JP2003262385A - Air conditioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air conditioner inexpensive in manufacturing cost and improved in reliability. <P>SOLUTION: In this air conditioner, a compressor 1, a condenser 4, a pressure reducing device 7, and an evaporator 3 are connected by a pipe. Evaporator inlet temperature and a condenser outlet temperature are detected. The suction pressure and the discharge pressure of the compressor 1 are respectively calculated from the evaporator inlet temperature and the condenser outlet temperature, thereby obtaining an operation pressure ratio that is a ratio between the suction pressure and the discharge pressure of the compressor 1. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an air conditioner,
In particular, it is suitable for the capacity control by detecting the operating pressure ratio which is the ratio of the compressor discharge pressure and the compressor suction pressure of the refrigeration cycle.

[0002]

2. Description of the Related Art Conventionally, in an air conditioner, in order to obtain an operating pressure ratio, it is known that pressure sensors are provided on the high pressure side and the low pressure side of a refrigeration cycle, and calculation is performed from the ratio of the values of the pressure sensor. It is described in Japanese Patent Laid-Open No. 5-10608. Also, a temperature sensor is installed in the low-pressure side refrigerant passage of the refrigeration cycle, the saturation pressure of the temperature sensor installation part is calculated from the output signal of the temperature sensor, and the pressure loss from the temperature sensor installation part to the compressor suction side is estimated. It is known that the compressor suction pressure is calculated as described in JP-A-8-121916.

[0003]

In the case of using the above-mentioned pressure sensor of the prior art, the cost of the pressure sensor itself is high and it is disadvantageous in terms of price, and the temperature sensor provided with the compressor suction pressure in the low pressure side refrigerant passage. It is estimated that when the piping that connects the indoor unit and the outdoor unit is long, the temperature at the temperature sensor installation part becomes low even though the refrigerant on the compressor suction side is overheated, and the suction pressure is estimated. There is an error in the value,
The estimation accuracy of the operating pressure ratio may decrease. further,
In both the cooling operation and the heating operation, the temperature sensor must be increased in order to detect the operating pressure ratio, which is also disadvantageous in terms of price.

An object of the present invention is to solve the above-mentioned conventional technical problems, to provide an air conditioner which is inexpensive in manufacturing cost, detects an operating pressure ratio with high accuracy, and has high reliability.

[0005]

In order to achieve the above object, the present invention provides an evaporator in an air conditioner in which a compressor, a condenser, a pressure reducing device, and an evaporator are connected by piping to form a refrigeration cycle. The inlet temperature and the condenser outlet temperature are detected, the suction pressure of the compressor is calculated from the evaporator inlet temperature, and the discharge pressure of the compressor is calculated from the condenser outlet temperature, and the discharge pressure of the compressor is calculated. The operating pressure ratio, which is the ratio of the suction pressure, is obtained.

Further, in the above, it is desirable that the suction pressure is obtained in relation to the operating frequency of the compressor and the length of the pipe connecting the condenser and the evaporator.

Further, in the above-mentioned apparatus, an expansion valve having a variable opening degree is provided on the condenser outlet side, and a receiver for storing excess refrigerant is provided at the outlet of the expansion valve, and the expansion valve is fully opened, that is, expansion is performed. It is desirable to obtain the operating pressure ratio by increasing the opening so as to reduce the pressure loss in the valve.

Further, in the above-mentioned ones, the suction pressure includes a saturation pressure on the suction side, a value proportional to the motor rotation speed of the compressor plus a coefficient, and a pipe length connecting the condenser and the evaporator. It is desirable to find it in relation to the power of the sum value.

Further, in the above, it is desirable to control the operating frequency of the compressor so that the obtained operating pressure ratio falls within a predetermined range.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a refrigeration cycle configuration, which is roughly divided into an outdoor unit 100 and an indoor unit 200, and the outdoor unit 100 and the indoor unit 200 are connected by a liquid side connection pipe 51 and a gas side connection pipe 50. Outdoor unit 100
Is a compressor 1, a four-way valve 2, an outdoor heat exchanger 4, an outdoor fan 5
The outdoor heat exchanger 4 is provided with a temperature sensor 21 at a position on the outlet side when acting as a condenser and on the inlet side when acting as an evaporator. In addition, the indoor unit 200 includes an indoor heat exchanger 3, an indoor expansion valve 7, and an indoor fan 6, and the indoor heat exchanger 3 has an outlet side when acting as a condenser like the outdoor heat exchanger 4, When operating as an evaporator, the temperature sensor 2 is placed at the position on the inlet side.
Two are provided. The signals of the temperature sensors provided in the indoor heat exchanger 3 and the outdoor heat exchanger 4 are wired so as to be input into the microcomputer 20.

Next, the operation of the refrigeration cycle will be described. In FIG. 1, solid arrows indicate the direction of refrigerant flow during cooling operation, and dashed arrows indicate the direction of refrigerant flow during heating operation. In the cooling operation, the high-temperature high-pressure gas refrigerant compressed by the compressor 1 flows into the outdoor heat exchanger 4 through the four-way valve 2 and exchanges heat with the air sent to the outdoor heat exchanger 4 by the outdoor fan 5. It is condensed and liquefied to flow out from the outdoor heat exchanger 4. The condensed and liquefied refrigerant passes through the liquid side connection pipe 51, is decompressed by the indoor expansion valve 7, becomes a gas-liquid two-phase refrigerant, flows into the indoor heat exchanger 3, and is sent to the indoor heat exchanger 3 by the indoor fan 6. It heat-exchanges with air to be vaporized and gasified, and flows out from the indoor heat exchanger 3. The evaporatively gasified refrigerant returns to the compressor 1 through the gas connection pipe 50 and the four-way valve 2, and is compressed again by the compressor 1 to form a refrigeration cycle.

FIG. 2 shows a refrigeration cycle Mollier diagram, in which point a shows the state of discharge from the compressor 1,
The discharge pressure, which is that pressure, is Pd. Point b shows the state of the outdoor heat exchanger 4 outlet, that is, the condenser outlet, and point c shows the state of the indoor heat exchanger 3 inlet that has been decompressed by the indoor expansion valve 7, that is, the evaporator inlet. A point d shows the state of being sucked into the compressor 1, and the suction pressure which is the pressure is Ps. The operating pressure ratio ε during the cooling operation is the ratio between the discharge pressure Pd and the suction pressure Ps.

As the operable range of the compressor, the operating pressure ratio ε
Is λ1 (eg, 1.8) <ε <λ2 (eg, 8.
0) is desirable, and the operating pressure ratio ε is λ1 or less, or λ
If it is 2 or more, the operating life of the compressor is extremely reduced, and there is a risk of early failure. Therefore, the compressor frequency, the indoor / outdoor fan and the indoor / outdoor expansion valve opening are controlled so that the operating pressure ratio ε is between λ1 and λ2, and the reliability of the compressor is ensured. That is, when the operating pressure ratio ε <λ1, the lower limit value of the compressor frequency is set higher than that during normal control,
The air volume of the outdoor fan is reduced in the cooling operation, and the air volume of the indoor fan is increased in the heating operation. When the operating pressure ratio ε> λ2, the upper limit of the compressor frequency is set lower than in the normal control, the air volume of the outdoor fan is increased during the cooling operation, and the outdoor fan is increased during the heating operation. The air volume is reduced, or the opening of the indoor expansion valve is opened to allow the receiver or the like to recover the refrigerant in the heat exchanger functioning as a condenser.

Next, a method of estimating the operating pressure ratio during the cooling operation will be described. The estimation of the operating pressure ratio is performed by the microcomputer 20 using the temperature sensors 21 and 22 provided in the indoor heat exchanger 3 and the outdoor heat exchanger 4 and the motor rotation speed signal of the compressor 1. The operating pressure ratio ε is determined by the outdoor heat exchanger 4
It is the ratio of the discharge pressure Pd estimated from the detection value Tc of the temperature sensor 21 provided in the indoor heat exchanger 3 to the suction pressure Ps estimated from the detection value Te of the temperature sensor 22 provided in the indoor heat exchanger 3.

[0015]

[Equation 1]

The estimated discharge pressure Pd is {α of the base e of the natural logarithm.
2 * (Tc + α3)} power, and the estimated suction pressure Ps is proportional to the bottom e of {β2 × (Te + F1 + L1)} power.

[0017]

[Equation 2]

[0018]

[Equation 3]

Tc is the saturation pressure on the discharge side, Te is the saturation pressure on the suction side, and α1 to α3, β1 and β2 are coefficients that vary depending on the type of refrigerant enclosed in the air conditioner. F1 is a correction value based on the motor speed Hz, and L1
Is a correction coefficient depending on the length of the connecting pipe connecting the condenser and the evaporator or the outdoor unit and the indoor unit. It is assumed that F1 is proportional to the detected value Hz of the motor rotation speed of the compressor 1 and γ2 is added as shown in Formula 4.

[0020]

[Equation 4]

L1 varies depending on the length of the pipe connecting the indoor unit 200 and the outdoor unit 100, and is input to the microcomputer 20 in advance, or is input from an external signal such as a DIP switch or communication.

Explaining with the Mollier diagram shown in FIG. 2, the saturation pressure Tc is obtained by the temperature sensor 21 provided in the outdoor heat exchanger 4, and the estimated discharge pressure Pd is obtained by obtaining Tc by Equation 2. The estimated Pd is slightly lower than the actual discharge pressure Pd due to the pressure loss of the four-way valve 2 and the outdoor heat exchanger 4 and the refrigerant supercooling degree of the condenser, but the refrigerant state is high in temperature and pressure and the density is large. Since the pressure loss is small and the distance to the temperature sensor does not change, the estimated Pd and the actual Pd can be adjusted by adjusting the coefficient of Equation 1.
Can be the same value.

On the other hand, the temperature sensor 22 provided in the indoor heat exchanger 3 determines the saturation pressure Te on the suction side. The saturation pressure Te is determined by the indoor heat exchanger 3 and the gas connection pipe 5
Since there is a pressure loss at 0 or the like, it becomes higher than the suction pressure Ps. Since this pressure loss changes depending on the length of the gas side connecting pipe 50 and the amount of circulation of the refrigerant flowing through the refrigeration cycle, it is corrected as shown in Formula 4. That is, since the circulation amount of the refrigerant flowing through the refrigeration cycle is proportional to the motor rotation speed Hz of the compressor 1, the estimated suction pressure Ps is a correction coefficient L1 depending on the connection pipe length and the correction value F1 depending on the motor rotation speed Hz of the compressor 1. Ask by.

In the heating operation, the high-temperature and high-pressure gas refrigerant compressed by the compressor 1 flows into the indoor heat exchanger 3 through the four-way valve 2 and the gas side connecting pipe 50, and the indoor fan 6 heats the indoor heat exchanger. The heat is exchanged with the air sent to the air conditioning unit 3 to condense and liquefy and flow out from the indoor heat exchanger 3. The condensed and liquefied refrigerant is decompressed by the indoor expansion valve 7, becomes a gas-liquid two-phase refrigerant, flows into the outdoor heat exchanger 4 through the liquid side connection pipe 51, and is sent to the outdoor heat exchanger 4 by the outdoor fan 5. It exchanges heat with air to be vaporized and gasified, and flows out from the outdoor heat exchanger 4. The evaporated gasified refrigerant returns to the compressor 1 through the four-way valve 2 and is compressed by the compressor 1 again to form a refrigeration cycle.

The refrigeration cycle of the heating operation is shown in the Mollier diagram as shown in FIG. 2 like the cooling operation, and the operating pressure ratio during the heating operation can be obtained in the same manner as during the cooling operation.
Further, the estimation of the operating pressure ratio during the heating operation is performed using the equations 1 to 4 as in the cooling operation. However, T in the formula
c is a detection value of the temperature sensor 22 provided in the indoor heat exchanger 3,
Te is a detection value of the temperature sensor 21 provided in the outdoor heat exchanger 4.

As described above, the operating pressure ratio of the air conditioner can be estimated by detecting the condenser outlet temperature and the evaporator inlet temperature, and the operating pressure ratio can be estimated without using an expensive pressure sensor. It can be detected and reliability can be improved. Also,
Since the discharge pressure and suction pressure are estimated by the temperature sensor (thermistor), the saturation temperature of the discharge gas can be estimated from the discharge pressure estimated value. Therefore, the discharge gas superheat degree is estimated by detecting the discharge temperature. It is possible to control the discharge gas superheat degree with the expansion valve. further,
Since the estimated value of the suction pressure can be used to control the refrigeration cycle control device so as to prevent the vacuum operation of the compressor, the reliability of the compressor can be further improved.

Next, another embodiment of the present invention will be described with reference to FIG.
This will be described with reference to Nos. 4 to 4. FIG. 3 shows a refrigeration cycle of an air conditioner equipped with a refrigerant supercooling degree control device for a condenser. The refrigeration cycle includes an indoor expansion valve 7 and an outdoor heat exchanger 4.
The liquid receiver 9 and the outdoor expansion valve 8 are arranged between them.

The receiver 9 stores excess refrigerant, and the outdoor expansion valve 8 is fully opened during the cooling operation, that is, the opening is increased so as to reduce the pressure loss in the expansion valve. The temperature of the refrigerating cycle is controlled by the valve 7, the indoor expansion valve 7 is fully opened during the heating operation, and the temperature of the refrigerating cycle is controlled by the outdoor expansion valve 8. The operation of the refrigeration cycle is shown in the Mollier diagram as shown in FIG. That is, since the expansion valve provided at the outlet of the heat exchanger acting as the condenser is fully opened and used, the degree of supercooling of the condenser refrigerant becomes 0, and the saturation of Tc detected by the temperature sensor at the condenser outlet is reached. The pressure has the same value as the discharge pressure Pd. Therefore, the estimated value of the discharge pressure Pd is obtained by providing the liquid receiver 9 and fully opening the expansion valve provided at the outlet of the heat exchanger functioning as the condenser to control the degree of supercooling of the refrigerant in the condenser. The accuracy can be improved, the operating pressure ratio of the air conditioner can be made more accurate, and the reliability can be improved.

[0029]

As described above, according to the present invention,
By detecting the operating pressure ratio without using an expensive pressure sensor, the manufacturing cost of the air conditioner can be significantly reduced, and the reliability can be improved.

[Brief description of drawings]

FIG. 1 is a refrigeration cycle of an air conditioner showing an embodiment of the present invention.

FIG. 2 is a Mollier diagram showing an operating state of the refrigeration cycle of FIG.

FIG. 3 is a refrigeration cycle for an air conditioner according to another embodiment.

FIG. 4 is a Mollier diagram showing an operating state of the refrigeration cycle in FIG.

[Explanation of symbols]

1 ... Compressor, 3 ... Indoor heat exchanger, 4 ... Outdoor heat exchanger, 7
... indoor expansion valve, 8 ... outdoor expansion valve, 9 ... liquid receiver, 20 ... microcomputers 21,22 ... temperature sensor, 50 ...
Gas side connection pipe, 51 ... Liquid side connection pipe, 100 ... Outdoor unit, 200 ... Indoor unit.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masayuki Okabe             Hitachi, Ltd. 390 Muramatsu, Shimizu City, Shizuoka Prefecture             Air conditioning system Shimizu Production Headquarters (72) Inventor Fukuji Tsukada             Hitachi, Ltd. 390 Muramatsu, Shimizu City, Shizuoka Prefecture             Air conditioning system Shimizu Production Headquarters F-term (reference) 3L060 AA08 CC04 DD02 EE02

Claims (5)

[Claims] 1. An air conditioner, in which a compressor, a condenser, a decompression device, and an evaporator are connected by piping to form a refrigeration cycle, and an evaporator inlet temperature and a condenser outlet temperature are detected, and the evaporator inlet temperature is detected. From the suction pressure of the compressor and the discharge pressure of the compressor from the outlet temperature of the condenser to obtain an operating pressure ratio, which is the ratio of the discharge pressure of the compressor to the suction pressure. Harmony machine. 2. The air conditioner according to claim 1, wherein the suction pressure is obtained in relation to an operating frequency of the compressor and a length of a pipe connecting the condenser and the evaporator. Machine. 3. The expansion valve according to claim 1, wherein an expansion valve having a variable opening degree is provided on the outlet side of the condenser, and a receiver for storing excess refrigerant is provided at the outlet of the expansion valve. An air conditioner, which is fully opened to obtain the operating pressure ratio. 4. The suction pressure according to claim 1, wherein the suction pressure is a saturation pressure on the suction side, a value proportional to a motor rotation speed of the compressor, and a coefficient is added to the suction pressure, the condenser and the evaporator. An air conditioner characterized by being obtained in relation to a power of a value that is the sum of the lengths of the pipes connecting the. 5. The air conditioner according to claim 1, wherein the operating frequency of the compressor is controlled so that the obtained operating pressure ratio falls within a predetermined range.