JPH0427398B2 - - Google Patents

Description

[Detailed description of the invention]

(a) Industrial Application Field The present invention relates to a control device for a multi-refrigerator. (B) Conventional technology A conventional multi-refrigerator is equipped with a low pressure switch with a different set pressure for each compressor, and the compressors are sequentially stopped when the suction pressure decreases, and are started sequentially when the suction pressure increases. There is. (C) Problems to be Solved by the Invention However, since conventional multi-refrigerators are provided with a low pressure switch for each compressor, it is difficult to set and adjust these low pressure switches, and it is difficult to adjust the set pressure of the low pressure switch. Compressors are stopped in order of low pressure, and the operating compressors have low low pressure and are operated inefficiently, and the order in which compressors are stopped is determined by the settings of each low pressure switch. There were problems such as: The present invention is intended to solve the above-mentioned problems, and an object of the present invention is to provide a multi-refrigerator in which operation of each compressor can be stopped at the same pressure range. (d) Means for Solving the Problems The present invention provides a condensing unit including a condenser and a plurality of compressors of different capacities connected in parallel, and a load side unit including an evaporator. A refrigeration cycle is constructed by connecting the refrigerant with piping, and the combination of these compressors is changed depending on the load of the load side unit. a pressure sensing means for sensing a common suction pressure, a pressure setting means for setting the suction pressure to a predetermined range between an upper limit value and a lower limit value, and a pressure set by the pressure setting means and a pressure detected by the pressure sensing means. a compressor capacity converting means for changing the operation combination of the compressor according to a signal from the comparison means; The device is equipped with a delay means that enables activation after being stopped. (e) Effect By having the present invention configured as described above, the common suction pressure of the refrigerant sucked into each compressor is compared with a set pressure, and the operation combination of the respective compressors is changed, The capacity of each compressor is controlled using the same suction pressure, and the number of capacity control steps for each compressor described above can be increased using fewer compressors. (F) Embodiments The present invention will now be explained based on embodiments shown in FIGS. 1 to 3. 1 is a refrigeration cycle, and this refrigeration cycle consists of a condensing unit 6 that combines three compressors 2, 3, and 4 with different capacities, a condenser 5, etc., an expansion valve 7, an evaporation side load 8, and the evaporator. A pressure sensing element 10 detects the pressure of a common suction pipe 9 between the side load and each compressor 2, 3, 4, and the capacity of each compressor 2, 3, 4 is adjusted by this pressure sensing element. It is constituted by a control circuit 11. Three compressors 2, 3, and 4 with capacities of 7.5 HP, 10 HP, and 15 HP are combined to form a condensing unit 6. The pressure sensing element 10 outputs a voltage corresponding to the pressure detected within the common suction pipe 9. The control circuit 11 includes a voltage setting element 1 that sets the set pressure width to an optimum low pressure value range that reduces the temperature change on the load side between the upper limit _P1 and the lower limit _P2 .
2, and first and second comparators 1 that compare the set voltage value of this voltage setting element and the voltage of the pressure sensing element 10.
3 and 14, first and second AND circuits 15 and 16 which operate according to the output state of this comparator, and this first and second AND circuits 15 and 16,
a counter 17 operated by the second AND circuit and the clock signal from the clock circuit 32; first and second OR circuits 18 that limit the output range of this counter;
19, a third AND circuit 20, an inverter 21 that creates a preset signal to keep the output of the counter 17 constant when the power is turned on, and an output from the counter 17 for changing the combined operating capacity of the compressors 2, 3, and 4. a decoder 22 which outputs an output of
25, first, second, and third delay timer circuits 26, 27, and 28 that enable each compressor 2, 3, and 4 to be started after being stopped for a predetermined period of time, and compressors 2, 3, and 4.
The first magnetic switch that drives the operating magnetic switch.
It is composed of second and third relays 29, 30, and 31. The first and second AND circuits 15 and 16, the counter 17, the first and second OR circuits 18 and 19, the third AND circuit 20, the inverter 21, and the decoder 22 combine the operation of the compressors 2, 3, and 4. It constitutes a control circuit that changes the ability of In the multi-refrigerator control device configured in this way, the three compressors 2, 3, and 4 that make up the refrigeration cycle 1 perform combined operation as shown in Table 1.

[Table] However, 1 indicates the operating state. 0 indicates a stopped state.
The first and second AND circuits 15 and 16 connect the voltage output corresponding to the pressure detected by the pressure sensing element 10 and the voltage of the upper and lower limit set voltage values of the voltage setting element 12 to the first comparator 13. The signals are compared with the second comparator 14 and output as shown in Table 2.

[Table] However, 1 means output, 0 means no output. If the low pressure exceeds the upper limit of the set pressure _P1 ,
The first and second comparators 13 and 14 output an output of 1,
The counter 17 outputs 1 from the second AND circuit 16.
A count-up is performed to increase the combined capacity of compressors 2, 3, and 4. Then, the third to fifth OR circuits 23,
24 and 25 to operate the first to third relays 2.
The necessary compressors 2, 3, and 4 are operated at 9, 30, and 31. After the first to third delay timer circuits 26, 27, and 28 are stopped for a predetermined time,
Each compressor 2, 3, and 4 is restarted. Also, if the low pressure is within the set pressure range,
The second comparator 14 outputs 1, the first AND circuit 15 outputs 1, the first OR circuit 18 outputs a signal to the counter 17 to prohibit up-down operation, and the compressors 2, 3, and 4 remain unchanged. I try to drive under these conditions. When the low pressure falls below the lower limit of the set pressure _P2 , the first and second comparators 13 and 1
4, the output becomes 0, and the counter 17 indicates that the compressor 2,
A countdown is performed to reduce the combined capacity of 3 and 4. Then, the decoder 22 operates the third to fifth OR circuits 23, 24, and 25 to operate the combined capacity one stage lower, and the first to third relays 29, 30, and 31 operate the necessary compressor 2. , 3, and 4 are operated. The third AND circuit 20 connects three compressors 2, 3, and 4.
are operated together, and the low pressure is at the upper limit of the set pressure.
When the second AND circuit 16 outputs an output of 1 in a state where _P1 is exceeded, the output of 1 is output and the count-up operation of the counter 17 is prohibited. The second OR circuit 19 connects three compressors 2, 3, and 4.
both stop, and the outputs of the first and second comparators 13 and 14 and the first and second AND circuits 15 and 16 are both 0 and output 1 to prohibit the countdown operation. The first OR circuit 18 is configured to give a signal to the counter 17 that prohibits the combination of operation of the compressors 2, 3, and 4 from changing based on the outputs of the first and third AND circuits 15 and 20 and the second OR circuit 19. ing. The decoder 22 converts the signal generated by the counter 17 into a signal of 8 stages from 0 to 7, and changes the combination of the outputs of the third to fifth OR circuits 23, 24, 25 at each stage. , 4, the combined capacity is changed. 3rd to 3rd
The signal of the decoder 22 outputted to the 5OR circuits 23, 24, and 25 changes in synchronization with the cycle of the clock signal of the counter 17. Here, to explain the operating status of the capacity control of the compressors 2, 3, and 4 using the time chart shown in FIG. 3, at the beginning of operation, the low pressure exceeds the upper limit _P1 of the set pressure of the voltage setting element 12, The three compressors 2, 3, and 4 continue to operate at full load of 32.5 HP, and continue to operate at the same capacity until the low pressure falls below the lower limit _P2 of the set pressure. When the low pressure falls below the lower limit _P2 of the set pressure, the first and second comparators 13 and 14 and the first and second AND circuits 15,
16 becomes 0 and synchronizes with the cycle of the clock signal of the counter 17, and this counter generates a countdown signal to stop the 7.5 HP compressor 2 and operate at a capacity of 25 HP. Even if the operating capacity of compressors 2, 3, and 4 decreases, if it remains below the lower limit P ₂ of the low pressure setting pressure,
In synchronization with the next clock signal of the counter 17, this counter generates a countdown signal again and enters the 22.5 HP capacity operation of the next lower class, but the 7.5 HP compressor 2 has not stopped for a predetermined time. Therefore, 15 HP compressor 4 is operated independently.
After the 7.5 HP compressor 2 has stopped for a predetermined time, the 7.5 HP
Compressor 2 starts operating, and combined with compressor 4 of 15 HP, the capacity is 22.5 HP.
In this state, when the low pressure exceeds the upper limit _P1 of the set pressure, the first and second comparators 13 and 14 and the second AND circuit 16 output an output of 1 in synchronization with the clock signal.
It enters the upper class 25HP capacity operation. At this time
Since the 10HP compressor 3 is stopped for a specified period of time,
It switches at the same time as the 7.5HP compressor 2. When the low pressure suddenly falls from within the set pressure range to below the lower limit _P2 , the system tries to switch to the one step lower capacity operation, but continues to operate at a capacity of 25 HP until it synchronizes with the clock signal, and then synchronizes with the clock signal. When this happens, the system switches to 22.5 HP capacity operation, but since the 7.5 HP compressor 2 has not stopped for a specified period of time, the 15 HP compressor 4 operates independently, and at the next clock signal, the low pressure reaches the lower limit of the set pressure P. If it is below ₂ , 17.5HP
countdown to capacity operation. 17.5HP capacity operation is 7.5HP compressor 2 and 10HP compressor 3
15 HP compressor 4 stopped due to the combination with
Since the other compressors 2 and 3 have not stopped for a predetermined period of time, the three compressors 2, 3, and 4 are in a stopped state,
The 7.5 HP compressor 2, which has been stopped for a predetermined period of time, starts operating first, and then the 10 HP compressor 3 starts operating. In this way, there is a time lag between the capacity of the operation command and the actual capacity, but this time lag prevents each compressor 2, 3, and 4 from repeatedly turning on and off in short cycles. I'm trying to protect it. Incidentally, the up-down prohibition signal is transmitted between the decoder 22 and the
It can also be generated by outputting from the 2AND circuit 16. (G) Effects of the Invention As described above, according to the present invention, there is provided one pressure sensing means for sensing the suction pressure of refrigerant sucked into a plurality of compressors having different capacities, and a suction pressure that is set to an upper limit value and a lower limit value. a pressure setting means for setting the pressure to a predetermined width, and a comparison means for comparing the pressure set by the pressure setting means and the pressure detected by the pressure sensing means;
Compressor capacity conversion means for changing the operating combination of the compressors according to the signal from the comparison means;
Since the compressor is provided with a delay means that enables the compressors to be stopped for a predetermined period of time and then started, the number of compressors is controlled at the same set pressure at a low pressure. This allows each compressor to operate efficiently regardless of the operating status of capacity control, and allows fine control of refrigeration capacity in response to load fluctuations by using compressors with different capacities. This is how it was done. In addition, the delay means enables each compressor to be started after it has been stopped for a predetermined period of time, thereby preventing on/off control of each compressor in a short cycle and protecting each compressor. It is.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a refrigeration cycle showing an embodiment of the present invention, Fig. 2 is a block diagram of a control circuit of the invention, and Fig. 3 is a time chart showing the operating status of each compressor. . 1... Refrigeration cycle, 2, 3, 4... Compressor, 10
...Pressure sensing element, 11... Control circuit, 12... Voltage setting element, 13, 14... Comparator, 26, 27, 28
...delay timer circuit.

Claims (1)

[Claims] 1. A refrigeration cycle is configured by connecting a condensing unit with a condenser and a plurality of compressors of different capacities connected in parallel to a load-side unit equipped with an evaporator, and In a system that operates by changing the combination of these compressors depending on the load amount of the side unit, one pressure sensing means for sensing the suction pressure of the refrigerant sucked into each compressor; a pressure setting means for setting the pressure to a predetermined range between an upper limit value and a lower limit value; a comparison means for comparing the pressure set by the pressure setting means with the pressure detected by the pressure sensing means; compressor capacity converting means for changing the operating combination of the compressors according to the signal; and delay means for enabling the compressor to be started after being stopped for a predetermined period of time depending on the operating combination. A control device for a multi-refrigeration machine characterized by comprising: