JP2003074948A - Controller for refrigerating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an excessive current from flowing in an electric motor upon switching the number of revolution of the electric motor for driving a compressor to a high revolution side in accordance with a load. SOLUTION: A refrigerating device 20 is provided with the compressor 21 driven by the electric motor 25, a condenser 22, a temperature automatic expansion valve 23 and an evaporator 24 while a refrigerant is circulated therethrough. The temperature automatic expansion valve 23 automatically controls the flow rate of the refrigerant supplied to the evaporator 24 in accordance with a temperature at the downstream of the evaporator 24, which is detected by a temperature sensitive tube 27. The operation control device 10 controls the number of revolution of the electric motor 25 by switching in accordance with the load of the refrigerating device 20. A microcomputer 34 allows the switching of the number of revolution of the electric motor 25 to the high revolution side only when the current I of the motor, a refrigerant pressure P1 at the downstream of the compressor 21, a refrigerant pressure P2 at the upstream side of the same, a refrigerant temperature T1 at the downstream side of the compressor 21, a refrigerant pressure P2 at the upstream side of the evaporator 24 or a temperature difference T1-T2 is under a reducing condition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a refrigerating machine which has a compressor driven by an electric motor whose speed is controlled and which cools the inside of a storage such as a refrigerator or a freezer.

[0002]

2. Description of the Related Art Conventionally, for example, JP-A-11-2811
As disclosed in Japanese Patent Laid-Open No. 72-72, refrigeration in which a refrigerant discharged from a compressor driven by an electric motor is circulated through a condenser and an evaporator, and the evaporator cools the inside of a refrigerator or a freezer. In an apparatus, it is known to switch and control the rotation speed of an electric motor according to a load. Specifically, with an outside air temperature sensor for detecting the outside air temperature, and a suction side refrigerant temperature sensor for detecting the temperature of the refrigerant gas sucked into the compressor, the difference between the two temperatures respectively detected by both sensors and A table that defines the relationship with the rotation speed of the electric motor is prepared, and the rotation speed of the electric motor is switched and controlled according to the temperature difference by referring to the table.

[0003]

However, the conventional technique of switching and controlling the number of rotations of the electric motor according to the above-mentioned load is applied to the downstream of the evaporator by an automatic temperature expansion valve provided between the condenser and the evaporator. When applied to a refrigeration system in which the flow rate of the refrigerant supplied to the evaporator is automatically adjusted in accordance with the temperature of 1, the cyclic flow of the refrigerant occurs, such as the hunting phenomenon. Due to the periodic change in the flow of the circulating refrigerant, the load of the compressor of the refrigerating apparatus having the temperature automatic expansion valve changes. Then, if the rotation speed of the electric motor that drives the compressor is switched to the high side when the load of the compressor is increasing, the electric motor will be switched due to the switching to the high speed side. As the current flowing increases, the current flowing through the electric motor also increases due to this increase in load. As a result, an extremely large current will flow in the electric motor, and in order to cope with this, it is necessary to prepare a large capacity power supply circuit for driving the electric motor and the motor.
The manufacturing cost of the refrigeration system becomes high.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and its purpose is to circulate the refrigerant discharged from a compressor driven by an electric motor through a condenser and an evaporator. , Applied to a refrigerating device that automatically adjusts the flow rate of the refrigerant supplied to the evaporator according to the temperature downstream of the evaporator by a temperature automatic expansion valve provided between the condenser and the evaporator, In a control device for a refrigeration system in which the rotation speed of an electric motor is switched and controlled according to a load, a refrigeration system in which even if the rotation speed of the electric motor is switched to a high side, the current flowing through the motor is kept as small as possible To provide a control device for the device.

In order to achieve the above-mentioned object, the structural features of the present invention are as follows: current detecting means for detecting a current flowing in an electric motor; and electric motor, provided that the detected current is in a decreasing state. And a switching control means for permitting switching of the rotation speed to the higher side. Also,
The switching control means switches the rotation speed of the electric motor to a higher side on the condition that the detected current is less than a predetermined value, in addition to the condition that the detected current is in a decreasing state. May be allowed.

In a refrigerating apparatus having a temperature automatic expansion valve in a refrigerant circulation path, a periodic change such as hunting occurs in the flow of the refrigerant circulating in the circulation path. Then, the load of the compressor fluctuates due to the periodic change of the flow of the refrigerant, and the current flowing through the electric motor repeatedly increases and decreases as shown in FIG. That is, when the load on the compressor increases, the current flowing through the electric motor increases accordingly, and when the load on the compressor decreases, the current flowing through the electric motor decreases accordingly.

As described above, when the electric current flowing through the electric motor is in a reduced state, if the rotational speed of the electric motor is allowed to be switched to a higher side, the load on the compressor tends to decrease. The rotation speed of the electric motor is switched to the higher side. That is, when the load on the compressor is increasing and the current flowing through the electric motor tends to increase, switching to the side with a higher rotation speed of the electric motor is prohibited, and the load on the compressor decreases. In a state where the current flowing through the electric motor tends to decrease, the electric motor can be switched to a higher rotation speed side. Therefore, at the time of switching the electric motor to a higher rotation speed side, it is possible to prevent an extremely large current from flowing to the electric motor even if the current flowing to the electric motor increases due to the switching. A relatively small power supply circuit can be used for the motor.

Further, another structural feature of the present invention is that, on the condition that the refrigerant pressure detecting means for detecting the refrigerant pressure downstream or upstream of the compressor and the detected refrigerant pressure are in a reduced state, A switching control means for permitting switching of the rotation speed of the electric motor to a higher side is provided. Further, the switching control means increases the rotation speed of the electric motor on the condition that the detected refrigerant pressure is less than a predetermined value, in addition to the condition that the detected refrigerant pressure is in a reduced state. You may allow it to switch to the side.

Another structural feature of the present invention is that the electric motor is provided on the condition that the temperature detecting means for detecting the temperature of the evaporator or the temperature downstream of the evaporator and the detected temperature are in a reduced state. And a switching control means for permitting switching of the rotation speed to the higher side. Further, the switching control means switches the rotation speed of the electric motor to a higher side on the condition that the detected temperature is lower than a predetermined value, in addition to the condition that the detected temperature is in a decreasing state. May be allowed.

Another structural feature of the present invention is that first temperature detecting means for detecting the temperature downstream of the evaporator, second temperature detecting means for detecting the temperature of the evaporator, and first temperature detecting means. Temperature difference calculating means for calculating a temperature difference between the temperature of the evaporator detected by the means and the temperature of the evaporator detected by the second temperature detecting means, and the calculated temperature difference is in a reduced state. Under this condition, the switching control means for permitting switching of the rotation speed of the electric motor to the higher side is provided. In addition to the condition that the calculated temperature difference is in a decreasing state, the switching control means increases the rotation speed of the electric motor on the condition that the calculated temperature difference is less than a predetermined value. It may be allowed to switch to.

The refrigerant pressure upstream of the compressor, the refrigerant pressure downstream of the compressor, the temperature of the evaporator, the temperature downstream of the evaporator, and the temperature difference between the temperature downstream of the evaporator and the temperature of the evaporator. The increase and decrease changes are the same as the increase and decrease changes of the current flowing through the electric motor, as shown in FIG. Therefore, even by these other structural features of the present invention, when the load of the compressor is increased and the current flowing through the electric motor tends to increase, the rotation speed of the electric motor is high. Switching to the side where the electric motor's rotation speed is high is permitted when the load on the compressor is reduced and the current flowing through the electric motor tends to decrease. It Therefore, even in these cases, when the electric motor is switched to a higher rotation speed side, it is possible to prevent an extremely large current from flowing to the electric motor even if the current flowing to the electric motor increases due to the switching. A relatively small electric motor and power supply circuit for the electric motor can be used.

[0012]

DETAILED DESCRIPTION OF THE INVENTION a. First Embodiment Hereinafter, a first embodiment of the present invention will be described with reference to FIG.
2 schematically shows the entire refrigerating device 20 for cooling the inside 10 of the refrigerator and the operation control device 30 thereof according to the first embodiment.

This refrigerating apparatus 20 comprises a compressor 21 for circulating a refrigerant, a condenser 22, an automatic temperature expansion valve 23 and an evaporator 24. The compressor 21 is rotationally driven by an electric motor 25 whose speed is controlled, and discharges a high temperature and high pressure refrigerant gas. As the electric motor 25, for example, a DC brushless motor can be used. The high-temperature and high-pressure refrigerant gas discharged from the compressor 21 is radiated as heat by a condenser 22 provided with a cooling fan 26, and the temperature automatic expansion valve 23
It is decompressed at, evaporated in the condenser 22 and returned to the compressor 21. The automatic temperature expansion valve 23 is connected to a temperature sensing cylinder 27 that is installed in a refrigerant flow path downstream of the evaporator 24 and senses the temperature of the downstream position, and automatically opens its opening as the sensed temperature rises. To increase the refrigerant flow rate.
An in-compartment fan 28 that cools the inside 10 by supplying cold air to the inside 10 is arranged near the evaporator 24.

The operation control device 30 has an inverter circuit 31 for controlling the rotation speed of the electric motor 25, and fan drive circuits 32, 33 for controlling the operations of the cooling fan 26 and the internal fan 28. ing. In this embodiment, the rotation speed of the electric motor 25 is changed by the inverter circuit 31 as shown in Table 1 below.
Switching control is performed in five ranks of levels L1 to L5. The rotation speed in Table 1 indicates the rotation speed of the electric motor 25 per second.

[0015]

[Table 1]

In the inverter circuit 31 and the fan drive circuits 32 and 33, the microcomputer 3
4 is connected. The microcomputer 34 executes the main program corresponding to the flowcharts of FIGS. 3 and 4 and the rank-up flag setting program corresponding to the flowchart of FIG. 5 to control the rotation speed of the electric motor 25. An internal temperature sensor 35 and a current detector 36 are connected to the microcomputer 34 via an A / D converter 37, and an internal temperature setter 38 is connected.

The inside temperature sensor 35 is used to detect the temperature T of the inside 10.
x is detected and an analog detection signal representing the temperature Tx in the same compartment is output to the A / D converter 37. The current detector 36 is incorporated in the inverter control circuit 31 to detect a current flowing through the electric motor 25, and outputs an analog detection signal representing the detected motor current I to the A / D converter 37. A / D
The converter 37 A / D-converts the analog detection signals respectively representing the inside temperature Tx and the motor current I, and outputs the analog detection signals to the microcomputer 34. The interior temperature setting device 38 is operated by the user to set the temperature Ts of the interior 10 desired by the user.

Further, the operation control device 30 includes a power supply circuit 40 for supplying electric power supplied from an external power supply line or the like to the inverter circuit 31 and the fan drive circuits 32 and 33. The power supply circuit 40 also supplies electric power to various circuits such as the microcomputer 34 and the A / D converter 37 as needed.

Before explaining the operation of the embodiment configured as described above, each relationship between the cooling capacity of the refrigerating apparatus 20 and the current flowing through the electric motor 25 with respect to the internal temperature Tx will be described. FIG. 2 shows a characteristic graph of the above two relationships, and the two-dot chain line in FIG. 2 indicates the temperature Tx in the refrigerator.
The characteristic line of the heat load with respect to is shown. The heat load represents the total value of the amount of heat entering the inside of the refrigerator 10 from the outside and the amount of internal heat generation of the inside of the refrigerator 10. From this characteristic line, it can be understood that the heat load increases as the inside temperature Tx decreases.

The solid line, broken line and alternate long and short dash line in the upper portion of FIG. 2 indicate that the electric motor 25 is operated at high speed, medium speed and low speed (for example, levels L5, L3 in Table 1 above) with respect to the internal temperature Tx. Each of the changing characteristics of the cooling capacity of the refrigerating apparatus 10 when rotated at (corresponding to L1) is shown. According to this, it can be understood that the cooling capacity of the refrigeration system 10 becomes higher as the electric motor 25 is rotated at a higher speed, and becomes higher as the inside temperature Tx becomes higher. Further, the cooling power of the interior 10 is defined by the difference between the cooling capacity of the refrigeration system 10 and the heat load. It can be understood that the cooling power of the inside 10 also becomes higher as the electric motor 25 is rotated at a higher speed, and becomes higher as the inside temperature Tx becomes higher, as indicated by the thick arrow in the figure.

The solid line, broken line and alternate long and short dash line at the bottom of FIG. 2 indicate that the electric motor 25 is operated at high speed, medium speed and low speed (for example, levels L5, L3 in Table 1 above) with respect to the internal temperature Tx. The characteristics of change in the magnitude of each current flowing through the electric motor 25 when rotated at (corresponding to L1) are shown. According to this, it can be understood that the current flowing through the electric motor 25 becomes larger as the electric motor 25 is rotated at a higher speed, and becomes larger as the inside temperature Tx becomes higher. The dotted line in FIG. 2 indicates the maximum allowable current Imax (rated current) of the electric motor 25 and the power supply circuit 40. When the rotation speed of the electric motor 25 is increased,
It can be understood that the electric current more than the maximum permissible current Imax tends to flow through the electric motor 25 as the inside temperature Tx increases. Therefore, the maximum allowable current (rated current) of the power supply circuit 40 may be determined so as to match the maximum allowable current Imax of the electric motor 25. Further, the dotted area in FIG. 2 indicates an area (prohibition area) where the refrigerating apparatus 10 cannot exert the cooling power.

The operation of the refrigerator provided with the refrigerating apparatus 20 having such characteristics will be described. After the user sets the set temperature Ts to a desired value using the internal temperature setting device 38,
When you start the operation with a switch not shown,
The microcomputer 34 starts executing the main program in step 100 of FIG. It should be noted that when the execution of this program is started, the microcomputer 34
Outputs an operation command to the fan drive circuits 32 and 33 to operate the cooling fan 26 and the internal fan 28.

After starting the execution of this program, step 1
At 02, the rank data RNK indicating the rank of the rotation speed of the electric motor 25 is set to the level L3, and the same rank data RNK is output to the inverter circuit 31. The inverter circuit 31 rotates the electric motor 25 at a rotation speed corresponding to the level L3 represented by the supplied rank data RNK. The rotation speed of the electric motor 25 with respect to each level is as shown in Table 1 above, and at a speed slow enough to suppress the current flowing through the electric motor 25 to the maximum allowable current Imax or less in relation to the internal temperature Tx. is there.

The rotation of the electric motor 25 is transmitted to the compressor 21, and the compressor 21 starts to discharge the high temperature and high pressure refrigerant.
The refrigerant discharged from the compressor 21 circulates through the condenser 22, the automatic temperature expansion valve 23, and the evaporator 24.
Then, by the circulation of the refrigerant, the refrigerating device 20 starts cooling the inside 10 in cooperation with the internal fan 28. on the other hand,
In the circulation of the refrigerant, the presence of the temperature automatic expansion valve 23 causes a periodic change such as hunting in the circulating refrigerant flow. Then, the load of the compressor 21 fluctuates due to the periodic change of the flow of the refrigerant, and the current flowing through the electric motor 25 repeatedly increases and decreases as shown in FIG.

After the processing of step 102, step 1
At 04, the inside temperature Tx detected by the inside temperature sensor 35 is input via the A / D converter 37, and the input inside temperature Tx is a predetermined relatively high predetermined temperature T1 ( For example, it is determined whether the temperature is lower than 10 ° C.

Immediately after the start of the operation of the refrigerating apparatus 20, if the internal temperature Tx is higher than the predetermined temperature T1 depending on the outside air temperature, it is determined to be "NO" in step 104 and the steps 102 and 104 are executed. The cyclic processing is repeated. By this circulation processing, when the inside 10 is cooled and the inside temperature Tx becomes lower than the predetermined temperature T1, step 104
Then, the program is judged to be "YES" and the program is executed in step 106.
Proceed to.

In step 106, it is determined whether or not the rank up flag RUF is "1". The rank-up flag RUF represents a state where "1" allows the rise of the rank data RNK, that is, an increase control of the rotation speed of the electric motor 25, and a "0" represents a state where the rise control is prohibited. This rank up flag RUF is
By executing the rank-up setting program of FIG. 5, "1" or "0" is set according to the change of the motor current I. This rank-up setting program is repeatedly interrupted and executed at predetermined short intervals during execution of the main program shown in FIGS.

This rank-up flag setting program is started in step 300 of FIG.
2 is detected by the current detector 36 and A /
A / D converted motor current I is input to the D converter 37, and the input motor current (current motor current) I is a subtraction value Iold obtained by subtracting a minute value ΔI from the previous motor current Iold1.
Determine if it is less than 1-ΔI. Also, step 3
In 04, the previous motor current Iold1 is the subtracted value Iold2-ΔI obtained by subtracting the small value ΔI from the motor current Iold2 two times before.
It is determined whether it is less than. In this case, the previous motor current old1 and the previous-previous motor current Iold2 are calculated in step 30
By the processing of steps 312 and 314 after the processing of 2 to 310, it is updated each time the rank-up flag setting program is executed. And the previous motor current ol
d1 represents the motor current I at the time of executing the previous rank-up flag setting program. Before-previous motor current Iold
2 represents the motor current I when the rank-up flag setting program is executed two times before.

The current motor current I is less than the subtraction value Iold1−ΔI, and the previous motor current Iold1 is the subtraction value Iold2−.
If it is less than ΔI, it is determined to be “YES” in both steps 302 and 304, and the program is executed in step 306.
Proceed to. It should be noted that the determination of “YES” in both steps 302 and 304 means that the motor current I is in a reduced state. In step 306, it is determined whether or not the current motor current I is less than the predetermined current value Io. The predetermined current value Io is set in advance to a value near the center of the change range of the motor current I. If the motor current I is less than the predetermined current value Io this time, step 3
It is determined to be “YES” in 06, and the rank-up flag RUF is set to “1” in step 308. And
After the processing of steps 312 and 314, step 316
Then, the execution of this rank-up flag setting program ends.

On the other hand, this time the motor current I is the subtracted value Iold1-
ΔI or more and the previous motor current Iold1 is the subtracted value Iold2
If it is −ΔI or more, or if the current motor current I is not less than the predetermined current value Io this time, “NO” is determined in any of the determination processes of steps 302 to 306, and the process proceeds to step 310. In step 310, the rank up flag RUF is set to "0". Then, the steps 312, 31
After the processing of 4, the execution of this rank-up flag setting program is ended in step 316. Therefore, by executing the rank-up flag setting program, the rank-up flag RUF is set to "1" only when the motor current I is in a decreasing state and is less than the predetermined current value Io, and other than that. Sometimes it is set to "0".

Returning again to the description of the main program in FIG. 3, as long as the rank-up flag RUF is "0", the determination of "NO" is continued in step 106 and the progress of the program is stopped. On the other hand, the rank-up flag RUF
If is “1”, it is determined to be “YES” in step 106, and the process proceeds to step 108. In step 108, the rank data RNK is set to the level L4 (or level L5) and the same rank data RNK is output to the inverter circuit 31. The inverter circuit 31 rotates the electric motor 25 at a rotation speed corresponding to the set level L4 (or level L5). The rotation speed of the electric motor 25 corresponding to the level L4 (or the level L5) is higher than the rotation speed of the electric motor 25 corresponding to the level L3 shown in Table 1 above.
The speed is such that the current flowing through the electric motor 25 and the power supply circuit 40 can be suppressed to the maximum allowable current Imax or less in relation to the internal temperature Tx. As a result, the current flowing through the electric motor 25 and the power supply circuit 40 is suppressed to the maximum allowable current Imax or less, and the cooling capacity of the refrigeration system 20 is enhanced.

After the processing of step 108, step 1
At 10, the inside temperature T input from the inside temperature sensor 35
It is determined whether x is lower than a predetermined temperature T2 (for example, 5 ° C.) lower than the predetermined temperature T1. Internal temperature Tx
Is higher than the predetermined temperature T2, in step 110, “N
It is determined to be “O”, and the circulation process including steps 108 and 110 is repeatedly executed. By this circulation processing, the inside 10 is continuously cooled.

During the circulation process consisting of steps 108 and 110, if the internal temperature Tx becomes lower than the predetermined temperature T2, it is determined to be "YES" in step 110 and the program proceeds to step 112. In step 112, “1” is subtracted from the rank data RNK, and the subtracted rank data RNK is output to the inverter circuit 31. The inverter circuit 31 rotates the electric motor 25 at a rotation speed corresponding to the subtracted rank data RNK. Therefore, the rotation speed of the electric motor 25 is reduced, and the compressor 21 is driven at this reduced rotation speed to cool the interior 10. That is, the cooling capacity of the refrigerating device 20 is switched to the lower side by one rank.

After the processing of step 112, the circulation processing of steps 114 and 116 of FIG. 4 is repeatedly executed. In step 114, it is determined whether the internal temperature Tx is equal to or higher than a predetermined temperature (upper limit temperature) T2 ′ (for example, 5.5 ° C.) higher than the predetermined temperature T2. Step 1
In 16, it is determined whether the internal temperature Tx is equal to or lower than the lower limit temperature Ts + ΔT11 obtained by adding the predetermined increment value ΔT11 to the set temperature Ts. The predetermined increment value ΔT11 is set to 2.5 ° C., and the set temperature Ts is 1 ° C., for example.
If the lower limit temperature Ts + ΔT11 is set to 3.
It is 5 ° C. Therefore, the internal temperature Tx is lower than the lower limit temperature Ts.
If it is between + ΔT11 and the upper limit temperature T2 ', step 1
Both of the determinations at 14 and 116 continue to be "NO", and the circulation processing including steps 114 and 116 is repeatedly executed. In this state, the refrigerating apparatus 20 continues to be operated in a state in which it is switched to the lower side by one rank by the processing of step 112.

If the internal temperature Tx becomes lower than or equal to the lower limit temperature Ts + ΔT11 by this cooling, in step 116, "YE
S ”is determined and the program proceeds to step 118 and the subsequent steps. In step 118, “1” is subtracted from the rank data RNK, and the subtracted rank data RNK is output to the inverter circuit 31. Therefore, the rotation speed of the electric motor 25 is reduced, and the compressor 21 is driven at the reduced rotation speed to cool the interior 10. That is, the cooling capacity of the refrigerating device 20 is switched to the lower side by one rank.

On the other hand, during the circulation processing in steps 114 and 116, when the internal temperature Tx becomes equal to or higher than the upper limit temperature T2 ', it is determined to be "YES" in step 114 and the process proceeds to step 120. In step 120, as in the case of the determination processing in step 106 described above, it is determined whether or not the rank-up flag RUF is "1". Also in this case, the rank-up flag RUF is "1".
If so, it is determined to be “YES” in step 120,
Go to step 122. However, the rank-up flag R
If the UF is "0", the determination is continued to be "NO" in step 120, and waits until the flag RUF becomes "1".

In step 122, "1" is added to the rank data RNK, and the rank data R is added.
NK is output to the inverter circuit 31. Therefore, the rotation speed of the electric motor 25 is increased, and the compressor 21 is driven at this increased rotation speed to cool the inside 10 of the refrigerator. That is, the cooling capacity of the refrigerating apparatus 20 is switched to the higher side by one rank. Then, after the processing of step 122, the process returns to the circulation processing of steps 108 and 110 of FIG.

After the processing of step 118, step 1
The circulation process composed of 24 and 126 is repeatedly executed. In step 124, it is determined whether the internal temperature Tx is equal to or higher than the upper limit temperature Ts + ΔT12 obtained by adding the predetermined increment value ΔT12 to the set temperature Ts. The predetermined increment value ΔT12 is larger than the increment value ΔT11 and is set to 3.0 ° C., for example, and if the set temperature Ts is set to 1 ° C., the upper limit temperature Ts + ΔT12 is 4.0 ° C. is there. In step 126, it is determined whether the internal temperature Tx is lower than or equal to the lower limit temperature Ts + ΔT21 obtained by adding a predetermined increment value ΔT21 to the set temperature Ts. The predetermined increment value ΔT21 is smaller than the increment value T11 and is set to, for example, 1.0 ° C. If the set temperature Ts is set to 1 ° C., the lower limit temperature Ts + ΔT21 is 2.0 ° C. is there. Therefore, the internal temperature Tx is lower than the lower limit temperature Ts + ΔT21 and the upper limit temperature Ts + Δ.
If it is between T12, it is continuously determined as "NO" in both steps 124 and 126, and the circulation process including steps 124 and 126 is repeatedly executed. In this state, the refrigerating apparatus 20 continues to be operated while being switched to the lower side by one rank by the process of step 118.

If the internal temperature Tx becomes lower than or equal to the lower limit temperature Ts + ΔT21 by this cooling, in step 126, "YE
S "is determined and the program proceeds to step 128 and thereafter. In step 128, “1” is subtracted from the rank data RNK, and the subtracted rank data RNK is output to the inverter circuit 31. Therefore, the rotation speed of the electric motor 25 is reduced, and the compressor 21 is driven at the reduced rotation speed to cool the interior 10. That is, the cooling capacity of the refrigerating device 20 is switched to the lower side by one rank.

On the other hand, during the circulation process of steps 124 and 126, if the internal temperature Tx becomes equal to or higher than the upper limit temperature Ts + T12, it is determined to be "YES" in step 124 and the process proceeds to step 130. In step 130, it is determined whether or not the rank-up flag RUF is "1", as in the case of the determination processing in step 106 described above. Also in this case, if the rank-up flag RUF is "1", it is determined to be "YES" in step 130 and the process proceeds to step 132. However, if the rank-up flag RUF is “0”, “N
It continues to determine “O” and waits until the flag RUF becomes “1”.

At step 132, "1" is added to the rank data RNK, and the rank data R is added.
NK is output to the inverter circuit 31. Therefore, the rotation speed of the electric motor 25 is increased, and the compressor 21 is driven at this increased rotation speed to cool the inside 10 of the refrigerator. That is, the cooling capacity of the refrigerating apparatus 20 is switched to the higher side by one rank. Then, after the processing of step 132, the process returns to the circulation processing of steps 114 and 116 described above.

After the processing of step 128, step 1
The circulation process composed of 34 and 136 is repeatedly executed. In step 134, it is determined whether the internal temperature Tx is equal to or higher than the upper limit temperature Ts + ΔT22 obtained by adding the predetermined increment value ΔT22 to the set temperature Ts. The predetermined increment value ΔT22 is larger than the increment value ΔT21 and is set to, for example, 1.5 ° C. If the set temperature Ts is set to, for example, 1 ° C., the upper limit temperature Ts + ΔT22 is 2.5 ° C. is there. In step 136, it is determined whether the internal temperature Tx is equal to or lower than the lower limit temperature Ts + ΔT31 obtained by adding a predetermined increment value ΔT31 to the set temperature Ts. The predetermined increment value ΔT31 is smaller than the increment value ΔT21 and is set to, for example, −1.0 ° C. If the set temperature Ts is set to, for example, 1 ° C., the lower limit temperature Ts + ΔT31 is 0.0 ° C. Is. Therefore, the internal temperature Tx is lower than the lower limit temperature Ts + ΔT31 and the upper limit temperature T.
If it is between s + ΔT22, it is continuously determined as “NO” in steps 134 and 136, and steps 134 and 1
The cyclic processing from 36 continues to be repeatedly executed. In this state, the refrigerating apparatus 20 continues to be operated in a state where it is switched to the lower side by one rank by the process of step 128.

If the internal temperature Tx becomes lower than or equal to the lower limit temperature Ts + ΔT31 by this cooling, in step 136, "YE
S "is determined and the process proceeds to step 142 and thereafter. Step 1
At 42, the operation of the electric motor 25 is stopped.
By stopping the operation of the electric motor 25, the refrigerating device 20 stops the cooling operation.

On the other hand, during the circulation processing in steps 134 and 136, if the internal temperature Tx exceeds the upper limit temperature Ts + T22, it is determined to be "YES" in step 134 and the process proceeds to step 138. In step 138, it is determined whether or not the rank-up flag RUF is “1”, as in the case of the determination processing in step 106 described above. Also in this case, if the rank-up flag RUF is "1", it is determined to be "YES" in step 138 and the process proceeds to step 140. However, if the rank-up flag RUF is “0”, “N
It continues to determine “O” and waits until the flag RUF becomes “1”.

In step 140, "1" is added to the rank data RNK and the rank data R is added.
NK is output to the inverter circuit 31. Therefore, the rotation speed of the electric motor 25 is increased, and the compressor 21 is driven at this increased rotation speed to cool the inside 10 of the refrigerator. That is, the cooling capacity of the refrigerating apparatus 20 is switched to the higher side by one rank. Then, after the processing of step 140, the processing returns to the circulation processing of steps 124 and 126 described above.

After the processing of step 142, step 1
At 44, the internal temperature Tx is increased to the set temperature Ts by a predetermined increment value Δ.
It is determined whether the temperature is equal to or higher than the upper limit temperature Ts + ΔT32 to which T32 is added. The predetermined increment value ΔT32 is the increment value ΔT3.
If it is set to be higher than 1 and is set to 0.5 ° C., for example, and the set temperature Ts is set to 1 ° C., the upper limit temperature Ts + ΔT 32 is 1.5 ° C. Therefore, if the internal temperature Tx is less than the upper limit temperature Ts + ΔT32, step 1
Continuing to be judged as “NO” at 44, step 142,
The circulation processing from 144 continues to be repeatedly executed. In this state, the operation of the electric motor 25 continues to be stopped, and the operation of the refrigeration system 20 also continues to be stopped.

On the other hand, during the circulation processing in steps 142 and 144, if the internal temperature Tx exceeds the upper limit temperature Ts + T32, it is determined to be "YES" in step 144 and the routine proceeds to step 146. In step 146, the operation of the electric motor 25 is restarted. And step 1
Returning to the circulation processing of 34 and 136, the refrigerating apparatus 20 is
Start cooling 0. In this case, since the rank data RNK is kept set as in step 128 described above, the rotation speed of the electric motor 25 is kept the same as that in the circulation processing in steps 134 and 136 described above.

As described above, in the first embodiment, the rotation speed of the electric motor 25 is sequentially switched between the increasing direction and the decreasing direction according to the load of the refrigeration system 20. When the rotation speed of the electric motor 25 is switched to the increasing direction, steps 106, 120, 130 and 138 of the main program shown in FIGS.
5 and the execution of the rank-up flag setting program of FIG. 5, the motor current I flowing through the electric motor is reduced and is increased to the increasing side only under the condition that it is less than the predetermined current value Io. It is allowed to change the rotation speed of. In other cases, switching of the rotation speed to the increasing side is prohibited until the above condition is satisfied.

As can be understood from the above description of the operation, according to the above embodiment, when the load of the compressor 21 is increased and the current flowing through the electric motor 25 tends to increase, When the switching of the electric motor 25 to the higher rotation speed side is prohibited, and the load of the compressor 21 is reduced and the current flowing through the electric motor 25 tends to decrease, the electric motor 25 Switching to the higher speed side is allowed. Therefore, the electric motor 2
Even when the current flowing through the electric motor 25 increases due to the switching at the time of switching to a higher rotation speed side of 5, it is possible to prevent an excessively large current from flowing through the electric motor 25, and the electric motor 25 and the power supply. A relatively small circuit can be used as the circuit 40.

B. Second Embodiment Next, a second embodiment in which the present invention is applied to a freezer will be described. Also in this second embodiment, the refrigerating apparatus 20
The operation control device 30 is configured similarly to the first embodiment. Further, in the second embodiment, the microcomputer 34 executes the main program corresponding to the flowcharts of FIGS. 7 and 8 and the rank-up flag setting program of FIG. The graph of FIG. 2 relating to the characteristics of the refrigerating device 20 and the electric motor 25 of FIG. 2 also has different temperatures,
The characteristics also apply to the freezer according to the second embodiment.

Next, the operation of the second embodiment will be described. Also in this case, upon the start of operation, the microcomputer 34 starts the program from step 200 of FIG. 7 and operates the cooling fan 26 and the internal fan 28. The processing of steps 202 to 210 of FIG. 7 is substantially the same as the processing of steps 102 to 110 of FIG. 3 of the first embodiment. The difference is that step 202,
It is the rank of the rotation speed of the electric motor 25 set in 208 and the temperature compared with the internal temperature Tx in step 210. That is, in the case of this freezer, the rank data RNK is set to the levels L2 and L3 in steps 202 and 208, respectively. Also, step 2
A predetermined temperature T4 that is compared with the internal temperature Tx in 10
Is -5 ° C.

After the processing of steps 202 to 210, the processing of steps 212 to 216 is executed. The processing of these steps 212 to 216 is the same as the processing of steps 206 to 210. However, in step 214, the rank data RNK is set to the level L4 or L4, respectively.
5 is set, and in step 216, the inside temperature Tx is set.
Is compared with a predetermined temperature T4 (eg, -18 ° C). Then, if the internal temperature Tx falls below the predetermined temperature T4,
It is determined to be "YES" at step 216, and the routine proceeds to the normal operation control routine after step 218 of FIG.

Therefore, in the second embodiment, from the state where the internal temperature Tx is extremely high immediately after the operation of the refrigerating apparatus 20 is started until the internal temperature Tx reaches 10 ° C.,
The rank of the rotation speed of the electric motor 25 is set to the level L2. Then, the rank of the rotation speed of the electric motor 25 when the internal temperature Tx is from 10 ° C. to −5 ° C. is the level L.
3, and the rank of the rotation speed of the electric motor 25 when the internal temperature Tx is from -5 ° C to -18 ° C is level L.
4 or level L5. At these levels L2 to L5, the current flowing through the electric motor 25 and the power supply circuit 40 can be suppressed to the maximum allowable current Imax or less, as in the case of the first embodiment.

After the processing of steps 212 to 216, the microcomputer 34 executes steps 218 to 25 of FIG.
The steady operation routine consisting of 0 is executed. The processing of these steps 218 to 250 is similar to that of the first embodiment shown in FIG.
The processing is substantially the same as the processing of steps 114 to 146 of. The difference is that steps 218, 220, 228, 2
It is a temperature compared with the in-compartment temperature Tx at 30, 238, 240, and 248. That is, a predetermined temperature (upper limit temperature) T4 ′ that is compared with the internal temperature Tx in step 218.
Is a low temperature such as -17.5 ° C. Also, steps 220, 228, 230, 238, 24
Predetermined increment value Δ added to the set temperature Ts at 0, 248
T41, ΔT42, ΔT51, ΔT52, ΔT61, and ΔT62 are, for example, 0 ° C., 1 ° C., −0.5 ° C., 0.5 ° C., −1, respectively.
It is set to 0 ℃ and 0 ℃. Then, if the set temperature Ts is set to, for example, −20 ° C., steps 220, 228, 23
The upper or lower limit temperature Ts + ΔT41, Ts + ΔT42, which is compared with the internal temperature Tx at 0, 238, 240, 248,
Ts + ΔT51, Ts + ΔT52, Ts + ΔT61, Ts + Δ
T62 is, for example, −20 ° C., −19 ° C., −20.
It becomes 5 degreeC, -19.5 degreeC, -21 degreeC, and -20 degreeC.

When it is judged "YES" in step 218, that is, the internal temperature Tx is equal to or higher than the upper limit temperature T4 ', after the processing of steps 220 and 224, the circulation consisting of steps 214 and 226 of FIG. Returned to processing.

As a result, even in the freezer according to the second embodiment, in the steady operation state after the start of the refrigerating apparatus 20, that is, in the state where the internal temperature Tx is lower than the predetermined temperature T4, the electric power is increased as the internal temperature Tx rises. The rotation speed of the motor 25 is controlled to be high, that is, the cooling capacity of the refrigeration system 20 is controlled to be high. Therefore, in the steady operation state of the freezer, when the item to be cooled is newly put in the inside 10 or when the cooled item is taken out from the inside 10, the inside temperature Tx is slightly different from the set temperature Ts. Even if the temperature rises, the temperature rise in the refrigerator 10 is corrected promptly and accurately, and the refrigerator temperature Tx during the steady operation of the refrigerating apparatus 20 is kept substantially at the set temperature Ts.

As described above, also in the second embodiment, the rotation speed of the electric motor 25 is sequentially switched between the increasing direction and the decreasing direction according to the magnitude of the load of the refrigeration system 20. When the rotation speed of the electric motor 25 is switched to the increasing direction, steps 206, 212, 222, and 23 of the main program of FIGS.
4, 242 and the execution of the rank-up flag setting program of FIG. 5, the motor current I flowing through the electric motor 25 is in a reduced state and is less than the predetermined current value Io only under the condition. Switching of the rotational speed to the increasing side is allowed. Otherwise,
Until the above condition is satisfied, switching of the rotation speed to the increasing side is prohibited. As a result, also in the second embodiment, the same effect as that of the first embodiment can be expected.

C. Modifications Next, modifications of the first and second embodiments will be described. First, in the rank-up flag setting program of FIG. 5, it is determined by the determination process of steps 302 and 304 that the motor current I is in a reduced state when the motor current I continuously decreases twice or more. If the motor current I decreases even once, it may be determined that the motor current I is in a decreasing state. In this case, the determination process of step 304 may be omitted. Further, it may be determined that the motor current I is in a decreasing state when the motor current I decreases three times, four times or more ... In this case, the process of sequentially determining the magnitude of the old motor current I may be performed in series in steps 302 and 304. Furthermore, the condition that the motor current I is less than the predetermined current value Io is removed, that is, step 306.
The present invention can be carried out by omitting the processing of 1) and setting the rank-up flag RUF to "1" only under the condition that the motor current I is in a reduced state.

In the first and second embodiments described above, the setting of the rank-up flag RUF is controlled based on the motor current I flowing through the electric motor 25. The first and second embodiments can be modified to use variables.

As a first modification of this type, the compressor 21
Is to use the refrigerant pressure downstream. In this case,
As shown in, the pressure sensor 41 is arranged in the refrigerant flow path downstream of the compressor 21. The pressure sensor 41 detects the pressure P1 of the high-pressure refrigerant downstream of the compressor 21 and outputs an analog signal indicating the detected pressure P1. This analog signal is also A
The signal is converted into a digital signal by the / D converter 37 and supplied to the microcomputer 34. Further, the microcomputer 34 executes the rank-up flag setting program shown in FIG. 9 instead of the rank-up flag setting program shown in FIG. For other parts, see above
This is the same as in the case of the first and second embodiments.

Each process of steps 400 to 416 of FIG. 9 constituting the rank-up flag setting program is performed by the steps 300 to 300 of the rank-up flag setting program of FIG.
This is substantially the same as each process of 316. However, in steps 402 to 406, 412, and 414 of FIG. 9, instead of the current motor current I, the previous motor current Iold1, and the two-previous-time motor current Iold2, the current pressure P1, the previous pressure P1old1, and the two-previous time detected by the pressure sensor 41 are detected. The motor current P1old2 is used. In step 406, the current pressure P1 is the predetermined pressure value P10.
Compared to. This predetermined pressure value P10 is the pressure sensor 41
It is set to a value near the center of the change range of the pressure P1 detected by.

A second modification of this type is that the pressure sensor 41 of the first modification is replaced with a pressure sensor 42 for detecting the pressure P2 of the low-pressure refrigerant downstream of the compressor 21. Then, in this case, the ramp-up flag setting program in which the pressure P1 in FIG. 9 is replaced with the pressure P2 is executed. The other points are the same as the first modification.

As a third modification of this type, the temperature of the refrigerant downstream of the evaporator 24 is used. In this case, as shown in FIG. 1, the temperature sensor 43 is attached to the temperature-sensitive cylinder 27, or the temperature sensor 43 is attached to the refrigerant passage downstream of the evaporator 24. The temperature sensor 43 detects the refrigerant temperature T1 downstream of the evaporator 24, and outputs an analog signal representing the detected temperature T1. This analog signal is also A / D
The signal is converted into a digital signal by the converter 37 and supplied to the microcomputer 34. Further, the microcomputer 34 executes the rank-up flag setting program shown in FIG. 10 instead of the rank-up flag setting program shown in FIG. For other parts, first
And it is similar to the case of the second embodiment.

Each process of steps 500 to 516 of FIG. 10 constituting the rank-up flag setting program is as shown in FIG.
Step 300 of the rank up flag setting program
To 316 are substantially the same. However, steps 502 to 506, 512 and 514 in FIG.
In place of the current motor current I, the previous motor current Iold1 and the two-previous motor current Iold2, the temperature sensor 43
The current temperature T1, the previous temperature T1old1 and the two-previous temperature T1old2 detected by are used. Further, in step 506, the current temperature T1 is compared with the predetermined temperature value T10. The predetermined temperature value T10 is set to a value near the center of the change range of the temperature T1 detected by the temperature sensor 43.

The fourth modification is that the temperature sensor 43 of the third modification is replaced with a temperature sensor 44 for detecting the temperature T2 of the evaporator 24. Then, in this case, the ramp-up flag setting program in which the temperature T1 in FIG. 10 is replaced with the temperature T2 is executed. Other points are the same as in the third modification.

In the first to fourth modified examples as described above, the refrigerant pressure P1 downstream of the compressor 21, the refrigerant pressure P2 upstream of the compressor 21, the temperature downstream of the evaporator 24 (even the temperature of the temperature sensitive tube 27) The same) T1 and the change in the increase and decrease of the temperature T2 of the evaporator 24, as shown in FIG.
This is the same as the change in the increase and decrease of the current I flowing through 5. Therefore, according to these modified examples, the compressor 2
When the load of No. 1 increases and the current flowing through the electric motor 25 tends to increase, the electric motor 2
Switching to the higher rotation speed side of 5 is prohibited, and the compressor 21
When the load of the electric motor 25 is decreasing and the current flowing through the electric motor 25 tends to decrease, the electric motor 2
Switching to a higher rotation speed of 5 is permitted. Therefore, when the electric motor 25 is switched to the higher rotation speed side,
Even if the current flowing through the electric motor 25 increases due to the switching, it is possible to avoid an extremely large current flowing through the electric motor 25, and it is possible to use a relatively small electric motor 25 and power supply circuit 40. it can.

Further, as shown in FIG. 6, the change in the temperature T1 downstream of the evaporator 24 (the same applies to the temperature of the temperature sensing tube 27) is:
It is considerably larger than the change in the temperature T2 of the evaporator 24. The increase and decrease of the temperature difference T1-T2 between the two temperatures T1 and T2 also changes as shown in FIG.
This is the same as the change of the current I flowing through. By using this, the rank-up flag setting program of FIG. 5 of the above-described embodiment can be modified into the rank-up flag setting program of FIG.

In the rank-up flag setting program shown in FIG. 11, the temperature of the refrigerant downstream of the evaporator 24 detected by the temperature sensor 43 in the step 602 after the execution of the step 600 (the same applies to the temperature of the temperature sensitive cylinder 27). ) T
1, the evaporator 24 detected by the temperature sensor 44
Is subtracted, and the subtraction result T1-T2 is set as the comparison temperature T (= T1-T2). This step 6
After the processing of 02, the processing of steps 604 to 618 is executed. Each processing of these steps 604-618 is shown in FIG.
Step 302 of the rank-up flag setting program
To 316 are substantially the same. However, steps 604 to 608, 614, 616 in FIG.
In place of the current motor current I, the previous motor current Iold1 and the two-previous motor current Iold2, the comparison temperature T
The current temperature T, the previous temperature Told1, and the temperature two times before the previous temperature Told2 are used. Further, in step 608, the current temperature T is compared with the predetermined temperature value T0. The predetermined temperature T0 value is set to a value near the center of the change range of the comparison temperature T.

As a result, also in this modification, the first
Similarly to the first to fourth modified examples, when the load of the compressor 21 is in an increasing state and the current flowing in the electric motor 25 tends to increase, the electric motor 25 is rotated toward the higher rotation speed side. When the switching is prohibited and the load of the compressor 21 is in the reduced state and the current flowing through the electric motor 25 tends to decrease, the switching of the electric motor 25 to the higher rotation speed side is allowed. It Therefore, the electric motor 25
Of the electric motor 2 even when the current flowing through the electric motor 25 increases due to the switching when the speed is switched to a higher rotation speed side.
It is possible to prevent an excessively large current from flowing through 5, and it is possible to use relatively small electric motors 25 and power supply circuits 40.

Also in these modified examples, FIGS.
In the rank-up flag setting program of No. 2, steps 402, 404, 502, 504, 604, 606.
By the determination process of,
When pressures T and T decrease twice or more in succession, pressures P1 and P2
And, the temperatures T1, T2 and T are determined to be in a decreasing state, respectively. However, if the pressures P1, P2 and the temperatures T1, T2, T decrease even once, the pressures P1, P2
2 and the temperatures T1, T2 and T may be determined to be in a decreasing state. In this case, steps 404 and 50
The determination processes of 4,606 may be omitted.

The pressures P1 and P2 and the temperatures T1 and T
It may be determined that the motor current I is in a decreasing state when the values of 2, T decrease three times, four times or more continuously. In this case, the old pressures P1 and P2 and the temperature T
The process of determining the magnitude of 1, T2, and T is step 40.
2, 404, 502, 504, 604, 606 may be performed in series. Further, the conditions that the pressures P1, P2 and the temperatures T1, T2, T are less than the predetermined pressure values P10, P20 and the predetermined temperature values T10, T20, T0 are removed, that is, steps 406, 506, 608.
The present invention can also be implemented by omitting the respective processes and setting the rank-up flag RUF to "1" when the pressures P1 and P2 and the temperatures T1, T2 and T are in a reduced state.

Furthermore, in the above-described first embodiment, second embodiment and various modifications, the example in which the present invention is applied to a refrigerator and a freezer has been described, but the present invention can also be applied to a refrigerator and a freezer which also serve as a freezer. Is.

[Brief description of drawings]

FIG. 1 is a schematic block diagram schematically showing an entire refrigerating device for cooling the inside of a refrigerator, a freezer or the like and an operation control device thereof according to the first and second embodiments of the present invention and their modifications. It is a figure.

FIG. 2 is a characteristic graph showing the respective relationships of the cooling capacity of the refrigeration system and the current flowing through the electric motor with respect to the temperature inside the refrigerator.

FIG. 3 is a flowchart showing a first half portion of a main program executed by the microcomputer of FIG. 1 according to the first embodiment of the present invention.

FIG. 4 is a flowchart showing a second half of the main program executed by the microcomputer of FIG. 1 according to the first embodiment of the present invention.

FIG. 5 is a flowchart showing a rank-up flag setting program executed by the microcomputer of FIG. 1 according to the first and second embodiments of the present invention.

FIG. 6 is a diagram showing an electric current flowing through the electric motor, a refrigerant pressure downstream or upstream of the compressor, a temperature downstream of the evaporator (temperature-sensitive tubular portion),
It is a graph which shows the relationship between the temperature of an evaporator, and the opening of a temperature automatic expansion valve.

FIG. 7 is a flowchart showing a first half portion of a main program executed by the microcomputer of FIG. 1 according to the second embodiment of the present invention.

8 is a flowchart showing a second half of the main program executed by the microcomputer of FIG. 1 according to the second embodiment of the present invention.

9 is a flowchart showing a modification of the rank-up flag setting program of FIG.

10 is a flowchart showing another modification of the rank-up flag setting program of FIG.

11 is a flowchart showing another modification of the rank-up flag setting program of FIG.

[Explanation of symbols]

10 ... Inside, 20 ... Refrigerating device, 21 ... Compressor, 22 ... Condenser, 23 ... Temperature automatic expansion valve, 24 ... Evaporator, 25 ... Electric motor, 26 ... Cooling fan, 27 ... Temperature sensing tube, 28 ... Internal fan, 30 ... Operation control device, 31 ... Inverter circuit, 34 ... Microcomputer, 35 ... Internal temperature sensor, 36 ... Current detector, 38 ... Internal temperature setter, 41,
42 ... Pressure sensor, 43, 44 ... Temperature sensor.

Claims (8)

[Claims] 1. A refrigerant discharged from a compressor driven by an electric motor is circulated through a condenser and an evaporator, and a temperature automatic expansion valve provided between the condenser and the evaporator is used to It is applied to a refrigeration system in which the flow rate of the refrigerant supplied to the evaporator is automatically adjusted according to the temperature downstream of the evaporator, and the rotation speed of the electric motor is switched and controlled according to the load. In a control device for a refrigerating device, switching the rotation speed of the electric motor to a higher side on the condition that a current detection unit that detects a current flowing through the electric motor and the detected current is in a decreasing state. A control device for a refrigerating apparatus, which is provided with a switching control means for permitting the above. 2. The control device for a refrigerating apparatus according to claim 1, wherein the switching control means sets the detected current to a predetermined value in addition to the condition that the detected current is in a decreasing state. A control device for a refrigerating apparatus, wherein the rotation speed of the electric motor is allowed to be switched to a higher side on condition that the value is less than a value. 3. A refrigerant discharged from a compressor driven by an electric motor is circulated through a condenser and an evaporator, and the temperature automatic expansion valve provided between the condenser and the evaporator is used to It is applied to a refrigeration system in which the flow rate of the refrigerant supplied to the evaporator is automatically adjusted according to the temperature downstream of the evaporator, and the rotation speed of the electric motor is switched and controlled according to the load. In a control device for a refrigeration system, a refrigerant pressure detecting means for detecting a refrigerant pressure downstream or upstream of the compressor, and a rotation speed of the electric motor on condition that the detected refrigerant pressure is in a reduced state. A control device for a refrigerating apparatus, which is provided with a switching control means for permitting switching to a higher side. 4. The control device for a refrigerating apparatus according to claim 3, wherein the switching control means includes a condition that the detected refrigerant pressure is in a decreasing state, and the detected refrigerant pressure is The control device for a refrigerating device is characterized in that the rotation speed of the electric motor is allowed to be switched to a higher side on the condition that is less than a predetermined value. 5. A refrigerant discharged from a compressor driven by an electric motor is circulated through a condenser and an evaporator, and the temperature automatic expansion valve provided between the condenser and the evaporator is used to It is applied to a refrigeration system in which the flow rate of the refrigerant supplied to the evaporator is automatically adjusted according to the temperature downstream of the evaporator, and the rotation speed of the electric motor is switched and controlled according to the load. In a control device for a refrigerating apparatus, a temperature detecting unit that detects a temperature of the evaporator or a temperature downstream of the evaporator, and a rotation speed of the electric motor on condition that the detected temperature is in a reduced state. A control device for a refrigerating apparatus, which is provided with a switching control means that allows switching to a higher side. 6. The control device for a refrigerating apparatus according to claim 5, wherein the switching control means sets the detected temperature to a predetermined value in addition to the condition that the detected temperature is in a decreasing state. A control device for a refrigerating apparatus, wherein the rotation speed of the electric motor is allowed to be switched to a higher side on condition that the value is less than a value. 7. A refrigerant discharged from a compressor driven by an electric motor is circulated through a condenser and an evaporator, and the temperature automatic expansion valve provided between the condenser and the evaporator serves to It is applied to a refrigeration system in which the flow rate of the refrigerant supplied to the evaporator is automatically adjusted according to the temperature downstream of the evaporator, and the rotation speed of the electric motor is switched and controlled according to the load. In a control device for a refrigerating apparatus, a first temperature detecting means for detecting a temperature downstream of the evaporator, a second temperature detecting means for detecting a temperature of the evaporator, and a first temperature detecting means. And a temperature difference calculating means for calculating a temperature difference between the temperature downstream of the evaporator and the temperature of the evaporator detected by the second temperature detecting means, and the calculated temperature difference is in a decreasing state. To
A control device for a refrigerating apparatus, comprising: a switching control unit that allows switching of the rotation speed of the electric motor to a higher side. 8. The control device for a refrigerating apparatus according to claim 7, wherein the switching control means adds the calculated temperature difference in addition to the condition that the calculated temperature difference is in a decreasing state. The control device for a refrigerating device is characterized in that the rotation speed of the electric motor is allowed to be switched to a higher side on the condition that is less than a predetermined value.