JP2000081271A - Low-temperature show case - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-temperature show case which can start a defrosting operation according to the amount of frost formed on a cooler during a cooling operation. SOLUTION: There is provided a low-temperature show case 1 which carries out a cooling operation by blowing air to a cooler by means of a blower, and a defrosting operation for removing frost formed on the cooler during the cooling operation. The show case comprises motors 57a to 57c which each can control an operating current value so as to be varied according to the amount of frost formed on the cooler. Further, the show case comprises of a control means 100 which drives the blower for the cooler by means of the motors 57a to 57c, detects the operating current value flowing through each of the motors 57a to 57c, and starts the defrosting operation, based on the operating current value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-temperature showcase for performing a defrosting operation for removing frost formed on a cooler during a cooling operation.

[0002]

2. Description of the Related Art Conventionally, in a low-temperature showcase, after a cooling operation is continuously performed for a predetermined time (for example, 4 hours), a defrost operation is periodically performed or a defrost operation is performed at a predetermined time. It is generally set as follows.

In this case, for example, electricity is supplied to a defrost heater provided in the vicinity of the cooler, and the heat generated by the defrost heater is used to remove the frost formed in the cooler. The air whose temperature has risen due to the heat generated by the defrost heater and the like flows into the refrigerator, which may adversely affect the products displayed in the refrigerator, and the power consumption when the defrost heater is energized is large. It is desirable that the number of operations is small.

[0004]

The amount of frost formed in the cooler during the cooling operation per unit time varies depending on various conditions such as temperature, humidity, and operating conditions. Since the defrosting operation is set to be performed periodically or at a predetermined time, the defrosting operation is performed even if the frost amount of the cooler has not reached the frost amount at which the defrost operation should be performed, There has been a problem that the temperature of the product is unnecessarily increased and extra power is consumed. Also,
Even if the frost amount of the cooler has already reached the frost amount at which the defrost operation should be performed, the defrost operation may not be started, in which case the cooler is blocked by frost and cool air circulates in the refrigerator. There is a problem that sometimes does not.

Accordingly, an object of the present invention is to provide a low-temperature showcase that solves the above-mentioned problems of the conventional technology and can start a defrosting operation in accordance with the amount of frost formed in a cooler during a cooling operation. Is to do.

[0006]

According to the first aspect of the present invention,
In a low-temperature showcase that performs a cooling operation by blowing air to a cooler with a blower for the cooler and performing a defrosting operation to remove frost formed in the cooler during the cooling operation, the amount of frost formed in the cooler is reduced. Control means for driving the blower for the cooler with a motor capable of controlling to change the operating current value according to the operating current value, detecting an operating current value flowing through the motor, and starting a defrosting operation based on the operating current value. It is characterized by the following.

According to a second aspect of the present invention, there is provided a low-temperature showcase for performing a cooling operation by blowing air to a cooler with a blower for the cooler and performing a defrosting operation for removing frost formed on the cooler during the cooling operation. The cooler blower is driven by a DC motor that can be controlled to change an operation current value in order to maintain the rotation speed at a predetermined rotation speed according to the amount of frost formed in the cooler, and flows through the DC motor. Control means for detecting an operating current value and starting a defrosting operation based on the operating current value is provided.

According to these inventions, since the defrosting operation is started in accordance with the amount of frost formed in the cooler, the defrosting operation can be performed efficiently. In addition, since the useless defrosting operation is not performed, energy efficiency is improved.

According to a third aspect of the present invention, in the first or second aspect, a defrosting prohibition time period for prohibiting the defrosting operation is provided, and the control means controls the operation before the defrosting prohibition time period. In the step, it is determined whether or not the defrosting operation is required during the defrosting prohibition time period, and when it is determined that the defrosting operation is required during the defrosting prohibition time period, the defrosting prohibition time period is entered. The defrosting operation is performed before.

According to the present invention, when it is determined that the defrosting operation is required during the defrosting prohibition time period, the defrosting operation is performed before the start of the defrosting prohibition time period. Compared with the case where the defrosting operation is performed after the end, it is possible to prevent a decrease in the cooling capacity due to the clogging of the cooler during the defrost inhibition time period.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a low-temperature showcase according to the present embodiment. The low-temperature showcase 1 is a multi-stage open type having an open front surface. The table and the refrigerator (not shown) are connected via a refrigerant pipe or the like.

A storage room 5 is provided behind the opening 3 of the low-temperature showcase 1, and a four-stage display shelf 7 is attached to the storage room 5. Further, an inner cool air passage 9 and an outer cool air passage 11 are arranged side by side so as to surround the storage room 5, and a heat insulating wall 13 is formed so as to surround the outer cool air passage 11. A temperature sensor 15 for measuring the discharge cold air temperature is provided in the inner cool air passage 9 at the upper part of the case, and a cooler 17 is provided in the inner cool air passage 9 at the back of the case. A frost heater 19 is provided. An inner-layer cooler blower 21 and an outer-layer cooler blower 23 are attached to the inner-layer cool air passage 9 and the outer-layer cool air passage 11 at the lower portion of the case, respectively. For example, three blowers 23 for the outer layer cooler are arranged side by side in the width direction of the low-temperature showcase 1. In this embodiment,
A DC motor 57 driven by a DC power supply is used as a fan motor for the inner layer cooler blower 21 in the inner layer cool air passage 9 provided with the cooler 17. Reference numeral 25 denotes an electromagnetic valve that controls opening and closing of the supply of the liquid refrigerant to the cooler 17.

When the cooling operation is performed in the low-temperature showcase 1, the blower 21 for the inner layer cooler and the blower 23 for the outer layer cooler rotate. The cool air blown from the outer-layer cooler blower 23 circulates as shown by a dotted arrow, and forms an outer-layer air curtain on the front surface of the low-temperature showcase 1. On the other hand, the cool air blown from the inner-layer cooler blower 21 passes through the inner-layer cool air passage 9 as shown by the solid-line arrow, and the cooler 17 is cooled.
To enter. During the cooling operation, the supply and the stop of the liquid refrigerant are repeatedly performed inside the cooler 17, and the supply and the stop of the liquid refrigerant are performed at the discharge cool air temperature detected by the temperature sensor 15 (or at the discharge cool air temperature). The opening and closing of the solenoid valve 25 is performed based on the internal temperature corrected and calculated based on the above. The cool air that has entered the cooler 17 is cooled by the cooler 17 when the liquid refrigerant is supplied inside the cooler 17, and is not cooled by the cooler 17 when the liquid refrigerant is not supplied inside the cooler 17. Thereafter, the cool air moves in the direction of the solid line arrow, is blown out to the front of the storage room 5, forms an inner layer air curtain, cools the inside of the storage room 5, and returns to the inner layer cooler blower 21. During the cooling operation, the temperature of the cooler 17 decreases to 0 ° C. or less, so that frost is gradually formed in the cooler 17.

In this embodiment, a defrosting operation for removing the frost from the cooler 17 is performed, and the start and stop timings of the defrosting operation are determined by the control means 100 shown in FIG.

The control means 100 includes a temperature controller 51 having a microcomputer and the like. The temperature controller 51 detects the temperature of the discharged cool air (the temperature in the refrigerator) via the temperature sensor 15 and
9. Control the solenoid valve 25 and the like (for example, open and close the solenoid valve 25 during the cooling operation described above). The temperature controller 51 is connected to a master controller together with another low-temperature showcase (not shown), and the master controller and each low-temperature showcase (temperature controller) can communicate with each other bidirectionally. Performs centralized control and monitoring of showcases.

The temperature controller 51 is electrically connected to the three motor controllers 55a to 55c, and exchanges signals with the motor controllers 55a to 55c. Each of the motor controllers 55a to 55c controls the DC motors 57a to 57c for driving the three inner-layer cooler blowers 21 (FIG. 1).

FIG. 3 shows a control flow of the control means 100.

First, during the cooling operation, the temperature controller 51
Is the rotation speed set from the memory or the like of the device (the rotation speed that each DC motor 57a to 57c should maintain during the cooling operation)
, And sends the set rotation speed data to each of the motor controllers 55a to 55c, and sets the set rotation speed data in each of the motor controllers 55a to 55c (S1). Next, each of the motor controllers 55a to 55a
5c reads the current rotational speed of the DC motors 57a to 57c (hereinafter referred to as the operating rotational speed) (S2).

In the low-temperature showcase 1, as the amount of frost on the cooler 17 increases, the ventilation resistance of the inner cool air passage 9 increases, and the load on the blower 21 for the inner cooler also increases.
The operating rotational speed of the DC motors 57a to 57c decreases,
The amount of air flowing through the inner layer cool air passage 9 is reduced. Conversely, as the amount of frost on the cooler 17 decreases, the ventilation resistance of the inner layer cool air passage 9 decreases, and the load on the inner layer cooler blower 21 also decreases, so that the operating rotational speeds of the DC motors 57a to 57c increase, The amount of air flowing through the inner layer cool air passage 9 is reduced.

In the present embodiment, the motor controllers 55a to 55a-
55c controls the DC motors 57a to 57c to maintain the rotational speeds at the set rotational speeds.
This is performed every 7c.

Each of the motor controllers 55a to 55c
It is determined whether or not the operating rotational speed of the DC motor controlled by itself is equal to or lower than a set rotational speed (S3). When the operating rotational speed of the DC motor is equal to or lower than the set rotational speed, each of the motor controllers 55a to 55c increases the current value flowing through the DC motor (hereinafter, referred to as an operating current value) to increase the operating rotational speed (S4). ). If the operation rotation speed is higher than the set rotation speed in step S3, whether the operation rotation speed is equal to or higher than the set rotation speed + α1 (α1: predetermined rotation speed, set rotation speed + α1: upper limit rotation speed of the set rotation speed range) is determined. Is determined (S5), and the operating rotational speed is equal to the set rotational speed
If α1 or more, the operation current value is reduced to lower the operation rotation speed (S6).

Each of the motor controllers 55a to 55c
When step S4 or S6 is completed, the operation current value of the DC motor controlled by itself is detected, and the detected operation current value is transmitted to the temperature controller 51.

In this embodiment, the temperature controller 51
Determines the amount of frost on the cooler 17 based on the operating current values of the DC motors 57a to 57c controlled by the motor controllers 55a to 55c in this manner. It is assumed that a defrosting operation prohibition time period (for example, 11:00 to 13:00) in which the defrosting operation is prohibited is set in the temperature controller 51 in advance.

The temperature controller 5 receiving the operating current value
1 examines the current time and the defrost prohibition time zone, and determines the start time of the defrost prohibition time zone in which the current time is set to t minutes (t
Minute: time required for the defrosting operation) or not (S:
8). The temperature control controller 51 determines that the operating current value of the DC motors 57a to 57c is equal to the frosting current value-α2 (the frosting current value: a state in which the defrosting operation is to be started) t minutes before the start of the defrost inhibition time zone. Is determined to be greater than or equal to α2: a predetermined current value, a frost formation current value-α2: a current value that can be estimated to require the defrosting operation during the defrost inhibition time zone). (S9) If any of the operating current values of the DC motors 57a to 57c is greater than or equal to the frost current value -α2, the frost / blocking flag is set (S12). Temperature controller 5
When the frosting / blocking flag is set, 1 starts energization of the defrost heater 19 and closes the solenoid valve 25,
Start the defrosting operation.

As described above, when the temperature controller 51 determines that the defrosting operation is required during the defrosting prohibition period, the temperature controller 51 performs the defrosting operation before the start of the defrosting prohibition period.
A decrease in cooling capacity due to clogging of the cooler 17 during the defrost prohibition time period in which the defrost operation is prohibited is prevented.

If the current time is not t minutes before the start time of the defrost inhibition time zone in step S8, the temperature controller 51 determines that the operating current value of the DC motors 57a to 57c is greater than the frost current value. Is determined (S10).
When the operation current value of any of the DC motors 57a to 57c is equal to or greater than the frost current value, it is further determined whether or not the current time is in the defrost inhibition time zone (S11). If is not during the defrost inhibition time, the frosting / blocking flag is set (S12), and the defrosting operation is started.

In step S10, DC motors 57a-57
If the operating current value of c is smaller than the frost current value,
It is determined whether or not the operating current value is equal to or greater than the frost current value -α3 (α3: a predetermined current value, the frost current value -α3: a current value indicating that the defrosting operation can be completed). (S1
3) If the operating current value of any of the DC motors 57a to 57c is equal to or greater than the frost current value -α3, the frost / blocking flag is reset (S14), and the defrost operation is stopped.

As described above, as the amount of frost formed in the cooler 17 increases, the operating current value of the blower 21 for the inner layer cooler increases, and conversely, as the amount of frost formed in the cooler 17 decreases, the inner layer cooling decreases. The operating current value of the dexterous blower 21 is reduced. In the present embodiment, the start or stop timing of the defrosting operation is determined when the operating current value reaches a predetermined current value by utilizing such a change in the operating current value. The start or stop of the defrosting operation is executed in accordance with the frost amount of the vessel 17, and the defrosting operation can be performed efficiently. Further, since the useless defrosting operation is not performed, energy efficiency can be improved.

Although the present invention has been described based on one embodiment, the present invention is not limited to this. For example, in the present embodiment, the cooler 17 is provided only in the inner layer cool air passage 9.
However, in the case of a low-temperature showcase in which a cooler is provided in each of the inner cool air passage and the outer cool air passage, the blower for the inner cooler in the inner cool air passage and the blower for the outer cooler in the outer cool air passage are provided. DC motors may be provided, and the amount of frost formed on the cooler may be determined based on the operating current values of these DC motors.

[0031]

According to the first or second aspect of the present invention, the blower for the cooler is driven by a motor capable of controlling the operation current value in accordance with the amount of frost formed in the cooler. Control means for detecting the operating current value flowing through the cooling device and starting the defrosting operation based on the operating current value, so that the defrosting operation is started according to the amount of frost formed in the cooler, and the defrosting operation is efficiently performed. It can be performed. In addition, since the useless defrosting operation is not performed, energy efficiency is improved.

According to the third aspect of the invention, when it is determined that the defrosting operation is required during the defrosting prohibition time period, the defrosting operation is performed before the start of the defrosting prohibition time period. Compared with the case where the defrosting operation is performed after the end of the prohibited period, the reduction of the cooling capacity due to the clogging of the cooler during the defrost prohibited period can be prevented.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a structure of a low-temperature showcase according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a control unit.

FIG. 3 is a flowchart showing a control flow of a control unit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Low-temperature showcase 17 Cooler 21 Blower for inner layer cooler 57a-57c DC motor 100 Control means

Claims (3)

[Claims] 1. A low-temperature showcase that performs a cooling operation by blowing air to a cooler with a blower for the cooler and performs a defrosting operation for removing frost formed in the cooler during the cooling operation. Drive the blower for the cooler with a motor that can be controlled to change the operating current value according to the amount of frost,
A low-temperature showcase comprising a control means for detecting an operation current value flowing through the motor and starting a defrosting operation based on the operation current value. 2. A low-temperature showcase for performing a cooling operation by blowing air to a cooler with a blower for the cooler and performing a defrosting operation for removing frost formed on the cooler during the cooling operation. The cooler blower is driven by a DC motor capable of controlling the operation current value to maintain the rotation speed at a predetermined rotation speed in accordance with the amount of frost, and the operation current value flowing through the DC motor is detected. And a control means for starting a defrosting operation based on the operation current value. 3. A defrosting prohibition time period for prohibiting the defrosting operation is provided, and the control means needs to perform the defrosting operation during the defrosting prohibition time period before entering the defrosting prohibition time period. The defrosting operation is performed before the defrosting prohibition time zone is entered when it is determined whether or not the defrosting operation time is required during the defrosting prohibition time period. 2. The low-temperature showcase according to 2.