JPH056111B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a cooling device that controls the temperature of a space to be cooled by variable speed operation of a compressor constituting a two-system refrigeration cycle.

(b) Conventional technology Traditionally, in female cooling devices, such as those used in cold storage, upper and lower temperature limits are determined above and below the set temperature, and the compressor of the refrigeration cycle is started at the upper temperature limit and stopped at the lower limit temperature. Since the temperature of the space to be cooled is configured to be the set temperature on average depending on the situation, the temperature of the space to be cooled fluctuates drastically and the stored articles are likely to deteriorate. FIG. 9 shows the time course of the temperature T _P of the storage room, which is the space to be cooled, when such a cooling device is used. In this case, the compressor is ON−
By turning off, the temperature T _P periodically fluctuates between an upper limit temperature T _H and a lower limit temperature T _L that are determined above and below the set temperature T _S. Furthermore, when defrosting of the evaporator of the refrigeration cycle starts at time _t20 , the temperature T _P rises rapidly.
Even if defrosting is finished and cooling operation is started at time _t21 , the temperature drops to the set temperature T _S at time _t22 .

To solve this problem, for example,
In the publication, the temperature T _P is substantially stably controlled to the set temperature T _S as shown in FIG. 10 by controlling the rotation speed of the compressor motor using an inverter circuit.

(c) Problems to be solved by the invention If the inverter circuit is used as described above, the temperature T _P can be stably controlled as shown in Figure 10, but in this case as well, the evaporator must be defrosted. . Since defrosting is started at time _t22 in FIG. 10 and the compressor is also stopped, the temperature T _P rises rapidly. Moreover, defrosting is finished at time t ₂₄ ,
Even if the compressor is restarted, the cooling capacity of the refrigeration cycle does not increase immediately, and the temperature of the cooler is also high, so it will take a long time for the temperature T _P to drop to the set temperature T _S. There was a problem where the time t ₂₅ was reached.

(d) Means for solving the problems The present invention has been made to solve the problems, and the structure of the present invention will be explained below with reference to Examples.

The cooling device R includes cooling units A and B each consisting of two independent refrigeration cycles, and a control device 11 controls the compressors CA and CB of the cooling units A and B at variable speeds using an inverter circuit 10. The control device 11 switches and operates the cooling units A and B alternately every M hours, and immediately defrosts the stopped evaporator 5 or 6. After the defrosting is completed, both compressors CA and CB are operated. is operated to powerfully cool the storage chamber 13. Thereafter, the operation of the evaporator 5 or 6 that had been stopped is stopped, and normal cooling operation is performed.

(E) Effect According to the present invention, while cooling the storage compartment with one cooling unit, the evaporator of the other cooling unit can be defrosted. Furthermore, after defrosting is completed, both cooling units perform powerful cooling to promote temperature reduction.

(F) Embodiments Next, embodiments of the present application will be explained with reference to the drawings. FIG. 1 shows a block diagram of the configuration of the cooling device R of the present application. A and B are cooling units each consisting of an independent refrigeration cycle, and each has a compressor.
CA, CB, condensers 1 and 2, pressure reducers 3 and 4, and evaporators 5 and 6 are successively connected to form separate refrigerant circuits. FA and FB are blowers for forcedly circulating cold air that has been heat exchanged with the evaporators 5 and 6, and 7 and 8 are blowers for cooling the condensers 1 and 2, respectively. Further, DA and DB are defrosting heaters for melting frost growing on the evaporators 5 and 6. The compressors CA and CB are driven by, for example, a three-phase induction motor, and the speed is variable depending on the output of a well-known inverter circuit 10, and the high temperature and high pressure gas refrigerant discharged from the compressors CA and CB is They each flow into condensers 1 and 2 and are condensed by heat radiation, and after being depressurized by pressure reducers 3 and 4, they flow into evaporators 5 and 6, where they are evaporated, exerting a cooling effect and causing compressors CA and CB.
They each return to

Reference numeral 11 denotes a control device composed of a microcomputer, which controls the output of a temperature detection device 14 that detects the temperature T _P in the storage chamber 13 of the storage 12, which will be described later, and a temperature setting that sets a desired temperature T _S of the storage chamber 13. The output of the device 15 is used as an input. Control device 1
1 generates a PID control frequency signal for the inverter circuit based on the outputs of the temperature detecting device 14 and the temperature setting device 15, or based on various timers that are included as functions and will be described later. PID control corrects the frequency signal based on the deviation of temperature T _P from the set temperature T _S , the slope of the change in temperature T _P , and the deviation of temperature T _{P from the set temperature T S for} a predetermined period of time.
The control device 11 controls the temperature T _P so that it substantially matches the set temperature T _S , and the control device 11 changes the frequency signal within the range of, for example, 30 Hz to 120 Hz, which is the output frequency of the inverter circuit 10. That is, the microcomputer calculates the difference (△T ₎ between the temperature T _P and the set temperature T _S at predetermined intervals and determines a predetermined proportional element correction amount based on this _value . If the frequency signal is high, the frequency signal is modified to increase the output frequency of the inverter circuit 10, and conversely, if it is low, the frequency signal is modified to decrease it. Also, the temperature T _P at each predetermined time
Calculate the predetermined differential element correction amount based on the rate of change of
By adding this correction amount to the proportional element correction amount in a direction that reduces the rate of change, the so-called overshoot of the temperature T _P near the set temperature T _P is reduced. Furthermore, the microcomputer calculates a predetermined integral element correction amount by adding the difference (△T) for a sufficiently long predetermined time, and adds (△T) to the proportional element correction amount in the direction of decreasing to set the set temperature T. Try to eliminate the steady difference between _S and temperature T _P. As a result, the temperature T _P is controlled to substantially match the set temperature T _S.
The inverter circuit 10 operates approximately in proportion to the frequency signal from the control device 11, for example from 0Hz.
It changes the output frequency up to 120Hz, and its output is connected to both compressors CA and CB via magnetic switches SW ₁ and SW _2, respectively. The control device 11 closes the magnetic switches SW ₁ and SW ₂ alternately at predetermined time intervals, as will be described later, based on a built-in switching timer as a function, and closes both at the same time if necessary. Furthermore, the control device 11 executes control of the defrosting heaters DA and DB as described later.

FIG. 2 shows a front view of the storage 12, and FIG. 3 shows a side sectional view. The inside of the storage room 13 of the storage room 12 is maintained at a desired set temperature T _S including the freezing temperature zone by a cooling device R. An inner box is built into an outer box that opens to the front, and a urethane or urethane material is placed between the two boxes. A heat insulating box 17 is constructed by loading glass wool or a heat insulating block with a vacuum inside, or by assembling heat insulating panels into a box shape, and the inside of this heat insulating box 17 is used as a storage room 13. There is. In the embodiment, the heat insulating box 17 is open to the front, but it may be opened upward, and the opening is closed by the heat insulating doors 18 and 19 so as to be openable and closable. Also, freezing temperature here refers to the temperature range below freezing before meat, fish, etc. freeze.
Typically this temperature ranges from approximately -1°C to -4°C. Compressors CA and CB, condensers 1 and 2, and blowers 7 and 8 of cooling units A and B are each housed in an insulating box 17.
The blower is installed in parallel on the top of the
FA, FB, evaporator 5, 6 and defrost heater DA,
AB is arranged on the top of the storage room 13, and the grill 2
Covered with 0. Grill 2 on the back of storage room 13
A cold air discharge port 23 is formed at the rear end of the air blowers FA and FB, and the blowers FA and FB rotate to suck the cold air in the storage chamber 13 through the suction ports 24 and 25 formed in the grille 20 in front of the blowers FA and FB. 23 discharges cold air into the storage chamber 13 as shown in FIG. or,
Although not shown, the control device 11 and the inverter circuit 10 are also attached to the upper surface of the heat insulating box 17.

Next, the operation of the cooling device R of the present invention will be explained with reference to FIGS. 4 to 7. 4 to 6 are flowcharts showing programs of the microcomputer of the control device 11, and FIG. 7 shows changes over time in the driving states of each device. When the power is turned on at time _t0 , the entire system is reset in step 30, and the A unit flag is set in step 31. Next, in step 32, the above-mentioned PID control is executed to determine the frequency signal H. Next, in step 33, the switching timer that the microcomputer has as its function is counted, and in step 34, it is determined whether the counting has finished or not. Judgment is negative, so step 40
Jump to and execute subroutine 1.

FIG. 5 shows subroutine 1. At step _S1 , it is determined whether or not the 2 unit flag is set. If not, the process proceeds to step _S2 , where it is determined whether or not the A unit flag is set. Since the A unit flag has been set in step 31, proceed to step _S2 and set the magnetic switch _SW1.
Close and operate cooling unit A. By closing the magnetic switch _SW1 , the output of the inverter circuit 10 is input to the compressor CA and the rotation speed is controlled. At the same time, the blower FA is operated and the inside of the storage chamber 13 is cooled by the evaporator 5.

After executing subroutine 1, it is determined in step 41 whether or not the defrosting flag is set, and if not, the process returns to step 32 and is repeated thereafter. At time _t1 , which is M hours after time _t0 , the switching timer stops counting (the counting time of the switching timer is M hours). The process then proceeds from step 34 to step 35 to reset the switching timer, and then in step 36 it is determined whether or not the A unit flag is currently set.Since it is set, the process proceeds to step 37 to reset the A unit flag. is reset, the defrosting flag is set in step 39, and the process proceeds to step 40. In subroutine 1, the A unit flag has been reset in step _S2 , so proceed to step _S5 , close magnet switch _SW2 , and turn on the compressor of cooling unit B.
Start operating the CB. Next, proceed to step 41,
Since the defrost flag is set, step 42
Proceed to and execute subroutine 2.

FIG. 6 shows subroutine 2. In step _S6 , it is determined whether or not the 2 unit flag is set. If not, the process proceeds to step _S7 , and it is determined whether the A unit flag is set. Since it has been reset, the process proceeds to step _S8 to remove it. frost heater DA
energizes to start defrosting the evaporator 5 of the cooling unit A. Next, in step _S9 , it is determined whether the evaporator 5 has reached a predetermined defrosting end temperature, and if not, the process returns to step 32 and repeats this process. That is, while the storage chamber 13 is being cooled by the cooling unit B, the evaporator 5 of the cooling unit A is defrosted. Therefore, the defrost heater DA when defrosting the evaporator 5
The rise in temperature of the storage chamber 13 due to heat generation can be suppressed to a low level.

When the temperature of the evaporator 5 reaches a predetermined defrosting end temperature at t ₂ while such a state continues (the control device 11 controls both the evaporators 5 and 6 by a sensor (not shown)
), from step _S9 , proceed to step _S12 , set the 2 unit flag,
In step _S13 , the current temperature T _P of the storage chamber 13 is read, and in step _S14 , the difference from the set temperature T _S (△T) is read.
Calculate, and in step _S15 , (△T) is, for example, −1.5.
Determine whether the temperature is below _T1 , such as ℃, and if not, proceed to step _S16 , and this time judge whether (△T) is below temperature _T2 , such as -0.2℃; If so, return to step 32. After that step S ₁
Since the 2-unit flag is set in step _S4 , both magnetic switches _SW1 and _SW2 are closed, and the compressors CA, CA and SW2 of both cooling units A and B are closed.
Drive a CB. Also, since the 2-nit flag is set in step _S6 , the process jumps to step _S13 , and the temperature (ΔT) is determined in the same manner as described above. Due to the cooling action of both cooling units A and B, the temperature T _P decreases (△
When T) reaches _T2 , the process proceeds from step _S16 to _S17 , reads the current frequency signal H _P , and proceeds to step _S18 .
For example, if the output frequency of the inverter circuit 10 is 50Hz
It is determined whether or not the frequency signal H ₀ is less than or equal to the frequency signal H 0 . If not, the process returns to step 32 . If the frequency signal H _P becomes less than H ₀ in subsequent step S ₁₈ , the process advances to step S ₁₉ . Also, before that, the temperature difference (△T)
If has reached T ₁ , proceed from step S ₁₅ to S ₁₉ ,
2 reset the unit flag, reset the defrost flag in step _S20 , and then proceed from step _S2 .
Proceed to _S5 to execute cooling by cooling unit B. This minimizes so-called undershoot.

That is, at time _t3 , (△T) is less than or equal to _T1 , and
When H _P becomes less than H ₀ or when (ΔT) becomes less than T ₂ , the cooling operation by both cooling units A and B is finished, and only cooling unit B returns to operation. The transition of temperature T _P from t ₁ to t ₃ above is shown in
As shown in the figure. When defrosting of the evaporator 5 is started at time _t1 , although the cooling unit B is in operation (naturally, the inverter circuit 10 generates an output at a frequency that maximizes the capacity of the compressor CB). , the cooling capacity does not increase immediately, so the temperature T _P increases somewhat, but if the compressor CB is not operated (Figure 10)
The temperature rise is suppressed to a minimum, and the temperature rise is kept to a minimum. When defrosting ends at time _t2 , there will be no further temperature rise, and cooling units A and B
The temperature decreases again by both cooling operations. At this time, a large amount of cold air that has exchanged heat with the evaporators 5 and 6 is supplied into the storage chamber 13, so the temperature T _P
will decline rapidly. That is, as a result, the time required from time t ₂ to t ₃ is reduced from time t ₂₁ in FIG.
t ₂₂ or the time required from time t ₂₄ to t ₂₅ in FIG. 10 is significantly shorter. Therefore, the temperature rise of the stored articles can be suppressed to a minimum, and quality deterioration can be prevented.

Thereafter, when the switching timer finishes counting at time _t4 , which is M hours after time _t1 , the process proceeds from step 36 to step 38, where the A unit flag is set. Therefore, in step _S2 , the program proceeds to step _S3 , where the magnetic switch _SW1 is closed and the operation of the cooling unit A is started. Also, since the defrost flag was set in step 39, steps 41 to 42
Since the A unit flag is set in step _S7 , the process proceeds to step _S10 , where the defrosting heater DB is energized and the evaporator 6 is defrosted. Thereafter, operations similar to those described above are performed.

In the embodiment, the period in which both cooling units A and B are operated after the end of defrosting is determined by the temperature and frequency signal values, but the timer is not limited to this. You may also set a period.

(g) Effects of the Invention As described above, the present invention controls the temperature of the space to be cooled by variable-speed operation of the compressor of the refrigeration cycle, so stable temperature control with little fluctuation is possible. In addition, in the present invention, two independent refrigeration cycles are alternately switched and operated, and one evaporator is defrosted while the other evaporator is being cooled, so the temperature rise in the space to be cooled during defrosting is also avoided. In addition, since both refrigeration cycles are operated for a predetermined period of time after defrosting, the temperature decrease after defrosting is accelerated and the time required to return to the set temperature can be shortened. This makes it possible to further reduce temperature fluctuations.

[Brief explanation of the drawing]

1 to 8 show embodiments of the present invention, and FIG. 1 is a block diagram showing the configuration of a cooling device;
Figure 2 is a front view of the storage area excluding the door, Figure 3 is a side sectional view of the storage area, Figures 4 to 6 are flowcharts of the microcomputer of the control device, and Figure 7 shows the operating status of each device. Figures 9 and 8 are diagrams showing the time course of the temperature in the storage room, and Figures 9 and 10 are diagrams showing the temperature change over time in the storage room.
This figure is a diagram showing the temperature of the storage chamber by a conventional cooling device corresponding to FIG. 8. R... Cooling device, A, B... Cooling unit,
CA, CB...Compressor, DA, DB...Defrost heater,
5, 6...Evaporator, 10...Inverter circuit, 1
1...control device, 12...storage, 13...storage room.

Claims (1)

[Claims] 1. In a cooling device that controls the temperature of a space to be cooled to a set value by variable-speed operation of a compressor that constitutes a refrigeration cycle, the cooling device has two independent refrigeration cycles and a system that controls the refrigeration cycle. The control device is provided with a control device that operates alternately by switching at predetermined time intervals, and the control device defrosts the evaporator of the stopped refrigeration cycle among the refrigeration cycles, and also defrosts the evaporator of the stopped refrigeration cycle and A cooling device characterized in that the refrigeration cycle is controlled to be stopped after being operated for a predetermined period of time.