JPH01314841A - Air conditioner - Google Patents

Abstract

PURPOSE:To prevent a compressor from hunting at the time of switching operation and to stabilize the operating state of the compressor by holding the operating frequencies of the compressors after the number of the compressors is switched at the time of switching the number of the operating compressors for a predetermined period of time. CONSTITUTION:A controller 6 calculates the difference DELTAt between the detected temperature of a diffusing temperature sensor 7 and a set value determined in an operation unit, and shifts the operation of one of first compressor 3a to the operation of two of first, second compressors 3a, 3b as the difference DELTAt increases. In this case, the operating frequences of the compressors 3a, 3b after the number of the operating compressors is shifted by the controller 6 is maintained for a predetermined period of time. As the temperature difference DELTAt decreases, the operation of two of the compressors 3a, 3b is shifted to the operation of one of the compressor 3a. In this case, the operating frequencies of the compressors 3a, 3b after the number of the operating compressors is shifted by the controller 6 are maintained for a predetermined period of time. Thus, the hunting at the time of switching the number of the operating compressors can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) This invention relates to an improvement in an air conditioner in which two mutually independent refrigeration cycles are connected to a common indoor heat exchanger.

(Prior Art) Generally, air conditioners have been developed in which two mutually independent refrigeration cycles are connected to a common indoor heat exchanger. In this case, a variable capacity compressor is interposed in each refrigeration cycle. Furthermore, a blowout temperature sensor is installed at the blowout port of the indoor unit housing the indoor heat exchanger, and the number of operating compressors and the operating frequency of each compressor are controlled based on the detection signal from this blowout temperature sensor. The temperature of the air blowing from the tank is kept constant.

By the way, in this type of compressor, the number of operating compressors and the operating frequency of each compressor are controlled according to the temperature blown out from the indoor unit. For example, during cooling operation, the temperature blown out from the indoor unit is higher than the set value. In this case, the capacity of the first compressor of one refrigeration cycle is increased, and furthermore, the second compressor of the other refrigeration cycle is started in addition to the first compressor that is being driven. When the temperature of the air discharged from the indoor unit approaches the set value in this state, the capacity of each compressor is reduced, and furthermore, the operation of the second compressor is stopped and only the first compressor is operated.

However, with the above configuration, there is a problem in that the temperature of the air blown from the indoor unit suddenly changes transiently when the number of operating compressors is changed. For example, when switching from a single compressor operating state to a simultaneous operating state of two compressors, the air outlet temperature from the indoor unit will drop sharply below the set value, so the air outlet temperature sensor will detect this temperature drop. Immediately after detecting this and switching from the individual operating state of only one compressor to the simultaneous operating state of two compressors, there is a possibility that the state returns to the individual operating state of only one compressor. Furthermore, from the simultaneous operation of two compressors, one
When switching to standalone operation of only one compressor, the air outlet temperature from the indoor unit will rise sharply higher than the set value, so the air outlet temperature sensor will detect this temperature rise and
Immediately after switching from the simultaneous operation state of two compressors to the independent operation state of only one compressor, there is a possibility that the state returns to the simultaneous operation state of two compressors again. Therefore, when switching the number of operating compressors, there is a risk that the second compressor will repeatedly turn on and off within a short period of time, causing a so-called hunting phenomenon, which may cause the operating state of the compressors to become unstable. there were.

(Problem to be Solved by the Invention) In the conventional configuration, when switching the number of operating compressors, the air outlet temperature of the indoor units changes suddenly and rapidly, so it is difficult to change the number of operating compressors. During the switching operation, there is a risk of causing the second compressor to turn on and off repeatedly within a short period of time, a so-called hunting phenomenon, and the operating state of the compressor may become unstable.

This invention was made in view of the above circumstances, and is an air conditioner that can prevent the hunting phenomenon of the compressor when switching the number of compressors in operation, and can stabilize the operating state of the compressor. The purpose is to provide the following.

[Structure of the Invention] (Means for Solving the Problem) Switching control of the number of operating compressors that maintains the operating frequency of each compressor for a certain period of time after switching the number of operating compressors. This means that a means has been established.

(Function) When switching the number of operating compressors based on the detection signal from the outlet temperature sensor, the operating frequency of each compressor is held for a certain period of time after the number of operating compressors is switched, so that each compression Even if the blowout temperature from the indoor unit suddenly changes transiently when changing the number of compressors in operation, the compressor will repeatedly turn on and off within a short period of time when changing the number of compressors in operation. This is designed to prevent the hunting phenomenon from occurring.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 schematically shows the overall configuration of an air conditioner in which two mutually independent refrigeration cycles 2a and 2b are connected to a common indoor heat exchanger 1.

In this case, the first refrigeration cycle 2a includes a first variable capacity compressor 3a, a first condenser 4a, and a first expansion valve 5.
Indoor heat exchangers 1 functioning as an AS evaporator are sequentially connected via refrigerant pipes. Further, the second refrigeration cycle 2b includes a second variable capacity compressor 3b, a second condenser 4b, and a second expansion valve 5b.

Indoor heat exchangers 1 functioning as evaporators are successively connected via refrigerant pipes. In this case, the indoor heat exchanger 1 includes, for example, a first refrigeration cycle 2 within a large number of common fins.
A refrigerant pipe section on the a side and a refrigerant pipe section on the second refrigeration cycle 2a side are respectively disposed.

Further, 6 is a control section of this air conditioner. This control section 6 is composed of, for example, a microcomputer and its peripheral circuits, and includes a blowout temperature sensor 7 and a first... ,
Second inverter circuit 8a.

8b and an operation section (not shown) are connected thereto, and a timer circuit 9 is built in.

In this case, the outlet temperature sensor 7 is provided at the outlet of the indoor unit housing the indoor heat exchanger 1. moreover,
Inverter circuits 8a and 8b rectify the voltage of the AC power supply,
The voltage is converted into an alternating current voltage of a predetermined frequency by switching according to a command from the control unit 6, and is supplied as driving power to the motors of the compressors 3a and 3b, respectively. Then, the control unit 6 calculates the difference Δt between the air outlet temperature and the set value Ts preset by the operation unit based on the detection signal from the air outlet temperature sensor 7, and calculates the number of operating units of each compressor 3a, 3b and the operating frequency. is controlled to keep the temperature of the air blown from the indoor unit constant. In addition, in this control section 6, when the number of operating compressors 3a, 3b is changed, the operating frequency of each compressor 3a, 3b after switching the number of operating compressors 3a, 3b is controlled by a timer circuit 9 for a certain period of time t1. I'm trying to keep it.

Next, the operation of the above configuration will be explained with reference to FIGS. 2 to 5.

First, during cooling operation, the air outlet temperature sensor 7 constantly detects the air outlet temperature from the indoor unit. At this time, the control unit 6 calculates the difference Δt between the temperature detected by the blowout temperature sensor 7 and the set value (set temperature) determined by the operation unit,
The number of operating compressors 3a, 3b and operating frequencies (output frequencies of inverter circuits 8a, 8b) fa, fb are controlled according to the temperature difference Δt. In this case, in the control section 6, as the temperature difference Δt increases, the first compressor 3a is operated from one to the first compressor 3a. He is trying to shift to operation of two second compressors 3a and 3b.

For example, if the difference Δt between the temperature detected by the outlet temperature sensor 7 and the set value (set temperature) determined by the operation section is large, first, as shown in FIG. When the operating frequency fa of the first compressor 3a is gradually increased from the minimum operating frequency (30 Hz) to the maximum operating frequency (60 Hz), the first compressor 3a is operated. The operation shifts to two second compressors 3a and 3b. When changing the number of operating compressors, the operating frequency fa of the first compressor 3a is changed from the maximum operating frequency (60 Hz) to the minimum operating frequency (30 Hz) as shown by the solid line arrow in FIG. The operating frequency fb of the compressor 3b is lower than the minimum operating frequency (30H) as shown by the dotted arrow in the figure.
Operate with z>. In this case, when switching the number of operating compressors, the control unit 6 sets the operating frequency fa (30Hz) of each compressor 3a, 3b after switching the number of operating compressors.
), fb (30Hz) is held for a certain period of time t1. Therefore, even if the temperature of the air discharged from the indoor unit suddenly decreases transiently as shown in FIG. 3 as the number of operating compressors is changed, each compressor 3a remains unchanged as in the conventional case.

When switching the number of compressors 3b in operation, the compressor 3b
It is possible to prevent the hunting phenomenon in which the power is turned on and off repeatedly.

Furthermore, this first. After switching to the operating state of the second compressors 3a and 3b, there are only two compressors 3a.

The operating frequencies fa and fb of 3b are the minimum operating frequency (30H
z), and the operating frequency fa corresponding to the temperature difference Δt between the detected temperature of the blowout temperature sensor 7 and the set value,
Two compressors 3a in fb.

3b respectively.

In addition, in the control unit 6, as the temperature difference Δt between the temperature detected by the blowout temperature sensor 7 and the set value decreases, the operation of the first and second compressors 3 a r 3 b is changed to the first compressor 3 .
Shift to single unit operation in a.

For example, the two compressors 3a and 3b are operated at an appropriate operating frequency f.
a, fb (fa >3CN1z, fb >
30Hz) to the operating frequency fa, f.
b is gradually lowered, and when the operating frequencies fa and fb of the two compressors 3a and 3b reach the minimum operating frequency (30 Hz), the operation shifts to one unit of the first compressor 3a. When switching the number of operating compressors, the operation of the second compressor 3b is stopped as shown by the dotted line arrow in FIG. 4 (the operating frequency fb is 0 Hz), and the The operating frequency fa of the No. 1 compressor 3a is changed from the minimum operating frequency (30 Hz) to the maximum operating frequency (60 Hz).

In this case as well, when switching the number of operating compressors, the control unit 6
Each compressor 3a, 3 after switching the number of operating compressors by
Operating frequency fa (60Hz) of b.

fb(O)Iz) for a certain period of time 1. let it hold. Therefore, even if the temperature of the air discharged from the indoor unit suddenly rises transiently as shown in Fig. 5 due to the switching operation of the number of operating compressors, the operation of switching the number of operating compressors 3a and 3b can be performed as usual. This can prevent the occurrence of a hunting phenomenon in which the compressor 3b is repeatedly turned on and off within a short period of time.

Further, after switching to the single operating state of the first compressor 3a, the operating frequency fa of this compressor 3a is gradually lowered from the maximum operating frequency (60H2).

Therefore, in the case of the above configuration, the blowout temperature sensor 7
During a switching operation in which the number of operating compressors 3a, 3b is switched based on a detection signal from By doing so, even if the blowout temperature from the indoor unit suddenly changes transiently when changing the number of operating compressors 3a and 3b, the It is possible to prevent the occurrence of a hunting phenomenon in which the compressor 3b repeatedly turns on and off within a short period of time, and the operating state of the compressors 3a and 3b can be stabilized.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] According to the present invention, there is provided a control means for switching the number of operating compressors that maintains the operating frequency of each compressor for a certain period of time after switching the number of operating compressors. Therefore, it is possible to prevent the nonching phenomenon of the compressor when changing the number of operating compressors, and it is possible to stabilize the operating state of the compressor.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and Fig. 1 is a schematic configuration diagram of the main parts showing the refrigeration cycle and control circuit in the air conditioner, and Fig. 2 shows switching from one unit operating state to two unit operating state. Figure 3 shows the relationship between the operating frequency of two compressors and Δt (the difference between the set value and the blowout temperature). A characteristic diagram showing the changing state. Figure 4 shows the relationship between the operating frequency of the two compressors and Δt (difference between the set value and the blowing temperature) when switching from a two-unit operating state to a one-unit operating state. FIG. 5 is a characteristic diagram showing how the blowing temperature changes when switching from a two-unit operating state to a one-unit operating state. DESCRIPTION OF SYMBOLS 1... Indoor heat exchanger, 2a... First refrigeration cycle, 2b... Second refrigeration cycle, 3a... First capacity variable compressor, 3b... Second capacity Variable compressor, 6
...Control unit, 7...Blowout temperature sensor. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 4

Claims (1)

[Claims] Two mutually independent refrigeration cycles are connected to a common indoor heat exchanger, a variable capacity compressor is interposed in each refrigeration cycle, and the indoor unit housing the indoor heat exchanger is A blowout temperature sensor is provided at the outlet, and the number of operating units and the operating frequency of each compressor are controlled based on the detection signal from the blowout temperature sensor,
In the air conditioner that maintains the blowing temperature from the indoor unit constant, when the number of operating compressors is switched, the operating frequency of each compressor is maintained for a certain period of time after switching the number of operating compressors. An air conditioner characterized by being provided with a control means for switching the number of operating units.