U.S. patent application number 11/784453 was filed with the patent office on 2007-10-11 for compressor driving torque estimating apparatus and compressor driving source control apparatus.
This patent application is currently assigned to DENSO Corporation. Invention is credited to Shigeki Ooya.
Application Number | 20070237648 11/784453 |
Document ID | / |
Family ID | 38575488 |
Filed Date | 2007-10-11 |
United States Patent
Application |
20070237648 |
Kind Code |
A1 |
Ooya; Shigeki |
October 11, 2007 |
Compressor driving torque estimating apparatus and compressor
driving source control apparatus
Abstract
A compressor driving torque estimating apparatus estimates
driving torque of a compressor. The apparatus includes a
discharge-side detecting device, an inlet-side detecting device,
first and second calculating devices, and an estimated driving
torque determining device. The discharge-side detecting device
detects discharge-side quantity about fluid discharged from the
compressor. The inlet-side detecting device detects inlet-side
quantity about fluid drawn into the compressor. The first
calculating device calculates first estimated driving torque based
on the discharge- and inlet-side quantity. The second calculating
device calculates second estimated driving torque based on the
discharge-side quantity. The estimated driving torque determining
device chooses a smaller value between the first and second
estimated driving torque as the driving torque. A compressor
driving source control apparatus includes the apparatus. The
control apparatus controls an output of a driving source, which
provides driving force for the compressor, based on the driving
torque.
Inventors: |
Ooya; Shigeki; (Nagoya-city,
JP) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 828
BLOOMFIELD HILLS
MI
48303
US
|
Assignee: |
DENSO Corporation
Kariya-city
JP
|
Family ID: |
38575488 |
Appl. No.: |
11/784453 |
Filed: |
April 6, 2007 |
Current U.S.
Class: |
417/19 |
Current CPC
Class: |
B60H 2001/325 20130101;
F04B 2205/01 20130101; F04B 2205/05 20130101; B60H 2001/3238
20130101; B60H 1/3216 20130101; F04B 2201/1202 20130101; F04B 51/00
20130101 |
Class at
Publication: |
417/019 |
International
Class: |
F04B 49/00 20060101
F04B049/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 10, 2006 |
JP |
2006-107162 |
Claims
1. A compressor driving torque estimating apparatus for estimating
driving torque of a variable displacement compressor, discharge
volume of fluid of which is variable, the apparatus comprising: a
discharge side detecting means for detecting discharge side
physical quantity about fluid discharged from the variable
displacement compressor; an inlet side detecting means for
detecting inlet side physical quantity about fluid drawn into the
variable displacement compressor; a first estimated driving torque
calculating means for calculating first estimated driving torque of
the variable displacement compressor based on the discharge side
physical quantity and the inlet side physical quantity; a second
estimated driving torque calculating means for calculating second
estimated driving torque of the variable displacement compressor
based on the discharge side physical quantity; and an estimated
driving torque determining means for choosing a smaller value
between the first estimated driving torque and the second estimated
driving torque as the driving torque.
2. The compressor driving torque estimating apparatus according to
claim 1, wherein: the first estimated driving torque calculating
means determines an estimated response time from a time when the
variable displacement compressor starts compression until the
driving torque starts increasing; and the first estimated driving
torque calculating means sets the first estimated driving torque at
0 (zero) Nm when an elapsed time from the time when the variable
displacement compressor starts the compression is shorter than the
estimated response time, and calculates the first estimated driving
torque such that the first estimated driving torque increases
gradually as the elapsed time increases, when the elapsed time is
equal to or longer than the estimated response time.
3. The compressor driving torque estimating apparatus according to
claim 1, wherein: the variable displacement compressor varies the
discharge volume based on an external electrical control signal;
and the discharge side physical quantity is the control signal.
4. A compressor driving source control apparatus comprising the
compressor driving torque estimating apparatus recited in claim 1,
wherein the compressor driving source control apparatus controls an
output of a driving source, which provides driving force for the
variable displacement compressor, based on the driving torque
estimated by the compressor driving torque estimating
apparatus.
5. The compressor driving source control apparatus according to
claim 4, wherein: the variable displacement compressor is installed
in an air conditioner for a vehicle; and the driving source is an
engine of the vehicle.
6. The compressor driving torque estimating apparatus according to
claim 2, wherein the first estimated driving torque calculating
means determines the estimated response time based on the discharge
side physical quantity and the inlet side physical quantity at the
time when the variable displacement compressor starts the
compression.
7. The compressor driving torque estimating apparatus according to
claim 2, wherein the first estimated driving torque calculating
means determines an increase rate, at which the first estimated
driving torque is gradually increased, based on the discharge side
physical quantity and the inlet side physical quantity at the time
when the variable displacement compressor starts the
compression.
8. The compressor driving torque estimating apparatus according to
claim 2, wherein the estimated driving torque determining means
chooses the first estimated driving torque as the driving torque in
priority to the second estimated driving torque, when the elapsed
time is shorter than a predetermined reference time.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is based on and incorporates herein by
reference Japanese Patent Application No. 2006-107162 filed on Apr.
10, 2006.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a compressor driving torque
estimating apparatus and a compressor driving source control
apparatus.
[0004] 2. Description of Related Art
[0005] A variable displacement compressor, which obtains driving
force from a vehicle engine, is conventionally employed as a
refrigerant compressor of an air conditioner for a vehicle. In such
a vehicle, generally by estimating driving torque of the compressor
and controlling an engine output based on the estimated driving
torque, an engine rotational speed does not change even if the
driving torque of the compressor varies.
[0006] In JP2001-180261A (corresponding to U.S. Pat. No.
6,336,335B2, US2001008131 A1), for example, the driving torque of
the compressor is estimated based on a control signal that
electrically controls a discharge volume changing mechanism of the
variable displacement compressor externally, and output torque of
the engine is controlled in such a manner that the estimated
driving torque is added.
[0007] However, in operating the discharge volume changing
mechanism of the variable displacement compressor, a mechanical
operational delay (response lag) is caused in response to a change
in the control signal. Accordingly, as in JP2001-180261A, when the
driving torque is estimated based on the control signal, a great
difference between the estimated driving torque and actual driving
torque arises in a transient state, in which discharge volume
changes considerably (e.g., immediately after the variable
displacement compressor starts compression).
[0008] In JP2006-105030A (corresponding to US2006/0073047A1), the
present applicant proposes a compressor driving torque estimation
method, whereby smaller driving torque is chosen between first
estimated driving torque and second estimated driving torque as the
estimated driving torque. The first estimated driving torque is
calculated such that it gradually increases according to a time
that elapses after the compressor compresses refrigerant. The
second estimated driving torque is calculated based on a compressor
discharge refrigerant pressure.
[0009] According to the estimation method in JP2006-105030A, the
first estimated driving torque is calculated such that it is
smaller than the second estimated driving torque in the transient
state immediately after the compressor starts compression.
Consequently, the first estimated driving torque that gradually
increases according to the elapsed time is adopted as the estimated
driving torque. As a result, the great difference between the
estimated driving torque and the actual driving torque in the
transient state is limited.
[0010] The first estimated driving torque can be calculated based
on the volume control signal in JP2006-105030A. However, according
to the present inventor's further examination, even though the
first estimated driving torque is calculated based on the volume
control signal, the difference between the estimated driving torque
and the actual driving torque cannot be completely prevented.
SUMMARY OF THE INVENTION
[0011] The present invention addresses the above disadvantages.
Thus, it is an objective of the present invention to limit a
difference between estimated driving torque and actual compressor
driving torque in a transient state immediately after a variable
displacement compressor starts compression.
[0012] To achieve the objective of the present invention, there is
provided a compressor driving torque estimating apparatus for
estimating driving torque of a variable displacement compressor,
discharge volume of fluid of which is variable. The apparatus
includes a discharge side detecting means, an inlet side detecting
means, a first estimated driving torque calculating means, a second
estimated driving torque calculating means, and an estimated
driving torque determining means. The discharge side detecting
means is for detecting discharge side physical quantity about fluid
discharged from the variable displacement compressor. The inlet
side detecting means is for detecting inlet side physical quantity
about fluid drawn into the variable displacement compressor. The
first estimated driving torque calculating means is for calculating
first estimated driving torque of the variable displacement
compressor based on the discharge side physical quantity and the
inlet side physical quantity. The second estimated driving torque
calculating means is for calculating second estimated driving
torque of the variable displacement compressor based on the
discharge side physical quantity. The estimated driving torque
determining means is for choosing a smaller value between the first
estimated driving torque and the second estimated driving torque as
the driving torque.
[0013] To achieve the objective of the present invention, there is
also provided a compressor driving source control apparatus
including the compressor driving torque estimating apparatus. The
compressor driving source control apparatus controls an output of a
driving source, which provides driving force for the variable
displacement compressor, based on the driving torque estimated by
the compressor driving torque estimating apparatus.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] 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:
[0015] FIG. 1 is an overall configuration diagram of an idle-speed
control apparatus according to a first embodiment of the present
invention;
[0016] FIG. 2 is a flowchart showing control of the idle-speed
control apparatus according to the first embodiment;
[0017] FIG. 3 is a flowchart showing a chief part of the control of
the idle-speed control apparatus according to the first
embodiment;
[0018] FIG. 4 is an illustrative graph showing a relationship
between estimated driving torque and actual driving torque
according to the first embodiment;
[0019] FIG. 5 is a graph showing a relationship between a discharge
refrigerant pressure and a control current; and
[0020] FIG. 6 is an illustrative graph showing variation of the
actual driving torque.
DETAILED DESCRIPTION OF THE INVENTION
[0021] The present invention is devised based on the following
experimental knowledge. In a variable displacement compressor
having the same configuration as a first embodiment (described
later), the present inventor examines variation of actual driving
torque immediately after the compressor starts compression. FIG. 6
is a graph showing results of the examination, with its horizontal
axis being an elapsed time T, and its vertical axis being the
actual driving torque of the compressor.
[0022] The results of the examination, in which a discharge
refrigerant pressure (Pd) and a suction refrigerant pressure (Ps)
at the time the compressor starts compression are varied according
to three conditions, are plotted on the graph in FIG. 6. More
specifically, the three conditions include a condition 1 (C1:
indicated by continuous line) of Pd=3.0 Mpa and Ps=0.5 Mpa, a
condition 2 (C2: indicated by dashed-two dotted line) of Pd=3.0 Mpa
and Ps=0.2 Mpa, and a condition 3 (C3: indicated by dashed line) of
Pd=1.5 Mpa and Ps=0.2 Mpa.
[0023] In comparison between C1 and C2 in FIG. 6, when the suction
refrigerant pressure (Ps) is high, a response time (Tn) from the
time a variable displacement compressor (10) starts compression
until the actual driving torque of the compressor starts increasing
becomes short, even though the discharge refrigerant pressure (Pd)
is the same. Furthermore, as can be seen from FIG. 6, an increase
rate (.DELTA.Trk) of the torque per unit time after the response
time (Tn) elapses increases.
[0024] Moreover, in comparison between C2 and C3, when the
discharge refrigerant pressure (Pd) is high, the response time (Tn)
becomes long, and the increase rate (.DELTA.Trk) of the torque
decreases even though the suction refrigerant pressure (Ps) is the
same.
[0025] That is, the response time (Tn) and the increase rate
(.DELTA.Trk) of the torque in a transient state vary according to
the discharge refrigerant pressure (Pd) and the suction refrigerant
pressure (Ps) at the time the compressor starts compression.
Consequently, by estimating driving torque of a compressor in the
transient state based on the discharge refrigerant pressure (Pd)
and the suction refrigerant pressure (Ps), an accurate estimate can
be made with its difference from the actual driving torque being
restricted.
[0026] Furthermore, according to the results of the experiments
above, when a high-low pressure ratio (Pd/Ps) between the discharge
refrigerant pressure (Pd) and the suction refrigerant pressure (Ps)
at the time the compressor starts compression is small, the
response time (Tn) becomes short, and the increase rate
(.DELTA.Trk) of the torque increases. In FIG. 6, the response times
(Tn) under the conditions 1 to 3 are indicated by T1 to T3,
respectively.
[0027] In addition, symbols and numerals that appear above in
parentheses correspond to concrete measures described in the
following embodiments.
First Embodiment
[0028] A first embodiment of the present invention is described
with reference to FIGS. 1 to 4. According to the first embodiment,
the present invention is applied to an idle-speed control apparatus
for a vehicle. The vehicle of the first embodiment employs a
variable displacement compressor 10, which obtains driving force
from an engine for vehicle traveling as a refrigerant compressor of
a vehicle air conditioner. The idle-speed control apparatus
controls an engine rotational speed based on estimated driving
torque STrk (described later) of the variable displacement
compressor 10.
[0029] FIG. 1 is an overall configuration diagram of the idle-speed
control apparatus of the first embodiment. An engine (not shown)
has an inlet pipe 20, in which a throttle valve 20a is placed. The
throttle valve 20a regulates an amount of intake air into the inlet
pipe 20 according to a degree of opening when an accelerator pedal
of the vehicle is depressed. In the engine, the engine rotational
speed (output power) is regulated according to the intake air
amount and injection quantity.
[0030] The inlet pipe 20 has a by-pass line 20b, and an idle
adjusting valve 20c is placed in the by-pass line 20b. The idle
adjusting valve 20c changes a bypassed amount of an intake airflow
from an upstream side to a downstream side of the throttle valve
20a according to the degree of valve opening. An idle speed of the
engine is regulated by the bypassed amount of the intake
airflow.
[0031] The idle adjusting valve 20c includes a known linear
solenoid valve, and is electrically controlled by a driving voltage
Visc outputted from an electrical control unit (described later) to
change its degree of opening.
[0032] A refrigerating cycle Rc, which is included in the vehicle
air conditioner, is disposed in an engine room, and includes the
variable displacement compressor 10. In the refrigerating cycle Rc,
the variable displacement compressor 10 draws refrigerant on a
downstream side of an evaporator 70 (described later) via a piping
P1 to be compressed and discharged. The variable displacement
compressor 10 is driven to rotate when the driving force is
transmitted from the engine via a magnetic clutch 30 and a belt
mechanism (not shown).
[0033] Thus, in the first embodiment, a driving source, which
provides the driving force to the variable displacement compressor
10, is the engine. A known skew-plate variable displacement
compressor, which continuously takes variable control over its
discharge volume through an external control signal, is employed as
the variable displacement compressor 10. Additionally, the
discharge volume is geometric volume of a working space, in which
refrigerant is drawn and compressed, and more specifically,
cylinder volume between a top dead center and a bottom dead center
of a piston stroke.
[0034] Accordingly, by changing the discharge volume, a discharge
capacity of the variable displacement compressor 10 is regulated.
The discharge volume is changed by controlling a pressure Pc of a
skew plate room (not shown) in the variable displacement compressor
10 to change an inclination angle of a skew plate and change the
piston stroke.
[0035] The pressure Pc of the skew plate room is controlled by
changing a rate between a discharge refrigerant pressure Pd and a
suction refrigerant pressure Ps, which are led to the skew plate
room, using an electromagnetic volume control valve 10a that is
controlled by the control signal (control current: In) outputted
from a microcomputer 100 of the electrical control unit (described
later). As a result, the variable displacement compressor 10
continuously changes the discharge volume in a range of
approximately 0% to 100%.
[0036] In addition, since the variable displacement compressor 10
continuously changes the discharge volume in the range of
approximately 0% to 100%, an operation of the variable displacement
compressor 10 can be substantially stopped by decreasing the
discharge volume to around 0%. Thus, a clutchless configuration, in
which a rotational axis of the variable displacement compressor 10
is constantly coupled to the engine of the vehicle via the belt
mechanism, may be employed.
[0037] An outlet side of the variable displacement compressor 10 is
connected to an inlet side of a condenser 40 via a piping P2. The
condenser 40 is arranged between the engine and a front grille (not
shown) of the vehicle in the engine room. The condenser 40 is a
radiator that cools refrigerant by exchanging heat between
refrigerant discharged from the variable displacement compressor 10
and outer air blown by a fan 40a.
[0038] An outlet side of the condenser 40 is connected to an inlet
side of a vapor-liquid separator 50 via a piping P3. The
vapor-liquid separator 50 separates refrigerant cooled in the
condenser 40 into a vapor phase and a liquid phase. A liquid-phase
refrigerant outlet side of the vapor-liquid separator 50 is
connected to an expansion valve 60 via a piping P4. The expansion
valve 60 decompresses and expands liquid-phase refrigerant
separated in the vapor-liquid separator 50, and regulates a flow
rate of refrigerant that flows out of an outlet side of the
expansion valve 60.
[0039] More specifically, the expansion valve 60 has a temperature
sensitive tube 60a that detects temperature of refrigerant in the
piping P1. The expansion valve 60 detects a degree of superheat of
refrigerant on an inlet side of the variable displacement
compressor 10 based on temperature and pressure of refrigerant
drawn to the variable displacement compressor 10 (i.e., refrigerant
in the piping P1), and regulates its degree of opening such that
the degree of superheat coincides with a predetermined value.
[0040] A downstream side of the expansion valve 60 is connected to
the evaporator 70 via a piping P5. The evaporator 70 exchanges heat
between refrigerant decompressed and expanded by the expansion
valve 60 and air blown by a fan 70a. The evaporator 70 is a heat
exchanger, in which low-pressure refrigerant flown into the
evaporator 70 absorbs heat from the blown air to evaporate, and
thereby the blown air is cooled down.
[0041] The downstream side of the evaporator 70 is connected to the
piping P1. Refrigerant evaporated flows into the variable
displacement compressor 10 again. In this manner, refrigerant
circulates around the refrigerating cycle Rc, which includes the
variable displacement compressor 10, the condenser 40, the
vapor-liquid separator 50, the expansion valve 60, the evaporator
70, and the variable displacement compressor 10 in this order.
[0042] A general description of the electrical control unit of the
first embodiment is given. The electrical control unit includes the
known microcomputer 100 including a CPU, an ROM, an RAM, and the
like and its peripheral circuits 110, 131 to 133. The microcomputer
100 stores a control program for the air-conditioning controllers
10a, 30, 70a and the idle adjusting valve 20c in the ROM. The
microcomputer 100 performs various operations and processing based
on the control program.
[0043] Sensor detection signals are inputted into the microcomputer
100 from a group of air-conditioning sensors 121 to 125 via an A/D
converter 110, which is the peripheral circuit. As well, operation
signals from various air-conditioning operation switches SW on an
air-conditioning operation panel disposed near an instrument panel
at a front part of a vehicle compartment and a detection signal of
an engine tachometer 126, which detects the engine rotational speed
Ne, are inputted into the microcomputer 100.
[0044] More specifically, the group of air-conditioning sensors 121
to 125 are an outside air sensor 121, an inside air sensor 122, a
solar radiation sensor 123, an evaporator temperature sensor 124,
and a high-pressure pressure sensor 125. The outside air sensor 121
detects an outside air temperature Tam. The inside air sensor 122
detects an inside air temperature Tr. The solar radiation sensor
123 detects a solar radiation amount Ts, which is incoming into the
vehicle compartment. The evaporator temperature sensor 124 is
disposed at an air outlet part of the evaporator 70 and detects an
evaporator outlet air temperature Te. The high-pressure pressure
sensor 125 detects the discharge refrigerant pressure Pd of
refrigerant discharged from the variable displacement compressor
10.
[0045] In the first embodiment, the high-pressure pressure sensor
125 is "a discharge side detecting means" for detecting physical
quantity about a discharge pressure of the variable displacement
compressor 10, and the discharge refrigerant pressure Pd is a
discharge side detection value. The high-pressure pressure sensor
125 is provided generally to sense an abnormal pressure in the
refrigerating cycle Rc, and there is no need to newly provide "a
dedicated detecting means" for detecting the physical quantity
about the discharge pressure.
[0046] Furthermore, in the first embodiment, the evaporator
temperature sensor 124 is "an inlet side detecting means" for
detecting physical quantity about an inlet pressure of the variable
displacement compressor 10, and the evaporator outlet air
temperature Te is an inlet side detection value. Since the
evaporator outlet air temperature Te is approximately the same as a
refrigerant evaporation temperature in the evaporator 70, a
refrigerant evaporation pressure in the evaporator 70 (i.e., an
inlet pressure of the variable displacement compressor 10) can be
determined by the refrigerant evaporation temperature.
[0047] The various air-conditioning operation switches SW on the
air-conditioning operation panel include an air-conditioning
switch, an outlet mode switch, an automatic switch, and a
temperature setting switch. The air-conditioning switch gives a
command signal to actuate the variable displacement compressor 10.
The outlet mode switch sets an outlet mode. The automatic switch
gives a command signal for an air-conditioning automatic control
state. The temperature setting switch is "a temperature setting
means" for setting a vehicle compartment temperature.
[0048] An output side of the microcomputer 100 is connected to the
magnetic clutch 30, the fan 70a of the evaporator 70, the idle
adjusting valve 20c, and the like, via the drive circuits
(peripheral circuits) 131 to 133 for driving various actuators.
Additionally, the output side of the microcomputer 100 is connected
to the electromagnetic volume control valve 10a of the variable
displacement compressor 10. Operations of the various actuators
10a, 30, 70a, and 20c are controlled by output signals from the
microcomputer 100.
[0049] Next, control processing performed by the microcomputer 100
in the first embodiment is described with reference to flowcharts
in FIGS. 2 to 3. In a state where an ignition switch of the vehicle
engine (not shown) is turned on, and thereby electrical power is
supplied to the microcomputer 100 by a battery B, this control
routine starts in response to the operation signal from the
operation switch SW.
[0050] At step 1 (S1) in FIG. 2, a flag, a timer, and the like are
initialized. The flag includes a starting determination flag Tfig
(described later) that indicates whether the variable displacement
compressor 10 is started a short while ago, and Tflg equals 0
(zero) (Tflg=0) at S1. The timer is built into the microcomputer
100. In the first embodiment, the timer is "an elapsed time
measuring means" for measuring an elapsed time T after the variable
displacement compressor 10 starts compression.
[0051] At step 2 (S2), the operation signal from the
air-conditioning operation switch SW and the detection signals of
the group of air-conditioning sensors 121 to 125 and the engine
tachometer 126 are read.
[0052] At step 3 (S3), control states of the various actuators
(air-conditioning controllers) 10a, 30, and 70a for controlling air
conditioning are determined. More specifically, the control signal
for the magnetic clutch 30 is determined to energize the magnetic
clutch 30. Furthermore, a target outlet temperature TAO is
calculated, and a control voltage Vfan applied to an electric motor
of the fan 70a, the control current In of the electromagnetic
volume control valve 10a of the variable displacement compressor
10, and the like are determined based on the target outlet
temperature TAO.
[0053] The target outlet temperature TAO is calculated based on an
air-conditioning heat load fluctuation, the vehicle compartment
temperature (inside air temperature) Tr, and a set temperature
Tset, which is set by the temperature setting switch of the
air-conditioning operation switch SW using the following equation
(F1): TAO=Kset.times.Tset-Kr.times.Tr-Kam.times.Tam-Ks.times.Ts+C
(F1) Tr is the inside air temperature detected by the inside air
sensor 122. Tam is the outside air temperature detected by the
outside air sensor 121. Ts is the solar radiation amount detected
by the solar radiation sensor 123. Kset, Kr, Kam, and Ks are
control gains. C is a constant for correction.
[0054] At step 4 (S4), the estimated driving torque STrk of the
variable displacement compressor 10 is estimated. S4 is described
in detail using the flowchart in FIG. 3. At step 41 (S41), it is
determined whether the variable displacement compressor 10 is
started a short while ago. More specifically, when the starting
determination flag Tflg equals 0 (zero) (Tflg=0), it is determined
that the variable displacement compressor 10 is started a short
while ago, and control proceeds to step 42 (S42). When the starting
determination flag Tflg does not equal 0 (zero) (Tflg.noteq.0), it
is determined that the variable displacement compressor 10 is not
started a short while ago, and control proceeds to step 45
(S45).
[0055] At S42, based on the discharge refrigerant pressure Pd
(discharge side detection value) and the evaporator outlet air
temperature Te (inlet side detection value), which are read at S2,
an estimated response time Ter from the time the variable
displacement compressor 10 starts compression until compressor
driving torque starts increasing is determined.
[0056] More specifically, the suction refrigerant pressure Ps of
the variable displacement compressor 10 is calculated based on the
evaporator outlet air temperature Te, and a high-low pressure ratio
(Pd/Ps) of the discharge refrigerant pressure Pd to the suction
refrigerant pressure Ps is calculated. Based on the high-low
pressure ratio Pd/Ps, the estimated response time Ter is determined
by referring to a control map, which is stored in the microcomputer
100 in advance.
[0057] In the first embodiment, the map, in which the estimated
response time Ter becomes long as the high-low pressure ratio Pd/Ps
increases, is employed. Besides, the estimated response time Ter is
used for calculating first estimated driving torque as described
later.
[0058] At step 43 (S43), based on the discharge refrigerant
pressure Pd (discharge side detection value) and the evaporator
outlet air temperature Te (inlet side detection value), which are
read at S2, an increase rate .DELTA.TrkA, at which the first
estimated driving torque TrkA is linearly increased as the elapsed
time T increases, is determined. More specifically, as in the case
of the estimated response time Ter, based on the high-low pressure
ratio Pd/Ps, the increase rate .DELTA.TrkA is determined by
referring to the control map stored in the microcomputer 100 in
advance.
[0059] In the first embodiment, the map, in which the increase rate
.DELTA.TrkA decreases as the high-low pressure ratio Pd/Ps
increases, is employed. At S42, S43, as shown in FIG. 4, an
estimated line for the first estimated driving torque TrkA, with
the elapsed time T being its variable, is determined. FIG. 4 shows
variation of actual driving torque (continuous line) under
predetermined conditions, the first estimated driving torque TrkA
(dashed line), and second estimated driving torque TrkB (dashed-two
dotted line) (described later).
[0060] At step 44 (S44), control proceeds to S45 with Tflg being
one (Tflg=1). At S45, the first estimated driving torque TrkA is
calculated based on the estimated line for the first estimated
driving torque TrkA and the elapsed time T. Accordingly, as shown
in FIG. 4, the first estimated driving torque TrkA is 0 [Nm] when
the elapsed time T is smaller than the estimated response time Ter.
The first estimated driving torque TrkA gradual increases according
to the increase rate .DELTA.TrkA when the elapsed time T is equal
to or larger than the estimated response time Ter.
[0061] At step 46 (S46), based on the discharge refrigerant
pressure Pd (discharge side detection value), which is read at S2,
the second estimated driving torque TrkB is calculated. More
specifically, TrkB is calculated using the following equations (F2)
to (F4).
L=(.kappa./.kappa.-1).times.Psc.times.Qs.times.{(Pd/Psc)(.kappa..sup.-1/.-
kappa.)-1} (F2) Qs=Vc.times.Nc.times..eta.v (F3) TrkB=L/Nc (F4) The
equation (F2) is generally used for calculating power consumption L
of a compressor. .kappa. is an adiabatic exponent, Psc is a central
value (fixed value) of a pressure on a low-pressure side when the
refrigerating cycle is in normal operation, and Qs is a flow rate
of vapor-phase refrigerant on the inlet side of the compressor.
[0062] The equation (F3) is for calculating Qs. Vc is the discharge
volume, Nc is a compressor rotational speed, and .eta.v is
volumetric efficiency of the compressor. Therefore, .kappa., Psc,
and .eta.v are fixed values. Moreover, Vc is calculated based on
the control current In, which is determined at S3, and Nc is
calculated by multiplying the engine rotational speed Ne, which is
read at S2, by a pulley ratio.
[0063] Consequently, at S46, the power consumption L of the
compressor is calculated based on the discharge refrigerant
pressure Pd using the equations (F2), (F3), and then, the second
estimated driving torque TrkB is calculated using the equation
(F4). As a result, the second estimated driving torque TrkB depends
only upon variation of the discharge refrigerant pressure Pd.
[0064] Accordingly, in the first embodiment, S41 to S45 serve as "a
first estimated driving torque calculating means" for calculating
the first estimated driving torque TrkA of the variable
displacement compressor 10 based on the discharge refrigerant
pressure Pd and the suction refrigerant pressure Ps. As well, S46
serves as "a second estimated driving torque calculating means" for
calculating the second estimated driving torque TrkB of the
variable displacement compressor 10 based on the discharge
refrigerant pressure Pd.
[0065] At step 47 (S47), when TrkA is smaller than TrkB
(TrkA<TrkB), control proceeds to step 48 (S48) to set the
estimated driving torque STrk at TrkA (STrk=TrkA). When TrkA is not
smaller than TrkB, control proceeds to step 49 (S49) to set the
estimated driving torque STrk at TrkB (STrk=TrkB). That is, at S47
to S49, a smaller value is chosen between TrkA and TrkB as the
estimated driving torque STrk. Then, control proceeds to step 5
(S5) in FIG. 2.
[0066] Consequently, in the first embodiment, S47 to S49 serve as
"an estimated driving torque determining means" for choosing the
smaller value between the first estimated driving torque TrkA and
the second estimated driving torque TrkB as the estimated driving
torque STrk.
[0067] At S5, the driving voltage Visc, which is outputted to the
idle adjusting valve 20c, is determined. The driving voltage Visc
is determined such that the engine rotational speed Ne is
approximated to a predetermined target idle speed Nco (e.g., 600 to
800 rpm) when the engine is in an idle state.
[0068] More specifically, by adding an adding driving voltage
Visc2, which corresponds to the estimated driving torque STrk, to a
reference driving voltage Visc1, which is determined in advance
such that the engine rotational speed Ne coincides with the target
idle speed Nco, a driving voltage Vn may be determined.
[0069] At step 6 (S6), signals are outputted from the microcomputer
100 to the idle adjusting valve 20c and the air-conditioning
controllers 10a, 30, and 70a via the drive circuits 131 to 133 in
order to obtain a control state, which is determined at S3, S5.
Following standby during a control period .tau. and it is
determined that the control period .tau. elapses at step 7 (S7).
Then, control returns to S2.
[0070] In the first embodiment, the estimated driving torque STrk
of the variable displacement compressor 10 is estimated by the
above control. Based on the estimated driving torque STrk, by
controlling the driving voltage Visc, which is outputted from the
microcomputer 100 to the idle adjusting valve 20c, the engine
rotational speed Ne in the idle state does not fluctuate even if
the driving torque of the compressor changes.
[0071] Accordingly, the high-pressure pressure sensor 125, the
evaporator temperature sensor 124, the electrical control unit, and
S4 in the control routine serve as "a compressor driving torque
estimating apparatus", and the compressor driving torque estimating
apparatus, the idle adjusting valve 20c, the electrical control
unit, and S5, S6 in the control routine serve as "a compressor
driving source control apparatus".
[0072] Furthermore, in the first embodiment, the first estimated
driving torque calculating means (S41 to S45) determine the
estimated response time Ter and the increase rate .DELTA.TrkA to
calculate the first estimated driving torque TrkA, based on the
discharge refrigerant pressure Pd and the evaporator outlet air
temperature Te. Thus, as shown in FIG. 4, the first estimated
driving torque TrkA is accurate by restricting its difference from
the actual compressor driving torque in a transient state
immediately after the variable displacement compressor 10 starts
compression.
[0073] Then, the estimated driving torque determining means (S47 to
S49) choose the smaller value between the first estimated driving
torque TrkA and the second estimated driving torque TrkB as the
estimated driving torque STrk. Therefore, the first estimated
driving torque TrkA is chosen in the transient state immediately
after the starting of the compression. After the refrigerating
cycle Rc is stabilized, the second estimated driving torque TrkB,
which is calculated using the equations (F2) to (F4), is
chosen.
[0074] In the first embodiment, even in the transient state
immediately after the variable displacement compressor 10 starts
compression, the idle speed is controlled based on the estimated
driving torque STrk, which is accurate with its difference from the
actual driving torque limited. As a result, stability of the idle
speed can be considerably improved.
Second Embodiment
[0075] In the first embodiment, the discharge refrigerant pressure
Pd is used as the discharge side detection value. In a second
embodiment of the present invention, the control current In of the
electromagnetic volume control valve 10a of the variable
displacement compressor 10 is used as the discharge side detection
value. In addition, the other configurations are the same as the
first embodiment.
[0076] FIG. 5 is a graph showing a relationship between the
discharge refrigerant pressure Pd and the control current In with
its horizontal axis being the control current In, and its vertical
axis being the discharge refrigerant pressure Pd. Results of a
survey, in which a refrigerant discharge flow rate of the variable
displacement compressor 10 is changed into a low flow rate, an
intermediate flow rate, and a high flow rate, are plotted on the
graph. At each flow rate, FIG. 5 shows a correlation between the
control current In and the discharge refrigerant pressure Pd.
[0077] Thus, even when the control current In of the
electromagnetic volume control valve 10a is used as the discharge
side detection value, a similar effect to the first embodiment can
be produced. Furthermore, since the control current In is an
electrical signal, it can be readily detected.
Other Embodiments
[0078] The present invention is not limited to the above
embodiments, and various modifications can be made on the present
invention as below.
[0079] (1) In the above embodiments, the discharge refrigerant
pressure Pd and the control current In of the electromagnetic
volume control valve 10a are used as the discharge side detection
values. Nevertheless, the discharge side detection value is not
limited to these. For example, a compressor rotational speed under
predetermined conditions may be used.
[0080] Moreover, the discharge refrigerant pressure Pd is not
limited to a pressure of refrigerant immediately after it is
discharged from the variable displacement compressor 10.
Alternatively, a high-pressure side refrigerant pressure in a
refrigerant passage from the discharge side of the variable
displacement compressor 10 to an inlet side of the expansion valve
60 may be detected for the discharge refrigerant pressure Pd.
[0081] (2) In the above embodiments, the evaporator outlet air
temperature Te is used as the inlet side detection value. However,
the inlet side detection value is not limited to this. For example,
temperature of a heat exchanger fin of the expansion valve 60 may
be used as the inlet side detection value.
[0082] Furthermore, a low-pressure pressure sensor, which detects a
pressure of refrigerant drawn into the variable displacement
compressor 10 (i.e., refrigerant pressure in the piping P1), may be
employed as the inlet side detecting means. Then, the suction
refrigerant pressure Ps detected by the low-pressure pressure
sensor may be used as the inlet side detection value. Besides, a
low-pressure side refrigerant pressure in a refrigerant passage
from the outlet side of the expansion valve 60 to the inlet side of
the variable displacement compressor 10 may be detected as the
suction refrigerant pressure Ps.
[0083] (3) In the above embodiments, the estimated driving torque
determining means (S47 to S49) choose the smaller value between the
first estimated driving torque TrkA and the second estimated
driving torque TrkB as the estimated driving torque STrk.
Additionally, when the elapsed time T is shorter than a
predetermined fiducial time, the first estimated driving torque
TrkA may be used as the estimated driving torque STrk in priority
to the second estimated driving torque TrkB.
[0084] In such a case, regardless of the magnitude of the first
estimated driving torque TrkA and the second estimated driving
torque TrkB, the first estimated driving torque TrkA is used as the
estimated driving torque STrk when the elapsed time T is shorter
than the predetermined fiducial time. Thus, the first estimated
driving torque TrkA is reliably used as the estimated driving
torque STrk in the transient state immediately after the starting
of the compression.
[0085] (4) In the above embodiments, the estimated response time
Ter and the estimated increase rate .DELTA.TrkA are determined
based on the high-low pressure ratio Pd/Ps. However, a method of
determining the estimated response time Ter and the estimated
increase rate .DELTA.TrkA is not limited to this. For example, a
plurality of control maps that correspond to a combination between
the discharge refrigerant pressure Pd and the suction refrigerant
pressure Ps may be stored in the microcomputer 100 in advance. By
referring to these control maps, the estimated response time Ter
and the increase rate .DELTA.TrkA may be determined.
[0086] In the above embodiments, the increase rate .DELTA.TrkA is
determined based on the high-low pressure ratio Pd/Ps at the time
the variable displacement compressor 10 starts compression. In
addition, after the starting of the compression as well,
.DELTA.TrkA may be varied sequentially based on the discharge side
detection value and the inlet side detection value. By this method,
the estimated driving torque STrk can be estimated with a higher
degree of accuracy.
[0087] (5) In the above embodiments, a predetermined value is used
as the reference driving voltage Visc1 for determining the driving
voltage Visc of the idle adjusting valve 20c. Alternatively, based
on a deviation En (En=Nco-Ne) (calculated using another control
routine) between the engine rotational speed Ne and the target idle
speed Nco, the reference driving voltage Visc1 may be determined by
a feedback control method using proportional-integral control (PI
control) or the like so that the engine rotational speed Ne is
approximated to the target idle speed Nco.
[0088] Besides, in the control routine of the controlling of the
idle speed based on the estimated driving torque STrk in the above
embodiments, the above feedback control may be concurrently
performed.
[0089] (6) In the above embodiments, the electrical control unit
includes the microcomputer 100 and its peripheral circuits 110, 131
to 133, and thereby the air-conditioning controllers 10a, 30, and
70a are controlled, the estimated driving torque STrk is
determined, and the idle adjusting valve 20c is controlled by the
sole electrical control unit. Alternatively, the above control may
be performed in communication between a plurality of electrical
control units.
[0090] For example, in a commonly used vehicle, in which the
air-conditioning controllers 10a, 30, and 70a are controlled by an
air-conditioning control ECU, and the idle adjusting valve 20c is
controlled by an engine ECU, either one of the ECUs may determine
the estimated driving torque STrk.
[0091] (7) The application of the present invention is not limited
to the idle-speed control apparatus. As long as it accords with the
purpose of the invention, which is described in claims, the
application is not limited to the above embodiments, and the
present invention may be applied to a variety of uses.
[0092] For example, the present invention may be applied to a
stationary heater or cooling apparatus including the variable
displacement compressor with a stationary engine being its driving
source. Moreover, it may be applied when, in a system that has the
variable displacement compressor with an electric motor being its
driving source, an amount of electrical power supplied to the motor
is controlled based on the estimated driving torque STrk to
maintain a regular rotational speed of the electric motor.
[0093] 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.
* * * * *