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.
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.
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, 28P) 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, 28P).
If the inverter (28, 28P) 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 operating environmental state of the machine (1), the destination, to which an output from the inverter (28) is directed, between the motor (14) of the compressor (15) and the motor (11) of the circulation pump (12).
In accordance with such arrangement, the destination, to which the output from the inverter (28) is directed, is switched between the motor (14) of the compressor (15) and the motor (11) of the circulation pump (12) according to the operating state or operating environmental state of the machine (1) by the switching means (33), and for example during normal operation the output of the inverter (28) is fed to the motor (14) of the compressor (15) and the motor (11) of the circulation pump (12) is connected to a normal power supply. On the other hand, when reducing the amount of circulating coolant liquid because, for example, the machine (1) is out of operation, the output of the inverter (28) is switched to the motor (11) of the circulation pump (12) from the motor (14) of the compressor (15). As a result, the operation of the compressor (15) is stopped and the operation of the circulation pump (12) is controlled by the inverter (28). As described above, the single inverter (28) is switchably connected to the compressor (15) or to the circulation pump (12), thereby making it possible to effectively utilize the idle inverter (28) when the compressor (15) stops operating, for the operation of the oil pump (12). In comparison with such a case that outputs from two inverters are connected to the compressor (15) and to the oil pump (12), respectively, it is possible to cut costs by reducing the number of inverters (28) required. Further, it is possible to reduce power loss for inverter efficiency when the circulation pump (12) is operated in normal mode by the output of the inverter (28).
Further, it may be arranged such that the coolant liquid circulation amount control means (27) has, as the operating mode of the circulation pump (12), a rated flow rate mode in which the rate of flow of the coolant liquid is fixed and a variable flow rate mode in which the rate of flow of the coolant liquid varies, and is so configured as to allow the circulation pump (12) to switch between the flow rate modes according to an operating state or operating environmental state of the machine (1).
As a result of such arrangement, the operating mode is switched between the rated flow rate mode and the variable flow rate mode according to the operating state or operating environmental state of the machine (1). For example, during normal operation the rated flow rate mode is selected, whereby the rate of flow of coolant liquid is held constant, while, for example when the machine (1) enters the out-of-operation state, the variable flow rate mode is selected, whereby the rate of flow of coolant liquid is made variable. Accordingly, it is possible to easily change the operation mode of the circulation pump (12).
In order to achieve the second object described above, the present invention presupposes a 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); 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 an inverter (28) for controlling the operating frequency of the motor (14) of the compressor (15), wherein a switching means (33) is provided which switches the destination, to which an output from the inverter (28) is directed, between the motor (14) of the compressor (15) and any other electric operating means according to an operating state or operating environmental state of the machine (1).
As a result of such arrangement, the destination, to which the output from the inverter (28) is directed, is switched between the motor (14) of the compressor (15) and another electric operating means according to the operating state or operating environmental state of the machine (1) by the switching means (33). For example, when the compressor (15) is in operation, the output from the inverter (28) is connected to the compressor (15) so that the operating frequency of the compressor (15) is controlled in variable manner. On the other hand, when the compressor (15) is stopped, the output from the inverter (28) is connected to the electric operating means so that the frequency of a power supply to the electric operating means is controlled in variable manner. Because of this, the output from the inverter (28) is always connected to either one of the compressor (15) and the electric operating means, which makes it possible to effectively and continuously utilize the inverter (28) without stopping the operation of the inverter (28).
Preferably, the electric operating means is any one of the motor (11) of the circulation pump (12), an electric heating means (24) for electrically heating the coolant liquid circulating in the coolant liquid circulation circuit (8), and an electric air blowing means (22) for sending air to the condenser (16).
As a result of such arrangement, the electric operating means can be embodied. Especially, if it is arranged such that the electric heating means (24) is controlled by the inverter (28), this makes it possible to provide enhanced temperature control performance for coolant liquid.
It may be arranged such that the operating state or operating environmental state of the machine (1) includes at least one of a signal sent from the side of the machine (1), a liquid temperature of the coolant liquid, an operating temperature of the machine (1), and an environmental temperature of the machine (1). This arrangement makes it possible to embody examples of the operating temperature or operating environmental temperature of the machine (1).
The machine (1) is a machine tool or industrial machine using oil as a coolant liquid. As a result, the machine (1) becomes a desirable device capable of effectively providing the effects of the present invention.