JPS63290354A - Heat pump type air conditioner - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a heat pump type air conditioner that employs an electric expansion valve as a refrigerant flow rate control device.

Conventional technology In recent years, heat pump type air conditioners have been developed using variable frequency power sources to drive the compressor and determine the optimal refrigerant flow rate according to the operating conditions, depending on the size of the air conditioning load. An electric expansion valve is used as the refrigerant control device.

FIG. 4 shows a cooling system diagram of a conventional heat pump type air conditioner. In FIG. 4, 1 is a compressor driven by a variable frequency power source 12. In FIG. 2 is a four-way valve that switches between cooling and heating cycles. 3 is an outdoor heat exchanger, 4 is an electric expansion valve on the outdoor side, 6.6' is an electric expansion valve on the indoor side, and 7°7' is an indoor heat exchanger.These are connected in a ring to form a refrigeration cycle. It consists of The electric expansion valve 4 on the outdoor side determines the opening degree by calculating the difference in temperature between the temperature sensors 20 and 210 provided at the intermediate part and the outlet part of the outdoor heat exchanger 3 with the controller 3o during heating operation, Performs refrigerant flow control. The electric expansion valve 6, 6' on the indoor side controls the temperature difference between the temperature sensors 22, 23 and 22', 23' provided at the intermediate part and the outlet part of the indoor heat exchangers 7, 7' to the controller 31 during cooling operation. The opening degree is determined by calculating .31', and the refrigerant flow rate is controlled. 9.9' is a check valve, 10.10' is a solenoid valve, and the check valve 9.9' and the solenoid valves 10 and 10' are connected in parallel.

11 is an accumulator. Reference numeral 12 is a variable frequency power supply, which changes the frequency according to the size of the air conditioning load.
Drive the compressor.

The operation of the air conditioner configured as above will be described below.

First, the cooling time will be explained. During cooling, high-temperature, high-pressure refrigerant gas compressed by the compressor 1 passes through the four-way valve 2 and is liquefied in the outdoor heat exchanger 3. During cooling, the outdoor electric expansion valve 4 is fully opened and no throttling is applied to the indoor unit.
High pressure liquid refrigerant enters. Furthermore, the electric expansion valve 6.6' on the indoor side
The controller 31, 31' calculates the difference between the pipe temperature at the middle part of the indoor heat exchanger 7°7' and the pipe temperature at the outlet part to determine the opening degree and apply a restriction to the refrigerant. Low-temperature, low-pressure gas-liquid two-phase refrigerant, indoor heat exchanger 7
．． It evaporates into gas at 7' and reaches the accumulator 11.
Return to compressor 1 and repeat the cycle.

Next, a method of controlling the refrigerant flow rate using the electric expansion valve 6 will be explained. The temperature difference measuring means 31a determines the temperature difference from the temperature sensors 22, 23 provided at the intermediate part and the outlet part of the indoor heat exchanger 7, and based on the temperature difference, the electric expansion valve opening determining means 31b controls the valve. The opening degree is determined, and based on the determination, the electric expansion valve control means 31c controls the electric expansion valve 6 to adjust and set the valve opening degree.

Control.

Note that the method of controlling the refrigerant flow rate using the electric expansion valve 6' is also the same as the method of controlling the refrigerant flow rate using the electric expansion valve 6.

Next, heating will be explained. During heating, high-temperature, high-pressure refrigerant gas compressed by the compressor 1 passes through the four-way valve 2 and is liquefied in the indoor heat exchanger 7.7'. During heating, electric expansion valve 6.6
' is fully opened and high pressure liquid refrigerant enters the outdoor unit. Furthermore, the electric expansion valve 4 on the indoor side determines the opening degree by calculating the difference between the piping temperature at the intermediate part of the outdoor heat exchanger 3 and the piping temperature at the outlet part by the controller 3o, and applies a restriction to the refrigerant. For,
The refrigerant becomes a low-temperature, low-pressure gas-liquid two-phase refrigerant, which is evaporated into gas in the outdoor heat exchanger 3, transferred to the accumulator 11, and returned to the compressor 1, repeating the cycle.

Next, a method of controlling the refrigerant flow rate using the electric expansion valve 4 will be explained. By detecting the temperature of the piping between the intermediate section and the outlet section of the outdoor heat exchanger 3 with the temperature sensor 20.21, the electric expansion valve is controlled in the same way as the controller 31 of the indoor unit according to the difference in temperature. Control 4.

Problems to be Solved by the Invention However, with the above configuration, as is clear from Figure 4, if the maximum practical capacity is to be achieved during normal heating and cooling operation, the refrigerant in the evaporator will be Since it is a phase flow, the pipe temperature at the middle part is slightly higher than the pipe temperature at the outlet part due to pressure loss.Furthermore, this temperature difference is almost negligible, and the amount of change is also small. Because of their small size, it is difficult to accurately detect them, and at the same time, the control becomes complicated and takes a long processing time. In addition, the temperature of the pipe at the outlet of the evaporator is sufficiently higher than that of the pipe at the middle of the evaporator, and the electric expansion valve is throttled to the extent that it is possible to detect the difference in temperature. The problem is that the degree of superheating on the suction side of the compressor increases and the amount of refrigerant circulated also decreases, resulting in a decrease in capacity.

In view of the above problems, the present invention provides a heat pump type air conditioner that prevents phenomena such as hunting and maintains a stable refrigeration cycle state.

Means for Solving the Problems In order to achieve the above object, the heat pump type air conditioner of the present invention has an electric expansion valve provided between an indoor heat exchanger and an outdoor heat exchanger, which is normally connected to a compressor. The opening degree is determined by detecting the operating frequency of the evaporator, and during overload operation of heating and cooling when indoor and outdoor air temperatures rise, the system calculates the difference between the pipe temperature at the middle part of the heat exchanger that serves as the evaporator and the pipe temperature at the outlet part. The system is equipped with superheat degree control means for determining the degree of opening of the electric expansion valve.

Effects The present invention has the above-described configuration, so that during normal heating and cooling operation, the compressor operating frequency is detected and the electric expansion valve opening degree is determined. In some cases, the frequency detection is accurate and quick, so the electric expansion valve immediately sets the optimal throttling amount at that time, and phenomena such as hunting do not occur, and the entire cooling system can be quickly maintained in a stable state. becomes.

In addition, during overloaded heating and cooling operations when indoor and outdoor air temperatures rise, the control method is switched to calculate the difference between the pipe temperature at the middle part of the heat exchanger that serves as the evaporator and the pipe temperature at the outlet part, and open the electric expansion valve. Since the electric expansion valve opening is larger than during normal operation, the refrigerant flow rate is increased, which prevents a rise in discharge temperature and improves the reliability of the compressor. .

EXAMPLE Hereinafter, a heat pump type air conditioner according to an example of the present invention will be described with reference to the drawings. FIG. 1 shows a cooling system diagram of a heat pump type air conditioner according to an embodiment of the present invention, and in particular, points different from the conventional example will be explained. In FIG. 1, 4, 6.6' are electric expansion valves, and 6° 8.8' are respective controllers.

The controller 5°, the controller 8, and the controller 8' are connected to a variable frequency power source 12 by a signal line.

The operation of the heat pump type air conditioner configured as above will be explained below with reference to FIGS. 1, 2, and 3.

First, referring to FIG. 2, the control of the dynamic expansion valves 4, 6, 6' will be explained. Since the electric expansion valve control is the same during each cooling/heating operation, the control of the indoor electric expansion valve 6 during cooling will be explained. During normal cooling operation, the operating frequency is detected by the operating frequency detecting means 8b from the variable frequency power supply 12, the electric expansion valve opening determining means 8C determines the opening of the electric expansion valve 6, and Based on this, the electric expansion valve control means 8d controls the valve opening degree. During cooling overload when the indoor and outdoor air temperatures rise, the difference in temperature between the temperature sensors 22 and 23 provided at the intermediate portion and the outlet portion of the indoor heat exchanger 7 increases. When the temperature difference measuring means 8a is larger than the set upper limit value of the temperature difference, the electric expansion valve opening degree determining means 8C determines the valve opening degree based on the temperature difference, and the electric expansion valve control means 8C determines the valve opening degree based on the temperature difference. 8d, the valve opening degree of the electric expansion valve 6 is controlled.

Next, from Fig. 3, electric expansion valve 6.6 due to load fluctuation.
′ will be explained in more detail.

During normal cooling operation (o(T, (t'')), the controller 8.8' detects the operating frequency of the compressor 1 and determines the opening degree of the electric expansion valves 6, 6'. If there is a load change and the operating frequency of the compressor 1 changes, the electric expansion valve opening degree will also change accordingly.Therefore, in this case, regardless of the number of indoor units in operation, the compressor 1 The opening degree of the electric expansion valve 6,6' is determined only by the operating frequency.However, in this case, the electric expansion valve 4 is fully open.During normal heating operation, as well as during normal cooling operation, ,
A controller 6 detects the operating frequency of the compressor 1 and determines the opening degree of the electric expansion valve 4. In this case electric expansion valves 6 and 6'
is at full throttle. Next, a case of cooling overload when the indoor and outdoor air temperature rises will be explained. During cooling overload (t>T,
), when the difference in temperature between the pipe temperature at the middle part of the evaporator and the pipe temperature at the outlet part exceeds a certain value, the temperature difference during normal cooling operation (0
<t<71), the control method of the electric expansion valve 6.6' is changed, and the temperature difference between the pipe temperature at the middle part and the pipe temperature at the outlet part of the indoor heat exchanger 7°7', which is the evaporator, is changed. The controllers 8, 8' calculate the opening degrees of the electric expansion valves 6, 6' based on the calculations. However, in this case as well, the electric expansion valve 4 is fully open. During a heating overload, as well as during a cooling overload, if the difference in temperature between the pipe temperature at the middle part of the outdoor heat exchanger 3, which serves as an evaporator, and the pipe temperature at the outlet part exceeds a certain value, normal heating is resumed. When driving (0<
The control method for the electric expansion valve 4 is switched from t<T1), the controller 6 calculates this temperature difference, and determines the opening degree of the electric expansion valve 4 based on it. However, in this case as well, the electric expansion valve 6.6' is fully open. As described above, according to this embodiment, during normal cooling/heating operation, the compressor operating frequency is detected and the electric expansion valve opening degree is determined, so when there is a load fluctuation and the compressor operating frequency changes. Since the optimum throttling amount at that time is immediately set by the electric expansion valve, phenomena such as hunting do not occur, and the entire cooling system can be quickly maintained in a stable state. In addition, during heating and cooling overload when indoor and outdoor air temperatures rise,
The degree of superheating at the outlet of the heat exchanger that serves as an evaporator is large, and the discharge temperature also increases. The opening degree of the electric expansion valve is determined by calculating the difference between the piping temperature of
By increasing the refrigerant flow rate, it is possible to prevent an increase in discharge temperature and improve the reliability of the compressor.

In addition, in this example, an overload state of heating and cooling is detected when the temperature difference between the piping temperature at the middle part of the evaporator and the piping temperature at the outlet part exceeds a certain value, but this is due to the discharge temperature. , the discharge pressure and the outside temperature may be used for detection.

Effects of the Invention As described above, the present invention detects the compressor operating frequency and determines the opening degree of the electric expansion valve during normal heating and cooling operation. Even when the amount of throttle changes, the electric expansion valve immediately sets the optimal throttling amount at that time, so phenomena such as hunting do not occur, and the entire cooling system can be quickly maintained in a stable state. 'Also, during overloaded heating and cooling operations when the indoor and outdoor air temperatures rise, the control method is switched to calculate the difference between the pipe temperature at the middle section of the heat exchanger that serves as the evaporator and the pipe temperature at the outlet section, and control the electric expansion valve. Since the opening degree is determined, the electric expansion valve opening degree becomes larger than during normal operation, and the refrigerant flow rate increases, thereby preventing a rise in discharge temperature and improving the reliability of the compressor.

[Brief explanation of the drawing]

Fig. 1 is a diagram of the cooling system of a heat pump air conditioner according to an embodiment of the present invention, Fig. 2 is a block diagram of the controller, and Fig. 3 is a diagram of the electric expansion valve control method of the heat pump air conditioner. Figure 4 is a diagram of the cooling system of a conventional heat pump air conditioner, Figure 6 is a block diagram of the controller, and Figure 6 shows the relationship between the electric expansion valve opening, evaporator piping temperature, and capacity. This is a diagram. 1...Compressor, 3...Outdoor heat exchanger,
4...Electric expansion valve, 5...Controller, 6
...Electric expansion valve, 6'...Electric expansion valve, 7...Indoor heat exchanger, 7'...Indoor heat exchanger, 8... ...Controller, 8'...Controller. Name of agent: Patent attorney Toshio Nakao and 1 other person1-
m=compressor 3-11 outdoor exchanger 4- electric expansion valve 5--1'' unit 6, 6'- @ dynamic expansion valve 77--11 chamber exchanger 8, 8'- - Anatomy # quantity Fig. 1 6 - Electric tension valve 8 - Controller 12 - - Variable waste wave number electric field 22, 23 - - Temperature fluctuation sensor Fig. 2 Fig. 4 Fig. 5

Claims (1)

[Claims] In a refrigerant circuit configured by connecting a compressor, an indoor heat exchanger, an outdoor heat exchanger, etc. in an annular manner driven by a variable frequency power source, there is a refrigerant circuit between the indoor heat exchanger and the outdoor heat exchanger. Normally, the operating frequency of the compressor is detected to determine the opening degree of the electric expansion valve, and during overload heating and cooling operation when indoor and outdoor air temperatures rise, the heat exchanger acts as an evaporator. 1. A heat pump type air conditioner, comprising: a degree of superheat control means that calculates a difference between a piping temperature at an intermediate portion of the container and a piping temperature at an outlet portion to determine the degree of opening of the electric expansion valve.