JP2012047429A - Chiller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a chiller capable of extending running for any length of time by avoiding the abnormal stop of a refrigerant circuit as far as possible.SOLUTION: A chiller 1 which has a refrigerant circuit 38 for circulating a refrigerant and a brine circuit 39 for circulating brine and performing heat exchange with the refrigerant circuit 38 via cooler 7, includes: a first high pressure adjusting means for gradually reducing, when the discharge side pressure of the compressor 2 of the refrigerant circuit 38 becomes high to approach a first predetermined high pressure value for abnormal stop, the discharge capacity of the compressor 2, and performing running; a discharge refrigerant temperature adjusting means for gradually reducing, when the discharge side temperature of the compressor 2 exceeds a predetermined discharge refrigerant temperature value, the discharge capacity of the compressor 2, and performing running; and a cooler exit side refrigerant temperature brine temperature adjusting means for gradually reducing, when the refrigerant temperature of the cooler 7 exit side of the refrigerant circuit 38 is lowered to approach a first predetermined refrigerant temperature value for abnormal stop, the discharge capacity of the compressor 2, and performing running.

Description

  The present invention relates to a chiller that functions to maintain a constant temperature of, for example, industrial equipment, measuring equipment, food processing equipment, physics and chemistry equipment, and the like.

In general, a chiller is composed of a refrigerant circuit that circulates a refrigerant such as chlorofluorocarbon, and a brine circuit that circulates a brine such as water, a mixture of water and ethylene glycol, and an inorganic salt aqueous solution. Heat exchange. Mainly used for cooling of brine, but sometimes used for heating.
Such a chiller is disclosed in Patent Document 1 below, for example. A chiller described in Patent Literature 1 includes a refrigerant circuit configured by sequentially connecting a refrigerant flow path of a compressor, an electromagnetic on-off valve, a condenser, an expansion valve having a variable valve opening degree, and a cooler, and an inside of the cooler. And a brine circuit configured by sequentially connecting a brine flow path for exchanging heat with the refrigerant flow path, a heater, an external load-side heat exchanger, a tank, and a pump in an annular manner. Furthermore, by providing the first bypass circuit that connects the upstream side of the expansion valve and the downstream side of the cooler in the refrigerant circuit, the refrigerant from the condenser is sucked into the compressor without passing through the expansion valve and the cooler. In addition, by providing a control valve for adjusting the refrigerant flow rate in the first bypass circuit, it can be stably operated over a wide brine temperature range, and the brine temperature can be accurately controlled.

JP 2008-75919 A

The chiller described in Patent Document 1 can be stably operated over a wide brine temperature range as described above and can control the brine temperature with high accuracy. However, if the refrigerant pressure on the compressor discharge side in the refrigerant circuit increases excessively. The refrigerant circuit, called high cut, must be stopped abnormally. Moreover, even if the refrigerant temperature on the compressor discharge side in the refrigerant circuit rises too much, it will cause deterioration of the refrigerating machine oil used in the refrigerant circuit, which may cause an abnormal stop of the refrigerant circuit. is there. Furthermore, if the refrigerant temperature on the outlet side of the cooler in the refrigerant circuit is too low, it may be considered that the brine piping is ruptured by freezing of the brine in the cooler, thereby causing an abnormal stop of the refrigerant circuit.
However, in the chiller described in Patent Document 1 described above, the refrigerant pressure is excessively increased on the discharge side of the compressor, the refrigerant temperature is excessively increased on the discharge side of the compressor, or the refrigerant temperature is excessively decreased on the discharge side of the cooler. No measures are taken into account. Therefore, if the refrigerant pressure or refrigerant temperature on the compressor discharge side rises too much, or if the refrigerant temperature on the cooler outlet side falls too much, it should be done until the set pressure value or set temperature value for abnormal stop is reached. I had to overlook it, and I couldn't do it even if I wanted to postpone driving.

  The present invention has been made in view of the above-described conventional problems, and it is a first object of the present invention to provide a chiller capable of extending the operation as much as possible while avoiding an abnormal stop of the refrigerant circuit as much as possible. The second object is to provide a chiller capable of avoiding adverse effects on the compressor such as bearing wear and lubrication system failure.

  In order to achieve the above object, a chiller according to the present invention sequentially connects a refrigerant with a variable discharge capacity, an electromagnetic on-off valve, a condenser, an expansion valve with a variable valve opening, and a refrigerant flow path of a cooler in order. Brine circuit configured by sequentially connecting a refrigerant circuit configured in this manner and a brine channel, a tank, a pump, and an external load-side heat exchanger in an annular manner to exchange heat between the refrigerant channel in the cooler A high pressure sensor that detects the pressure on the compressor discharge side in the refrigerant circuit, a discharge refrigerant temperature sensor that detects the temperature on the compressor discharge side in the refrigerant circuit, and a cooling that detects the temperature on the cooler outlet side in the refrigerant circuit A second predetermined high pressure in which the compressor discharge side pressure detected by the high pressure sensor is lower than a first predetermined high pressure value for preset abnormal stop. Less than pressure value The compressor discharge-side temperature detected by the first high-pressure adjustment means that operates by gradually reducing the discharge capacity of the compressor until it falls below the second predetermined high-pressure value and the discharge refrigerant temperature sensor When the temperature exceeds a predetermined discharge refrigerant temperature value, a discharge refrigerant temperature adjusting means that operates by gradually decreasing the discharge capacity of the compressor until the temperature becomes equal to or lower than the predetermined discharge refrigerant temperature value, and a cooler outlet side refrigerant temperature sensor When the detected cooler outlet temperature falls below a second predetermined refrigerant temperature value that is higher than a first predetermined refrigerant temperature value that is set in advance for an abnormal stop, the temperature becomes equal to or higher than the second predetermined refrigerant temperature value. And a cooler outlet side refrigerant temperature adjusting means which operates by gradually decreasing the discharge capacity of the compressor.

  In the above configuration, the low pressure sensor for detecting the pressure on the compressor suction side in the refrigerant circuit, and the compressor suction pressure detected by the low pressure sensor is equal to or higher than a first predetermined low pressure value set in advance. And a first low pressure adjustment means that operates by lowering the valve opening of the expansion valve until it falls below the first predetermined low pressure value.

  In each of the above-described configurations, an intake refrigerant temperature sensor that detects the compressor intake side temperature in the refrigerant circuit, the compressor intake side temperature detected by the intake refrigerant temperature sensor, and the compressor intake detected by the low pressure sensor Superheat degree calculation means for calculating the degree of superheat based on the side pressure, and when the superheat degree calculated by the superheat degree calculation means falls below a predetermined superheat degree value set in advance, the superheat degree value becomes equal to or greater than the predetermined superheat degree value. And a superheat degree adjusting means that operates by lowering the valve opening degree of the expansion valve of the refrigerant circuit.

  Further, in each of the above-described configurations, a low-pressure sensor that detects the pressure on the compressor suction side in the refrigerant circuit, and the compressor suction-side pressure detected by the low-pressure sensor is a preset second predetermined low pressure value. When the pressure is lower than the value, the compressor discharge capacity is decreased by the first predetermined capacity until the second predetermined low pressure value or higher, and the detected compressor suction side pressure becomes the second predetermined low pressure value or higher. The second low-pressure adjustment means that operates until the discharge capacity of the compressor is lowered by a second predetermined capacity smaller than the first predetermined capacity and becomes equal to or higher than a third predetermined low-pressure value that is larger than the second predetermined low-pressure value. And.

  Further, in each of the above-described configurations, a bypass circuit having a capillary connected so as to branch from between the compressor and the electromagnetic on-off valve in the refrigerant circuit and join between the expansion valve and the cooler, and an electromagnetic on-off valve of the refrigerant circuit The heating operation means that closes the refrigerant and flows the refrigerant from the compressor through the bypass circuit to the cooler, and the compressor outlet pressure detected by the high pressure sensor during the heating operation by the heating operation means is preset. When it becomes equal to or higher than the second predetermined high pressure value lower than the first predetermined high pressure value for abnormal stop, the refrigerant circuit is kept until it falls below a third predetermined high pressure value set lower than the second predetermined high pressure value. And a second high-pressure adjusting means that opens and operates the electromagnetic on-off valve.

  According to the chiller according to the present invention, when the pressure on the discharge side of the compressor increases by the first high pressure adjustment means and approaches the first predetermined high pressure value for abnormal stop, the discharge of the compressor is temporarily performed. Since the operation is performed at a reduced capacity, the compressor discharge side pressure can be reduced. Thereby, it is possible to avoid the high-pressure abnormal stop of the refrigerant circuit and to extend the operation. Also, when the compressor discharge side temperature rises and exceeds the predetermined discharge refrigerant temperature value by the discharge refrigerant temperature adjusting means, the compressor discharge side temperature is temporarily lowered to operate, so the compressor discharge side temperature is reduced. The temperature can be lowered below a predetermined discharge refrigerant temperature value. Thereby, deterioration of the refrigeration oil in a refrigerant circuit can be prevented, and the early stop of a refrigerant circuit can be avoided. Then, when the cooler outlet side temperature in the refrigerant circuit decreases and approaches the first predetermined refrigerant temperature value by the cooler outlet side refrigerant temperature adjusting means, the discharge capacity of the compressor in the refrigerant circuit is temporarily reduced. Since the operation is performed, the refrigerant outlet side temperature of the refrigerant can be raised. As a result, it is possible to prevent the brine from freezing in the cooler, avoid an abnormal stop of the refrigerant circuit and the brine circuit, and extend the operation.

  In addition, when the compressor suction side pressure rises and becomes equal to or higher than the first predetermined low pressure value, the valve opening degree of the expansion valve is reduced until it falls below the first predetermined low pressure value. Therefore, adverse effects such as bearing wear on the compressor can be eliminated, and the life of the compressor can be extended.

  In the case where the superheat degree calculating means and the superheat degree adjusting means are provided, when the superheat degree at that time falls below a predetermined superheat degree value, the valve opening degree of the expansion valve of the refrigerant circuit is increased until the superheat degree value becomes equal to or higher than the predetermined superheat degree value. Since the operation is performed at a lower temperature, the degree of superheat can be increased to a value equal to or higher than a predetermined superheat value, and liquid back to the compressor can be avoided. As a result, it is possible to prevent a compressor failure.

  Further, in the apparatus including the second low-pressure pressure adjusting means, when the compressor suction side pressure of the refrigerant circuit is lower than the second predetermined low-pressure pressure value, it becomes equal to or higher than the third predetermined low-pressure pressure value which is larger than the second predetermined low-pressure pressure value. Since the operation is performed with the discharge capacity of the compressor being reduced until the pressure reaches, the compressor suction side pressure can be quickly made higher than the third predetermined low pressure value. As a result, troubles that may occur in the lubrication system of the compressor can be avoided.

  Further, in the apparatus including the heating operation means and the second high pressure adjustment means, when the compressor discharge side pressure increases during the heating operation and approaches the first predetermined high pressure value, the electromagnetic on-off valve of the refrigerant circuit temporarily Since the engine is operated with the compressor open, the compressor discharge side pressure can be lowered. Thereby, it is possible to avoid the abnormal stop of the refrigerant circuit and to extend the operation.

It is a circuit block diagram of the chiller which concerns on embodiment of this invention. It is a block block diagram which shows the control system of the said chiller. It is an external view of the chiller and a precision machine tool provided with the chiller. It is a figure which shows the time-dependent change of the inlet water temperature of the said chiller, outlet water temperature, and load. It is a figure of the graph which shows the relationship between the cold water supply temperature of the said chiller, and ambient temperature. It is a figure of the graph which shows the relationship between the load ratio of the said chiller, and a coefficient of performance. It is a figure of the flowchart which shows the control action of the chiller which concerns on Embodiment 1. FIG. It is a figure of the flowchart which shows another control action of the said chiller which concerns on Embodiment 2,3. FIG. 10 is a flowchart illustrating another control operation of the chiller according to Embodiments 4 and 5.

Embodiments of the present invention will be described with reference to the drawings. Each embodiment described below is only an example in which the present invention is embodied, and does not limit the technical scope of the present invention.
Embodiment 1:
1 is a circuit configuration diagram of a chiller according to an embodiment of the present invention, FIG. 2 is a block configuration diagram showing a control system of the chiller, and FIG. 3 is an external view of the chiller and a precision machine tool provided with the chiller.
In each figure, the chiller 1 according to this embodiment exchanges heat between a refrigerant circuit 38 that circulates refrigerant and performs a refrigeration cycle operation and a refrigerant in the refrigerant circuit 38 that circulates brine (water in this example). And a main body casing 46 containing the refrigerant circuit 38 and the brine circuit 39. The refrigerant circuit 38 includes a compressor 2 having a variable discharge capacity, an electromagnetic on-off valve 3, a condenser 36, a strainer 5, a linear expansion valve 6 whose valve opening is variable in a linear function with respect to a command input, and a cooler. 7 refrigerant flow paths 7 </ b> A and an accumulator 8 are sequentially connected in an annular manner via a refrigerant pipe 9. The brine circuit 39 described above includes a brine flow path 7B in the cooler 7 that exchanges heat with the refrigerant flow path 7A, an inflow pipe 19, a tank 4 that stores water W, and a pump 20 that sends out the water W in the tank 4. , And the load side heat exchanger 33 is configured to be sequentially connected in an annular manner through the water pipe 18. The load side heat exchanger 33 is provided in the precision machine tool 35 in order to keep the temperature in the external precision machine tool 35 (see FIG. 3) constant.

  In the refrigerant circuit 38, a refrigerant pipe 9 on the discharge side of the compressor 2 has a high pressure sensor 10 that detects a refrigerant pressure on the discharge side of the compressor 2, and a refrigerant at a first predetermined high pressure value (in this example, a refrigerant pressure of 4.15 mPa). A high pressure switch 11 for forcibly stopping the circuit 38 abnormally, a discharge refrigerant temperature sensor 41 for detecting the refrigerant temperature on the discharge side of the compressor 2, and a charge valve 12 for taking in and out the refrigerant are provided. The refrigerant pipe 9 on the suction side of the accumulator 8 detects the refrigerant pressure on the suction side of the compressor 2 and the refrigerant temperature on the suction side of the compressor 2 (corresponding to the refrigerant temperature on the outlet side of the cooler 7). An intake refrigerant temperature sensor 40 and a charge valve 16 for taking in and out the refrigerant are provided. The bypass circuit 13 described above is connected so as to branch from between the compressor 2 and the electromagnetic on-off valve 3 in the refrigerant circuit 38 so as to join between the linear expansion valve 6 and the cooler 7. A bypass electromagnetic opening / closing valve 15 is provided. In the vicinity of the condenser 36 in the main body casing 46, blowers 30, 30 for sucking outside air from the suction port 34 of the main body casing 46 and blowing the air to the condenser 36 are installed. The main casing 46 is provided with an electric box 29 containing a controller 42.

  In the brine circuit 39, an outlet water temperature sensor 21 that detects the outlet water temperature WT and a water pressure gauge 22 that detects the water pressure on the outlet side of the pump 20 are arranged in the water pipe 18 on the outlet side of the pump 20. The water pipe 18 on the outlet side of the pump 20 is connected to the inlet side of the load side heat exchanger 33 via the connection water pipe 31, and the water pipe 18 on the inlet side of the cooler 7 is connected to the load side via the connection water pipe 32. The outlet side of the heat exchanger 33 is connected. The tip of the inflow pipe 19 and the suction port of the pump 20 are arranged in the tank 4. The tank 4 is a container with a lid, and has a water level switch 23 for starting and stopping the pump 20 and a liquid level gauge 24 for viewing the water W from the outside. The tank 4 is connected to a lid drain drain port 25, a water supply port 26, an overflow port 27, and a tank drain drain port 28, respectively. The water level in the tank 4 may be confirmed from the outside through the liquid level gauge 24, and the water W may be manually supplied from the water supply port 26. A float type water supply valve (not shown) is provided in the tank 4, and this float type water supply is provided. Water may be automatically supplied by a valve.

  In addition, the secondary equipment 60 enclosed with the dashed-dotted line in FIG. 1 is the equipment employ | adopted by the general chiller, but the tank 61 which stores the water W, one end is arrange | positioned in the tank 61, and the other end is a pump. 20 Water pipe 62 connected to the outlet water pipe 18, one end arranged in the tank 61, the other end connected to the water pipe 18 on the inlet side of the cooler 7, one end arranged in the tank 61 A water pipe 64 whose other end is connected to the inlet side of the load-side heat exchanger 33, a water pipe 65 whose one end is disposed in the tank 61 and whose other end is connected to the outlet side of the load-side heat exchanger 33, water The secondary side pump 68 provided in the pipe 64, the secondary side pump 68, the branch water pipe 66 connecting the water pipe 64 and the water pipe 65 on the suction side, and the branch water pipe 66 and the water pipe 64 are provided at the branch positions. The three-way flow path switching valve 67 is configured. Although the chiller 1 of this embodiment is not provided with the secondary equipment 60, it is possible to attach such a secondary equipment 60 to the chiller 1.

A control system of the chiller 1 is shown in FIG. The controller 42 described above is configured with the CPU 37 as the center, and is wired and connected to the memory M and the input / output device via the data bus DB so as to allow data communication. That is, the high pressure sensor 10, the low pressure sensor 17, the discharge refrigerant temperature sensor 41, the intake refrigerant temperature sensor 40, the outlet water temperature sensor 21, the water level switch 23, the external input device 43, and the like are connected to the data input side of the data bus DB. Has been. The data output side of the data bus DB is connected to the linear expansion valve 6, the electromagnetic on-off valve 3, the bypass electromagnetic on-off valve 15, and the driver D that drives the pump 20, and the motor 45 that drives the compressor 2 has a rotational speed. An inverter device 44 for outputting a control inverter frequency command signal is connected. Then, the CPU 37 will be described in detail later, the function of the first high pressure adjustment means 48, the function of the discharge refrigerant temperature adjustment means 49, the function of the cooler outlet side refrigerant temperature adjustment means 50, the first low pressure adjustment means 51. Function, superheat degree calculating means 52 function, superheat degree adjusting means 53 function, second low pressure pressure adjusting means 54 function, heating operation means 55 function, second high pressure pressure adjusting means 56 function, and general It has the function of normal operation means 57 for performing proper PI control. Program software for executing the functions of these means is stored in advance in the memory M as program data, and is read from the memory M and used as necessary.
The first predetermined high pressure value, the second predetermined high pressure value, the third predetermined high pressure value, the predetermined discharge refrigerant temperature value, the first predetermined refrigerant temperature value, and the second predetermined refrigerant temperature value, which will be described in detail later. The first predetermined low pressure value, the second predetermined low pressure value, the third predetermined low pressure value, the predetermined superheat value, the first predetermined capacity, the second predetermined capacity, and the low pressure LP detected by the low pressure sensor 17. Conversion table data or the like for converting the refrigerant saturation temperature Te is set and inputted in advance from the external input device 43 and stored in the memory M. The chiller 1 having the above-described configuration is used by being connected to the load side heat exchanger 33 of the precision machine tool 35 shown in FIG.

The operation of the chiller 1 will be described. First, the “cooling operation” for cooling the water W (an example of the brine) of the brine circuit 39 will be described.
First, the operation of the refrigerant circuit 38 in the cooling operation will be described.
The high-temperature and high-pressure gas refrigerant discharged from the compressor 45 driven by the motor 45 whose rotational speed is controlled by the inverter device 44 enters the condenser 36 through the electromagnetic on-off valve 3, where it is cooled by the surrounding air, It becomes a high-temperature, high-pressure liquid refrigerant. This liquid refrigerant passes through the strainer 5 and is decompressed by the linear expansion valve 6 to become a low-pressure gas-liquid two-phase refrigerant. The gas-liquid two-phase refrigerant exchanges heat with water in the brine flow path 7B in the cooler 7 and evaporates to become a low-temperature / low-pressure gas refrigerant, and then returns to the compressor 1 via the accumulator 8. Repeat the operation. Heat that is exchanged with the refrigerant in the cooler 7 is water whose temperature has risen by cooling, for example, the precision machine tool 35 on the load side. The CPU 37 of the controller 42 determines the degree of superheat SH, which is the difference between the suction refrigerant temperature Ts of the refrigerant sucked into the compressor 2 and the refrigerant saturation temperature Te converted from the low pressure LP detected by the low pressure sensor 17. The PI control such as the rotational speed of the compressor 2 and the valve opening degree VO of the linear expansion valve 6 is performed so that the calculated superheat degree SH falls within the set target SH range of 4 to 7 ° C.

Next, the operation of the brine circuit 39 will be described.
In the cooler 7, the water W in the brine flow path 7B cooled by the refrigerant in the refrigerant flow path 7A flows into the tank 4 from the inflow pipe 19 and is stored. Thereafter, the water W in the tank 4 is pumped up by the pump 20 and sent to the load side heat exchanger 33 through the water pipe 18 and the connection water pipe 31 to cool the precision machine tool 35. The water whose temperature has increased due to this cooling returns to the brine flow path 7B of the cooler 7 via the connection water pipe 32 and the water pipe 18, and is cooled again by evaporation of the refrigerant in the refrigerant flow path 7A and then flows into the tank 4. Repeat the cycle. When the water level in the tank 4 is lowered, the water level is raised to a predetermined level by manual water supply from the water supply port 26, for example.
And water temperature control is described.
Usually, since the desired cold water supply temperature differs depending on the type of load-side precision machine used at the customer, the target water temperature value of the supplied water W is set in advance from the external input device 43 on the customer side. Get it. The refrigerant circuit 38 is controlled so that the difference between the set target water temperature value and the detected outlet water temperature WT becomes ± 0.1 ° C., and cools the water W. The cooled water W Water is sent to the exchanger 33. First, the outlet water temperature sensor 21 detects the outlet water temperature WT, and when the detected outlet water temperature WT is higher than the set target water temperature value, the rotational speed of the motor 45 of the compressor 2 is changed to the set target water temperature value. Drive to reach. That is, the water temperature control is microcomputer control by the CPU 37 using a PI control program that uses the difference between the outlet water temperature WT and the set target water temperature value. That is, the target motor rotation speed at that time is calculated, and a control command value is output to the inverter device 44 so as to operate at the calculated target motor rotation speed, and the inverter device 44 has an inverter frequency corresponding to the control command value. Thus, the motor 45 of the compressor 2 is driven to rotate. In this way, the outlet water temperature WT is made to reach the set target water temperature.

Subsequently, in the “heating operation” in which the water W is heated, the operation of the refrigerant circuit 38 will be described first.
In the case of heating operation, the bypass electromagnetic on-off valve 15 is opened and the electromagnetic on-off valve 3 is closed. Therefore, the high-temperature and high-pressure gas refrigerant discharged from the compressor 2 flows into the bypass circuit 13 and is decompressed through the capillary 14 that regulates the bypass flow rate to become a high-temperature and low-pressure gas refrigerant. This gas refrigerant enters the refrigerant flow path 7A of the cooler 7 from the bypass electromagnetic on-off valve 15 through the refrigerant pipe 9, and exchanges heat with the water W in the brine flow path 7B to heat the water W. At this time, the refrigerant becomes a low-temperature and low-pressure gas refrigerant, and returns to the compressor 2 through the accumulator 8.
Next, the operation of the brine circuit 39 will be described.
In general, the water temperature of the water W in the brine circuit 39 on the load side is often lower than the set target water temperature, particularly before the device is started in winter. At that time, the above-described heating operation is performed, and water W that has been heated up to the set target water temperature is generated and stored in the tank 4. When the load-side precision machine tool 35 or the like starts operation, the water temperature in the brine circuit 39 inevitably rises, so that the cooling operation mode described above can be restored.

  As general performance of the chiller 1, as shown in FIG. 4, the load amount (indicated by a two-dot chain line A in the figure) and the inlet water temperature (indicated by a one-dot chain line B in the figure) returning to the cooler 7. Even if it fluctuates, it is possible to supply cold water to the load-side heat exchanger 33 without causing a large fluctuation in the outlet water temperature WT (shown by the solid line C in the figure) on the outlet side of the cooler 7. When the load is stable, as shown in the two enlarged circles in FIG. 4, the outlet water temperature WT is within ± 0.1 ° C. of the set target water temperature value, and an extremely stable cold water supply is achieved. it can. By adopting the high-performance inverter device 44, it is possible to continue the operation in the range of the operation capacity (motor rotation speed) from 20% load to 100% load.

As shown in FIG. 5, the ambient temperature of the chiller 1 is −5 to 43 ° C., that is, the range of the outlet water temperature WT that can be set by the customer's desired input from the external input device 43 throughout the year is 3 ° C. to 30 ° C. Cold water in a wide temperature range of 0 ° C. can be supplied to the load-side heat exchanger 33.
Further, since the chiller 1 is configured such that the compressor 2 has a variable discharge capacity under the control of the inverter device 44, the coefficient of performance COP by the chiller 1 is the solid line D (ambient temperature = 0 ° C., outlet water shown in FIG. As shown by a temperature WT = 5 ° C.) and a one-dot chain line E (ambient temperature = 35 ° C., outlet water temperature WT = 5 ° C.), a chiller COP using a compressor with a constant discharge capacity (dashed line F1). , F2)).

Next, a characteristic protection control operation of the chiller 1 according to the first embodiment will be described with reference to the flowchart of FIG.
First, “high pressure rise protection control” will be described.
Generally, when the ambient temperature such as the outside air temperature is high, the high pressure HP on the discharge side of the compressor 2 in the refrigerant circuit 38 increases. When the high pressure HP reaches 4.15 mPa, the refrigerant circuit 38 is abnormally stopped called a high cut. Since the load side device (for example, the precision machine tool 35 of FIG. 3) must be stopped when the refrigerant circuit 38 stops, it is desirable to avoid stopping the refrigerant circuit 38 as much as possible.
Therefore, as shown by the program 1 in FIG. 7A, the CPU 37 takes in the high pressure HP detected by the high pressure sensor 10 (step S1, the following steps are omitted, and only S is shown). If the taken-in high pressure HP is 3.8 mPa or more (Y in S2) and 4.15 mPa or more (Y in S3), the refrigerant circuit 38 and the brine circuit 39 are forcibly determined that the high pressure HP is abnormal. (S4). On the other hand, when the high pressure HP is 3.8 mPa or more (Y of S2) and less than 4.15 mPa (N of S3), the CPU 37 controls the inverter device 44 to set the rotation speed of the motor 45 of the compressor 2 to 10 rps. (10 revolutions per second) is lowered, and operation is performed for a predetermined time (the time until the control state of the refrigerant circuit 38 settles down, for example, 120 seconds) (S5). Thereafter, if the high pressure HP detected this time by the high pressure sensor 10 is not lower than the previously detected high pressure HP (N in S6, S7), the processes of S5 to S7 are repeated. If the current high pressure HP is lower than the previous high pressure HP (Y in S7), the process waits for the high pressure HP to drop below 3.8 mPa (N in S8 and S9), and the high pressure HP is When the pressure falls below 3.8 mPa (Y in S9), the normal operation means 57 of the CPU 37 returns the refrigerant circuit 38 to the original normal operation by PI control (S10). The above control is repeated to avoid a high cut, and the operation of the refrigerant circuit 38 is continued.
In other words, the first high pressure adjustment means 48 of the CPU 37 is configured so that the high pressure HP on the discharge side of the compressor 2 detected by the high pressure sensor 10 is a first predetermined high pressure value (this In the example, when the second predetermined high pressure value (3.8 mPa in this example) is lower than 4.15 mPa) or higher, the discharge capacity of the compressor 2 (corresponding to the number of rotations) until the second predetermined high pressure value is reduced. ) Is gradually lowered.

Next, “discharge refrigerant temperature rise prevention control” will be described.
In general, under conditions where the load side water temperature is low and the ambient temperature is high (the refrigeration cycle conditions are such that the high pressure HP is high and the low pressure LP is low), the discharge refrigerant temperature DT on the discharge side of the compressor 2 may increase. Arise. When the discharged refrigerant temperature DT is 110 ° C. or higher, the refrigeration oil used in the refrigerant circuit 38 may be deteriorated.
Therefore, as shown by the program 2 in FIG. 3B, the CPU 37 takes in the discharged refrigerant temperature DT detected by the discharged refrigerant temperature sensor 41 (S11). Then, when the discharged refrigerant temperature DT taken in exceeds 110 ° C. (Y in S12), the CPU 37 controls the inverter device 44 to reduce the rotational speed of the motor 45 of the compressor 2 by about 10% of the rated maximum rotational speed. In this state, the operation for the predetermined time described above is performed (S13). Thereafter, if the discharged refrigerant temperature DT detected by the discharged refrigerant temperature sensor 41 is not 110 ° C. or less (N in S14 and S15), the processes in S13 to S15 are repeated. Then, if the discharge refrigerant temperature DT detected this time is 110 ° C. or less (Y in S15), the normal operation means 57 of the CPU 37 returns the refrigerant circuit 38 to the original normal operation by PI control (S16).
In other words, the discharge refrigerant temperature adjusting means 49 of the CPU 37 is configured so that the discharge refrigerant temperature DT on the discharge side of the compressor 2 detected by the discharge refrigerant temperature sensor 41 is set to a predetermined discharge refrigerant temperature value (110 ° C. in this example). ), The discharge capacity (corresponding to the number of revolutions) of the compressor 2 is gradually lowered until the temperature becomes equal to or lower than the predetermined discharge refrigerant temperature value.

Then, “chiller freezing prevention control in chiller” will be described.
In general, when the temperature (example of the cooler outlet temperature) Ts detected by the suction refrigerant temperature sensor 40 becomes −5 ° C. or lower for the refrigerant discharged from the cooler 7, partial freezing of cold water occurs in the cooler 7. There is a possibility. If left as it is, it will be completely frozen, and the brine flow path 7B of the cooler 7 may burst due to freezing. In order to prevent this, a control for abnormally stopping the refrigerant circuit 38 when the refrigerant temperature Ts on the outlet side of the cooler 7 reaches −12 ° C. is incorporated. However, if the control can be recovered in advance before the abnormal stop, it is not over that.
Therefore, as shown by the program 3 in FIG. 7C, the CPU 37 takes in the refrigerant temperature Ts on the outlet side of the cooler 7 detected by the intake refrigerant temperature sensor (an example of the refrigerant outlet side refrigerant temperature sensor) 40 ( S21), if the refrigerant temperature Ts taken in is less than −5 ° C. (Y in S22) and −12 ° C. or less (Y in S23), the refrigerant circuit 38 and the The brine circuit 39 is forcibly stopped (S24). On the other hand, when the refrigerant temperature Ts is lower than −5 ° C. (Y in S22) and higher than −12 ° C. (N in S23), the CPU 37 controls the inverter device 44 to control the rotation speed of the motor 45 of the compressor 2. The rated maximum rotational speed is lowered by about 5%, and the operation for the predetermined time described above is performed in this state (S25). Thereafter, if the refrigerant temperature Ts detected by the intake refrigerant temperature sensor 40 is not −5 ° C. or higher (N of S26 and S27), the processes of S25 to S27 are repeated. If the refrigerant temperature Ts detected this time is equal to or higher than −5 ° C. (Y in S27), the normal operation means 57 of the CPU 37 returns the refrigerant circuit 38 to the original normal operation by the PI control (S28).
That is, the cooler outlet-side refrigerant temperature adjusting means 50 of the CPU 37 is configured such that the refrigerant temperature Ts on the outlet side of the cooler 7 detected by the intake refrigerant temperature sensor 40 is a preset first predetermined refrigerant temperature for abnormal stop that is set in advance. When the temperature falls below a second predetermined refrigerant temperature value (−5 ° C. in this example) that is higher than the value (−12 ° C. in this example), the discharge capacity (rotation) of the compressor 2 until the temperature reaches the second predetermined refrigerant temperature value or higher. (Corresponding to the number) is gradually lowered.

As described above, in the chiller 1 of the first embodiment, the high pressure HP on the discharge side of the compressor 2 is increased by the “high pressure rise protection control” and the first predetermined high pressure value (4 .15 mPa), the rotational speed of the motor 45 of the compressor 2 is temporarily lowered to operate, so that the high pressure HP can be lowered or kept at that pressure. it can. As a result, it is possible to avoid the abnormal stop of the refrigerant circuit 38 as much as possible and to extend the operation.
Further, when the discharge refrigerant temperature DT on the discharge side of the compressor 2 rises and exceeds the predetermined discharge refrigerant temperature value (110 ° C.) for preventing refrigeration oil deterioration by “discharge refrigerant temperature rise prevention control”, Since the operation of the motor 45 of the compressor 2 is gradually reduced, the discharged refrigerant temperature DT can be lowered to a predetermined discharged refrigerant temperature value or less. Thereby, deterioration of the refrigeration oil in the refrigerant circuit 38 can be prevented, and early stop of the refrigerant circuit 38 can be avoided.
When the refrigerant temperature Ts on the outlet side of the cooler 7 in the refrigerant circuit 38 is reduced by the “chiller freezing water freeze prevention control” and approaches the first predetermined refrigerant temperature value (−12 ° C.) for abnormal stop, Temporarily lowering the rotational speed of the motor 45 of the compressor 2 in the refrigerant circuit 38 and temporarily operating the refrigerant circuit 38, the refrigerant temperature Ts on the outlet side of the cooler 7 is raised, or the outlet side refrigerant temperature at that time is kept. Can do. As a result, it is possible to prevent brine freezing in the cooler 7, avoid the abnormal stop of the refrigerant circuit 38 as much as possible, and extend the operation.
Many of these types of chillers are provided with the secondary equipment 60 described above, but the chiller 1 of this embodiment has sufficient performance even without the secondary equipment 60.

Embodiment 2:
Next, Embodiment 2 according to “low pressure increase prevention control” will be described.
Generally, when the water temperature on the load side of the cooler 7 is high, the low pressure LP of the refrigerant circuit 38 increases. When the low pressure LP is 1.15 mPa or more, the bearing wear or mechanism of the compressor 2 is adversely affected and the life of the compressor 2 is shortened. Therefore, it is necessary to control the refrigerant circuit 38 so that the low pressure LP is not as high as 1.15 mPa.
Therefore, as shown by the program 4 in FIG. 8A, the CPU 37 takes in the low pressure LP detected by the low pressure sensor 17 (S31). Then, when the taken-in low pressure LP is 1.15 mPa or more (Y in S32), the CPU 37 controls the driver D of the linear expansion valve 6 to lower the valve opening VO by about 5% of the maximum valve opening, The operation for the predetermined time described in the state is performed (S33). Thereafter, if the low pressure LP detected this time by the low pressure sensor 17 is not lower than the previously detected low pressure LP (N of S34, S35), the processing of S33 to S35 is repeated. If the current low pressure LP is lower than the previous low pressure LP (Y in S35), the process waits for the low pressure LP to be lower than 1.15 mPa (N in S36, S37). If it falls below 1.15 mPa (Y in S37), the normal operation means 57 of the CPU 37 returns the refrigerant circuit 38 to the original normal operation by PI control (S38). The above control is repeated to prevent the low pressure LP from rising. However, the minimum valve opening of the linear expansion valve 6 is limited to 10%.
That is, the first low-pressure pressure adjusting means 51 of the CPU 37 is configured so that the low-pressure pressure LP on the compressor 2 suction side detected by the low-pressure sensor 17 is set to a first predetermined low-pressure pressure value (1.15 mPa in this example). ) When the above is reached, the valve is operated by gradually decreasing the valve opening VO of the linear expansion valve 6 until it falls below the first predetermined low pressure value.
By controlling in this way, even when the low-pressure pressure LP on the suction side of the compressor 2 increases, it is possible to avoid the low-pressure pressure LP from exceeding the first predetermined low-pressure value as much as possible. As a result, adverse effects such as bearing wear on the compressor 2 can be removed, and the life of the compressor 2 can be extended.

Embodiment 3:
Next, a third embodiment according to “superheat reduction control” will be described.
Generally, the difference between the suction refrigerant temperature Ts on the suction side of the compressor 2 and the refrigerant saturation temperature Te converted from the low pressure LP detected by the low pressure sensor 17 is referred to as superheat degree SH (= Ts−Te). Yes. When the degree of superheat SH is 0, it means that the refrigerant is not superheated and is in a wet region, so that the refrigerant returns to the compressor 2 while remaining in a liquid state. It may cause failure. Therefore, it is necessary to keep the superheat degree at 2 ° C. or higher as much as possible.
Therefore, as shown by the program 5 in FIG. 8B, the CPU 37 collates the low pressure LP detected by the low pressure sensor 17 with the conversion table data in the memory M to obtain the refrigerant saturation temperature Te, and this refrigerant saturation. The degree of superheat SH is calculated as the difference between the temperature Te and the intake refrigerant temperature Ts detected by the intake refrigerant temperature sensor 40 (S41). If the calculated degree of superheat SH is less than 2 degrees (Y in S42), the CPU 37 lowers the valve opening VO of the linear expansion valve 6 by about 5% of the maximum valve opening, and in this state for the predetermined time described above. Operation is performed (S43). Thereafter, the low pressure LP and the suction refrigerant temperature Ts are detected and the superheat degree SH is calculated (S44). If the calculated superheat degree SH is not 4 degrees or more (N in S45), the process returns to S43 to perform linear expansion. The valve opening degree VO of the valve 6 is further reduced by 5%, and the operation for the predetermined time described above is performed. If the current superheat degree SH is 4 degrees or more (Y in S45), the normal operation means 57 of the CPU 37 returns the refrigerant circuit 38 to the original normal operation by the PI control (S46). The above control is repeated to avoid an excessive decrease in the superheat degree SH. However, the minimum valve opening of the linear expansion valve 6 is limited to 10%.
That is, the superheat degree calculation means 52 of the CPU 37 is based on the compressor suction side temperature Ts detected by the suction refrigerant temperature sensor 40 and the low pressure pressure LP on the compressor suction side detected by the low pressure sensor 17. SH is calculated. Then, when the superheat degree SH calculated by the superheat degree calculation means 52 falls below a predetermined superheat degree value (2 degrees in this example), the superheat degree adjusting means 53 becomes equal to or higher than the predetermined superheat degree value. Thus, the operation is performed by gradually decreasing the valve opening VO of the linear expansion valve 6 of the refrigerant circuit 38.
By controlling in this way, the superheat degree SH can be raised to a predetermined superheat degree value or more, and the liquid back to the compressor 2 can be avoided. As a result, failure of the compressor 2 can be prevented in advance.

Embodiment 4:
Then, Embodiment 4 according to “low pressure pressure drop prevention control” will be described.
When the ambient temperature is low and the load-side water temperature is low, if the low pressure LP of the refrigerant circuit 38 is lowered to 0.47 mPa or less, the lubrication system of the compressor 2 may be hindered. Therefore, it is necessary to control the refrigerant circuit 38 so that the low pressure LP is not set to 0.47 mPa or less.
9A, the CPU 37 takes in the low pressure LP detected by the low pressure sensor 17 (S51), and the taken-in low pressure LP is 0.40 mPa smaller than 0.47 mPa. (Y in S52), the CPU 37 controls the inverter device 44 to reduce the rotational speed of the motor 45 of the compressor 2 by about 10% of the rated maximum rotational speed, and the operation for the predetermined time described in that state is performed. (S53). Thereafter, the low pressure LP is detected by the low pressure sensor 17 (S54). If the low pressure LP is not 0.40 mPa or more (N in S55), the processes of S53 to S55 are repeated. Then, when the low pressure LP detected in S54 becomes 0.40 mPa or more (Y in S55), the CPU 37 reduces the rotation speed of the motor 45 of the compressor 2 by about 5% and operates for the predetermined time described above. (S56). Thereafter, if the detected low pressure LP is not 0.47 mPa or more (N in S57 and S58), the processes in S56 to S58 are repeated. When the low pressure LP detected in S57 recovers to 0.47 mPa or more (Y in S58), the normal operation means 57 of the CPU 37 returns the refrigerant circuit 38 to the original normal operation by the PI control (S59).

That is, the second low pressure adjusting means 54 of the CPU 37 performs two-stage control. First, when the low pressure LP on the suction side of the compressor 2 detected by the low pressure sensor 17 falls below a preset second predetermined low pressure value (0.40 mPa in this example), the second predetermined low pressure is set. The compressor 2 is operated with the discharge capacity (corresponding to the rotational speed) of the compressor 2 greatly decreased by a first predetermined capacity (10% in this example) until the value becomes equal to or greater than the value. Next, when the detected low pressure LP becomes equal to or higher than the second predetermined low pressure value, the discharge capacity of the compressor 2 is gradually increased by a second predetermined capacity (5% in this example) smaller than the first predetermined capacity. The operation is continued until the pressure reaches a third predetermined low pressure value (0.47 mPa in this example) that is greater than the second predetermined low pressure value.
By controlling in this way, the low pressure LP of the refrigerant circuit 38 can be quickly made equal to or higher than the third predetermined low pressure value. As a result, troubles that may occur in the lubrication system of the compressor 2 can be avoided in advance.

Embodiment 5:
Next, Embodiment 5 according to “high pressure protection control during heating operation” will be described.
Even when the operation is performed in the heating operation mode and the load side water temperature is high, the high pressure HP may increase and a high cut may occur.
Therefore, in order to prevent this, as shown by the program 7 in FIG. 9B, the CPU 37 performs a heating operation in which the refrigerant from the compressor 2 flows through the bypass circuit 13 to the cooler 7 ( (S61) The high pressure HP detected by the high pressure sensor 10 is taken in (S62). Then, if the taken-in high pressure HP is 3.8 mPa or more (Y in S63) and 4.15 mPa or more (Y in S64), the refrigerant circuit 38 and the brine circuit 39 are forcibly determined that the high pressure HP is abnormal. (S65). On the other hand, when the high pressure HP is 3.8 mPa or more (Y in S63) and less than 4.15 mPa (N in S64), the CPU 37 opens the electromagnetic on-off valve 3 of the refrigerant circuit 38 and condenses the refrigerant from the compressor 2. The high pressure HP is decreased by flowing through the vessel 36 (S66). Thereafter, it waits for the high pressure HP to fall below 2.8 mPa (N in S67, S68), and after the high pressure HP falls below 2.8 mPa (Y in S68), the electromagnetic on-off valve 3 is closed (S69). Return to normal heating operation (S70).
That is, the heating operation means 55 of the CPU 37 closes the electromagnetic on-off valve 3 of the refrigerant circuit 38 and causes the refrigerant from the compressor 2 to flow from the bypass circuit 13 to the cooler 7. Then, the second high pressure adjustment means 56 is configured such that the high pressure HP detected by the high pressure sensor 10 during the heating operation by the heating operation means 55 is a first predetermined high pressure value for abnormal stop that is set in advance. When the second predetermined high pressure value (3.8 mPa in this example) is lower than (in this example, 4.15 mPa) or higher, a third predetermined high pressure value (lower than the second predetermined high pressure value) ( In this example, the electromagnetic on-off valve 3 of the refrigerant circuit 38 is opened until the pressure falls below 2.8 mPa), and the refrigerant from the compressor 2 is caused to flow through the condenser 36 for operation.
By controlling in this way, when the high pressure HP on the discharge side of the compressor 2 increases during the heating operation and approaches the first predetermined high pressure value for abnormal stop, the electromagnetic on-off valve 3 of the refrigerant circuit 38 is temporarily. Therefore, the high pressure HP can be lowered or at least kept at the pressure value at that time. Thereby, it is possible to avoid the abnormal stop of the refrigerant circuit 38 and to extend the operation.

  In the above-described embodiment, an example in which the chiller 1 is connected to the precision machine tool 35 that is the load side device is shown. However, the chiller of the present invention is not limited thereto, and other than the precision machine tool 35, for example, The present invention can also be applied to industrial fields such as analyzers, laser processing machines, molding machines, exposure machines, and etching apparatuses, or food manufacturing fields and medical fields.

DESCRIPTION OF SYMBOLS 1 Chiller 2 Compressor 3 Electromagnetic on-off valve 4 Tank 6 Linear expansion valve 7 Cooler 7A Refrigerant flow path 7B Brine flow path 9 Refrigerant pipe 10 High pressure sensor 13 Bypass circuit 14 Capillary 17 Low pressure sensor 18 Water pipe 20 Pump 21 Outlet side Water temperature sensor 31 Connection water piping 32 Connection water piping 33 Load side heat exchanger 35 Precision machine tool 36 Condenser 37 CPU
38 Refrigerant circuit 39 Brine circuit 40 Suction refrigerant temperature sensor (cooler outlet refrigerant temperature sensor)
41 Discharge refrigerant temperature sensor 44 Inverter device 45 Motor 48 First high pressure adjustment means 49 Discharge refrigerant temperature adjustment means 50 Cooler outlet side refrigerant temperature adjustment means 51 First low pressure adjustment means 52 Superheat degree calculation means 53 Superheat degree adjustment means 54 Second low pressure adjustment means 55 Heating operation means 56 Second high pressure adjustment means 57 Normal operation means M Memory W Water DT Discharge refrigerant temperature HP High pressure LP Low pressure SH Superheat Ts Intake refrigerant temperature (cooler outlet temperature)
Te Refrigerant saturation temperature VO Valve opening

Claims (5)

A refrigerant circuit configured by sequentially connecting a refrigerant flow path of a compressor having a variable discharge capacity, an electromagnetic on-off valve, a condenser, an expansion valve having a variable valve opening degree, and a cooler, and a refrigerant flow path in the cooler A brine circuit configured by sequentially connecting a brine flow path, a tank, a pump, and an external load-side heat exchanger in an annular manner to exchange heat with the high pressure for detecting the pressure on the compressor discharge side in the refrigerant circuit In a chiller having a pressure sensor, a discharge refrigerant temperature sensor for detecting a compressor discharge side temperature in the refrigerant circuit, and a cooler outlet side refrigerant temperature sensor for detecting a cooler outlet side temperature in the refrigerant circuit,
When the compressor discharge side pressure detected by the high pressure sensor becomes equal to or higher than a second predetermined high pressure value that is lower than a first predetermined high pressure value for preset abnormal stop, the second predetermined high pressure is set. First high-pressure adjusting means that operates by gradually decreasing the discharge capacity of the compressor until it falls below the value;
When the compressor discharge-side temperature detected by the discharge refrigerant temperature sensor exceeds a preset predetermined discharge refrigerant temperature value, the compressor discharge capacity is gradually decreased until the compressor discharge side temperature falls below the predetermined discharge refrigerant temperature value. Discharging refrigerant temperature adjusting means for
When the cooler outlet-side temperature detected by the cooler outlet-side refrigerant temperature sensor falls below a second predetermined refrigerant temperature value that is higher than a first predetermined refrigerant temperature value that is set in advance for an abnormal stop, the first 2 cooler outlet side refrigerant temperature adjusting means that operates by gradually decreasing the discharge capacity of the compressor until the refrigerant reaches a predetermined refrigerant temperature value or higher;
A chiller comprising: A low pressure sensor for detecting the pressure on the compressor suction side in the refrigerant circuit;
When the compressor suction-side pressure detected by the low-pressure pressure sensor becomes equal to or higher than a first predetermined low-pressure pressure value, the operation of the expansion valve is decreased until it falls below the first predetermined low-pressure pressure value. The chiller according to claim 1, further comprising: a first low-pressure adjustment unit that performs An intake refrigerant temperature sensor for detecting the temperature at the compressor intake side in the refrigerant circuit;
Superheat degree calculating means for calculating the degree of superheat based on the compressor suction side temperature detected by the suction refrigerant temperature sensor and the compressor suction side pressure detected by the low pressure sensor;
When the superheat degree calculated by the superheat degree calculation means falls below a predetermined superheat degree value set in advance, the superheat degree is operated by lowering the valve opening of the expansion valve of the refrigerant circuit until the superheat degree value becomes equal to or higher than the predetermined superheat degree value. The chiller according to claim 1, further comprising an adjusting unit. A low pressure sensor for detecting the pressure on the compressor suction side in the refrigerant circuit;
When the compressor suction side pressure detected by the low pressure sensor is lower than a preset second predetermined low pressure value, the discharge capacity of the compressor is set to the first predetermined capacity until it becomes equal to or higher than the second predetermined low pressure value. When the detected compressor suction side pressure exceeds the second predetermined low pressure value, the discharge capacity of the compressor is decreased by a second predetermined capacity smaller than the first predetermined capacity, and the second 4. The chiller according to claim 1, further comprising: a second low-pressure pressure adjusting unit that operates until a third predetermined low-pressure pressure value that is larger than the predetermined low-pressure pressure value is reached. A bypass circuit having a capillary connected to be branched from between the compressor and the electromagnetic on-off valve in the refrigerant circuit and joined between the expansion valve and the cooler;
Heating operation means for closing the electromagnetic on-off valve of the refrigerant circuit and flowing the refrigerant from the compressor through the bypass circuit to the cooler;
During the heating operation by the heating operation means, the compressor outlet pressure detected by the high pressure sensor is equal to or higher than a second predetermined high pressure value that is lower than a first predetermined high pressure value for abnormal stop set in advance. And a second high-pressure adjusting means that opens and operates the electromagnetic on-off valve of the refrigerant circuit until it falls below a third predetermined high-pressure value that is set lower than the second predetermined high-pressure value. The chiller according to any one of claims 1 to 4, wherein the chiller is characterized.

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