Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
2002-01-14
2003-09-02
La, Anh V (Department: 2632)
Communications: electrical
Condition responsive indicating system
Specific condition
C340S501000, C340S587000, C062S196400, C062S185000, C137S487500
Reexamination Certificate
active
06614353
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention concerns an alarm or warning system for predictive maintenance, in a constant temperature liquid circulating apparatus which supplies a constant temperature cooling liquid to a load in accordance with operation of a three-way proportional valve.
2. Description of the Related Art
In various kinds of mechanical devices having constant temperature components, for example in the case of a semiconductor processing apparatus, a constant temperature cooling liquid (typically a brine solution) is continuously supplied to the constant temperature component (load) of the apparatus, wherein it is necessary to maintain a fixed temperature at the load. For this purpose, a constant temperature liquid circulating apparatus (also known as a “chiller” unit) is provided for supplying a constant temperature cooling liquid, wherein the cooling liquid which has risen in temperature by the load is circulated back to the constant temperature liquid circulating apparatus and, after being chilled by contact with a refrigerant in a heat exchanger, heat is then applied to the cooling liquid from a heater to establish a fixed temperature for the cooling liquid, and the cooling liquid is resupplied to the load in a circulatory manner.
The constant temperature liquid circulating apparatus, as understood from the description above, is not only for connection to a semiconductor processing apparatus, but may also be connected to other mechanical or electrical devices (master devices) in various industrial areas for which temperature control is required for supporting their proper operation. Therefore, breakdown or irregular operation of the constant temperature liquid circulating apparatus is directly related to stoppage of the master apparatus to which it is attached, with the possibility of creating large scale failure and loss.
More specifically, the constant temperature liquid circulating apparatus generally comprises a refrigeration circuit for cooling, in a heat exchanger, the cooling liquid that is returned from the load, and a cooling liquid circulating circuit for adjusting to a fixed temperature by applied heating the cooling liquid which has been chilled in the heat exchanger, and discharging the same, as well as other operating equipment therefor. The structural elements making up the aforementioned refrigeration circuit and cooling liquid circulating circuit, and the operating equipment therefor, are made up of a large number of parts. Even if one of the structural parts develops a fault, there is not only the possibility for breakdown or irregular operation of the constant temperature liquid circulating apparatus itself, but irregular operation or operational stoppage of the master device attached thereto may also occur, and in extreme cases, may cause a complete breakdown of the master device itself.
Accordingly, it is necessary to consider how to avoid irregular conditions in such a constant temperature liquid circulating apparatus, while at the same time is it very important to take preventative safety measures before such irregular conditions arise. However, when the constant temperature liquid circulating apparatus is used, there is a tendency, from the standpoint of rising costs, not to continuously perform careful observation thereof. Moreover, even when observations of the apparatus are regularly made, it is not possible to avoid natural wear and tear of parts which occur with the passage of time, and as a result, the useful life of the parts, and natural breakdown thereof, cannot be avoided. Thus, so called post-event processing, that is, methods for investigating the cause only after an irregular condition has occurred in the constant temperature liquid circulating apparatus, with exchange of parts and the like, have been required. With such methods, however, the time for restoration of the apparatus is lengthened, and large scale losses can occur.
As one system which attempts to deal with this type of problem, a so called “remote maintenance” system is known. This system is one in which the running state of an apparatus is observed using various kinds of sensors, and when a breakdown or irregular condition occurs, information about the state of the apparatus is transmitted to a predetermined location using telephone lines, so that service personnel can be quickly dispatched for conducting repairs. Notwithstanding, this system also involves post-event processing in which repair work is not begun until after the constant temperature liquid circulating apparatus develops a breakdown or irregular condition, wherein required repairs can be hastened only to a certain extent.
In order to address some of the problems indicated above, one approach has been proposed as described in Japanese Laid-Open Patent Publication No. 11-37516. This system attempts to minimize apparatus downtime by inferring the parts which require maintenance, and time intervals at which maintenance therefor is needed, in a constant temperature liquid circulating apparatus before the occurrence of an irregular condition.
As shown in
FIG. 5
, such a constant temperature liquid circulating apparatus is made up of a refrigeration circuit and a cooling liquid circulating circuit. The refrigeration circuit comprises a compressor
61
, a condenser
62
, a pressure-reducing valve
63
, an evaporator
64
and an accumulator
65
, all of which are connected in series. The refrigeration circuit section also includes an overheat prevention circuit
66
that directly returns the compressed refrigerant to an accumulator
65
when the evaporator
64
is subjected to a large load, including an overheat prevention valve
66
a
in the circuit
66
that opens and closes the overheat prevention circuit
66
based on readings from a temperature sensor
66
b
located on the upstream side of the accumulator
65
for detecting the temperature of the refrigerant.
On the other hand, the cooling liquid circulating circuit comprises a heat exchanger
71
, in which heat exchange occurs between the refrigerant and the cooling liquid that is circulated back after having risen in temperature by the load, a cooling liquid tank
72
having a heater
73
installed therein, and a pump
74
which supplies and circulates the cooling liquid to the load which has been heated to a fixed temperature by the heater
73
, all of which are interconnected in series.
As a result, the cooling liquid which has risen in temperature by the load is chilled by the refrigerant of the refrigeration circuit which flows through the evaporator
64
arranged in the heat exchanger
71
.
In addition, a temperature sensor
75
that detects the temperature of the cooling liquid and outputs a signal thereof is provided near an outlet of the tank
72
, and a temperature controller
76
is installed in the circulating circuit section to control the amount of power supplied to the heater
73
based on the output signal from the temperature sensor
75
. The temperature controller
76
compares the temperature detected by the temperature sensor
75
with a set temperature for the cooling liquid in order to control the amount of power supplied to the heater
73
, i.e., the amount of heat provided in the tank
72
.
Such a constant temperature liquid circulating apparatus includes a predictive maintenance system which comprises additional sensors for continuously monitoring various condition amounts, the sensors being provided at respective components of the apparatus. From the condition amounts of the apparatus which are obtained as outputs of the sensors, internal components and parts requiring maintenance, and maintenance time intervals therefor, are inferred. Further, a warning means
81
is also provided for issuing a warning when a warning condition exists, but before a serious irregular condition or breakdown actually takes place.
More specifically, in this predictive maintenance system, as sensors for continuously monitoring various types of conditions, sensors for detecting changes in condition amounts incl
Guss Paul A.
La Anh V
SMC Kabushiki Kaisha
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