JPS6018899B2 - Air conditioner capacity control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the capacity of an air conditioner that is capable of creating a comfortable environment by eliminating the offset phenomenon in which the room temperature deviates from the set temperature.

A method of controlling the capacity of an air conditioner using a frequency converter (inverter) has already been proposed, but normally the output frequency of the inverter is determined by the indoor temperature and the setting of the room temperature setting device, as shown in Figure 5. It is controlled by the temperature deviation ΔT from the temperature. According to this control method, even if the air conditioning load and the air conditioning function are balanced and the operating condition is stable, an offset (temperature difference △T'
) occurs, and this offset becomes larger as the operating frequency is higher and the air conditioning function is greater.

If the control has the characteristics shown in Figure 5, the room temperature will fluctuate depending on the operating frequency even without changing the set temperature, which will cause discomfort to the user, which is the main purpose of continuous control in air conditioners. It is clear that this goes against the point of trying to obtain a certain comfortable space.

In addition, in order to prevent such drawbacks from occurring as much as possible, if the deviation △T between the room temperature and the set temperature of the room temperature setting device is adjusted to be small or medium, the fluctuations in the heating frequency will become severe and the room temperature will increase. This resulted in a hunting condition, which was not favorable for the compressor, and therefore could not solve the problem.

Focusing on such conventional problems, the present invention proposes a novel capacity control method for an air conditioner that can create a comfortable space while solving the above-mentioned defects. When controlling the capacity by increasing or decreasing the rotation speed of the compressor using a frequency converter, the room temperature and the set temperature set with the room temperature setting device are detected and compared, and the temperature deviation △T is calculated intermittently, and the temperature deviation is When △T is calculated, the output frequency of the frequency converter is controlled to increase or decrease by the frequency conversion axis wealth △na corresponding to the temperature deviation △T, with respect to the frequency currently in operation. Until the calculation of the temperature deviation △T, the operation is performed at a constant frequency controlled based on the currently calculated temperature deviation △T, and the time △t from when the temperature deviation △T is calculated until the next calculation is performed is calculated based on the temperature deviation △
It is characterized by an indefinite time having an inversely proportional relationship to the absolute value of T.

In addition, the second invention is that after the temperature deviation △T is calculated, until the next calculation, the outside air temperature or the cooling operation and the heating are changed while the constant frequency is controlled based on the actually calculated temperature deviation △T. The output frequency is changed depending on the type of operation, and the third invention is such that the increase/decrease control of the output frequency to reach the constant frequency is changed with a gentle slope.

Hereinafter, the present invention will be explained in detail based on examples.

FIG. 1 is a flowchart of a compressor rotation speed control device according to an embodiment of the method of the present invention. 1 is a room temperature sensor installed at an appropriate location in the room, which converts room temperature into an electrical signal such as a change in resistance. This is what is output.

Reference numeral 2 denotes a room temperature setting device attached to the indoor unit of the air conditioner, and a manually operated room temperature setting device such as a variable resistor that can output an electric signal with a value corresponding to the temperature is often used.

3 is a temperature deviation detector which receives electrical signals output from the room temperature sensor 1 and the room temperature setting device 2 as input elements;
After calculating the polarity difference between both signals, the electrical output is amplified and transmitted to the frequency controller 4 at the next stage.

The temperature deviation detector 3 is configured not to output a fin air signal corresponding to the temperature deviation ΔT moment by moment, but to emit an electric signal when a signal is outputted from the time setting device 6 intermittently. ing. On the other hand, when the frequency controller 4 receives a signal from the temperature deviation detector 3, it issues a frequency control command corresponding to this signal, and sends this control command to the next stage frequency converter 5 to adjust the output frequency. control the increase/decrease.

As a result, the compressor motor 7 that receives power from the frequency converter 5 can control the capacity of the air conditioner by energizing the compressor at a rotational speed corresponding to the output frequency.

The content of the method of the present invention will be made clear by explaining the operation of the control device configured as described above. As shown in FIG. 2, the relationship between the temperature deviation ΔT and the output frequency N of the frequency converter 6 is fixed If △T is greater than the differential (in this case differential is a minute temperature difference that the user does not feel), the output frequency will be changed within the range commensurate with △T, that is, under control. Control is performed to increase or decrease the frequency by Δn with respect to the frequency currently in operation, and by doing so, the room temperature will always fall within the range of the differential.

The frequency is increased or decreased intermittently in consideration of the relationship between the air conditioning load and the air conditioning function, both of which have fairly large time constants.

For example, to explain the state when an air conditioner is started using FIG. 3, immediately after starting, △Nas is a low frequency
Operating at a constant temperature, the room temperature Ta that can be heard after △ts has elapsed
- Detect the set temperature To=T and increase the frequency by ΔN corresponding to ΔT from the ΔT-ΔN characteristic diagram in FIG.

As a result, at point a', it operates at a frequency of ('s0△〆,).

However, in FIG. 3, since 〆s+△〆・Z〆max (maximum frequency), it is operated at this maximum frequency. Next, at time t2, Tb-To=△L is detected, and △T2
△'2 corresponding to ('s + △ na,) is supposed to be operated at a frequency that is added to ('s + △ na,), but in this case, the frequency is already n, max
There is no further increase in frequency because of this.

Then, the operation is performed at Na max until t5, but at t5, the room temperature becomes lower than the set temperature, so △T5 is detected, △Na5 corresponding to 1△T5 is calculated from Fig. 2, and △〆 Decrease frequency by 5. As a result, at point C', the motor is operated at a frequency of (namax-Δ〆5). As described above, the temperature deviation △T is detected every time a certain period of time elapses for each △to, and if it is greater than or equal to the differential shown in the second figure, the △〆 corresponding to △T is currently in operation. The room temperature can be brought closer to the set value by increasing or decreasing the frequency of the temperature, and the room temperature is maintained at the set temperature without any offset.

After low-frequency startup in this way, high-speed (high-capacity) operation is performed until the set temperature is reached, which shortens warm-up time and has a great effect on distant cooling.
It is clear that this method is significantly different from the conventional control method shown by the broken line in the figure.

In the control mode described above, the time point at which the temperature deviation ΔT is calculated is
In this example, the detection time interval △to of △T is narrowed and △T
By performing multiple detections and controlling the frequency, it is possible to approach the set temperature more quickly and accurately.

Such control can be achieved by making the time from the calculation of △T to the next calculation maintain an inversely proportional relationship to the absolute value of △T, and is possible by providing the time setting device 6 with such a function. It is. By controlling the detection timing of ΔT using the absolute value of ΔT as described above, the following characteristics are exhibited.

If ΔT is large, the increase or decrease in frequency becomes large, and the fluctuation in the capacity of the air conditioner also becomes large, and the time changes rapidly.

In that case, if △t is fixed at a fixed time, there is a risk that the room temperature will not stabilize at the set temperature due to vertical hunting, but if △t is small and the output frequency is controlled when △T is large, hunting can be prevented. This allows the room temperature to quickly approach and maintain the set temperature.

Also, during the change in frequency with respect to △T shown in Fig. 2, △ is not only affected by a certain fixed characteristic A, but also by B depending on the outside temperature.
, C characteristics, etc. If the optimum one is selected from among different proportional constants, more effective room temperature control becomes possible.

Furthermore, since the operation control modes for the outside air temperature are reversed between the cooling operation and the heating operation, it is preferable to change ΔN in the same way while the frequency changes with respect to ΔT. However,
Changing the ΔT-Δn characteristic depending on the outside air temperature has the following effects.

For example, in the case of heating operation, if △T is 0.5 0 and △〆 is 10Hz on the opposite side, the outside air temperature is DB or o/WB.
Oko0 and DBIO.

Considering an example of an air conditioner in which the increase in heating capacity at C/WB6oo is controlled by a frequency conversion method, if the outside air temperature is DB2℃/WB0oo, the increase in heating capacity is 14%.
In the case of DBI0qo/WB6°C, the increase is 25%.
In this way, for the same value of ΔT, there is a considerable difference in the ability change.

If the capacity increase is large, the room temperature may exceed the set temperature and a hunting phenomenon may occur. Furthermore, if the capacity increment is small, it takes a long time to reach the set temperature, and in some cases, the output frequency must be further increased to increase the capacity. From this point of view, depending on the outside temperature,
By performing control to appropriately change the rate of change of Δn with respect to T, the function of bringing the room temperature closer to the set temperature more quickly and maintaining this temperature is achieved. On the other hand, if the ΔT-Δ〆 characteristics are changed depending on the difference between cooling operation and heating operation, the following effects can be obtained.

In other words, in the control of changing △T - △〆 according to the outside air temperature, the rate of change in capacity of the air conditioner decreases by 4.0% during cooling operation as the outside temperature increases, while the opposite occurs during heating operation. Changing △T-△na between cooling and heating is effective in providing a more comfortable feeling.

In addition, changes in outside air temperature are directly affected by the evaporation temperature during heating operation, and by the condensation temperature during cooling operation, but changes in air conditioner capacity are directly affected by changes in evaporation temperature than condensation temperature. It is natural that consideration for the outside temperature must be more strict during heating operation than during cooling operation, and therefore it is natural that it is more preferable to change the △T-△ characteristics depending on the difference in operation. be. The present invention further includes:
When controlling the output frequency to increase or decrease, if the control is performed stepwise over time as shown in Figure 3, the expansion valve of the air conditioner will not accurately follow the sudden change, causing the liquid to drop. Sudden rotational fluctuations are undesirable for the compressor because it may cause a return.

Therefore, as shown in Figure 4, by controlling the output frequency to increase or decrease with a relatively gentle slope with respect to time, it is possible to prevent damage to the compressor due to liquid return. be.

As is clear from the above description, the present invention calculates the temperature deviation △T between the actual room temperature and the set temperature intermittently when controlling the compression function using the frequency conversion method. After T is calculated, the output frequency of the frequency converter 5 is changed during frequency fluctuation corresponding to the calculated △T.
At the same time, after calculating the temperature deviation △T, until the next calculation, the operation is performed at a constant frequency controlled based on the currently calculated temperature deviation △T, and the temperature The special feature is that the time from when the deviation △T is calculated until the next calculation is made is an indefinite period of time that is inversely proportional to the absolute value of the temperature deviation △T.
In the conventional control method in which the relationship between the temperature deviation ΔT and the output frequency N of the frequency converter is fixed, an offset occurs with respect to the set temperature, impairing comfort, but the present invention eliminates the offset. This enables stable control close to the set temperature, which has the effect of further improving comfort.

In particular, at startup, high-capacity operation is performed continuously within a certain specified time, so the warm-up time is shortened because the operation reaches the set temperature quickly. Demonstrate.

Furthermore, the present invention changes the period of change in the output frequency in response to temperature deviation depending on the outside air temperature or whether cooling or heating operation is performed, so that the room temperature can be quickly brought close to the set value and the function of maintaining this temperature can be reliably exerted. In addition, while the rate of change in capacity of an air conditioner with respect to outside air temperature is opposite between cooling operation and heating operation, in the present invention, the rate of change in capacity is changed between cooling operation and heating operation. This has the effect of providing even more comfort.

Furthermore, the present invention controls the increase/decrease of the output frequency with a relatively gentle slope with respect to time, thereby preventing liquid return and preventing damage to the compressor. It has the advantage of preventing As described above, the method of the present invention reliably guarantees the creation of a comfortable environment that could not be achieved with conventional methods of this type, and is therefore an extremely useful capacity control method.

[Brief explanation of drawings]

Fig. 1 is a flowchart of a capacity control device according to the method of the present invention, Figs. 2 to 4 are characteristic diagrams graphically showing various characteristics related to the method of the present invention, and Fig. 5 is a conventional frequency conversion method. It is a characteristic diagram of the capacity control method by. 2... Room temperature setting device, 5... Frequency converter, 7... Compressor. 5 diagrams of filial children, 5 diagrams of filial

Claims (1)

[Claims] 1. When the frequency converter 5 increases or decreases the rotation speed of the compressor 7 to control its capacity, the room temperature and the set temperature set by the room temperature setting device 2 are detected and compared, and the temperature deviation ΔT is calculated. If the temperature deviation ΔT is calculated intermittently, the output frequency of the frequency converter 5 is controlled to increase or decrease by the frequency conversion width Δf corresponding to the temperature deviation ΔT with respect to the frequency currently in operation, and the temperature deviation is After calculating ΔT, until the next calculation, the system was operated at a constant frequency controlled based on the actually calculated temperature deviation ΔT to prevent deviation from the set temperature, and the temperature deviation ΔT was calculated. A capacity control method for an air conditioner, characterized in that the time Δt until the next calculation is performed is an undefined time having an inversely proportional relationship to the absolute value of the temperature deviation ΔT. 2. When the frequency converter 5 increases or decreases the rotation speed of the compressor 7 to control the capacity, detect and compare the room temperature and the set temperature set by the room temperature setting device 2, and calculate the temperature deviation ΔT intermittently. At the same time, if the temperature deviation ΔT is calculated, the output frequency of the frequency converter 5 is controlled to increase or decrease by the frequency conversion width Δf corresponding to the temperature deviation ΔT with respect to the frequency currently in operation, and after calculating the temperature deviation ΔT, the following Until the calculation, the system is operated at a constant frequency controlled based on the actually calculated temperature deviation ΔT to prevent deviation from the set temperature, and the range of change Δf of the output frequency with respect to the temperature deviation ΔT is A method for controlling the capacity of an air conditioner, characterized in that the capacity is changed depending on the outside temperature or whether cooling operation or heating operation is performed. 3 When controlling the capacity by increasing or decreasing the rotation speed of the compressor 7 using the frequency converter 5, detect and compare the room temperature and the set temperature set by the room temperature setting device 2, and calculate the temperature deviation ΔT intermittently. At the same time, if the temperature deviation ΔT is calculated, the output frequency of the frequency converter 5 is controlled to increase or decrease by the frequency conversion width Δf corresponding to the temperature deviation ΔT with respect to the frequency currently in operation, and after calculating the temperature deviation ΔT, the following Until the calculation, the operation is performed at a constant frequency controlled based on the actually calculated temperature deviation ΔT to prevent deviation from the set temperature, and the output frequency is controlled to increase or decrease depending on the temperature deviation ΔT. A method for controlling the capacity of an air conditioner, characterized in that the capacity of an air conditioner is changed not in stages but with a gentle slope.