JPH0718599B2 - Air conditioner - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an air conditioner having an electric expansion valve as an expansion mechanism in a refrigerant pipe connecting an indoor heat exchanger and an outdoor heat exchanger. is there.

(Prior Art) Conventionally, in an air conditioner of a medium / large size or a large load fluctuation, an expansion valve is provided as an expansion mechanism in a refrigerant pipe connecting a condenser and an evaporator. Cage,
Thus, the flow rate of the refrigerant is adjusted according to the load change. In recent years, many devices have been provided with an electrically driven expansion valve, and the device is configured as a device with improved reliability by an electric control means. The opening degree control of such an electric expansion valve is generally performed by a superheat control method, and a specific example thereof is described in JP-A-60-133269, and FIG. The refrigerant circuit is shown schematically. As shown in the figure, this device is a separate type air conditioner composed of an outdoor unit A and an indoor unit B, and a compressor 31 provided in the outdoor unit A is connected to a four-way switching valve 32 and One connection port of the path switching valve 32 is connected to the outdoor heat exchanger 33, and the other connection port is connected to the indoor heat exchanger 34 provided in the indoor unit B.
5, connected by the second gas pipe 36. The outdoor heat exchanger 33 and the indoor heat exchanger 34 are connected by a liquid pipe 37 to form a refrigerant circulation circuit, and an electric expansion valve 38 is interposed in the liquid pipe 37. In addition, 39 is a liquid receiver installed in the liquid pipe 37, and the suction port of the compressor 31 and the four-way switching valve.
An accumulator 41 is interposed in the suction pipe 40 connecting with 32. In addition to the above refrigerant circulation circuit,
In order to control the opening degree of the electric expansion valve 38, the liquid pipe 37 and the suction pipe 40 are connected by an injection pipe 43 interposed between the capillary tubes 42, and the suction pipe 40 side from the capillary tube 42 is connected. The injection pipe 43 has a thermistor 44 for measuring the evaporation pressure saturation temperature, the second gas pipe 36 has a thermistor 45 for measuring the evaporator outlet temperature during cooling, and the suction pipe 40 has the evaporator outlet temperature during heating. A measurement thermistor 46 is attached to each.

In the device configured as described above, the opening degree control of the electric expansion valve 38 is performed as follows. For example, during cooling operation,
When the refrigerant is circulated in the direction of the solid line arrow in the figure, the indoor heat exchanger 34 acts as an evaporator, and the outlet gas temperature of the indoor heat exchanger 34 is measured by the thermistor 45 attached to the second gas pipe 36. , Meanwhile, the liquid pipe 37 through the injection pipe 43
The temperature of the refrigerant that is more bypassed and evaporates when passing through the capillary tube 42 depends on the injection pipe 43.
It is measured as the evaporation pressure equivalent saturation temperature by the thermistor 44 attached to, the temperature difference between the two measured values is taken as the degree of superheat, and in order to maintain this at the measured value, the opening degree of the electric expansion valve 38 is controlled. . On the other hand, during the heating operation, the refrigerant circulates in the direction of the broken arrow in the figure, and since the outdoor heat exchanger 33 acts as an evaporator at this time, the temperature measured by the thermistor 44 attached to the injection pipe 43, Suction pipe 40
The degree of superheat is obtained from the difference between the temperature measured by the thermistor 46 attached to the motor, and the opening degree of the electric expansion valve 38 is controlled in the same manner as above.

(Problems to be Solved by the Invention) As described above, in order to control the refrigerant flow rate by the electric expansion valve according to the load fluctuation, the injection pipe 43 provided via the capillary tube 42 is provided exclusively. In addition, a temperature measurement sensor such as a thermistor for temperature measurement is required, and thus an apparatus using an electric expansion valve is expensive. Further, since the refrigerant is bypassed from the liquid pipe 37 through the injection pipe 43, the refrigerating capacity is also lowered.

On the other hand, as an example of using an electric expansion valve without depending on the superheat control method as described above, there is a multi-type air conditioner in which a plurality of indoor units are connected to one outdoor unit. However, the opening degree corresponding to the change in the number of operating rooms is set in advance, and the refrigerant flow rate is switched step by step according to the operating room, and it is possible to cope with the load fluctuation in each room. Absent. Therefore, although it can be constructed at a low cost, the refrigerating capacity is not sufficiently exerted because the opening is not the optimum opening in consideration of load fluctuation in each room.

The present invention has been made to solve the above-mentioned conventional problems, does not require a special temperature measurement detection circuit, etc., and enables the opening control of the electric expansion valve corresponding to the load fluctuation. It is to provide a simplified air conditioner.

(Means for Solving Problems) Therefore, in the air conditioner of the present invention, the compressor 1, the indoor heat exchanger 6, and the outdoor heat exchanger 4 are connected so that refrigerant can circulate, and the indoor heat exchanger 6 is connected. Pipe 12 that connects the heat exchanger 4 and the outdoor heat exchanger 4
An air conditioner having a motor-operated expansion valve 13 interposed therein, which is provided with a first temperature detecting means 14 for detecting the temperature inside the room and a second temperature detecting means 15 for detecting the temperature outside the room. The control means 16 is provided for controlling the opening degree of the electric expansion valve 13 based on the temperature difference between the first and second temperature detecting means 14 and 15, and the control means 16 detects the temperature difference. As the absolute value of the electric expansion valve 13 increases, the opening degree of the electric expansion valve 13 is reduced, and for the same absolute value of the detected temperature difference, the opening degree of the electric expansion valve 13 is reduced together with the decrease in the outdoor temperature during the cooling operation. On the other hand, during the heating operation, control is performed such that the opening degree of the electric expansion valve 13 is reduced as the outdoor temperature rises.

(Operation) In the air conditioner of the present invention configured as described above, the control means 16 obtains a signal corresponding to the indoor load to be temperature-controlled by the difference between the indoor temperature and the outdoor temperature. Thus, the opening degree of the electric expansion valve 13 is controlled by obtaining an appropriate opening degree from the above signal. At this time, a special detection circuit such as injection piping in the conventional superheat control method is not required, and the first temperature detecting means 14 for detecting the indoor temperature is, for example, an indoor thermistor of a room thermostat for controlling the indoor temperature. Further, as the second temperature detecting means 15 for detecting the outdoor temperature, for example, an outdoor thermistor for defrost control provided in the outdoor heat exchanger 4 can be diverted and used. For controlling the opening of the electric expansion valve 13 that responds to load fluctuations,
Since no special equipment is required, it can be constructed at low cost. Further, unlike the conventional superheat control method, it is not necessary to bypass the refrigerant, and this can improve the cooling and heating capacity.

(Examples) Next, specific examples of the air conditioner of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a refrigerant circuit diagram of an apparatus configured as a separate type air conditioner. In the figure, this apparatus is composed of an outdoor unit X and an indoor unit Y, and the outdoor unit X is a compressor 1. Four-way switching valve 2 and outdoor fan 3
Of the indoor heat exchanger 6 to which the indoor fan 5 is attached.
have. The compressor 1 and the four-way switching valve 2 are connected by a discharge pipe 7 and a suction pipe 9 provided with an accumulator 8, and one connection port of the four-way switching valve 2 is a first port. Outdoor heat exchanger 4 by gas pipe 10
It is connected to the. Further, the other connection port of the four-way switching valve 2 is connected by the second gas pipe 11 and the outdoor heat exchanger 4
Are connected to the indoor heat exchanger 6 by liquid tubes 12 to form a refrigerant circulation circuit. Then, the liquid pipe 12
A motor-operated expansion valve 13 is installed in the. Further, the indoor unit Y is provided with an indoor thermistor 14 for detecting the indoor temperature in order to adjust the room temperature. On the other hand, in the outdoor heat exchanger 4, when performing indoor heating operation at low outdoor temperature,
Although frost may adhere to the outdoor heat exchanger 4, in order to control the defrost operation operation for removing this frost,
An thermistor for measuring the outside air temperature (hereinafter referred to as the outside air thermistor) 15 is attached. The indoor thermistor 14 and the outside air thermistor 15 also serve as first and second temperature detecting means also used for controlling the opening degree of the electric expansion valve 13, and the detected temperature signals of the indoor expansion thermistor 15 and the outside expansion thermistor 15, respectively. It is input to the control means 16 which is the control means for controlling the opening degree of the valve 13. The electric expansion valve 13 is of a type driven by a pulse motor, and from the control device 16,
A pulse train corresponding to the set opening is output to the electric expansion valve 13 as a control signal. On the other hand, the indoor fan 5 attached to the indoor heat exchanger 6 has a fan tap (not shown) capable of switching the amount of air blown, and the compressor 1 has its rotation speed. That is, it has an inverter 17 for controlling the compression capacity. The fan tap switching position signal and the inverter frequency signal are further input to the control device 16.

In the device configured as described above, the indoor cooling operation is performed by driving the compressor 1 and circulating the refrigerant in the direction of the solid line arrow in the figure by switching the four-way switching valve 2, while the refrigerant is cooled in the direction of the broken line arrow. Heating operation is performed by circulating.

In the refrigeration cycle in which the refrigerant is circulated for cooling or heating as described above, for example, during cooling operation, the sum of the compression work amount of the compressor 1 and the heat amount absorbed from the outside in the indoor heat exchanger 6 is the outdoor heat. The refrigerant is circulated in a state of being balanced with the external heat radiation amount in the exchanger 4. Here, when the temperature of the indoor air blown to the indoor heat exchanger 6 gradually decreases, and thus the amount of heat exchange (absorption heat amount) with the blown air in the indoor heat exchanger 6 decreases, the above heat amount The balance is lost, for example, the circulating liquid refrigerant cannot be completely evaporated and is returned to the compressor 1 to perform a wet operation, which makes it impossible to maintain an effective refrigeration cycle. Therefore, at this time, it is necessary to reduce the amount of circulating refrigerant to restore the heat balance. As described above, in order to operate the refrigeration cycle efficiently, the indoor heat exchange amount of the indoor heat exchanger 6 with the indoor blown air and the heat amount balance of the outdoor heat exchanger 4 with the outdoor heat exchanger are balanced. It is necessary to adjust the refrigerant flow rate to be maintained. By the way, if the outside air temperature is obtained, the relationship between the refrigerant flow rate and the outdoor heat exchange amount is obtained, and if the temperature of the air blown to the indoor heat exchanger 6 is obtained, the relationship between the refrigerant flow amount and the indoor heat exchange amount is obtained. If the outside air temperature and the indoor temperature are respectively roughly obtained, and therefore the outside air temperature and the indoor temperature are obtained, an appropriate refrigerant flow rate that balances the amounts of the outdoor heat exchange and the indoor heat exchange can be set substantially. Furthermore, it is possible to obtain the correlation between this parameter and the proper refrigerant flow rate by setting the difference between the outside air temperature and the indoor temperature as a parameter that substantially corresponds to the refrigeration load.

Therefore, in the air conditioner, in order to control the opening degree of the electric expansion valve 13, the indoor temperature during operation and the outdoor temperature are detected, and the opening degree is controlled by the detected temperature. Then, this control method will be described below.

FIG. 1 is a block diagram of the opening control function of the electric expansion valve. In FIG. 1, the indoor detected temperature signal from the indoor thermistor 14 serving as the first temperature detecting means for detecting the temperature of the outdoor side and the outdoor side. The outside air temperature detection temperature signal from the outside air thermistor 15 which serves as the second temperature detecting means for detecting the temperature is input to the control device 16 which serves as the control means for controlling the opening degree of the electric expansion valve 13. Furthermore, a switching position signal of a fan tap that switches the blow rate of the indoor fan 5 that has a great influence on the indoor heat exchange amount between H (strong wind) and L (weak wind), and the compression work of the compressor 1 in the heat balance. The frequency signal of the inverter frequency that influences the quantity is input to the control device 16. This control device 16 is composed of an input unit 20, a calculation unit 21, a condition data storage unit 22 and an output unit 23, and the input signals are first subjected to signal processing such as A / D conversion in the input unit 20. And is transferred to the calculation unit 21. The calculation unit 21 obtains the difference between the indoor temperature and the outside air temperature, and from the result,
The proper opening value stored in the condition data storage unit 22 described later is obtained, and the correction coefficient is obtained from the condition data storage unit 22 from the fan tap signal and the inverter frequency signal, and the previous proper opening value is corrected. Calculate Then, based on the result of this calculation, an output pulse train corresponding to the value is generated in the output unit 23, this is given to the electric expansion valve 13, and the valve opening degree is set.

FIGS. 3 to 6 schematically show tables for creating the data table stored in the condition data storage unit 22. In FIG. 3, the horizontal axis indicates the outside air temperature and the indoor temperature. The absolute value of the difference ΔT, the valve opening of the electric expansion valve on the vertical axis,
It is a graph which calculates | requires the appropriate valve opening degree at the time of air_conditionaing | cooling operation using the said outside air temperature as a parameter. And, FIG. 4 is a graph showing the same relationship as in FIG. 3 during the heating operation. As shown in FIG. 3, during cooling operation, the valve opening is decreased as the absolute value ΔT of the temperature difference increases, and when the absolute value ΔT of the temperature difference is constant, the valve opening is decreased as the outside air temperature decreases. I am trying to reduce it. Further, as shown in FIG. 4, during the heating operation, the valve opening degree is decreased as the absolute value ΔT of the temperature difference increases, and when the absolute value ΔT of the temperature difference is constant, the valve opening degree increases as the outside air temperature increases. I am trying to reduce. Fig. 5 shows the heating operation
The relationship between the outside air temperature and the correction coefficient C1 when the fan tap is H (strong wind) and L (weak wind), and FIG. 6 shows the relationship between the outside air temperature and the correction coefficient C2 when the inverter frequency is changed. From the above graphs, for example, during the heating operation, the final valve opening is determined by multiplying the valve opening obtained in FIG. 4 by the correction factors C1 and C2 obtained in FIGS. 5 and 6, respectively. is there. The graph of the correction coefficient during the cooling operation is also not shown in the figure, but similarly obtained in advance, and the appropriate valve opening degree and the correction coefficient value under each condition are used as a data table as a condition from the above graphs. It is stored in the data storage unit 22.

Next, to explain based on the control flowchart of FIG. 7, when the air conditioner is started, first, a start-up process is executed. During this period, the number of revolutions of the compressor 1 is suppressed to release the refrigerant dissolved in the oil and improve the lubricity. During this period, as shown in Step S1 and Step S2 of FIG. 7, During this startup period T1, the electric expansion valve 13
A signal for fixing the valve opening degree of is fixed to the initial setting value is output. Then, after the passage of T1, from step S2 to step S3,
The valve opening automatic control for returning from step S3, S4, S5 to step S3 is performed. That is, in step S3, the input signal such as the indoor temperature and the outside air temperature is received and processed, and in step S4, the required valve opening is obtained based on the input signal. The opening degree of the expansion valve 13 is operated. For example, during the heating operation when the outside air temperature is 5 ° C., P shown in FIG.
Room temperature 5 ℃ after maintaining T1 at the initial setting opening at point
Is set to the valve opening indicated by point A, and the heating load decreases as the room temperature rises in the subsequent heating operation.
The valve opening is gradually reduced to the point.

As described above, when the electric expansion valve 13 is used as the expansion mechanism to control the refrigerant flow rate according to the load change, the difference between the outside air temperature and the room temperature corresponds to the approximate load in the above embodiment. The value is set as a value, and based on this value, the proper valve opening degree is set in advance, which is obtained in advance from the operating conditions such as the outside air temperature, the fan tap state, and the inverter frequency. Therefore, unlike the conventional device, it is possible to control the valve opening degree according to the substantial load variation of the electric expansion valve without requiring a dedicated detection circuit for controlling the electric expansion valve.

Further, in the conventional device, it was necessary to partially bypass the refrigerant, but in the above-described embodiment, all the refrigerant circulates in the refrigeration cycle, so the refrigerating capacity is also improved. In addition, in the application to the multi-type air conditioner described above, the optimal operation control corresponding to the load fluctuation in each room is provided by installing the electric expansion valve for each pipe communicating with each indoor unit, and other special It is possible to implement without the need for such a detection circuit, and further, in the configuration in which the electric expansion valve is provided in the main liquid pipe as in the conventional device, together with the information on the number of operating rooms, By processing the average value of the indoor temperature as the indoor temperature in the above-described embodiment, it becomes possible to perform the operation corresponding to the load variation as compared with the conventional device.

In the above embodiment, the electric motor-operated expansion valve is of the pulse motor drive type, but can be applied to other types of expansion valves. In addition, the indoor thermistor attached to the room thermostat and the outdoor air thermistor attached to the outdoor heat exchanger were used as the indoor and outdoor temperature detecting means, but the evaporation temperature of the heat exchanger that acts as the other evaporator is used. And a thermistor that measures the condensation temperature of the heat exchanger that acts as a condenser,
It is also possible to configure based on those detected temperature thermistors.

(Effects of the Invention) As described above, in the air conditioner of the present invention, when performing the opening control of the electric expansion valve in order to increase / decrease the refrigerant flow rate according to the load change, the air conditioner becomes It does not require the measured values of the refrigerant temperature on the inlet side and the outlet side of the heat exchanger on the side acting as an evaporator, and obtains a signal corresponding to the approximate load based on the temperature difference between the indoor side and the outdoor side, and further Since it is decided to select an appropriate opening that is preset in the control device, there is no need for a dedicated detection refrigerant circuit or side temperature sensor for controlling the opening of the electric expansion valve as in the conventional device, Further, it is not necessary to bypass the refrigerant, and therefore, it is possible to inexpensively configure an apparatus having a control function that copes with load fluctuations and improve refrigeration capacity.

[Brief description of drawings]

FIG. 1 is a functional block diagram of the opening degree control of an electric expansion valve in an air conditioner of the present invention, FIG. 2 is a refrigerant circuit diagram showing an overall configuration of a separate type air conditioner to which the present invention is applied, and FIG. ~ Fig. 6 is a graph showing the relationship between the proper opening degree of the electric expansion valve and usage conditions, Fig. 7 is a flowchart of operation, Fig. 8 is an explanatory diagram showing the operating state over time, and Fig. 9 is It is a schematic diagram of the refrigerant circuit in the conventional apparatus. 1 ... compressor, 4 ... outdoor heat exchanger, 6 ... indoor heat exchanger, 12 ... liquid pipe, 13 ... motorized expansion valve, 14 ... indoor thermistor (first temperature detecting means), 15 ...... Outside air thermistor (second temperature detection means), 16 …… Control device (control means).

Claims (1)

[Claims] 1. A compressor (1), an indoor heat exchanger (6), and an outdoor heat exchanger (4) are connected so that refrigerant can circulate, and the indoor heat exchanger (6) and the outdoor heat exchanger (4). ) Is an air conditioner in which an electric expansion valve (13) is interposed in a liquid pipe (12) connecting with (1), and first temperature detecting means (14) for detecting the temperature inside the room.
And a second temperature detecting means (15) for detecting the temperature outside the room, and the first and second temperature detecting means (14).
The electric expansion valve (13) based on the temperature difference detected by (15)
The control means (16) for controlling the opening degree of the electric expansion valve (13) is reduced as the absolute value of the detected temperature difference increases. For the same absolute value of detected temperature difference, the opening degree of the electric expansion valve (13) is decreased with the decrease of the outdoor temperature during the cooling operation, while the opening temperature of the electric expansion valve (13) is increased with the increase of the outdoor temperature during the heating operation. ) The air conditioner is characterized by being controlled so as to reduce the opening degree.