Note: Descriptions are shown in the official language in which they were submitted.
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AIR CONDITIONING APPARATUS
FIELD OF THE INVENTION
The present invention relates to an air conditioning device including a PTC
heater.
BACKGROUND OF THE INVENTION
A conventional air conditioning device is disclosed in JP-A-H08-152179. This
air conditioning device is integrally formed such that an indoor portion
within a room
is arranged in its front portion and an outdoor portion outside the room is
arranged in
its rear portion. In the outdoor portion, a compressor that operates a
refrigeration cycle
and an outdoor heat exchanger that is connected to the compressor are
arranged. An
inlet port and an outlet port are open in the indoor portion; an air blower,
an indoor
heat exchanger and a PTC (positive temperature coefficient) heater are
arranged
within the indoor portion. The indoor heat exchanger is connected to the
compressor
through a refrigerant pipe. The air blower sucks in air through the inlet
port, and
discharges, through the outlet port, the air that has exchanged heat with the
indoor
heat exchanger and the PTC heater.
When a cooling operation is started, the compressor is driven and thus the
refrigeration cycle is operated, the indoor heat exchanger functions as an
evaporator
on the low temperature side of the refrigeration cycle, and the outdoor heat
exchanger
functions as a condenser on the high temperature side of the refrigeration
cycle. Air
within the room flows, by driving of the air blower, into the indoor portion
through the
inlet port; the air whose temperature is decreased by exchanging heat with the
indoor
heat exchanger is discharged through the outlet port into the room. In this
way, the
room is cooled.
When a heating operation is started, the compressor is driven and thus the
refrigeration cycle is operated, the indoor heat exchanger functions as a
condenser on
the high temperature side of the refrigeration cycle, and the outdoor heat
exchanger
functions as an evaporator on the low temperature side of the refrigeration
cycle. The
air within the room flows, by driving of the air blower, into the indoor
portion through
the inlet port, and the air is increased in temperature by exchanging heat
with the
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indoor heat exchanger. The air that has flowed into the indoor portion by
driving of the
PTC heater is further increased in temperature. The heated air is discharged
through
the outlet port into the room, and thus the room is heated.
The PTC heater is formed by sandwiching a heating element having a PTC
characteristic between electrodes; voltage is applied across the electrodes to
drive the
PTC heater. In a stable region, when the temperature of the heating element is
increased, the resistance of the heating element is decreased or is
substantially
constant whereas, in a rise region, the resistance is rapidly increased when
the
temperature exceeds a rise temperature.
When the PTC heater is driven in the rise region and thus its temperature is
increased, the resistance of the heating element is rapidly increased, and the
current
and the amount of heat generated are decreased; when its temperature is
decreased,
the resistance of the heating element is rapidly decreased, and the current
and the
amount of heat generated are increased. In this way, the amount of heat
generated
by the PTC heater becomes constant, and thus it is possible not only to easily
produce
warm air having a predetermined temperature but also to prevent the PTC heater
from
being overheated.
However, in the conventional air conditioning device described above, when the
temperature within the room exceeds the set temperature, the heating ability
of the
PTC heater is reduced whereas when the temperature within the room drops below
the set temperature, the heating ability of the PTC heater is enhanced. Here,
when the
heating ability of the PTC heater is changed by voltage, a temperature drop
resulting
from a decrease in voltage causes the resistance of the heating element to be
rapidly
reduced, and an overcurrent flows through the PTC heater, with the result that
the
power supply capacity is disadvantageously exceeded.
On the other hand, when the heating ability of the PTC heater is changed by
the
volume of air blown by the air blower, if the temperature within the room is
increased,
the number of revolutions of the air blower is decreased whereas if the
temperature
within the room is decreased, the number of revolutions of the air blower is
increased.
Here, since the PTC heater continues to produce a predetermined amount of
heat, the
temperature near the air conditioning device is increased, with the result
that the
temperature within the room disadvantageously becomes uneven.
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Hence, when the compressor is stopped in the heating operation, the average
heating ability of the PTC heater is kept high and the heating is performed
only by the
PTC heater, an overcurrent is produced or the temperature within the room
becomes
uneven. It is therefore common to decrease the average heating ability of the
PTC
heater, drive the compressor and use the PTC heater in an auxiliary manner.
Thus,
it is likely that the ability of the PTC heater can not be sufficiently
utilized and that the
heating ability is reduced such as when the outside temperature is low.
SUMMARY OF THE INVENTION
An aspect of the present invention is to provide an air conditioning device
that
can make a temperature within a room uniform and prevent an overcurrent from
flowing through a PTC heater.
According to an embodiment of the present invention, there is provided an air
conditioning device including a PTC heater in which, in a stable region, when
a
temperature of the PTC heater is increased, a resistance of the PTC heater is
decreased or is substantially constant whereas, in a rise region, the
resistance is
rapidly increased when the temperature exceeds a rise temperature; a heater
control
portion that controls a duty ratio of the PTC heater; a temperature detection
portion
that detects a temperature within a room; and an air blower that generates an
air
current which exchanges heat with the PTC heater. In the air conditioning
device, a
heating operation is performed by discharging air heated by the PTC heater
into the
room, when the temperature within the room is within a low temperature range
including a region whose temperature is lower than a set temperature, the duty
ratio
is set at 100%, and the PTC heater is driven in the rise region, when the
temperature
within the room is within a high temperature range whose temperatures are
higher
than the set temperature, the PTC heater is stopped, and when the temperature
within
the room is within an intermediate temperature range between the low
temperature
range and the high temperature range, the duty ratio is set at a predetermined
duty
ratio, and the PTC heater is driven in the stable region.
In this configuration, when the heating operation is started, the PTC heater
and
the air blower are driven. The air current generated by the air blower
exchanges heat
with the PTC heater, and the air heated by the PTC heater is discharged into
the
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room. The duty ratio of the PTC heater is controlled by the heater control
portion;
when the temperature within the room detected by the temperature detection
portion
is within the low temperature range including the region whose temperature is
lower
than the set temperature, the PTC heater is driven at a duty ratio of 100%.
Here, the
temperature of the PTC heater is kept at the temperature in the rise region
where the
resistance is rapidly changed as the temperature changes. Thus, it is possible
to
stabilize the amount of heat generated by the PTC heater and to prevent the
PTC
heater from being overheated.
When the temperature within the room is increased to reach the intermediate
temperature range, the PTC heater is driven at a predetermined duty ratio.
Here, the
temperature of the PTC heater is kept at the temperature in the stable region
where,
when the temperature is increased, the resistance is decreased or is
substantially
constant, and thus the amount of heat generated by the PTC heater is
decreased.
Since the duty ratio is reduced until the temperature within the room reaches
the
temperature in the stable region, the resistance of the PTC heater is
decreased but
the current is reduced, and thus an overcurrent is prevented from being
produced.
When the temperature within the room is further increased to reach the high
temperature range, the PTC heater is stopped, and the temperature of the PTC
heater
is reduced.
Preferably, in the air conditioning device of the present invention configured
as
described above, the intermediate temperature range is further divided into a
plurality
of auxiliary temperature ranges, and, when the temperature within the room is
within
a high temperature-side auxiliary temperature range, the duty ratio of the PTC
heater
is set lower than a duty ratio at the time of a low temperature-side auxiliary
temperature range. In this configuration, the temperature within the room
reaches the
low temperature-side auxiliary temperature range of the intermediate
temperature
range, the PTC heater is driven at a predetermined duty ratio. When the
temperature
within the room is increased to reach the high temperature-side auxiliary
temperature
range of the intermediate temperature range, the PTC heater is driven at a
duty ratio
that is obtained by decreasing the duty ratio by a predetermined amount from
the low
temperature-side auxiliary temperature range.
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Preferably, in the air conditioning device of the present invention configured
as
described above, when the temperature within the room is within the high
temperature-side auxiliary temperature range, the number of revolutions of the
air
blower is changed such that the number of revolutions of the air blower is
lower than
the number of revolutions of the air blower at the time of the low temperature-
side
auxiliary temperature range. In this configuration, when the temperature of
the PTC
heater is decreased in the high temperature side auxiliary temperature range
because
the duty ratio is reduced, the number of revolutions of the air blower is
decreased, and
cold air is prevented from being discharged.
Preferably, in the air conditioning device of the present invention configured
as
described above, when the temperature within the room is within the high
temperature
range, the number of revolutions of the air blower is changed such that the
number of
revolutions of the air blower is lower than the number of revolutions of the
air blower
at the time of the low temperature range. In this configuration, when the
temperature
is decreased in the high temperature range due to the stop of the PTC heater,
the
number of revolutions of the air blower is decreased, and cold air is
prevented from
being discharged. The air blower may be stopped in the high temperature range.
Preferably, in the air conditioning device of the present invention configured
as
described above, a current detection portion that detects a current which
flows through
the PTC heater is further provided, and processing in which, in an early stage
after the
temperature within the room enters the low temperature range, the duty ratio
is set
higher than a duty ratio at the time of the intermediate temperature range,
and in
which, when the current detected by the current detection portion is lower
than a
predetermined value, the duty ratio is increased by a predetermined amount is
repeated until the duty ratio reaches 100%.
In this configuration, when the temperature within the room reaches the low
temperature range, the heater control portion applies, for example, a voltage
at a duty
ratio of 50% to the PTC heater. The current detection portion detects the
current
through the PTC heater at predetermined intervals, and, when the current
through the
PTC heater is lower than a predetermined value, the duty ratio is increased
by, for
example, 10%. This processing is repeated and thus the duty ratio is gradually
increased, and, when the duty ratio reaches 100%, the PTC heater is driven.
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Preferably, in the air conditioning device of the present invention configured
as
described above, in the early stage after the temperature within the room
enters the
low temperature range, the air blower is driven at the first number of
revolutions, until
the duty ratio of the PTC heater reaches 100%, the number of revolutions of
the air
blower is gradually decreased from the first number of revolution, and, when
the duty
ratio of the PTC heater reaches 100%, the air blower is driven at the second
number
of revolutions that is larger than the first number of revolution.
In this configuration, when the temperature within the room reaches the low
temperature range, the air blower is rotated at the first number of
revolutions, and the
number of revolutions is gradually reduced, with the result that the air
blower is rotated
at a low speed. Then, when the duty ratio of the PTC heater reaches 100%, the
air
blower is rotated at the second number of revolutions, that is, at a high
speed.
Preferably, in the air conditioning device of the present invention configured
as
described above, when the current detected by the current detection portion is
higher
than a predetermined value, the duty ratio of the PTC heater is decreased by a
predetermined amount. In this configuration, when the current detected by the
current
detection portion is higher than the predetermined value, the duty ratio of
the PTC
heater is decreased by, for example, 10%. Thus, it is possible to prevent an
overcurrent from flowing through the PTC heater.
Preferably, in the air conditioning device of the present invention configured
as
described above, a compressor that operates a refrigeration cycle and a heat
exchanger that exchanges heat with the air current generated by the air blower
in a
high temperature part of the refrigeration cycle are provided, and the air
conditioning
device can switch between a heating operation performed by driving of the
compressor
and a heating operation performed by driving of the PTC heater, and, when the
heating operation by driving of the compressor is performed and the
temperature
within the room is lower than a predetermined temperature, the heating
operation is
switched to the heating operation by driving of the PTC heater.
In this configuration, the compressor and the air blower are driven to perform
the heating operation, and the compressor is driven to operate the
refrigeration cycle.
The air current generated by the air blower exchanges heat with the heat
exchanger,
and the air heated by the heat exchanger is discharged into the room. In a
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predetermined period after the heating operation by driving of the compressor
is
performed, the temperature detection portion detects the temperature within
the room.
When the temperature within the room is lower than the predetermined
temperature,
the compressor is stopped and the PTC heater is driven, and the air that has
exchanged heat with the PTC heater is discharged into the room.
Preferably, in the air conditioning device of the present invention configured
as
described above, when the heating operation is started, the heating operation
by
driving of the PTC heater is performed, and, when the temperature within the
room
becomes higher than a predetermined temperature, the heating operation is
switched
to the heating operation by driving of the compressor. In this configuration,
when the
air conditioning device starts to perform the heating operation, the air that
has
exchanged heat with the PTC heater by driving of the PTC heater is discharged
into
the room. When the temperature within the room becomes higher than the
predetermined temperature, the PTC heater is stopped and the compressor is
driven,
and the air that has exchanged heat with the heat exchanger is discharged into
the
room. Then, when the temperature within the room becomes lower than the
predetermined temperature, the compressor is stopped and the PTC heater is
driven.
In the present invention, the duty ratio is set at 100% in the low temperature
range and the PTC heater is driven in the rise region; the PTC heater is
stopped in the
high temperature range; and the duty ratio is set at a predetermined duty
ratio in the
intermediate temperature range and the PTC heater is driven in the stable
region.
Thus it is possible not only to stabilize the amount of heat generated by the
PTC
heater in the low temperature range to prevent the PTC heater from being
overheated
but also to prevent an overcurrent from being produced in the intermediate
temperature range. Since the temperature of the PTC heater is not kept at a
high
temperature, it is possible to prevent the temperature near the air
conditioning device
from being increased and to make the temperature within the room uniform.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be further understood from the following detailed
description
of exemplary embodiments of the invention in conjunction with the accompanying
drawings, in which:
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FIG. 1 is a perspective view showing an air conditioning device of a first
embodiment;
FIG. 2 is a side cross-sectional view showing the air conditioning device of
the
first embodiment;
Fig. 3 is a block diagram showing the configuration of the air conditioning
device
of the first embodiment;
Fig. 4 is a diagram showing the temperature characteristic of the resistance
of
a PTC heater in the air conditioning device of the first embodiment;
Fig. 5 is a flowchart showing the operation of a heating operation of the air
conditioning device of the first embodiment;
Fig. 6 is a flowchart showing the operation of a heating operation of an air
conditioning device of a second embodiment;
Fig. 7 is a flowchart showing the operation of a heating operation of the air
conditioning device of a third embodiment;
Fig. 8 is a flowchart showing the operation of duty variation processing on
the
air conditioning device of the third embodiment;
Fig. 9 is a time chart on the duty variation processing on the air
conditioning
device of the third embodiment; and
Fig. 10 is a flowchart showing the operation of a heating operation of an air
conditioning device of a fourth embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiments of the present invention will be described below with reference
to the accompanying drawings. Figs 1 and 2 show a perspective view and a side
cross
sectional view, respectively, of an air conditioning device of a first
embodiment. Fig.
1 shows a state where an outer cover 30 (see Fig. 2) is removed. The air
conditioning
device 1 is integrally formed so as to have an indoor portion 2 that is
arranged within
a room and an outdoor portion 4 that is adjacent to the indoor portion 2 and
arranged
outside the room.
In the front surface of the indoor portion 2, an inlet port 21 is provided; in
the
front surface of the outdoor portion 4, an outdoor heat exchanger 42 is
provided. In the
following description, the side of the inlet port 21 is referred to as a front
side, and the
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side of the outdoor heat exchanger 42 is referred to as a rear side (back
surface side).
The right side and the left side as seem from a position opposite the front
surface of
the inlet port 21 are referred to as the right side and the left side of the
air conditioning
device 1.
The indoor portion 2 and the outdoor portion 4 are placed on a bottom plate 3,
and they are separated, one in front of the other, by a separation wall 5. In
the indoor
portion 2, an enclosure 20 is formed that covers the outside of the indoor
portion 2 with
the bottom plate 3, the separation wall 5 and the outer cover 30. Likewise, in
the
outdoor portion 4, an enclosure 40 is formed that covers the outside of the
outdoor
portion 4 with the bottom plate 3, the separation wall 5 and an outer cover
(not shown).
In the outdoor portion 4, a compressor 41 that operates a refrigeration cycle
is
arranged in an end portion in the right side. In the back surface of the
outdoor portion
4, the outdoor heat exchanger 42, which is connected to the compressor 41
through
a refrigerant pipe 47, is arranged. An outdoor fan 43 that is formed with a
propeller fan
is so arranged in the center portion in a right and left direction as to face
the outdoor
heat exchanger 42, and cools the outdoor heat exchanger 42. The outdoor fan 43
and
the outdoor heat exchanger 42 are arranged within a housing 44, and the
housing 44
forms a duct that guides an air current from the outdoor fan 43 to the outdoor
heat
exchanger 42. The housing 44 is supported by the separation wall 5 through
brackets
45.
The inlet port 21 is open in the front surface of the outer cover 30 covering
the
indoor portion 2; an outlet port 22 is open above the inlet port 21. Within
the indoor
portion 2, a blower duct 24 through which the inlet port 21 is coupled to the
outlet port
22 forms a blower passage 23. The blower duct 24 has, in its upper portion, a
duct
member 29 that can be freely detached when the outer cover 30 is removed; the
duct
member 29 forms a lower wall near the outlet port 22 of the blower passage 23.
Within the blower passage 23, an indoor fan 25 (air blower) formed with a
cross
flow fan is provided. In the vicinity of the outlet port 22 within the blower
passage 23,
a louver 26 is provided that can change the direction of an air current. An
indoor heat
exchanger 27 that is connected to the compressor 41 through the refrigerant
pipe 47
is arranged between the indoor fan 25 and the inlet port 21.
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A heating portion 28 that has a plurality of PTC heaters 55 (see Fig. 3) is
arranged between the indoor fan 25 and the indoor heat exchanger 27. The
indoor fan
25 forms, in the blower passage 23, an air current that is passed through the
inlet port
21 and that exchanges heat with the PTC heaters 55 and the indoor heat
exchanger
27. The duct member 29 covers the top of the indoor heat exchanger 27 and the
heating portion 28. When the duct member 29 is removed, the heating portion 28
can
be freely detached.
Fig. 3 is a block diagram showing the configuration of the air conditioning
device. The air conditioning device 1 includes a control portion 50 that
controls
portions of the air conditioning device 1. The compressor 41, the indoor fan
25, the
outdoor fan 43, an operation portion 51, a storage portion 52, a current
detection
portion 53, a heater control portion 54 and a temperature detection portion 56
are
connected to the control portion 50. The PTC heaters 55 of the heating portion
28 are
connected to the heater control portion 54.
The operation portion 51 is formed with an operation button and a remote
controller provided on the surface of the enclosure 20; through the operation
portion
51, an instruction to operate the air conditioning device 1 is provided and a
setting is
input. The storage portion 52 is formed with a ROM and a RAM; the storage
portion
52 stores a program for operating the air conditioning device 1 and setting
conditions
and the like, and performs temporary storage during the computation of the
control
portion 50. Although the storage portion 52 is connected to the outside of the
control
portion 50, the storage portion 52 may be provided within the control portion
50.
The current detection portion 53 detects a current flowing through the PTC
heaters. The heater control portion 54 controls the driving of the PTC heaters
55. The
temperature detection portion 56 detects the temperature within the room. The
heater
control portion 54 is formed with a triac circuit or a relay circuit, and
controls the duty
ratio of the PTC heaters 55. The heater control portion 54 is preferably
formed with the
tiac circuit because this makes it possible to reduce a sound resulting from
switching
as compared with the relay circuit.
The PTC heater 55 is formed by sandwiching a heating element having a PTC
characteristic between electrodes; a drive voltage is applied, by the heater
control
portion 54, across the electrodes, and thus heat is produced. Fig. 4 shows the
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temperature characteristic of the resistance of the PT'C heater 55. The
vertical axis
represents the resistance; the horizontal axis represents the temperature. In
a stable
region SI, when the temperature of the PTC heater 55 is increased, the
resistance is
decreased or is substantially constant whereas, in a rise region S2, the
resistance is
rapidly increased when the temperature exceeds a rise temperature T1.
In the air conditioning device 1 configured as described above, when a cooling
operation is started, the compressor 41 is driven and thus the refrigeration
cycle is
operated. Thus, the indoor heat exchanger 27 functions as an evaporator on the
low
temperature side of the refrigeration cycle, and the outdoor heat exchanger 42
functions as a condenser on the high temperature side of the refrigeration
cycle. The
outdoor heat exchanger 42 is cooled by the outdoor fan 43 to discharge heat.
The air
within the room flows, by driving of the indoor fan 25, through the inlet port
21 into the
blower passage 23; the air whose temperature is decreased by exchanging heat
with
the indoor heat exchanger 27 is discharged through the outlet port 22 into the
room.
In this way, the room is cooled.
The air conditioning device 1 can switch between a heating operation performed
by driving of the compressor 41 and a heating operation performed by driving
of the
PTC heaters 55, and thereby perform the heating operation. When the compressor
41
is driven, the refrigeration cycle is operated. Thus, the indoor heat
exchanger 27
functions as a condenser on the high temperature side of the refrigeration
cycle, and
the outdoor heat exchanger 42 functions as an evaporator on the low
temperature side
of the refrigeration cycle. The outdoor heat exchanger 42 exchanges heat with
outside
air by the outdoor fan 43, and absorbs heat. The air within the room flows, by
driving
of the indoor fan 25, through the inlet port 21 into the blower passage 23,
and the air
is increased in temperature by exchanging heat with the indoor heat exchanger
27.
The air heated by the indoor heat exchanger 27 is discharged through the
outlet port
22 into the room.
When the PTC heaters 55 are driven, the air within the blower passage 23 is
increased in temperature by the PTC heaters 55. The air heated by the PTC
heaters
55 is discharged through the outlet port 22 into the room.
Although the heating operation performed by driving of the compressor 41 can
reduce power consumption as compared with the heating operation performed by
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driving of the PTC heaters 55, since the outdoor heat exchanger 42 does not
sufficiently absorb heat when the temperature of the outside air is low, the
heating
ability is reduced. Hence, when the temperature of the outside air is high,
the heating
operation by driving of the compressor 41 is performed whereas when the
temperature
of the outside air is low, the heating operation by driving of the PTC heaters
55 is
performed.
Fig. 5 is a flowchart showing the operation of the heating operation performed
by driving of the PTC heaters 55. A different type of control is performed on
the PTC
heaters 55 and the indoor fan 25 in each of a low temperature range, an
intermediate
temperature range and a high temperature range into which the temperature
within the
room is divided. The low temperature range is formed with a predetermined
temperature range including a region whose temperatures are lower than the set
temperature for the temperature within the room. The high temperature range is
formed with a predetermined temperature range whose temperatures are higher
than
the set temperature for the temperature within the room. The intermediate
temperature
range is formed with a temperature range between the low temperature range and
the
high temperature range.
For example, a boundary temperature between the low temperature range and
the intermediate temperature range is set at the set temperature for the
temperature
within the room, and a boundary temperature between the intermediate
temperature
range and the high temperature range is set at a temperature that is 2 C
higher than
the set temperature for the temperature within the room. Consequently, the low
temperature range is a temperature range that is equal to or less than the set
temperature, the intermediate temperature range is a temperature range that
ranges
from the set temperature to the set temperature +2 C and the high temperature
range
is a temperature range that is equal to or more than the set temperature +2 C.
The
boundary temperature between the low temperature range and the intermediate
temperature range may be set higher than the set temperature for the
temperature
within the room. The boundary temperature when the temperature is decreased
may
be reduced by a predetermined temperature (for example, 1 C) from the boundary
temperature when the temperature is increased. Thus, it is possible to
stabilize the
operation of the PTC heaters 55 around the boundary temperature.
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In step #21, the temperature within the room is detected by the temperature
detection portion 56. In step #22, whether or not the temperature within the
room is
within the low temperature range is determined. If the temperature within the
room is
within the low temperature range, in step #23, the duty ratio of the PTC
heaters 55 is
set at 100%, and the PTC heaters 55 are driven. In step #36, the indoor fan 25
is
driven to produce a strong air current (for example, 1140 RPM), and the
process
returns to step #21.
Here, the temperature of the PTC heaters 55 is kept at the temperature in the
rise region S2 (see Fig. 4). Thus, when the temperature of the PTC heaters 55
are
increased, the resistance of the heating elements is rapidly increased, and
the current
and the amount of heat generated are decreased whereas, when the temperature
is
decreased, the resistance of the heating elements is rapidly decreased, and
the
current and the amount of heat generated are increased. Hence, the amount of
heat
generated by the PTC heaters 55 becomes constant, and thus it is possible not
only
to easily produce warm air having a predetermined temperature but also to
prevent the
PTC heaters 55 from being overheated.
If, in step #22, the temperature within the room is determined not to be
within
the low temperature range, the process moves to step #31. In step #31, whether
or not
the temperature within the room is within the intermediate temperature range
is
determined. If the temperature within the room is within the intermediate
temperature
range, in step #35, the duty ratio of the PTC heaters 55 is set at 40%, and
the PTC
heaters 55 are driven. In step #36, the indoor fan 25 is driven to produce a
strong air
current, and the process returns to step #21.
Here, the temperature of the PTC heaters 55 is kept at the temperature in the
stable region S1 (see Fig. 4), and the amount of heat generated by the PTC
heaters
55 is reduced. Since the duty ratio is reduced such that the temperature in
the stable
region S1 is reached, the resistance of the PTC heaters 55 is decreased but
the
current is reduced. Thus, an overcurrent is prevented from flowing through the
PTC
heaters 55.
lf, in step #31, the temperature within the room is determined not to be
within
the intermediate temperature range, the temperature within the room is within
the high
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temperature range, and hence the process moves to step #41. In step #41, the
PTC
heaters 55 are stopped (duty ratio of 0%). In step #42, the indoor fan 25 is
driven to
produce a soft air current (for example, 300 RPM), and the process returns to
step
#21. Thus, the discharge of cold air resulting from the temperature of the PTC
heaters
55 being reduced is prevented.
In step #42, the indoor fan 25 may be stopped. Here, it is preferable to stop
the
indoor fan 25 a predetermined period of time (for example, 30 seconds) after
the PTC
heaters 55 are stopped because heat is not left within the indoor portion 2.
In the present embodiment, the duty ratio is set at 100% in the low
temperature
range and the PTC heaters 55 are driven in the rise region S2; the PTC heaters
55 are
stopped in the high temperature range; and the duty ratio is set at a
predetermined
duty ratio in the intermediate temperature range and the PTC heaters 55 are
driven
in the stable region S1. Thus it is possible not only to stabilize the amount
of heat
generated by the PTC heaters 55 in the low temperature range to prevent the
PTC
heaters 55 from being overheated but also to prevent an overcurrent from being
produced in the intermediate temperature range. Since the temperature of the
PTC
heaters 55 is not kept at a high temperature, it is possible to prevent the
temperature
near the indoor portion 2 of the air conditioning device 1 from being
increased and to
make the temperature within the room uniform.
Hence, the compressor 41 is stopped, the PTC heaters 55 are only driven and
thus the heating operation can be performed. Therefore, the ability of the PTC
heaters
55 is fully used, and thus it is possible to prevent the heating ability from
being
reduced such as when the temperature of outside air is low.
Since the number of revolutions of the indoor fan 25 (air blower) is reduced
in
the high temperature range as compared with the low temperature range, it is
possible
to prevent cold air from being discharged due to the stop of the PTC heaters
55 and
to prevent an uncomfortable feeling from being given to the user.
Fig. 6 is a flowchart showing the operation of a heating operation performed
by
driving of the PTC heaters 55 of an air conditioning device 1 according to a
second
embodiment. The configuration of the air conditioning device 1 of the present
embodiment is the same as described in the first embodiment shown in Figs. 1
to 5
described previously except that a control method used when the temperature
within
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the room is within the intermediate temperature range is different. In the
present
embodiment, the intermediate temperature range obtained by diving the
temperature
within the room is further divided into two auxiliary temperature ranges, and
different
types of control are performed on the PTC heaters 55 and the indoor fan 25. In
the
figure, since steps #21 to #23 and step #41 are the same as shown in Fig. 5
described
previously, their description will not be repeated.
lf, in step #31, the temperature within the room is determined to be within
the
intermediate temperature range, the process moves to step #32. In step #32,
whether
or not the temperature within the room is within a low temperature-side
auxiliary
temperature range is determined. If the temperature within the room is within
the low
temperature-side auxiliary temperature range, in step #35, the duty ratio of
the PTC
heaters 55 is set at 40%, and the PTC heaters 55 are driven. In step #36, the
indoor
fan 25 is driven to produce a strong air current, and the process returns to
steR#21. .
lf, in step #32, the temperature within the room is determined not to be
within
the low temperature-side auxiliary temperature range, the temperature within
the room
is within a high temperature-side auxiliary temperature range, and the process
moves
to step #37. In step #37, the duty ratio of the PTC heaters 55 is set at 30%,
and the
PTC heaters 55 are driven. In step #42, the indoor fan 25 is driven to produce
a soft
air current, and the process returns to step #21.
In the present embodiment, the intermediate temperature range is further
divided into a plurality of auxiliary temperature ranges, the duty ratio in
the high
temperature-side auxiliary temperature range is set at 30% that is lower than
that in
the low temperature-side auxiliary temperature range and the PTC heaters 55
are
driven. Thus, it is possible to more finely adjust the amount of heat supplied
to the
room according to the temperature within the room and to more stably maintain
the
temperature within the room.
Since the number of revolutions of the indoor fan 25 (air blower) is reduced
in
the high temperature-side auxiliary temperature range as compared with the low
temperature-side auxiliary temperature range, it is possible to prevent cold
air from
being discharged due to a decrease in the temperature of the PTC heaters 55
and to
prevent an uncomfortable feeling from being given to the user. When the duty
ratio is
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set at 30% but the temperature within the room is increased, in step #41, the
PTC
heaters 55 are stopped. Here, the indoor fan 25 may be stopped.
Although, in the present embodiment, the intermediate temperature range is
divided into the two auxiliary temperature ranges, the intermediate
temperature range
may be divided into three or more auxiliary temperature ranges, and the PTC
heaters
55 may be driven at different duty ratios.
Fig. 7 is a flowchart showing the operation of a heating operation performed
by
driving of the PTC heaters 55 of an air conditioning device 1 according to a
third
embodiment. The air conditioning device 1 of the present embodiment is
operated in
the same manner as in the second embodiment shown in Fig. 6 described
previously
except that a control method used when the temperature within the room is
within the
low temperature range is different. In the figure, since steps #21 and #22 and
steps
#31 to #42 are the same as shown in Fig. 6 described previously, their
description will
not be repeated.
lf, in step #22, the temperature within the room is determined to be within
the
low temperature range, the process moves to step #25 where duty variation
processing shown in Fig. 8 is performed. Fig. 9 is a time chart when the duty
variation
processing is performed. Fig. 9(a) shows a duty ratio (unit: %) of a drive
voltage of the
PTC heaters 55. Fig. 9(b) shows a current (represented by "I" in the figure)
detected
by the current detection portion 53 and the temperature (represented by "T" in
the
figure) of the PTC heaters 55.
In step #51, in the early stage of the duty variation processing, the indoor
fan
is driven at the first number of revolutions (for example, 600 RPM) to produce
a soft
air current. In step #52, the PTC heaters 55 start being driven at a duty
ratio of 50%
25
that is higher than that in the intermediate temperature range (time t0).
Thus, the
temperature of the PTC heaters 55 is increased, and the current flowing
through the
PTC heaters 55 is increased until the temperature of the heating elements
reaches the
rise temperature T1 (see Fig. 4).
The heater control portion 54 acquires a result of detection by the current
detection portion 53 at intervals of a predetermined period (one second in the
present
embodiment); in step #53, the heater control portion 54 is placed on standby
until the
predetermined period elapses. After the predetermined period elapses, in step
#54,
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the current detected by the current detection portion 53 is acquired. In step
#55,
whether or not the current acquired from the current detection portion 53 is
higher than
a predetermined current value 11 is determined. The current value 11 is set
based on
a power supply capacity; when the current exceeds the current value 11, an
overcurrent state where a large amount of current flows through the PTC
heaters 55
and the power supply capacity may be exceeded is produced.
If the predetermined period that is the interval for the acquisition of the
result
of the detection by the current detection portion 53 in step #53 is too short,
a burden
is placed on the control. On the other hand, if the predetermined period is
too long,
during standby, the current flowing through the PTC heaters 55 may be
excessively
increased or may be excessively decreased. Hence, in the present embodiment,
the
predetermined period is set at one second. It is preferable to determine an
appropriate
period by experiment according to the configuration of the air conditioning
device 1.
If the current acquired from the current detection portion 53 is higher than
the
current value 11 in step #56, the duty ratio of the PTC heaters 55 is reduced
only by
10% (which indicates 10% with respect to 100%). Thus, it is possible to come
out of
the overcurrent state, and the process returns to step #53.
If the current acquired from the current detection portion 53 is not higher
than
the current value 11, in step #57, whether or not the current is lower than a
predetermined current value 12 is determined. The current value 12 is set
lower than
the current value 11 If the current acquired from the current detection
portion 53 is
lower than the predetermined current value 12, the process moves to step #58.
When the temperature of the PTC heaters 55 is increased and the temperature
of the heating elements exceeds the rise temperature T1, the resistance of the
heating
elements is increased, and the current through the PTC heaters 55 reaches a
local
maximum value P (see Fig. 9(b)). Hence, if the current acquired from the
current
detection portion 53 becomes lower than the current value acquired in the
preceding
round, the current is determined to reach the local maximum value P, and the
process
moves to step #59. If the current acquired from the current detection portion
53 is not
lower than the current value acquired in the preceding round, the process
returns to
step #53.
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In step #59, the duty ratio of the PTC heaters 55 is increased only by 10%
(which indicates 10% with respect to 100%). Since the duty ratio is increased,
the
current through the PTC heaters 55 is increased again. The duty ratio of the
PTC
heaters 55 may be increased by a value other than 10%.
In step #60, whether or not the duty ratio of the PTC heaters 55 reaches 100%
is determined. If the duty ratio of the PTC heaters 55 does not reach 100%,
the
process returns to step #53, and steps #53 to #60 are repeated. Then, as
described
above, when the temperature of the PTC heaters 55 is increased, the resistance
is
increased, and the current through the PTC heaters 55 reaches the local
maximum
value P. In this way, the duty ratio of the PTC heaters 55 is increased by 10%
each
time the process comes to step #59, and the current is gradually increased.
If the duty ratio of the PTC heaters 55 reaches 100%, the process returns to
the
flowchart of Fig. 7. In step #36 of Fig. 7, the indoor fan 25 is driven at a
second
number of revolutions (for example, 1140 RPM) larger than the first number of
revolutions so as to produce a strong air current. Here, the amount of cooling
by the
PTC heaters 55 is increased, and the temperature T of the PTC heaters 55 is
slightly
reduced.
lf, in step #57, the current acquired from the current detection portion 53 is
determined not to be lower than the current value 12, the process returns to
step #53.
In other words, the duty ratio of the PTC heaters 55 is maintained regardless
of the
occurrence of the local maximum value P. Hence, the duty ratio is neither
increased
nor decreased between the current value 11 and the current value 12, and thus
it is
possible to prevent the overcurrent state from being produced.
In the present embodiment, in the early stage after the movement to the low
temperature range, driving is performed at a duty ratio higher than the duty
ratio in the
intermediate temperature range; and, when the current through the PTC heaters
55
is lower than the predetermined current value 12, the duty ratio is increased
only by the
predetermined amount, and this is repeated until the duty ratio reaches 100%.
Hence,
even when the temperature of the PTC heaters 55 is low, such as when the PTC
heaters 55 are started, the current is gradually increased, and thus it is
possible to
prevent an overcurrent from being produced and to prevent the current from
exceeding
the power supply capacity.
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Since, when the current through the PTC heaters 55 reaches the local
maximum value P, the duty ratio is increased, the timing of increasing the
duty ratio
is prevented from being early, and thus it is possible to reliably prevent an
overcurrent
from being produced such as when the PTC heaters 55 are started.
In the early stage of the duty variation processing, the indoor fan 25 is
driven
at the first number of revolutions (for example, 600 RPM), and, when the duty
ratio of
the PTC heaters 55 reaches 100%, the indoor fan 25 is driven at the second
number
of revolutions (for example, 1140 RPM), which is larger than the first number
of
revolutions. The volume of air blown by the indoor fan 25 is reduced in the
early stage,
and thus the exchange of heat between the PTC heaters 55 and the air is
facilitated.
It is therefore possible to increase the rate at which the temperature of the
PTC
heaters 55 is increased.
Since, if the current acquired from the current detection portion 53 is higher
than the current value 11, in step #56, the duty ratio is reduced, it is
possible to come
out of the overcurrent state of the PTC heaters 55 and to more reliably
prevent the
current from exceeding the power supply capacity.
Fig. 10 is a flowchart showing the operation of a heating operation performed
by an air conditioning device 1 according to a fourth embodiment. The air
conditioning
device 1 of the present embodiment can switch between the heating operation
performed by driving of the compressor 41 and the heating operation performed
by
driving of the PTC heaters 55. The heating operation by driving of the PTC
heaters 55
is performed in the same manner as described in the third embodiment of Figs.
7 to
9 described previously; since the steps #21 to #42 are the same as shown in
Fig. 7,
and their description will not be repeated.
When the heating operation is started, in step #11, the indoor fan 25 is
driven
to produce a strong air current. In step #12, the temperature within the room
is
detected by the temperature detection portion 56. In step #13, whether or not
the
temperature within the room is within the high temperature range is
determined. If the
temperature within the room is not within the high temperature range, in step
#14, the
duty ratio of the PTC heaters 55 is set at 100%, and the PTC heaters 55 are
driven.
In this way, the heating operation by driving of the PTC heaters 55 is
performed. Then,
the process returns to step #11, and steps #11 to #14 are repeated.
If the temperature within the room enters the high temperature range, the
process moves to step #15 where the PTC heaters 55 are stopped. In step #16,
the
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compressor 41 is driven. Thus, the heating operation by driving of the
compressor 41
is performed. In step #17, the temperature within the room is detected by the
temperature detection portion 56. In step #18, whether or not the temperature
within
the room is within the low temperature range is determined.
If the temperature within the room is not within the low temperature range,
steps
#17 and #18 are repeated. The ability of the compressor 41 is changed
according to
the temperature within the room, and the compressor 41 is driven such that the
temperature within the room is kept near the set temperature. Here, since the
temperature within the room changes near the set temperature, in order to
prevent the
temperature within the room from often entering the low temperature range, the
boundary temperature between the low temperature range and the intermediate
temperature range is set such that the boundary temperature is reduced by a
predetermined temperature (for example, 1 C) from the set temperature for the
temperature within the room.
If the temperature within the room enters the low temperature range, in step
#19, the compressor 41 is stopped. Then, in steps #21 to #42, the operation is
switched to the heating operation performed by driving of the PTC heaters 55.
If the
temperature within the room enters the high temperature range while the PTC
heaters
55 are being driven, the process moves to step #15 by the determination made
in step
#31. Thus, the PTC heaters 55 are stopped, and the operation is switched to
the
heating operation performed by driving of the compressor 41.
In the present embodiment, since, when the temperature within the room is
lower than the predetermined temperature, the heating operation performed by
driving
of the compressor 41 is switched to the heating operation performed by driving
of the
PTC heaters 55, it is possible to reduce the power consumption by performing
the
heating operation by driving of the compressor 41 near the set temperature.
When the
temperature within the room cannot be kept near the set temperature by driving
of the
compressor 41, the PTC heaters 55 are driven, and thus it is possible to keep
the
temperature at the set temperature.
When the heating operation is started, the heating operation by driving of the
PTC heaters 55 is performed, and, when the temperature within the room becomes
higher than the predetermined temperature, the operation is switched to the
heating
operation performed by driving of the compressor 41. Therefore, the PTC
heaters 55
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are driven at a low temperature when the air conditioning device 1 is started,
and thus
it is possible to rapidly increase the temperature within the room.
The present invention can be applied to air conditioning devices having PTC
heaters.
List of Reference Numerals
1 AIR CONDITIONING DEVICE
2 INDOOR PORTION
3 BOTTOM PLATE
4 OUTDOOR PORTION
5 SEPARATION WALL
ENCLOSURE
21 INLET PORT
22 OUTLET PORT
15 23 BLOWER PASSAGE
24 BLOWER DUCT
INDOOR FAN
26 LOUVER
27 INDOOR HEAT EXCHANGER
20 28 HEATING PORTION
OUTER COVER
41 COMPRESSOR
42 OUTDOOR HEAT EXCHANGER
43 OUTDOOR FAN
25 47 REFRIGERANT PIPE
50 CONTROL PORTION
51 OPERATION PORTION
52 STORAGE PORTION
53 CURRENT DETECTION PORTION
30 54 HEATER CONTROL PORTION
55 PTC HEATER
56 TEMPERATURE DETECTION PORTION
