JPH0151754B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of operating a refrigerator in which a compressor motor is driven by an inverter device and the refrigerating capacity can be varied.

Recently, attempts have been made to control the rotational speed of a compressor in a refrigerator according to the amount of load by driving the compressor motor with an inverter device that can vary the output frequency.
However, when controlling the refrigerating capacity by controlling the output frequency of the inverter device in this way, it is important to prevent the efficiency from decreasing.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method of operating a refrigerator that can minimize the decrease in efficiency caused by starting and stopping the compressor, especially when the compressor motor is driven by an inverter device to control the refrigerating capacity. It is.

That is, in the present invention, the compressor motor is driven by an inverter device so that its speed can be controlled, and the rate of decrease in the temperature inside the refrigerator (or the temperature of the cooler) is detected while the compressor is being driven, and the rate of change is determined in advance. The speed of the compressor motor is controlled to maintain the minimum value set, thereby cooling the inside of the refrigerator as slowly as possible, thereby lengthening the start/stop cycle of the compressor and reducing losses.

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an example of a refrigeration cycle to which this explanation can be applied. In FIG. 1, 1 is a compressor, and between its discharge side and suction side is a refrigerant flow path consisting of a condenser 2, capillary tubes 3, 4, a cooler 5 for the refrigerator compartment, and a cooler 6 for the freezer compartment. A flow path consisting of a flow path switching valve 7 and a capillary tube 8 is formed in parallel with a refrigerant flow path consisting of a capillary tube 4 and a freezer compartment cooler 5. FIG. 2 shows the operating circuit of this refrigeration cycle, which consists of an inverter device 9 and a control section 10. The inverter device 9 includes an AC power source 11 and a full-wave rectifier circuit 1.
2, a smoothing capacitor 13, and an inverter main circuit 14 formed by transistors _Tr1 to _Tr6 , which are switching elements. Further, the control unit 10 includes a control circuit 15 and the transistors Tr ₁ to Tr 1 .
I memorized a control pattern for controlling Tr ₆ on and off to obtain three-phase alternating current and controlling its frequency.
By ROM (memory element) 16 and control circuit 15
The base drive circuit 17 controls the bases of the transistors Tr ₁ to _{Tr 6} based on the control pattern read from the ROM 16. 18 is a compressor motor connected to the output terminal of the inverter main circuit 14. Now, to describe the part directly corresponding to the object of the present invention, the first temperature detection element SN ₅ detects the refrigerator room temperature (or the temperature of the refrigerator compartment cooler 5).
is adapted to supply a temperature detection signal _S5 to the control circuit 15 so as to be a control element for opening and closing the flow path switching valve 7. On the other hand, a second temperature detection element SN ₆ that detects the freezing room temperature (or the temperature of the freezer compartment cooler 6) sends a temperature detection signal S ₆ in cooperation with the control circuit 15 to constitute speed control means. It is also provided to the temperature change rate determination circuit 19. The temperature change determination circuit 19 determines the temperature rise, decrease, and rate of change from the temperature detection signal _S6 , and outputs either the temperature increase change signal Su or the temperature decrease change rate signal Sd.

FIG. 3 is for explaining the control method according to the present invention, and the first quadrant of this FIG. 3 shows the temperature increase rate of change, the third quadrant shows the temperature decrease rate of change, and The magnitude of is in the relationship θ ₀ < θ ₁ < θ ₂ .

Next, the operation of the above configuration will be explained. First, to describe the general operation, during operation when the compressor motor 18 is being driven, if both the refrigerator compartment and the freezer compartment are at or above the set temperature, the flow path switching valve 7 is closed. Refrigerant is supplied to both the refrigerator compartment cooler 5 and the freezer compartment cooler 6, and when the refrigerator room temperature drops to the set value, the flow path switching valve is activated based on the temperature detection signal _S5 from the first temperature detection element _SN5 . 7 is opened and the refrigerant is supplied only to the freezer compartment cooler 6, and when the temperature drops to the set temperature, the compressor motor 18 is activated by the temperature detection signal _S6 from the temperature detection element _SN6 shown in FIG. operation will be stopped.

Next, an operating method for minimizing the rate of change in internal temperature during operation as described above will be explained with reference to FIG. 4. Let's take an example of a cycle that is supplied at the same time. At the same time as the start of this cycle, the temperature change rate determination circuit 19 is provided with freezer compartment temperature information by the second temperature detection element SN ₆ , and thereafter determines whether the temperature is rising or decreasing at appropriate sampling times, and determines the magnitude of the rate of change. (corresponding to step A in FIG. 4).
When the temperature is in the decreasing direction, the temperature decrease rate of change signal
Sd, and when the rate of change is larger than the predetermined minimum value θ ₀ in FIG. Control in direction.
Such judgment and control operations are repeated until the rate of change in temperature decrease reaches a predetermined minimum value θ ₀ (see step B). On the other hand, when the temperature is in the rising direction, the temperature change rate determination circuit 19 outputs the temperature rise change rate Su, and step C in FIG.
As shown in the figure, the output frequency of the inverter device 9 is set to Δ
Control is performed to increase the temperature step by step, and when the temperature starts to decrease due to this, the control is shifted to the above-mentioned control shown in steps A and B.

FIG. 5 shows another embodiment of the method of the invention. To explain this below, in step B, which performs frequency reduction control, when the temperature change rate is as large as -(θ ₄ to _{θ 7} ) as shown in section B ₁ , the frequency reduction unit is set to 4 times Δ, and -θ ₃ or more, and in Step C, which performs frequency increase control, when the rate of temperature change is a large value (θ ₃ - _{θ 7} ), the frequency reduction unit is set to 4 times Δ, and when θ ₂ or less, it is doubled. In this way, the unit increase/decrease value of the output frequency of the inverter device 9 is increased as the rate of temperature change increases, thereby shortening the time required to reach the predetermined minimum rate of temperature change. .

〔Effect of the invention〕

As described above, the present invention controls the speed of the compressor and thus the compressor motor so that the rate of change in temperature decreases at a predetermined minimum value during operation to lower the temperature inside the refrigerator. It is possible to provide a method of operating a refrigerator in which the discharge pressure decreases and the suction pressure conversely increases, resulting in a highly efficient operating state for the refrigerant cycle and in which the continuous operation time of the compressor becomes longer and an increase in loss due to an increase in the number of starts and stops can be avoided. It is something.

[Brief explanation of drawings]

The drawings show an embodiment to which the method of the present invention is applied. Fig. 1 is a configuration diagram of a refrigeration cycle, Fig. 2 is a wiring diagram of an operating circuit, Fig. 3 is a mode explanatory diagram of temperature change rate, and Fig. 4 and 5 are flowcharts showing different specific examples of control methods, respectively. In the figure, 1 is a compressor, 5 and 6 are coolers for refrigerator and freezer compartments, 9 is an inverter device, 18 is a compressor motor, and 19 is a temperature change rate determination circuit.

Claims (1)

[Claims] 1 In a refrigerator in which the compressor motor that drives the compressor of the refrigeration cycle is operated in a speed-controllable manner by an inverter device, the internal temperature or cooler temperature is detected and the rate of decrease in temperature is set to a predetermined minimum. A method for operating a refrigerator, comprising controlling the output frequency of the inverter device so as to maintain a constant value.