JPH03213957A - Air conditioner - Google Patents

Abstract

PURPOSE:To perform a high reliable operation without fear of any compression of liquid by a method wherein when a temperature difference between a discharged refrigerant temperature of a compressor and a refrigerant condensing temperature at a condenser is less than a predetermined value, the number of revolution of a condenser cooling fan motor is decreased. CONSTITUTION:A difference between a discharging temperature of a compressor 1 to be detected by a temperature sensor 8 and a condensing temperature of refrigerant in a condenser 2 to be detected by a temperature sensor 9, i.e., a discharging over-heat is detected by control means 10 for the number of revolution. When the discharging over-heat is lower than a predetermined value, the number of revolution of a condenser cooling fan motor 5 is decreased. With such an arrangement, an amount of condensed and liquified refrigerant is decreased, a pressure of inputted refrigerant gas for the condenser 2 is increased, the discharging over-heat of the compressor 1 is kept at the predetermined value and the liquid compression is prevented. In this way, it is always possible to perform an efficient and reliable operation without any liquid compression.

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention provides a refrigerant circuit that connects at least a compressor, a condenser, a pressure reducer, and an evaporator, and includes a fan motor that drives a condenser cooling fan. Regarding air conditioners.

[Prior Art] Fig. 6 is a refrigerant circuit diagram showing a conventional air conditioner disclosed in, for example, Japanese Unexamined Patent Publication No. 64-57052. In the figure, (1) is a compressor, and (2) is a condenser. (3) is a pressure reducer,
(4) is the evaporator, (5) is a fan motor that drives the condenser cooling fan attached to the condenser (2), and (6) is a temperature sensor that detects the refrigerant temperature at the outlet of the condenser (2). vessel,(
7) is a rotation speed control means for controlling the rotation speed of the fan motor according to the output temperature signal of the temperature detector (6).

Next, we will explain the operation.0 The high-temperature, high-pressure gas discharged from the normal compressor (1) is directed to the condenser (2) as shown by the solid arrow.
), the high-temperature, high-pressure gas becomes a condensate by being cooled by the fan motor (5). After that, the refrigerant undergoes adiabatic expansion in the pressure reducer (3), becomes a low-pressure refrigerant, and the evaporator (
In step 4), it is heated and evaporated, becoming a low-pressure gas that is sucked into the compressor.

For example, when the outside temperature drops during cooling operation, the condenser (2
) becomes too large and the condenser (2)
The amount of liquefied refrigerant inside increases, the amount of refrigerant gas decreases, and the pressure of the refrigerant gas on the high pressure side decreases. Then, the pressure of the refrigerant further decreases after passing through the pressure reducer (3). As a result, the evaporator (4)
The evaporation temperature becomes too low and liquid refrigerant is sucked into the compressor (1) (hereinafter referred to as liquid compression).
, there is a possibility of damaging the compressor (1). To prevent this, the refrigerant temperature at the condenser outlet is detected by a temperature detector (6), and if the temperature is lower than a predetermined value, the rotation speed of the fan motor (5) is lowered by the rotation speed control means (7). Accordingly, the amount of heat exchanged in the condenser (2) decreases, the amount of liquefied refrigerant decreases, and the refrigerant sucked into the compressor (1) becomes completely gaseous, preventing damage to the compressor (1). Ru.

In this way, the reliability of the compressor is improved.

[Problem to be solved by the invention] Since the conventional air conditioner is configured as described above,
When a variable speed compressor with variable capacity is used and it is operated at low speed, the refrigerant temperature at the condenser outlet may become too low even if the outside temperature is not low. In this case as well, the rotation speed of the fan motor is lowered by the rotation speed control means, and there is a problem that sufficient heat exchange cannot be performed and efficient cooling operation may not be possible. This was developed to solve the above problems, and is a highly reliable air conditioner that operates efficiently and does not allow liquid refrigerant to flow into the compressor suction port even when the compressor rotation speed is low. The purpose is to obtain.

[Means for Solving the Problems] The air conditioner according to the present invention includes a discharge temperature detector that detects the temperature of the refrigerant discharged from the compressor, a condensation temperature detector that detects the condensation temperature of the refrigerant in the condenser, and both of these temperatures. A rotation speed control means is provided for reducing the rotation speed of the condenser cooling fan motor when the temperature difference detected by the detector is less than a predetermined value.

[Function] In this invention, the difference between the compressor discharge temperature and the condensing temperature,
That is, the discharge superheat degree is detected, and when the discharge superheat degree is lower than a predetermined value, the rotation speed of the condenser cooling fan motor is reduced. As a result, the amount of condensed liquefied refrigerant decreases, the input refrigerant gas pressure to the condenser increases, the degree of superheat discharged from the compressor is maintained at a predetermined value, and liquid compression is prevented. Also, even if the refrigerant temperature at the condenser outlet becomes too low while the compressor is operating at low speed,
If the liquid is not compressed, the degree of discharge superheat exceeding a predetermined value will not be detected and the rotation speed of the fan motor will not be reduced.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
5 to 5 show an embodiment of the present invention, FIG. 1 is a refrigerant circuit diagram, FIG. 2 is a fan motor control configuration diagram, FIG. 3 is a control circuit diagram, and FIG. 4 is an operating program. The flowchart and FIG. 5 are Mollier diagrams for explaining the operation. In the figure, (1) is a compressor, (2) is a condenser, (3) is a pressure reducer, (4) is an evaporator, (5) is a fan motor for cooling the condenser, and 1 or more are shown in Figure 6. This is similar to the conventional device. (8) is a discharge temperature detector that detects the discharge refrigerant temperature of the compressor (1), (9) is a condensing temperature detector that detects the condensation temperature of the condenser (2), and (10) is a discharge temperature detector ( 8
) and the condensing temperature detector (9) to change the rotation speed of the fan motor (5) according to the temperature difference detected by the condensing temperature detector (9). The memory (IOB) in which the operating program is stored, the discharge temperature detector (8) in the input end chain, and the condensation temperature detector (9) in the input end chain 2.
It has an input circuit (IOC) to which are respectively connected, and an output circuit (100) to which a fan motor (5) is connected to an output terminal 01.

Next, the operation of this embodiment will be explained. The flow of the refrigerant in Fig. 1 is the same as in the conventional example, so a special explanation is omitted.The rotation speed of the fan motor (5) is controlled according to the detection signals of the discharge temperature detector (8) and the condensation temperature detector (9). The operation of the rotation speed control means (10) will be explained with reference to the flowchart shown in FIG.

First, in step (11), a short period of time t after the start of operation.
, the discharge temperature detector (8) and the condensing temperature detector (9) are stabilized to some extent. The operation is normally continued for 30 minutes to 1 hour, and after the time has elapsed from the start of operation, step (1) is performed.
Proceeding to 2), the difference between the detected discharge temperature from the discharge temperature detector (8) to the input terminal 11 and the detected condensation temperature from the condensation temperature detector (9) to the input end chain 2.

In other words, it is determined whether the discharge superheat degree is greater than or equal to the predetermined value 61. If the discharge superheat degree is greater than the predetermined value ΔT, the program ends as is; if it is smaller, the program proceeds to step (13) and the fan motor (5) is controlled. and the rotation speed decreases.

Then, the amount of condensation in the condenser (2), that is, the amount of condensed liquefied refrigerant decreases, and the amount of refrigerant gas increases, increasing the refrigerant pressure, and as a result, the input to the compressor (1) increases. As the refrigerant pressure in the condenser (2) increases, that is, the pressure on the high pressure side of the compressor (1) increases, the discharge superheat degree also increases, and when that value becomes greater than the predetermined value ΔT, the program ends from step (12). , the rotation speed of the fan motor (5) is maintained as it is.

The flow state of the refrigerant at this time is shown in the Mollier diagram of FIG. In FIG. 5, the dotted line indicates a state in which the degree of discharge superheat has decreased, and the solid line indicates a state in which the degree of discharge superheat has increased due to a decrease in the rotation speed of the fan motor (5) by the rotation speed control means (10). . The degree of discharge superheat increases from A on the dotted line to B on the solid line.

In this way, the degree of discharge superheat represents the degree of liquid compression, which is how much liquid is compressed in the compressor, so it is important to always keep track of this degree of discharge superheat and its value is related to the reliability of the compressor (1). By controlling the temperature so that it does not fall below a predetermined value ΔT within 5 to 20 degrees, highly reliable and efficient operation is possible.

[Effects of the Invention] As described above, according to the present invention, when the temperature difference between the discharge refrigerant temperature of the compressor and the refrigerant condensation temperature in the condenser is below a predetermined value, the rotation speed of the condenser cooling fan motor is reduced. Since the rotation speed control means is provided, it is possible to obtain an air conditioner that can always operate efficiently and with high reliability without fear of liquid compression.

[Brief explanation of drawings]

Figures 1 to 5 show an embodiment of the present invention, where Figure 1 is a refrigerant circuit diagram, Figure 2 is a fan motor control configuration diagram, Figure 3 is a control circuit diagram, and Figure 4 is an operating program. Fig. 5 is a Mollier diagram for explaining the operation, Fig. 6 is a flowchart showing the
The figure is a refrigerant circuit diagram of a conventional air conditioner. In the figure, (1) is the compressor, (2) is the condenser, and (3)
is a pressure reducer, (4) is an evaporator, and (5) is a fan motor (
8) is a discharge temperature detector, (9) is a condensing temperature detector, (1
0) is a rotation speed control means. The same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] In an air conditioner, the refrigerant circuit connected to at least a compressor, a condenser, a pressure reducer, and an evaporator is provided with a fan motor that drives the condenser cooling fan, and the temperature of the refrigerant discharged from the compressor is detected. A discharge temperature detector, a condensing temperature detector that detects the condensation temperature of the refrigerant in the condenser, and a rotation speed control means that reduces the rotation speed of the fan motor when the detected temperature difference between both temperature detectors is below a predetermined value. An air conditioner characterized by the following: