JPH063323B2 - Overload protection control method for air conditioner - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overload protection control method for an air conditioner having a variable speed compressor.

2. Description of the Related Art Generally, when a heating operation is performed in an air conditioner, the condensing pressure of the refrigerant rises and the usage limit of the compressor is often exceeded when the indoor or outdoor temperature is high. If such an overloaded state is left as it is, the life of the compressor is significantly impaired and the temperature of the electric motor for the compressor is abnormally increased. Therefore, various protections have been invented.

A conventional example will be described with reference to FIG.

In the case of an air conditioner that has a compressor with variable capacity, the condensing pressure is determined from the usage limit of the compressor by a condensing temperature corresponding to the condensing pressure (also called high pressure) and a temperature sensor that detects the blowout temperature of the indoor unit. When a constant value here, which exceeds 24 atg at point B, is detected, the compressor is changed from the normal capacity operation state up to that point to a preset low capacity state, whereby the condensation pressure decreases to 18 atg. In general, the control to return the compressor to the original operating state was common. Although this example describes cooling, the same applies to heating.

Problems to be Solved by the Invention However, the above-mentioned conventional example has the following problems.

The capacity of the compressor is basically determined by the difference between the room temperature T _R and the set value T _S of the temperature controller. When the difference between T _R and T _S is large, a large capacity is required. If, when the room temperature T _R and the outdoor temperature T _O is high, it tends to exceed (24Atg in the example) the condensation pressure limit.

However, the pressure function force decreases beyond the limit pressure (hereinafter referred to as P ₁₁₎ pressure limit pressure - reduced to a differential amount (hereinafter referred to as P _12), the compressor returns to the original capacity, again the pressure There that exceeds P _11, fitted in a loop operation, until the original compression force rises room temperature T _R is sufficiently decreases, get stuck from the loop operation. During this loop operation, the volume and frequency of the compressor noise change frequently, so it feels very noisy.

In order to prevent this loop operation, it is preferable to increase the difference between P ₁₁ and P ₁₂ or increase the compression function force value at the time of low capacity. However, P ₁₁ is determined by the specifications of the compressor, and increasing the value causes significant technical difficulty and increases the cost of the compressor. Further, if P ₁₂ is lowered, the compressor continues to rotate with a low capacity, so that the capacity is insufficient and the room temperature is lowered, or it takes a long time to rise the room temperature. In addition, when the compression function force value at low capacity is increased, the change in the condensing pressure may temporarily become extremely high due to the large time delay with respect to the change in the rotation speed, and there is an upper limit for this value. Therefore, it is difficult to raise the loop operation to prevent it.

It is an object of the present invention to eliminate the loop operation of compressor capacity change that has occurred due to protection control during overload of an air conditioner without deterioration of capacity or protection function.

Means for Solving the Problems In order to solve the above problems, the present invention provides a compressor, a variable speed compressor motor, a four-way valve, a pressure reducing device, a use side heat exchanger,
Heat source side heat exchanger, means for setting temperature of air taken into the air conditioner on the use side and its detecting means, and refrigerant condensing pressure or discharge pressure detecting means, P ₁₁ > P ₁₂ , P ₁₂ > P
₂₂ ......> _Pn2 and pressure storage means for storing a preset condensation or discharge pressure value, and Nn >>
A method for controlling an air conditioner, comprising: a rotation speed storage means for storing a preset compressor motor rotation speed in a relation of N ₂ > N ₁ (N ₁ is a minimum operation rotation speed of the compressor). When the pressure detected by the detection means becomes equal to or higher than the pressure P ₁₁ stored in the pressure storage means, the rotational speed Nu (> N ₂ ) of the compressor electric motor is set to the rotational speed N stored in the rotational speed storage means. ₁ , the rotation speed is set to N ₂ when the pressure is less than P ₁₂ , and the rotation speed is set to N _{i + 1} when the pressure is less than P _i2.
When it becomes less than _n2 , the rotation speed is returned to the normal rotation speed Nu which is not subjected to the overload control of the present invention.

Operation With the above-described configuration, the overload protection control method for the air conditioner of the present invention is N when the compressor speed exceeds the condensing pressure P _11.
It is the same as in the conventional example until it is reduced to _1, and if P ₁₁ and N ₁ are equal to the conventional _one , the protection function is not reduced. However, after that, when the pressure falls below P ₁₂ , the rotational speed is not increased to Nu in accordance with the pressure P, but is sequentially increased to a plurality of intermediate rotational speeds N _{2 to} Nn, and the pressure is stabilized by balancing at intermediate rotational speeds. Try. Since there are a plurality of intermediate rotation speeds, there is a higher probability of stabilization in the middle than when a single intermediate rotation speed is provided, and therefore the frequency of loop operation is also reduced. Also,
When stabilized at an intermediate rotation speed, the capacity also hardly deteriorates in the average capacity as compared with the case where the loop operation is performed between the low capacity N and the high capacity Nu.

Embodiment An overload protection control method for an air conditioner according to an embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 is a compressor, 2 is a four-way valve, 3 is a heat source side heat exchanger, 4 is a use side heat exchanger, 5 is a pressure reducer, 6 is a compressor driving electric motor, and 7 is rotation of the electric motor 6. An inverter for changing the number, 8 is a fan for the heat source side heat exchanger, 9 is a fan for the use side heat exchanger, 10 is a room temperature sensor for detecting the temperature of the air flowing into the use side heat exchanger 4, and 11 is the setting of this air temperature. , 12 is a temperature comparison means for the room temperature sensor 10 and the setting device 11, 13 is a pressure detection means for detecting the condensation pressure, 14 is a set condensation pressure storage means, 15 is a set rotation speed storage means, 16
Is a pressure comparing means of the pressure detecting means 13 and the condensing pressure storing means 14, 100 is a computing unit for judging and computing the number of revolutions based on the results of the temperature comparing means 12 and the pressure comparing means 16 and the set number of revolutions storing means 15, Reference numeral 101 denotes a rotation speed change command means for giving a rotation speed change command to the inverter 7 in response to a command from the arithmetic unit 100.

Next, the operation will be described with reference to FIGS. Four-way valve 2
Is switched to a direction in which the refrigerant is circulated during the heating operation, and the refrigerant absorbs heat by the heat source side heat exchanger 3 and evaporates by heat dissipation in the use side heat exchanger 4 to perform a heating operation. Here, when the amount of heat absorption is large, the amount of heat radiation is small, that is, when the indoor / outdoor temperature is high or the amount of air blown by the fan 9 for the heat exchanger on the use side is small, the condensing pressure becomes high, and when it is extremely high, the compressor Damage and shorten its life, or in extreme cases lead to destruction.

Assuming that the limit condensing pressure that does not bring about such a state is P _L , the overload control start pressure P having a relation of P ₁₁ <P _L
11 is set. (P _L −P ₁₁ ) is a value that plays a role of a safety factor that is determined by the tolerance of the pressure detection means. However (P L _{-P 11)} and taking up too large a condensation pressure and the corresponding air temperature, P ₁₁ for leading to reduction in the heating capacity is set higher as possible.

Before the overload control is started, that is, in the state of the condensing pressure P <P ₁₁ , the compressor 1 rotating at the rotation speed Nu determined by the difference between the use side air temperature and the set temperature is P ≧ P.
_When it becomes ₁₁ , the overload control is started and the rotation speed is reduced to N ₁ .
N ₁ is a rotational speed determined to be sufficiently low so that P <P _L is maintained even in that case because the condensation pressure changes with a slight delay when the rotational speed decreases from Nu to N ₁ . When the load is extremely high, the pressure P does not decrease even when it becomes N ₁ as shown by an arrow A in FIG. 2, and it stabilizes in the vicinity of P ₁₁ and usually decreases.

P ₁₂ <decided _{P 12} having a _{P 11} the relationship, raised and the condensing pressure P _{<P 12} the rotational speed _{N 2.} Thereafter, each time the pressure falls below P _i2 , the rotation speed is changed to N _{i + 1} . N
_{2 to} Nn are higher than N ₁ and smaller than Nu. In actual operation, Nu may be Nn or less, but in this case, the control routine may be different from the present invention.

Here, when the load is considerably high, the condensing pressure P rises again and the rotation speed returns to N _1, and thereafter, as shown by the arrow B in FIG. ₂ , the loop operation is started between N ₁ and N ₂ , but the conventional Nu Compared with the loop operation of N ₁ and N ₁ , there is less difference in the number of revolutions, so there is not much problem.

When the load is a little low, the rotation speed and the pressure stabilize at somewhere from N _{2 to} Nn as shown by the arrow C in FIG. 2, and when the load is further lower, it falls below the overload control end pressure P _n2 and the rotation speed returns to Nu. ,
It enters a loop operation shown in FIG. 2 arrow D beyond the P ₁₁ and the pressure rises again. However, the pressure at N ₂ is lower than P _n2 only when the load is relatively low, and in that case, the rotation speed is Nu.
However, the pressure rises slowly and does not result in frequent loop operation. That is, in the load region where the loop operation is most frequently performed in the past, it stabilizes at any one of N _{2 to} Nn, so that not only the noise is greatly improved, but N _{2 to} Nn are generally equal to those of N ₁ and Nu. Since the rotational speed is an intermediate value, the capacity is equivalent to the average capacity when the loop operation is performed between N ₁ and Nu.

In this embodiment, the condensing pressure is detected and the overload control is performed.However, the discharge pressure of the compressor, the condensing temperature of the heat exchanger, the outlet temperature after passing through the heat exchanger on the use side, etc. correspond to the condensing reaction. Therefore, it is possible to detect these values and use values set appropriately according to the values instead of P ₁₁ , P ₁₂ , P ₂₂ , ... P _n2 .

Although the compressor rotation speed is controlled, the compressor current value may be used instead.

EFFECTS OF THE INVENTION As is apparent from the description of the above-described embodiments, the present invention protects the compressor at the time of overload in the same manner as the conventional one, and significantly hunts the compressor rotational speed by the loop operation that frequently occurs conventionally. It is possible to secure an average capacity equivalent to that of the conventional one, while significantly improving the actual hearing of compressor noise.

[Brief description of drawings]

FIG. 1 is a device configuration diagram of an air conditioner showing an embodiment of the present invention, FIG. 2 is an explanatory diagram showing an operating condition of the air conditioner, and FIG. 3 is a flowchart showing control contents of the air conditioner. ,
FIG. 4 is an explanatory diagram showing the operation of the conventional example. 1 ... Compressor, 2 ... Four-way valve, 3 ... Heat source side heat exchanger,
4 ... Utilization side heat exchanger, 5 ... Pressure reducer, 6 ... Compressor driving electric motor, 7 ... Inverter, 8, 9 ... Blower, 1
0 ... Room temperature sensor, 11 ... Room temperature setting device, 12 ... 10
.11 comparison means, 13 ... condensation pressure detection means, 14 ...
Condensing pressure storage means, 15 ... Rotation speed storage means, 16 ... 1
3 · 14 comparison means, 100 ... arithmetic unit, 101 ... rotation speed change command means.

Claims (3)

[Claims] 1. A compressor, a variable speed electric motor for a compressor, a four-way valve, a pressure reducing device, a heat exchanger on the use side, a heat exchanger on the heat source side, and means for setting the temperature of the air taken into the air conditioner on the use side. The detecting means and the pressure detecting means for detecting the refrigerant condensing pressure or the discharge pressure, P ₁₁ > P ₁₂ , P ₁₂ > P ₂₂ > ...
...> P _n2 and a pressure storage means for storing a preset condensation or discharge pressure value, and N _n >...> N ₂
> N ₁ (N ₁ is the minimum number of times of operation of the compressor), and a rotation speed storage means for storing the rotation speed of the compressor motor preset in relation to the control method of the air conditioner, When the pressure detected by the pressure detection means becomes equal to or higher than the pressure P ₁₁ stored in the pressure storage means, the rotation speed Nu (> N _n ) of the compressor electric motor that has not been subjected to overload control until then. To the rotation speed N ₁ stored in the rotation speed storage means, the rotation speed is N ₂ when the pressure is _lower than P ₁₂ , and the rotation speed is N when the pressure is _lower than P _i2.
The overload protection control method for an air conditioner, wherein the operation of setting _{i + 1} is repeated and when the pressure becomes less than P _n2 , the rotation speed is returned to the normal rotation speed Nu which is not overloaded. 2. The pressure detecting means for detecting the condensation or discharge pressure is a temperature detecting means for detecting the temperature of blown air at the utilization side heat exchanger or its downstream side, and set pressures P ₁₁ , P.
₁₂ , P ₂₂ , ..., P _n2 respectively corresponding to heat exchangers or blown air temperatures T ₁₁ , T ₁₂ , T ₂₂ ,.
, T _n2 , The overload protection control method for an air conditioner according to claim 1. 3. A rotational speed _{N 1,} N 2, ..., compressor current value _{A 1,} A 2 of the _{N n} corresponding thereto, ..., the first term claims was _{A n} or paragraph 2 An overload protection control method for an air conditioner as described.