Abstrict
An air conditioning apparatus for heating a cabin of an electric
car having reduced electric power consumption is disclosed. An initial
setting of the heating operation is that of using a refrigerating
cycle 17. An average value of actual electric power consumption
using the refrigerating cycle for a predetermined period is calculated.
Furthermore, electric power consumption using an electric heater
20 is calculated for obtaining the same heating capacity as that
obtained by the refrigerating cycle. A switching of the heating
operation from the refrigerating cycle to the electric heater 20
takes place when it is determined that electric power consumption
using the electric heater is less than that using the refrigerating
cycle 17.
Claims
We claim:
1. An air conditioning apparatus for controlling a temperature
of a cabin, comprising:
(a) a duct defining therein an air passageway to said cabin;
(b) a fan device for creating a forced air flow in said passageway
toward the cabin;
(c) a refrigerating cycle comprising a compressor for obtaining
a high pressure gaseous refrigerant, and an inner heat exchanger
that receives the gaseous refrigerant from the compressor, said
inner heat exchanger being arranged in the duct so that a heat exchange
between the air in the duct and the refrigerant in the inner heat
exchanger takes place to heat the air directed to the cabin;
(d) an electric motor for imparting a rotational movement to the
compressor to recirculate the refrigerant along the refrigerating
cycle;
(e) an electric heater arranged in the duct for generating electric
heat for directly heating the air flow directed to the cabin;
(f) means for determining electrical power consumption of the refrigerating
cycle and for determining electrical power consumption of the electric
heater; and
(g) control means for selecting the one of the refrigerating cycle
and the electric heater that consumes less electric power when obtaining
a desired heating capacity at the cabin.
2. An air conditioning apparatus according to claim 1, further
comprising means for detecting a degree of the heating as required,
and means for operating both the refrigerating cycle and the electric
heater when the heating requirement is larger than a predetermined
value.
3. An air conditioning apparatus for controlling a temperature
of a cabin, comprising:
(a) a duct defining therein an air passageway to said cabin;
(b) a fan device for creating a forced air flow in said passageway
toward the cabin;
(c) a refrigerating cycle comprising a compressor for obtaining
a high pressure gaseous refrigerant, and an inner heat exchanger
that receives the gaseous refrigerant from the compressor, said
inner heat exchanger being arranged in the duct so that a heat exchange
between the air in the duct and the refrigerant in the inner heat
exchanger takes place to heat the air directed to the cabin;
(d) an electric motor for imparting a rotational movement to the
compressor to recirculate the refrigerant along the refrigerating
cycle:
(e) an electric heater arranged in the duct for generating electric
heat for directly heating the air flow directed to the cabin; and
(f) control means for selecting the one of the refrigerating cycle
and the electric heater that consumes less electric power when obtaining
a desired chamber heating capacity; wherein said control means includes
means for obtaining a value of electric power consumption when
using the refrigerating cycle for heating the cabin,
means for obtaining a value of electric power consumption when
using the electric heater for obtaining the same heating capacity
as that obtained by the refrigerating cycle,
means for comparing the value of electric power consumption when
using the refrigerating cycle with the value of electric power consumption
when using the electric heater, and
means for selecting one of said refrigerating cycle and said electric
heater that provides a smaller value of electric power consumption.
4. An air conditioning apparatus according to claim 3, wherein
said means for obtaining a value of electric power consumption when
using the refrigerating cycle comprises means for detecting operating
parameters of the air conditioning apparatus, and means, based on
the detected operating parameters, for calculating electric power
consumption when during the heating operation using the refrigerating
cycle.
5. An air conditioning apparatus for controlling a temperature
of a cabin, comprising:
(a) a duct defining therein an air passageway to said cabin;
(b) a fan device for creating a forced air flow in said passageway
toward the cabin;
(c) a refrigerating cycle comprising a compressor for obtaining
a high pressure gaseous refrigerant, and an inner heat exchanger
that, receives the gaseous refrigerant from the compressor, said
inner heat exchanger being arranged in the duct so that a heat exchange
between the air in the duct and the refrigerant in the inner heat
exchanger takes place to heat the air directed to the cabin;
(d) an electric motor for imparting a rotational movement to the
compressor to recirculate the refrigerant along the refrigerating
cycle;
(e) an electric heater arranged in the duct for generating electric
heat for directly heating the air flow directed to the cabin; and
(f) control means for selecting the one of the refrigerating cycle
and the electric heater that consumes less electric power when obtaining
a desired chamber heating capacity; wherein said control means includes
means for obtaining a value of electric power consumption when
using the refrigerating cycle for heating the cabin comprising means
for operating the refrigerating cycle for a predetermined period,
and means for measuring actual electric power consumption using
the refrigerating cycle when obtaining a required level of heating,
means for obtaining a value of electric power consumption when
using the electric heater for obtaining the same heating capacity
as that obtained by the refrigerating cycle,
means for comparing the value of electric power consumption when
using the refrigerating cycle with the value of electric power consumption
when using the electric heater, and
means for selecting one of said refrigerating cycle and said electric
heater that provides a smaller value of electric power consumption.
6. An air conditioning apparatus for an electric car cabin, comprising:
(a) a duct defining therein an air passageway that has at its first
end an inlet for inside air and an inlet for outside air, and, at
its second end an outlet for discharging air to the cabin;
(b) a switching means for switching between a position where the
inside inlet is connected to the air passageway and a second position
where the outside inlet is connected to the passageway;
(c) a fan device for creating a forced air flow in said passageway
toward the cabin;
(d) a refrigerating cycle comprising a compressor for obtaining
a high pressure gaseous refrigerant, and an inlet heat exchanger
that receives the gaseous refrigerant from the compressor, said
inner heat exchanger being arranged in the duct so that a heat exchange
between the air in the duct and the refrigerant in the inner heat
exchanger takes place for heating the air directed to the cabin;
(e) an electric motor for imparting a rotational movement to the
compressor so that a recirculation of the refrigerant along the
refrigerating cycle is obtained;
(f) an electric heater arranged in the duct for generating electric
heat for directly heating the air flow directed to the cabin; and
(g) control means for selecting one of the refrigerating cycle
and the electric heater that consumes less electric power when obtaining
a desired heating capacity at the cabin by comparing the electric
power consumption when using the refrigerating cycle with the electric
power consumption when using the electric heater.
Description BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an air conditioning apparatus
capable of conducting a heating operation using a refrigerating
cycle which is suitable, in particular, for an electric car.
2. Description of Related Art
A technique for heating air using a refrigerant compressor operated
by an electric motor is known in the art. In this technique, the
compressor is located in a refrigerating circuit which, in addition
to the compressor, includes an inside heat exchanger as a condenser
connected to the compressor for receiving a high temperature refrigerant,
a pressure reduction device for reducing a pressure of the refrigerant
from the inner heat exchanger, and an outside heat exchanger acting
as an evaporator for receiving the pressure reduced refrigerant
from the pressure reduction device and for returning the refrigerant
to the compressor. The inner heat exchanger acting as a condenser
is located in an air duct in which an air flow is created and discharged
to the interior of the vehicle. At the inner heat exchanger, a heat
exchange takes place between the air in the duct and the high temperature
refrigerant, so that the air is heated while the refrigerant is
cooled, thereby causing the refrigerant to condense. At the outside
heat exchanger acting as an evaporator, a heat exchange takes place
between the outside air and the refrigerant, so that heat is taken
from the outside air while the refrigerant is heated, thereby causing
the refrigerant to evaporate.
In such an air conditioning apparatus where the heating operation
is carried out by the refrigerating cycle, a reduction in heating
efficiency is inevitable when the temperature of the outside air
is low, because the outside air is deprived of heat. Thus, a reduction
in the outside air temperature will increase the work done by the
compressor in maintaining a desired level of heating performance,
which increases the electric power consumption of the motor. Furthermore,
the increased work load of the compressor will increase the pressure
of the refrigerant at the outlet of the compressor, thereby increasing
the load of the compressor, which also increases the electric power
consumption of the motor.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an air conditioning
apparatus using a refrigerant cycle for a heating operation that
is capable of operating with a reduced electric power consumption.
According to the present invention, an air conditioning apparatus
for controlling a temperature of a chamber is provided and comprises:
(a) a duct defining therein an air passageway to said chamber;
(b) a fan device for creating a forced air flow in said passageway
toward the chamber;
(c) a refrigerating cycle comprising a compressor for obtaining
a high pressure gaseous refrigerant, and an inner heat exchanger
that receives the gaseous refrigerant from the compressor;
(d) said inner heat exchanger being arranged in the duct such that
a heat exchange of the air in the duct with the refrigerant in the
inner heat exchanger takes place for heating the air directed to
the chamber;
(e) an electric motor for imparting a rotational movement to the
compressor such that a recirculation of the refrigerant in the refrigerating
cycle is obtained;
(f) an electric heater arranged in the duct for generating electric
heat so as to directly heat the air flow directed to the chamber
and,
(g) control means for selecting the system between the refrigerating
cycle and the electric heater that consumes less electric power
for obtaining a desired chamber heating capacity.
BRIEF EXPLANATION OF ATTACHED DRAWINGS
FIG. 1 is a schematic view of an air conditioning apparatus according
to the present invention when used in an electric car.
FIG. 2 shows refrigerating cycle in the air conditioning apparatus
in FIG. 1 together with an air duct for air conditioning the vehicle.
FIG. 3 schematically shows an arrangement of a control panel of
the air conditioning apparatus in the interior of a vehicle.
FIGS. 4 and 5 are flow charts generally illustrating the air conditioning
apparatus in the first embodiment.
FIG. 6 is a flow chart for executing a heating operation in a second
embodiment.
FIGS. 7 and 8 are routines for obtaining estimated values of electric
power consumption during the heating operation using a refrigerating
cycle and an electric heater, respectively, in the second embodiment.
FIG. 9 shows another embodiment of the invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
In FIG. 1, which schematically shows an air conditioning apparatus
for an electric car, reference numeral 1 generally illustrates an
air conditioning apparatus. The air conditioning apparatus 1 includes
a duct 2 defining therein a passageway for an air flow, which has
at its inlet end a switching device 3 for switching an air inlet
between a position for the introduction of inside air and a position
for the introduction of outside air, and a blower device 4 for generating
an air flow in the duct 2. An electric motor 10 is provided for
imparting a rotational movement to the fan. The duct 2 has, at its
first end, an inside air inlet 5 opened to the interior for the
introduction of inside air in the interior after being subjected
to a heat exchange, and an outside air inlet 6 for the introduction
of outside air, and, at its second end, upper outlets 11 for discharging
air flows (mainly cooled air) directed to an upper part (head) of
a passenger, lower outlets 12 for discharging air flows (mainly
hot air) directed to a lower part (legs) of the passenger, and a
defroster outlet 13 for discharging air flows (mainly hot air) directed
to the windshield (not shown) of a vehicle. Dampers 14 control the
flow of air from the upper outlets 11, a damper 15 controls the
flows of air from the lower outlet 12, and a damper 16 controls
the flows of air from the defroster outlet 13.
The switching device 3 includes a damper 7 that is moved between
an outside air introduction position 7A, as shown by a solid line,
where the inside air inlet 5 is closed and the outside air inlet
6 is opened, and an inside air introduction position 7B, as shown
by a dotted line, where the inside air inlet 5 is opened and the
outside air inlet 6 is closed.
The blower device 4 includes a fan case 8, a fan 9 having an axial
inlet and spaced radial outlets, and an electric motor 10 connected
to the fan 9 for rotating the fan 9, thereby causing the inside
air or outside air to be introduced into the duct 2.
Arranged in the duct 2 at a position downstream from the fan 9
is an upstream heat exchanger 18, purely for heating purposes, such
that a heat exchange is obtained between all of the air flow in
the duct 2 and a low temperature refrigerant in the heat exchanger
18 for cooling the air. Arranged in the duct 2 at a position downstream
from the upstream heat exchanger 18, purely for cooling purposes,
is a downstream heat exchanger 19 such that a heat exchange is obtained
between all of the air flow in the duct 2 and a high temperature
refrigerant in the heat exchanger 18 for heating the air. An auxiliary
heater 20 is made as an electric heating element, such as a positive
temperature coefficient (PTC) element for generating an amount of
heat that varies in accordance with an electric current applied
thereto.
In FIG. 2, a reference numeral 17 is a refrigerant cycle, which
includes, in addition to the upstream and downstream heat exchangers
18 and 19, an outside heat exchanger 21, a compressor 22, a first
pressure reduction device 23, a second pressure reduction device
24, an accumulator 25, and a four port two position flow direction
switching valve 27. The outside heat exchanger 21 is for obtaining
a heat exchange between the air outside the duct 2 and the refrigerant.
An outside air fan 26 is arranged so as to face the outside heat
exchanger 21 for obtaining a forced flow of outside air. The outside
air flow fan 26 has an electric motor 26-1 for imparting a rotational
movement to the fan 26.
The refrigerant compressor 22 has an inlet 22-1 for receiving a
gaseous state refrigerant from the accumulator 25 and an outlet
22-2 for issuing the refrigerant under high pressure. The compressor
22 has an electric motor 22A for imparting a rotational movement
to the compressor section. The compressor 22 and the electric motor
22A are arranged in a casing so that they are hermetically sealed.
As will be described later, an inverter 42 is provided for obtaining
a varied rotational movement speed from the electric motor 22A so
that the amount of gaseous refrigerant issued from the outlet 22-2
of the compressor 22 varies continuously. Such a change in the refrigerant
from the compressor 22 can control the temperature of the air issued
from the duct 2 to the vehicle interior.
The first pressure reduction device 23 is constructed as a capillary
tube for reducing the pressure of the refrigerant introduced into
the upstream heat exchanger 18 from the outside heat exchanger 21.
The second pressure reduction device 24 is also constructed as a
capillary tube for reducing the pressure of the refrigerant introduced
into the outside heat exchanger 21 from the downstream heat exchanger
19.
The accumulator 25 is constructed by a series of containers 25-1
and 25-2 for storing excess liquid refrigerant and for separating
gaseous refrigerant that is introduced into the inlet 22-1 of the
compressor 22.
The switching valve 27 has a first port 27-1 connected to the outlet
22-2 of the compressor 22, a second port 27-2 connected to the outside
heat exchanger 21 via a check valve 30a, a third port 27-3 connected
to the downstream heat exchanger 19, and a fourth port 27-4 connected
to the accumulator 25. The switching valve 27 is moved between a
first position (solid line) where the first and second ports 27-1
and 27-2 are connected and third and fourth ports 27-3 and 27-4
are connected, and a second portion (dotted line) where the first
and third ports 27-1 and 27-3 are connected and the second and fourth
ports 27-2 and 27-4 are connected.
A by-pass passageway 28-1 is connected to the refrigerant circuit
17 to by-pass the first pressure reduction device 23 and the upstream
heat exchanger 18, which are connected in series. A normally closed
first electromagnetic valve 28 is arranged on the by-pass passageway
28-1, and is energized during a heating operation for by-passing
the first pressure reduction device 23 and the upstream heat exchanger
18, as shown by an arrow H. A by-pass passageway 29-1 is connected
to the refrigerant circuit 17 so as to by-pass the second pressure
reduction device 24. A normally closed second electromagnetic valve
29 is arranged on the by-pass passageway 29-1, and is energized
during a dehumidifying operation for by-passing the second pressure
reduction device 24, as shown by an arrow D. A check valve 30b is
arranged between the point where the second pressure reduction device
24 and the by-pass passageway 29-1 are connected and the point where
the check valve 30a is connected to the outside heat exchanger 21.
The check valve 30b is for preventing the refrigerant from being
introduced into the downstream heat exchanger 19 during a cooling
operation, as will be seen later.
During a cooling operation, the switching valve 27 is in its first
position, as shown by the solid line, where the first and second
ports 27-1 and 27-2 are connected and third and fourth ports 27-3
and 27-4 are connected. The first electromagnetic valve 28 is de-energized
(closed) and a second electromagnetic valve 29 is de-energized (closed).
As a result, a recirculated flow of refrigerant is obtained in the
following order, that is, the outlet 22-2 of the compressor, the
first and second ports 27-1 and 27-2 of the electromagnetic valve
27 (arrow C), the check valve 30a, the outside heat exchanger 21,
the first pressure reduction device 23 (arrow C), the upstream heat
exchanger 18, the accumulator 25, and the inlet 22-1 of the compressor
22. In this case, the outside heat exchanger 21 operates as a condenser
for liquidizing the refrigerant, and the upstream heat exchanger
18 operates as an evaporator for absorbing heat from the air in
the duct, i.e., for cooling the air. During the cooling operation,
the check valve 30b prevents the gaseous refrigerant from being
introduced into the downstream heat exchanger 19. The liquid refrigerant
in the downstream heat exchanger 19 is returned to the accumulator
25 via the fourth and third ports 27-3 and 27-4 of the switching
valve 27.
During a heating operation, the switching valve 27 is in its second
position as shown by the dotted line where the first and third ports
27-1 and 27-3 are connected and second and fourth ports 27-2 and
27-4 are connected. The first electromagnetic valve 28 is energized
(opened), and a second electromagnetic valve 29 is de-energized
(closed). As a result, a recirculated flow of refrigerant is obtained
in the following order, that is, the outlet 22-2 of the compressor,
the first and third ports 27-1 and 27-3 of the electromagnetic valve
27 (arrow H), the downstream heat exchanger 19, the second pressure
reduction device 24 (arrow H), the check valve 30b, the outside
heat exchanger 21, the first electromagnetic valve 28 (arrow H),
the accumulator 25, and the inlet 22-1 of the compressor 22. The
upstream heat exchanger 18 operates as a condenser for liquidizing
the refrigerant, and the outside heat exchanger 21 operates as a
evaporator. Thus, heat is emitted from the downstream heat exchanger
19 to the air flow in the duct 2 for heating the air issued to the
cabin.
During a dehumidifying operation, the switching valve 27 is in
its second position, as shown by the dotted line, where the first
and third ports 27-1 and 27-3 are connected and second and fourth
ports 27-2 and 27-4 are connected. The first electromagnetic valve
28 is de-energized (closed), a second electromagnetic valve 29 is
energized (opened). As a result, a recirculated flow of refrigerant
is obtained in the following order, that is, the outlet 22-2 of
the compressor, the first and second ports 27-1 and 27-3 of the
electromagnetic valve 27 (arrow D), the downstream heat exchanger
19, the second electromagnetic valve 29 (arrow D), the check valve
30b, the outside heat exchanger 21, the first pressure reduction
device 23 (arrow D), the upstream heat exchanger 18, the accumulator
25, and the inlet 22-1 of the compressor 22. In this case, the downstream
heat exchanger 19 operates as a condenser for liquidizing the refrigerant,
and the upstream heat exchanger 21 operates as an evaporator. Thus,
the air is cooled at the upstream heat exchanger 18 and the dehumidifying
air is heated at the downstream heat exchanger 19.
In FIG. 2, a control circuit 31 constructed as a microcomputer
system is provided for controlling the auxiliary heater 20, the
outside fan 26, the inverter 42 for the electric motor 22A of the
compressor 22, the switching valve 27, the first and second electromagnetic
valves 28 and 29, and the dampers 7, 14, 15 and 16 in FIG. 1.
FIG. 3 shows an arrangement of a control panel 32 for the control
circuit 31 as a microcomputer in FIG. 2. The control panel 32 in
FIG. 3 is arranged at a suitable location in the interior of the
automobile. The panel 32 is provided with a mode selection section
33 for selecting a desired mode, an air amount control switch 34
for obtaining a desired amount of air flow into the cabin, an inlet
selection switch 35 for selecting an air inlet between the inside
air mode and the outside air mode, a mode selection section 36 for
selecting a desired mode, a de-icing switch 37 for de-icing the
outside heat exchanger 21 when using the heating mode, and a temperature
control lever 38 for controlling the rotational speed of the compressor
22 at the respective modes as selected. The flow amount section
33 includes a high level mode function 33-1 for obtaining an air
flow from the upper (ventilation) outlets 11, a bi-level mode function
33-2 for obtaining an air flow from both the upper and lower outlets
11 and 12, a bottom level mode function 33-3 for obtaining an air
flow from the lower level outlets 12, a DEF/VENT mode function 33-4
for obtaining an air flow from both the defroster outlet 13 and
the lower level outlet 12, and a defroster mode button 33-5 for
obtaining an air flow from the defroster outlet 33-5. The air amount
control switch 34 is for switching the amount of air in the duct
2 between a high (H), medium (M) and low (L) amounts. The selection
switch 35 is for selecting between a condition where the outside
air is introduced, a condition where the inside air is recirculated,
and a condition where both the outside air introduction and the
inside air recirculation takes place. The mode select section 36
includes a function 36-1 for stopping the operation of the system,
a function 36-2 for controlling the operation of the fan 4, a function
36-3 for obtaining a cooling operation, a function 36-4 for obtaining
a heating operation, and a function 36-5 for obtaining a dehumidifying
(DRY) operation. In addition to the above, on the panel 32, an automatic
temperature control switch 40 is provided for automatically determining
various operations such as an air outlet mode selection, an air
amount control and an air inlet switching operation in accordance
with the target temperature of the air to be sent to the interior
of the vehicle.
In FIG. 2, an inverter 42 is for changing a direct current from
a battery 44 to an AC current with a frequency that changes in a
continuous or a step like manner, and which is applied to the electric
motor 22A of the compressor 22, so that the rotational speed of
the compressor 22 is controlled so as to obtain a desired outlet
volume of refrigerant from the outlet 22-2 of the compressor 22
for controlling the temperature of the air issued to the interior
of the vehicle.
According to the present invention, upon starting a heating operation,
the control circuit 31 compares the electric power consumed if the
refrigerating cycle 17 is selected with the power consumed if an
electric heater 20 is selected, and the heating operation that consumes
a smaller amount of electric power is selected. According to this
embodiment, in order to measure the electric power consumed when
undergoing an heating operation using the refrigerating cycle 17,
a value of the electric power consumed at the electric motor 22A
for operating the compressor 22 and the inverter 42 are directly
measured, to which the electric power consumed by the fan 4 and
the electric power consumed by the outside fan 26 are added. An
average value of the added values for a predetermined period in
a range between 5 to 20 minutes is obtained as the electric power
consumed by the refrigerating cycle. In order to do this, as shown
in FIG. 2, a sensor 46 is provided for detecting a value of the
direct current applied from the battery 44 to the inverter 42, so
that the electric power consumed at the electric motor 22A for driving
the refrigerant compressor 22 and the inverter 42 can be obtained.
Electric power consumption by the fan 4 can be calculated from the
set value of the electric voltage applied to the electric motor
10 of the fan 4, which is determined by the control circuit 31.
The set value is controlled by the setting of the air flow amount
control switch 34. Electric power consumption by the outside fan
26 is calculated based on the set voltage value of the electric
motor 26-1, which is also determined by the control circuit 31.
The electric power consumed when undergoing an heating operation
using the electric heater 20 is calculated as a sum of electric
power consumption by the heater 20 as the target heating capacity
calculated from the difference in the target temperature determined
by the position of the temperature control lever 38 and the temperature
of the air drawn and by the set value of the air using the fan 4,
and of electric power consumed by the fan 4 determined by the set
air amount using the fan 4.
It should be noted that the initial setting when the heating operation
is selected is the heating operation using the refrigerating cycle.
FIG. 4 shows very generally a flow chart of a routine executed
by the control circuit 31 for controlling the air conditioning apparatus
according to the present invention. At step 100 it is determined
whether the auto-mode switch 40 is ON. When the auto-mode switch
40 is OFF, the routine goes to step 101, where it is determined
if the cooling switch is ON. When the cooling button 36-3 has been
pushed, the cooling switch is made ON, so that the routine goes
to step 102, where the cooling operation is executed. As already
explained, during the cooling operation, the flow of refrigerant
as shown by the arrow C in FIG. 2 is obtained.
When it is not undergoing a cooling operation at step 101, the
routine goes to step 104, where it is determined whether the heating
switch is ON. When the heating button 36-4 is pushed, the heating
switch is made ON, so that the routine goes to step 106, where the
heating operation is executed by the refrigerating cycle 17 and
the electric heater 20, which involve less electric power consumption.
As already explained, upon undergoing an heating operation by the
refrigerating cycle, the flow of refrigerant, as shown by the arrow
H in FIG. 2, is obtained.
When not undergoing an heating operation at step 104, the routine
goes to step 108, wherein it is determined whether the dehumidifying
switch is ON. When the dehumidifying button 36-5 is pushed, the
dehumidifying switch is turned ON, so that the routine goes to step
110, where the dehumidifying operation is executed. As already explained,
during the dehumidifying operation, the flow of refrigerant, as
shown by the arrow D in FIG. 2 is obtained.
When it is determined that the auto-mode switch 40 is ON, the routine
goes to step 111, where the auto-mode operation is carried out.
Namely, in accordance with the desired temperature, a heating operation
or cooling operation is automatically selected as is done in a well
known manner.
FIG. 5 shows a heating operation executed at step 106 in FIG. 4
or step 111 when the heating operation is carried out during the
auto-mode operation. At step 120, it is determined whether this
is the first cycle to be executed after the heating switch is turned
on or a heating condition is changed by operating the temperature
control lever 38 or air control switch 34. When it is determined
that this is the first cycle after the heating button 36-4 is pushed
or the heating conduction is changed by moving the temperature control
lever 38 or air amount control switch 34, the routine goes to step
121, where the heating operation using the refrigerating cycle 17
is executed. In this case, the flow of refrigerant as shown by the
arrows H is obtained, and the rotational speed of the compressor
22 is controlled in accordance with the position of the temperature
control lever 38. The routine then flows to step 122, where it is
determined whether a predetermined time TI has elapsed after it
is determined, at step 120, that the heating switch is turned on
or a heating operation is varied. This predetermined time TI is
a value in a range, for example, between 5 to 20 minutes, for obtaining
a stable heating operation by the refrigerating cycle 17. When the
predetermined time interval TI has not elapsed, the steps 124 to
132 are by-passed, and returned to the main routine.
When it is determined that the predetermined time TI has elapsed
at step 122, the routine goes to step 124, where the electric power
consumption A for the heating operation by the refrigerating cycle
17 is calculated based on set values of the air flow of the inside
fan 4 and the outside fan 26 and on the electric power consumption
by the electric motor 22A and inverter circuit 42 obtained from
the electric current sensed by the electric current sensor 46. The
routine then goes to step 126, where the electric power consumption
B by the electric heater 20 is calculated for obtaining the same
heating capacity as obtained by the heating operation using the
refrigerating cycle 17. The electric power consumption B is a sum
of the electric power consumption of the fan 4 obtained from the
setting of the air amount using the switch 34 and the electric power
consumption by the electric heater 20 obtained from a difference
of the setting of the temperature of the air by the control lever
38 from the air temperature as introduced. The routine then goes
to step 128, where it is determined if the electric power consumption
A of the heating operation using the refrigerating cycle 17 is larger
than the electric power consumption B of the heating operation using
the electric heater 20. When it is determined that A.ltoreq.B, the
routine by-passes step 130 and 132, so that execution of the heating
operation by the refrigerating cycle continues.
The change in heating conditions makes the heating operation using
the electric heater much more economical than the heating operation
using the refrigerating cycle. In this situation, it is determined
that the electric power consumption A of the heating operation using
the refrigerating cycle 17 is larger than the electric power consumption
B of the heating operation using the electric heater 20 at step
128, so that the routine now flows to step 130, where the refrigerating
cycle is stopped, i.e., the rotation of the compressor 22 is stopped,
and to step 132, where the heating operation using the electric
heater 20 is executed. Thus, the electric current to the electric
heater 20 is controlled in accordance with the position of the temperature
control lever 38.
As is clear from the above, according to the first embodiment,
even in the case that the heating operation using the electric heater
20 is selected for a preceding cycle, a switch to another mode by
the mode selection switch 36 or an increase in the air flow amount
by the air amount control switch 34 or a change in the position
of the temperature control lever 38 causes an affirmative determination
at step 120, so that the electric heater is at least once stopped,
and the heating operation using the refrigerating cycle 17 is started
at step 121 for at least the period TI so as to check whether electric
power consumption using the refrigerating cycle is larger than that
using the electric heater 20 to obtain the same heating capacity
(steps 124 to 128).
According to the embodiment of the present invention, during the
heating operation using the refrigerating cycle 17, a calculated
value of the electric power consumed by the heating operation using
the electric heater larger than the electric power consumed during
the refrigerating cycle causes the heating operation to change to
that using the electric heater. As a result, an effective use of
the electric power of the battery 44 of an automobile is obtained,
so that the service life of the battery before a charging operation
is required can be prolonged.
Furthermore, the upstream heat exchanger 18 and the downstream
heat exchanger 19 arranged in the duct 2 always operate as the evaporator
and the condenser, respectively, irrespective of the mode selected.
As a result, a change in the mode does not cause the heat exchanger
18 or 19 to switch its function between the evaporator and the condenser.
As a result, a change in the mode does not result in the drain water
evaporating; thus, condensation does not form on the windshield.
It should be noted that the air conditioning apparatus according
to the present invention is suitable for an electric car without
an additional heating source.
FIG. 6 shows a second embodiment of the present invention. This
embodiment features steps 120 to 122 in FIG. 5 eliminated, and,
at step 124-1 corresponding to step 124 in FIG. 5, an estimated
value of electric power consumption A using the refrigerating cycle
is calculated. Namely, in this embodiment, steps for operating the
refrigerating cycle for a time TI so as to obtain an actual value
of electric power consumption A are eliminated. FIG. 7 is a detail
of step 124-1 for calculating the estimated value of electric power
consumption A. Namely, at step 160, setting of the various switches
and output of various sensors, such as the set temperature T.sub.set
by the temperature control lever 38, the inside air temperature
T.sub.r, the outside air temperature T.sub.am, and the sun radiation
amount T.sub.s. At step 162, a target heating capacity QAO is calculated
using the following equation.
where are K1, K2, K3 and K4 are predetermined factors and C is
a constant.
At step 164, based on the target heating capacity QAO, the set
value of the air amount Va by the fan 4 including that determined
in the auto-mode or that determined in the manual mode, and the
inside temperature T.sub.r in the inside air inside mode or the
outside air temperature T.sub.am in the outside air inlet mode,
a target air temperature TAO issued to the cabin is calculated by
the following equation. ##EQU1## where Cp is specific heat, and
is .gamma. specific weight.
Then, at step 166, a condensing temperature T.sub.c at the downstream
heat exchanger 19 and a saturated pressure P.sub.c of the refrigerant
corresponding to the condensing temperature T.sub.c are calculated
based on the inside air temperature T.sub.r when the inside air
inlet mode is selected or the outside air temperature T.sub.am when
the outside air inlet mode is selected as the target air temperature
TAO as issued to the cabin, and the temperature efficiency .phi..sub.ac
at the downstream heat exchanger 19. The condensing temperature
T.sub.c is calculated by the following equation. ##EQU2##
Next, at step 168, an intake enthalpy I.sub.1 at the inlet side
of the compressor 22, an outlet enthalpy I.sub.2 at the outlet side
of the compressor, and the recirculated amount G.sub.r of the refrigerant
are calculated. Namely, first, the evaporation temperature T.sub.e
at the outside heat exchanger 21, a saturated evaporation pressure
P.sub.e, and a recirculated amount G.sub.r of the refrigerant are
estimated. Then, using these estimated values, the outlet enthalpy
I.sub.2 is calculated. This outlet enthalpy I.sub.2 is calculated
by the following equation. ##EQU3## where .kappa. is adiabatic index,
V.sub.e is a specific volume, .eta..sub.c is adiabatic compression
efficiency, .eta..sub.m is a machine efficiency, and .eta..sub.mo
is a motor efficiency. Then, the outlet side enthalpy I.sub.3 at
the downstream heat exchanger 19 is calculated by the following
equation. ##EQU4##
Then, a heat exchange capacity Q.sub.re at the refrigerant side
of the outside heat exchanger 21 and a heat exchanging capacity
Q.sub.ae at the air side are calculated by the following equations.
where I.sub.am is an enthalpy of the outside air, and .sub.e is
an enthalpy of the air corresponding to an evaporation temperature
at the outside heat exchanger 21.
Then, the heat exchanging capacity Q.sub.re at the refrigerant
side and the heat exchanging capacity Q.sub.ae at the air side are
compared, and the heat exchanging capacity Q.sub.re at the refrigerant
side and the heat exchanging capacity Q.sub.ae at the air side are
substantially equalized by varying the evaporation temperature T.sub.e,
the saturated vapor pressure P.sub.e and the recirculated amount
G.sub.r of the refrigerant at the outside heat exchanger 21, as
estimated above. When the heat exchanging capacity Q.sub.re at the
refrigerant side and the heat exchanging capacity Q.sub.ae at the
air side are substantially equalized, the values of the intake enthalpy
Q.sub.re, the outlet enthalpy 12 and the recirculated amount G.sub.r
of the refrigerant are determined.
Finally, at step 170, based on the calculated intake enthalpy I.sub.1,
the discharge enthalpy I.sub.2, and the refrigerant recirculated
amount G.sub.r, a value of the inlet electric current L.sub.i to
be applied to the inverter circuit 42 is calculated by the following
equation. ##EQU5## where .eta..sub.i is inverter efficiency at the
inverter circuit 42. The estimated value of the electric power consumption
A during the heating operation using the refrigerating cycle is
then calculated from the inlet electric current L.sub.i added by
the electric power consumption L.sub.B by the set air amount by
the fan 4 and the electric power consumption L.sub.0D by the set
air amount by the outside fan 26.
FIG. 8 are details of step 126 in FIG. 6 for obtaining an estimation
of electric power consumption by the electric heater. Steps 190
and 192 are the same as steps 160 and 162 in FIG. 6. Namely, based
on the detected operating conditions, a target heating capacity
QAO is calculated. At step 194, the calculated heating capacity
QAO is moved to the inlet electric current of the electric heater
20 L.sub.H. At step 196, a value of electric power consumption L.sub.B
by fan 4 is added to the value of L.sub.H to obtain an estimated
value of electric power consumption during the heating operation
using the electric heater 20. It should be noted that the routine
in FIG. 8 corresponds to details of the routine at step 126 in FIG.
5 of the first embodiment. In this second embodiment, different
from the first embodiment in FIG. 5, electric power consumption
during the heating operation using the refrigerating cycle can be
calculated without executing a heating operation using the refrigerating
cycle. Namely, the heating operation is eliminated when, upon starting
the heating operation, electric power consumption by the electric
heater is smaller than that using the refrigerating cycle. Thus,
a further reduction in electric power consumption for the heating
operation can be attained.
FIG. 9 shows another embodiment, wherein the heating operation
is switched between that using only the refrigerating cycle, that
using only the electric heater, and that using both the refrigerating
cycle and the electric heater. In FIG. 8, at step 200, it is determined
whether a required heating capacity is low, medium or high, and
when the required heating capacity is medium, the routine proceeds
goes to step 202 where only the refrigerating cycle is carried out.
When the heating requirement is low, steps 204 to 208 are executed.
Namely, at step 204, electric power consumption A using the refrigerating
cycle, and at step 206, electric power consumption B using the electric
heater 20 are calculated. At step 208, it is determined that the
value of A is larger than the value of B, and when electric power
consumption A using the refrigerating cycle is smaller than electric
power consumption B using the electric heater 20, the routine proceeds
to step 202, where a heating operation using only the refrigerating
circuit 17 is realized. When electric power consumption B by the
electric heater 20 is smaller than electric power consumption A
by the refrigerating cycle, the routine proceeds to step 210, where
a heating operation using only the electric heater 20 is realized.
When the required heating capacity is high, the routine proceeds
to step 212, where the heating operation using both the refrigerating
cycle and the electric heater 20 is executed.
In the second or third embodiment where both estimated values of
electric power consumption A and B are calculated, the heating operation
that provides a smaller value is selected. In this case, a hysteresis
is provided so that once one of the heating operations of the refrigerating
cycle and the electric heater is selected because one provides smaller
electric power consumption, switching to the other heating operation
is allowed to occur when electric power consumption thereof becomes
larger than the other by a predetermined small value. This hysteresis
is to prevent the occurrence of so-called "hunting".
Control of the volume of the refrigerant compressor for varying
the heating capacity using the refrigerating cycle in the above
embodiment can be replaced by the provision of an air mix damper
for controlling the ratio of the amount of air in contact with the
heat exchanger for heating the air equal to the amount of air by-passing
the heat exchanger, for heating the air.
Control of the electric current to the electric heater 20 for varying
the heating volume can be replaced by the provision of an air mix
damper for controlling the ratio of the amount of air contacting
the electric heater to the amount of air by-passing the electric
heater.
The numerical figures in the flowcharts are purely for illustration
purposes, and the present invention should not be limited to such
numerical values.
In the embodiment, the upstream heat exchanger always operates
as an evaporator. However, the present invention can also be applied
to a refrigerating cycle, where the upstream heat exchanger operates
as a condenser.
In the embodiment, the downstream heat exchanger always operates
as an condenser. However, the present invention can also be applied
to a refrigerating cycle, where the downstream heat exchanger operates
as a condenser.
In the embodiment, the air conditioning apparatus is for air conditioning
the interior of an automobile. The present invention can also be
applied to an air conditioning apparatus for domestic or industrial
use. |