JPH0232541B2 - - 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, 7 is an indoor heat exchanger that serves as a condenser during heating, and includes a compressor 1, a four-way valve 2,
The outdoor heat exchanger 4, the capillary tube 5, and the indoor heat exchanger 7 are connected in a ring to form a well-known refrigeration cycle.

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 transferred to the outdoor heat exchanger. 4, the outdoor fan motor 3 absorbs heat from the outdoor air, 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 time is shown on the X-axis. 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 defrosting control operation. However, this control is not suitable for outdoor use because the defrosting operating temperature T _ON and the certain time t' that enables defrosting (hereinafter referred to as defrosting regulation release time) are fixed. Under conditions where the temperature is relatively high, the defrosting operation will not start until the above-mentioned defrost regulation release time t' has elapsed, and if the outside temperature is low, the above-mentioned defrost regulation release time t will not start even if no frost has formed. There was a problem that the defrosting operation started after the time period ' had elapsed.

In addition, since it is necessary to defrost reliably under any of the various load conditions mentioned above, the defrost operation temperature T _ON is set to a relatively high temperature, and the defrost regulation release time t' is set to a relatively high temperature. This has to be done in a relatively short period of time, and the defrosting operation often starts even when there is no actual frost formation, which results in more defrosting operations than necessary, resulting in inefficient heating operation. I was getting used to it.

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 first output means that outputs an output when heating operation is started, and a timer that measures the time when the first output means outputs an output. means, a setting means for sequentially setting a defrosting operating temperature higher in accordance with the timing of the timing means, and a temperature of the outdoor heat exchanger reaching a defrosting operating temperature set by the setting means or lower; a second output means for occasionally outputting a defrosting signal; and a release means for canceling the time measurement by the timer when the temperature of the outdoor heat exchanger reaches a 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 the conventional example, illustration and explanation will be omitted, 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 detected temperature T of the outdoor heat exchanger 4, and the X axis indicates the elapsed time t of the heating operation. In addition, the air conditioner is configured to include, for example, 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 1 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 drops rapidly, making it possible to detect the frost area A.

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 synchronization 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 passes, it becomes necessary to raise the set value of the defrosting operation temperature.

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 the vessel (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, so that when the room temperature reaches the set value without frost on the outdoor heat exchanger 4 and the operation of the compressor 1 is interrupted. Then 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, the first set time from the start of heating operation.
The heating operation is forcibly performed until t ₁ , and from the time when this first set time t ₁ has passed, if the detected temperature of the outdoor heat exchanger 4 is below the first set temperature T ₁ , defrosting is performed. enter. Further, after the second set time _t2 , the value of the defrosting operation temperature rises to the second set temperature _T2 , and furthermore, after the third set time _t3 , the defrosting operation temperature rises to the third set temperature T2. Similarly, after the fourth setting time _t4 has passed, the defrosting operation temperature is set to the fourth temperature _T3 .
The set temperature of T ₄ and rises.

When the defrosting operation conditions are met, the four-way valve 2,
The indoor and outdoor fans 3 and 6 are each turned off, enter the cooling cycle, and defrost. 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, the relationship between the first to fourth set times t ₁ to t ₄ and the first to fourth set temperatures T ₁ to T ₄ is
Optimum defrosting characteristics can be obtained by setting in a proportional relationship as shown in the figure.

Next, after the first defrosting is completed, the first to fourth set times t ₁ to t ₄ start from the time when heating operation is started again.
starts counting, but 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 when the timer cancel temperature T _O is exceeded. t _c is this timer cancellation period.

Furthermore, from the time heating operation is started by turning on the thermostat 14, etc., the set time t ₁ to _{t 4} is set again.
Start counting.

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, after a relatively low rotation speed continues, the thermostat 14
If the rotation speed increases due to a setting change, the equilibrium point of the refrigeration cycle may shift, causing the ice to enter day ice even though no frost has formed. However, if this timer cancel function is used, In practical terms, the chances of "empty day ice" can be dramatically reduced.

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 .
Reference numeral 23 denotes a reference voltage generation unit that determines voltage levels according to the room temperature set temperature T _OFF , timer cancel temperature T ₀ , and first to fourth set temperatures T ₁ to T ₄ , and corresponds to the setting means of the present invention. In addition to determining the voltage levels of the room temperature set temperature T _OFF and the timer cancellation temperature T ₀ , the proportional relationship between the first to fourth temperatures T ₁ to _{T 4} and the first to fourth set times t ₁ to t ₄ is determined. Change settings gradually. 24
As is well known, the first to fourth set times are internally set.
A P-channel microcomputer equipped with a timer function for setting _t1 to _t4 , 25 is a defrosting signal output section that receives a signal from the output port _O5 of the microcomputer 24, and is a second output section of the present invention. corresponds to the switching transistor 25a,
It is composed of 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 includes, in addition to the timekeeping means and the release means of the present invention, a first output means (output port O ₆ ) that outputs an operation control signal for the heating operation equipment 26 such as a compressor and a blower, and the above-mentioned settings. It also has an arithmetic function and an instruction function for controlling the first and second output means.

Then, the output of the microcomputer 24 is O ₀
~O ₄ is output in time division, and all outputs O ₀ ~ O ₄ are
When it is OFF, the voltage level corresponds to the room temperature set temperature T _OFF in Fig. 5, and the following outputs are sequentially output as O ₀ to O ₄ , and the timer cancel temperature T ₀ and defrosting operation temperature are the first to fourth set temperatures, respectively. Generate voltage levels corresponding to _T1 to _T4 . 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 operating 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.

In other words, when conventional defrosting control is applied to an air conditioner with variable capacity, the chances of so-called "empty day ice", which is even less efficient than in air conditioners without variable capacity, increase; however, the defrosting control of the present invention According to the control device, the defrosting characteristics can be made to almost match the frosting characteristics of the air conditioner with variable capacity, and the timer itself can be canceled when it is not needed.
Defrosting operation is not performed unless frost is actually forming, and the frequency of defrosting in practical use can be greatly reduced.

In addition, even in air conditioners whose capacity is not variable,
Similar effects can be obtained even if the defrosting operation temperature is set to gradually rise in proportion to the operating time from the start of the heating operation, as shown in FIG. 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 when the outside temperature is relatively high, Since the defrosting ability is relatively high, the defrosting operation can be started after sufficient frost formation, 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, the timer count is canceled if there is no frost formation, making it possible to further reduce the frequency of defrosting and increase heating efficiency. becomes.

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. This has the advantage of not having to go into defrosting operation in a short period of time when the system is restarted.

[Brief explanation of drawings]

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 a main part electric circuit diagram of a defrosting control device for an air conditioner showing one embodiment of the present invention. DESCRIPTION OF SYMBOLS 1...Compressor, 2...Four-way valve, 4...Outdoor heat exchanger, 5...Capillary tube, 7...Indoor heat exchanger, 21...Thermistor, 23...Reference voltage generator ( (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 for detecting the temperature of a timing means for timing the output of the output means; a setting means for sequentially setting a defrosting operation temperature higher in accordance with the timing of the output means; and a setting means for setting the temperature of the outdoor heat exchanger by the setting means. a second output means for outputting a defrosting signal when the temperature of the outdoor heat exchanger reaches a timer cancel temperature or higher while the compressor is stopped; A defrosting control device for an air conditioner comprising a release means for canceling time measurement by a time measurement means.