JPH0549905B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a method for controlling the capacity of a refrigeration system used in a heat pump air conditioner, a show case refrigerator, or the like.

(b) Conventional technology An air conditioner equipped with a variable-capacity compressor whose operating frequency is varied in steps using a frequency converter (inverter device) was developed, for example, in the 1980s.
As disclosed in Publication No. 12532, in general, in this type of air conditioner, the variable speed of the operating frequency is set constant at the start of operation and during normal operation after this start, and especially at the start of operation, the variable speed of the operating frequency is set constant. Currently, the variable speed of the operating frequency is set quickly to reach the highest frequency as quickly as possible so that the room is cooled and heated.

In addition, a pressure sensor is provided to detect high-pressure refrigerant pressure, so that when the refrigerant pressure exceeds a set value during heating, for example, an increase in operating frequency is suppressed, and a high-pressure protection switch is installed to prevent the compressor from stopping frequently.

(c) Problems to be solved by the invention Since a pressure sensor is required, cost increases are unavoidable.For this reason, in heat pump type air conditioners, heat pumps are used to prevent cold air during heating and to prevent evaporation from freezing during cooling. Attempts were also made to use the temperature sensor attached to the exchanger to suppress the increase in operating frequency, but the rate of increase in refrigerant pressure was faster than the rate of increase in refrigerant temperature, so the increase in operating frequency was The high-pressure refrigerant pressure rises quickly before the rise can be suppressed, causing the high-pressure protection switch to operate, causing the compressor to frequently stop.

In view of this problem, the present invention provides a method for controlling the capacity of a refrigeration system that can reliably suppress an increase in operating frequency even with a temperature sensor attached to the refrigeration system.

(d) Means for Solving the Problems The present invention sets the variable speed (frequency/second) of the operating frequency during the startup operation of the compressor based on the refrigeration load after the completion of the startup operation, so that the operating frequency during normal operation is changed. The speed is set faster than the variable speed.

(E) Effect During start-up operation, the operating frequency increases at a fast speed of, for example, 2 Hz/1 second and reaches the maximum operating frequency of 90 Hz in a short time, so the room is rapidly cooled and heated with maximum cooling and heating capacity. . When the maximum operating frequency of 90Hz is reached and normal operation starts based on the heating and cooling load after the start-up operation is completed, the variable speed of the operating frequency changes to 2Hz/30 seconds, and from then on, the indoor temperature and room temperature set value are maintained at this slow speed. Since the operating frequency is gradually changed between 50Hz and 90Hz depending on the difference between the Even at traffic lights, the compressor does not stop frequently because the increase in operating frequency is reliably suppressed.

(F) Example Fig. 1 is a flowchart showing the capacity control method of the device of the present invention, and Fig. 2 is a heat pump type refrigerant circuit diagram of the device of the present invention, in which the operating frequency is variable by a frequency converter in the controller 1. FIG. 2 shows a variable capacity refrigerant compressor 2, a four-way valve 3 for switching between cooling and heating channels, an indoor heat exchanger 4, a pressure reducing element 5 such as a capillary tube, and an outdoor heat exchanger 6. During heating operation, the four-way valve 3 is set to the solid line state, and the refrigerant discharged from the compressor 2 is routed from the indoor heat exchanger 4 to the outdoor heat exchanger 6. During cooling operation, the four-way valve 3 is connected to the solid line state. 3 is switched to the broken line state so that the discharged refrigerant flows reversely from the outdoor heat exchanger 6 to the indoor heat exchanger 4.

Furthermore, the discharge pipe 7 of the compressor 2 is equipped with a high pressure protection switch 8, and the suction pipe 9 is equipped with a low pressure protection switch 10.
However, both are provided to protect the compressor 2, and the indoor heat exchanger 4 is provided with a temperature sensor 11 that detects the refrigerant temperature to prevent cold air during heating operation and to prevent freezing during cooling operation. ing.

Signals from these protection switches 8, 10 and temperature sensor 11 are input to the controller 1, and the compressor 2 is controlled at the operating frequency according to the flowchart in Figure 1 (showing an example during heating operation). It is becoming more and more common.

This control method will be explained below. When the operation switch is first turned on, the operating frequency of the compressor 2 is set to 2Hz/1 second (T ₁ = 1 second) by the signal from the controller 1.
Since the compressor 2 is started at an extremely fast rising speed and reaches the maximum operating frequency of 90 Hz in a short time (during the start-up operation of the compressor 2), heating of the room is rapidly started with the compressor 2 operating at its maximum capacity. If it takes 30 minutes or more for the operating frequency to reach 90 Hz due to fluctuations in the power supply voltage, etc., the increase in the operating frequency will be stopped at this time-up point.

Then, when normal operation starts based on the refrigeration load after this start-up operation is completed, the variable speed of the operating frequency is set to 2 Hz/30 seconds (T ₂
= 30 seconds), and if the temperature difference between the room temperature and the set temperature is 3℃ ((△t ₁ ) or more, it will be 90Hz, and if the temperature difference is between 3℃ and 2℃ (=△t ₂ ) The time is 70Hz,
50 when the temperature difference is between 2℃ and 1℃ (=△t ₃ )
Compressor 2 is operated at Hz.

During such operation, the temperature of the refrigerant in the indoor heat exchanger 4 is
Check temperature sensor 1 to see if it has reached 58℃ (=t ₁ )
If the refrigerant temperature is below 58℃, the compressor 2 will be operated at the operating frequency set as described above based on the temperature difference between the room temperature and the set temperature. From 70Hz to 90Hz
If it rises to , it will change slowly even with the variable speed 2Hz/30 seconds set as mentioned above,
The high pressure protection switch 8 will not operate due to a sudden rise in high pressure.

Next, the refrigerant temperature of the indoor heat exchanger 4 is 58℃ and 60℃.
℃ (=t ₂ ), the controller 1 receives the signal from the temperature sensor 11 and determines whether the operating frequency is higher than or equal to t 2 .
It is controlled so that the refrigerant temperature does not rise, and if this refrigerant temperature
When the temperature exceeds 60 degrees, the controller 1 lowers the operating frequency in 2 Hz steps to control the refrigerant temperature to 58 degrees Celsius or less.

The above has been explained using heating operation as an example, but in the case of cooling operation as well, the variable speed of the operating frequency is set to 2Hz/1 second during the startup operation of compressor 2, and the variable speed is set to 2Hz/1 second during the startup operation of the compressor 2, and the normal speed is set based on the refrigeration load after the startup operation is completed. 2 when I start driving
By setting it to Hz/30 seconds, the room will be rapidly cooled when the compressor 2 is operated at its maximum capacity, and when the operating frequency increases from 50Hz to 70HzΩ and further to 90Hz due to the temperature difference between the room temperature and the set temperature. Since the speed changes slowly, the low-pressure refrigerant pressure will not drop suddenly and the low-pressure protection switch 10 will not work, and the refrigerant temperature in the indoor heat exchanger 4 will drop to 0°C and freeze. If so, controller 1
is controlled to stop increasing the operating frequency or to lower the operating frequency in 2 Hz steps in response to a signal from the temperature sensor 11.

In the above embodiment, a heat pump type air conditioner was described, but the high pressure protection switch 8 and the four-way valve 3
It can also be applied to air conditioners and case cases that do not have In addition, although the explanation was given using step control in which the operating frequency changes in steps of 2 Hz, it can also be applied to a control method in which the operating frequency changes linearly.In this case, the slope of the characteristic straight line of the operating frequency against time is increased at startup, It is best to make it smaller during normal operation later.

(G) Effects of the Invention According to the present invention, the speed (frequency/second) of changing the operating frequency of the compressor is fast during the startup operation of the compressor, and then becomes normal based on the refrigeration load after the startup operation is completed. Since the operation time is set to be slower than during this start-up operation, cooling and heating will start rapidly at high capacity during the start-up operation, and during normal operation based on the refrigeration load after this start-up operation is completed, the operating frequency will be reduced. Since the refrigerant pressure rises slowly (slowly), the high-pressure (low-pressure) refrigerant pressure does not rise (fall) suddenly. Therefore, even a refrigerant temperature sensor installed for the purpose of preventing cold air or freezing can prevent an increase in the operating frequency. It can be fully utilized as a signal source to stop the compressor, and the high pressure (low pressure) protection switch can prevent the compressor from frequently stopping due to sudden pressure fluctuations.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing the capacity control method of the apparatus of the present invention, and FIG. 2 is a heat pump type refrigerant circuit diagram of the apparatus of the present invention. 1...Controller, 2...Refrigerant compressor, 8...High pressure protection switch, 10...Low pressure protection switch, 11
...Temperature sensor.

Claims (1)

[Claims] 1. In a refrigeration system equipped with a variable capacity refrigerant compressor whose operating frequency is varied by a frequency converter,
Capacity control of a refrigeration system characterized in that the variable speed of the operating frequency during the startup operation of the compressor is set faster than the variable speed of the operating frequency during normal operation based on the refrigeration load after the completion of the startup operation. Method.