JPH0341751B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Field of Application> The present invention relates to a defrosting method for a heat pump air conditioner.

<Prior art> In a heat pump type air conditioner in which a refrigeration cycle is configured by sequentially connecting a compressor, a four-way switching valve, an outdoor heat exchanger, a throttling mechanism, an indoor heat exchanger, etc., the It is now possible to switch between cooling operation and heating operation. If frost forms on the outdoor heat exchanger during heating operation, the most common method is so-called reverse cycle defrosting, in which the four-way switching valve is switched to temporarily perform cooling operation to defrost. Since this reverse cycle defrosting switches the refrigeration cycle from heating to cooling, it takes a long time to defrost even when the amount of frost is small, so it is suitable when there is a large amount of frost. This method cannot be said to be very suitable when the amount of frost is small. In addition, so-called hot gas defrosting is also known, in which an outdoor heat exchanger is provided with a bypass line that can be opened and closed, and hot gas is sent to the outdoor heat exchanger for defrosting by opening this bypass line. It is difficult to secure a sufficient heat source for defrosting, and although it is suitable for cases with a small amount of frost that can finish defrosting in a short time, it is not suitable for cases with a large amount of frost. It could not be called a method.

<Objective of the invention> The present invention focuses on the characteristics of the two defrosting methods as described above, takes advantage of the advantages of both methods without compensating for their shortcomings, and minimizes the defrosting operation while maintaining the heating effect as much as possible. The purpose of this invention is to provide a defrosting method for an air conditioner that can effectively defrost the air.

<Structure of the Invention> In order to achieve the above object, the present invention adjusts the temperature of an outdoor heat exchanger during heating operation of an air conditioner configured to perform both reverse cycle defrosting and hot gas defrosting. The temperature difference with the outside air temperature is detected, and if the temperature difference is larger than a preset first reference value, hot gas defrosting is performed, and the second temperature difference is preset larger than the first reference value.
The feature is that reverse cycle defrosting is performed when the temperature is greater than a reference value.

<Example> The present invention will be specifically described below with reference to an illustrated example.

FIG. 1 shows a refrigeration cycle system diagram. 1 is a compressor, 2 is a four-way switching valve, 3 is an outdoor heat exchanger, 4 is a throttle mechanism, and 5 is an indoor heat exchanger, and these are connected in sequence to form a refrigeration cycle. Reference numeral 6 designates an injection capillary tube for cooling the compressor 1, 7 a bypass line provided in parallel to the outdoor heat exchanger 3, and 8 a solenoid valve for opening and closing the bypass line 7.

In this configuration, during heating operation, the compressor 1
The high-pressure, high-temperature refrigerant gas discharged from the refrigerant gas is sent to the indoor heat exchanger 5 via the four-way switching valve 2, where it is condensed and radiates heat, throttled by the throttle mechanism 4, and evaporated by the outdoor heat exchanger 3. It absorbs heat and returns to the compressor 1 via the four-way switching valve 2. For reverse cycle defrost,
The four-way switching valve 2 is switched as shown by the broken line in the figure, and the refrigerant gas discharged from the compressor 1 is sent to the outdoor exchanger 3 via the four-way switching valve 2, where it radiates heat and adheres to the outdoor heat exchanger 3. melt the frost. In addition, in the case of hot gas defrosting, the solenoid valve 8 is operated during normal heating operation to open the bypass line 7, and the high temperature gas is guided to the outdoor heat exchanger 3, thereby removing the frost that has adhered to the outdoor heat exchanger 3. Melt.

FIG. 2 is a wiring diagram of the control device, and the outdoor fan motor 3a of the outdoor heat exchanger 3, the indoor fan motor 5a of the indoor heat exchanger 5, the compressor 1, the four-way switching valve 2, and the solenoid valve 8 are relays. The AC power circuits 22 and 22' are connected in parallel to each other via contacts 17' to 21'. 10 is a thermistor for detecting the temperature of the outdoor heat exchanger 3 provided in the outdoor heat exchanger 3, 11 is a thermistor for detecting the outside air temperature, and the detected value of each thermistor 10, 11 is detected by the A/D converter 2.
4 to the microcomputer 12. The microcomputer 12 is, for example, a so-called one-chip microcomputer equipped with a program ROM, data RAM, accumulator, ALU, general registers, etc., and performs predetermined calculations according to the detected values of the thermistors 10 and 11 according to the program. The output signal of the calculation result is amplified by a driver array 13 composed of power transistors, etc., and drives the relays 17 to 21 to open and close each relay contact 17' to 21'. 14 is an external transmission circuit for the microcomputer 12, 15 is a power transformer, 16 is a rectifier circuit,
23, 23' are DC power supply circuits for the control section.

Next, the operation will be explained with reference to the control flowchart shown in FIG. Step S1 indicates normal heating operation, at which time relay contacts 17', 18', 1
9' and 20' are on, and 21' is off.
_T1 in step S2 indicates a preset fixed time, and a timer built into the microcomputer 12 continues the heating operation for the time _T1 . Next, the detection value Th ₂ of thermistor 10 and thermistor 1
The detected value Th ₁ of 1 is read in step S3, the difference between each detected value is compared in step S4, and when the temperature of the outdoor heat exchanger 3 decreases until Th ₁ - _{Th 2} > α, the process proceeds to step S5. Hot gas defrosting is then carried out. Here, α is the first reference value, and generally, when frost forms on the outdoor heat exchanger 3, the heat absorption effect deteriorates and the temperature of the outdoor heat exchanger 3 decreases, and the difference from the outside temperature is Th ₁ - _{Th 2} Since α is proportional to the amount of frost formation, α is preset to a certain predetermined value that serves as a reference for determining the necessity of hot gas defrosting. During hot gas defrosting, relay contacts 19', 20', 2
1' is on, 17' and 18' are off,
The solenoid valve 8 opens and the fan motor 3 of each heat exchanger
a and 5a are stopped. Th ₁ − at step S4
If Th ₂ > α, return to step S3,
The procedures of steps S3 and S4 are repeated at regular sampling intervals.

When hot gas defrosting is finished, steps S6 and S7
heating operation is resumed for a preset period of time.
The detection values Th _{1 and} Th ₂ of the thermistors 11 and 10 are read and compared in steps S8 and S9, and when the temperature of the outdoor heat exchanger 3 decreases until Th ₁ - Th ₂ > β. , step S10 is entered and reverse cycle defrosting is performed. β is a second reference value set in advance as a standard for determining that reverse cycle defrosting is necessary, and is set to a predetermined value such that β>α. During this reverse cycle defrosting, relay contact 19' is turned on, other contacts 17', 18', 20', and 21' are all turned off, and fan motor 3a,
5a is stopped, the four-way switching valve 2 is switched, and the refrigeration cycle is operated on the cooling side. When the reverse cycle defrosting is completed, the process returns to step S1 and the above-mentioned procedure is repeated again, and in step S9 Th ₁ - _{Th 2}
>β, the process returns to step S3 and the procedure from here is repeated.

Through the above procedure, when defrosting is necessary, either hot gas defrosting or reverse cycle defrosting is automatically selected.

<Effects of the invention> During heating operation, it is determined whether or not frost has formed based on the temperature difference, and if it is determined that there is frost and the amount of frost is relatively small, hot gas defrosting is performed. If the frost is no longer formed, the heating operation continues, and if it is determined from the temperature difference that the defrost has not been sufficiently defrosted even if the defrost is performed using the hot gas, the reverse cycle is started. Since defrosting is carried out by , it is possible to compensate for the disadvantages of both defrosting methods and take advantage of their advantages during heating operation.

In other words, if it is determined that relatively little frost has formed during heating operation, defrost is performed using hot gas, and the operation mode remains the heating cycle, and the operation mode is switched when returning to heating operation. It does not take much time, and the temperature of the indoor heat exchanger rises quickly, so the reduction in heating effectiveness can be minimized.

In addition, even if defrosting is performed using hot gas, if the above temperature difference is large and the amount of frost formed is relatively large, defrosting will be performed using the reverse cycle, so the operation mode will be switched to the reverse cycle and the defrosting will be performed. Can be done effectively.

In addition, when defrosting using hot gas is performed, the heating operation is temporarily resumed, and after checking the temperature difference again, it is necessary to decide whether to continue heating operation, or to perform defrosting using hot gas. By determining whether to perform defrosting using the reverse cycle, it is possible to suppress a decrease in the heating effect as much as possible, and to perform the heating operation effectively.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a refrigeration cycle according to the present invention,
FIG. 2 is a wiring diagram of a control device according to an embodiment of the present invention, and FIG. 3 is a control flowchart of the same. DESCRIPTION OF SYMBOLS 1... Compressor, 2... Four-way switching valve, 3... Outdoor heat exchanger, 4... Throttle mechanism, 5... Indoor heat exchanger, 7... Bypass line, 10, 11... Thermistor, 12... ...Microcomputer, α...
First reference value, β... second reference value.

Claims (1)

[Claims] 1 A compressor, a four-way switching valve, an outdoor heat exchanger, a throttling mechanism, an indoor heat exchanger, etc. are connected in sequence to constitute a refrigeration cycle that can be switched to cooling and heating, and the compressor and outdoor heat exchanger are In an air conditioner with a bypass line that can be opened and closed in between, the temperature difference between the outdoor heat exchanger temperature and the outside air temperature is detected.
If the temperature difference is in the region of the first set reference value α, the bypass line is opened to perform hot gas defrosting, and after that, the heating operation is performed for a preset interim time, and then the temperature of the external heat exchanger is adjusted again. When a temperature difference with the outside air temperature is detected and the temperature difference is in a region of a second set reference value β that is larger than the first set reference value α, the refrigeration cycle is switched to perform defrosting. A defrosting method for an air conditioner, characterized by: