JPH0566497B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a defrosting control device for a separate heat pump type air conditioner. Regarding air conditioners.

Prior Art Conventionally, as shown in Japanese Patent Publication No. 59-34255, the state of frost on an outdoor heat exchanger is detected based on both the temperature change of the indoor heat exchanger and the indoor temperature change. Technologies have been developed to control heating and defrosting operations.

Problems to be Solved by the Invention However, such a conventional configuration requires a plurality of temperature detection elements, and has the problem of complicating the circuit itself. Furthermore, in air conditioners, the amount of air blown inside the room is usually variably set arbitrarily, and for this reason, adding an air amount correction means to the conventional technology would further complicate the circuit. . Moreover, since this configuration detects the temperature of the gas-liquid mixed refrigerant flowing through the heat exchanger, the temperature change between frost and non-frost is small, and frost formation must be determined within a minute range. However, there is a problem that the detection accuracy is unstable.

In addition, in recent years, control devices are often configured by using microcomputers to perform complex signal processing, but the fact that there are many input signal sources (temperature detection elements) as in conventional technology makes it difficult to create programs. This is a source of negative effects, and there are limits to the simplification of programs.

As described above, the conventional technology has many problems, and improvements are required.

In view of the above-mentioned conventional problems, the present invention provides a defrosting control device that can be simplified in configuration without sacrificing the advantages of the prior art.

Means for Solving the Problems In order to solve the above problems, the present invention, as shown in FIG. A time measuring means for measuring a time, a set time storing means for storing a preset time, and a second time measuring means for detecting and outputting a match between the time detected by the time measuring means and the time set in the set time storing means. 1, a temperature detection means for detecting the temperature of a pipe connected to the refrigerant inlet side of the indoor heat exchanger, and a set temperature storage means for storing a boundary value temperature for switching a heating cycle to a defrosting cycle. , second comparison means for detecting and outputting that the temperature detected by the temperature detection means has fallen below the boundary value temperature stored in the set temperature storage means; a current detection means for detecting a power supply current; and a heating cycle. a set current storage means storing a boundary value current for switching to a defrosting cycle; and detecting that the current detected by the current detection means has decreased from the boundary value current stored in the set current storage means;
a third comparing means to output, and a comparison between a set time elapsed signal by the first comparing means and a boundary value decrease signal by the second comparing means or a set time elapsed signal from the first comparing means and the third comparison means; The apparatus is comprised of a determination means for determining switching from a heating cycle to a defrosting cycle based on a boundary value decrease signal from the means, and a selection output means for controlling the refrigeration cycle from heating operation to defrosting operation in accordance with the output of the determination means. This is what I did.

Effect: With this configuration, the heating operation is ensured until a predetermined time has elapsed from the start of the heating operation, and after the elapse of the predetermined time, the defrosting operation is controlled by the temperature detected by the temperature detection means or the current detected by the current detection means. Ru.

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 2 to 6. FIG. 2 is a refrigeration cycle diagram showing one embodiment of the present invention. In the figure, the refrigeration cycle is constructed by sequentially connecting a compressor 1, a four-way switching valve 2, an indoor heat exchanger 3, a pressure reducer 4, and an outdoor heat exchanger 5. Reference numeral 6 denotes a pipe temperature detection element, which is attached to a pipe that is on the refrigerant inlet side of the indoor heat exchanger 3 (condenser) during heating. In this case, during cooling operation, the refrigerant flows in the direction of the solid line arrow in the figure, and during heating operation, the four-way switching valve 2 is switched so that the refrigerant flows in the direction of the broken line arrow in the figure.

Further, the compressor 1, the four-way switching valve 2, the pressure reducer 4, the outdoor heat exchanger 5, and the outdoor blower 8 constitute an outdoor unit A. In addition, a microcomputer (hereinafter abbreviated as microcomputer) is programmed with the indoor heat exchanger 3 and the indoor blower 7, a pipe temperature detection element 6, a current detection element 9 that detects the power supply current, a timer function, a temperature control function, etc. ) is provided in indoor unit B (not shown). Here, the pipe temperature detection element 6 is attached at a location away from the wind circuit where it is not affected by the air blowing from the indoor blower 7. Alternatively, the location may be near indoor unit B.

FIG. 3 is a main circuit diagram of the operation control section. In the same figure, a storage unit 1 that stores a time count value for determining operating time is included in a microcomputer 11.
2. It has a drive signal generating means 13 which generates an appropriate output signal by comparing the time count value stored in the storage section 12 with the input value. On the input side of this microcomputer 11, via a comparator 14, a piping temperature detection element 6 (for example, a piping thermistor or thermocouple element, etc.) serving as a temperature detection means, and a temperature setting resistor 15 whose resistance value can be changed as necessary.
16, 17, a current detection element 9 (for example, a current transformer) which is a current detection means via a comparator 18, a current-voltage conversion circuit 21 which converts a current value into a voltage value, and the resistance value can be changed as necessary. Current setting resistors 19 and 20 are connected. Furthermore, on the output side, there are a relay R ₁ that drives a four-way switching valve coil, which is a driving means, via the switch transistors TR ₁ to _{TR 4} , a relay R ₂ that drives the indoor blower 7,
A relay R ₃ that drives the outdoor blower 8 and a relay R ₄ that drives the compressor 1 are connected.

Here, when comparing the configuration of FIG. 3 with the configuration of FIG. 1, the piping temperature detection element 6 and the resistor 15 are
The comparator 14 corresponds to the second comparison means in FIG. 1, and the resistors 16, 1
The voltage generated by 7 and the pipe temperature detection element 6 corresponds to the signal of the set temperature storage means in FIG. 1, and the current detection element 9 and the current-voltage conversion circuit 21 correspond to the current detection means in FIG. Comparator 18 is the first
The voltage generated by the resistors 19 and 20 corresponds to the signal of the set current storage means shown in FIG.
corresponds to the set time storage means, time measurement means, first comparison means, determination means, and selection output means in FIG. 1, and among them, the drive signal generation means 13 corresponds to the determination means and selection output means.

Next, the operation from the start of heating operation to defrosting operation will be explained.

The discharge refrigerant temperature of compressor 1 is Td, the suction refrigerant temperature of compressor 1 is Ts, the discharge pressure of compressor 1 is Pd, the suction pressure of compressor 1 is Ps, and the polytropic index is n (where 1<n<K In the relationship, K is the adiabatic compression index), then the discharge refrigerant temperature Td is expressed by the following equation. (However, heat loss due to piping) Td=Ts・(Pd/Ps)n-1/n Therefore, when the outdoor heat exchanger 5 is not frosted, the suction refrigerant temperature Ts is high, and the discharge refrigerant temperature Td is also high. expensive. As the outside air drops and frost grows, the suction refrigerant temperature Ts decreases and the discharge refrigerant temperature Td
It also goes down. Piping temperature detection element 6 in the present invention
is installed in the inlet pipe of the indoor heat exchanger 3, and detects the temperature of the part through which the high-temperature, high-pressure superheated refrigerant gas discharged from the compressor 1 flows, but the temperature is actually lower than that of the discharged gas. This is the temperature that has decreased by a predetermined temperature due to heat loss in piping, etc. Therefore, as shown in FIG. 4, when the outdoor heat exchanger 5 is not frosted, both the suction refrigerant temperature Ts of the compressor 1 and the inlet piping temperature t of the indoor heat exchanger 3 are high; As the temperature progresses, the temperature t of the inlet pipe of the indoor heat exchanger 3 gradually decreases, and when frost formation occurs which significantly reduces the heating capacity, the temperature t of the inlet pipe of the indoor heat exchanger 3 decreases extremely. Further, the power supply current of the air conditioner generally has a value that proportionally follows the discharge refrigerant temperature Td, and as shown in FIG. 4, has a value that approximately follows the temperature detected by the pipe temperature detection element 6.

However, when the amount of refrigerant in the refrigeration cycle of an air conditioner decreases, the current value tends to be relatively low. That is, if the inlet pipe temperature t becomes less than the set pipe temperature t ₁ or the current value I becomes less than the set current I ₁ , the heating capacity decreases, and since frost formation has progressed, it is necessary to defrost. in this way,
Since the inlet pipe temperature t of the indoor heat exchanger 3 is the temperature of the refrigerant gas in the superheated region, it is not easily affected by the air volume of the indoor blower 7, and is determined by the inlet pipe temperature of the indoor heat exchanger 3 or the current value. Appropriate defrosting operation decisions can be made.

Next, the behavior when the amount of refrigerant in the refrigeration cycle is insufficient or when it gradually leaks due to long-term use will be explained using FIG. 6.

Based on the above explanation, the control circuit shown in FIG. 3 controls the contents of the flowchart shown in FIG. 5.

When the amount of refrigerant is insufficient compared to the steady amount of refrigerant,
As is well known, the amount of refrigerant circulated within the refrigeration cycle decreases, the temperature of the refrigerant discharged from the compressor rises, and the temperature of the refrigerant sucked rises as well. On the other hand, naturally, the pressure in the refrigeration cycle decreases, and the refrigerant temperature in the evaporator also decreases as the pressure decreases, and due to heat exchange with the outside air, frost formation occurs during heating operation compared to when operating with a steady amount of refrigerant. We will move on. On the other hand, the operating current decreases compared to steady operation because the amount of refrigerant circulation decreases, the high pressure decreases, the pressure difference between the high pressure and the low pressure becomes smaller, and the amount of work of the compressor decreases.

Therefore, the suction refrigerant temperature Ts of the compressor 1, the inlet pipe temperature t of the indoor heat exchanger, and the power supply current value I are
Compared to the state shown in the figure, there is an upward trend, an upward trend, and a downward trend, respectively.

Therefore, if the defrosting start determination condition is only the value of the inlet pipe temperature t of the indoor heat exchanger, if the amount of refrigerant is insufficient, the defrosting operation will not start even if frosting progresses.

By appropriately setting the determination point I ₁ of the power supply current value I, an appropriate defrosting operation can be performed even in such a case.

That is, when the heating operation is started as shown in step 1 in FIG. 5, a timer count for a predetermined time T is set in the microcomputer 11 (step 2). This timer count set is for ensuring heating operation for T hours (for example, 1 hour) from the start of heating operation. For example, one means is to forcibly continue heating for T hours.

After the timer count is set, in step 3 it is determined whether time T has elapsed. Heating operation continues until T time elapses.

Then, when time T has elapsed, the process moves to step 4.
The pipe temperature t is read by the pipe temperature detection element 6, and the process moves to step 5, where it is determined whether the pipe temperature t is lower than the set pipe temperature _t1 . Specifically, the comparator 14 in FIG. 3 makes the determination.

If the pipe temperature t is higher than the set temperature _t1 in step 5, the process moves to step 6, where it is determined whether the current value I is lower than the set current value _I1 .
Specifically, the comparator 18 shown in FIG. 3 makes the determination.

When the conditions of step 5 or step 7 are satisfied, the process moves to step 8 and defrosting operation is started. That is, the transistor TR ₁ in FIG.
TR ₂ , TR ₃ , and TR ₄ each operate to switch the four-way switching valve 2, and if necessary, before that, the compressor 1 is stopped for a certain period of time, and the indoor blower 7 and outdoor blower 8 are switched on.
stop. Defrost is then performed in the cooling cycle. Since the content of this defrosting operation is conventionally well known, detailed explanation will be omitted. Further, the restoration of the heating operation can be carried out by any suitable means as is well known in the art.

In this embodiment, the defrosting operation is performed by switching from the heating cycle to the cooling cycle. It goes without saying that a configuration in which the frost is allowed to flow or a configuration in which a separate heat source is used to melt the frost may also be used. Further, the compressor 1 may be operated continuously when switching to defrosting operation, and may be temporarily stopped before returning to heating operation.

Effects of the Invention As described above, according to the present invention, the temperature of the refrigerant gas in the superheated region is detected at the indoor heat exchanger inlet piping, and the power supply current is detected by the above-described configuration.
Accurate defrosting operation can be performed with one temperature detection point or one current detection point without being affected by the indoor air volume, the configuration is very simple, and the refrigerant has a sufficient amount of heat for heating. Since it can be determined on the inlet side of the indoor heat exchanger whether the heating capacity is present or not, defrosting can be performed by reliably determining the presence or absence of the actual heating capacity. In addition, if the refrigerant cycle is short of refrigerant, the current can be used to perform appropriate defrosting.
In other words, in the present invention, there is no difference in the temperature of the refrigerant at the inlet part and the middle part of the heat exchanger when frost has completely formed, and when no frost has formed, the inlet refrigerant temperature is higher than the refrigerant temperature in the middle part. By focusing on the proportional relationship between the extremely high point and the inlet refrigerant temperature and power supply current, and detecting the refrigerant temperature and power supply current on the inlet side, it is possible to detect temperature changes and current changes from non-frost to frost. The heating capacity is close to the limit by detecting temperature and power supply current at one point each. Furthermore, since the present invention does not detect frost formation until a certain period of time has elapsed from the start of heating, heating capacity is ensured during that certain period of time, and comfort is not impaired.

[Brief explanation of the drawing]

Fig. 1 is a block diagram expressing the defrosting control device of the present invention using function realizing means, Fig. 2 is a refrigeration cycle diagram of an air conditioner showing an embodiment of the present invention, and Fig. 3 is a diagram of the defrosting control device of the present invention. FIG. 4 is a circuit diagram of the defrosting control device, and FIG. The figure is a flowchart showing the operation details of the defrosting control device.
FIG. 6 is a characteristic diagram showing the relationship between the temperature of the refrigerant flowing into the indoor heat exchanger, the temperature of the refrigerant sucked into the compressor, and the power supply current of the air conditioner when the amount of refrigerant is insufficient in the defrosting control device. 1... Compressor, 2... Four-way switching valve, 3... Indoor heat exchanger, 4... Pressure reducer, 5... Outdoor heat exchanger, 6... Piping temperature detection element, 7... Indoor blower , 8... Outdoor blower, 9... Current detection element, 1
1...Microcomputer, 12...Storage unit,
13... Drive signal generation means, 14, 18... Comparator, 15, 16, 17... Temperature setting resistor, 19, 20... Current setting resistor, 21... Current voltage conversion circuit, A... Outdoor unit , B... Indoor unit.

Claims (1)

[Claims] 1. A refrigeration cycle equipped with a compressor, an indoor heat exchanger, a pressure reducing device, and an outdoor heat exchanger is provided with a cycle switching means for switching between a heating cycle and a defrosting cycle, and the cycle switching means switches from the heating cycle to the defrosting cycle. A control device for switching the cycle, a time measuring means for measuring time from the start of heating operation,
a set time storage means for storing a preset time; a first comparison means for detecting and outputting a match between the time detected by the time measurement means and the time set in the set time storage means; Temperature detection means for detecting the temperature of the part of the pipe connected to the refrigerant inlet side of the indoor heat exchanger through which superheated refrigerant gas flows, and a set temperature memory that stores the boundary value temperature for switching the heating cycle to the defrosting cycle. and second comparison means for detecting and outputting that the temperature detected by the temperature detection means has fallen below the boundary value temperature stored in the set temperature storage means;
current detection means for detecting a power supply current; set current storage means for storing a boundary value current for switching a heating cycle to a defrosting cycle; a third comparing means for detecting and outputting a drop below the current value, a set time elapsed signal from the first comparing means and a boundary value drop signal from the second comparing means, or the first comparing means; determining means for determining whether to switch from the heating cycle to the defrosting cycle based on the set time elapsed signal and the boundary value drop signal from the third comparison means; A defrosting control device for an air conditioner comprising selection output means for controlling defrosting operation.