U.S. patent application number 11/386641 was filed with the patent office on 2006-10-12 for constant temperature controller.
This patent application is currently assigned to ATS JAPAN Corp.. Invention is credited to Kazushige Shimizu.
Application Number | 20060225876 11/386641 |
Document ID | / |
Family ID | 37082064 |
Filed Date | 2006-10-12 |
United States Patent
Application |
20060225876 |
Kind Code |
A1 |
Shimizu; Kazushige |
October 12, 2006 |
Constant temperature controller
Abstract
A constant temperature controller inexpensive and easy to
operate, yet capable of accurately controlling the temperature with
significantly reduced heat energy consumption, is provided. An
operation mode of a cooler is switched between an idling mode and a
loaded mode, based on a difference in temperature between a first
temperature sensor and a third temperature sensor. For switching
the operation mode, cooling power of the cooler is adjusted by
changing a frequency of an inverter driving a compressor. Under the
loaded mode, the cooling power of the cooler is adjusted by an
aperture of an electronic expansion valve such that a difference
between a temperature of a second sensor and a target temperature
of a heater becomes a constant value.
Inventors: |
Shimizu; Kazushige;
(Koshigaya-shi, JP) |
Correspondence
Address: |
BROWDY AND NEIMARK, P.L.L.C.;624 NINTH STREET, NW
SUITE 300
WASHINGTON
DC
20001-5303
US
|
Assignee: |
ATS JAPAN Corp.
Koshigaya-shi
JP
|
Family ID: |
37082064 |
Appl. No.: |
11/386641 |
Filed: |
March 23, 2006 |
Current U.S.
Class: |
165/263 ;
165/65 |
Current CPC
Class: |
F25B 2700/21172
20130101; F25B 49/02 20130101; F25D 17/02 20130101; F25B 2400/0403
20130101; F25B 2600/021 20130101; F25B 2400/0409 20130101; F25B
2700/21173 20130101; Y02B 30/70 20130101; F25B 2400/24 20130101;
F25B 41/35 20210101 |
Class at
Publication: |
165/263 ;
165/065 |
International
Class: |
F25B 29/00 20060101
F25B029/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 7, 2005 |
JP |
2005-110439 |
Claims
1. A constant temperature controller that circulates a heat medium
fluid through a fluid path arranged in a loop through a cooler, a
heater and an external heat load apparatus so as to maintain the
external heat load apparatus at a predetermined constant
temperature, comprising: a cooler operation mode switch that
selects one of the cooler operation modes at least including an
idling mode of outputting a minimal cooling power to maintain the
temperature when the external heat load is off, and a loaded mode
of increasing or decreasing the cooling power according to the
external heat load, based on a difference between a heat medium
fluid temperature at an inlet port of the cooler and a heat medium
fluid temperature at an outlet port of the heater; and a cooling
power controller that adjusts the cooling power of the cooler such
that the difference between the heat medium fluid temperature at an
outlet port of the cooler and a target temperature of the heater
becomes a predetermined target difference in temperature, under the
loaded mode.
2. The constant temperature controller according to claim 1,
wherein the cooler operation mode switches a frequency of an
inverter driving a compressor incorporated in the refrigerator
cycle of the cooler, so as to switch the cooler operation mode.
3. The constant temperature controller according to claim 1,
wherein the target difference in temperature of the cooling power
controller is set such that the heat medium fluid temperature at
the outlet port of the cooler becomes lower than the target
temperature of the heater by a predetermined value.
4. The constant temperature controller according to claim 1,
wherein the cooling power controller includes an electronic
expansion valve incorporated in the refrigerator cycle of the
cooler, so as to adjust the cooling power by controlling the
aperture of the electronic expansion valve.
5. The constant temperature controller according to claim 4,
wherein the cooling power controller including the electronic
expansion valve includes a feedback control function based on the
temperature of the heat medium fluid at the outlet port of the
cooler.
6. The constant temperature controller according to claim 5,
wherein the feedback control function includes dividing the heat
medium fluid temperature at the outlet port of the cooler into a
plurality of temperature zones in advance, and adjusting the
cooling power of the cooler according to the respective temperature
zones.
7. The constant temperature controller according to claim 1,
wherein the heater includes a feedback control function based on
the temperature of the heat medium fluid at the outlet port of the
heater.
8. The constant temperature controller according to claim 7,
wherein the feedback control function includes a PID control
function.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a constant temperature
controller for maintaining the temperature of an external heat load
apparatus constant, and more particularly to a constant temperature
controller that circulates a heat medium fluid of a constant
temperature so as to maintain the temperature of the external heat
load apparatus constant, employed for a chiller incorporated in a
semiconductor manufacturing apparatus, or the like.
DESCRIPTION OF THE RELATED ART
[0002] A conventional constant temperature controller, generally
called a chiller, is designed to circulate a heat medium fluid
through a pipeline arranged in a loop through a cooler, a heater
and an external heat load apparatus, so as to once supercool the
liquid medium heated by the external heater with the cooler, and to
heat the supercooled liquid medium with the heater thus to supply
the external heat load apparatus with the liquid medium of a
predetermined temperature specified by the external heat load
apparatus.
[0003] In such controller, normally the cooler is constantly
outputting the rated cooling power irrespective of whether the
external heat load apparatus is working. This leads to continuous
consumption of a large power, especially when a refrigerator is
employed as the cooler. Therefore, JP-A 2004-169933 proposes a
constant temperature controller that can switch between an
operation mode and an energy-saving mode according to the operation
status of the external heat load apparatus.
[0004] Also, the cooler of the constant temperature controller is
usually set such that the liquid medium is cooled to the specified
temperature at the outlet port of the cooler. However, the
temperature of the liquid medium often becomes considerably higher
(overshoot) or lower (undershoot) than the specified temperature
after once reaching the specified temperature, because of slow heat
transmission of a coolant gas (such as a CFC gas) in the
refrigerator cycle of the cooler. This requires a larger capacity
of the heater, and hence a larger heater capable of controlling a
wider temperature range has to be employed.
[0005] Accordingly, JP-A 2001-153518 proposes providing a
temperature controller, outside the constant temperature controller
and close to the external heat load apparatus, for micro-adjusting
the temperature of the heat medium.
[0006] [Patented document 1] JP-A 2004-169933
[0007] [Patented document 2] JP-A 2001-153518
[0008] The JP-A 2004-169933 discloses a chiller controller that
employs a computer that pre-reads recipe information on a process
sequence of a plasma etching processor, so as to switch the chiller
to the operation mode or to the energy-saving mode, when the
etching process enters a certain duration of downtime or when the
etching process is resumed.
[0009] Such chiller controller, however, requires the computer and
associated wires and so on, for constantly monitoring the operation
status of the apparatus under the temperature control, and
transmitting the status information to the control system of the
chiller.
[0010] The JP-A 2001-153518 discloses a temperature control system
that includes a second temperature controller separated from the
chiller and located close to the processing apparatus to be
controlled, for setting the temperature at the outlet port of the
chiller and micro-adjusting the temperature of the heat medium
supplied to the processing apparatus, depending on the temperature
of the processing apparatus. Such system, however, incurs a greater
heat energy loss because of including two temperature controllers
which naturally requires two power supply systems. The system also
requires two signal line systems for operating the two controllers,
thus making the operation process more complicated.
[0011] Accordingly, it is an object of the present invention to
provide a constant temperature controller having an operation mode
switching function that enables performing the energy-saving
operation.
[0012] It is another object of the present invention to provide a
constant temperature controller inexpensive and easy to operate,
yet capable of accurately controlling the temperature with
significantly reduced heat energy consumption.
SUMMARY OF THE INVENTION
[0013] The present invention provides a constant temperature
controller that circulates a heat medium fluid through a fluid path
arranged in a loop through a cooler, a heater and an external heat
load apparatus so as to maintain the external heat load apparatus
at a predetermined constant temperature, comprising a cooler
operation mode switch that selects one of the cooler operation
modes at least including an idling mode of outputting a minimal
cooling power to maintain the temperature when the external heat
load is off, and a loaded mode of increasing or decreasing the
cooling power according to the external heat load, based on a
difference between a heat medium fluid temperature at an inlet port
of the cooler and a heat medium fluid temperature at an outlet port
of the heater; and a cooling power controller that adjusts the
cooling power of the cooler such that the difference between the
heat medium fluid temperature at an outlet port of the cooler and a
target temperature of the heater becomes a predetermined target
difference in temperature under the loaded mode.
[0014] The cooler operation mode is switched based on the
difference between the circulating heat medium fluid temperature at
the inlet port of the cooler and the circulating heat medium fluid
temperature at the outlet port of the heater. A reason of such
arrangement may be described as follows. It is impossible to
precisely foresee when the heat load that has been changed returns
from the external heat load apparatus, i.e. the object of the
temperature control. The target temperature of the heater, which is
the target temperature of the constant temperature controller, is
often changed depending on the operation status of the external
heat load apparatus. Although the target temperature of the
constant temperature controller is changed, the heat load that has
been changed may not always return from the external heat load
apparatus after the temperature of the heat medium fluid at the
outlet port of the constant temperature controller has reached the
newly set target and has been stabilized. The heat load that has
changed may return during the transition of the temperature toward
the target newly set by the constant temperature controller.
[0015] Under the conventional control system of switching the
operation mode based on the difference between the circulating
fluid temperature at the inlet port of the cooler and the target
temperature of the constant temperature controller, the heat load
that has been changed may return during the transition of the
target temperature of the constant temperature controller, i.e.
before the circulating fluid temperature at the outlet port of the
constant temperature controller reaches the newly set target, in
which case the actual temperature becomes considerably higher
(overshoot) or lower (undershoot) than the target temperature.
[0016] To avoid this, the present invention switches the operation
mode based on the difference between the circulating fluid
temperature at the inlet port of the cooler and the circulating
fluid temperature at the outlet port of the heater. Such method
enables quickly detecting the fluctuation in the difference in
temperature even during the transition of the target temperature of
the constant temperature controller, to thereby quickly react the
fluctuation of the lead load, thus allowing switching the operation
mode under a stabilized situation without overshooting or
undershooting the target temperature by far. As a result, the
operation mode can be timely switched and therefore the operation
status can be quickly stabilized.
[0017] The difference in the circulating fluid temperature varies
depending on the type or scale of the external heat load apparatus,
as well as of the constant temperature controller, but may be
usually set in a range of 1 to 5 degree centigrade. For measuring
the temperature difference, a first temperature sensor is disposed
at the inlet port of the cooler, and a third temperature sensor at
the outlet port of the heater.
[0018] The operation mode of the cooler may be switched by
switching a frequency of an inverter driving a compressor
incorporated in the refrigerator cycle of the cooler. Specifically,
the compressor is driven by a low inverter frequency in the idling
mode. Driving under a low frequency can reduce the cooling
power.
[0019] Also, driving the inverter with a low-frequency power
reduces the power consumption. In the idling mode real-time
adjustment of the cooling power is not required because the heat
load scarcely returns from the external heat load apparatus, and it
is sufficient to output a low cooling power generally constantly.
Such operation mode can be performed over the entire rated
temperature range of the constant temperature controller.
[0020] In the loaded mode, the compressor of the refrigerator cycle
is driven by a power of a high inverter frequency. Increasing the
inverter frequency can increase the cooling power. However, since
controlling the compressor by the inverter frequency does not
provide a sufficiently quick response, the inverter frequency is
fixed in the loaded mode, and an electronic expansion valve is
employed for controlling the cooling power of the cooler.
[0021] Another reason of fixing the inverter frequency of the
refrigerator in the loaded mode is that the coolant gas (such as a
CFC gas becomes temporarily unstable because of a fluctuation in
the inverter frequency, thus degrading the temperature adjusting
accuracy.
[0022] Also, the fluctuating heat load returns from the external
heat load apparatus in the loaded mode, and hence the cooling power
of the cooler has to be adjusted at real time in response to the
heat load fluctuation. Accordingly, it is preferable to employ the
electronic expansion valve which can quickly react, for adjusting
the cooling power of the cooler in the loaded mode by controlling
the aperture of the valve.
[0023] The aperture of the electronic expansion valve is to be
adjusted such that the difference between the circulating fluid
temperature at the outlet port of the cooler and the target
temperature of the heater becomes a predetermined value
(hereinafter, "target difference in temperature"). It is preferable
to set the target difference in temperature so as to secure a
heating margin of the heater, specifically such that the
circulating fluid temperature at the outlet port of the cooler
becomes several degree centigrade lower, for example 1 to 5 degree
centigrade lower than the target temperature of the heater. For
such purpose, a second temperature sensor is provided for measuring
the circulating fluid temperature at the outlet port of the
cooler.
[0024] The aperture of the electronic expansion valve may be
controlled based on feedback of the circulating fluid temperature
at the outlet port of the cooler.
[0025] For performing the feedback control, the circulating fluid
temperature at the outlet port of the cooler is divided in advance
into a plurality of temperature zones, so as to adjust the cooling
power of the cooler according to the respective temperature
zones.
[0026] Hereinafter, the temperature zone of a certain range around
a temperature lower than the target temperature of the heater by a
predetermined value will be referred to as a target temperature
zone, and a zone higher than the target temperature zone as a
higher temperature zone, while a zone lower than the target
temperature as a lower temperature zone.
[0027] When the circulating fluid temperature at the outlet port of
the cooler is within the target temperature zone, the aperture of
the electronic expansion valve is maintained as it is. When the
circulating fluid moves up to the higher temperature zone, which is
higher than the target temperature zone, the aperture of the
electronic expansion valve is gradually increased so as to increase
the cooling power. On the other hand, when the circulating fluid
moves down to the lower temperature zone, which is lower than the
target temperature zone, the aperture of the electronic expansion
valve is gradually reduced so as to decrease the cooling power.
Setting thus a certain range in the temperature based on which the
valve aperture is controlled allows improving the stability of the
circulating fluid temperature.
[0028] More specifically, when the circulating fluid of +30 degree
centigrade is to be supplied to the external heat load apparatus,
the cooler is set so as to maintain the target difference in
temperature that is 1 to 5 degree centigrade lower than +30 degree
centigrade, at the outlet port. When the target difference in
temperature is set as 2 degree centigrade for example, the target
temperature becomes +28 degree centigrade. In this case, the
expansion valve opens or closes even when the circulating fluid
temperature is only 0.1 degree centigrade higher or lower than +28
degree centigrade, which leads to lack of stability in the
circulating fluid temperature. Accordingly, granting a certain
range to the target temperature, such as +28.5 to +27.5 degree
centigrade, the aperture of the expansion valve is not changed
within this range, and the circulating fluid temperature can be
stabilized.
[0029] The target temperature of the heater means the target
temperature of the constant temperature controller, which may be
changed depending on the type or operation status of the external
heat load apparatus.
[0030] The heater also has the feedback control function so as to
adjust the circulating fluid temperature at the target temperature
at the outlet port thereof.
[0031] To perform the feedback control, a PID control function may
be introduced. Employing the PID control function enables
controlling the circulating fluid temperature at the outlet port of
the constant temperature controller extremely accurately.
[0032] The operation modes of the cooler may further include a
temperature increasing mode and a temperature decreasing mode. The
temperature increasing mode is performed when the target
temperature of the constant temperature controller is changed to a
higher temperature, so as to increase the temperature up to the
newly set higher target temperature. In this mode, the cooling
power is reduced to a minimal level, and a maximal heating power is
output thus to increase the temperature as quickly as possible.
[0033] The temperature decreasing mode is performed when the target
temperature of the constant temperature controller is changed to a
lower temperature, so as to decrease the temperature down to the
newly set lower target temperature. In this mode, the cooling power
is increased and the heating power is turned off thus to decrease
the temperature as quickly as possible. The switching between the
temperature increasing mode and the temperature decreasing mode is
automatically or semi-automatically performed when the target
temperature of the constant temperature controller is changed.
[0034] The constant temperature controller according to the present
invention includes the cooler operation mode switch that selects
the cooler operation mode based on the difference between the
circulating fluid temperature at the inlet port of the cooler and
the circulating fluid temperature at the outlet port of the heater.
Such configuration allows quickly detecting the fluctuation in the
difference in temperature of the constant temperature controller
even during the transition of the target temperature, to thereby
quickly react the fluctuation of the lead load, thus allowing
switching the operation mode under a stabilized situation without
overshooting or undershooting the target temperature by far. As a
result, the operation mode can be timely switched and therefore the
operation status can be quickly stabilized.
[0035] The constant temperature controller according to the present
invention includes the cooling power controller that adjusts the
cooling power by the inverter frequency that drives the compressor
in the refrigerator cycle, and is therefore capable of switching
the cooler operation mode between the idling mode and the loaded
mode, and thereby performing the energy-saving operation.
[0036] The constant temperature controller according to the present
invention includes the cooling power controller that adjusts the
cooling power by controlling the aperture of the electronic
expansion valve provided in the refrigerator cycle, which enables
quickly changing the temperature under the loaded mode, as well as
performing extremely accurate temperature control of the
cooler.
[0037] The constant temperature controller according to the present
invention includes the cooling power controller that adjusts the
cooling power of the cooler such that the difference between the
circulating fluid temperature at the outlet port of the cooler and
the target temperature of the heater becomes a predetermined target
difference in temperature. Such configuration enables maintaining
the temperature of the circulating fluid flowing into the heater at
a generally constant level, and setting the target difference in
temperature in a small range can reduce the influence of the
fluctuation of the heat load returning from the external heat load
apparatus, which permits selecting a heater of a quite small
output, such as an electric heater, yet controlling the circulating
fluid temperature flowing out of the heater, quite accurately and
at real time.
[0038] The constant temperature controller according to the present
invention includes the temperature control function of dividing the
temperature range of the circulating fluid at the outlet port of
the cooler into a plurality of predetermined temperature zones, and
utilizing the electronic expansion valve that controls the cooling
power of the cooler according to the respective temperature zones.
Such method grants a reasonable margin to the temperature based on
which the aperture of the electronic expansion valve is to be
controlled, thereby improving the stability of the temperature.
[0039] The constant temperature controller according to the present
invention employs the heater with the PID feedback control
function, which allows employing a small-sized electric heater thus
to perform the energy-saving operation, as well as accurately
controlling the temperature of the circulating fluid supplied to
the external heat load apparatus.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] FIG. 1 is a block diagram schematically showing a
configuration of a constant temperature controller according to the
present invention;
[0041] FIG. 2 is a circuit diagram of the constant temperature
controller according to the present invention;
[0042] FIG. 3 is a circuit diagram of a control system of the
constant temperature controller according to the present
invention;
[0043] FIG. 4 is a flowchart showing a controlling method of the
constant temperature controller according to the present
invention;
[0044] FIG. 5 is a block diagram for explaining an operation of the
constant temperature controller according to the present invention
under an idling mode;
[0045] FIG. 6 is a block diagram for explaining an operation of the
constant temperature controller according to the present invention
under a loaded mode (under a large heat load); and
[0046] FIG. 6 is a block diagram for explaining an operation of the
constant temperature controller according to the present invention
under a loaded mode (under a small heat load).
DETAILED DESCRIPTION OF THE INVENTION
[0047] Exemplary embodiments of the present invention will be
described hereunder, referring to the accompanying drawings.
First Embodiment
[0048] FIG. 1 is a block diagram schematically showing a
configuration of a constant temperature controller, in which a
portion enclosed by broken lines constitutes the constant
temperature controller 1. The constant temperature controller 1
includes a cooler 2 and a heater 4. Numeral 5 designates an
external heat load apparatus to be maintained at a constant
temperature, such as an etching apparatus for semiconductor wafers,
connected to the constant temperature controller via a pipeline 6
for a circulating fluid so as to constitute a closed loop.
[0049] In the pipeline 6, water is sealed in to serve as a heat
medium. To the pipeline 6, temperature sensors for measuring the
temperature of the heat medium are attached at some points. 41
designates a first temperature sensor that measures the circulating
fluid temperature at the inlet port of the cooler, i.e. the
temperature of the circulating fluid returning from the external
heat load; 42 a second temperature sensor that measures the
circulating fluid temperature at the outlet port of the cooler; and
43 a third temperature sensor that measures the circulating fluid
temperature at the outlet port of the heater.
[0050] FIG. 2 is a circuit diagram showing a configuration of the
constant temperature controller, in which a portion enclosed by
broken lines corresponds to the constant temperature controller 1
including the cooler 2 and the heater 4 enclosed by dash-dot lines.
The constant temperature controller is connected to the external
heat load via the pipeline 6. Accordingly, a circulating fluid
inlet port 64 and a circulating fluid outlet port 65 are
provided.
[0051] The cooler 2 includes a compressor 21, a condenser 22, and a
heat exchanger 26 connected via a coolant circuit 7 so as to
constitute a refrigerator cycle. The coolant circuit 7 includes a
first electronic expansion valve 23, a second electronic expansion
valve 24, a third electronic expansion valve 25, a separator 27 and
so forth. The condenser 22 serves to cool the coolant in the
coolant circuit 7 with cooling water in a cooling water circuit 8,
to thereby liquidize the coolant.
[0052] In FIG. 2, numeral 70 designates a drier (D: a filter
including a drying agent to remove moisture from the coolant gas),
71 a strainer (a mesh-type filter for the coolant gas), 72 a sight
glass (SG: a window for confirming therethrough the liquidizing
status of the coolant gas), 73 a pressure sensor (for detecting
higher-pressure side coolant gas pressure), 74 a lower-pressure
side service valve (an access point utilized for sealing the
coolant gas or maintenance work), 75 a pressure sensor (for
detecting lower-pressure side coolant gas pressure) 76 a
higher-pressure side service valve (an access point utilized for
sealing the coolant gas or maintenance work), 77 a temperature
sensor (a fourth sensor that measures the temperature of the
coolant gas discharged from the refrigerator), 78 a hot gas bypass
circuit (for utilizing compression heat of the coolant gas), 79 an
injection circuit (for lowering the temperature of the coolant gas
aspirated by the refrigerator to thereby protect the refrigerator),
81 an inlet port of the cooling water, and 82 an outlet port of the
cooling water.
[0053] The coolant compressed by the compressor 21 is forwarded to
the condenser 22 to be cooled by the cooling water flowing through
the cooling water circuit 8, thus to be liquidized. The liquidized
coolant is adiabatically expanded by the first electronic expansion
valve 23 and quickly loses the temperature. The coolant with the
dropped temperature exchanges heat with the circulating fluid at
the heat exchanger 26, to thereby cool the circulating fluid to the
desired temperature. The coolant which has thus gained temperature
is vaporized by a separator 30, and introduced into the compressor
again.
[0054] The electronic expansion valve 23 mainly serves to control
the cooling power of the cooler 2. The second electronic expansion
valve 24 serves to protect the compressor 21, and the third
electronic expansion valve 25 to auxiliarily adjust the cooling
power of the cooler 2. The circuit including the electronic
expansion valve 25 is referred to as the hot gas bypass circuit,
which introduces the coolant gas compressed by the refrigerator and
hence having compression heat directly into the heat exchanger 26
instead of cooling the gas in the condenser 22, for exchanging the
heat thus to collect heating energy, for adjusting the cooling
power when the cooling power has temporarily become excessively
large.
[0055] The aperture of the electronic expansion valves is adjusted
by stepping motors 27, 28, 29.
[0056] The heater 4 serves to heat the circulating fluid, which has
been supercooled at the heat exchanger 26 in the cooler 2 upon
returning from the external heat load apparatus though a return
pipeline 61, up to a target temperature. The circulating fluid
heated up to the target temperature is forwarded by the pressure of
a pump 66, to be supplied to the external heat load apparatus via a
feed pipeline 63.
[0057] FIG. 3 is a circuit diagram of a controller 11 that controls
the cooler 2 and the heater 4. The controller 11 switches a
frequency control signal of an inverter 13 that drives the
compressor 21 of the cooler 2, based on a difference in temperature
between the circulating fluid returning from the external heat load
apparatus measured by the first temperature sensor 41 and the
circulating fluid forwarded from the heater 4 measured by the third
temperature sensor 43, to thereby switch the operation mode of the
cooler 2. Here, numeral 12 designates a display/input panel.
[0058] When the temperatures measured by the first temperature
sensor 41 and the third temperature sensor 43 are barely different,
i.e. when the external heat load apparatus is off, the controller
selects an idling mode, in which the frequency of the inverter 13
is lowered thus to drive the compressor 21 of the refrigerator
cycle at a lower inverter frequency. Driving the inverter at a
lower frequency reduces the power consumption of the inverter.
Concurrently the controller reduces the aperture of the first
electronic expansion valve 23, to thereby reduce the cold energy
supplied to the heat exchanger to a minimal level that can maintain
the target temperature of the constant temperature controller.
[0059] When the difference in temperature between the first
temperature sensor 41 and the third temperature sensor 43 exceeds a
predetermined threshold value, i.e. when the external heat load
apparatus resumes the operation, the controller 11 selects a loaded
mode, in which the compressor 21 of the refrigerator cycle is
driven at a higher inverter frequency so as to increase the cooling
power. Concurrently the controller 11 transmits a control signal to
the stepping motor 27 so as to increase the aperture of the first
electronic expansion valve 23 thus to increase the cooling power of
the cooler 2, and supplies the necessary cold energy to the heat
exchanger 26.
[0060] In the loaded mode, however, the external heat load is not
constant, and hence the cooling power has to be controlled
according to the external heat load. For performing such control,
the aperture of the electronic expansion valve is adjusted such
that a difference between the temperature detected by the second
temperature sensor 42 and the target temperature of the heater 4
constantly remains the same. Here, it suffices that the difference
in temperature can secure a heating margin for an electric heater
44 of the heater 4.
[0061] Maintaining the difference between the circulating fluid
temperature at the outlet port of the cooler 2 and the target
temperature of the heater 4 at a constant level leads to
maintaining the load applied to the heater 4 at a constant level.
Applying a constant load makes it easier to control the temperature
with the heater 4, resultantly enabling accurately controlling the
circulating fluid temperature flowing out of the heater 4. Also,
setting the temperature difference in a narrower range can reduce
the heating output of the heater 4.
[0062] The electric heater 44 is subjected to a PID control, so
that the target temperature of the heater 4 and the circulating
fluid temperature detected by the third temperature sensor 43
becomes the same.
[0063] The target temperature of the heater may be changed
depending on a type or operation status of the external heat load
apparatus.
[0064] The circulating pump 66 is located on an upstream side of
the third temperature sensor 43. This is because the work heat of
the pump 66 can serve as the heating source in addition to the
heater 4, which leads to reduction of the power consumption, and
also to more accurate measurement of the temperature of the
circulating fluid supplied to the external heat load apparatus.
[0065] Referring now to FIG. 4, descriptions will be given
hereunder on the operation mode switching function of the constant
temperature controller according to the present invention, and the
control method of the cooling power of the cooler 2 under each
operation mode.
[0066] To start with, the target temperature SV of the constant
temperature controller is input, and the temperature TS1 of the
first temperature sensor 41, the temperature TS2 of the second
temperature sensor 42, and the temperature TS3 of the third
temperature sensor 43 are read in at the step 91.
[0067] At the step 92, the value of TS3-TS1 is compared with the
target difference in temperature, and when the former is smaller
the process advances to the step 93 of the idling mode. If the
former is greater, the process advances to the step 95 of the
loaded mode. At the step 93, the frequency of the inverter driving
the compressor 21 is lowered to decrease the cooling power of the
cooler 2. At the step 94, the aperture of the electronic expansion
valve 27 is adjusted for the idling mode. At the step 95 under the
loaded mode, the inverter frequency is increased. At the step 96,
the value obtained from (target temperature SV-temperature TS2 of
the second temperature sensor) and the target difference in
temperature are compared, and if the former is smaller the process
advances to the step 97, where the aperture of the electronic
expansion valve ELV1 is reduced.
[0068] If the former is greater, the process advances to the step
98, where the aperture of the electronic expansion valve ELV1 is
increased. At the step 99, the heater 4 is subjected to the PID
control both under the idling mode and the loaded mode, such that
the circulating fluid temperature at the outlet port of the heater
reaches the target temperature.
[0069] The following passages describe specific examples of the
operation of constant temperature controller according to the
present invention.
[0070] The target difference in temperature A represents the
difference between the temperature measured by the first
temperature sensor 41 and the temperature measured by the third
temperature sensor 43, which will be set as 3 degree
centigrade.
[0071] The target difference in temperature B represents the
difference between the temperature measured by the second
temperature sensor 42 and the target temperature of the heater 4,
which will be set as -2 degree centigrade.
[0072] FIG. 5 is a block diagram showing an operation under the
idling mode with the external heat load turned off.
[0073] In the example of FIG. 5, the external heat load is 0 W, the
temperature measure by the first temperature sensor 41 is 30 degree
centigrade, the temperature measured by the second temperature
sensor 42 is 29 degree centigrade, the temperature measured by the
third temperature sensor 43 is 30 degree centigrade, the energy
consumption by the cooler is -500 W, and the energy consumption by
the heater is +500 W.
[0074] FIG. 6 is a block diagram showing an operation under the
loaded mode with a large heat load.
[0075] In the example of FIG. 6, the external heat load is +3000 W,
the temperature measure by the first temperature sensor 41 is 36
degree centigrade, the temperature measured by the second
temperature sensor 42 is 28 degree centigrade, the temperature
measured by the third temperature sensor 43 is 30 degree
centigrade, the energy consumption by the cooler is -4000 W, and
the energy consumption by the heater is +1000 W.
[0076] FIG. 7 is a block diagram showing an operation under the
loaded mode with a small heat load.
[0077] In the example of FIG. 7, the external heat load is +1500 W,
the temperature measure by the first temperature sensor 41 is 33
degree centigrade, the temperature measured by the second
temperature sensor 42 is 28 degree centigrade, the temperature
measured by the third temperature sensor 43 is 30 degree
centigrade, the energy consumption by the cooler is -2500 W, and
the energy consumption by the heater is +1000 W.
[0078] When the target difference in temperature is thus defined on
the assumption that 1 degree centigrade corresponds to an amount of
heat of 500 W and the operation is accordingly controlled, the
target difference in temperature A of 3 degree centigrade means
that the heat load of 1500 W has returned. Likewise, the target
difference in temperature B of -2 degree centigrade means that the
heat load that has returned is supercooled by the cooler by an
amount of -1000 W, and that the heater is subjected to the PID
control so as to accurately control the temperature with respect to
the amount of +1000 W.
[0079] When the target difference in temperature B is set as -1
degree centigrade, the cooler supercools the circulating fluid by
-500 W, which leads to reduced energy consumption by the heater for
executing the control.
[0080] The following passages cover a difference in thermal
efficiency between a conventional constant temperature controller
(including a large heater because of not including the cooler
operation switching function and the cooling power controlling
function) and the constant temperature controller according to the
present invention, when operated under the same condition.
[0081] In the conventional constant temperature controller, the
cooler is constantly outputting a certain cooling power
irrespective of an amount of the heat load returning from the
object of the temperature control (external heat load apparatus).
Accordingly, when the heat load returning from the object of the
temperature control is small, an excessive cooling power is
consumed and hence the heater has to output as much energy, in
order to control the circulating fluid temperature.
[0082] Further, when the external heat load is off and no heat load
is returning, the heater has to output a power substantially
equivalent to the cooling power of the cooler, for controlling the
circulating fluid temperature. This naturally requires a
large-scaled heater, thus resulting in greater energy
consumption.
[0083] Table 1 shows a comparison between the conventional constant
temperature controller and the constant temperature controller
according to the present invention, on the assumption that the
maximum cooling power of the constant temperature controller is
5000 W, and that the energy required for heating or cooling by 1000
W is indicated as 1. TABLE-US-00001 TABLE 1 Without With heat load
heat load A B A B Heat load from 0 0 3000 3000 external apparatus
Cooling power(1) 5000 1000 5000 4000 Heating power(2) 5000 1000
2000 1000 Energy 5 + 5 = 10 1 + 1 = 2 5 + 2 = 7 4 + 1 = 5
consumption(1) + (2) Remarks Idling Loaded mode mode A =
Conventional constant temperature controller B = Constant
temperature controller of the present invention
[0084] As is apparent from Table 1, the total energy consumption of
the conventional constant temperature controller with and without
the heat load is 10+7=17, while that of the present invention is
2+5=7, which corresponds to energy saving of approx. 60% with
respect to the conventional constant temperature controller.
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