JPS6333623B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a defrosting method for an air source heat pump type air conditioner.

First, an air source heat pump type air conditioner will be briefly described with reference to FIGS. 1 and 2. FIG. 1 is an explanatory diagram showing a schematic configuration of an air source heat pump type air conditioner, and FIG. 2 is an electrical system wiring diagram thereof. In FIG. 1, 1 is a compressor;
2 is a four-way switching valve, 3 is a heat source side heat exchanger provided outdoors, 4 is an expansion valve such as a capillary tube, and 5 is a user side heat exchanger provided indoors. These are connected by piping as shown in the figure, and a refrigerant is circulated inside the piping. In the figure, the arrows along the pipes indicate the direction of refrigerant circulation, the solid arrow x indicates the circulation method during heating operation, and the broken arrow y indicates the circulation direction during cooling operation and defrosting operation. An indoor fan 7 driven by an electric motor 6 is provided near the user-side heat exchanger 5. The indoor air blower 7 sucks indoor air through the heat exchanger 5 as shown by the arrow in the figure, and blows it out into the room from the outlet. A suction temperature detecting element 8 and a blowing temperature detecting element 9 are provided at the air inlet and outlet, respectively.
On the other hand, an outdoor air blower driven by an electric motor 10 is disposed near the heat source side heat exchanger 3. All operations of the electrical system of the air conditioner configured as described above are controlled by an electronic control section 11. Next, the electrical system will be explained. In FIG. 2, 12 is a power transformer for the electronic control section 11. The compressor 1, the four-way switching valve 2, the drive motor 6 of the indoor blower 7, the temperature detection elements 8 and 9, and the drive motor 10 of the outdoor blower are all controlled by an electronic control unit 11.
It is connected to the. Also, in the figure 13', 14', 1
5' are contacts that are opened and closed by electromagnetic contactors 13, 14, 15, respectively;
5 is connected to the electronic control section 11. and,
The electronic control section 11 is provided with a remote control operation section 16 .

During heating operation of the air heat source heat pump type air conditioner having the above configuration, the remote control operation unit 1
6, conduction is made to the electronic control unit 11 via the power transformer 12, and then the electromagnetic contactors 13, 1
4 and 15 are energized to connect the respective contacts 13', 14', and 1.
By closing 5', the compressor 1, the four-way switching valve 2, the outdoor ventilation motor 10 are operated, and the indoor ventilation motor 6 is also operated. The high-temperature, high-pressure refrigerant discharged from the compressor 1 is introduced into the user-side heat exchanger 5 installed indoors through the four-way switching valve 2 as shown by the arrow x, where it is condensed and liquefied to release the heat of condensation. . Then, this released heat is absorbed by the indoor air sucked through the heat exchanger 5 by the indoor air blower 7, and the air warmed by this heat exchange is blown out from the outlet as warm air. On the other hand, the refrigerant liquefied in the user-side heat exchanger 5 is depressurized by the expansion valve 4 and introduced into the heat source-side heat exchanger 3 installed outdoors, where it is evaporated and vaporized, and then passed through the four-way valve 2. Returns to compressor 1.

By the way, since the temperature of the heat source side heat exchanger 3 decreases due to evaporation of the refrigerant, frost may adhere to the heat exchanger 3 depending on the operating state, such as when the outside air is extremely low temperature and high humidity. When the amount of accumulated frost exceeds a certain limit, the heat exchange efficiency on the heat source side decreases and the heating capacity begins to decrease, impeding efficient heating operation. Therefore, it is necessary to melt the adhering frost before the performance decreases significantly due to frost accumulation. This defrosting is performed by operating the refrigeration cycle in the opposite direction, that is, by circulating the refrigerant in the direction of arrow y in FIG. This defrosting operation generates condensation heat of the refrigerant in the heat source side heat exchanger 3, and the accumulated frost is melted.

Now, the defrosting operation in the above-mentioned air source heat pump type air conditioner has conventionally been performed as follows. That is, during heating operation, the temperature sensing elements 8, 9
Intake temperature Ti and outlet temperature of indoor air detected in
A method has been adopted in which the temperature difference ΔT=T ₀ −Ti with respect to T ₀ is used as an index of heating capacity, and defrosting operation is started when this temperature difference ΔT falls below a certain value due to frost formation. This is disclosed in Japanese Patent Publication No. 48-20825, and more specifically, the maximum temperature difference ΔTmax during one cycle is memorized, and the temperature difference ΔT measured during heating operation is set at a predetermined ratio to ΔTmax. Defrosting operation is started when the temperature drops to below.

However, in reality, the factors that affect the above temperature difference ΔT are not only the accumulation of frost due to frost formation, but also changes in air volume caused by switching the air volume of the indoor and outdoor blowers 7 and 10, adjusting the air direction adjustment plate, etc., and the power supply voltage. Sudden fluctuations in temperature, changes in capacity due to a compressor with a capacity control device, etc. also affect the temperature difference ΔT (hereinafter, these factors other than frost formation that affect ΔT are referred to as disturbances). Furthermore, with conventional methods, it is not possible to determine whether the change in ΔT is due to frost formation or external disturbance, which causes the problem that defrosting operation is started even when there is no frost formation. was occurring.

The present invention has been made in view of the above circumstances, and it solves the inconvenience that occurs when defrosting operation is started even though there is no frost accumulation on the heat source side heat exchanger, and also eliminates the frost accumulation. To provide a defrosting method for an air conditioner that can appropriately start defrosting operation when the defrosting occurs.

That is, the present invention starts the defrosting operation when the temperature difference ΔT between the inlet air temperature and the outlet air temperature of the user-side heat exchanger decreases to a preset ratio with respect to the stored maximum value ΔTmax. In the defrosting method for an air-source heat pump air conditioner, if the absolute value of the first-order differential value of the temperature difference ΔT with respect to time is smaller than a predetermined value, the temperature difference ΔT is used as is, and the first-order differential value of the temperature difference ΔT with respect to time is This defrosting method is characterized by automatically correcting the temperature difference ΔT when the absolute value is larger than a predetermined value.

The defrosting method of the present invention is based on the experimentally confirmed fact that the temporal change in the temperature difference ΔT due to disturbance is much larger than the temporal change in ΔT due to frost accumulation. In other words, only when the first-order differential value of the measured temperature difference ΔT with respect to time is calculated and its absolute value is smaller than a predetermined value is the state change considered to be due to frost formation, and only in this case is the same deduction as before applied. Implement frost method. On the other hand, if the absolute value of the first-order differential value of the temperature difference ΔT with respect to time is larger than the predetermined value, the state change at that time is considered to be caused by a disturbance. Then, monitoring of ΔT is prohibited for a certain time a from time τ ₃ when the disturbance occurs, and ΔT at time τ ₃ +a is monitored.
Then, the correction coefficient k of the temperature difference ΔT with respect to disturbance is defined by the following equation (1), and the temperature difference ΔT is calculated as ΔT (τ=τ ₃ +a) × k (=ΔT (τ=τ ₃ )). Then, the correction coefficient k is used to automatically correct the disturbance of ΔT.

k=ΔT(τ=τ ₃ )/ΔT(τ=τ ₃ +a)……
(1) A more detailed explanation will be given below with reference to FIGS. 3 to 6.

Fig. 3 is a diagram showing changes in the air volume of the indoor blower with respect to the operating time of the air conditioner, Fig. 4 is a diagram showing changes in the indoor suction temperature Ti and outlet temperature T ₀ ,
Figure 5 is a diagram showing changes in ΔT (ΔT=T ₀ −Ti),
Figure 6 shows the first-order differential value I (I=
FIG. 3 is a diagram showing changes in ∂(ΔT)/∂τ). In FIGS. 3 to 6, the time τ on the horizontal axis is synchronized.

First, from time τ ₀ , the air volume of the indoor fan 7 is set to L ₀
When heating operation is performed at a constant level, the outlet temperature T ₀ and ΔT rise rapidly and reach ΔTmax.
After that, T ₀ and ΔT gradually decrease due to the influence of frost formation. At time τ ₁ , ΔT is the value t determined at which the defrosting operation should start.
(0.7 to 0.8 times ΔTmax), and therefore, defrosting operation is started at this point. Since no disturbance is acting on this operation cycle, defrosting can be carried out using the same conventional method without any problem.
Note that during the defrosting operation, the indoor air blower 7 is stopped.

When the frost that has formed in the defrosting operation is completely removed in this way, the heating operation is restarted at time τ ₂ and at the same time, the indoor fan 7 also restarts its operation at the air volume L ₀ level. Therefore, as mentioned above, ΔT is
After rapidly increasing with T ₀ and reaching ΔTmax,
gradually decreases. Now, before ΔT decreases to t, the air volume of the blower 7 is set to Hi at time τ ₃ .
Switch to level. Then, due to this disturbance
Along with T ₀ , ΔT also rapidly decreases to below t. Therefore, with conventional defrosting methods, defrosting operation would start at this point, but since the decrease in ΔT at this time is not due to frost formation but to external disturbances, defrosting operation is completely unnecessary. This is as already stated. In the present invention, this unnecessary defrosting operation is avoided by determining the change in ΔT due to disturbance from the first-order differential value I=∂(ΔT)/∂τ of ΔT with respect to time.

As shown in FIG. 6, the change in I when ΔT changes due to disturbance is extremely large compared to the change in I when ΔT changes due to frost formation. Therefore, by constantly calculating I and comparing its absolute value |I| with a predetermined value C, it can be determined that the sudden decrease in ΔT below t at time τ ₃ is due to disturbance rather than frost formation. can be detected.

Once the change in ΔT due to disturbance is detected in this way,
Since the defrosting operation is not started due to this decrease in ΔT, in the present invention, monitoring of ΔT is first prohibited within a certain time a until the change due to disturbance stabilizes. It is sufficient to select 5 to 10 minutes as this fixed time a. Then, ΔT is monitored at the time point of τ=τ ₃ +a, and a correction coefficient k of ΔT due to disturbance is calculated and stored according to the above equation (1).

k=ΔT(τ=τ ₃ )/ΔT(τ=τ ₃ +a)……
(1) Now, as shown in Figure 4, T ₀ continues to decrease even after τ = τ ₃ + a when the disturbance has stabilized, so if no correction is made to ΔT that is monitored after that, then In this case, an unnecessary defrosting operation will be performed as a result. Therefore, in the present invention, the defrosting operation is properly performed by multiplying the correction coefficient k by the ΔT monitored after time τ=τ ₃ +a. That is, the amount of frost formed during the certain time a is assumed to be zero, and τ=
By setting ΔT at τ ₃ and ΔT at τ=τ ₃ +a to be equal, it is possible to monitor the amount of frost formation using ΔT as shown in FIG. As a result, after τ=τ ₃ +a, the defrosting operation is started at the time point τ=τ ₄ when k(T ₀ −Ti) decreases to t.

FIG. 7 shows a flowchart of the defrosting control according to the present invention described above.

Although the explanation has been given by citing a change in the air volume of the indoor fan as a disturbance factor, the method of the present invention is also effective for other disturbance factors.

According to the present invention as detailed above, it is possible to prevent unnecessary defrosting operation due to external disturbances, and to perform defrosting operation appropriately when frost formation occurs.
Therefore, the feeling of heating can be improved and energy can be used effectively throughout the year.
In addition, it is possible to configure the system to self-determine and self-compensate for disturbances based on changes in the temperature difference ΔT, eliminating the need to provide input signals for each cause of disturbance, and allowing the electronic control unit to program Since it can be easily configured with a small capacity, it has a practical effect that it can be realized without a significant increase in cost.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a schematic configuration of an air source heat pump type air conditioner, FIG. 2 is a schematic explanatory diagram showing its electrical system, and FIGS. 3 to 6 show a defrosting method according to the present invention. An explanatory diagram, FIG. 7, is a flowchart of defrosting control according to the present invention. 1... Compressor, 2... Four-way switching valve, 3... Heat source side heat exchanger, 4... Expansion valve, 5... User side heat exchanger, 6, 10... Air blower motor, 7... Room Inner blower, 8, 9...Temperature detection element, 11...Electronic control unit.

Claims (1)

[Claims] 1 An air source heat pump type that starts defrosting operation when the temperature difference ΔT between the inlet air temperature and outlet air temperature of the user-side heat exchanger decreases to a set percentage of the stored maximum value ΔTmax. In the defrosting method for air conditioners, when the absolute value of the first derivative of the temperature difference ΔT with respect to time is smaller than a predetermined value, the temperature difference ΔT is used as is, and when the absolute value of the first derivative larger than the predetermined value appears, A correction coefficient is calculated by comparing and calculating the temperature difference ΔT before and after, and after an absolute value of a first-order differential value larger than a predetermined value appears, a correction value obtained by multiplying the temperature difference ΔT by the correction coefficient is output. How to defrost an air conditioner.