a 
rotational motion recognition means for recognizing an angular position of 
the air-mixing door. The position judging means is constructed of the 
rotational motion recognition means and an angular difference judging 
means for judging whether or not a difference in opening angle of the 
air-mixing door between its target angle, which is calculated based on a 
desired air-outlet temperature according to a predetermined equation, and 
an actual angle, which corresponds to the angular position of the 
air-mixing door recognized by the rotational motion recognition means, 
exceeds a predetermined value. 
A judgment that the difference in opening angle of the air-mixing door 
judged by the angular difference judging means is larger than or equal to 
the predetermined value means that the actual opening angle of the 
air-mixing door is out of a predetermined range of the target opening 
angle, which corresponds to the fact that an actual position of the motor 
actuator is out of the predetermined range of the target drive position. A 
judgment that the difference in opening angle of the air-mixing door 
judged by the angular difference judging means is less than the 
predetermined value means that the actual opening angle of the air-mixing 
door comes within the predetermined range of the target opening angle, 
which corresponds the fact that the actual position of the motor actuator 
comes within the predetermined range of the target drive position. 
In the apparatus of the present invention having the above construction, 
all the drive means, the opening angle judging means and the actuation 
control means are realized by executing the predetermined program in a 
so-call CPU. 
In the apparatus of the present invention in which the motor actuator is 
constructed of a motor with a minimum overrun, for example, a stepping 
motor, it is possible for the motor actuator to stop at its desired 
position without overrunning and is stable in operation thereafter. When 
the angular difference judging means judges that the difference in opening 
angle of the air-mixing door between its target angle and the actual angle 
corresponding to the angular position of the air-mixing door, exceeds the 
predetermined value, the motor actuator is driven by both the drive means 
and the actuation control means until the air-mixing door reaches its 
target opening angle, which improves the apparatus of the present 
invention in controlling accuracy. After the air-mixing door reaches its 
target opening angle, the insensitive band area provided in each of 
opposite sides of this target opening angle is effected. When the 
air-mixing door is in this sensitive band area, the motor actuator is not 
driven to stabilize its operation around the target position. 
According to a fourth aspect of the present invention, the above objects of 
the present invention are accomplished by providing the apparatus for 
controlling the motor actuator under drive mode, as set forth in the 
second aspect of the present invention, wherein the motor actuator is 
operable for rotatably driving an air-mixing door used in a vehicle 
air-conditioning equipment. The position judging means is provided with an 
air temperature detection means for detecting a temperature of air inside 
a vehicle. The position judging means is constructed of the air 
temperature detection means and a temperature difference judging means for 
judging whether or not a difference in temperature of air between any two 
of its target air-outlet temperature calculated based on various data 
inputted from outside, its estimated temperature calculated based on the 
opening angle of the air-mixing door, and its actual temperature detected 
by the air temperature detection means is larger than or equal to a 
predetermined value. A judgment that the difference in temperature of air 
judged by the temperature difference judging means is larger than or equal 
to the predetermined value means that the actual opening angle of the 
air-mixing door is out of a predetermined range of the target opening 
angle, which corresponds to the fact that an actual position of the motor 
actuator is out of the predetermined range of the target drive position. A 
judgment that the difference in temperature of air judged by the 
temperature difference judging means is less than the predetermined value 
means that the actual opening angle of the air-mixing door comes within 
the predetermined range of the target opening angle, which corresponds the 
fact that the actual position of the motor actuator comes within the 
predetermined range of the target drive position. 
In the apparatus of the present invention having the above construction, 
all the drive means, the opening angle judging means and the actuation 
control means are realized by executing the predetermined program in the 
CPU. 
In the apparatus of the present invention in which the motor actuator is 
constructed of a motor with a minimum overrun, for example, with a 
stepping motor, it is possible for the motor actuator to stop at its 
desired position without overrunning and is stable in operation 
thereafter. When the temperature difference judging means judges that the 
temperature difference in air between the air-outlet temperature in a 
vehicle compartment and the actual temperature exceeds the predetermined 
value, the motor actuator is driven by both the actuation control means 
and the drive means until the air-mixing door reaches its target opening 
angle, so that the apparatus of the present invention is improved in 
controlling accuracy. After the air-mixing door reaches its target opening 
angle, the in sensitive band area provided in each of opposite sides of 
the target opening angle is effected. When the air-mixing door is in the 
insensitive band area, the motor actuator is not driven, which stabilizes 
the motor actuator in operation around its target position. 
According to a fifth aspect of the present invention, the above objects of 
the present invention are accomplished by providing a recording medium 
storing a program for carrying out a method for controlling a motor 
actuator under drive mode. The program instructs the CPU (computer) to 
provide an insensitive band area having a predetermined band width in the 
vicinity of a target position of the motor actuator, to undo such 
provision of the insensitive band area when the motor actuator is driven 
in an area outside the insensitive band area, which permits the motor 
actuator to be driven to the target position, to effect the provision of 
the insensitive band area after the actuator motor reaches the target 
position, and to stop the motor actuator from being driven when a drive 
position of the motor actuator is inside the insensitive band area.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Hereinbelow, the present invention will be described in detail with 
reference to the accompanying drawings. 
Incidentally, many changes and modifications can be made to the embodiments 
of the present invention without departing from its spirit, it is intended 
that all matters given in the following description and the accompanying 
drawings shall be interpreted to be illustrative only, and not as a 
limitation to the scope of the present invention. 
In the following embodiments, the present invention is applied to a motor 
actuator of a vehicle air-conditioning equipment, which is schematically 
shown in FIG. 1. 
As shown in FIG. 1, in this air-conditioning equipment, an upstream side of 
an air-conditioning duct 1 is divided into a fresh-air intake opening 2 
and an indoor-air intake opening 3. Provided in such branch portion of the 
duct 1 between these intake openings 2, 3 is an intake door 4 which 
switches its intake air from fresh air to the indoor air or vice versa. 
Sequentially provided in a downstream side of the air-conditioning duct 1 
are a blower motor 5, an evaporator 6, and a heater core 7. Incidentally, 
the evaporator 6 is combined with a compressor (not shown) and like 
components to form a refrigerant cycle of the vehicle air-conditioning 
equipment. 
On the other hand, the heater core 7 is eccentrically mounted in the 
air-conditioning duct 1 so as to form a by-pass passage 8 between a side 
wall portion of the duct 1 and the heater core 7. Provided in front of 
this heater core 7 is the air-mixing door 9 which controls both the amount 
of air passing through the heater core 7 and that passing through the 
by-pass passage 8. 
A downstream side of the air-conditioning duct 1 is divided into a vent 
opening 10, a defroster opening 11 and a heater opening 12. All of these 
openings 10, 11, 12 open into a passenger compartment of the vehicle, and 
are provided with mode doors 13a, 13b, 13c, respectively. 
Each of the air-mixing door 9, and the mode doors 13a, 13b, 13c is 
rotatably driven by motor actuators 14, 15 each of which is constructed of 
a stepping motor (not shown). More specifically, the air-mixing door 9 is 
driven by the motor actuator 14 serving as an air-mixing door actuator 
(shown in FIG. 1), while the mode doors 13a, 13b, 13c are driven by the 
motor actuator 15 serving as a mode door actuator, as shown in FIG. 1. 
On the other hand, the blower motor 5 is driven by a blower driving circuit 
16. 
A control unit 17 (i.e., C/U shown in FIG. 1) is substantially constructed 
of a so-called CPU (not shown), and controls in operation the 
air-conditioning equipment which comprises the blower driving circuit 16, 
the air-mixing door actuator 14 and the mode door actuator 15. 
Incidentally, in the embodiment shown in FIG. 1, among various sensors used 
therein, ones only shown are: an evaporator temperature sensor 18 for 
detecting a temperature Te of the evaporator 6, the temperature Te being 
required when the air-mixing door 9 is controlled by the control unit 17 
according to flowcharts shown in FIGS. 2 to 4; an outside air temperature 
sensor 19 for detecting an outside air temperature T.sub.AM ; a solar 
radiation sensor 20 for detecting a quantity Q.sub.SUN of solar radiation; 
a passenger compartment temperature sensor 21 for detecting a passenger 
compartment temperature T.sub.INC ; and, an air-mixing door opening angle 
sensor 22 for detecting an actual opening angle .THETA..sub.A completed in 
the air-mixing door 9. 
FIG. 2 shows an upper part of a flowchart for a subroutine of a first 
embodiment of the method of the present invention for controlling the 
mixing door actuator 14 used in the air-conditioning equipment shown in 
FIG. 1. 
In operation, as shown in FIG. 2, first, in a step 100, it is judged 
whether or not a temperature setting lever (not shown) of the vehicle 
air-conditioning equipment is set at a position of "FULL HEAT" (i.e., FH: 
maximum heating). When it is judged that the lever is set at "FH", this 
step 100 is followed by a subsequent step 128 in which a target opening 
angle .THETA..sub.A ' is set at 100 percent in order to set the 
temperature setting lever (not show) at the "FULL HEAT" position. After 
that, the step 128 is followed by a subsequent step 132a (shown in FIG. 
3). 
On the other hand, in the above step 100 shown in FIG. 2, when it is not 
judged that the lever is set at "FH", this step 100 is followed by a 
subsequent step 102 in which it is judged whether or not a temperature 
setting lever (not shown) of the vehicle air-conditioning equipment is set 
at a position of "FULL COOL" (i.e., FC: maximum cooling). In the step 102, 
when it is judged that the lever is set at "FC", the step 102 is followed 
by a subsequent step 130 in which a target opening angle .THETA..sub.A ' 
is set at 0 percent in order to set the temperature setting lever (not 
show) at the "FULL COOL" position. After that, the step 130 is followed by 
the step 132a (shown in FIG. 3). 
On the other hand, in the above step 102 shown in FIG. 2 , when it is not 
judged that the lever is set at "FC", this step 102 is followed by a 
subsequent step 104 in which it is judged whether or not the vehicle 
air-conditioning equipment is operated. When it is judged that the 
equipment is operated, the step 104 is followed by a subsequent step 108 
in which the evaporator temperature Te is set at 3 degrees centigrade. On 
the other hand, when it is not judged that the equipment is operated, the 
step 104 is followed by a subsequent step 106 in which the evaporator 
temperature Te is set at a temperature detected by the evaporator 
temperature sensor 18. 
In the above description, the evaporator temperature Te is fixed at a 
temperature of 3 degrees centigrade since the actual temperature of the 
evaporator 6 is variable due to the presence of the evaporator defrost 
cycle. The use of such variable temperature clearly makes it difficult for 
the air-mixing door 9 to exhibit good operational stability. Incidentally, 
the defrost cycle is performed in the vehicle air-conditioning equipment 
by disconnecting the compressor (not shown) from the refrigerating circuit 
by energizing an electromagnetic clutch (not shown), the defrost cycle 
being required to prevent the evaporator 6 from freezing. 
After the evaporator temperature Te is set at a temperature of 3 degrees 
centigrade in the step 108, the step 108 is followed by a subsequent step 
110. In this step 110, it is judged whether or not the mode doors 13a, 
13b, 13c are in vent positions. When it is judged that the mode doors 13a, 
13b, 13c are not in the vent positions, the step 110 is followed by a step 
116. On the other hand, when it is judged that the mode doors 13a, 13b, 
13c are in the vent positions, the step 110 is followed by a step 112 in 
which it is judged whether or not a general signal T is smaller than or 
equal to a predetermined value (i.e., -5 in the flowchart shown in FIG. 
2). 
This general signal T represents a thermal load inside the passenger 
compartment of the vehicle, and is calculated from a predetermined 
equation using necessary parameters such as a temperature of the interior 
of the vehicle, the outside air temperature, a solar radiation 
temperature, an evaporator temperature, and the like. 
In the step 112, when it is judged that the general signal is not smaller 
than or equal to the predetermined value (i.e., -5), the step 112 is 
followed by a step 116. On the other hand, when it is judged that the 
general signal is smaller than or equal to the predetermined value (i.e., 
-5), the step 112 is followed by a step 114 in which the general signal T 
is set at the predetermined value (i.e., -5). Then, the step 114 is 
followed by the step 116. 
In the step 116, it is judged whether or not the present target opening 
angle .THETA..sub.A ' is smaller than or equal to, for example, 60 
percent. 
This target opening angle .THETA..sub.A ' represents a target opening angle 
of the air-mixing door 9, and is calculated from a predetermined equation 
in a step 126 (described later) using the general signal T, evaporator 
temperature Te, and constants .alpha., .beta.. 
In the step 116, when it is judged that the target opening angle 
.THETA..sub.A ' is smaller than or equal to 60 percent, the step 116 is 
followed by a subsequent step 118. In this step 118, as shown in FIG. 2, 
the constants .alpha. and .beta. are set at K3 and K4, respectively. Then, 
the step 118 is followed by a subsequent step 120. In this step 120, the 
hysteresis limits, which define the insensitive band area, are set at plus 
or minus 5 percent. After that, the step 120 is followed by a step 126. 
On the other hand, in the step 116, when it is not judged that the target 
opening angle .THETA..sub.A ' is smaller than or equal to 60 percent, the 
step 116 is followed by a subsequent step 122. In this step 122, as shown 
in FIG. 2, the constants .alpha. and .beta. are set at K1 and K2, 
respectively. Then, the step 122 is followed by a subsequent step 124. In 
this step 124, the hysteresis limits, which define the insensitive band 
area, are set at plus or minus 2.5 percent. After that, the step 124 is 
followed by the step 126. 
In the above, the reason why the constants .alpha., .beta. are changed, 
depending on the amount of the target opening angle .THETA..sub.A ' is as 
follows. 
Namely, the relation between the opening angle of the air-mixing door 9 and 
a temperature of air introduced into the passenger compartment of the 
vehicle through the heater core 7 is approximately defined by a 
predetermined linear equation having an inflection point where the 
equation's constants (i.e., .alpha., .beta.) representing temperature 
control characteristics of the heater core 7 change. This inflection point 
corresponds to the target opening angle of 60 percent in the flowchart 
shown in FIG. 2. Consequently, such equation's constants .alpha., .beta. 
are changed to proper values, depending on the amount of the target 
opening angle .THETA..sub.A '. 
In the step 126, the target opening angle .THETA..sub.A ' is calculated 
from a predetermined equation using the general signal T, evaporator 
temperature Te and the constants .alpha., .beta.. After that, the step 126 
is followed by a step 132a shown in FIG. 3. 
In the step 132a, it is judged whether or not a flag H is 1. When it is 
judged that the flag H is 1, the step 132a is followed by a step 148. On 
the other hand, when it is not judged that the flag H is 1, the step 132a 
is followed by a subsequent step 132b in which it is judged whether or not 
the flag H is 0. When it is judged that the flag H is 0, the step 132b is 
followed by a subsequent step 134a. On the other hand, when it is not 
judge that the flag H is 0, the step 132b is followed by a step 140. 
In the step 134a, it is judged whether or not a value of "-(.THETA..sub.A 
'-.THETA..sub.A)" exceeds the hysteresis limits. When it is judged that 
the value of "-(.THETA..sub.A '-.THETA..sub.A)" exceeds the hysteresis 
limits, the step 134a is followed by the step 148. On the other hand, when 
it is not judged that the value of "-(.THETA..sub.A '-.THETA..sub.A)" 
exceeds the hysteresis limits, the step 134a is followed by a subsequent 
step 134b in which it is judged whether or not an absolute value of 
(.THETA..sub.A '-.THETA..sub.A) is smaller than the hysteresis limits 
which are already determined in the above step 120 or 124. 
In the step 134b, when it is judged that the absolute value of 
(.THETA..sub.A '-.THETA..sub.A) is smaller than the hysteresis limits, the 
step 134b is followed by a subsequent step 136 in which the flag H is set 
at 0 again, since the air-mixing door is just in the target position or 
within the hysteresis limits thereof determined in the step 120 or 124, 
and, therefore there is no need for further drive of the air-mixing door 
actuator 14. After that, the step 136 is followed by a subsequent step 138 
where the air-mixing door actuator 14 stops in operation, so that the 
subroutine shown in FIG. 3 is completed. 
On the other hand, in the step 134a, when it is judged that the value of 
"-(.THETA..sub.A '-.THETA..sub.A)" exceeds the hysteresis limits 
determined in the step 120 or 124 (shown in FIG. 2), the step 134a is 
followed by the step 148 in which the flag H is set at 1. After that, the 
step 148 is followed by a subsequent step 150 in which it is judged 
whether or not the target opening angle .THETA..sub.A ' is larger than or 
equal to the actual opening angle of the air-mixing door 9. 
In the step 150, when it is not judged that the target opening angle 
.THETA..sub.A ' is larger than or equal to the actual opening angle 
.THETA..sub.A of the air-mixing door 9 (i.e., the target opening angle 
.THETA..sub.A ' is smaller than the actual opening angle .THETA..sub.A), 
this fact means that the air-mixing door 9 is not properly positioned, and 
must be moved toward its closed side (i.e., full cool side). Consequently, 
the step 150 is followed by a subsequent step 152 in which the air-mixing 
door 9 is moved toward its closed side by further driving the air-mixing 
door actuator 14, so that the subroutine shown in FIG. 3 is completed. 
Consequently, in a condition in which the flag H is 1 and the target 
opening angle .THETA..sub.A ' is not larger than or equal to the actual 
opening angle .THETA..sub.A, regardless of the presence of the hysteresis 
limits, the air-mixing door actuator 14 is driven until the air-mixing 
door 9 reaches the target opening angle .THETA..sub.A '. After the 
air-mixing door 9 reaches target opening angle .THETA..sub.A ', since the 
target opening angle .THETA..sub.A ' becomes larger than or equal to the 
actual opening angle .THETA..sub.A, it is possible to set the flag H at 0 
in the step 136, as shown in FIG. 3, by which the provision of the 
hysteresis limits is effected, as is effected in the steps 134a, 134b. 
On the other hand, in the step 150, when it is judged that the target 
opening angle .THETA..sub.A ' is larger than or equal to the actual 
opening angle .THETA..sub.A, the step 150 is followed by the step 136 in 
which the flag H is set at 0 to prevent the air-mixing door actuator 14 
from being further driven. Consequently, the step 136 is followed by the 
step 138 in which the air-mixing door actuator 14 stops in operation, so 
that the subroutine shown in FIG. 3 is completed. 
Further, in the step 134b, when it is judged that the absolute value of 
(.THETA..sub.A '-.THETA..sub.A) is not smaller than the hysteresis limits, 
i.e., that this absolute value is larger than or equal to the hysteresis 
limits, the step 134b is followed by a step 140 in which the flag H is set 
at 2. After that, the step 140 is followed by a subsequent step 142 in 
which it is judged whether or not the actual opening angle .THETA..sub.A 
is larger than or equal to the target opening angle .THETA..sub.A ', as 
shown in FIG. 3. 
In the step 142, when it is not judged that the actual opening angle 
.THETA..sub.A is larger than or equal to the target opening angle 
.THETA..sub.A ', this fact means that the air-mixing door 9 is not 
properly positioned outside the hysteresis limits, and must be moved 
toward its opened side (i.e., full heat side). Consequently, the step 142 
is followed by a subsequent step 146 in which the air-mixing door 9 is 
moved toward its opened side by further driving the air-mixing door 
actuator 14, so that the subroutine shown in FIG. 3 is completed. 
Consequently, in a condition in which the flag H is 2 and the actual 
opening angle .THETA..sub.A is not larger than or equal to the target 
opening angle .THETA..sub.A ', regardless of the presence of the 
hysteresis limits, the air-mixing door actuator 14 is driven until the 
air-mixing door 9 reaches the target opening angle .THETA..sub.A '. After 
the air-mixing door 9 reaches the target opening angle .THETA..sub.A ', 
since the actual opening angle .THETA..sub.A becomes larger than or equal 
to the target opening angle .THETA..sub.A ', it is possible to set the 
flag H at 0 in the step 136, as shown in FIG. 3, by which the provision of 
the hysteresis limits is effected, as is effected in the steps 134a, 134b. 
On the other hand, in the step 142, when it is judged that the actual 
opening angle .THETA..sub.A is larger than or equal to the target opening 
angle .THETA..sub.A ', a further drive of the air-mixing door actuator 14 
is not required. Consequently, the step 142 is followed by the steps 136, 
138 in the same manner as described above, so that the subroutine shown in 
FIG. 3 is completed. 
The method of the present invention for controlling the air-mixing door 9 
is summarized as follows, in comparison with the conventional method, with 
reference to FIGS. 5 to 7. 
FIG. 6 shows a completed opening angle of the air-mixing door 9 with a 
target air-outlet temperature, for a characteristic line graph G5 which is 
indicated in thick solid line and represents the target opening angle, and 
for another characteristic line graph G6 which is indicated in phantom 
line and represents a lower hysteresis limit. On the other hand, another 
characteristic line graph G7, indicated in thin solid line, represents an 
upper hysteresis limits. 
In the graph shown in FIG. 6, a fully opened position of the air-mixing 
door 9 is denoted by 100 percent corresponding to a full heat position, 
while a fully closed position of the door 9 is denoted by 0 percent 
corresponding to a full cool position. 
In the prior art, the motor actuator is permitted to overrun due to 
inertia, without stopping immediately after its drive signal is cut. When 
the motor actuator is controlled in the conventional manner in which the 
drive signal issued to the motor actuator is cut when the air-mixing door 
driven by the motor actuator reaches the hysteresis limits, the actual 
opening angle of the air-mixing door thus completed may near the line 
graph G5 (which represents the target opening angle) due to the 
overrunning effect of the motor actuator, but not reach the target opening 
angle, as shown in the line graph G8. 
Also in the prior art, when the motor actuator free from any overrun is 
used, since the motor actuator may immediately stop when it reaches the 
hysteresis limits, the actual opening angle of the air-mixing door 9 is 
defined by the line graph G6 as shown in FIG. 7, so that the actual 
opening angle thus completed is smaller than its target opening angle by a 
minus one of the hysteresis limits. 
In contrast with this, in the method of the present invention for 
controlling the air-mixing door 9, when the air-mixing door actuator 14 
(shown in FIG. 1) is outside the hysteresis limits in its drive mode, 
since it is possible to drive the actuator 14 without considering the 
presence of the hysteresis limits, the air-mixing door 9 may reach the 
target opening angle. After the air-mixing door 9 reaches the target 
opening angle, the hysteresis limits are effected as in the prior art. 
Consequently, in this case, the actual opening angle of the air-mixing 
door 9 is defined by the line graph G4 which lies between the line graph 
G1 representing the target opening angle and the line graph G2 
representing a lower one of the hysteresis limits. As is clear from FIG. 
5, the line graph G4 is of a zigzag line type, and shown in dotted line. 
In the first embodiment of the present invention shown in FIG. 1, the drive 
means is realized by the air-mixing door actuator 14. The apparatus of the 
present invention shown in FIG. 1 comprises a rotational motion 
recognition means which is realized by an opening angle sensor 22. 
Further, the apparatus of the present invention includes: an angular 
difference judging means which is realized by the steps 134a, 134b (shown 
in FIG. 3) executed in the control unit 17 (shown in FIG. 1) and an 
actuation control means which is realized by the steps 132a and 132b, 136 
to 152 executed in the control unit 17. 
Incidentally, the rotational motion recognition means does not necessarily 
have to use the opening angle sensor 22. Namely, in order to detect the 
rotational position, it is also possible for the rotational motion 
recognition means to use the number of pulses, which is stored in the 
control unit 17 and supplied to the stepping motor (not shown) used in the 
air-mixing door actuator 14. 
Now, a second embodiment of the method of the present invention for 
controlling the air-mixing door actuator by means of the control unit 17 
will be described with reference to a flowchart of a subroutine shown in 
FIG. 4. 
In operation, first, in a step 200 of the flowchart shown in FIG. 4, 
various constants, for example such as the constants A, B, C, D, E, F, G 
and the like used in the following equations are initialized. This step 
200 is followed by a subsequent step 202 in which the target opening angle 
.THETA..sub.A ' of the air-mixing door 9 is calculated from a 
predetermined equation (not shown). 
After that, the step 202 is followed by a subsequent step 204 in which one 
of the constants, i.e., Wo, is calculated using a predetermined conversion 
table or map which is experimentally obtained. The constant Wo is used to 
determine an air-outlet temperature deviation S (described later). 
More particularly, the constant Wo can be represented by the following 
experimental formula: 
EQU Wo=f(B.times.T.sub.AM -D.times.T.sub.INC) 
where: B and D are constants; T.sub.AM is a temperature of the outside air; 
and, T.sub.INC is a temperature of the interior of the passenger 
compartment of the vehicle. 
After that, the step 204 is followed by a subsequent step 206. Calculated 
in this step 206 is the air-outlet temperature deviation S which 
represents a difference between a target air-outlet temperature and an 
actual air-outlet temperature (i.e., a temperature of the interior of the 
passenger compartment of the vehicle). Incidentally, in this step 206: 
T.sub.PTC is a setting temperature set by the temperature setting lever 
(not shown) used in the apparatus of the present invention shown in FIG. 
1; T'.sub.PTC is a compensated version of the setting temperature 
T.sub.PTC ; and, Q'.sub.SUN is a compensated quantity of solar radiation. 
After the air-outlet temperature deviation S is calculated, the step 206 is 
followed by a subsequent step 208a. In this step 208a, it is judged 
whether or not the setting temperature T.sub.PTC is a predetermined lower 
limit temperature of, for example, 18 degrees centigrade, as shown in FIG. 
4. When it is judged that the setting temperature T.sub.PTC is the lower 
limit temperature of 18 degrees centigrade, the step 208a is followed by a 
step 220. On the other hand, in the step 208a, when it is not judged that 
the setting temperature T.sub.PTC is the lower limit temperature of 18 
degrees centigrade, the step 208a is followed by a subsequent step 208b. 
In this step 208b, it is judged whether or not the setting temperature 
T.sub.PTC is within a range of from 19.5 to 31.5 degrees centigrade. 
When it is judged that the setting temperature T.sub.PTC is within a range 
of from 19.5 to 31.5 degrees centigrade, the step 208b is followed by a 
subsequent step 210a. On the other hand, when in the step 208b, it is not 
judged that the setting temperature T.sub.PTC is within a range of from 
19.5 to 31.5 degrees centigrade, this fact means that the setting 
temperature T.sub.PTC is set at a predetermined upper limit temperature 
of, for example, 32 degrees centigrade. Consequently, the step 208b is 
followed by a step 218. 
Consequently, in the step 208b, when it is found that the setting 
temperature T.sub.PTC is set at the predetermined upper limit temperature 
of, for example, 32 degrees centigrade, it is necessary to fully open the 
air-mixing door 9. Therefore, in the step 218 following the step 208b, the 
air-mixing door actuator 14 is driven so as to set the air-mixing door 9 
at its fully opened position corresponding to a "FULL HEAT" position, so 
that the subroutine shown in FIG. 4 is completed. 
Further, in the step 208a, when it is judged that the setting temperature 
T.sub.PTC is set at the predetermined lower limit temperature of 18 
degrees centigrade, it is necessary to fully close the air-mixing door 9. 
Therefore, in the step 220 following the step 208a, the air-mixing door 
actuator 14 is driven so as to set the air-mixing door 9 at its fully 
closed position (i.e., 0 percent shown in FIG. 5) corresponding to a "FULL 
COOL" position, so that the subroutine shown in FIG. 4 is completed. 
On the other hand, in the step 208b, when it is judged that the setting 
temperature T.sub.PTC is within a range of from 19.5 to 31.5 degrees 
centigrade, the step 208b is followed by the step 210a in which it is 
judged whether or not the flag H is "1". When it is judged that the flag H 
is "1", the step 210a is followed by a step 228. When it is not judged 
that the flag H is "1", the step 210a is followed by a subsequent step 
210b in which it is judged whether or not the flag H is "0". When it is 
judged that the flag H is "0", the step 210b is followed by a subsequent 
step 212a. On the other hand, when it is not judged that the flag H is 
"0", this fact means that the flag H is "2". Consequently, the step 210b 
is followed by a step 222 in which the flag H is set at "2". 
In the step 212a following the step 210b, it is judged whether or not the 
air-outlet temperature deviation S calculated in the above is smaller than 
a predetermined value of "-SO". When it is judged that the air-outlet 
temperature deviation S is smaller than the predetermined value of "-SO", 
the step 212a is followed by the step 228. On the other hand, in the step 
212a, when it is not judged that the air-outlet temperature deviation S is 
smaller than the predetermined value of "-SO", the step 212a is followed 
by a subsequent step 212b. In this step 212b, it is judged whether or not 
the absolute value of the air-outlet temperature deviation S is smaller 
than or equal to the predetermined value of "SO". When it is judged that 
the absolute value of the air-outlet temperature deviation S is smaller 
than or equal to the predetermined value of "SO", this fact means that the 
target temperature is accomplished, and, therefore there is no need for 
further drive of the air-mixing door actuator 14. Consequently, the step 
212b is followed by a subsequent step 214 in which the flag H is set at 
"0", so that the air-mixing door actuator 14 stops in operation in a step 
216 following the step 214, whereby the subroutine shown in FIG. 4 is 
completed. 
Consequently, the predetermined value "SO" serves as the insensitive band 
area limits. 
On the other hand, in the step 212b, when it is not judged that the 
absolute value of the air-outlet temperature deviation S is smaller than 
or equal to the predetermined value "SO", this fact means that the 
air-outlet temperature deviation S is larger than the predetermined value 
"SO". In other words, this fact means that the target air-outlet 
temperature is larger than the actual temperature of the interior of the 
passenger compartment of the vehicle. Consequently, the step 212b is 
followed by the step 222 in which the flag H is set at "2", as shown in 
FIG. 4. The step 222 is followed by a subsequent step 224. In this step 
224, it is judged whether or not the air-outlet temperature deviation S is 
larger than 0. When it is judged that the air-outlet temperature deviation 
S is larger than 0, it is necessary to move the air-mixing door 9 to its 
fully opened position (i.e., "FULL HEAT" position). Consequently, the step 
224 is followed by a subsequent step 226 in which the air-mixing door 
actuator 14 is driven so as to move the air-mixing door 9 to its fully 
opened position, whereby the subroutine shown in FIG. 4 is completed. 
Consequently, so far as the flag H is "2" and the air-outlet temperature 
deviation S is larger than 0, the air-mixing door actuator 14 is driven 
until the air-mixing door 9 reaches the target opening angle .THETA..sub.A 
', regardless of the presence of the hysteresis limits. After the 
air-mixing door 9 reaches the target opening angle .THETA..sub.A ', since 
the air-outlet temperature deviation S is not larger than 0, the flag H is 
set at "0" in the step 214 following the step 224, to effect the provision 
of the hysteresis limits. 
On the other hand, in the step 224 following the step 222, when it is 
judged that the air-outlet temperature deviation S is not larger than 0, 
this fact means that there is no need for further drive of the air-mixing 
door actuator 14. Consequently, the step 224 is followed by the step 214. 
After that the same processing procedures as those described in the above 
as to the steps 214, 216 are used, so that the subroutine shown in FIG. 4 
is completed. 
Further, in the step 212a, when it is judged that the air-outlet 
temperature deviation S is smaller than the predetermined value of "-SO", 
this fact means that the actual temperature of the interior of the 
passenger compartment of the vehicle is higher than the target 
temperature. Consequently, in the step 228 following the step 212a, the 
flag H is set at "1". This step 228 is then followed by a subsequent step 
230 in which it is judged whether or not the air-outlet temperature 
deviation is smaller than 0. When it is judged that air-outlet temperature 
deviation is smaller than 0, this fact means that the air-mixing door 9 
should be moved to its fully closed position (i.e., to its "FULL COOL" 
position). Consequently, the step 230 is followed by a subsequent step 
232. In this step 232, the air-mixing door actuator 14 is so driven as to 
move the air-mixing door 9 to its fully closed position (i.e., 0 percent 
shown in FIG. 5), whereby the subroutine shown in FIG. 4 is completed. 
Consequently, so long as the flag H is "1" and the air-outlet temperature 
deviation S is smaller than 0, the air-mixing door actuator 14 is driven 
until the air-mixing door 9 reaches the target opening angle .THETA..sub.A 
', regardless of the presence of the hysteresis limits. After the 
air-mixing door 9 reaches the target opening angle .THETA..sub.A ', since 
the air-outlet temperature deviation S is not smaller than 0, there is no 
need for further drive of the air-mixing door actuator 14. Consequently, 
the step 230 is followed by the step 214. Thereafter, the same processing 
procedures as those described in the above as to the steps 214, 216 are 
used, so that the subroutine shown in FIG. 4 is completed. 
As described above, in this second embodiment of the method of the present 
invention, when the air-outlet temperature deviation S is within a 
predetermined range in either the plus or minus direction, the air-mixing 
door actuator 14 is not driven (see the steps 212a, 212b, 214, 216). In 
contrast with this, when the air-outlet temperature deviation S is out of 
such predetermined range in either the plus or minus direction, the 
air-mixing door actuator 14 is driven so as to move the air-mixing door 9 
to its necessary side (see the steps 212a, 212b, 222, 224, 226, 228, 230, 
232), whereby the air-mixing door 9 is set at its target opening angle, as 
in the first embodiment of the method of the present invention. 
In a summary of the above, as shown in the graph of FIG. 5 wherein the 
X-axis is graduated in temperature (centigrade) and the Y-axis is 
graduated in opening angle of the air-mixing door 9 (percent), in the 
second embodiment of the method of the present invention, a target line 
graph G1 shows the target opening angle of the air-mixing door 9, while a 
lower limit line graph G2 shows a lower hysteresis limit, and is smaller 
in opening angle than the target line graph G1 by the predetermined amount 
"SO". On the other hand, an upper limit line graph G3 shows an upper 
hysteresis limit, and is larger in opening angle than the target line 
graph G1 by the predetermined amount "SO". 
Consequently, an actual line graph G4, which is shown in dotted line 
between the line graphs G1 and G2, shows the actual opening angle of the 
air-mixing door 9 in operation. 
Incidentally, in the second embodiment of the present invention described 
above, the air-mixing door actuator 14 forms a drive means used in the 
apparatus of the present invention, and the passenger compartment 
temperature sensor 21 forms an air temperature detection means for 
detecting a temperature of air inside the vehicle. 
Further, in the second embodiment of the present invention executing of the 
steps 212a, 212b in the flowchart shown in FIG. 4 realizes a temperature 
difference judging means, and executing of the steps 210a, 210b, 214, 216, 
and 222 to 232 in the control unit 17 realizes an actuator control means. 
In the embodiments of the present invention described above, though the 
air-mixing door actuator 14 is descried to be constructed of a stepping 
motor, it is also possible that the air-mixing door actuator 14 is 
constructed of any other motor of a no-overrun type, or constructed of a 
suitable motor with a little overrun, provided that such overrun does not 
affect the method and apparatus of the present invention in operation. 
In the above description, the control unit 17 substantially serves as a 
computer, and, therefore previously stores the program described in the 
flowchart shown in FIGS. 2 to 4. However, such program is not necessarily 
stored in the control unit 17, since the program may be stored in any 
other suitable recording medium. In this case, the program is retrieved 
from such recording medium by a suitable reader, and inputted to the 
control unit 17 so as to be executed therein. 
For example, as shown in FIG. 8, the above recording medium may be 
constructed of a floppy disk 30 which carries the program. In this case, a 
floppy disk drive unit 31 is connected with the control unit 17, so that 
the program is retrieved from the floppy disk 30 by the disk drive unit 31 
and inputted to the control unit 17. 
Incidentally, the recording medium may be constructed of any other suitable 
means, such as, for example magnetic tapes, hard disks and the like. 
As described above, in the present invention, the motor actuators are 
improved with respect to the control accuracy in the drive mode of the 
motor actuator. When the insensitive band area is provided in the vicinity 
of the target value to stabilize the operation as in the prior art, such 
provision of the insensitive band area is undone in case the motor 
actuator is driven from outside the insensitive band area, which enables 
the motor actuator to reach its target value. Consequently, this improves 
the motor actuator in control accuracy and in control speed. Further, in 
the present invention, after the motor actuator reaches its target value, 
the provision of the insensitive band area is effected so as to stabilize 
the control operation in the vicinity of the target value. 
Further, as for the provision of the insensitive band area, switching from 
undoing to effecting or vice versa of the insensitive band area can be 
easily accomplished by only executing the program without requiring any 
special circuit, which makes it possible for the apparatus of the present 
invention to have a simple construction.