JPS61101736A - Defrosting control device of air conditioner - Google Patents

Abstract

PURPOSE:To properly start the defrosting operation by detecting the differential temperature between the ambient temperature and the temperature of the outside heat exchanger and memorizing the value of said differential temperature at the time when there is no frosting so that the defrosting operation may be started when the corrected value reaches the reference value. CONSTITUTION:A differential temperature detecting circuit 17 detects the difference DELTAT between the ambient temperature and the temperature of the outside heat exchanger, and a hold circuit 18 retains the memory of the value tau of DELTAT under the normal operation. A correction circuit 19 detects the ratio between DELTAT and tau, i.e. DELTAT/tau, and a reference value setting circuit 20 sets a reference value alpha of the amount of correction as a function of the frosting amount at which a judgment is made that it will be the best in terms of efficiency if the heating operation is stopped and the defrosting operation is started. A judgment circuit 21 compares the correction amount DELTAT/tau with alpha, and outputs a defrosting starting signal when the reference value alpha is reached.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a defrosting control device for air conditioners that can be applied to defrosting control of small near conditioners (air conditioners), packaged air conditioners, air heat pumps, etc. It is something.

[Conventional technology]

Conventionally, this type of defrosting control device includes one that detects the temperature of the outdoor heat exchanger and performs defrost control in combination with a timer, and one that detects the temperature of the outdoor heat exchanger and performs defrost control in combination with a timer. A method is used that detects the difference and starts defrosting operation when the difference becomes larger than a predetermined value.

[Problem that the invention seeks to solve]

(1) A method that combines the outdoor heat exchanger temperature and a timer A method that starts defrosting operation when the temperature of the outdoor heat exchanger falls below the set value when the timer reaches the set time. This causes the following two problems.

(a) With air source heat pumps, frost does not form when the relative humidity is low even at low outside temperatures. However, the outdoor heat exchanger temperature may drop below the set value when the outside air temperature is low, and this method results in unnecessary defrosting operation. Since the heating operation is stopped during the defrosting operation, the room temperature decreases, causing discomfort, and unnecessary defrosting operation consumes energy, resulting in an inefficient operation.

(b) Even if frosting progresses rapidly and the temperature of the outdoor heat exchanger falls below the set temperature, the defrosting operation will not start if the timer has not reached the set time. As a result, the heating capacity decreases due to the heating mK, resulting in continued inefficient operation.

(2) A method that starts defrosting based on the temperature difference between the outside air temperature and the temperature of the outdoor heat exchanger.In this method, the difference between the outside air temperature and the temperature of the outdoor heat exchanger is larger than a predetermined value. When this happens, defrosting operation will start. In this case, the temperature difference that signals the start of defrosting (the difference between the outside air temperature and the temperature of one outdoor heat exchanger) cannot be removed unless it is changed depending on the size of the outdoor heat exchanger of the air conditioner, the air volume, etc. Cases occur where frost starts too early or, conversely, too late. For this reason, it is necessary to prepare models with different temperature difference settings for different models, which is uneconomical.The present invention was proposed to solve the above-mentioned conventional problems. A defrost control device for an air conditioner that eliminates the problem of starting defrosting operation when there is no frost on the outside heat exchanger, and also properly starts defrosting operation when frost accumulation occurs. The purpose is to provide the following.

[Means for solving problems]

The defrosting control device for an air conditioner according to the present invention includes a means for detecting a temperature difference ΔT between an outside air temperature and an evaporator temperature in an air conditioner including a compressor, a condenser, a throttle mechanism, an evaporator, etc. , the value τ of this temperature difference ΔT during steady operation
means for storing and storing the temperature difference ΔT, a means for detecting ΔT/τ by comparing the temperature difference ΔT that changes with time with the stored value τ, and a means for detecting ΔT/τ when the value of ΔT/τ exceeds a predetermined value. The apparatus is characterized by comprising means for outputting a defrosting operation start signal.

[Effect]

According to the present invention, the temperature difference ΔT between the outside air temperature and the evaporator temperature (outdoor heat exchanger temperature) when there is no frost accumulation on the outdoor heat exchanger at the initial stage of starting the operation of the air conditioner. Store the minimum value τ, then operate the air conditioner to detect the temperature difference ΔT between the outside air temperature and the outdoor heat exchanger when frost accumulates on the outdoor heat exchanger, and calculate these τ and ΔT. Compare and Δ
The defrosting operation is started when the relationship T/τ≧α (α is a predetermined value) is satisfied, thereby solving the above-mentioned conventional problems.

〔Example〕

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

FIG. 1 is a refrigeration cycle diagram showing the configuration of an embodiment of the present invention, and FIG. 2 is an electrical wiring diagram of the embodiment shown in FIG. 1. In FIG. 1 and FIG. 2, 1 is a compressor; 2 is a four-way switching valve, 3 is an outdoor heat exchanger, 4 is a capillary tube, 5 is an indoor heat exchanger, 6 is an indoor blower motor, 7 is an indoor blower, 8 is an outdoor blower motor, 9 is a A temperature sensing element of the outdoor heat exchanger, 10 is an outdoor temperature sensing element installed on the outdoor side, 11 is a control device for controlling the air conditioner, 12 is a power transformer for the control device, 13.14.15 is a temperature sensing element for the outdoor heat exchanger; The electromagnetic contactor 16 is an operating section for remote control.

FIG. 3 is a block diagram showing the configuration of a control unit that grasps the progress of frost formation and controls the start of defrosting operation in the embodiment shown in FIG. The outside air temperature TA and the temperature sensing element 9 of the outdoor heat exchanger
The temperature difference ΔT of the temperature Tc of the outdoor heat exchanger sensed by
(-TA-To); 18 is a hold circuit that detects and stores the minimum value τ of the temperature difference ΔT; 1;
9 is a correction circuit that compares and calculates the value of the temperature difference ΔT and the minimum value τ of the temperature difference that changes from time to time to detect the value Z; 2o is a reference value setting circuit; and 2 is the output of the correction circuit 19 and the reference value setting. circuit 2
A determination circuit 22 compares the output with the output of 0 and outputs a defrosting operation start signal when the correction value exceeds the reference value. 22 controls the operation of the hold circuit 18 and the correction circuit 19 depending on the operating status of the air conditioner. This is a control circuit that controls the

The operation of the embodiment of the present invention will be described. In FIGS. 1 to 3, when the heating operation is turned on by operating the remote control operation section 16, the electromagnetic contactors 13, 14. 15 is energized, each contact 13', 14'.

15' becomes "closed", the compressor 1, the four-way switching valve 2, and the outdoor ventilation motor 8 are energized, and the indoor ventilation motor 6 is also energized.
The high-pressure refrigerant passes through the four-way switching valve 2 and enters the indoor heat exchanger (condenser) 5, where it is condensed and liquefied. At this time, air is circulated by the indoor fan 7 and the indoor heat exchanger 5
Then, the refrigerant is depressurized in the capillary tube 4 and enters the outdoor heat exchanger (evaporator) 3, where it is evaporated and vaporized, and then sucked into the compressor 1 via the four-way switching valve 2. Ru.

In this case, if the heating operation continues, the outdoor heat exchanger 3 will have frost on its surface depending on the outside air conditions.

When the amount of frost accumulation exceeds a certain limit, the heating capacity decreases, and it is necessary to melt the frost before the heating capacity deteriorates further due to frost accumulation.To do this, it is necessary to accurately grasp the progress of frost formation. It is essential to do so.

FIG. 4 shows experimental results regarding the correlation between the process in which frosting progresses and the process in which the temperature difference (ΔT=I-TA-Tc) between the outside air and the outdoor heat exchanger increases.

In Fig. 4, the temperature difference ΔT goes through an unstable state (a) due to transient fluctuations in the refrigeration cycle immediately after the start of heating operation, and then reaches a stable state where it becomes almost constant when no frost formation occurs. Enter (b). When frosting progresses, ΔT
gradually increases from state ((b). Except for the transient unstable state (a) above, ΔT shows a minimum value in a stable state, but if the value at this time is τ, then the difference between ΔT and τ Ratio ≠
tends to increase monotonically as frost buildup increases.

The control section shown in FIG. 3 is a control section that accurately grasps frost formation and controls the start of defrosting operation based on the above experimental results, and its operation will be explained below.

In FIG. 3, a temperature difference detection circuit 17 is a circuit that detects the difference ΔT −TA −Ta between the outside air temperature TA and the outdoor heat exchanger temperature Tc, and a hold circuit 18 is a circuit that detects the difference ΔT during steady operation.
The correction circuit 19 is a circuit that stores and holds the value τ, and the correction circuit 19 is a correction circuit that detects the ratio of ΔT and τ, that is, ΔT/τ.The reference value setting circuit 20 is a circuit that stores and holds the value τ of In response, the heating operation can be stopped and the defrosting operation can be started.
The standard value of the above-mentioned correction amount (α ), the judgment circuit 2 compares the correction IΔT/τ with the above-mentioned base value α, and when it reaches the reference value, outputs a defrosting start signal, and the control circuit 22 controls the air conditioner. This circuit controls the operation of the hold circuit 18 and the integral circuit according to the operating state of the machine.It is a circuit that controls the operation of the hold circuit 18 and the integral circuit according to the operating status of the machine. The time set in anticipation, usually 5
(about 6 minutes), the hold circuit 18 is operated to stop the minimum value detection and memory retention functions, and the correction circuit 19 is operated to change the correction value to the initial value. This is a circuit that works to restore and maintain the state. The defrosting start signal from the control unit shown in FIG.
The four-way switching valve 2 is switched via the +4 magnetic contactor 15, the flow of the refrigerant is switched to the opposite direction, and the defrosting operation is started.

Note that the defrosting operation ends when the temperature Tc of the outdoor heat exchanger 3 becomes equal to or higher than the set value, and the heating operation returns.

〔Effect of the invention〕

As described above, according to the present invention, the temperature difference (ΔT-TA-Tc) between the outside air temperature and the outdoor heat exchanger is detected, and the value τ of the same temperature difference when no frost is formed is stored, and the air conditioner is operated. As the amount of frost increases, the temperature difference ΔT increases, and when the above correction value ΔT/τ reaches the reference value α, defrosting operation is started. It is something that can be effective.

(1) There is no problem with defrosting starting when there is no frost.

(2) Since the reference value α can be selected based on the relationship with the amount of frost formation, the defrosting operation can be started properly without starting the defrosting operation too early or too late. can.

(3) Conventional outside air temperature (TA) and outdoor heat exchanger temperature (
In the case where defrosting is started based on the temperature difference ΔT of Tc), the temperature difference ΔT at the start of defrosting had to be determined as an absolute value. However, the absolute value of the temperature difference ΔT at the start of defrosting usually varies depending on the size of the outdoor heat exchanger of the air conditioner, the air volume, etc. As shown on the right, the set value of the temperature difference ΔT differs for different models. However, according to the present invention, the difference between the outdoor heat exchanger and the outside heat exchanger at the initial stage of operation when there is no frost is detected during operation. The system detects the temperature τ (i.e., the minimum value of ΔT) and uses the phenomenon that the temperature difference ΔT monotonically increases as frost progresses to determine whether to start defrosting based on the correction value ΔT/τ. As a result, one type of defrosting device can be used for different types of air conditioners, which is an extremely economical advantage. At the same time, the necessary time for defrosting is not lost.

[Brief explanation of the drawing]

FIG. 1 is a refrigeration cycle diagram showing the configuration of an embodiment of the present invention, FIG. 2 is an electrical wiring diagram of the embodiment in FIG. 1, and FIG.
The figure is a block diagram showing the configuration of the control section of one embodiment in Fig. 1, and Fig. 4 is a diagram showing the experimental results regarding the temperature difference and the amount of frost formation.09...Temperature sensing of outdoor heat exchanger Element, 10...Outside temperature sensing element, 1...Control device, 16...Remote control operation unit, 17...Difference temperature detection circuit,
18... Hold circuit, 19... Correction circuit, 20.
...Reference value setting circuit, 2nd...Judgment circuit. Applicant Sub-Agent Patent Attorney Hiko Suzue Figure 1

Claims (1)

[Claims] In an air conditioner composed of a compressor, a condenser, a throttle mechanism, an evaporator, etc., there is a means for detecting a temperature difference ΔT between the outside air temperature and the evaporator temperature, and a value τ of this temperature difference ΔT during steady operation. The storage means compares the temperature difference ΔT that changes over time with the stored value τ, and calculates ΔT/τ.
A defrosting control device for an air conditioner, comprising: means for detecting ΔT/τ; and means for outputting a defrosting operation start signal when the value of ΔT/τ exceeds a predetermined value.