JPH05322425A - How to defrost an open showcase - Google Patents

Abstract

PURPOSE:To make it possible to start a defrosting at a necessary and appropriate time without being affected by the surrounding condition of a show case, and make a frost sensor unnecessary by determining the defrosting start time by detecting the temperature and static pressure in the chilled air circulating passage, which change accompanying with the grow of frost on a chilling apparatus. CONSTITUTION:For an open show case, a chilled air circulating passage 2 and air circulating passage 3 are formed to surround a commodity display chamber 1 in the main body of which the front surface is opened, and air which is chilled by a chilling apparatus 5 is circulated in the chilled air circulating passage 2 by the operation of a blowing fan 6. In this case, temperature sensors 14, 15 are respectively provided right before the blowout port of an air curtain 9 and right after the chilling apparatus 5. Then, at a controller, a difference DELTAt of detected temperatures t1, t2 of respective temperature sensors 14, 15 is acquired, and it is judged whether the difference DELTAt has reached a specified level T or not, and when it has become DELTAt>=T, a defrosting start command is generated. By this, a solenoid valve is turned off to stop the supply of a refrigerant to the chilling apparatus 5, and at the same time, power is connected to a defrosting heater to start the defrosting.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defrosting method for a cold air circulation type open showcase, and more particularly to a method for detecting the start time of defrosting.

[0002]

2. Description of the Related Art In order to defrost a cooler of a cool air circulation type open showcase, conventionally, a timer is used to start defrosting at a constant time interval.

[0003]

However, in the conventional method in which defrosting is started after a certain period of time irrespective of the surrounding environment, defrosting takes a lot of time due to a large amount of frost when the temperature is high and the humidity is high, so that the temperature inside the refrigerator is high. When the temperature rises excessively and the conditions are not good, there is a risk that ice banks will be generated.However, when the temperature is low and the humidity is relatively low, defrosting starts even though the amount of frost is small, which causes the temperature inside the refrigerator to rise unnecessarily. There was a problem. Therefore, an object of the present invention is to provide a defrosting method for an open showcase, which can always start defrosting at an appropriate time even if the surrounding environment changes.

[0004]

To achieve the above object, the present invention detects the difference between the air temperature near the air curtain outlet in the cold air circulation passage and the air temperature near the cooler outlet. Defrosting shall be started when the temperature difference expands to a certain level. Further, in order to achieve the above object, the present invention detects the static pressure in the cold air circulation passage, and this static pressure decreases to a certain level before the air curtain outlet, or becomes constant before the cooler. Defrosting shall be started when the level rises to.

[0005]

When the cooler is frosted, the capacity of the cooler is reduced, and the ventilation resistance is increased to reduce the amount of circulating air, so that the air temperature t ₁ near the air curtain outlet tends to rise as shown in FIG. On the other hand, the air temperature t ₂ near the outlet of the cooler
2 tends to decrease as shown in FIG. 2 due to the decrease in the amount of circulating air, which is a load on the cooler, and the temperature difference between them increases as frost forms. Therefore, it can be determined that defrosting is necessary when the temperature difference expands to a level T.

On the other hand, there is some static pressure in front of the air curtain outlet of the cold air circulation passage due to pressure loss in the commutator, but when the cooler frosts and the circulating air volume decreases, the static pressure is reduced. descend. Further, static pressure exists in front of the cooler due to the pressure loss, but the static pressure rises when the cooler is frosted and ventilation resistance increases. Therefore, when the static pressure changes to a certain level, it can be determined that defrosting is necessary.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS. 1, 3 and 4. FIG. 1 is a vertical sectional view of an open showcase, in which a cold air circulation passage 2 and an air circulation passage 3 are formed in a main body having a front opening so as to surround a product display chamber 1. Reference numeral 4 is a product display shelf. A cooler 5 and a blower fan 6 are installed in the cold air circulation passage 2, and a cool air curtain 9 is formed between an air outlet composed of a commutator 7 and an air inlet 8 by the cold air circulating in the direction of the arrow. There is. Further, a blower fan 10 is installed in the air circulation passage 3,
A protective air curtain 13 is formed between the air outlet formed of the commutator 11 and the air inlet 12 by the air circulating in the arrow direction.

First, an embodiment of a method for determining the defrosting start timing by detecting the difference between the air temperature near the air curtain outlet and the air temperature near the cooler outlet will be described. Reference numeral 14 denotes a temperature sensor (blowing air temperature sensor) provided immediately before the air curtain outlet (commutator 7) of the cool air circulation passage 2, and 15 denotes a temperature sensor provided immediately after the cooler 5 (cooler outlet air temperature). Sensor). As shown in the control block diagram of FIG. 2, these temperature sensors 14 and 15 are connected to the input / output control unit 16b of the showcase controller 16 including a microprocessor 16a. Further, the input / output control unit 16b includes a solenoid valve relay 1 for controlling on / off of a refrigerant supply solenoid valve (not shown) of the cooler 5.
7 and a heater relay 18 for controlling on / off of the defrost heater (not shown) are connected.

Under such a configuration, the controller 16
As shown in the flowchart of FIG.
And 15, the air curtain outlet air temperature t ₁ and the cooler outlet air temperature t ₂ are constantly input, and the difference (t ₁ −t
₂ ) It is determined whether or not the level has reached a certain level T (a value unique to the showcase). When t ₁ −t ₂ ≧ T, defrosting is started, and the solenoid valve relay 17 is turned on.
FF is performed to stop the supply of the refrigerant, and the heater relay is turned on to energize the defrost heater. The termination of defrosting is separately determined by detecting the surface temperature of the cooler 5.

Next, an embodiment of a method for determining the defrosting start timing by detecting the static pressure in the cold air circulation passage will be described.
Reference numeral 19 denotes a pressure sensor when installed in front of the commutator 7, and detects the static pressure p ₁ generated by the pressure loss at the commutator 7. The static pressure p ₁ decreases because the wind velocity in the cool air circulation passage 2 decreases when the cooler 5 is frosted and ventilation resistance increases. Therefore, when the static pressure drops to a certain level P (p
Defrosting is started when ₁ ≤ P ₁ ). Further, if the pressure sensor 19 is installed at this position, the pressure increase due to the dust clogging of the commutator 11 can be detected, and by setting an appropriate value, the alarm can be used together with the cleaning time alarm.

Reference numeral 20 denotes a pressure sensor when it is installed in front of the cooler 5, and detects the static pressure p ₂ generated by the pressure loss in the cooler 5. The static pressure p ₂ rises when the cooler 5 is frosted and ventilation resistance increases. Therefore, defrosting is started when the static pressure p ₂ rises to a certain level P ₂ (p ₂ ≧ P ₂ ). The block diagram when defrosting is started by pressure detection uses the pressure sensor 19 or 20 in place of the temperature sensor 14 or 15 in FIG. 2, and the flow chart in that case is shown in FIG. 3 at the air temperatures t ₁ and t _2. Instead of static pressure p ₁
Or to detect the p _2, it intended to start the defrosting when it becomes a constant value P ₁ or less or P ₂ or more, omitted because otherwise the same.

[0012]

As described above, according to the present invention, the defrosting start time is determined by detecting the temperature or the static pressure in the cold air circulation passage that changes as the cooler frosts. Defrosting can be started at a necessary and appropriate time without being affected by ambient conditions to reliably prevent an excessive temperature rise in the refrigerator and the formation of ice banks, and a special sensor such as a frost sensor is also available. It is unnecessary.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an open showcase showing an embodiment of the present invention.

FIG. 2 is a diagram illustrating a temperature change in a cold air circulation passage due to frost formation.

FIG. 3 is a control block diagram of the open showcase of FIG.

4 is a flowchart showing the control operation of FIG.

[Explanation of symbols]

 1 Product Display Room 2 Cold Air Circulation Passage 3 Air Circulation Passage 4 Product Display Shelf 5 Cooler 6 Fan 7 Commutator 8 Cold Air Suction Port 9 Air Curtain 10 Fan 11 Commutator 12 Air Suction Port 13 Air Curtain 14 Outlet Air Temperature Sensor 15 Cooling Outlet air temperature sensor 19 Pressure sensor 20 Pressure sensor

Claims (2)

[Claims] 1. In a cold air circulation type open showcase, the difference between the air temperature near the air curtain outlet in the cold air circulation passage and the air temperature near the cooler outlet is detected, and this temperature difference reaches a certain level. A defrosting method for an open showcase, which is characterized by starting defrosting when expanded. 2. In a cold air circulation type open showcase, the static pressure in the cold air circulation passage is detected, and this static pressure decreases to a certain level before the air curtain outlet, or becomes constant before the cooler. A defrosting method for an open showcase, which is characterized by starting defrosting when the temperature rises to the level.