JPH0145029Y2 - - Google Patents

Description

[Detailed description of the invention] <Technical field> The present invention is a refrigerator-freezer that cools the interior of a freezer compartment, a refrigerator compartment, etc. using a refrigeration cycle that includes an electric compressor, a pressure reducing valve (capillary tube), and an evaporator. It is related to.

<Prior art> In conventional refrigerator-freezers, a constant-speed induction motor is often used as the motor for driving the compressor, and the operation and stop of the motor are controlled according to the difference between the internal temperature and the set temperature. Ta. Figure 8 shows the temperature change inside the refrigerator when operating at a commercial power frequency of 50Hz and 60Hz, where Tf indicates the temperature inside the refrigerator and Ts indicates the set temperature. As is clear from this figure, the temperature inside the refrigerator begins to hunt due to intermittent operation with a certain hysteresis. In this type of control method, (a) the motor starts and stops in a complicated manner, and a large current flows during startup, shortening the life of the motor and compressor; (b) noise is generated when starting and stopping; (c) When the motor is stopped, the refrigerant does not flow to the heat exchanger, so it is wasted. (d) The high-temperature, high-pressure refrigerant in the condenser flows backwards, requiring an increase in power consumption to raise the pressure again when the motor is started. It had the following drawbacks:

<Purpose> In view of the above, the present invention aims to provide a refrigerator-freezer that uses a variable frequency electric compressor and is capable of controlling the temperature inside the refrigerator to a set temperature in response to a wide range of loads. It is.

<Embodiment> An embodiment of the present invention will be described below with reference to FIGS. 1 to 7. The refrigerator-freezer according to the present invention includes an electric compressor 1 for compressing refrigerant with a variable operating frequency. , a control device 2 that controls the operating frequency of the electric compressor 1, and the control device 2 includes an internal temperature detector 3 that detects the internal temperature of the refrigerator, and an internal temperature detector 3 that detects the internal temperature of the refrigerator. A setting device 4 is provided,
The control device 2 detects the load condition in the refrigerator based on the output signals of the refrigerator temperature detector 3 and the refrigerator temperature setting device 4, and operates the electric compressor 1 in continuous operation when the load is large and when the load is small. It is configured to automatically control the temperature to a set temperature during intermittent operation.

The control device 2 includes an internal temperature detector 3 consisting of a thermistor, an internal temperature setting device 4, and a temperature difference detector 5 that detects a temperature difference between the internal temperature and the set temperature.
, a frequency selector 6 that sets the frequency including operation stop based on the output signal of the detector 5, and a frequency control signal generator 7 that outputs a frequency control signal to the electric compressor 1. . The electric compressor 1 includes a compressor 8, an electric motor 9, and a frequency control drive unit 10 that receives the control command and controls the electric motor 9.

Next, to describe the control method, the temperature difference detector 5 detects the difference between the freezer compartment temperature detected by the compartment temperature detector 3 and the temperature set by the compartment temperature setter 4.
The frequency selector 6 determines the rotational speed of the electric compressor 1 according to the temperature deviation using the corresponding example shown in FIG.

Figure 6 shows the difference (Ts -
Tf), that is, the deviation ΔT, is shown on the horizontal axis, and feedback control is performed according to the flowchart in FIG. 2 until the deviation becomes zero. That is, when the deviation is negative, that is, when the internal temperature Tf is higher than the set temperature Ts, the frequency F is controlled to increase, and when the deviation is positive, that is, when the internal temperature Tf is higher than the set temperature Ts.
If it is lower than Ts, the frequency F is controlled to be lowered to make the deviation zero. FIG. 4 shows a state in which the cooling power is adjusted by varying the frequency according to the deviation, and as is clear from this figure, the temperature in the freezer compartment hardly changes and remains constant.

However, this frequency control during continuous operation can only be performed when the frequency F is between Fmin and Fmax; in other cases, especially when the frequency is below Fmin, intermittent operation is required as described below. There must be.

FIG. 3 shows the relationship between the frequency of the compressor driving electric motor 9 and the refrigerating capacity. Qmin is the refrigeration capacity for frequency Fmin, and Qmax is the refrigeration capacity for Fmax.
shall be. For reference, frequencies F50 and F60 indicate commercial power frequencies of 50Hz and 60Hz, and the corresponding refrigeration capacities are indicated as Q50 and Q60. When the freezer load is smaller than Qmin as shown in Figure 3, the internal temperature Tf will be lower than the set value Ts by ΔT, as a deviation from ΔT will occur even if the frequency is Fmin, as shown by the broken line in Figure 6. settles to a low value. Therefore, as shown in Fig. 7, when the frequency is Fmin and ΔT2 or more, the compressor 8 is stopped, and then when the temperature rises to ΔT1 above the set temperature Ts,
That is, when the internal temperature Tf becomes higher than the set temperature Ts by ΔT1, the operation of the compressor 8 is restarted, and the frequency of the compressor motor 9 is increased according to the deviation ΔT1.
After that, the frequency is changed so that the deviation becomes zero above the frequency Fmin. Even if the frequency is Fmin, the internal temperature Tf becomes lower than the set temperature Ts,
When the temperature reaches ΔT2, the compressor 8 is stopped. Thereafter, the intermittent operation as described above is repeated.

FIG. 5 shows an intermittent operating state when the lower limit of the frequency is Fmin and the refrigerating load is smaller than the refrigerating capacity Qmin. By appropriately determining the deviations ΔT1 and ΔT2 in this manner and inputting them to the frequency selector 6, the amplitude of fluctuation can be made small and equal to the temperature inside the refrigerator even during intermittent operation.

<Effects> As is clear from the above description, the present invention includes an electric compressor for compressing refrigerant whose operating frequency is variable, and a control device for controlling the operating frequency of the electric compressor. includes an internal temperature detector for detecting the internal temperature, an internal temperature setting device for setting the internal temperature, a temperature difference detector for detecting the temperature difference between the internal temperature and the set temperature, and a temperature difference detector for detecting the temperature difference between the internal temperature and the set temperature. The electric compressor is provided with a frequency selector that sets a frequency including operation stoppage based on an output signal from the compressor, and a frequency control signal generator that outputs a frequency control signal to the electric compressor.

Therefore, according to the present invention, by operating the electric compressor while changing its refrigerating capacity by making the frequency variable, it is possible to reduce the number of times the electric compressor starts and stops, thereby extending its life and eliminating the discomfort caused by starting and stopping. It is possible to prevent the generation of noise, it is possible to increase the cooling responsiveness to load fluctuations, and it is also possible to save energy because the heat exchanger can be used effectively.

Furthermore, in this invention, the frequency selector uses the difference between the detected temperature in the freezer compartment and the set temperature in the freezer compartment as a deviation, and on both sides of the set temperature, there is a positive deviation value where the temperature inside the refrigerator is lower than the set temperature. If the temperature is set to a negative deviation value higher than the set temperature and the operating frequency is between the highest frequency and the lowest frequency, a signal is output that changes the frequency according to the deviation between the internal temperature and the set temperature. With the continuous operation function, if the operating frequency is the lowest frequency and the temperature inside the refrigerator is lower than the set temperature by more than the positive deviation value, the electric compressor will be stopped, and if the temperature inside the refrigerator is higher than the set temperature by the negative deviation value or more, the electric compressor will be stopped. It has an intermittent operation function that outputs a signal to restart the electric compressor.

Therefore, when the load is small (intermittent operation), the set temperature fluctuates in the range of positive and negative deviation values, so the average value is equal to the set temperature, as shown in Figures 4 and 5. Since it essentially controls the temperature, it has the advantage of being extremely responsive to disturbances.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the refrigerator-freezer of the present invention, Fig. 2 is a control flowchart thereof, Fig. 3 is a diagram showing the relationship between the frequency of the compressor motor and the refrigerating capacity, and Fig. 4 is a diagram showing the relationship between the frequency of the compressor motor and the refrigerating capacity. Figure 5 shows the temporal change in refrigerator temperature during continuous operation, Figure 5 shows the temporal change in refrigerator temperature during intermittent operation, and Figure 6 shows the temperature in the refrigerator versus the frequency of the electric compressor and the set temperature. Figure 7 is a diagram showing the command method for stopping operation during intermittent operation. Figure 8 is a diagram showing the temperature control status of a conventional refrigerator-freezer operating at a motor frequency of 50Hz or 60Hz. It is. 1...Electric compressor, 2...Frequency control device, 3
...Inner temperature detector, 4...Inner temperature setting device, 5
...Temperature difference detector, 6...Frequency selector, 7...
Frequency control signal generator, 8... Compressor, 9... Electric motor, 10... Frequency control drive section.

Claims (1)

[Scope of utility model registration request] It includes an electric compressor 1 for compressing refrigerant whose operating frequency is variable, and a control device 2 that controls the operating frequency of the electric compressor 1. A detector 3, an internal temperature setting device 4 for setting the internal temperature, and a temperature difference detector 5 for detecting the temperature difference between the internal temperature and the set temperature, and the operation is stopped by the output signal of the detector 5. A frequency selector 6 that sets a frequency including a frequency, and a frequency control signal generator 7 that outputs a frequency control signal to the electric compressor 1 are provided. The difference (Ts − Tf) between ΔT2) and a negative deviation value (ΔT1) where the internal temperature (Tf) is higher than the set temperature (Ts), and when the operating frequency is between the highest frequency and the lowest frequency, the internal temperature (Tf ) and the set temperature (Ts), a continuous operation function that outputs a signal that changes the frequency according to the deviation (ΔT) from the set temperature (Ts), and a continuous operation function that outputs a signal that changes the frequency according to the deviation (ΔT) between the operating frequency and the set temperature (Ts). If the internal temperature (Tf) is higher than the set temperature (Ts) by more than the negative deviation value (ΔT1), the electric compressor 1 is stopped. A refrigerator-freezer characterized by having an intermittent operation function that outputs a restart signal.