U.S. patent application number 12/382441 was filed with the patent office on 2009-10-01 for refrigerant cycle system.
This patent application is currently assigned to DENSO CORPORATION. Invention is credited to Satoshi Itoh, Nobukazu Kuribayashi, Yasutaka Kuroda, Ken Matsunaga, Mitsuyo Oomura.
Application Number | 20090241570 12/382441 |
Document ID | / |
Family ID | 41115082 |
Filed Date | 2009-10-01 |
United States Patent
Application |
20090241570 |
Kind Code |
A1 |
Kuribayashi; Nobukazu ; et
al. |
October 1, 2009 |
Refrigerant cycle system
Abstract
In a refrigerant cycle system, a compression mechanism of an
electric compressor sucks and compresses refrigerant, and an
electric motor that drives the compression mechanism is cooled by
the refrigerant. A variable throttle mechanism decompresses the
refrigerant discharged from the electric compressor. A motor
temperature detector detects a temperature of the electric motor. A
motor protection determiner determines whether the temperature of
the electric motor detected by the motor temperature detector is
equal to or higher than a criterion value. A motor protection
controller controls the variable throttle mechanism so that an
opening degree of the variable throttle mechanism does not decrease
when the motor protection determiner determines that the
temperature of the electric motor is equal to or higher than the
criterion value.
Inventors: |
Kuribayashi; Nobukazu;
(Kariya-city, JP) ; Kuroda; Yasutaka;
(Nishio-city, JP) ; Oomura; Mitsuyo;
(Hekinan-city, JP) ; Matsunaga; Ken; (Kariya-city,
JP) ; Itoh; Satoshi; (Kariya-city, JP) |
Correspondence
Address: |
POSZ LAW GROUP, PLC
12040 SOUTH LAKES DRIVE, SUITE 101
RESTON
VA
20191
US
|
Assignee: |
DENSO CORPORATION
Kariya-city
JP
|
Family ID: |
41115082 |
Appl. No.: |
12/382441 |
Filed: |
March 17, 2009 |
Current U.S.
Class: |
62/225 ;
417/410.1; 62/428; 62/500; 62/505 |
Current CPC
Class: |
F25B 2600/2513 20130101;
F25B 49/005 20130101; F25B 2700/21156 20130101; F25B 2700/171
20130101; B60H 2001/3285 20130101; B60H 1/3225 20130101; B60H
2001/3238 20130101; B60H 2001/3292 20130101; F25B 49/027
20130101 |
Class at
Publication: |
62/225 ; 62/500;
62/505; 417/410.1; 62/428 |
International
Class: |
F25B 41/00 20060101
F25B041/00; F25B 1/06 20060101 F25B001/06; F25B 31/00 20060101
F25B031/00; F04B 35/04 20060101 F04B035/04; F25D 17/06 20060101
F25D017/06 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 27, 2008 |
JP |
2008-82749 |
Claims
1. A refrigerant cycle system comprising: an electric compressor
that includes a compression mechanism, which sucks and compresses
refrigerant, and an electric motor, which drives the compression
mechanism and is cooled by the refrigerant at a suction side of the
compression mechanism; a variable throttle mechanism that
decompresses the refrigerant discharged from the electric
compressor; a motor temperature detector that detects a temperature
of the electric motor; a motor protection determiner that
determines whether the temperature of the electric motor detected
by the motor temperature detector is equal to or higher than a
criterion value; and a motor protection controller that controls
the variable throttle mechanism so that opening degree of the
variable throttle mechanism does not decrease when the motor
protection determiner determines that the temperature of the
electric motor is equal to or higher than the criterion value.
2. The refrigerant cycle system according to claim 1, further
comprising a drive circuit that controls operation of the electric
motor, wherein: the drive circuit detects a motor current, which is
an electric current outputted to the electric motor, and a
rotational speed of the electric motor; and the motor temperature
detector detects the temperature of the electric motor by
calculating the temperature of the electric motor from the
rotational speed and the motor current of the electric motor, which
are detected by the drive circuit, with reference to a control
characteristic data map, which is prepared in advance and indicates
a relationship of the temperature of the electric motor with
respect to the rotational speed and the motor current of the
electric motor.
3. The refrigerant cycle system according to claim 2, wherein: the
criterion value is specified in the control characteristic data map
to corresponds to the rotational speed and the motor current of the
electric motor; and the motor protection determiner determines
whether the temperature of the electric motor calculated by the
motor temperature detector is equal to or higher than the criterion
value specified in the control characteristic data map.
4. The refrigerant cycle system according to claim 3, wherein: the
criterion value specified in the control characteristic data map is
a first criterion value; a second criterion value that is higher
than the first criterion value is specified in the control
characteristic data map; the motor protection determiner determines
whether the temperature of the electric motor calculated by the
motor temperature detector is equal to or higher than the first
criterion value; the motor protection determiner further determines
whether the temperature of the electric motor calculated by the
motor temperature detector is equal to or higher than the second
criterion value when the motor protection determiner determines
that the temperature of the electric motor calculated by the motor
temperature detector is equal to or higher than the first criterion
value; the motor protection controller controls the variable
throttle mechanism so that the opening degree of the variable
throttle mechanism does not decrease when the motor protection
determiner determines that the temperature of the electric motor
calculated by the motor temperature detector is equal to or higher
than the first criterion value and is lower than the second
criterion value; and the motor protection controller controls the
variable throttle mechanism so that the opening degree of the
variable throttle mechanism increases when the motor protection
determiner determines that the temperature of the electric motor
calculated by the motor temperature detector is equal to or higher
than the second criterion value.
5. The refrigerant cycle system according to claim 3, further
comprising: a suction refrigerant superheating degree detector that
detects a degree of superheat of the refrigerant at the suction
side of the electric compressor; and a control characteristic
selector that selects one control characteristic data map from
among a plurality of control characteristic data maps, each of
which is prepared in advance and indicates a relationship of the
temperature of the electric motor with respect to the rotational
speed and the motor current of the electric motor, on a basis of
the degree of superheat of the refrigerant detected by the suction
refrigerant superheating degree detector, wherein the motor
protection determiner determines whether the temperature of the
electric motor calculated by the motor temperature detector is
equal to or higher than the criterion value specified in the one
control characteristic data map.
6. The refrigerant cycle system according to claim 3, wherein the
refrigerant cycle system is a heat pump system that operates in a
cooling operation mode in which the refrigerant cools heat-exchange
target fluid and in a heating operation mode in which the
refrigerant heats the heat-exchange target fluid, the refrigerant
cycle system further comprising a control characteristic selector
that selects a first control characteristic data map in the cooling
operation mode from among a plurality of control characteristic
data maps, each of which is prepared in advance and indicates a
relationship of the temperature of the electric motor with respect
to the rotational speed and the motor current of the electric
motor, and selects a second control characteristic data map in the
heating operation mode from among the plurality of control
characteristic data maps so that the criterion value specified in
the first control characteristic data map is lower than the
criterion value specified in the second control characteristic data
map, wherein the motor protection determiner determines whether the
temperature of the electric motor calculated by the motor
temperature detector is equal to or higher than the criterion value
specified in the first control characteristic data map or the
second control characteristic data map that is selected by the
control characteristic selector.
7. The refrigerant cycle system according to claim 1, further
comprising a heat-radiating heat exchanger that cools the
refrigerant at a discharge side of the electric compressor,
wherein: the variable throttle mechanism decompresses the
refrigerant at an outlet side of the heat-radiating heat exchanger
so that a pressure of the refrigerant at the discharge side of the
electric compressor becomes closer to a target high pressure that
is determined on a basis of a temperature of the refrigerant at the
outlet side of the heat-radiating heat exchanger; and the motor
protection controller lowers the target high pressure when the
temperature of the electric motor detected by the motor temperature
detector is equal to or higher than the criterion value.
8. The refrigerant cycle system according to claim 7, further
comprising: a first electric blower that blows exterior air to the
heat-radiating heat exchanger; and a first electric blower
controller that controls a rotational speed of the first electric
blower, wherein the first electric blower controller raises the
rotational speed of the first electric blower when the motor
protection determiner determines that the temperature of the
electric motor detected by the motor temperature detector is equal
to or higher than the criterion value.
9. The refrigerant cycle system according to claim 6, further
comprising: an evaporator that vaporizes the refrigerant
decompressed by the variable throttle mechanism; a second electric
blower that blows heat-exchange target fluid to the evaporator; and
a second electric blower controller that controls a rotational
speed of the second electric blower, wherein the second electric
blower controller lowers the rotational speed of the second
electric blower when the motor protection determiner determines
that the temperature of the electric motor detected by the motor
temperature detector is equal to or higher than the criterion
value.
10. The refrigerant cycle system according to claim 6, further
comprising: an evaporator that vaporizes the refrigerant that is
decompressed by the variable throttle mechanism; and an
interior/exterior air switcher that switches an air introducing
mechanism between an interior air mode, in which air blown to the
evaporator is introduced from an interior, and an exterior air
mode, in which the air blown to the evaporator is introduced from
an exterior, wherein the interior/exterior air switcher switches
the air introducing mechanism to the interior air mode when the
motor protection determiner determines that the temperature of the
electric motor detected by the motor temperature detector is equal
to or higher than the criterion value.
11. The refrigerant cycle system according to claim 1, wherein the
motor temperature detector includes a motor temperature detection
sensor for detecting the temperature of the electric motor.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is based on and incorporates herein by
reference Japanese Patent Application No. 2008-082749 filed on Mar.
27, 2008.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a refrigerant cycle system
having an electric compressor.
[0004] 2. Description of Related Art
[0005] Conventionally, in an electric compressor in which a
compression mechanism and an electric motor for driving the
compression mechanism are integrated, a temperature protection
control is performed as disclosed in JP2006-291878A and
JP2005-248730A, for example. In order to avoid excessive
temperature rise of the electric motor, the temperature protection
control is performed when the temperature of an inverter, the
electric motor, etc., excessively rises due to heavy load condition
of the electric compressor.
[0006] In JP2006-291878A, the temperature of the electric motor is
evaluated on the basis of the motor speed of the electric
compressor, the input current of the inverter, etc. The excessive
temperature rise of the electric motor is avoided by stopping the
electric compressor when the evaluated temperature of the electric
motor exceeds a predetermined value. In JP2005-248730A, the
electric compressor has a construction in which refrigerant sucked
into the electric compressor cools an inverter that includes a
driving circuit for the electric motor. In the electric compressor,
the motor speed of the electric motor is raised or the electric
compressor is stopped to inhibit the temperature rise of the
inverter, which occurs when the rotational speed of the electric
converter is small although the torque that should be generated by
the electric motor is large.
[0007] In JP2006-291878A, the electric compressor is stopped in
order to avoid the temperature rise of the electric motor. However,
if a refrigerant cycle system having the electric compressor is
applied to a vehicular air conditioning system, there is a problem
that the air conditioning feeling etc. in a passenger compartment
becomes worse significantly.
[0008] The construction of the electric compressor disclosed in
JP2005-248730A is for protecting an inverter device from excessive
temperature rise. However, when the temperature of the inverter
rises, a current value inputted into the electric motor is also
large. Therefore, heat generation in the electric motor is large,
and the electric motor is in a high temperature state. In this
situation, a temperature protection control of the electric motor
is performed by stopping the electric compressor as in
JP2006-291878A, and the same problem as in JP2006-291878A
occurs.
SUMMARY OF THE INVENTION
[0009] The present invention is made in view of the above-mentioned
problem. Thus, it is an objective of the present invention to
provide a refrigerant cycle system that can perform temperature
protection control for avoiding excessive temperature rise of an
electric motor of an electric compressor without stopping the
electric compressor more than necessary.
[0010] To achieve the objective of the present invention, there is
provided a refrigerant cycle system that has an electric
compressor, a variable throttle mechanism, a motor temperature
detector, a motor protection determiner and a motor protection
controller. The electric compressor includes a compression
mechanism, which sucks and compresses refrigerant, and an electric
motor, which drives the compression mechanism and is cooled by the
refrigerant at a suction side of the compression mechanism. The
variable throttle mechanism decompresses the refrigerant discharged
from the electric compressor. The motor temperature detector
detects a temperature of the electric motor. The motor protection
determiner determines whether the temperature of the electric motor
detected by the motor temperature detector is equal to or higher
than a criterion value. The motor protection controller controls
the variable throttle mechanism so that an opening degree of the
variable throttle mechanism does not decrease when the motor
protection determiner determines that the temperature of the
electric motor is equal to or higher than the criterion value.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The invention, together with additional objectives, features
and advantages thereof, will be best understood from the following
description, the appended claims and the accompanying drawings in
which:
[0012] FIG. 1 is a schematic diagram showing the configuration of a
refrigerant cycle system according to a first embodiment of the
present invention;
[0013] FIG. 2 is a block diagram showing an electric control
portion of the refrigerant cycle system according to the first
embodiment;
[0014] FIG. 3 is a flowchart showing a process for setting an
opening degree of an electric expansion valve of the refrigerant
cycle system according to the first embodiment;
[0015] FIG. 4 is a control characteristic diagram showing a motor
temperature associated with a motor current and a motor speed of an
electric motor of an electric compressor of the refrigerant cycle
system according to the first embodiment;
[0016] FIG. 5 is a schematic diagram showing the configuration of a
refrigerant cycle system according to a second embodiment of the
present invention;
[0017] FIG. 6 is a flowchart showing a principal part of a process
for setting opening degree of an electric expansion valve of the
refrigerant cycle system according to the second embodiment;
and
[0018] FIGS. 7A, 7B are control characteristic diagrams showing a
motor temperature associated with a motor current and a motor speed
of an electric motor of an electric compressor of the refrigerant
cycle system according to the second embodiment.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
First Embodiment
[0019] A first embodiment of the present invention will be
described hereafter, referring to FIGS. 1-4. FIG. 1 is a schematic
diagram showing an entire construction of a refrigerant cycle
system according to the first embodiment, which is applied to a
vehicular air conditioning system. As shown in FIG. 1, the
vehicular air conditioning system according to the first embodiment
has an interior air conditioning unit 1 that is installed inside an
instrument panel, which is located at a front-most part of a
passenger compartment of a vehicle to form an instrument board
etc.
[0020] The interior air conditioning unit 1 has a case member 2
that is made of resin. The case member 2 forms an outer shell of
the interior air conditioning unit 1, and houses constituent
devices of the interior air conditioning unit 1 therein. This case
member 2 defines an air passage through which air is blown into the
passenger compartment of the vehicle.
[0021] An interior/exterior air switching box 3 is installed in the
most upstream portion of the air passage of the case member 2. The
interior/exterior air switching box 3 has an interior-air inlet
port 3a and an exterior air inlet port 3b. An interior/exterior air
switching door 3c is rotatably installed in the interior/exterior
air switching box 3.
[0022] The interior/exterior air switching door 3c is driven by a
servomotor (not shown) to switch between an interior air mode, an
exterior air mode and an interior/exterior air mode. In the
interior air mode, interior air (air inside the passenger
compartment) is introduced through the interior air inlet port 3a
into the passenger compartment. In the exterior air mode, exterior
air (air outside the passenger compartment) is introduced through
the exterior air inlet port 3b into the passenger compartment. In
the interior/exterior air mode, both the interior air and the
exterior air are introduced into the passenger compartment.
[0023] An electric blower 4 is installed at a downstream side of
the interior/exterior air switching box 3. The electric blower 4
blows the air into the passenger compartment. The electric blower
(second electric blower) 4 is an electrically-driven blower in
which a well-known centrifugal multi-blade fan (sirocco fan) is
driven by an electric motor 4a. The rotational speed of the
electric motor 4a can be controlled by a control voltage outputted
from an air conditioner controller 20, which will be described
later.
[0024] An evaporator 5 is installed at a downstream side of the
electric blower 4. The evaporator 5 is one of the constituent
devices that constitute a refrigerant cycle system 10, which will
be described later. Moreover, the evaporator 5 evaporates
low-pressure side refrigerant, which has flowed into the evaporator
5, to absorb heat. Thereby, the evaporator 5 functions as a cooling
heat exchanger that cools the air blown from the electric blower
4.
[0025] A heater core 6 is installed at a downstream side of the
evaporator 5 in an air flow direction. The heater core 6 is a heat
exchanger for heating, which heats the air that has passed through
the evaporator 5 by using heat of hot water that is heated by an
electric heater etc. The hot water heated by the electric heater
etc. is supplied into the heater core 6 by an electric pump (not
shown).
[0026] Bypass passages 7 are arranged on the sides of the heater
core 6. The air flows through the bypass passages 7 to bypass the
heater core 6. Moreover, air mixing doors 8 are rotatably arranged
on the sides of the heater core 6. The air mixing doors 8 functions
as an air temperature adjusting means. The air mixing door 8 are
driven by a servomotor (not shown) so that the rotation position
(opening degree) of the air mixing door 8 can be continuously
adjusted.
[0027] By adjusting the opening degree of the air mixing door 8,
the ratio between the amount of air passing through the heater core
6 and the amount of air passing through the bypass passages 7 is
adjusted. Thus, the temperature of the air on a downstream side of
the heater core 6 is adjusted. In this embodiment, the bypass
passages 7 are arranged on both sides of the heater core 6.
Accordingly, also the air mixing doors 8 are arranged on both sides
of the heater core 6, and the two air mixing doors 8 are controlled
in conjunction with each other.
[0028] A defroster blowing-out port (not shown), a face blowing-out
port (not shown) and a foot blowing-out port (not shown) are
arranged at the most downstream part of the air passage of the case
member 2. Conditioned air is blown out toward a front window glass
(windshield) of the vehicle through the defroster blowing-out port,
toward an upper body of the passenger through the face blowing-out
port, and toward feet of the passenger through the foot blowing-out
port. Opening/closing doors are rotatably arranged at upstream
sides of these blowing-out ports. The opening/closing doors open or
close by being driven by a common servomotor through the medium of
a link mechanism (not shown).
[0029] Next, the refrigerant cycle system 10 will be described. The
refrigerant cycle system 10 has an electric compressor 11, an
exterior-side heat exchanger 13, an electric expansion valve 16, an
accumulator 18, etc., in addition to the above-mentioned evaporator
5.
[0030] In the electric compressor 11, an electric motor 11a and a
compression mechanism 11b, which is driven by the electric motor
11a, are integrated. The electric motor 11a is located at a suction
side of the electric compressor 11, and is cooled by cold
refrigerant that is drawn into the electric compressor 11.
[0031] The electric motor 11a is a three phase AC motor. The
compression mechanism 11b is a well-known scroll compression
mechanism, for example. Moreover, the rotational speed of the
electric motor 11a is variably controlled by an inverter unit 19,
which will be described later.
[0032] The exterior-side heat exchanger 13 is connected with a
discharge side of the electric compressor 11. At the exterior-side
heat exchanger 13, the refrigerant, which is discharged from the
electric compressor 11 and has high temperature and high pressure,
exchanges heat with the exterior air (air outside the passenger
compartment). Thus, the exterior-side heat exchanger 13 functions
as a heat-radiating heat exchanger. The exterior air is blown to
the exterior-side heat exchanger 13 by an electrically-driven
cooling fan (first electric blower) 13a. The cooling fan 13a is
driven by an electric motor 13b. The rotational speed of the
electric motor 13b is controlled by the controlled voltage that is
outputted from the air conditioner controller 20, which will be
described later.
[0033] The electric expansion valve 16, which functions as a
variable throttle mechanism, is connected with an outlet side of
the exterior-side heat exchanger 13. The electric expansion valve
16 functions as a pressure control valve. An opening degree of the
pressure control valve is electrically controlled so that discharge
refrigerant pressure Pd, which is the pressure of refrigerant at
the discharge side of the electric compressor 11, would be a target
high pressure in a normal operation time of the refrigeration
cycle. The electric expansion valve 16 also functions as a control
valve, which inhibits temperature rise of the electric motor 11a of
the electric compressor 11 when the temperature of the electric
motor 11a is high.
[0034] Specifically, the electric expansion valve 16 includes an
electric actuator mechanism 16a and a valve mechanism that is
driven by the electric actuator mechanism 16a. A stepping motor
serves as the electric actuator mechanism 16a, for example. An
opening degree of the valve mechanism can be minutely adjusted in
accordance with a working angle of the electric actuator mechanism
16a. The opening degree of the electric expansion valve 16 is
controlled by the air conditioner controller 20, which will be
described later.
[0035] The above-mentioned evaporator 5 is connected with an outlet
side of the electric type expansion valve 16. The accumulator 18 is
connected with the outlet side of the evaporator 5. The accumulator
18 is a gas/liquid separation means, which separates the
refrigerant discharged from the evaporator 5 into gas refrigerant
(saturated gas-phase refrigerant) and liquid refrigerant (saturated
liquid-phase refrigerant), and accumulates excessive refrigerant in
the refrigeration cycle. The gas refrigerant separated in the
accumulator 18 is introduced to the suction side of the electric
compressor 11.
[0036] An outline of an electrical control unit according to the
first embodiment will be described hereafter. FIG. 2 is a block
diagram showing the electric control portion. The air conditioner
controller 20 is composed of a well-known microcomputer that
includes a CPU, a ROM, a RAM, etc. and a periphery circuit of the
microcomputer. The air conditioner controller 20 performs various
calculations and processes based on a control program that is
memorized in the ROM, to control operations of electric devices
such as the inverter unit 19 of the electric compressor 11, the
electric motor 13b of the cooling fan 13a, the electric actuator
mechanism 16a of the electric expansion valve 16 and the electric
motor 4a of the electric blower 4.
[0037] The inverter unit 19 of the electric compressor 11 will be
briefly described hereafter. The electric motor 11a of the electric
compressor 11, which is a three phase AC motor, is rotationally
driven by three phase AC electric power that is converted by and
outputted from a power device 190 of the inverter unit 19. The
rotational speed of the electric motor 11a is minutely and variably
controlled by an inverter control portion 191 (adjustable-speed
drive controlling).
[0038] The inverter control portion 191 includes a CPU 192, a
communication circuit 193, etc. The inverter control portion 191
communicates with the air conditioner controller 20 and controls
the rotational speed of the electric motor 11a of the electric
compressor 11 so that the rotational speed would be adjusted to an
optimum value.
[0039] The inverter control portion 191 detects motor current,
which is outputted to the electric motor 11a, and the rotational
speed of the electric motor 11a, and outputs the detection values
to the air conditioner controller 20. The power source of the
inverter unit 19 is a battery 21 that is mounted on the
vehicle.
[0040] An input side of the air conditioner controller 20 is
connected with a discharge pressure sensor 31, an exterior-side
refrigerant temperature sensor 32, a post-evaporator air
temperature sensor 33, etc. The discharge pressure sensor 31 is for
detecting the discharge refrigerant pressure Pd. The exterior-side
refrigerant temperature sensor 32 is for detecting exterior-side
refrigerant temperature Tho, which is the temperature of the
refrigerant at the outlet side of the exterior-side heat exchanger
13. The post-evaporator air temperature sensor 33 is for detecting
blown-out air temperature Te, which is the temperature of the air
blown from the evaporator 5.
[0041] The detection signals of sensors 34, which include an
exterior air temperature sensor, an interior air temperature
sensor, a solar radiation sensor, etc., are also inputted to the
air conditioner controller 20. These sensors 31-34 serve as various
detection means in the first embodiment. Furthermore, an air
conditioner operating panel 40 is arranged near the instrument
board (instrument panel) in the passenger compartment. Various air
conditioner operation signals are inputted from operation members
of the air conditioner operating panel 40 to the air conditioner
controller 20.
[0042] Specifically, the various air conditioner operation signals
inputted by the air conditioner operating panel 40 include an
interior temperature setting signal, an airflow volume switching
signal of the electric blower 4, an air blow mode switching signal,
an interior/exterior air introducing mode switching signal of the
interior/exterior air switching box 3, etc. The interior
temperature setting signal is set by a temperature setting switch.
The airflow volume switching signal is set by an airflow selector
switch. The air blow mode switching signal is set by an air blow
mode selector switch. The interior/exterior air introducing mode
switching signal is set by an interior/exterior air selector
switch.
[0043] Next, the operation of the refrigerant cycle system
according to the first embodiment, which has the above-described
construction, will be described hereafter. First, a basic operation
of the refrigerant cycle system 10 will be described hereafter.
When the operation member (air conditioner switch) of the air
conditioner operating panel 40 is switched and the compressor
activation commanding signal is generated, the electric motor 11a
is electrically energized through the inverter unit 19, and the
electric motor 11a rotates. The driving force of the electric motor
11a is transmitted to the compression mechanism 11b, and the
electric compressor 11 is driven.
[0044] The refrigerant is compressed by the electric compressor 11,
and the refrigerant has high temperature and high pressure. The
refrigerant having the high temperature and the high pressure flows
into the exterior-side heat exchanger 13. At the exterior-side heat
exchanger 13, the refrigerant exchanges heat with the exterior air
that is blown by the cooling fan 13a, so as to radiate heat to the
exterior air.
[0045] Then, the refrigerant discharged from the exterior-side heat
exchanger 13 is decompressed by the electric expansion valve 16 and
brought into a gas-liquid two-phase state having low temperature
and low pressure. The gas-liquid two-phase refrigerant having the
low temperature and the low pressure flows into the evaporator 5.
At the evaporator 5, the refrigerant is vaporized by absorbing heat
of the air that is blown from the electric blower 4. Thereby, the
air blown from the electric blower 4 is cooled down by the
evaporator 5, and the cooled air can be blown into the passenger
compartment.
[0046] Then, the low-pressure refrigerant that has passed through
the evaporator 5 flows into the accumulator 18. At the accumulator
18, the low-pressure refrigerant is separated into the saturated
liquid-phase refrigerant and the saturated gas-phase refrigerant.
The saturated gas-phase refrigerant is introduced from an outlet of
the accumulator 18 to the suction side of the electric compressor
11. Then, the saturated gas-phase refrigerant is sucked into the
electric compressor 11 and is compressed again.
[0047] Next, basic control process performed by the air conditioner
controller 20 according to the first embodiment will be described
hereafter. This control process begins when the air conditioner
switch is turned on under the condition that a starter switch (not
shown) of the vehicle is turned on.
[0048] First, a flag, a timer, etc. are initialized. Then,
detection signals of the sensors 31-34 and operation signals of the
air conditioner operating panel 40 are read in. Then, control
states of the actuators 4a, 13b, 16a, 19 etc. are determined.
[0049] Specifically, a target blowing-out temperature TAO, at which
the air should be blown into the passenger compartment, is
calculated based on target air temperature Tset in the passenger
compartment, interior air temperature Tr and exterior air
temperature Tam. Furthermore, based on the target blowing-out
temperature TAO, a target rotational speed of the electric blower 4
(voltage applied to the electric motor 4a), a target rotational
speed of the cooling fan 13a of the exterior-side heat exchanger 13
(voltage applied to the cooling fan 13a), a target opening degrees
of the air mixing doors 8 (control signals outputted to the
servomotor for the air mixing doors 8) are determined.
[0050] Furthermore, based on the target blowing-out temperature
TAO, a target evaporator blowing-out temperature TEO is determined.
The target blowing-out temperature TEO is a target value of cooling
degree of the evaporator 5. Then, a refrigerant discharge capacity
of the electric compressor 11 (control signal that is outputted to
the inverter unit 19) is calculated so that the blowing-out air
temperature Te of the evaporator 5 would approach the target
evaporator blowing-out temperature TEO.
[0051] Moreover, based on the exterior-side refrigerant temperature
Tho (temperature of the refrigerant at the outlet side of the
exterior-side heat exchanger 13), a target high pressure Po is
determined. By the target high pressure Po, efficiency of the
refrigeration cycle (COP) is maximized. The opening degree of the
electric expansion valve 16 (control signal that is outputted to
the electric actuator mechanism 16a) is determined so that the
discharge refrigerant pressure Pd of the electric compressor 11
would become the above-mentioned target high pressure Po.
[0052] Then, output signals are outputted from the air conditioner
controller 20 to the actuators 4a, 11a, 13b, 16a, etc. so as to
realize the control states of the actuators 4a, 13b, 16a, 19 etc.,
which have been already determined.
[0053] In the electric compressor 11 in the first embodiment, the
electric motor 11a is cooled by the cold refrigerant that is drawn
into the electric compressor 11. When the motor current, which is
outputted from the inverter unit 19 to the electric motor 11a, is
large and the rotational speed of the electric motor 11a is small,
occasionally the electric motor 11a is not sufficiently cooled down
by the cold refrigerant that is drawn into the electric compressor
11, and the electric motor 11a can be in a high temperature
state.
[0054] In such a case, the electric compressor 11 is stopped in a
conventional refrigerant cycle system. In the first embodiment, the
opening degree of the electric expansion valve 16 is controlled
instead, to perform a temperature protection control for avoiding
temperature rise of the electric motor 11a of the electric
compressor 11.
[0055] The temperature protection control for the electric motor
11a in the first embodiment will be described hereafter with
reference to FIGS. 3, 4. FIG. 3 is a flowchart showing a process
for setting the opening degree of the electric expansion valve 16,
which is performed by the air conditioner controller 20. FIG. 4 is
a control characteristic diagram showing the temperature of the
electric motor 11a associated with the motor current and the
rotational speed of the electric motor 11a of the electric
compressor 11 in the first embodiment.
[0056] The process for setting the opening degree of the electric
expansion valve 16, which is shown in FIG. 3, begins when the
refrigeration cycle is started, that is, when the electric
compressor 11 is started. First, at step S100, the air conditioner
controller 20 reads the detection signals of the sensors, the
various air conditioner operation signals sent from the air
conditioner operating panel 40, etc.
[0057] Specifically, the air conditioner controller 20 reads the
discharge refrigerant pressure Pd that is detected by the discharge
pressure sensor 31, the exterior-side refrigerant temperature Tho
(temperature of the refrigerant at the outlet side of the
exterior-side heat exchanger 13) that is detected by the
exterior-side refrigerant temperature sensor 32, the value of the
motor current that is outputted from the inverter unit 19 to the
electric motor 11a, the rotational speed of the electric motor 11a,
etc.
[0058] Next, at step S200, the air conditioner controller 20
calculates a control amount of the opening degree of the electric
expansion valve 16 so that the discharge refrigerant pressure Pd,
which is detected by the discharge pressure sensor 31, would become
the target high pressure Po, which is determined based on the
exterior-side refrigerant temperature Tho (temperature of the
refrigerant at the outlet side of the exterior-side heat exchanger
13) that is detected by the exterior-side refrigerant temperature
sensor 32. In the first embodiment, the opening degree of the
electric expansion valve 16 is increased when the control amount of
the opening degree is larger than zero, and the opening degree of
the electric expansion valve 16 is decreased when the control
amount of the opening degree is smaller than zero.
[0059] Moreover, in the first embodiment, the control
characteristic shown in FIG. 4 is memorized beforehand in the ROM
etc. of the air conditioner controller 20. In this control
characteristic, the temperature of the electric motor 11a is
associated with the rotational speed and the motor current of the
electric motor 11a, which are detected by the inverter unit 19. The
temperature of the electric motor 11a is inversely proportional to
a flow rate of the refrigerant, namely, the rotational speed of the
electric motor 11a. The temperature of the electric motor 11a is
proportional to a heat generation in the electric motor 11a,
namely, a square of the value of the motor current. For example,
the temperature of the electric motor 11a becomes low when the
rotational speed of the electric motor 11a is large and the motor
current is small. The temperature of the electric motor 11a becomes
high when the rotational speed of the electric motor 11a is small
and the motor current is large.
[0060] In the first embodiment, the temperature of the electric
motor 11a is calculated and detected based on the control
characteristic. Alternatively, the temperature of the electric
motor 11a may be calculated by inputting the rotational speed of
the electric motor 11a and the value of the motor current into a
computing equation, etc.
[0061] In the control characteristic, criterion values of the
temperature of the electric motor 11a are specified in order to
determine whether the temperature rise of the electric motor 11a
should be avoided or not. Specifically, in the control
characteristic of the first embodiment, first to third criterion
values are specified as the criterion values of the temperature of
the electric motor 11a, and a limit value of the temperature of the
electric motor 11a is also specified.
[0062] The relation between the criterion values and the limit
value is: (first criterion value)<(second criterion
value)<(third criterion value)<(limit value). The first to
third criterion values and the limit value of the temperature of
the electric motor 11a are specified so that the rotational speed
of the electric motor 11a would increases as the value of the motor
current increases on a condition that the temperature of the
electric motor 11a is kept at either one of the first to third
criterion values and the limit value. A first criterion line, which
indicates the rotational speed and the motor current of the
electric motor 11a that correspond to the first criterion value, a
second criterion line, which indicates the rotational speed and the
motor current of the electric motor 11a that correspond to the
second criterion value, a third criterion line, which indicates the
rotational speed and the motor current of the electric motor 11a
that correspond to the third criterion value, and a limit line,
which indicates the rotational speed and the motor current of the
electric motor 11a that correspond to the limit value, are in
parallel with each other.
[0063] The first to third criterion lines and the limit line
separate the temperature of the electric motor 11a of the electric
compressor 11 into ranges A-D and an off-limit range. Specifically,
in the range A, the temperature of the electric motor 11a is lower
than the first criterion value on the basis of the control
characteristic that associates the temperature of the electric
motor 11a with the rotational speed and the motor current of the
electric motor 11a. In the range B, the temperature of the electric
motor 11a is equal to or higher than the first criterion value and
is lower than the second criterion value. In the range C, the
temperature of the electric motor 11a is equal to or higher than
the second criterion value and is lower than the third criterion
value. In the range D, the temperature of the electric motor 11a is
equal to or higher than the third criterion value and is lower than
the limit value. In the off-limit range, which is a diagonally
shaded area in FIG. 4, the temperature of the electric motor 11a is
equal to or higher than the limit value.
[0064] The ranges A-D and the off-limit range are indices that
indicate the states of the temperature of the electric motor 11a of
the electric compressor 11. The range A indicates a normal state of
the temperature of the electric motor 11a. The off-limit range
indicates an abnormal state of the temperature of the electric
motor 11a, in which the temperature of the electric motor 11a is
excessively high (at 120.degree. C., for example) and an insulation
failure of a winding can occur in the electric motor 11a. The
ranges B-D are set between the range A and the off-limit range, and
indicate a state where the temperature protection control for the
electric motor 11a is necessary.
[0065] At step S300 in FIG. 3, the air conditioner controller 20
calculates and detects current temperature of the electric motor
11a in accordance with the rotational speed and the motor current
of the electric motor 11a on the basis of the control
characteristic. Then, the air conditioner controller 20 calculates
the current temperature of the electric motor 11a is in which range
of the above-mentioned control characteristic. Then, at step S400,
the air conditioner controller 20 determines whether the
temperature of the electric motor 11a, which has been calculated at
step S300, is in the range A or not.
[0066] If it is determined at step S400 that the temperature of the
electric motor 11a is in the range A, the air conditioner
controller 20 sets the control amount that has been calculated at
step S200 as the control amount of the opening degree of the
electric expansion valve 16 (step S500). That is, the discharge
refrigerant pressure Pd of the electric compressor 11 can be
maintained at the target high pressure Po, which realizes the
optimal control of the refrigeration cycle.
[0067] If it is not determined at step S400 that the temperature of
the electric motor 11a is in the range A, the air conditioner
controller 20 determines at step S410 whether the control amount of
the opening degree of the electric expansion valve 16, which has
been calculated at step S200, is larger than zero or not. If it is
determined at step S410 that the control amount is smaller than
zero, the opening degree of the electric expansion valve 16 is
being controlled to decrease. Thus, at step S420, the air
conditioner controller 20 sets the control amount at zero so as to
change the control amount to a value that will not change the
opening degree of the electric expansion valve 16. If it is
determined at step S410 that the control amount is larger than or
equal to zero, the air conditioner controller 20 does not change
the control amount, and the process goes to step S430.
[0068] Next, at step S430, the air conditioner controller 20
determines whether the temperature of the electric motor 11a is in
the range B or not. If it is determined at step S430 that the
temperature of the electric motor 11a is in the range B, the
process goes to step S500, and the air conditioner controller 20
sets the control amount that is larger than or equal to zero as the
control amount of the opening degree of the electric expansion
valve 16.
[0069] Thus, if the temperature of the electric motor 11a is in the
range B, at least the opening degree of the electric expansion
valve 16 is controlled not to decrease. That is, at least the
increase of the discharge refrigerant pressure Pd of the electric
compressor 11 is inhibited, so that it is possible to avoid the
load increase of the electric compressor 11 and the temperature
rise of the electric motor 11a.
[0070] If it is not determined at step S430 that the temperature of
the electric motor 11a is in the range B, the air conditioner
controller 20 determines at step S440 whether the temperature of
the electric motor 11a is in the range C or not. If it is
determined at step S440 that the temperature of the electric motor
11a is in the range C, at step S450, the air conditioner controller
20 adds a first predetermined value alpha to the control amount of
the opening degree of the electric expansion valve 16, which has
been calculated at step S200, or adds the first predetermined value
alpha to the control amount that has been set at zero at step
S420.
[0071] Then, the process goes to step S500, and the air conditioner
controller 20 sets the control amount, to which the first
predetermined value alpha is added, as the control amount of the
opening degree of the electric expansion valve 16. Thus, if the
temperature of the electric motor 11a is in the range C, the
opening degree of the electric expansion valve 16 is controlled to
increase. That is, the discharge refrigerant pressure Pd of the
electric compressor 11 is decreased, so that it is possible to
decrease the load of the electric compressor 11 and to avoid the
temperature rise of the electric motor 11a.
[0072] If it is not determined at step S440 that the temperature of
the electric motor 11a is in the range C, the air conditioner
controller 20 determines at step S460 whether the temperature of
the electric motor 11a is in the range D or not. If it is
determined at step S460 that the temperature of the electric motor
11a is in the range D, at step S470, the air conditioner controller
20 adds a second predetermined value beta to the control amount of
the opening degree of the electric expansion valve 16, which has
been calculated at step S200, or adds the second predetermined
value beta to the control amount that has been set at zero at step
S420.
[0073] Then, the process goes to step S500, and the air conditioner
controller 20 sets the control amount, to which the second
predetermined value beta is added, as the control amount of the
opening degree of the electric expansion valve 16. The second
predetermined value beta, which is added at step S460, is a value
larger than the first predetermined value alpha, which is added at
step S450 ((first predetermined value alpha)<(second
predetermined value beta)). Thus, if the temperature of the
electric motor 11a is in the range D, the opening degree of the
electric expansion valve 16 is controlled to increase more than
when the temperature of the electric motor 11a is in the range
C.
[0074] That is, by gradually decreasing the discharge refrigerant
pressure Pd of the electric compressor 11, it become possible to
avoid the temperature rise of the electric motor 11a by decreasing
the load of the electric compressor 11, and to prevent a sudden
change of the discharge refrigerant pressure Pd of the electric
compressor 11, which degrades the air conditioning feeling etc. in
the passenger compartment.
[0075] If it is not determined at step S460 that the temperature of
the electric motor 11a is in the range D, the air conditioner
controller 20 determines at step S480 that the temperature of the
electric motor 11a is abnormal, and memorizes the abnormality in
the ROM etc. of the air conditioner controller 20.
[0076] If the temperature of the electric motor 11a is in the
off-limit range, it is anticipated that the refrigerant cycle
system 10 can break down. Therefore, the operation of the electric
compressor 11 is stopped. The determination processes at steps
S400, S430, S440, S460 correspond to a protection determining
means, and the processes at steps S420, S450, S470 correspond to a
motor protection control means.
[0077] As described above, when the temperature of the electric
motor 11a of the electric compressor 11 is equal to or higher than
the first criterion value, at least the opening degree of the
electric expansion valve 16 is controlled not to decrease. Thus, it
is possible to avoid the increase of the discharge refrigerant
pressure Pd of the electric compressor 11. Thereby, at least the
increase of the load of the electric compressor 11 is avoided, and
it is possible to avoid the increase of the motor current that is
outputted to the electric motor 11a. Therefore, it is possible to
perform the temperature protection control for avoiding temperature
rise of the electric motor 11a without stopping the electric
compressor 11.
[0078] Moreover, the temperature of the electric motor 11a is
calculated and detected on the basis of the control characteristic
that associates the temperature of the electric motor 11a with the
rotational speed and the motor current of the electric motor 11a.
Thus, it is possible to perform the temperature protection control
for avoiding temperature rise of the electric motor 11a when the
temperature of the electric motor 11a is equal to or higher than a
criterion value.
[0079] Moreover, in detecting the temperature of the electric motor
11a on the basis of the control characteristic, it is possible to
perform the temperature protection control for avoiding temperature
rise of the electric motor 11a without providing the electric motor
11a with a detecting device exclusively for detecting the
temperature of the electric motor 11a. Thus, it is possible to
simplify the construction of the electric compressor 11.
[0080] Moreover, by specifying more than two criterion values (the
first to third criterion values) as the criterion value in the
control characteristic, it is possible to gradually adjust the
opening degree of the electric expansion valve 16. Therefore, it is
possible to inhibit the air conditioning feeling etc. in the
passenger compartment from becoming degraded. In the first
embodiment, the first to third criterion values are specified as
the criterion value. The present invention is not limited to this,
and it is also possible to increase or decrease the number of the
criterion value(s).
Second Embodiment
[0081] Next, a second embodiment of the present invention will be
described hereafter, referring to FIGS. 5-7. Elements that are
substantially the same as or equivalent to those in the first
embodiment have the same reference numerals as in the first
embodiment, and are not described again. FIG. 5 is a schematic
diagram showing an entire construction of a refrigerant cycle
system according to the second embodiment, which is applied to a
vehicular air conditioning system. The refrigerant cycle system 10
according to the second embodiment is configured as a heat pump
refrigeration cycle that can be switched between a cooling
operation mode and a heating operation mode.
[0082] As shown in FIG. 5, in the second embodiment, a heater core
6 is arranged in a case member 2 of an interior air conditioning
unit 1. The heater core 6 is one of the constituent devices that
constitute the refrigerant cycle system 10. The heater core 6
functions as a use-side heat exchanger, which heats the air that
has passed through an evaporator 5 by using the refrigerant having
high temperature and high pressure as a heat source. The heater
core 6 functions also as a heat-radiating heat exchanger, which
cools the refrigerant by radiating heat to the air that has passed
through the evaporator 5.
[0083] The refrigerant cycle system 10 according to the second
embodiment has the evaporator 5, the heater core 6, an electric
compressor 11, a first electric expansion valve 12, an
exterior-side heat exchanger 13, an interior heat exchanger 15, a
second electric expansion valve 16, which corresponds to the
electric expansion valve in the first embodiment, an accumulator
18, etc. In the following description, the heater core 6 is
explained as a use-side heat exchanger.
[0084] An inlet side of the above-mentioned use-side heat exchanger
6 is connected with a discharge side of the electric compressor 11.
The first electric expansion valve 12, which functions as a
variable throttle mechanism, is connected with an outlet side of
the use-side heat exchanger 6.
[0085] The first electric expansion valve 12 functions also as a
high pressure control valve. The opening degree of the high
pressure control valve is electrically controlled by control
signals that are outputted from an air conditioner controller 20 so
that discharge refrigerant pressure Pd of the refrigeration cycle
would become a target high pressure Po in the heating operation
mode, which will be described later. The first electric expansion
valve 12 includes an electric actuator mechanism 12a and a valve
mechanism.
[0086] The exterior-side heat exchanger 13 is connected with an
outlet side of the first electric expansion valve 12. The
refrigerant cycle system 10 according to the second embodiment has
a first bypass passage 14a. The first bypass passage 14a connects
the outlet side of the use-side heat exchanger 6 directly with an
inlet side of the exterior-side heat exchanger 13 so that the
refrigerant can bypass the first electric expansion valve 12. A
first open/close valve 14 is arranged in the first bypass passage
14a to open and close the first bypass passage 14a. The first
open/close valve 14 is an electromagnetic valve that is controlled
to be opened and closed by control voltage that is outputted from
the air conditioner controller 20.
[0087] In the cooling operation mode, which will be described
later, the exterior-side heat exchanger 13 functions as a
heat-radiating heat exchanger that cools the refrigerant by
radiating heat of the refrigerant to the exterior air in an
analogous fashion as in the first embodiment. In the heating
operation mode, the exterior-side heat exchanger 13 functions as a
heat-absorbing heat exchanger that vaporizes the refrigerant by
absorbing heat from the exterior air.
[0088] A first refrigerant passage 15a of the interior heat
exchanger 15 is connected with an outlet side of the exterior-side
heat exchanger 13. In the cooling operation mode, which will be
described later, the interior heat exchanger 15 cools the
refrigerant at the outlet side of the exterior-side heat exchanger
13 by exchanging heat between the refrigerant at the outlet side of
the exterior-side heat exchanger 13, which passes through the first
refrigerant passage 15a of the interior heat exchanger 15, and the
refrigerant at a suction side of the electric compressor 11, which
passes through a second refrigerant passage 15b of the interior
heat exchanger 15.
[0089] The second electric expansion valve 16, which functions as a
variable throttle mechanism, is arranged at an outlet side of the
first refrigerant passage 15a of the interior heat exchanger 15.
The second electric expansion valve 16 has substantially the same
construction as the first electric expansion valve 12, and has an
electric actuator mechanism 16a and a valve mechanism.
[0090] In the cooling operation mode, which will be described
later, the second electric expansion valve 16 functions also as a
high pressure control valve. The opening degree of the high
pressure control valve is electrically controlled by the control
signals that are outputted from the air conditioner controller 20
so that the discharge refrigerant pressure Pd would become the
target high pressure Po. The evaporator 5 is connected with an
outlet side of the second electric expansion valve 16.
[0091] Furthermore, the refrigerant cycle system 10 according to
the second embodiment has a second bypass passage 17a. The second
bypass passage 17a connects an inlet side of the first refrigerant
passage 15a of the interior heat exchanger 15 directly with an
outlet side of the evaporator 5 so that the refrigerant can bypass
the second electric expansion valve 16. Moreover, a second
open/closing valve 17 is arranged in the second bypass passage 17a
to open and close the second bypass passage 17a.
[0092] The second open/close valve 17 has substantially the same
construction as the first open/close valve 14, and is an
electromagnetic valve that is controlled to be opened and closed by
control voltage that is outputted from the air conditioner
controller 20. The accumulator 18 is arranged at a downstream side
of the evaporator 5 and the second bypass passage 17a. Moreover, an
inlet side of the second refrigerant passage 15b of the interior
heat exchanger 15 is connected with an outlet of the accumulator
18, from which gas-phase refrigerant flows out. The suction side of
the electric compressor 11 is connected with an outlet side of the
second refrigerant passage 15b.
[0093] The air conditioner controller 20 performs various
calculations and processes based on a control program that is
memorized in the ROM, to control operations of the above-mentioned
actuators 4a, 11b, 12a, 13a, 14, 16a, 17, etc.
[0094] Moreover, an input side of the air conditioner controller 20
is connected with a suction pressure sensor 35, a suction
refrigerant temperature sensor 36, a discharge refrigerant
temperature sensor 37, a use-side refrigerant temperature sensor
38, etc., in addition to the construction of the first embodiment.
The suction pressure sensor 35 is for detecting suction refrigerant
pressure Ps of the electric compressor 11. The suction refrigerant
temperature sensor 36 is for detecting suction refrigerant
temperature sensor Ts of the electric compressor 11. The discharge
refrigerant temperature sensor 37 is for detecting discharge
refrigerant temperature Td of the electric compressor 11. The
use-side refrigerant temperature sensor 38 is for detecting for
detecting use-side refrigerant temperature Tco. Detection signals
of these sensors 35-38, etc. are inputted to the input side of the
air conditioner controller 20.
[0095] Furthermore, an air conditioner operating panel 40 is
provided with a cooling/heating selecting switch, etc. The
cooling/heating selecting switch is for selectively switching
between the heating operation mode, in which the air to be blown
into the passenger compartment is heated, and the cooling operation
mode, in which the air to be blown into the passenger compartment
is cooled.
[0096] Next, the operation of the refrigerant cycle system 10
according to the second embodiment, which has the above-described
construction, will be described hereafter. First, a basic operation
of the refrigerant cycle system 10 when the cooling/heating
selecting switch of the air conditioner operating panel 40 is
switched to the cooling operation mode will be described
hereafter.
[0097] In the cooling operation mode, the first open/close valve 14
is opened, the first electric expansion valve 12 is fully closed,
and the second open/close valve 17 is closed. Thus, in the cooling
operation mode, the refrigerant, which has been compressed in the
electric compressor 11 and has high temperature and high pressure,
radiates heat to the air in the use-side heat exchanger (heater
core) 6. The refrigerant that has flowed out from the use-side heat
exchanger 6 flows into the exterior side heat exchanger 13 through
the first bypass passage 14a, and further radiates heat to the
exterior air and is cooled.
[0098] The refrigerant that has flowed out from the exterior-side
heat exchanger 13 flows into the first refrigerant passage 15a of
the interior heat exchanger 15, and exchanges heat with the suction
refrigerant of the electric compressor 11, which is going to be
sucked into the electric compressor 11 and is passing through the
second refrigerant passage 15b, and is further cooled, so that the
enthalpy of the refrigerant is decreased. Thus, the enthalpy
difference (refrigeration capacity) between the refrigerant at the
inlet of the evaporator 5 and the refrigerant at the outlet of the
evaporator 5 is increased.
[0099] The refrigerant that has flowed out from the first
refrigerant passage 15a of the interior heat exchanger 15 is
depressurized at the second electric expansion valve 16. The
refrigerant that has been depressurized at the second electric
expansion valve 16 flows into the evaporator 5, and absorbs heat
from the air and evaporates. Therefore, the air that is blown into
the passenger compartment is cooled. Thus, the refrigerant that has
flowed out from the evaporator 5 flows into the accumulator 18, and
gas-phase refrigerant is separated from liquid-phase refrigerant.
Furthermore, the gas-phase refrigerant that has flowed out from the
accumulator 18 is sucked into the electric compressor 11 through
the second refrigerant passage 15b of the interior heat exchanger
15.
[0100] In the heating operation mode, the first open/close valve 14
is closed, the second open/close valve 17 is opened and the second
electric expansion valve 16 is fully closed. Thus, in the heating
operation mode, the refrigerant, which has been compressed in the
electric compressor 11 and has high temperature and the high
pressure, radiates heat to the air in the use-side heat exchanger
6.
[0101] The refrigerant that has flowed out from the use-side heat
exchanger 6 is depressurized at the first electric expansion valve
12. The refrigerant that has been depressurized at the first
electric expansion valve 12 absorbs heat at the exterior-side heat
exchanger 13 from the exterior air, and is vaporized. The
refrigerant that has flowed out from the exterior-side heat
exchanger 13 flows through the second bypass passage 17a, the
accumulator 18 and the second refrigerant passage 15b of the
interior heat exchanger 15 in sequence, and is sucked into the
electric compressor 11.
[0102] Next, the temperature protection control in the second
embodiment, in which the first and second electric expansion valves
12, 16 operates to protect the electric motor 11a of the electric
compressor 11, will be described hereafter with reference to FIGS.
6, 7A, 7B. FIG. 6 is a flowchart showing a process for setting the
opening degrees of the first and second electric expansion valves
12, 16, which is performed by the air conditioner controller 20 in
the second embodiment. FIGS. 7A, 7B are control characteristic
diagrams showing criterion values of the motor current of the
electric motor 11a of the electric compressor 11 in the second
embodiment, which are set in association with the rotational speed
of the electric motor 11a. FIG. 7A shows the control characteristic
diagram in the cooling operation mode. FIG. 7B shows the control
characteristic diagram in the heating operation mode.
[0103] First, at step S100, the air conditioner controller 20 reads
the detection signals of the sensors, the various air conditioner
operation signals sent from the air conditioner operating panel 40,
etc.
[0104] Specifically, the air conditioner controller 20 reads
discharge refrigerant pressure Pd that is detected by a discharge
pressure sensor 31, exterior-side refrigerant temperature Tho that
is detected by an exterior-side refrigerant temperature sensor 32,
use-side refrigerant temperature Tco that is detected by a use-side
refrigerant temperature sensor 38, the value of the motor current
that is outputted from the inverter unit 19 to the electric motor
11a, the rotational speed of the electric motor 11a, etc. Moreover,
the air conditioner controller 20 detects whether the
cooling/heating selecting switch of the air conditioner operating
panel 40 is switched to the cooling operation mode or to
the-heating operation mode.
[0105] Next, at step S110, the air conditioner controller 20
determines whether the cooling/heating selecting switch of the air
conditioner operating panel 40 is switched to the cooling operation
mode or not. If it is determined that the cooling/heating selecting
switch of the air conditioner operating panel 40 is switched to the
cooling operation mode, the air conditioner controller 20
calculates at step S210 a control amount of the opening degree of
the second electric expansion valve 16 so that the discharge
refrigerant pressure Pd of the electric compressor 11 can become
the target high pressure Po, which is determined based on the
exterior-side refrigerant temperature Tho of the exterior-side heat
exchanger 13.
[0106] In the second embodiment, the refrigerant that has flowed
out from the exterior-side heat exchanger 13 exchanges heat at the
interior heat exchanger 15 with the suction refrigerant of the
electric compressor 11 in the cooling operation mode. Therefore,
the suction refrigerant of the electric compressor 11 is heated by
the refrigerant that has flown out from the exterior-side heat
exchanger 13, and the temperature of the suction refrigerant is
higher than that in the heating operation mode. Accordingly, in the
cooling operation mode, the discharge refrigerant temperature is
higher than that in the heating operation mode, so that the
temperature of the electric motor 11a rises more than in the
heating operation mode. That is, the temperature of the suction
refrigerant of the electric compressor 11 in the cooling operation
mode is different from that in the heating operation mode, and the
temperature of the electric motor 11a in the cooling operation mode
is different from that in the heating operation mode even if each
the motor current and the rotational speed of the electric motor
11a is the same.
[0107] For this reason, in the second embodiment, the control
characteristic for the cooling operation mode (see FIG. 7A) and the
control characteristic for the heating operation mode (see FIG. 7B)
are separately memorized beforehand in the ROM etc. of the air
conditioner controller 20. As shown in FIGS. 7A, 7B, the criterion
temperature in the control characteristic for the cooling operation
mode is lower than the criterion temperature in the control
characteristic for the heating operation mode. Two or more control
characteristics in which the criterion values are different are
memorized in ROM etc. of the air conditioner controller 20 for each
operation mode.
[0108] Next, at step S310, the air conditioner controller 20
selects the control characteristic for the cooling operation mode.
Then, based on the selected control characteristic, the air
conditioner controller 20 calculates and detects the temperature of
the electric motor 11a from the detected rotational speed and the
motor current of the electric motor 11a. Moreover, the air
conditioner controller 20 calculates the detected temperature of
the electric motor 11a is in which range of the control
characteristic for the cooling operation mode, and the process goes
to step S400.
[0109] If it is determined at step S110 that the cooling/heating
selecting switch of the air conditioner operating panel 40 is
switched to the heating operation mode, the air conditioner
controller 20 calculates at step S220 a control amount of the
opening degree of the first electric expansion valve 12 so that the
discharge refrigerant pressure Pd of the electric compressor 11 can
become the target high pressure Po, which is determined based on
the exterior-side refrigerant temperature Tho of the exterior-side
heat exchanger 13.
[0110] Next, at step S310, the air conditioner controller 20
selects the control characteristic for the cooling operation mode.
Then, based on the selected control characteristic, the air
conditioner controller 20 calculates and detects the temperature of
the electric motor 11a from the detected rotational speed and the
motor current of the electric motor 11a. Moreover, the air
conditioner controller 20 calculates the detected temperature of
the electric motor 11a is in which range of the control
characteristic for the heating operation mode, and the process goes
to step S400. The processes at steps S310, S320 correspond to a
control characteristic selector.
[0111] As explained above, in each operation mode, a control
characteristic adapted for the operation mode is selected from two
or more control characteristics in which the criterion values are
different, and the temperature of the electric motor 11a is
detected based on the selected control characteristic. By
determining whether the detected temperature of the electric motor
11a is larger than (or equal to) the criterion value of the
selected control characteristic or not, it is possible to perform
the determination in the temperature protection control for the
electric motor 11a. Thereby, the reliability of the temperature
protection control of the electric motor 11a is raised.
Third Embodiment
[0112] Next, a third embodiment of the present invention will be
described hereafter. Elements that are substantially the same as or
equivalent to those in the first and second embodiments have the
same reference numerals as in the first and second embodiments, and
are not described again.
[0113] In the above-described second embodiment, a certain control
characteristic is selected in accordance with the operation mode,
and the temperature of the electric motor 11a is calculated and
detected from the detection value of the inverter unit 19, on the
basis of the selected control characteristic. In contrast, in the
third embodiment, two or more control characteristics in which the
criterion values are different are memorized beforehand in ROM etc.
of the air conditioner controller 20. Then, a certain control
characteristic is selected from the two or more control
characteristics in accordance with a degree of superheat of the
refrigerant at the suction side of the electric compressor 11, and
the temperature of the electric motor 11a is calculated from the
detection value of the inverter unit 19.
[0114] Specifically, suction refrigerant pressure Ps of the
electric compressor 11 is detected by the suction pressure sensor
35, and suction refrigerant temperature sensor Ts of the electric
compressor 11 is detected by the suction refrigerant temperature
sensor 36. Then, saturated vapor temperature of the refrigerant is
calculated from the detected suction refrigerant pressure Ps, and
the degree of superheat SH of the refrigerant at the suction side
of the electric compressor 11 is calculated from the suction
refrigerant temperature Ts and the saturated vapor temperature.
Alternatively, the suction refrigerant pressure Ps may be evaluated
from blown-out air temperature Te of the evaporator 5, which is
detected by a post-evaporator air temperature sensor 33.
[0115] If the degree of superheat SH of the refrigerant at the
suction side of the electric compressor 11 is large, the
temperature of the electric motor 11a rises. Therefore, a control
characteristic in which the criterion value is set low is selected
from two or more control characteristics. If the degree of
superheat SH of the refrigerant at the suction side of the electric
compressor 11 is small, the temperature of the electric motor 11a
does not rise so much. Therefore, a control characteristic in which
the criterion value is set high is selected from two or more
control characteristics.
[0116] As explained above, based on the degree of superheat SH of
the refrigerant at the suction side of the electric compressor 11,
a certain control characteristic is selected from predetermined two
or more control characteristics in which the criterion values are
different and the temperature of the electric motor 11a is
calculated and detected based on the certain control
characteristic. Thus, it is possible to perform the determination
in the temperature protection control for the electric motor 11a.
Thereby, the reliability of the temperature protection control of
the electric motor 11a is raised.
[0117] Here, the control process in the third embodiment is
applicable not only to the heat pump refrigerant cycle system
described in the second embodiment, but also to the refrigerant
cycle system described in the first embodiment.
Other Embodiments
[0118] The present invention is not limited to the above-described
embodiments, and may be modified variously as follows.
[0119] (1) In the above-described embodiments, the temperature of
the electric motor 11a of the electric compressor 11 is calculated
and detected, using the control characteristic that associates the
temperature of the electric motor 11a with the rotational speed and
the motor current of the electric motor 11a. The present invention
is not limited to this configuration. For example, the temperature
of the electric motor 11a may be detected by a temperature sensor
for detecting intra-motor temperature of the electric motor 11a, a
temperature sensor for detecting temperature of a housing of the
electric motor 11a, etc.
[0120] (2) In the above-described embodiments, the opening degrees
of the electric expansion valves 12, 16 are directly adjusted in
the temperature protection control for the electric motor 11a of
the electric compressor 11. The present invention is not limited to
this configuration. For example, the discharge refrigerant pressure
Pd of the electric compressor 11 may be lowered by lowering the
target high pressure that is determined based on the temperature
(exterior-side refrigerant temperature) Tho of the refrigerant at
the outlet side of the exterior-side heat exchanger 13 or the
use-side heat exchanger 6, which acts as the heat-radiating heat
exchanger.
[0121] (3) In the above-described embodiments, the temperature
protection control for the electric motor 11a of the electric
compressor 11 is performed by controlling the opening degree of the
electric expansion valve 16 not to decrease when the temperature
protection for the electric motor 11a of the electric compressor 11
is necessary. Alternatively, it is also possible to raise the
rotational speed of the electric motor 13b of the cooling fan
(first electric blower) 13a in addition to the control of the
opening degree of the electric expansion valve 16.
[0122] By raising the rotational speed of the cooling fan 13a, the
temperature of the refrigerant at the outlet side of the
heat-radiating heat exchanger 6, 13 is lowered, and the target high
pressure is lowered. Thereby, the pressure (discharge refrigerant
pressure Pd) of the refrigerant at the outlet side of the electric
compressor 11 is lowered, and the temperature rise of the electric
motor 11a is avoided.
[0123] (4) Moreover, it is also possible to lower the rotational
speed of the electric motor 4a of the electric blower (second
electric blower) 4 when the temperature protection for the electric
motor 11a of the electric compressor 11 is necessary.
[0124] By lowering the rotational speed of the electric blower 4,
the cooling capacity of the evaporator 5 is raised, and the degree
of superheat of the refrigerant at the suction side of the electric
compressor 11 is lowered. Thereby, the pressure (suction
refrigerant pressure Ps) of the refrigerant at the suction side of
the electric compressor 11 is lowered, and the temperature rise of
the electric motor 11a is avoided.
[0125] (5) Further, the interior/exterior air switching door 3c may
be switched to the interior air mode when the temperature
protection for the electric motor 11a of the electric compressor 11
is necessary. By switching the interior/exterior air switching door
3c to the interior air mode, the cooling capacity of the evaporator
5 is lowered, and the degree of superheat of the refrigerant at the
suction side of the electric compressor 11 is lowered. Thereby, the
pressure (suction refrigerant pressure Ps) of the refrigerant at
the suction side of the electric compressor 11 is lowered, and the
temperature rise of the electric motor 11a is avoided.
[0126] (6) In the above-described second embodiment, different
control characteristics, in which the criterion values are
different, are selected for the cooling operation mode and the
heating operation mode. The present invention is not limited to
this configuration. For example, the control characteristic for the
heating operation mode may be applied in dehumidifying operation
mode. A control characteristic for the dehumidifying operation mode
may be selected in the dehumidifying operation mode.
[0127] (7) Moreover, in the above-described second embodiment, even
in the cooling operation mode, the degree of superheat of the
refrigerant at the suction side of the electric compressor 11 is
small when the electric compressor 11 has just started. Therefore,
the same control characteristic as that for the heating operation
mode may be selected when the degree of superheat of the
refrigerant is smaller than a predetermined value, and the same
control characteristic as that for the cooling operation mode may
be selected when the degree of superheat of the refrigerant is
larger than a predetermined value.
[0128] (8) Moreover, the above-described refrigerant cycle system
10 may be applied to an ejector cycle system that is publicly known
by the documents such as JP3322263B1, which corresponds to U.S.
Pat. Nos. 6,477,857 and 6,574,987. In this case, the variable
throttle mechanism is replaced by an ejector provided with a
variable needle.
[0129] (9) In the above-described embodiments, the refrigerant
cycle system 10 according to the present invention is applied to a
vehicular air conditioning system. The present invention is not
limited to these examples. For example, the refrigerant cycle
system according to the present invention may be applied to a fixed
air conditioning system for home use or business use. Moreover, the
refrigerant cycle system may be applied not only to an air
conditioning system that can be switched between the cooling
operation mode and the heating operation mode but also to a
dedicated cooling system.
[0130] (10) Moreover, in the above-described refrigerant cycle
system 10, the kind of the refrigerant is not specified. The
refrigerant may be chlorofluorocarbons, chlorofluorocarbon
substitutes such as HC refrigerants, carbon dioxide (CO.sub.2) that
can be applied to both a supercritical vapor compression
refrigerant cycle system and a subcritical vapor compression
refrigerant cycle system, etc.
[0131] Additional advantages and modifications will readily occur
to those skilled in the art. The invention in its broader terms is
therefore not limited to the specific details, representative
apparatus, and illustrative examples shown and described.
* * * * *