JPH0151749B2 - - Google Patents

Description

[Detailed description of the invention]

(B) Industrial Application Field The present invention provides a method for controlling a refrigerator equipped with a refrigerant circuit that connects a compressor with variable operating capacity, a heat source side heat exchanger, a pressure reduction device, and a user side heat exchanger. It is related to. (b) Conventional technology Conventional technology related to such a control method includes Japanese Utility Model Publication No. 16995/1983 and Japanese Unexamined Patent Application Publication No. 1983-16995.
There was something like the one described in Publication No. 59652. The publication states that ``a refrigerating machine drive motor is provided with a detection element for detecting its load capacity, and the adjustment range of the refrigeration capacity adjustment mechanism is limited by a command from the detection element.'' The publication states that ``the motor load is detected by current.'' The conventional technology that combines these publications is to detect the load capacity of the refrigerator from the current flowing through the compressor motor, and if this current value is within the normal value, the refrigeration capacity is calculated based on this current value. Only a control method has been disclosed in which the adjustment range of the refrigerating capacity is restricted when the current value reaches an overcurrent (overload). (c) Problems to be Solved by the Invention In the conventional technology as described above, the refrigerating capacity is adjusted based on the current value, so the temperature fluctuation of the load is calculated based on the amount of evaporation of the refrigerant in the heat exchanger and the current. This will be known through the change in value. In other words, there is a problem in that the adjustment of the refrigerating capacity in response to temperature fluctuations in the load is delayed, resulting in a wide range of load temperature fluctuations. Furthermore, there is no fixed correlation between the temperature change of the load and the increase/decrease in the current value, and the current does not always follow the temperature change of the load, and the range of temperature fluctuation of the load sometimes becomes large. Furthermore, in the event of an overload, the adjustment range of the refrigeration capacity is changed according to the increase/decrease of the current (effectively, the refrigeration capacity is reduced), so the refrigeration capacity change may chattering around this current value, resulting in a shortened lifespan of the equipment. The larger the refrigerating capacity, the greater the effect). In view of these problems, the present invention provides a control method that can optimally change the refrigerating capacity in accordance with the temperature fluctuations of the load, and at the same time, can quickly avoid an overload state in the event of an overload. (d) Means for Solving the Problems The control method of the present invention includes an electric compressor whose operating capacity can be changed, a heat source side heat exchanger, a pressure reducing device, and a user side heat exchanger provided on the load side. The refrigerator includes a capacity control section that changes the operating capacity of the compressor based on the temperature of the load, and the value of the current flowing through the drive motor of the compressor is set to a first Once the current value exceeds the first set value, a signal is output to the capacity control unit to reduce the operating capacity of the compressor. 2, a signal for increasing the operating capacity of the compressor is output to the capacity control section. (E) Effect In the control method configured in this way, the operating capacity of the compressor is appropriately set based on the temperature of the load, and overload of the compressor is detected from an increase in current to adjust the operating capacity of the compressor. When the current value flowing through the compressor once falls below the second set value after a certain period of time after the current value is reduced, the operating capacity of the compressor is increased again. (f) Examples Examples of the present invention will be described below based on the drawings. First, as shown in FIG. 1, a refrigerator to which the present invention is applied includes a compressor 1, a four-way valve 2, a heat source side heat exchanger 3, a liquid receiver 4, a pressure reducing device 5, and a user side heat exchanger 3. The exchanger 6 and the accumulator 7 are connected to form a refrigerant circuit 8. Note that 9 and 10 are check valves for cooling, and 11 and 12 are check valves for heating. This compressor 1 has a variable operating capacity (compression capacity). Mechanisms for changing the operating capacity include those that control the compressor with multiple unloader valves, those that change the number of drive cylinders of a reciprocating compressor, and the capacity control valve of a screw compressor. Various mechanisms are conceivable, such as one that controls the speed of the compressor, and one that changes the rotation speed of the compressor drive motor. The following explanation will be given assuming that the capacity can be controlled. The refrigerant discharged from the compressor 1 is discharged through the discharge line 1
3 through the four-way valve 2 in the direction of the solid arrow during cooling, and in the direction of the broken arrow during heating, and returns to the compressor 1 from the suction line 14 via the four-way valve 2 and the accumulator 7. At this time, the heat source side heat exchanger 3 acts as a condenser during cooling and as an evaporator during heating, and the blower 15 promotes heat exchange with outside air. Further, the user-side heat exchanger 6 acts as an evaporator during cooling and as a condenser during heating to cool or heat the secondary refrigerant (for example, water) in the secondary refrigerant circuit 16. This hot and cold water is circulated through the secondary refrigerant circuit 16 by the pump 17 and supplied to the fan coil 18, where heat exchange between the cold and hot water and the indoor air is performed, thereby cooling or heating the room. . The compression capacity of the compressor 1 is adjusted according to the inflow temperature of the secondary refrigerant into the user-side heat exchanger 6, so that the outflow temperature of the secondary refrigerant becomes an appropriate temperature. In FIG. 2, l is a bus bar to which a constant DC voltage is supplied via the operation switch 19. A microcomputer 20 has a power terminal BT connected to a bus line l, and an oscillator 21 that determines the free running time of the microcomputer 20 between clock terminals CL1 and CL2. Reference numeral 22 denotes a heating/cooling selection switch, one end of which is connected to the bus line I, and the other end connected to the input port I1 of the microcomputer 20. Reference numeral 23 denotes a secondary refrigerant temperature measuring circuit which is supplied with a DC constant voltage from the bus line l and which converts an analog signal of a temperature sensor 24 that detects the inflow temperature of the secondary refrigerant into the user-side heat exchanger 6 into a binary digital signal. , the output end is connected to the input port I2. Reference numeral 25 denotes an operating current measuring circuit to which a DC constant voltage is supplied from the bus line l, and which measures the operating current of the drive motor CM of the compressor 1 shown in FIG. 3 as a binary digital value, and its output end is connected to the input port I3. It is connected to the.
The circuit 25 has a primary winding 261 connected to a driving motor CM.
After converting the current flowing through the secondary winding 262 of the current transformer 26 connected in series to the voltage, rectifying and smoothing it, the difference voltage with respect to the reference voltage is determined, and the difference voltage is expressed as A-
The operating current of the drive motor CM is measured by D (analog-to-digital) conversion. 2
A reference pulse generator 7 generates a reference pulse of a predetermined frequency using a constant DC voltage supplied from the bus line I, and its output end is connected to the input port I4. Reference numeral 28 denotes a control relay circuit consisting of control relays 29 to 34, one end of each relay being connected to bus line l, and the other end being connected to output ports P1 to P6 via drivers 35 each having a reversing mechanism. Reference numeral 36 denotes a warning lamp, one end of which is connected to the bus line l, and the other end connected to the output port P7 via a driver 37 having a reversing mechanism. In FIG. 3, 38 is an AC power supply, which includes an excitation relay 39 for the four-way valve 2, a power supply relay 40 for the drive motor FM of the blower 15, a power supply relay 41 for the drive motor CM of the compressor 1, Capacity adjustment relays 42, 43 and 44 of compressor 1 are connected to AC power supply 38 via normally open switches 291 to 341 of control relays 29 to 34, respectively. Further, the drive motor FM is connected to the AC power source 38 via the normally open switch 401 of the power supply relay 40, and the drive motor CM is connected to the AC power source 38 via the normally open switch 411 of the power supply relay 41. FIG. 4 shows the internal system of the microcomputer 20.
0 is sent via the input port I2 and a cooling/heating command device 45 that issues a cooling or heating command depending on whether a low-level "0" signal or a high-level "1" signal is present at the input port I1. Temperature storage device 46 that stores the latest temperature data received.
, a set value storage device 47 that stores a set value to be compared with the temperature data of the storage device 46, a current storage device 48 that stores the latest current data sent through the input port I3, and a storage device. A set value storage device 49 stores a set value to be compared with the current data of 48, and the next stage control compares the stored contents of both storage devices 46 and 47 to obtain the characteristics shown in FIGS. 5 and 6. a temperature comparator 51 that instructs the signal generator 50 to issue the control signals shown in Table 1;
A current comparator 52 compares the values stored in both storage devices 48 and 49 and outputs outputs A and B to a control signal generator 50, and outputs from both comparators 51 and 52 are processed by a program to output ports P1 to P7. Based on the commands from the control signal generator 50 that issues a control signal of "1" or "0" from the current comparator 52, the reference pulse from the input port I4 is used to count the time for 3 seconds and 10 minutes, respectively. It is composed of timer devices 53 and 54.

[Table] It is assumed that the cooling/heating selection switch 22 is open during the current cooling season. When the operation switch 19 is closed, the microcomputer 20 connects to the input port I1.
In response to the "0" signal, the cooling/heating command device 45 issues a cooling command to the control signal generating device 50, and at the same time stores in the storage device 46 the temperature data of the secondary refrigerant flowing into the user-side heat exchanger 6, which comes in from the input port I2. When the secondary refrigerant inflow temperature is 14° C., as is clear from the characteristics shown in FIG.
Since a command is issued to issue a control signal [1, 1, 1, 1] from the driver 35, all of the control relays 31 to 34 are energized. Therefore, the power supply relay 41 is energized, the drive motor CM is operated, and the capacity adjustment relays 42 to 44 are energized.
is excited, the compressor 1 operates at 100% compression capacity, and the secondary refrigerant cooled by the user-side heat exchanger 6 is supplied to the fan coil 18 to perform indoor cooling operation. Note that the "1" signal is also supplied from the output port P2, and the control relay P2 is energized and the power relay 40 is excited, so the drive motor FM is operated and the blower 15 is operated.
Since the "0" signal is supplied to the output port P1, the control relay 29 is not energized, and the four-way valve excitation relay 39 is also not energized, so the four-way valve 2 is in a solid line state. During this operation, when the secondary refrigerant inflow temperature of the user-side heat exchanger 6 falls below 10°C, the control signal generator 50 outputs [1, 1, 1,
0], the control relay 34 and the capacity adjustment relay 44 are de-energized and the compressor 1 is operated at 75% capacity, and as a result, the secondary refrigerant inflow temperature begins to rise, and the 12 When the temperature exceeds ℃, the compressor returns to 100% operation again. Conversely, when the secondary refrigerant inflow temperature further decreases and falls below 9°C, the control signal generator 50 issues a control signal of [1, 1, 0, 0], and further controls the control relay 33 and the capacity adjustment relay 4.
Turn off power to compressor 3 and operate compressor 1 at 50% capacity. In this way, the control signal generator 50
In response to a command from a temperature comparison device 51 that compares the secondary refrigerant inflow temperature and a set value according to the characteristics of the figure, the compressor 1
Automatically controlled in 5 stages from (stop) to 100%. The current comparison device 52 compares the operating current of the drive motor CM stored in the storage device 48 with the first set value 265A and the second set value 295A of the storage device 49. The second set value is set close to the maximum allowable current of the drive motor CM of the compressor 1, and the first set value is set to about 90% of the second set value. When the compressor 1 is operating at 100% compression capacity, the outside temperature rises and the refrigerant pressure on the high-pressure side of the refrigerant circuit 8 increases, causing overload to the compressor 1 and damage to the AC power supply 38. When there is a voltage fluctuation and the power supply voltage drops by about 10%, the operating current of the drive motor CM increases. As shown in FIG. 7, when the operating current of the drive motor CM of the compressor 1 exceeds 265A, the current comparator 52 first
Issue a set command to 3. When the timer device 53 finishes counting for 3 seconds and times out, the current comparison device 52 again checks whether the operating current exceeds 265A. The reason for reconfirming after 3 seconds is to exclude cases where the operating current of the drive motor CM increases instantaneously, such as when switching the compression capacity of the compressor 1. In this case, the operating current continues to exceed 265A, so
The current comparison device 52 outputs an output A to the control signal generation device 50, and the control signal generation device 50 outputs output ports P3 to P6 regardless of the output of the temperature comparison device 51.
A control signal [1, 1, 1, 0] is generated from the compressor 1 to operate the compressor 1 at 75% compression capacity, and a reset command is issued to the timer device 53.
It also issues a set command to the timer device 54. By switching the compressor 1 from 100% operation to 75% operation, the load on the compressor 1 and the drive motor CM is reduced, and the operating current of the drive motor CM rapidly decreases as shown in the figure. When the timer device 53 times up three seconds later, the current comparator 52 calculates the return current value based on the current operating current value. That is, if the operating current value is 212A, the return current value will be 207A, which is 5A less. As a result, the current comparator 52 has a timer device 54 of 10
After completing the time count of 1 minute, a time-up command is issued, and the output A is supplied to the control signal generator 50 until the operating current becomes lower than the return current, and the compressor 1 is
Continue 75% compression capacity operation. Therefore, if the cause of the increase in the operating current of the drive motor CM is a temporary increase in high pressure in the refrigerant circuit 8 or a fluctuation in the power supply voltage, the operating current may fall below the return current while the timer device 54 is counting time. 75% operation continues until the timer device 54 times out. In addition, if the cause of the increased operating current does not go away for a long time, the operation will continue at 75% even after the timer device 54 times out, causing the outside temperature to drop and the high pressure in the refrigerant circuit 8 to drop, or to cause the power supply voltage to drop. When the operating current returns to a steady value and the cause of the increase in operating current disappears, and the operating current falls below the recovery current, 75% operation ends and returns to 100% operation. When the compressor 1 is operating at a small capacity of 75% or less, the above-mentioned capacity change control is not performed even if the operating current exceeds 265A. In this way, when the compressor 1 is operating at a small capacity, the operating current of the drive motor CM is
If the value exceeds 265A, it is possible that there is an extremely abnormal condition such as a failure of the blower 15 or a restriction of the drive motor CM. Therefore, the current comparator 52 issues an output B to the control signal generator 50 when the operating current exceeds 295A, and the control signal generator 50 issues a "0" signal from the output port P2 to stop the blower 15 and output Control signals [0, 0, 0, 0] are issued from ports P3 to P6 to stop the compressor 1, and a "1" signal is issued from output port P7 to light up the alarm lamp 36 to indicate an abnormal condition. . Also, the same control is performed when the operating current exceeds 295A during the aforementioned small capacity operation switching from 100% to 75%. This state is canceled when the abnormality is repaired and a reset key (not shown) is pressed. During the heating period when the cooling/heating changeover switch 22 is closed, the control signal generator 50 emits a "1" signal from the output port P1 to excite the control relay 29 in response to the heating command from the cooling/heating command device 45, and the four-way valve excitation relay 39 is activated. The four-way valve 2 is switched to the broken line state by being energized. The temperature comparator 51 then compares the secondary refrigerant temperature stored in the storage device 46 with the setting value for heating in the storage device 47, and instructs the control signal generator 50 to obtain the characteristics shown in FIG. Since it outputs and controls the compression capacity of compressor 1,
The degree of heating of the secondary refrigerant in the user-side heat exchanger 6 is adjusted, and the fan coil 18 performs an appropriate heating operation. In this case as well, if the operating current of drive motor CM exceeds the first set value (265A) while compressor 1 is operating at 100% compression capacity, compressor control similar to that during cooling is performed, and compressor 1 and To reduce the load on the drive motor CM so that operation can continue. Also, if the operating current exceeds the second set value (295A) during small capacity operation of 75% or less, it is the same as when cooling. Note that each of the above-mentioned setting values is appropriately selected depending on the model used, and is not limited to the numerical values shown in the figure. (G) Effects of the Invention The control method of the present invention allows the operating capacity of a compressor whose operating capacity can be changed to be set based on the load temperature, thereby directly setting the operating capacity in accordance with load temperature fluctuations. Therefore, it is possible to keep the temperature fluctuation range of the load small, and it is also possible to save energy by not using excess operating capacity. In addition, since the current flowing through the compressor drive motor is detected, if the current increases rapidly during overload and this current value exceeds the first set value, the operating capacity of the compressor is reduced and the current does not increase any further. This prevents burnout of the drive motor. After this, that is, after a certain period of time has elapsed, if the current value falls below the second set value, the operating capacity of the compressor is increased again. At the same time as preventing chattering operation, if the cause of the overload is resolved and the current flowing to the motor is reduced after a certain period of time, the operating capacity of the compressor is increased and the range of temperature fluctuations of the load is reduced. Stabilize load temperature. Therefore, it is possible to prevent shortening of the life of the refrigerator due to the chattering operation that occurs due to changes in the current value that increase or decrease in response to increases and decreases in the operating capacity of the compressor, and to stabilize the load temperature at the same time. In addition to adjusting the operating capacity according to the load temperature, it is possible to constantly reduce load temperature fluctuations. If the cause of the overload has not been resolved after a certain period of time, the current of the drive motor will increase again due to the increased operating capacity of the compressor, which will reduce the operating capacity again to prevent motor burnout. Can be done. Therefore, by using the control method of the present invention, the operating capacity of the compressor can be controlled from two sides: the temperature of the load and the current flowing through the drive motor of the compressor. This allows the range of temperature fluctuations in the load to be kept to a minimum at all times, and also prevents the life of the compressor from shortening.

[Brief explanation of drawings]

FIG. 1 is a refrigerant circuit diagram showing an example of a refrigerator to which the present invention can be applied, FIGS. 2 and 3 are electric circuit diagrams showing an example of using the method of the present invention, and FIG. A block diagram showing an example of the internal system of the microcomputer shown in the figure, and FIGS. 5 to 7 are explanatory diagrams for explaining the operation of the apparatus using the present invention. DESCRIPTION OF SYMBOLS 1... Compressor, 3... Heat source side heat exchanger, 5... Pressure reduction device, 6... Utilization side heat exchanger, 8... Refrigerant circuit, 20...
Microcomputer, 25... Operating current measurement circuit, 50... Control signal generator, 52... Current comparator, CM... Compressor drive motor.

Claims (1)

[Claims] 1. In a refrigerator equipped with a refrigerant circuit that connects an electric compressor with variable operating capacity, a heat source side heat exchanger, a pressure reducing device, and a user side heat exchanger installed on the load side, comprising a capacity control unit that changes the operating capacity of the compressor based on temperature;
outputting a signal for reducing the operating capacity of the compressor to the capacity control unit when the value of the current flowing through the drive motor of the compressor once exceeds a first set value, while a certain period of time has elapsed since the output of the signal; Afterwards, when the value of the current once falls below a second set value that is lower than the first set value, a signal for increasing the operating capacity of the compressor is output to the capacity control section. Control method.