JPH0670546B2 - refrigerator - Google Patents

Description

TECHNICAL FIELD The present invention relates to a refrigerator that controls the temperature in a storage chamber by controlling the rotation speed of a compressor in a refrigeration cycle.

(B) Conventional technology Conventionally, in this type of refrigerator, the upper limit temperature and the lower limit temperature are set above and below the set temperature of the storage room, and the compressor of the refrigeration cycle is started at the upper limit temperature and stopped at the lower limit temperature for storage. A so-called ON-OFF control system was adopted in which the temperature inside the room was set as an average. In this method, the interval between the upper limit temperature and the lower limit temperature is not narrowed below a certain value in order to prevent frequent start and stop of the compressor, and therefore the storage chamber temperature constantly fluctuates between the upper limit temperature and the lower limit temperature. Therefore, there is a limit to the quality control ability of foods.

Recently, in order to solve this problem, for example, JP-A-60-263 has been proposed.
As disclosed in Japanese Patent Laid-Open No. 070, it is conceivable to control the temperature in the storage chamber with a variable speed compressor, and according to this, the temperature fluctuation in the storage chamber can be reduced as much as possible.

(C) Problems to be solved by the invention In the refrigeration cycle of this type of refrigerator, the high-temperature high-pressure gas refrigerant discharged from the compressor can be condensed and liquefied by the condenser.
In order to obtain an appropriately low evaporation temperature in the cooler, a decompressor is provided in the preceding stage of the cooler, and the pressure is reduced here, and then it is introduced into the cooler. This pressure reducer is composed of a capillary tube that is a thin tube having a constant flow resistance, for example, when the rotation speed of the compressor is high and the resistance value of the capillary tube is set in accordance with the state in which the refrigerant circulation amount is large, When the number of rotations decreases and the amount of refrigerant circulation decreases, the resistance value is small, so an appropriate pressure difference is not created before and after the capillary tube, and there is a problem that the evaporation temperature of the refrigerant in the cooler rises.

(D) Means for Solving the Problems The present invention provides a refrigerant circuit in which a compressor, a condenser, a decompressor, and an evaporator are sequentially connected, and the operating frequency of the compressor is based on the temperature of a freezer. In the refrigerator provided with a controller for changing the resistance value of the decompressor, the controller is a frequency changing unit for changing the operating frequency after a predetermined time after the temperature of the freezer changes by a predetermined temperature, and the change. A resistance value changing means for changing the resistance value on the basis of the changed operating frequency and the temperature of the freezer, and the resistance value changing means is provided when the changed operating frequency is equal to or lower than a preset reference frequency. When the changed operating frequency is higher than the reference frequency and the temperature of the freezer compartment is equal to or lower than the preset reference temperature, the resistance value of the pressure reducer is set to a large value, and the changed operating frequency is higher than the reference frequency. When the temperature of the freezer compartment is higher than a preset reference temperature, the resistance value of the pressure reducer is set to a small value.

(E) Action According to the present invention, it is possible to select a capillary tube having an appropriate pressure reducing resistance according to the rotation speed of the electric compressor.

(F) Example An example will be described with reference to the drawings. FIG. 2 shows a refrigerator-freezer (1) as an example. (2) is a heat insulating box, the inside of which is divided into upper and lower parts by a heat insulating partition wall (3), a freezing room (F) as a first room above and a refrigerating room (R) as a second room below ) And are compartmentalized.
(6) and (7) are heat insulating doors that separately open and close the front openings of the freezing compartment (F) and the refrigerating compartment (R).
A cooling chamber (8) is formed in the partition wall (3), and a cooler (10) included in the refrigeration cycle is housed and installed therein. A duct (11) communicating with the cooling chamber (8) and both chambers (F) and (R) is formed behind the cooler (10), and a blower (12) provided in the duct (11) is provided. )
At, the air cooled by the cooler (10), that is, cold air is sucked and forced out into the duct (11). (12M) is a motor that drives the blower (12). The cold air blown into the duct (11) is discharged from the discharge port (14) into the freezer compartment (F).
It will be blown out from the discharge port (15) to the refrigerating room (R). (17) is a refrigerating room (R) to open and close the discharge port (15)
With a gas-filled damper thermostat installed inside,
The baffle plate (18) opens and closes the discharge port (15) based on the temperature in the refrigerating compartment (R) to control the temperature of the refrigerating compartment (R) to an average of + 5 ° C between + 7 ° C and + 3 ° C. (19) is a heat insulating cover of the damper thermostat (17). Reference numeral (20) is an electric compressor installed in the machine room (21) below the refrigerator-freezer (1) and included in the refrigeration cycle. In the machine room (21), a condenser (22) similarly included in the refrigeration cycle, the condenser (22) and the electric compressor (2) described above.
A blower (23) is installed to cool (0). still,
(5) is an operation panel attached to the front surface of the door (6).

FIG. 1 shows a control electric circuit (2
4) is shown in a block diagram. (25) is a microcomputer, A / D converters (26) and (28) and a micro CP
It has the function of U (30). Reference numeral (31) is a sensor for detecting the temperature (T _F ) of the freezer compartment (F), which is an A / D converter (26).
Is input to the micro CPU (30) via. Reference numeral (33) is a setting switch for setting the temperature of the freezer compartment (F), which is input to the micro CPU (30) via the A / D converter (28).
The output of the micro CPU (30) passes through the D / A converter (36) and the inverter circuit (37) controls the rotational speed of the three-phase synchronous motor (20M) for driving the electric compressor (20). D /
The A converter (36) and the inverter circuit (37) constitute frequency changing means. The output of the micro CPU (30) is D
The motor (12M) is controlled by the driver circuit (39) via the / A converter (38). Furthermore, the output of the micro CPU (30) is input to the driver circuit (41) via the D / A converter (40), and this driver circuit (41) causes the first solenoid valve (4) to move.
2) is driven, and the output of the micro CPU (30) drives the second solenoid valve (45) by the driver circuit (44) via the D / A converter (43).

D / A converters (40), (43) and driver circuits (41),
(44) constitutes resistance value changing means.

FIG. 3 shows a refrigerant circuit diagram of the refrigeration cycle of the refrigerator-freezer (1). The high-temperature high-pressure refrigerant discharged from the electric compressor (20) radiates heat in the condenser (22), is decompressed in the pressure reducer (47), flows into the cooler (10), and evaporates there to generate heat of vaporization. It is taken from the surroundings and then sucked into the electric compressor (20).

Next, referring to the graph of FIG. 4 showing the relationship between the operating frequency of the electric compressor (20) and the temperature (T _F ) of the freezer compartment (F),
The operation of the micro CPU (30) of the control electric circuit (24) shown in the figure will be described. Setting freezing chamber that is set by the switch (33) the temperature (T _F) and (T _S) (where configurable to -22 ° C. from -12 ° C. in.) To the as the operating frequency of the solid line in the figure (F) change. That is, when the temperature (T _F ) sensed by the sensor (31) is currently higher than (T _F +4), the operating frequency of the electric compressor (20) is set to 120 Hz which is the maximum rotation speed by the inverter circuit. As a result, the temperature (T _F ) of the freezer compartment (F) rapidly decreases. As a result, (T _F ) becomes (T _S +
When 4) is reached, the current state is maintained for 3 minutes from that point, and then the operating frequency is reduced to 90 Hz. This slows down the rate of decrease of temperature (T _F ). When (T _F ) further reaches (T _S +2) from this state, the current state is maintained for 3 minutes from that point, and then the frequency is lowered to 60 Hz. This further slows down the temperature ( _TF ) decrease rate. After that, when (T _S ) is reached, the operating frequency is also reduced to 30 Hz 3 minutes after that. In this way, the temperature (T _F ) becomes asymptotic to the set temperature (T _S ) and so-called overshoot is reduced.

On the contrary, when the temperature (T _F ) rises from the operating frequency of 30 Hz to reach (T _S ), the current state is maintained for 3 minutes from that point, and then the temperature is raised to 60 Hz. Furthermore (T _S +2) When increased to, 90H after 3 minutes from the time of reaching the (T _S +2)
accelerate to z. Similarly, after reaching (T _S +4), the frequency is raised to 120 Hz after 3 minutes. In this way, the micro CPU (30) internally issues a command to change the operating frequency when the temperature (T _F ) reaches (T _S +4), (T _S +2), and (T _S ). However, from that point, the frequency is not changed for 3 minutes as described above. This is the same even if the frequency to be changed is corrected within 3 minutes, and after 3 minutes after reaching any of (T _S +4) (T _S +2) (T _S ), the corrected frequency Change to. This prevents frequent changes in the operating frequency of the electric compressor (20), and prevents deterioration of the motor (20M) and noise expansion.

Ideally, the capacity of each device is set so that the temperature (T _F ) can be maintained at the set temperature (T _S ) by operating at 30 Hz, but the load in the freezer compartment (F) is small, and the refrigerator-freezer (1)
When the ambient temperature is low, the temperature ( _TF ) drops even at 30Hz operation. In this case, stop the motor (20M) when (T _S -2) is reached. This prevents supercooling in the freezer compartment (F). After that, the temperature (T) rises (T _S
-When 2) is reached, stop for 5 minutes from that point and then start the electric compressor (20) to 30Hz. This prevents deterioration of the electric compressor (20) due to frequent start and stop. As described above, the operating frequency of the electric compressor (20) is sequentially changed according to the difference between the temperature (T _F ) and the set temperature, so the temperature (T _F ) is approximately equal to the set temperature (T _S ) (eg, -18 ° C). It is controlled stably. The blower (12) is continuously operated while the electric compressor (20) is operating. Moreover, the frequency change is not always performed in steps as shown in FIG. 4, and for example, the temperature (T _F ) changes rapidly from the state where it is (T _S ) due to the long-term opening of the door (6). If it rises to (T _S +4), in this case as well, the operating frequency is raised toward the frequency 120 Hz three minutes after the frequency change command is issued inside the micro CPU (30).

Next, FIG. 5 shows the structure of the pressure reducer (47). Pressure reducer (47)
Is the first solenoid valve (42) and the first capillary tube (5
0) series circuit and the second solenoid valve (45) and the second capillary tube (51) series circuit in parallel, the condenser (22)
It is configured to be connected between a pipe (47a) to the cooler (10) and a pipe (47b) to the cooler (10). First and second solenoid valves (42) (4
5) is controlled by the microcomputer (25) as described above, and the first capillary tube (50) is 8 kg / cm ² G and the second capillary tube (51) is 4 kg / cm, for example. The flow path resistance value is different from that of cm ² G.

Next, the control operation of the solenoid valves (42) (45) of the microcomputer (25) will be described with reference to the flowchart shown in FIG. Only in the solenoid valve control, the microcomputer (25) samples the temperature (T _F ) when the power is turned on and when a predetermined threshold value such as −20 ° C. and −16 ° C. is crossed, and the current freezing chamber (F) is sampled. It is assumed that the temperature (T _FP ) is measured and the temperature at the previous sampling (T _FP -1) is stored. Start from power-on and reset everything in step (S ₁ ), then current electric compressor (20) in step (S ₂ ).
If it is in operation, it proceeds to step (S ₄ ) to determine whether the current operating frequency (H _P ) is, for example, 65 Hz or less. From the above, the frequency is 60Hz or 30Hz
If Open Step first solenoid valve advances to (S ₉₎ (42), closes the second solenoid valve (45). Further, in step (S ₄₎ is determined whether the temperature (T _FP) is -20 ° C. or less proceeds to step (S ₅₎ If the frequency is a 120Hz or 90Hz in, if not step (S ₆₎ Temperature (T _FP ) is -16 ℃
It is judged whether or not it is above, and if it is not, the temperature (T _FP -1) at the previous sampling is compared with (T _FP ) at step (S ₇ ) and (T _FP ) is less than (T _FP -1). if the first solenoid valve in step (S ₈₎ closed (42), opens the second solenoid valve (45).
Moreover, even the temperature (T _FP) is -16 ° C. or higher in the step (S ₆₎ proceeds to step (S _8). That is, when the operating frequency of the electric compressor (20) is as low as 30 Hz or 60 Hz and the refrigerant circulation amount is small, the first capillary tube (50) is connected to the refrigerant circuit, and the flow path resistance of the pressure reducer (47) is 8 kg. / Cm ² G,
Also, when the operating frequency is as high as 90 Hz or 120 Hz and an increase in the refrigerant circulation amount is expected, the second capillary tube (51) is connected to the refrigerant circuit to reduce the flow path resistance of the pressure reducer (47).
4 kg / cm ² G As a result, the pressure difference before and after the pressure reducer (47) becomes substantially constant at each operating frequency, so that an appropriate evaporation temperature can be obtained. That is, when the operating frequency is high, the resistance value is too large and the refrigerant circulation amount is insufficient,
It is possible to prevent insufficient decompression and increase in evaporation temperature due to the resistance value being too small when the operating frequency is low.

Here, in step (S ₄ ), the operating frequency (H _P ) is 90 Hz, or
Even at 120Hz, the freezing room (F) temperature (T _FP ) is -20 ℃
In the following cases, proceed from step (S ₅ ) to (S ₉ ) to open the first solenoid valve (42) and close the second solenoid valve (45) to reduce the flow path resistance of the pressure reducer (47) to 8 kg / cm ² G This is because the refrigerant evaporation amount in the cooler (10) is small when the freezer compartment (F) is cooled to a low temperature, and therefore the refrigerant circulation amount is small even if the operating frequency of the electric compressor (20) is high. . Step (S ₇₎ Temperature (T _FP) in that the process proceeds to also step is higher than _{(T FP -1) (S 9} ) is to prevent chattering.

In addition, a step (S ₂₎ in the electric compressor (20) both of the solenoid valves proceeds to step (S ₃₎ when it is stopped (42) (4
5) Close. As a result, when the electric compressor (20) is stopped, high temperature refrigerant does not naturally flow into the cooler (10) from the condenser (22).

(G) Effect of the Invention According to the present invention, when the changed operating frequency is higher than the reference frequency and the temperature of the freezer compartment is equal to or lower than the preset reference temperature, a small amount of refrigerant is sufficient, and thus the resistance value of the pressure reducer. On the other hand, when the changed operating frequency is higher than the reference frequency and the temperature of the freezer compartment is higher than the preset reference temperature, a large amount of refrigerant is required, so the resistance value of the pressure reducer is large. This can be dealt with as a small value. Therefore, it is possible to secure the refrigerant circulation amount according to the temperature of the freezer and the refrigerant evaporation amount of the evaporator, and reliably prevent the evaporation temperature increase at the low frequency and the refrigerant circulation shortage at the high frequency to always be good. It is possible to secure a sufficient cooling capacity.

[Brief description of drawings]

Each drawing shows an embodiment of the present invention. FIG. 1 is a block diagram of a control electric circuit, FIG. 2 is a side sectional view of a refrigerator-freezer,
FIG. 3 is a refrigerant circuit diagram, FIG. 4 is a diagram showing the relationship between the operating frequency of the electric compressor and the freezer compartment temperature, FIG. 5 is a diagram showing the configuration of the pressure reducer, and FIG. 6 is a microcomputer relating to solenoid valve control. 3 is a flowchart showing the software of FIG. (F) ... Freezer, (20) ... Electric compressor, (24) ... Control electric circuit, (30) ... Micro CPU, (37) ... Inverter circuit, (42) (45) ... First and second Solenoid valve, (47) ...
Pressure reducer, (50) (51) ... First and second capillary tubes.

Claims (1)

[Claims] 1. A compressor, a condenser, a pressure reducer and an evaporator are sequentially connected to form a refrigerant circuit, and an operating frequency of the compressor and a resistance value of the pressure reducer are changed based on a temperature of a freezer. In a refrigerator provided with a control device, the control device is
Frequency changing means for changing the operating frequency after a predetermined time after the temperature of the freezer changes by a predetermined temperature, and resistance value changing means for changing the resistance value based on the changed operating frequency and the temperature of the freezer. The resistance value changing means is characterized in that when the changed operating frequency is equal to or lower than a preset reference frequency, or the changed operating frequency is higher than the reference frequency and the temperature of the freezer is equal to or lower than a preset reference temperature. In this case, the resistance value of the pressure reducer is set to a large value, and when the changed operating frequency is higher than the reference frequency and the temperature of the freezer compartment is higher than a preset reference temperature, the resistance value of the pressure reducer is set to a small value. A refrigerator characterized by that.