JPH0221745Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a frost detection device that detects frost adhering to a cooler such as a refrigerator using a frost detector and defrosts the frost at a constant amount.

A conventional frost detection device A will be explained with reference to FIG.
1 is a metal casing with good heat conduction; 2 is a vibration surface formed by pasting a piezoelectric element 3 on the inner surface of the ceiling of the casing 1; an airtight plate 4 for airtightly dividing the vibrating part where the piezoelectric element 3 is located; and an epoxy resin. It is composed of a molding material 5 such as, and a lead wire 6 of the piezoelectric element 3.

The purpose of the frost detection device A is to detect frost formation by stopping oscillation when frost formation on the vibrating surface 2 reaches a certain amount. However, when the quality of frost changes due to changes in outside temperature and humidity, even if the amount of frost is the same, the elastic force that prevents oscillation differs depending on the quality of the frost, resulting in detection variations depending on the outside air conditions.

The object of the present invention is to provide an evaporator frost detection device that eliminates the above-mentioned drawbacks.

An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 2 is a plan view of an evaporator equipped with a frost detection device according to an embodiment of the present invention. In this figure, reference numeral 7 denotes an evaporator consisting of a fin 8 and refrigerant pipes 10 passing through end plates 9 on both sides of the fin 8;
1 is a fan that provides forced ventilation to the evaporator. 12 is a frost detector attached to a part of the evaporator 7.

The frost detector 12 will be explained in detail in FIG.
The frost detector 12 includes an oscillating section 13 that converts electrical signals into mechanical vibrations and a receiving section 14 that converts mechanical vibrations into electrical signals, which are provided facing each other at a predetermined interval. A roughly U-shaped support part 1
2' is connected. The oscillating part 13 and the vibration receiving part 14 are both made of a metal casing 1 with good thermal conductivity.
5, 15', a vibration surface 17, 17' formed by pasting piezoelectric elements 16, 16' on the inner surface of the casings 15, 15', and piezoelectric elements 16, 1
Airtight plate 18, 1 for airtightly dividing the vibrating part with 6'
8', molding material 19, 19' such as epoxy resin,
It consists of lead wires 20, 20' of piezoelectric elements 16, 16'.

Next, the frost detection circuit will be explained with reference to FIG. 21 is a DC power supply circuit that converts AC into DC. The oscillation circuit 22 is connected to the piezoelectric element 16 of the oscillation section 13, and causes the piezoelectric element 16 to oscillate at a constant oscillation level.

The vibration receiving circuit 23 is connected to the piezoelectric element 16' of the vibration receiving part 14, and detects an electric signal generated by the piezoelectric element 16' when mechanical vibration is applied to the vibration surface 17' of the vibration receiving part 14, and generates a defrosting signal. Output. 24 drives the relay R by the output of the vibration receiving circuit 23 to connect the evaporator defrosting heater 25 (defrosting device) and the compressor 2.
6 (the defrosting control device claimed in the utility model registration claims corresponds to the relay R and the drive circuit 24). The compressor 26 is connected to the power source via the normally closed contact Ra of the relay R, and the evaporator defrosting heater 25 is connected to the power source via the normally open contact Rb of the relay R.

The operation in such a configuration will be explained. When the amount of frost on the evaporator 7 is small, both vibration surfaces 17, 1 of the oscillating part 13 and the receiving part 14 of the frost detector 12
7', there is almost no frost, the oscillating section 13 is in an oscillating state, and the receiving section 14 is in a stopped state. Evaporator 7
As the frost progresses, the oscillating section 13 of the frost detector 12
and between both vibration surfaces 17 and 17' of the vibration receiver 14 is the third
When it is covered with frost as shown in a in the figure, the vibration of the oscillating part 13 is propagated to the vibration surface 12' of the receiving part 14, and the piezoelectric element 16' of the receiving part 14 converts the mechanical vibration into an electrical signal and the vibration receiving circuit 23 outputs a defrosting signal. Then, the drive circuit 24 is activated and the relay R is closed. In other words, the normally closed contact Ra is opened, the compressor 26 is disconnected from the power supply, the cooling operation is stopped, and the normally open contact Ra is opened.
Close Rb and energize the evaporator defrosting heater 25 to start frosting.

In this way, if frost closes the space between the vibrating surfaces 17 and 17' of the oscillating section 13 and the receiving section 14 of the frost detector 12, the vibration of the oscillating section 13 will definitely propagate to the receiving section 14 and frost formation will be detected. , it becomes possible to perform defrosting with a constant amount of frost formation. In addition, frost on both vibration surfaces 17, 1
Since it is always detected as long as the frost grows by the distance between 7' and 7', the difference in elastic force on the vibrating surfaces 17 and 17' due to frost quality is not a problem, and therefore the frost quality changes due to changes in outside temperature and humidity. However, there is no variation in the detected amount.

As is clear from the above explanation, the frost detection device of the present invention consists of a diaphragm as a part of the casing,
A frost sensor is arranged in the evaporator so that the vibrating surfaces of the vibrating plates of each of the oscillating part formed by fixing a piezoelectric element to the vibrating plate and the receiving part having the same structure face each other with a distance sufficient for frost growth. An oscillation circuit that causes the piezoelectric element of the oscillation section to oscillate at a constant oscillation level, and the space between the oscillation section and the vibration receiving section is closed by frost, and the vibration of the oscillation section is caused to oscillate at a constant oscillation level of the piezoelectric element of the vibration receiving section. a vibration receiving circuit that detects an electric signal emitted by a piezoelectric element when propagated and outputs a defrosting signal; and a defrosting control device that receives a defrosting signal from the vibration receiving circuit and drives a defrosting device of the evaporator. Because it is made up of more. Even if the quality of frost changes due to outside temperature, humidity, etc., frost detection can be performed only when the frost on the evaporator reaches a predetermined amount, eliminating unnecessary defrosting and improving the operating efficiency of refrigerators, etc. This can contribute to higher power savings.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventional frost detection device, FIG. 2 is a plan view of an evaporator having a frost detection device according to an embodiment of the present invention, FIG. 3 is a sectional view of the frost detection device, and FIG. 4 is a sectional view of the frost detection device of the present invention. FIG. 2 is a schematic electrical circuit diagram of a frost detection device. 7...Evaporator, 12...Frost detection device, 13...
Oscillating section, 14... Vibration receiving section, 16, 16'... Piezoelectric element, 17, 17'... Vibration surface, 22... Oscillation circuit, 23... Vibration receiving circuit, 24... Drive circuit.

Claims (1)

[Scope of utility model registration request] A part of the casing is constituted by a diaphragm, and a piezoelectric element is fixed to this diaphragm, and the oscillating part and the receiving part having the same configuration are separated from each other by a distance sufficient to allow frost to grow between the oscillating surfaces of the diaphragms. A frost detector placed opposite to each other on the evaporator, an oscillation circuit that causes the piezoelectric element of the oscillation section to oscillate at a constant oscillation level, and a space between the oscillation section and the oscillation receiver section are closed by frost, and the oscillation circuit oscillates at a constant oscillation level. a vibration receiving circuit that detects an electric signal generated by the piezoelectric element when the vibration of the vibration receiving part is propagated to the piezoelectric element of the vibration receiving part and outputs a defrosting signal; A frost detection device comprising a defrost control device that drives a defrost device.