U.S. patent application number 11/483672 was filed with the patent office on 2007-01-18 for variable capacity compressor control apparatus for vehicle.
This patent application is currently assigned to Calsonic Kansei Corporation. Invention is credited to Hiroyuki Makishima.
Application Number | 20070012056 11/483672 |
Document ID | / |
Family ID | 37575854 |
Filed Date | 2007-01-18 |
United States Patent
Application |
20070012056 |
Kind Code |
A1 |
Makishima; Hiroyuki |
January 18, 2007 |
Variable capacity compressor control apparatus for vehicle
Abstract
A variable capacity compressor control apparatus includes a
variable capacity compressor equipped with a control valve, a valve
controller connected to the control valve to determine its
opening/closing duty ratio and output a compression-ratio control
signal for driving the control valve with the opening/closing duty
ratio determined, a flow meter arranged in a refrigerant pipe
connected to the variable capacity compressor to detect a flow rate
of the refrigerant for the air conditioner flowing into the
variable capacity compressor, a signal processing unit connected to
the flow meter to generate a flow-rate control signal based on the
present flow rate of the refrigerant detected by the flow meter,
the signal processing unit inputting the compression-ratio control
signal outputted from the valve controller to generate a valve
control signal formed by the flow-rate control signal and the
compression-ratio control signal to the control valve, and an
outside control unit configured to input a driving condition of the
vehicle and output a demand of reducing a driving torque of the
variable capacity compressor to the signal processing unit when the
present driving condition satisfies a predetermined condition.
Inventors: |
Makishima; Hiroyuki;
(Tochigi, JP) |
Correspondence
Address: |
FOLEY AND LARDNER LLP;SUITE 500
3000 K STREET NW
WASHINGTON
DC
20007
US
|
Assignee: |
Calsonic Kansei Corporation
|
Family ID: |
37575854 |
Appl. No.: |
11/483672 |
Filed: |
July 11, 2006 |
Current U.S.
Class: |
62/228.1 |
Current CPC
Class: |
F04B 2027/1859 20130101;
F25B 2700/21175 20130101; F04B 2027/1827 20130101; F25B 2700/135
20130101; F04B 2027/1854 20130101; F25B 2600/023 20130101; F25B
2700/2104 20130101; F25B 49/022 20130101; F04B 27/1804 20130101;
F25B 2700/2106 20130101; F04B 2205/09 20130101 |
Class at
Publication: |
062/228.1 |
International
Class: |
F25B 49/00 20060101
F25B049/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 15, 2005 |
JP |
P2005-207872 |
Claims
1. A variable capacity compressor control apparatus for a vehicle,
comprising: a variable capacity compressor equipped with a control
valve capable of changing a discharge volume of a refrigerant for
an air conditioner therefrom; a valve control unit electrically
connected to the control valve to determine an opening/closing duty
ratio thereof on a basis of a preset in-cabin target temperature
and various air conditioning parameters and output a
compression-ratio control signal for driving the control valve with
the opening/closing duty ratio determined; a flow meter arranged in
a refrigerant pipe connected to the variable capacity compressor to
detect a flow rate of the refrigerant for the air conditioner
flowing into the variable capacity compressor; a signal processing
unit electrically connected to the flow meter and the valve control
unit to generate a flow-rate control signal based on the present
flow rate of the refrigerant detected by the flow meter, the signal
processing unit inputting the compression-ratio control signal
outputted from the valve control unit and outputting a valve
control signal formed by the flow-rate control signal and the
compression-ratio control signal to the control valve; and an
outside control unit electrically connected to the signal
processing unit to input a driving condition of the vehicle and
output a demand of reducing a driving torque of the variable
capacity compressor to the signal processing unit when the present
driving condition satisfies a predetermined condition, wherein when
the demand of reducing the driving torque is outputted from the
outside control unit, the signal processing unit modulates the
flow-rate control signal, thereby changing the valve control
signal.
2. The variable capacity compressor control apparatus of claim 1,
wherein the compression-ratio control signal is a signal in the
form of PWM control.
3. The variable capacity compressor control apparatus of claim 1,
wherein the control valve of the variable capacity compressor
comprises: a suction pressure detecting section communicated with a
suction chamber of the variable capacity compressor to detect a
suction-side pressure Ps of refrigerant sucked into the variable
capacity compressor; a discharge pressure detecting section
communicated with a discharge chamber of the variable capacity
compressor to detect a discharge-side pressure Pd of the
refrigerant discharged from the variable capacity compressor; a
crank-chamber communicating section communicated with a crank
chamber of the variable capacity compressor; a pressure regulating
passage formed to communicate the crank-chamber communicating
section with the discharge pressure detecting section; a valve
section having a valve body movably arranged in the pressure
regulating passage and configured to open and close the pressure
regulating passage with movements of the valve body in the pressure
regulating passage; a pressure regulating spring which is
responsive of the suction-side pressure Ps thereby to open and
close the valve section; a suction-pressure-chamber communicating
passage formed to communicate the suction pressure detecting
section with the discharge pressure detecting section; and a
driving section electrically connected to the signal processing
section to actuate the valve body of the valve section thereby
opening and closing the pressure regulating passage.
4. The variable capacity compressor control apparatus of claim 1,
wherein the outside control unit is an engine control unit for
controlling a driving source of the vehicle.
5. The variable capacity compressor control apparatus of claim 1,
wherein when the demand of reducing the driving torque is outputted
from the outside control unit, the signal processing unit modulates
the flow-rate control signal so as to reduce a voltage of the valve
control signal.
6. The variable capacity compressor control apparatus of claim 1,
wherein when the demand of reducing the driving torque is outputted
from the outside control unit, the signal processing unit modulates
the flow-rate control signal so as to reduce a pulse width of the
valve control signal.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a variable capacity
compressor control apparatus for controlling a variable capacity
compressor for a vehicle.
[0003] 2. Description of Related Art
[0004] Japanese Patent Application Laid-open Nos. 2000-317467,
2003-90284 and 2003-278660 disclose a refrigerant circulation
circuit for an automotive air conditioner commonly. In Japanese
Patent Application Laid-open No. 2000-317467, as shown in FIG. 1,
the disclosed refrigerant circulation circuit comprises a
compressor module CPM having a compressor CP and an outside
refrigerant circuit 101. The outside refrigerant circuit 101
includes a condenser 102, an expansion valve 103 and an evaporator
104. In constituents of the compressor CP, a discharge chamber 107
is communicated with the condenser 102 through a communication pipe
108. A fixed choke 108a is interposed in the communication pipe
108. This compressor CP is a type of variable capacity by
controlling pressure in a crank chamber 115. For this, the
compressor module CPM is provided with a control valve 132 for
controlling the pressure in the crank chamber 115 and a compressor
ECU (Electronic Control Unit) 177. In order to allow the compressor
CP to operate at torque corresponding to a torque setting command
from an air-conditioner ECU 180 or an engine ECU 190, the
compressor ECU 177 controls an opening degree of the control valve
132, so that the discharge flow rate of the compressor CP is
changed to a value corresponding to a desired setting torque. Thus,
since the engine ECU 190 dose not estimate a load torque on the
compressor CP but employs a value of the load torque as engine
control data, there is no need to prepare an estimation map for
load torque with respect to each type of vehicle.
[0005] In the above-mentioned conventional automotive air
conditioner, however, the driving torque of the compressor CP is
controlled by altering control signals transmitted from the
air-conditioner ECU 180 to the control valve 132 forcibly.
Therefore, there is a tendency that during the control of the
driving torque of the compressor CP, its amenity is damaged.
Additionally, due to controlling of the discharge flow only, there
is a possibility that a change in compression ratio causes abrupt
torque fluctuations.
SUMMARY OF THE INVENTION
[0006] In the above-mentioned situation, it is an object of the
present invention to provide a variable capacity compressor control
apparatus which is capable of controlling its driving torque
without producing such abrupt torque fluctuations.
[0007] In order to attain the above object, according to the first
aspect of the invention, there is provided a variable capacity
compressor control apparatus for a vehicle, comprising: a variable
capacity compressor equipped with a control valve capable of
changing a discharge volume of a refrigerant for an air conditioner
therefrom; a valve control unit electrically connected to the
control valve to determine an opening/closing duty ratio thereof on
a basis of a preset in-cabin target temperature and various air
conditioning parameters and output a compression-ratio control
signal for driving the control valve with the opening/closing duty
ratio determined; a flow meter arranged in a refrigerant pipe
connected to the variable capacity compressor to detect a flow rate
of the refrigerant for the air conditioner flowing into the
variable capacity compressor; a signal processing unit electrically
connected to the flow meter and the valve control unit to generate
a flow-rate control signal based on the present flow rate of the
refrigerant detected by the flow meter, the signal processing unit
inputting the compression-ratio control signal outputted from the
valve control unit and outputting a valve control signal formed by
the flow-rate control signal and the compression-ratio control
signal to the control valve; and an outside control unit
electrically connected to the signal processing unit to input a
driving condition of the vehicle and output a demand of reducing a
driving torque of the variable capacity compressor to the signal
processing unit when the present driving condition satisfies a
predetermined condition, wherein when the demand of reducing the
driving torque is outputted from the outside control unit, the
signal processing unit modulates the flow-rate control signal,
thereby changing the valve control signal.
[0008] According to the second aspect of the invention, the
compression-ratio control signal is a signal in the form of PWM
control.
[0009] According to the third aspect of the invention, the control
valve of the variable capacity compressor comprises: a suction
pressure detecting section communicated with a suction chamber of
the variable capacity compressor to detect a suction-side pressure
Ps of refrigerant sucked into the variable capacity compressor; a
discharge pressure detecting section communicated with a discharge
chamber of the variable capacity compressor to detect a
discharge-side pressure Pd of the refrigerant discharged from the
variable capacity compressor; a crank-chamber communicating section
communicated with a crank chamber of the variable capacity
compressor; a pressure regulating passage formed to communicate the
crank-chamber communicating section with the discharge pressure
detecting section; a valve section having a valve body movably
arranged in the pressure regulating passage and configured to open
and close the pressure regulating passage with movements of the
valve body in the pressure regulating passage; a pressure
regulating spring which is responsive of the suction-side pressure
Ps thereby to open and close the valve section; a
suction-pressure-chamber communicating passage formed to
communicate the suction pressure detecting section with the
discharge pressure detecting section; and a driving section
electrically connected to the signal processing section to actuate
the valve body of the valve section thereby opening and closing the
pressure regulating passage.
[0010] According to the fourth aspect of the invention, the outside
control unit is an engine control unit for controlling a driving
source of the vehicle.
[0011] According to the fifth aspect of the invention, when the
demand of reducing the driving torque is outputted from the outside
control unit, the signal processing unit modulates the flow-rate
control signal so as to reduce a voltage of the valve control
signal.
[0012] According to the sixth aspect of the invention, when the
demand of reducing the driving torque is outputted from the outside
control unit, the signal processing unit modulates the flow-rate
control signal so as to reduce a pulse width of the valve control
signal.
[0013] These and other objects and features of the present
invention will become more fully apparent from the following
description and appended claims taken in conjunction with the
accompany drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a schematic view showing the constitution of a
conventional apparatus;
[0015] FIG. 2 is a schematic view of an air conditioner for a
vehicle, showing one embodiment of the present invention;
[0016] FIG. 3 is a circuit diagram showing the constitution of a
flow meter on which the embodiment of the present invention is
applied;
[0017] FIG. 4 is a time chart showing the operating characteristics
of a variable capacity compressor in case of controlling its
refrigerant flow rate by reducing voltage of control signals
applied on a driving part of the compressor through flow control
signals; and
[0018] FIG. 5 is another time chart showing the operating
characteristics of the variable capacity compressor in case of
controlling its refrigerant flow rate by reducing pulse-width of
control signals applied on the driving part of the compressor
through flow control signals.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0019] Referring to the accompanying drawings, a variable capacity
compressor in accordance with an embodiment of the present
invention and a control method of controlling the variable capacity
compressor will be described below.
[0020] [Constitution of Air Conditioner for Vehicle]
[0021] Referring to FIGS. 2 and 3, the constitution of an air
conditioner for vehicle will be described in detail. FIG. 2 is a
structural schematic view of the air conditioner. FIG. 3 is a
circuit diagram showing the constitution of a flow meter.
[0022] As shown in FIG. 2, the variable capacity compressor 1 of
this embodiment constitutes an air conditioner for vehicle, sucks
in refrigerant circulating in a pipe 74 under condition of low
temperature and low pressure and compresses the refrigerant under
condition of high temperature and high pressure for discharge. The
discharged refrigerant is cooled down in a condenser 71 and
adiabatically expanded at an expansion valve 72. In succession, the
refrigerant changes its state into condition of low temperature and
low pressure on absorbing heat from air passing through an
evaporator 73 and is sucked into the variable capacity compressor 1
for next circulation in the pipe 74. Note that as a result of
drawing heat by the refrigerant in the evaporator 73, air becomes
dehumidified cool air.
[0023] The variable capacity compressor 1 is arranged outside a
vehicle cabin, for example, in an engine compartment and driven by
an engine (not shown) through a not-shown belt. The variable
capacity compressor 1 includes a suction chamber 2, a discharge
chamber 3 and a crank chamber 4. The suction chamber 2 is supplied
with gas-phase refrigerant of low temperature and low pressure
passing through the evaporator 73. The discharge chamber 3 is
compressed by a piston (not shown) to feed the gas-phase
refrigerant of high temperature and high pressure to the condenser
71. The crank chamber 4 is always communicated with the suction
chamber 2 to allow the refrigerant in the suction chamber 2 to
enter into the crank chamber 4. When the variable capacity
compressor 1 stops its operation, the pressure in the crank chamber
4 becomes equal to that in the suction chamber 2.
[0024] The crank chamber 4 is communicated with the discharge
chamber 3 through a control valve 10. When the control valve 10
opens, the crank chamber 4 is communicated with the discharge
chamber 3, allowing the refrigerant in the discharge chamber 3 to
enter into the crank chamber 4. When the control valve 10 closes,
the discharge chamber 3 and the crank chamber 4 are insulated from
each other, while the crank chamber 4 is communicated with the
suction chamber 2. Thus, as a pressure difference between the
suction chamber 2 and the crank chamber 4 is reduced, the stroke of
the piston gets longer to increase a compressive capacity of the
compressor 1.
[0025] On the other hand, when the control valve 10 opens so that
the refrigerant on the discharge side enters into the crank chamber
4, the stroke of the piston gets shorter due to a pressure
difference between the pressure in the crank chamber 4 and the
pressure in the suction chamber 2 (i.e. former pressure>latter
pressure), so that the compressive capacity of the compressor 1 is
decreased.
[0026] The control valve 10 is controlled by a valve control signal
composed of a compression-ratio control signal in the form of PWM
(Pulse Width Modulation) outputted from a valve control unit 50 and
a flow-rate control signal outputted on a basis of a detection
result of a flow meter 60. The workload of the variable capacity
compressor 1 is controlled since the control valve control unit 50
changes a duty ratio of the control valve 10 due to PWM control
method to adjust the pressure in the crank chamber 4 and change the
compressive capacity of the compressor 1.
[0027] The valve control unit 50 comprises a central processing
unit (CPU) 51 for various calculations, a memory 52 for storing
various program and data, such as read only memory (ROM) and random
access memory (RAM), an input port (I/P) 53 for inputting an
in-cabin target temperature and various air conditioning parameters
etc., an output port (O/P) 54 and a bus 55 for interconnecting
these elements with each other. The valve control unit 50 further
includes a compression-ratio signal generating circuit 56 for
generating the compression-ratio control signal. The
compression-ratio signal generating circuit 56 is driven by a drive
signal outputted from the output port 54. In connection, the
compression-ratio signal generating circuit 56 is electrically
connected to a signal processing unit 90 mentioned later.
[0028] For the air conditioning parameters, an air conditioner
switch 61, a "just behind the evaporator" temperature sensor 62, a
room-temperature sensor 63, and an atmosphere-temperature sensor
64, an insolation sensor 65 are connected to the input port 53.
Further, the in-cabin target temperature is also inputted to the
input port 53.
[0029] As shown in FIG. 2, the control valve 10 comprises a
suction-pressure detecting section 12a arranged on one side of a
body casing 11 and communicated with the suction chamber 2 to
detect a suction-side pressure, a discharge-pressure detecting
section 14a arranged at the center of the body casing 11 and
communicated with the discharge chamber 3 to detect a
discharge-side pressure and a driving section 30 arranged on the
other side of the body casing 11 to drive a valve body 21,
mainly.
[0030] Formed in the body casing 11 are a suction pressure chamber
12 that communicates with the suction chamber 2 through the
suction-pressure detecting section 12a on one side of the casing
11, a discharge pressure chamber 14 that communicates with the
discharge chamber 3 through the discharge-pressure detecting
section 14a, a pressure regulating passage 15 that communicates the
discharge pressure chamber 14 with the crank chamber 4, an
auxiliary suction pressure chamber 13 comparted from the discharge
pressure chamber 14 by a later-mentioned compartment section 22, a
driver accommodating chamber 17 where the driving section 30 is
arranged on the other side of the casing 11 and a suction pressure
chamber communicating passage 13a that communicates the suction
pressure chamber 12 with the auxiliary suction pressure chamber 13.
On a shaft 20, there are successively and integrally formed a
bellows 40, a valve body 21, the compartment section 22 and an
armature 33 in this order from one side of the shaft 20 to the
other side.
[0031] The bellows 40 is formed by a flexible bellows member 41 and
a pressure regulating spring 42 disposed in the bellow member 41 to
have a predetermined sprint constant. The bellows 40 is arranged in
the suction pressure chamber 12. The bellows 40 has its one side
formed integrally with one end of the shaft 20 and the other side
fixed on an inner wall of the suction pressure chamber 12. The
bellows 40 is sensitive against an inside pressure of the suction
pressure chamber 12. Thus, when the suction-side pressure is
smaller than a predetermined pressure, the pressure regulating
spring 42 slides the shaft 20 to open a valve part 16.
[0032] The valve body 21 constitutes the valve part 16 together
with the pressure regulating passage 15. With slide movements of
the shaft 20, the valve body 21 opens and closes the pressure
regulating passage 15.
[0033] The compartment section 22 is formed integrally with the
shaft 20 and arranged slidably. The compartment section 22 divides
off the discharge pressure chamber 14 from the auxiliary suction
pressure chamber 13 in a sealed condition while changing both
capacities of the auxiliary suction pressure chamber 13 and the
discharge pressure chamber 14 by the compartment section's
sliding.
[0034] The armature 33 is made of magnetic material and formed
integrally with the other end of the shaft 20 to constitute the
driving section 30.
[0035] The driving section 30 is arranged in the driver
accommodating chamber 17 on the other side of the body casing 11.
The driving section 30 is formed by a solenoid coil 31 arranged in
the chamber 17, a yoke 32 arranged on an inner circumference of the
solenoid coil 31 and made of magnetic material and the armature 33.
In operation, the solenoid coil 31 is excited by the valve control
signals composed of the compression-ratio control signal outputted
from the control valve control unit 50 and the flow-rate control
signal outputted on the basis of the detection result of the flow
meter 60 to absorb the armature 30. As a result, the shaft 20 is
slid to open the valve part 16.
[0036] A differential pressure setting spring 43 is interposed
between the compartment section 22 in the auxiliary suction
pressure chamber 13 and the yoke 32. When a differential pressure
between the suction pressure and the discharge pressure exceeds a
predetermined value, the shaft 20 is slid by the discharge pressure
while the differential pressure setting spring 43 is shrinking, so
that the valve part 16 is opened.
[0037] As shown in FIG. 2, the flow meter 60 of this embodiment is
interposed in a pipe 66 connecting the evaporator 73 with the
variable capacity condenser 1. The flow meter 60 is electrically
connected to the signal processing unit 90. Further, an engine
control unit 80 (as an outside control unit) is also electrically
connected to the signal processing unit 90. In operation, various
parameters representing an actual driving condition of the vehicle
are inputted to the engine control unit 80. On detection of the
driving condition of the vehicle, the engine control unit 80
controls the operation of the engine. Additionally, when the
so-detected driving condition satisfies a predetermined condition
mentioned later, the engine control unit 80 outputs a demand
(signal) of reducing a driving torque of the variable capacity
compressor to the signal processing unit 90.
[0038] As shown in FIG. 3, the flow meter 60 of this embodiment is
a so-called heater type flow meter. This flow meter 60 is equipped
with a constant temperature-difference control circuit (not shown)
for maintaining temperature of a heat wire 67 higher than
temperature of the suction refrigerant by constant temperature.
This constant temperature-difference control circuit has a function
to maintain the heat wire 67 under a constant
temperature-difference condition. That is, if the heat wire 67 is
cooled down by the suction refrigerant, the constant
temperature-difference control circuit operates to increase a
supply current for the heat wire 67 in order to maintain it under
the constant temperature-difference condition. In such a case,
simultaneously, the constant temperature-difference control circuit
outputs a voltage signal corresponding to the above supply current
for the heat wire 67, as a measured flow rate value. According to
the embodiment, since a heater type flow meter constitutes the flow
meter 60, it is possible to acquire an output corresponding to a
mass flow rate directly. Therefore, there is no influence of
refrigerant density (temperature, pressure) on measured values,
allowing dispensation with a correction. In FIG. 3, reference
numeral 68 denotes a temperature compensating resistance that is
paralleled with the heat wire 67 in order to effect the
above-mentioned function of the flow meter 60.
[0039] [Control Process for Control Valve]
[0040] (1.sup.st. Embodiment)
[0041] Referring to FIG. 4, we now describe a case of controlling
the refrigerant flow rate by reducing voltage of the control signal
for the driving section 30 through the flow rate control
signal.
[0042] First, when the air conditioner switch 61 is tuned on to
operate the air conditioner for a vehicle, the valve control unit
50 changes a duty ratio of the valve control signal for the control
valve 10 in accordance with the in-cabin target temperature and the
air conditioning parameters detected by a variety of sensors (e.g.
the "just behind the evaporator" temperature sensor 62, the
room-temperature sensor 63, the atmosphere-temperature sensor 64,
the insolation sensor 65) in order to make a room temperature
(in-cabin temperature) the target temperature as soon as
possible.
[0043] Suppose, during normal operating of the air conditioner, the
driving condition of the engine changes to a predetermined
condition where it is required to reduce a driving torque of the
compressor 1 in view of maintaining the drivability of the vehicle.
For example, there may be cited, a change from a normal traveling
to acceleration; idling; some changes in engine's combustion mode
(e.g. direct injection gasoline lo engine, lean burn engine).
[0044] In this case, the engine control unit 80 outputs a demand
(signal) of immediately reducing the present driving torque of the
variable capacity compressor 1 to the signal processing unit 90.
Inputting the above demand signal, the signal processing unit 90
modulates the flow-rate control signal and produces a valve control
signal whose voltage is lower than that of the valve control signal
in the normal driving state (See FIG. 4). Next, the so-produced
valve control signal is transmitted from the signal processing unit
90 to the driving section 30 of the valve 10 of the variable
capacity compressor 1.
[0045] In this way, when the voltage of the valve control signal
inputted to the driving section 30 is reduced, the capacity of the
variable capacity compressor 1 becomes smaller. As a result, the
flow rate of the refrigerant on circulation is reduced.
[0046] Here, it is noted that the driving torque of the variable
capacity compressor 1 is determined from a following arithmetic
expression (1) for calculating a compression energy (power) P0 and
a following relational expression (2) between the energy (power) P0
and the driving torque with the use of parameters of suction-side
pressure Ps, discharge-side pressure Pd and flow rate of the
refrigerant. Thus, by restraining a maximum flow rate of the
refrigerant, it is possible to restrain the upper limit of the
driving torque of the compressor 1. P0=(PsV/6120){n/(n-1)}{(Pd/Ps)
((n-1)/n)-1}(.eta.v/.eta.ad) (1)
[0047] where, V denotes specific volume .times.compressor discharge
rate;
[0048] n denotes polytropic index;
[0049] .eta.v denotes volumetric efficiency; and
[0050] .eta.ad denotes compression efficiency. P0=Driving
Torque.times.Number of Revolutions (2)
[0051] With the above-mentioned constitution and control method, if
the engine control unit 80 requires the variable capacity
compressor 1 to restrain the driving torque, it is carried out to
restrain the flow rate of the refrigerant so as not to exceed a
predetermined driving torque through the flow-rate control signal.
Consequently, with the restriction in the flow rate of the
refrigerant (or refrigerant flow rate) to be supplied into the
variable capacity compressor 1, it is possible to restrain the
driving torque essential to drive the compressor 1 to a value less
than the driving torque required by the engine control unit 80.
[0052] Additionally, according to the embodiment, since a parameter
to be changed in accordance with the requirement by the engine
control unit 80 is not the compression-ratio control signal but the
flow-rate control signal, it is possible to prevent occurrence of
abnormal noise because the refrigerant flow rate in the pipe does
not change abruptly.
[0053] Further, since the refrigerant flow rate is detected by the
flow meter 60 and the detection result is reflected on the
flow-rate control signal, it is possible to restrain the driving
torque less than a value required by the control unit 80 with
higher accuracy.
[0054] Meanwhile, under a situation that a signal to reduce the
driving torque is generated from the engine control unit 80 for a
long time, there arises a possibility that the valve control unit
50 judges that the cooling capability of the compressor 1 runs
short since the compressor control apparatus of the invention is
constructed so as to restrain the refrigerant flow rate without
going through the valve control unit 50. In such a case, the valve
control unit 50 would intend to increase the refrigerant flow rate.
Therefore, in order to avoid an occurrence of such a misjudgment,
it may be carried out to allow the engine control unit 80 to output
a command of fixing the control signal to the valve control unit
50.
[0055] (2.sup.nd. Embodiment)
[0056] According to the second embodiment, as shown in FIG. 5, the
flow rate of the refrigerant is restrained by reducing the pulse
width of the control signal outputted to the driving section 30
through the flow-rate control signal.
[0057] The operation of the second embodiment will be described
below.
[0058] First of all, it is noted that similarly to the first
embodiment, the valve control unit 50 changes a duty ratio of the
control signal impressed on the control valve 10 in view of
establishing a target temperature in terms of the in-cabin
temperature.
[0059] Suppose again, during normal operating of the air
conditioner, the driving condition of the engine changes to a
predetermined condition where it is required to reduce a driving
torque of the compressor 1 in view of maintaining the drivability
of the vehicle.
[0060] In this case, the engine control unit 80 outputs a demand
(signal) of immediately reducing the present driving torque of the
variable capacity compressor 1 to the signal processing unit 90.
Inputting the above demand signal, the signal processing unit 90
modulates the flow-rate control signal and produces a valve control
signal whose pulse width is smaller than that of the valve control
signal in the normal driving state (see FIG. 5). Next, the
so-produced valve control signal is transmitted 15 from the signal
processing unit 90 to the driving section 30 of the valve 10 of the
variable capacity compressor 1.
[0061] In this way, when the voltage of the valve control signal
inputted to the driving section 30 is reduced, the capacity of the
variable capacity compressor 1 becomes smaller. As a result, the
flow rate of the refrigerant on circulation is reduced.
[0062] Note that the flow-rate control signal of this embodiment is
established so as to have a frequency more than ten times of the
frequency of the valve control signal.
[0063] In this way, according to the embodiment, when the demand of
restraining the driving torque engine is generated from the engine
control unit 80, the flow rate of the refrigerant is restrained by
the flow-rate control signal in a manner that the driving torque of
the compressor 1 does not exceed a predetermined value.
Consequently, since the flow rate of the refrigerant to be supplied
into the compressor 1 is suppressed, it is possible to reduce the
driving torque necessary to drive the variable capacity compressor
1 less than a value required by the control unit 80.
[0064] Additionally, also in the second embodiment, since a
parameter to be changed in accordance with the requirement by the
engine control unit 80 is not the compression-ratio control signal
but the flow-rate control signal, it is possible to prevent
occurrence of abnormal noise because the refrigerant flow rate in
the pipe does not change abruptly.
[0065] Further, since the refrigerant flow rate is detected by the
flow meter 60 and the detection result is reflected on the
flow-rate control signal, it is possible to restrain the driving
torque less than a value required by the control unit 80 with
higher accuracy.
[0066] Meanwhile, under a situation that a signal to reduce the
driving torque is generated from the engine control unit 80 for a
long time, there arises a possibility that the valve control unit
50 judges that the cooling capability of the compressor 1 runs
short since the compressor control apparatus of the invention is
constructed so as to restrain the refrigerant flow rate without
going through the valve control unit 50. In such a case, the valve
control unit 50 would intend to increase the refrigerant flow rate.
Therefore, in order to avoid an occurrence of such a misjudgment,
it may be carried out to allow the engine control unit 80 to output
a command of fixing the control signal to the valve control unit
50.
[0067] Finally, it will be understood by those skilled in the art
that the foregoing descriptions are nothing but three embodiments
of the disclosed variable capacity compressor control apparatus and
therefore, various changes and modifications may be made within the
scope of claims.
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