JP3255455B2 - Cooling system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling system, and more particularly to a control system for a compressor and a cooling air circulation fan.

[0002]

2. Description of the Related Art Conventionally, in a cooling device in which a refrigerant is compressed by a compressor, the refrigerant is liquefied by a condenser, the refrigerant is evaporated by an evaporator, and the inside of the refrigerator is cooled by the heat of vaporization, the compressor is synchronized with the temperature in the refrigerator. And the cooling air circulation fan were operated / stopped at the same time. In this synchronous control, the temperature inside the refrigerator and the operation of the compressor and the cool air circulation fan /
The relationship with the stop is shown in FIG. Set the stop temperature and operating temperature so that the temperature becomes ± α, and stop the compressor and cool air circulation fan if the inside of the refrigerator becomes lower than the stop temperature.If the inside of the refrigerator becomes higher than the operating temperature, circulate the compressor and cool air. By operating the fan, the internal temperature was set to the set temperature ± α.

[0003]

In the synchronous control of the compressor and the cool air circulation fan as described above, liquefied refrigerant remains inside the evaporator when the compressor is stopped. FIG. 5 shows the relationship between the inside temperature and the evaporator temperature when the compressor and the cool air circulation fan are simultaneously operated / stopped. In the figure,
The circled portion is a portion that can be cooled by evaporation of the residual liquefied refrigerant. Thus, in the conventional cooling device, after the compressor is stopped, the heat that can be taken by evaporating the residual liquefied refrigerant inside the evaporator is wasted.

[0004] The present invention has been made in view of the above,
It is an object of the present invention to provide a cooling device that can save power by using a liquefied refrigerant in an evaporator after the compressor is stopped for cooling the inside of the refrigerator.

[0005]

In order to solve the above problems, the present invention firstly compresses a refrigerant by a compressor, liquefies the refrigerant with a condenser, evaporates the refrigerant with an evaporator, and generates cool air. Further, in a cooling device that circulates cool air by operating a cool air circulation fan to cool the inside of the refrigerator, a refrigerant cooling calorie estimating means for estimating a cooling heat amount of a liquefied refrigerant held inside the evaporator, and setting the inside of the refrigerator. The required amount of cooling heat in the refrigerator for estimating the amount of cooling heat required for cooling to the temperature, and the inside of the refrigerator by the liquefied refrigerant inside the evaporator from the estimated value of the refrigerant cooling heat amount estimating device and the estimated value of the required cooling heat amount in the refrigerator. A compressor control unit that stops the compressor when it becomes possible to cool to the set temperature, and the cool air circulation fan when the inside of the refrigerator reaches the set temperature. And summarized in that and a cold air circulation fan control unit for stopping.

Secondly, in the above-mentioned first configuration, the refrigerant cooling heat amount estimating means and the internal cooling heat amount estimating means are arranged so that the internal temperature of the refrigerator becomes the set temperature when all the liquefied refrigerant in the evaporator evaporates. The gist of the present invention is to have a guess correction signal output means for outputting a correction signal.

[0007]

In the above configuration, first, the compressor is:
The operation is stopped when the inside of the refrigerator can be cooled to the set temperature by the liquefied refrigerant held in the evaporator. Thereafter, when the inside of the refrigerator reaches the stop temperature due to the evaporation of the remaining liquefied refrigerant in the evaporator, the cool air circulation fan is stopped. As a result, all the liquefied refrigerant inside the evaporator when the compressor is stopped is used for cooling the inside of the refrigerator, and power can be saved.

[0008] Second, the estimation and correction is performed so that the temperature in the refrigerator after evaporation of the residual liquefied refrigerant and the actual temperature in the refrigerator are estimated from the estimated values of the refrigerant cooling heat estimation device and the required cooling heat estimation device. The correction is made by the correction signal from the signal output means. As a result, errors due to estimation are eliminated, and more efficient control is realized.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows the configuration of the control device. Liquid refrigerant amount estimating unit 1 as refrigerant cooling heat amount estimating means for estimating the amount of liquefied refrigerant in the evaporator at the present time, evaporating time calculating unit 2 for calculating the time until the estimated liquefied refrigerant completely evaporates, A temperature change calculator 3 for calculating the internal temperature at the time when the liquefied refrigerant completely evaporates from the temperature, a compressor controller 4 for stopping the compressor when the calculated internal temperature reaches the stop temperature, an internal temperature. The cooling air circulation fan control unit 5 that stops the cooling air circulation fan when the temperature actually reaches the stop temperature and corrects the calculation data so that the internal temperature correctly reaches the set temperature when all the liquefied refrigerant inside the evaporator evaporates. And a refrigeration capacity correction unit 6 as an estimated correction signal output unit. From the estimated time until the liquefied refrigerant evaporates completely and the calculation of the internal temperature after that time, it is possible to estimate the amount of cooling heat required to cool the internal space to the set temperature. The evaporating time calculation unit 2 and the in-compartment temperature change calculation unit 3 constitute an in-compartment required cooling heat amount estimating unit.

Next, the control operation of the cooling device by the control device configured as described above will be described with reference to the flowchart of FIG.

When the power is turned on, the compressor and the cool air circulation fan are operated, and at the same time, the refrigerating capacity is initialized (steps 11, 12, and 13). after this,
The liquid refrigerant amount estimating unit 1 estimates the liquefied refrigerant amount Gl inside the evaporator at the present time (step 14). The average dryness x of the refrigerant in the evaporator is expressed by the following equation.

X = a ⁻³ .Ta + b Ta: room temperature (° C.) a, b: changed by refrigerator Assuming that the refrigerant flow in the evaporator is an annular flow, the average void fraction fg is obtained from the Levy equation. Here, the saturated liquid specific weight γl and the saturated gas specific weight γg can be obtained by obtaining the refrigerant pressure Ps in the evaporator from the evaporator inlet temperature using a refrigerant physical property value table.

[0013]

[Number 1] x = {fg (1-2fg) + fg · [(1-2fg) 2 + fg {2γl / γg (1-fg 2) + fg (1-2fg)}] 1/2} / {2γl / γg (1-fg ² ) + fg (1-2fg)｝ γl: Saturated liquid specific weight (Kg / m ³ ) γg: Saturated gas specific weight (Kg / m ³ ) The liquid refrigerant amount Gl in the evaporator is obtained by the following equation. Can be.

Gl = (1−fg) · γl · Ve Ve: evaporator inner volume (m ³ ) From the above, as a result of calculation for a certain refrigerator Z, it can be estimated that, for example, the amount of liquid refrigerant at room temperature 30 ° C. is 126 g. Was.

A time t until the amount of the liquid refrigerant in the evaporator estimated by the evaporation time calculating section 2 is completely evaporated is calculated (step 15). Cooling heat Q of liquid refrigerant in evaporator
l can be obtained by the following equation. Here, the refrigerant pressure P
The latent heat Δh at s can be obtained from a refrigerant physical property value table.

Ql = Gl.Δh Δh: Latent heat (Kcal / Kg) at the refrigerant pressure Ps The time t until the liquid refrigerant amount is completely evaporated can be obtained by the following equation. The refrigerating capacity Φl of the evaporator varies depending on each refrigerator and is determined by experiments.

T = Ql / φl × 3600 φl: Refrigerating capacity of evaporator (Kcal / h) From the above, the evaporation time of the refrigerant was calculated to be 126 seconds.

The internal temperature change calculator 3 calculates from the current internal temperature what the temperature will be after the time t when the liquid refrigerant has completely evaporated (step 16). When the heat balance equation of the refrigerator is established, CdT / dt = KA · (Ta-T) -Φl T: temperature in the refrigerator (° C) C: heat capacity in the refrigerator (Kcal / ° C) A: refrigerator surface area (m ²⁾ ) K: Refrigerator heat transfer coefficient (Kcal / hm ² ℃)

## EQU2 ## dT / dt + KAAT / C = (KATA
−Φl) / C

## EQU3 ## T = T0.exp ((-K.A / C) t) + T
a-Φl / K · A T0: Internal temperature at t = 0 (° C.) Each constant of refrigerator Z is obtained by experiment, and the internal temperature at time t after the evaporation time of the refrigerant is calculated. Calculating from the inside temperature of -20 ° C, the temperature was -23.1 ° C at 30 ° C in the outside air.

The compressor control section 4 stops the compressor when the temperature inside the refrigerator after the time t outputted by the calculation becomes equal to or lower than the stop temperature (steps 17 and 18). If the temperature has not reached the stop temperature, the calculation is performed again from the estimation of the liquid refrigerant amount in the evaporator in step 14. Further, the cool air circulation fan controller 5 stops the cool air circulation fan when the liquid refrigerant in the evaporator evaporates and the inside of the refrigerator actually reaches the stop temperature (steps 19, 20, 21). After the compressor and the cool air circulating fan are stopped, the compressor control unit 4 and the cool air circulating fan control unit 5 operate the compressor and the cool air circulating fan again when the internal temperature reaches the operating temperature. Hereinafter, the same operation / stop cycle is repeated,
All the heat stored in the evaporator can be used for cooling the inside of the refrigerator.

However, if the calculated internal temperature after time t is higher than the actual internal temperature, the cooling air circulation fan is required until the amount of cooling heat of the liquefied refrigerant held in the evaporator is used up. Is stopped, and the effect of the present embodiment cannot be sufficiently obtained. Conversely, if the calculated internal temperature after time t is a value lower than the actual internal temperature, after the compressor is stopped, the internal temperature may rise without reaching the stop temperature. is there. Therefore, it is necessary to make a correction so that the inside temperature after the time t obtained by the calculation becomes equal to the actual inside temperature. The refrigeration capacity correction unit 6 performs this correction by changing the refrigeration capacity Φ1 determined by experiment (step 22). When the internal temperature reaches the stop temperature earlier than the calculated time t after stopping the compressor, the refrigerating capacity Φ1 is increased by ΔΦ. Conversely, if the internal temperature does not reach the stop temperature even after the calculated time t has elapsed, the refrigerating capacity Φl is changed to Δ
Φ is reduced. By correcting the calculation data in this way, it is possible to eliminate errors due to the calculation and perform efficient control.

FIG. 3 shows the relationship between the inside temperature and the evaporator temperature when the compressor and the cool air circulation fan of this embodiment are operated / stopped, as described above. The control of the cool air circulation fan is stopped when the inside of the refrigerator becomes equal to or lower than the stop temperature, and is operated when the internal temperature becomes equal to or higher than the operating temperature. On the other hand, the compressor is stopped when the inside of the refrigerator can be cooled down to the set temperature by the liquefied refrigerant in the evaporator. FIG. 4 shows the flow of cool air during operation of the cool air circulation fan 25 in the refrigerator. The cool air is blown up by the cool air circulation fan 25 and is forcibly sent to the freezing room 26, the refrigerating room 27 and the like for cooling. However, when the cool air circulation fan 25 stops, the cool air of the evaporator 24 naturally flows back into the vegetable / bottle room 28, abnormally lowers the temperature of the vegetable / bottle room 28, and may adversely affect the indoor vegetables. . However, in the present embodiment, when the cool air circulation fan 25 is stopped, the cooling capacity of the evaporator 24 is almost zero, and it is possible to minimize the backflow of the cool air.
Temperature change can be reduced.

[0022]

As described above, according to the present invention,
First, the compressor is stopped when the inside of the refrigerator can be cooled down to the set temperature by the liquefied refrigerant held in the evaporator, and the cool air circulation fan is thereafter cooled by the evaporation of the residual liquefied refrigerant inside the evaporator. Since the operation is stopped when the temperature actually reaches the set temperature, all the liquefied refrigerant in the evaporator after the compressor is stopped is used for cooling the inside of the refrigerator, thereby saving power.

Secondly, the refrigerant cooling heat estimating means and the required cooling heat amount estimating means are corrected so that the inside temperature of the evaporator when the compressor is stopped and the liquefied refrigerant in the evaporator has completely evaporated is the set temperature. Therefore, an error caused by the estimation is eliminated, and more efficient control can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a control device in an embodiment of a cooling device according to the present invention.

FIG. 2 is a flowchart illustrating a control operation of the cooling device by the control device.

FIG. 3 is a timing chart showing operation / stop timings of a compressor and a cool air circulation fan in the present embodiment.

FIG. 4 is a diagram showing a flow of cool air during a cool air circulation fan operation in the embodiment.

FIG. 5 is a timing chart showing operation / stop timings of a compressor and a cool air circulation fan in a conventional cooling device.

[Explanation of symbols]

1 Liquid refrigerant amount estimating unit (refrigerant cooling heat amount estimating means) 2 Evaporation time calculating unit 3 Internal temperature change calculating unit which constitutes the required internal cooling heat amount estimating unit together with evaporation time calculating unit 4 Compressor control unit 5 Cooling air circulation fan control unit 6. Cooling capacity correction unit (estimated correction signal output means)

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-165557 (JP, A) JP-B-62-20463 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) F25B 1/00

Claims (2)

(57) [Claims] 1. A cooling system in which a refrigerant is compressed by a compressor, the refrigerant is liquefied by a condenser, the refrigerant is evaporated by an evaporator to generate cool air, and cool air is circulated by operating a cool air circulation fan to cool the inside of the refrigerator. In the apparatus, a refrigerant cooling heat amount estimating means for estimating a cooling heat amount of the liquefied refrigerant held in the evaporator, and a required cooling heat amount estimating means for estimating a cooling heat amount required for cooling the inside of the refrigerator to a set temperature. And a compressor control unit that stops the compressor when the inside of the refrigerator can be cooled to a set temperature by the liquefied refrigerant inside the evaporator from the estimated value of the refrigerant cooling calorie estimating means and the estimated required cooling calorie in the refrigerator, A cooling air circulating fan control unit for stopping the cooling air circulating fan when the inside of the refrigerator reaches a set temperature. Location. 2. An estimated correction signal output for outputting a correction signal to the refrigerant cooling heat amount estimating means and the required internal cooling heat amount estimating means so that the inside temperature of the refrigerator becomes a set temperature when all the liquefied refrigerant inside the evaporator evaporates. 2. The cooling device according to claim 1, further comprising means.