JPH0370155B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a defrosting control device for an air-cooled heat pump type air conditioner.

(Prior art) Defrosting control devices for air-cooled heat pump type air conditioners are disclosed in Japanese Patent Application Laid-open Nos. 54-100550 and 1982-10055.
There is a method known from Publication No. 20348, in which a temperature detector is installed at the outlet of the outdoor coil during defrosting operation, and when the temperature detected by this detector becomes higher than a predetermined value, defrosting is completed. The system determines that the defrosting process has been completed.

(Problem to be solved by the invention) A thermistor is generally used as the above-mentioned temperature detector, but when the temperature of the outdoor coil is detected by this thermistor, the defrosting is performed by bypassing the hot gas in the forward cycle. In equipment that performs defrosting, the temperature of the refrigerant gas has decreased at the end of defrosting, so there is little temperature change at the outlet of the outdoor coil, making it difficult to detect the degree of change, and the thermistor also has variations in detection performance. Normally, about 5°C is required at the end of defrosting compared to 0°C during defrosting, so by the time the thermistor detects a temperature change and issues a defrost end signal, defrosting has already ended. This causes the inconvenience that defrosting takes longer than necessary.

The present invention was developed in light of the fact that in the defrosting operation using the hot gas bypass method using the positive cycle, the defrosting time becomes long, resulting in problems such as a decrease in heating operation efficiency and energy consumption. By specifying the temperature detection part of the temperature detection means that detects that defrosting has been completed, and by making the defrost release setting temperature variable according to the outside air temperature, it is possible to accurately determine the point at which defrosting is completed. The purpose is to enable detection and achieve rational defrosting operation.

(Means for Solving the Problems) Accordingly, the present invention provides a heat pump type air conditioner that performs a defrosting operation in which hot gas is circulated through an outdoor coil 8 acting as an evaporator in a positive cycle, as shown in FIG. As shown in FIG.
The defrosting control device is constructed by the following.

The temperature detection means 1 is configured to detect the temperature (Te) of the central portion of the outdoor coil 8 and output an electric signal.

On the other hand, the defrost release temperature correction means 2 is configured to calculate a defrost release set temperature (T _D ) which is higher when the outside air temperature is low, and conversely outputs an electric signal when the outside air temperature is high. .

Next, the defrosting end command means 3 compares the temperature (Te) detected by the temperature detection means 1 with the defrost release set temperature (T _D ) outputted by the defrost release temperature correction means 2, The defrosting operation is configured to output an electric signal to end the defrosting operation when the temperature (Te) exceeds the latter (T _D ).

(Function) Since a temperature difference occurs in the central portion of the outdoor coil 8 depending on whether frost remains in the central portion or whether the frost has melted, the temperature detecting means 1 can accurately detect the frost melting situation in the central portion.

On the other hand, the state of frost on the outdoor coil 8 changes depending on whether the outside air temperature is high or low, so even if the frost has melted at the center, frost may remain at the coil outlet or may have already melted. ,fluctuate.

Therefore, by adding outside air correction to the temperature at the center of the outdoor coil 8 by the defrosting release temperature correction means 2, it is possible to always properly detect the end of defrosting without being affected by the amount of frost formed by the outside air temperature. is possible.

(Example) Hereinafter, an example of the present invention will be described with reference to the accompanying drawings.

FIG. 2 is a device circuit diagram of a heat pump type air conditioner according to an embodiment of the present invention, which includes a compressor 6, a four-way switching valve 7, an outdoor coil 8, a cooling pressure reducer 9, a heating expansion valve 10, It includes a check valve 11, an indoor coil 12, and an accurator 13 connected in parallel to the inflator valve 10, and are connected to each other in a reversible circulation manner through refrigerant piping to constitute a known heat pump air conditioner.

Note that 14 indicates an outdoor fan, and 15 indicates an indoor fan.

In the above air conditioner, the compressor 6 and the four-way switching valve 7
A bypass pipe 1 is connected between the discharge pipe that connects the outdoor coil 8 and the liquid pipe that connects the outdoor coil 8 and the cooling pressure reducer 9.
7, and a solenoid valve 16 and a resistance pipe 18 are interposed in series with this bypass pipe 17.

When it becomes necessary to defrost the outdoor coil 8 during heating operation, the bypass pipe 17 is connected to the solenoid valve 1.
The bypass flow rate at this time is determined by the diameter of the resistance pipe 18 and the solenoid valve 16, and the total amount of the discharged gas flows through the four paths during heating operation. The discharge gas flows through the switching valve 7 to the indoor coil 12, whereas in the case of defrosting operation, the discharged gas flows in a predetermined ratio between the indoor coil 12 side and the bypass pipe 17. Discharge gas (hot gas) to the outdoor coil 8 that acts as an evaporator.
As a result, the defrosting operation is performed indoors while the heating operation continues.

The compressor 6, the fans 14, 15, and the solenoid valve 16 of the air conditioner having the above configuration are controlled by a microcomputer, and the microcomputer 19 is basically CPU (central processing unit) 20, RAM 21,
It is composed of a ROM 22, an input port 23, and an output port 24.

A program to control the CPU 20 is written in the ROM 22, and according to this program, the CPU 20 takes in necessary external data from the input port 23 or inputs it to the RAM.
It performs arithmetic processing while exchanging data with 21, and outputs the processed data to the output port 24 as necessary.

Regarding the arithmetic processing of the CPU 20, those related to the defrosting operation will be explained below.
3 receives an electric signal from the thermistor 4 that detects the temperature of the outdoor coil 8 via an A/D converter, and a thermistor 5 that detects the outside air temperature.
electrical signals are input through an A/D converter.

On the other hand, a defrost start command signal and a defrost end command signal are output from the output port 24 to the solenoid 16S of the solenoid valve 16 via the A/D converter.

When a predetermined amount of frost grows on the outdoor coil 8 during heating operation, the thermistor 4 detects the drop in temperature and causes the CPU 20 to issue a command signal to start defrosting. The valve opens and hot gas flows into the outdoor coil 8 to start defrosting (a)
do. (See Figure 4).

The thermistor 4 is attached to the center of the outdoor coil 8 to detect the temperature at the middle of the coil.

The contents of the defrosting control of the program written in the ROM 22 are shown in a flowchart as shown in Fig. 4.Hereinafter, the defrosting control, especially the defrosting end control, will be explained based on this flowchart. .

At the same time as the start of defrosting (A), the defrosting operation time (t _D clock (B))
Further, the defrosting release set temperature (T _D ) is calculated (c) from the outside air temperature (T _G ) detected by the thermistor 5.

The set temperature (T _D ) is determined based on the formula T _D =-f×T _G +g, for example, f=1.4.
(constant) and g = 9 (constant), the result will be the diagram shown in Figure 5. For example, if the outside air temperature (T _G is -5℃ and 0℃, the set temperature (T _D teeth
Corrected to 16℃ and 9℃, respectively.

That is, when the outside air temperature (T _G ) becomes low, the defrost release setting temperature (T _D ) becomes high, and conversely, when it becomes high, it becomes low.

The calculation process (c) described above corresponds to the operation of the defrosting release temperature correction means 2.

The set temperature (T _D ) calculated in this way is the lower limit value (T _DMIN ) determined in advance.
For example, compare 5℃ and the upper limit value (T _DMAX ) with, for example, 15℃ (D), (E), if it is lower than the lower limit value, correct it to the lower limit value (T _DMIN ) (F), and on the other hand, if it is higher than the upper limit value. If so, correct it to the upper limit value ( _TDMAX ) (g).

Time comparison 4 to determine whether the operating time (t _D ) reaches the preset maximum time (t _DMAX ) as defrosting progresses
At the same time, compare the coil temperature (T _e ) detected by thermistor 4 to see if it is greater than the defrost release setting temperature (T _D ), and determine whether t _D > t _DMAX .
Depending on whether T _e > T _D , a defrosting end command signal is issued, and the power to the electromagnetic valve solenoid 16S is cut off to cancel defrosting (N).

In this way, the defrosting operation is completed and normal heating operation is resumed.

In addition, the temperature comparison (i) and the defrosting release command (nu) are
This corresponds to the operation of the defrosting end command means 3.

In this way, when the outside temperature (T _G ) at the time of starting defrosting is low, the amount of frost formation should naturally be large, so by correcting the set temperature (T _D ) higher, the operating time required for defrosting can be reduced. It is possible to accurately evaluate the temperature at the center of the coil at the time when the frost at the outlet of the outdoor coil 8 has finished melting, and the amount of frost should naturally be small when the outside air temperature (T _G ) is high. Therefore, by correcting the set temperature (T _D ) to a lower value, the defrosting time can be substantially shortened, and the temperature at the center of the coil at the end of defrosting can be accurately evaluated. The problem of insufficient or excessive defrosting remaining will be resolved.

(Effects of the Invention) As described in detail above, the present invention detects the end of defrosting based on the temperature at the center of the outdoor coil 8, and further corrects this temperature linearly with a negative coefficient, for example, based on the outside air temperature. This makes it possible to correctly detect that defrosting has been performed reliably, and compared to detection at the outlet, defrosting does not take an unnecessarily long time, and it also prevents insufficient defrosting. The energy saving effect is great.

Further, since the defrosting state can be reliably detected based on temperature changes, an inexpensive temperature detection element such as a thermistor can be used, and the detection accuracy can be maintained at a high level.

[Brief explanation of drawings]

Figure 1 is a block diagram showing the configuration of the present invention, Figure 2 is a block diagram showing the configuration of the present invention.
The figure is a device circuit diagram of an air conditioner according to an embodiment of the present invention,
FIG. 3 is a control circuit diagram, FIG. 4 is a flowchart showing a defrosting termination control mode, and FIG. 5 is a temperature diagram for explaining temperature correction of the defrosting release temperature correction means according to the present invention. . 1...Temperature detection means, 2...Defrosting release temperature correction means, 3...Defrosting end command means, 8...Outdoor coil.

Claims (1)

[Claims] 1. In a heat pump air conditioner that performs a defrosting operation in which hot gas is circulated through the outdoor coil 8 acting as an evaporator in a positive cycle, a temperature detection means 1 for detecting the temperature (Te) of the central portion of the outdoor coil 8; The lower the outside temperature (T _G ), the higher it is;
Conversely, the higher the value, the lower the defrost release setting temperature (T _D )
The defrost release temperature correction means 2 calculates and outputs the temperature (Te) detected by the temperature detection means 1 and the defrost release set temperature (T _D ) outputted by the defrost release temperature correction means 2. A defrosting control device comprising a defrosting termination command means 3 which terminates the defrosting operation when the former (Te) becomes equal to or higher than the latter (T _D ).