Refrigeration – Automatic control – Of external fluid or means
Reexamination Certificate
2002-06-11
2004-08-24
Tanner, Harry B. (Department: 3744)
Refrigeration
Automatic control
Of external fluid or means
C062S180000, C062S201000, C062S228400
Reexamination Certificate
active
06779354
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a temperature controller for a liquid cooling system for holding, by making utilization of a refrigeration circuit, the temperature of a coolant liquid for use in devices such as a machine tool at a substantially constant value and more particularly it relates to energy-saving technology thereof.
BACKGROUND ART
Conventionally, liquid cooling systems adapted to cool a coolant liquid of a device such as a machine tool by circulation thereof have been known in the art. One such liquid cooling system is disclosed in Japanese Patent Kokai Gazette No. H02-104994. The disclosed liquid cooling system comprises: a coolant liquid circulation circuit through which the device coolant liquid is circulated by a motor-driven circulation pump; and a refrigeration circuit formed by interconnecting, in the order given, a compressor, a condenser, a pressure reducing mechanism, and an evaporator. The coolant liquid is cooled by making utilization of the evaporation of liquid refrigerant in the evaporator, and the compressor is subjected to variable displacement control by an inverter so that the temperature of the coolant liquid is held at a substantially constant value even when there occurs a change in heat generation accompanied with the operation of the device.
Apart from the above, such previously known liquid cooling systems employ a circulation pump for the circulation of a device coolant liquid. The circulation pump is a rated flow rate type and therefore discharges coolant liquid at a fixed rate, and the rated flow rate is so set as to secure a sufficient cooling capacity or the like even when the device operates at its maximum capacity. And the circulation pump is in operation all the time. In other words, the circulation pump is continuously operated and discharges a fixed amount of coolant liquid, even when it is not required doing so. That is, there are operation situations in which it is sufficient for the circulation pump to deliver a minimum amount of coolant liquid required for lubrication or the like, when the amount of heat generated in the operation of the device decreases (for example, when the device is out of operation) and there is no need for the circulation pump to deliver cooled coolant liquid to the device at a rated flow rate. The circulation pump consumes energy unnecessarily, and there is room for improvement.
Further, when the compressor stops operating at the time of controlling the temperature of the coolant liquid, the inverter also becomes idle. Therefore, it is desirable that the inverter be utilized effectively.
Bearing in mind the above, the present invention was made. Accordingly, a first object of the present invention is to reduce unnecessary energy consumption by a circulation pump by providing improvements in the manner of controlling the circulation pump in a liquid cooling system comprising a coolant liquid circulation circuit through which a device coolant liquid is circulated as described above, and a refrigeration circuit through which refrigerant is circulated.
Further, a second object of the present invention is to effectively utilize an inverter which controls the operating frequency of a compressor of a liquid cooling system of the same type as described above, by providing improvements in the manner of controlling the inverter.
DISCLOSURE OF THE INVENTION
In order to achieve the first object described above, the amount of coolant liquid that a circulation pump circulates is made variable depending on the operating state or operating environmental state of a machine in the present invention.
More specifically, as shown in
FIGS. 4
,
6
,
9
, and
10
, the present invention presupposes a liquid cooling system, the liquid cooling system comprising a coolant liquid circulation circuit (
8
) in which a coolant liquid of a machine (
1
) is circulated by a circulation pump (
12
) which is operated by a motor (
11
), and a refrigeration circuit (
20
) formed by interconnecting, in the order given, a compressor (
15
), operated by a motor (
14
), for compressing gas refrigerant, a condenser (
16
) for condensing gas refrigerant, a pressure reducing mechanism (
17
) for depressurizing liquid refrigerant, and an evaporator (
18
) for cooling the coolant liquid in the coolant liquid circulation circuit (
8
) by heat exchange with refrigerant.
And, a coolant liquid circulation amount control means (
27
) is provided which varies, on the basis of an operating state or operating environmental state of the machine (
1
), the amount of coolant liquid that the circulation pump (
12
) circulates.
As a result of such arrangement, the circulation pump (
12
) is operated by the motor (
11
), thereby causing a coolant liquid for the machine (
1
) to circulate through the coolant liquid circulation circuit (
8
), and the device coolant liquid is cooled, midway along the coolant liquid circulation circuit (
8
), by heat exchange with refrigerant in the evaporator (
18
) of the refrigeration circuit (
20
). Then the amount of circulating coolant liquid in the coolant liquid circulation circuit (
8
) is changed by the coolant liquid circulation amount control means (
27
) depending on the operating state or operating environmental state of the machine (
1
). Because of this, when the machine tool (
1
) enters for example the out-of-operating state and, as a result, the amount of heat produced in the operation of the machine tool (
1
) is reduced (i.e., when there is no need to deliver to the machine tool (
1
) cooled coolant oil at a rated flow rate and it is sufficient that a minimum required amount of coolant oil for lubrication or the like is delivered to the machine tool (
1
)), it is arranged such that the amount of coolant liquid that the circulation pump (
12
) circulates is reduced. This reduces wasteful consumption of energy by the circulation pump (
12
) and energy savings are achieved.
Further, as shown in
FIG. 10
, it may be arranged such that the circulation pump (
12
) is a variable displacement pump capable of variable discharge of coolant liquid, and that the coolant liquid circulation amount control means (
27
) varies the rate of flow by controlling the discharge amount of the variable displacement pump.
Such arrangement makes it possible to vary the rate of flow of coolant liquid by controlling the amount of coolant liquid that the variable displacement pump discharges, and the coolant liquid circulation amount control means (
27
) can be embodied easily.
Further, it may be arranged such that a pole change means is provided which changes the number of poles of the motor (
11
) of the circulation pump (
12
), and that the coolant liquid circulation amount control means (
27
) varies the rate of flow by controlling the number of poles of the motor (
11
) through the pole change means.
If the pole change means performs control so that the number of poles of the motor (
11
) of the circulation pump (
12
) is reduced, then it is possible to reduce the amount of coolant liquid that the circulation pump (
12
) circulates, and the coolant liquid circulation amount control means (
27
) can be embodied.
As shown in
FIGS. 4 and 9
, it may be arranged such that an inverter (
28
,
28
P) is provided which changes the operating frequency of the motor (
11
) of the circulation pump (
12
), and that the coolant liquid circulation amount control means (
27
) varies the rate of flow by controlling the operating frequency of the motor (
11
) through the inverter (
28
,
28
P).
If the inverter (
28
,
28
P) performs control so that the operating frequency of the motor (
11
) is reduced, then it is possible to reduce the amount of coolant liquid that the circulation pump (
12
) circulates, and the coolant liquid circulation amount control means (
27
) can be embodied.
Further, as shown in
FIG. 4
, it may be arranged such that the inverter (
28
) controls the operating frequency of the motor (
14
) of the compressor (
15
), and that a switching means (
33
) is provided which switches, according to an operating state or
Daikin Industries Ltd.
Nixon & Peabody LLP
Studebaker Donald R.
Tanner Harry B.
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