JPS6334376B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a defrosting control device for a heat pump type air conditioner, the operation control device of which is equipped with a microcomputer.

Conventional configuration and its problems Conventional defrosting control during heating with a heat pump air conditioner measures the temperature of the outdoor heat exchanger and, after a certain period of time, defrosts if the temperature is below a certain level. Ta.

This conventional example will be explained using FIGS. 1 to 3.

FIG. 1 is a refrigeration cycle diagram during heating.

In Fig. 1, 1 is a compressor, 2 is a four-way valve, 3 is an outdoor fan motor, 4 is an outdoor heat exchanger that serves as an evaporator during heating, 5 is a capillary tube as a pressure reducer, 6 is an indoor fan motor, and 7 is an indoor heat exchanger that serves as a condenser during heating, and is connected in a ring with a compressor 1, a four-way valve 2, an outdoor heat exchanger 4, a capillary tube 5, and an indoor heat exchanger 7 to form a well-known refrigeration cycle. It consists of

During heating, the refrigerant compressed by the compressor 1 enters the indoor heat exchanger 7, radiates heat indoors by the indoor fan motor 6, is depressurized via the capillary tube 5, and is then heat exchanged outdoors. The air enters the compressor 4, absorbs heat from the outdoor air by the outdoor fan motor 3, passes through the four-way valve 2, and returns to the compressor 1. Further, during defrosting, the indoor and outdoor fan motors 3 and 6 are stopped, the four-way valve 2 is switched to establish a cooling cycle, and the frost that has formed on the outdoor heat exchanger 4 is melted.

FIG. 2 is an electrical circuit diagram that realizes the operation of the refrigeration cycle shown in FIG. 1. Here, the same parts as in FIG. 1 are given the same numbers and the explanation will be omitted.

In Fig. 2, 11 is a control circuit, 12 is a defrosting output contact that is controlled ON and OFF by the control circuit 11, 13 is a heating switch (a switch that turns OFF during cooling), and 14 is a thermostat. is ON when the setting value is exceeded during cooling.
Also, during heating, the ON operation is performed below the set value. 15
is the driving switch.

When frost forms on the outdoor heat exchanger 4, the defrosting output contact 12 is opened, the four-way valve 2, the outdoor fan motor 3, and the indoor fan motor 6 are de-energized and defrosting operation begins.

FIG. 3 is a time chart explaining the conventional defrosting operation.

In FIG. 3, the detected temperature from the outdoor heat exchanger 4 is shown on the Y-axis, and the X-axis shows time. Then, when the heating operation is started, the detected temperature of the outdoor heat exchanger 4 gradually decreases.

After a certain period of time t' has elapsed from the start of heating, when the detected temperature falls below the defrosting operation temperature T _ON , the defrosting operation described above is started, the four-way valve 2 is switched, and the outdoor fan motor 3 and indoor fan motor 6 are turned off. Let it be an action. As a result, when the frost melts and reaches the defrost stop temperature T _OFF or higher, the defrost control is ended and normal heating operation is resumed.

The above is the conventional defrost control operation, but in this control, the defrost operating temperature T _ON and the fixed time t' that enables defrosting (hereinafter referred to as the defrost control release time) are fixed, so the outdoor temperature Under conditions where the temperature is relatively high, it is difficult to start the defrosting operation even if frost forms until the above-mentioned defrost restriction release time t' has elapsed, and if the outside temperature is low, the above-mentioned defrosting operation will not start even if there is no frost. There was a problem in that the defrosting operation started after the frost restriction release time t' had elapsed.

In addition, since it is necessary to defrost reliably under any of the various load conditions mentioned above, the defrosting operation temperature T _ON is set to a relatively high temperature, and the defrosting regulation release time t' is set at a relatively high temperature. I had no choice but to make it a short time,
Defrosting operations often begin even when frost has not actually formed, which results in more defrosting operations than necessary.
This resulted in inefficient heating operation.

Furthermore, recently, it has become known to perform variable capacity control of an air conditioner using a power saving mechanism of a refrigeration cycle, or compressor rotational speed control such as inverter control or pole number conversion control. However, with these controls, the equilibrium point of the refrigeration cycle changes depending on the capacity, and the rate of progress of frost formation differs, so when conventional defrosting control is used, heating efficiency deteriorates.

Purpose of the invention The present invention solves the above-mentioned conventional problems.
The aim is to dramatically improve heating efficiency.

Composition of the Invention In order to achieve this object, the present invention provides a control circuit for an air conditioner including a comparison means that outputs an output when the temperature of the outdoor heat exchanger is equal to or lower than the timer cancel temperature, and a timer that measures time when the comparison means outputs an output. a setting means for sequentially setting a defrosting operating temperature to a higher value in accordance with the timing of the timing means; an output means for outputting a defrosting signal when the temperature reaches the timer cancel temperature, and a release means for canceling the time measurement by the timer when the temperature of the outdoor heat exchanger reaches the timer cancel temperature or higher while the compressor is stopped. It is composed of

With this configuration, defrosting operation can be performed reliably only when frost has formed on the outdoor heat exchanger.
This will improve heating efficiency.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 4 to 6 of the accompanying drawings. Here, since the structure of the refrigeration cycle is the same as that of the conventional example, illustrations and explanations will be omitted again, and the control contents related to defrosting will be explained here.

Changes in frost formation conditions due to outside temperature have already been described, so a description thereof will be omitted, and here, first, frost formation conditions due to heating capacity will be explained using FIG. 4.
In FIG. 4, the Y axis indicates the temperature T of the outdoor heat exchanger,
Moreover, the X-axis shows the elapsed time t of the heating operation.
Further, as an example, the air conditioner is configured to include a compressor whose rotation speed is variable using an inverter to change its capacity.

As for the operating conditions of the air conditioner, for example, the synchronous frequency of the compressor is varied from 45 Hz to 90 Hz, and the same air conditioning load is applied.

When the amount of frost builds up exceeds a certain level, the amount of ventilation in the outdoor heat exchanger 4 decreases rapidly, so both the high and low pressures of the refrigeration cycle decrease rapidly, causing
The detected temperature also decreases rapidly, and the frost area A can be detected.

On the other hand, when the synchronous frequency of the compressor 1 is around 45 Hz, the capacity is relatively low, so the equilibrium temperature is somewhat high and the progress of frost formation is slow. Further, when the synchronous frequency is 90 Hz, the capacity is large, so the equilibrium temperature is low and the rate of frost formation is fast, so that the relationship shown in FIG. 4 is established.

Therefore, as time t elapses, it becomes necessary to raise the defrosting operation setting value.

Furthermore, during seasons when the heating load is light, such as in spring and autumn, the thermostat 14 opens and closes frequently. When the room temperature reaches the set value and the thermostat 14 is OFF, if there is no frost on the outdoor heat exchanger (evaporator) 4, the high and low pressures of the refrigeration cycle balance the pressure, so the outdoor heat exchanger The temperature of (evaporator) 4 reaches at least 0 degrees or higher.

If the defrosting restriction release time t' by the operation timer has already elapsed as in the conventional case, the next time the heating operation is restarted by a command from the thermostat 14, the temporary drop in high and low pressure will cause the detection The temperature may drop and defrost operation may be started.

Therefore, a timer cancel temperature higher than the defrosting operation temperature is set in the temperature to be detected, and if the room temperature reaches the set value without frost formation in the outdoor heat exchanger 4 and the operation of the compressor 1 is interrupted, It becomes necessary to cancel the operation timer.

Next, referring to FIG. 5, a description will be given of defrosting control when the operating temperature and time setting are set in four stages, which is an example of the present invention.

First, after starting heating operation, timer cancel temperature
Heating operation is forcibly performed from the time when T _O falls below T O until the first set time, and from the time when this first set time t ₁ has passed, the detected temperature of the outdoor heat exchanger 4 reaches the first set time. If the set temperature is below T ₁ , defrosting will begin. Furthermore, after the second set time _t2 , the value of the defrosting operating temperature rises to the second set temperature _T2 , and furthermore, after the third set time _t3 , the defrosting operating temperature rises to the third set temperature T2. The set temperature T ₃ is set, and the fourth set time t ₄ is also set.
The defrosting operation temperature is set to the fourth set temperature after
T ₄ and rise.

When the defrosting operation conditions are met, the four-way valve 2 and indoor fans 3 and 6 are turned off,
The air conditioner enters the cooling cycle and defrosts the air. As a result, when the temperature of the outdoor heat exchanger 4 becomes equal to or higher than the return set value T _OFF , defrosting ends and heating operation returns.

Therefore, by setting the relationship between the first to fourth set times _t2 to _t4 and the first to fourth set temperatures _T1 to _T4 in a proportional relationship as shown in FIG. , optimum defrosting characteristics can be obtained.

Next, after the first defrosting is completed, the heating operation is started again, and the first to fourth counts are started from the time when the temperature of the outdoor heat exchanger 4 falls below the timer cancel temperature _TO . , thermostat 14
When the compressor 1 is stopped due to turning off or the like, the temperature of the outdoor heat exchanger 4 starts to rise. As a result, the timer count is canceled at the point where the timer cancel temperature T _O is exceeded.

Furthermore, heating operation is started by turning on the thermostat 14, etc., and counting of set times _{t1 to t4 is} started again from the time the timer cancel temperature T0 falls below.

This timer cancel function can prevent day ice operation due to a temporary drop in high and low pressure. In addition, in an air conditioner that uses an inverter or the like to control the rotation speed of the compressor 1, if the rotation speed increases due to a change in the thermostat setting after a series of relatively low rotation speeds, the equilibrium point of the refrigeration cycle may change. Due to movement, there may be cases where day ice is entered even though there is no frost, but if this timer cancel function is used, the chances of "empty day ice" can be dramatically reduced in practice.

In addition, the timer start condition is such that counting starts from the time when the compressor 1 is in ON operation and falls below the timer cancel temperature _TO . This occurs when the outside temperature is low and the compressor 1 stops, for example, when the thermostat 14 is set to a low temperature setting, or when another heater is used indoors. etc., but the timer count is not started under such conditions.

This is also effective in reducing "empty day ice".

Next, the configuration of the electric circuit that performs the above operation will be explained with reference to FIG.

In the figure, 21 is a thermistor that detects the temperature of the outdoor heat exchanger 4, and corresponds to the temperature detector of the present invention. 22 is the detection temperature of the thermistor 21, the room temperature set temperature T _OFF , and the timer cancel temperature T ₀
and the first to fourth set temperatures which are the defrosting operating temperatures.
This is a comparator that detects temperature levels from _T1 to _T4 , and corresponds to the comparison means of the present invention. 23 are the room temperature set temperature T _OFF , the timer cancel temperature T ₀ , and the first to fourth
A reference voltage generation unit that determines the voltage level according to the set temperature _T1 to _T4 , which corresponds to the setting means of the present invention,
The room temperature setting temperature T _OFF , timer cancel temperature
In addition to determining the voltage level of T ₀ , the first to fourth temperatures
The proportional relationship between T ₁ to T ₄ and the first to fourth set times t ₁ to _{t 4} is gradually switched and set. 24 is a P-channel microcomputer internally equipped with a timer function for setting the first to fourth set times _t1 to _t4 as is well known; 25 is a defrosting signal output section of the microcomputer 24; Corresponds to the output means of the present invention,
It is composed of a switching transistor 25a, a relay coil 25b, and a relay contact 25c. The relay contact 25c controls energization to an electromagnetic coil (not shown) that drives the four-way valve 2. Further, the microcomputer 24 is equipped with an arithmetic function and an instruction function for controlling the setting means and output means, in addition to the timekeeping means and canceling means of the present invention.

Then, the output of the microcomputer 24 is 0O
~04 is output in time division and all outputs are 00~04.
When it is OFF, the voltage level corresponds to the room temperature set temperature T _OFF in Figure 5, and the following values are sequentially output as 00 to 04, and the timer cancel temperature T ₀ and the defrosting operation temperature become the first to fourth set temperatures T ₁ , respectively. Generates a voltage level corresponding to ~T ₄ . By comparing this voltage with the voltage from the thermistor 21 using a comparator 22, the frosting state of the outdoor heat exchanger 4 is detected.

By combining and calculating this temperature and the first to fourth set times _t1 to _t4 of the timer counted by the software of the microcomputer 24, the defrosting characteristics shown in FIG. 5 are synthesized. Once the frost conditions are established, the defrost signal is output to the defrost signal output section 25,
A defrosting operation is performed, and when the temperature of the outdoor heat exchanger reaches the timer cancel temperature T ₀ while the compressor is stopped, the timer operation of the microcomputer 24 is canceled.

Therefore, efficient defrosting can be performed with an extremely simple circuit configuration without using complicated means such as detecting the outside temperature or the capacity level of the compressor.

The effect of this defrosting control is particularly remarkable in air conditioners equipped with variable capacity compressors, and a great effect is expected.

That is, when conventional defrosting control is applied to an air conditioner with variable capacity, the chances of so-called "empty die ice" which is even less efficient than in non-variable capacity air conditioners increases; however, the defrosting control of the present invention The control device allows the defrosting characteristics to almost match the frosting characteristics of an air conditioner with variable capacity, and the timer itself can be canceled when it is not needed, so it can be used only when frost is not actually forming. No defrosting operation is performed, and the practical frequency of defrosting can be greatly reduced.

In addition, even in air conditioners whose capacity is not variable,
As shown in FIG. 5, the same effect can be obtained even if the defrosting operation is set to gradually increase in proportion to the operating time from the start of the heating operation. In other words, even when the outside temperature is low and the equilibrium temperature of the outdoor heat exchanger 4 is low, the operating temperature is lower than the conventional defrosting conditions, so the frequency of defrosting can be lowered, and even when the outside temperature is relatively high, Since the defrosting ability is relatively high, the defrosting operation can be started after sufficient frost has formed, and the defrosting frequency can also be lowered in this case. Furthermore, under air conditioning conditions where the room temperature reaches the set value and the thermostat 14 is turned off, if there is no frost formation, the timer count is canceled, making it possible to further reduce the frequency of defrosting and improve heating efficiency. becomes possible.

In addition, in this embodiment, capacity control is not limited to inverter control, and can be similarly performed in air conditioners using other controls such as bypass control, and air conditioners that are not equipped with capacity control. .

Effects of the Invention As described above, the defrosting control device of the present invention increases the defrosting operation temperature value in proportion to the elapse of time from the start of heating operation, so that when the first set time elapses and the outside temperature decreases. Even if the outdoor heat exchanger is not frosted, the heating operation will continue as long as frost does not form on the outdoor heat exchanger. heating efficiency can be dramatically increased compared to conventional configurations.
Furthermore, ideal defrosting control can be performed with a simple circuit configuration, and the compressor is stopped by room temperature control, and the defrost temperature setting time is canceled if there is no frost on the outdoor heat exchanger. , the defrosting operation does not start in a short time when restarting, and the defrosting temperature setting time starts again when the temperature of the outdoor heat exchanger reaches a temperature where frost is likely to form (timer cancel temperature). This has the effect of ensuring reliable defrosting operation.

[Brief explanation of the drawing]

Figure 1 is a diagram of a heat pump refrigeration cycle that performs heating and defrosting operations, Figure 2 is an electrical circuit diagram of a conventional air conditioner defrost control device, and Figure 3 is a diagram of the conventional defrost control operation of the same device. 4 is a time chart showing the frosting state of the heat exchanger of an air conditioner. FIG. 5 is a time chart showing the defrosting control operation in an embodiment of the present invention. FIG. 6 is a time chart showing the defrosting control operation in an embodiment of the present invention. 1 is an electrical circuit diagram of a main part of a defrosting control device for an air conditioner showing one embodiment of the present invention. 1... Compressor, 2... Four-way valve, 4... Outdoor heat exchanger, 5... Capillary tube, 7... Indoor heat exchanger, 21... Thermistor, 23... Reference voltage generation section ( switching setting means), 24...microcomputer (control circuit), _t1 to _t4 ...setting time,
T ₁ to T ₄ ...Set temperature.

Claims (1)

[Claims] 1 A compressor, a four-way valve for switching between a heating cycle and a defrosting cycle, an outdoor heat exchanger, a pressure reducer, and an indoor heat exchanger are connected in a ring to form a heat pump refrigeration cycle, and the outdoor heat exchanger A temperature detector that detects the temperature of the outdoor heat exchanger and a control circuit that inputs a signal from the temperature detector are provided, and the control circuit outputs the signal when the temperature of the outdoor heat exchanger is equal to or lower than the timer cancel temperature. means for timing the output of the comparison means; setting means for setting the defrosting operation temperature to higher values in accordance with the timing of the timekeeping means; output means for outputting a defrost signal when the defrost operating temperature reaches a preset defrost operating temperature;
A defrosting control device for an air conditioner, comprising a release means for canceling the time measurement by the time measurement means when the temperature of the outdoor heat exchanger reaches the timer cancel temperature or more while the compressor is stopped.