JPH0195255A - Protective system of air conditioner - Google Patents

Abstract

PURPOSE: To eliminate leakage of a refrigerant and to easily detect the shortage of the refrigerant by performing a protection operation when the temperature difference between a temperature to be detected after a specific period of time passes after a compressor starts operating and a temperature being detected when the compressor starts operating is at a specified value or less. CONSTITUTION: The activation treatment of a microcomputer is made, and a value and a current value, a room temperature, and a coil temperature that are operated or set by a key input part are inputted and stored. When a compressor operates once, a timer counts time. When the timer counts two seconds, the conduction of all electrical equipment is shut off and a failure display is made when 5A or larger current is not flowing for a rated current of 6-7A. When the timer counts further three minutes, it is judged to be normal when 'a coil temperature at three minutes before < a current coil temperature' is established on heating and when 'the coil temperature at three minutes before > the current coil temperature' is established on cooling. A protection operation is executed when the above conditions cannot be established.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a protection system for an air conditioner having a refrigeration cycle.

(b) Conventional technology In general, conventional protection methods include
There was something like the one described in Publication No. 5. This bulletin is written in fII! The most popular type had a float switch installed in the receiver tank, and when there was a shortage of refrigerant, a signal from the float switch would turn on a warning lamp.

(8) Problems to be Solved by the Invention In the conventional refrigerant shortage detection system configured as described above,
It is necessary to provide a float switch in the receiver tank, and there is a problem in that refrigerant tends to leak from the connection part of the float switch.

In view of these problems, the present invention provides a protection system that does not have a connection that can cause refrigerant leakage, and that can detect refrigerant shortage from temperature fluctuations in the heat exchanger and provide protection.

(d) Means for Solving the Problems The present invention provides an air conditioner having a refrigeration cycle in which a compressor, a condenser, a pressure reducing device, and an evaporator are sequentially connected in a ring through refrigerant piping. It has a temperature detector that detects the temperature of This protects the compressor by stopping the compressor when the temperature difference is below a certain value.

(*) Effect When using the protection system configured as described above, the temperature of the condenser or evaporator before and after the compressor starts operating, and the temperature of the condenser or evaporator after a predetermined period of time from the start of operation. If the temperature difference is below a certain value, the compressor is stopped and a protective operation is performed. Therefore, when there is a shortage of refrigerant in the refrigeration cycle, the temperature increase (or temperature decrease) in the heat exchanger due to compressor operation becomes slower (or smaller), and the temperature of the heat exchanger after a predetermined period of time increases. Since the fluctuation range is below a certain value, refrigerant shortage can be detected.

(f) Examples Examples of the present invention will be described below based on the drawings. Figure 2 is a schematic diagram of a heat pump air conditioner using the device of the present invention, where 1 is a compressor, 2 is a four-way valve, 3 is an indoor heat exchanger (user side heat exchanger), and 4 is a capillary tube. ,
5 is an outdoor heat exchanger (heat source side heat exchanger), 6 is an accumulator, and these are sequentially connected in a ring shape via refrigerant piping to constitute a refrigeration cycle. When the direction of the four-way valve 2 is in the state shown by the solid line in the figure (when ON), the high-temperature, high-pressure refrigerant discharged from the compressor 1 condenses in the indoor heat exchanger 3, releases condensation heat, and flows into the conditioned room. After being evaporated in the outdoor heat exchanger 5, the air is sucked into the compressor 1 again through the accumulator 6. Furthermore, when the direction of the four-way valve 2 is in the state shown by the dotted line in the figure, the high temperature and high pressure refrigerant discharged from the compressor 1 is condensed in the outdoor heat exchanger 5 and evaporated in the indoor heat exchanger 3. Performs cooling operation in the conditioned room. Reference numeral 7 denotes an indoor air blower, which is provided at a position where air can be blown to the indoor heat exchanger 3. Note that this air blower may be configured to be able to switch the air volume between a small air volume, a medium air volume, and a large air volume. Reference numeral 8 denotes an outdoor side blower device, which is provided at a position where air can be blown to the outdoor side heat exchanger 5. Note that this air blower may be configured to be able to switch the air volume into two levels: small air volume and old air volume.

The compressor 1, four-way valve 2, indoor blower 7, and outdoor blower 8 are controlled by a coil temperature detector 1 that detects the detected value of the indoor temperature detector 10 and the temperature of the indoor heat exchanger 3.
This is performed by the control device 12 based on the detected value of No. 1.

FIG. 1 is an electrical circuit diagram of a main part of the control device shown in FIG. 2. In this figure, 13 is a microprocessor, which mainly controls the cooling or heating operation by comparing the room temperature detected by the room temperature detector 10 with a set temperature, and its main operations will be described later. Reference numeral 14 denotes a key power section, which includes a run/stop switch, a cooling/heating changeover switch, a room temperature setting switch, a timer time setting switch, and the like. Reference numeral 15 denotes a display section, which includes an operating lamp, a room temperature indicator, and the like.

16 is a resistor connected in series with the indoor temperature detector 10 (thermistor), and the connection point with the indoor temperature detector 10 is connected to the analog input terminal (A/D2) of the microcomputer. Note that this analog input terminal has an analog/digital converter inside. 17 is the coil temperature detector 11 (
The connection point with the fill temperature detector 11 is connected to the analog input terminal (A/D 3 ) of the microcomputer. 18 is a driver section, which is connected to terminals 0.1 of the microcomputer. The outputs from O4 to O4 are power amplified to drive relays 19 to 22. The relay 19 has a normally open contact piece 23, and the contact piece has a contact capacity of 3 (A). Therefore, the four-way valve 2 is connected to the AC power source via this normally open contact piece 23 and the connectors D and d. Note that the rated current of this four-way valve 2 is several tens of meters (A). Relays 20 and 21 each have normally open contacts 24 and 25, each of which has a contact capacity of 3 (A). Therefore,
The indoor air blower 7 includes this normally open contact piece 24 and the connector C,
The outdoor air blower 8 is connected to the AC power source via the normally open contact piece 25 and the connectors B and b. In addition, this indoor side blower device 7, outdoor side blower device 8
The rated current of each is 1 (A). The relay 22 has a normally open contact piece 26, and the contact capacity of the contact piece is 20 (A).

Therefore, the compressor 1 uses this normally open contact piece 26, the connector A, a
It is not connected to AC power through the Furthermore, this compressor 1
The rated current is about 6 to 7 (A).

A single-phase induction motor is used for the compressor 1, the indoor blower 7, and the outdoor blower 8, and a relay with a large contact capacity is used in consideration of rush current at the start of operation.

27 is a current detector, which outputs a DC voltage having a potential proportional to the current value detected by C, 728 (current transformer) to the analog input terminal (A/D1) of the microcomputer 13.

These C and T28 are provided at positions where the total current flowing through the compressor 1, the indoor side blower device 7, the outdoor side blower device 8, and the four-way valve 2 can be detected.

Note that 29 is a step-down transformer, and 30 is a rectification, smoothing, and stabilization circuit section.

In the above control circuit, the normal state is Funecta A-a.
, B-b, C-c, D-d, and E-e are connected, respectively.

FIG. 3 is an explanatory diagram showing the main operations of the microprocessor 13 shown in FIG. 1. First, in Step SI, the microcomputer is started up. Next, in Step S, the values operated or set by the key manual section (run/stop, cooling/heating switching, room temperature set value, etc.), current value, indoor temperature, coil temperature are checked. Analog input terminals (A/DI, A/D2, A/D3)
Next, in step S, the room temperature set value is compared with the room temperature to control ON-OFF of the compressor. Next, in step S4, it is determined whether this compressor is turned on for the first time since the start of operation. If it is not the first time, that is, if it is the second time or later, step S6
The operation of the indoor air blower and outdoor air blower will begin. At this time, if heating operation is being performed, the four-way valve is turned on.

When the compressor is operated for the first time, the process proceeds to step S, where a timer is counted. Note that this timer can be reset when the timer is counted for the first time. Next, in step S, it is determined whether two seconds have elapsed since the timer has counted. After 2 seconds (compressor startup time), the current value is set to 5 in step S.
(A) Determine whether or not the above is satisfied. At this time, only the compressor ON signal is still being output, and only the relay 22 shown at No. 1 I50 is energized. Therefore, if the connectors A to E and a to e are properly connected, the compressor 1 will be supplied with the rated current (
6~? (A)) is flowing. In this step Sm, 5 (
A) If it is determined that the above current is not flowing, proceed to the protective operation subroutine. This subroutine cuts off the power to all electrical equipment such as the compressor, and displays an abnormality indication, such as blinking an indicator light. Note that this operation is canceled by re-initialization. When a current of 5 (A) or more is detected, the process proceeds to step S and normal operation is performed. This step S is the same operation as step S described above.

Next, step S1. Then, it is determined whether the timer has counted three more minutes. If 3 minutes have elapsed, the process advances to step st1*st* depending on whether the heating operation is in progress or not. In step stt, 5111, the coil temperature 3 minutes ago (the coil temperature at the start of energization of the compressor or within several 10 seconds before and after) is checked. temperature) and the current coil temperature, and step S++
(When heating), the fill temperature 43 minutes ago is the current coil temperature.”
If it holds true, it is judged as normal, and step S+* (when cooling)
Then, if "Coil temperature 3 minutes ago>Current fill temperature" holds true, it is determined to be normal (there is enough refrigerant, and the temperature of the heat exchanger has changed as it circulates through the refrigeration cycle). When these conditions are not met (such as when a four-way valve is incorrectly connected or when there is a gas shortage during the refrigeration cycle), the above-mentioned protective operation subroutine is executed.

(G) Effects of the Invention The present invention provides an air conditioner having a refrigeration cycle in which a compressor, a condenser, a pressure reducing device, and an evaporator are sequentially connected in an annular manner through refrigerant piping. Compare the temperature of the evaporator and the temperature after a predetermined period of time has elapsed since the start of operation of the compressor, and if the difference between these temperatures is below a certain value, the refrigerant in the refrigeration cycle has decreased and the capacity is insufficient. Since there is no need to install a float switch that directly detects the amount of refrigerant or a pressure switch that detects the amount of refrigerant from the pressure of the refrigerant, it is possible to detect refrigerant shortage from temperature changes in the heat exchanger. It can be easily detected.

[Brief explanation of the drawing]

FIG. 1 is an electrical circuit diagram of the main part of the control device shown in FIG. 2, FIG. 2 is a schematic diagram of an air conditioner using an embodiment of the present invention, and FIG. 3 is a main part of the microcomputer shown in FIG. FIG. DESCRIPTION OF SYMBOLS 1... Compressor, 2... Four-way valve, 7... Indoor side blower, 8... Outdoor side blower, 10.
... Indoor temperature detector, 11... Coil temperature detector, 13... Microcomputer, 19 to 22... Relay, 23 to 26... Normally open contact piece, 27...
Current detector, 28...C,T.

Claims (1)

[Claims] (1) In an air conditioner having a refrigeration cycle in which a compressor, a condenser, a pressure reducing device, and an evaporator are sequentially connected in a ring through refrigerant piping, the air conditioner is equipped with a temperature detector to detect the temperature of the condenser or evaporator. , the temperature detected by the temperature sensor after a predetermined time has elapsed since the start of compressor operation is compared with the temperature detected by the temperature sensor at the time of start of compressor operation, and when this temperature difference is below a certain value, the compressor is activated. A protection method for air conditioners that is characterized by stopping operation and performing protective actions.