JPH1038398A - Controller of electric expansion valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the degree of superheat of a refrigerant more accurately and also, control an electric expansion valve, according to this degree of superheat, by detecting the temperature of the refrigerant on outlet side of an evaporator and the temperature of the refrigerant on inlet side severally, and computing the temperature of evaporation, and further, seeking the degree of superheat of the refrigerant. SOLUTION: A temporary degree-of-superheat computing means 12 receives the input of the refrigerant temperature TC1 on outlet side of an outdoor heat exchanger 24 detected by a temperature sensor 51 and the refrigerant temperature TC2 on inlet side, and computes temporary degree SH0 of superheat, and adds it to a temperature displacement retrieval means 13. A evaporation temperature computing means 14 receives the input of the refrigerant temperature TC2 on inlet side detected by a temperature sensor in addition to the displacement TGX of saturation temperature, and computes the evaporation temperature TG. The degree of superheat SH computed with a refrigerant degree-of-superheat computing means 15 is added to an expansion valve aperture control means 16, and it controls the aperture of the electric expansion valve 25. Hereby, the degree of superheat of the refrigerant can be detected more accurately, and the electric expansion valve can be controlled, according to this degree of superheat.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an electric expansion valve for controlling the opening of the electric expansion valve so that the refrigerant in the refrigeration cycle has an appropriate degree of superheating.

[0002]

2. Description of the Related Art FIG. 14 shows a portion corresponding to an outdoor unit in a refrigeration cycle constituting an air conditioner. A muffler 22 is provided on a discharge side of a compressor 21 driven by a commercial power supply. The gas refrigerant is supplied to the four-way switching valve 23 through the muffler. The four-way switching valve 23
In the cooling operation mode, the gas refrigerant is sent to the outdoor heat exchanger 24 as indicated by the solid line arrow, and in the heating operation mode, the gas refrigerant is transmitted through the strainer 28 through the strainer 28 as shown in a room (not shown) in the heating operation mode. It is sent to the indoor heat exchanger that constitutes the unit.

[0003] Assuming that the air conditioner is operated in the cooling mode,
The gas refrigerant sent to the outdoor heat exchanger 24 is heat-exchanged here and converted into a liquid refrigerant. The liquid refrigerant is subjected to flow control by an electric expansion valve 25, and further stored in a liquid tank 26. It is sent to an indoor heat exchanger (not shown) via a dryer 27 for removing moisture.
This liquid refrigerant is converted into a gas refrigerant in the indoor heat exchanger and returned to the four-way switching valve 23 via the strainer 28. Further, the gas refrigerant that has passed through the four-way switching valve 23 is sent to the accumulator 30. The gas refrigerant contains some liquid refrigerant, and the accumulator 30 separates the liquid refrigerant, sends out only the gas refrigerant, and causes the compressor 21 to suck it.

On the other hand, if operated in the heating mode,
The gas refrigerant sent to the indoor heat exchanger via the strainer 28 is converted here into a liquid refrigerant, and then is converted into a liquid refrigerant.
7, and is stored in the liquid tank 26. Further, the flow rate of the liquid refrigerant is controlled by the electric expansion valve 25 and is supplied to the outdoor heat exchanger 24. The liquid refrigerant is converted into a gas refrigerant by the outdoor heat exchanger 24 and then sent to the accumulator 30 through the four-way switching valve 23. Then, only the gas refrigerant obtained by separating some of the liquid refrigerant contained therein is sucked into the compressor 21.

[0005]

As is well known, the motorized expansion valve 25 is a heat exchanger acting as an evaporator,
It controls the flow rate of the liquid refrigerant to keep the state of the outdoor heat exchanger when operating in the heating mode or the state of the indoor heat exchanger when operating in the cooling mode. It is necessary to determine the degree, that is, the difference from the saturation temperature.

Originally, this degree of superheat can be detected with high accuracy by providing a pressure sensor on the suction side of the compressor. However, since the pressure sensor is expensive, an air conditioner as shown in FIG. In, the degree of superheat is determined by a pseudo-saturation temperature detection circuit including a temperature sensor which is much cheaper than a pressure sensor.

That is, in the refrigeration cycle shown in FIG. 14, a capillary tube 29 is provided between the inlet side of the motor-operated expansion valve 25 and the suction side of the accumulator 30 in the heating operation mode, so that the gas refrigerant on the accumulator 30 side is cooled. The temperature is detected by the temperature sensor 34 as the pseudo saturation temperature TG. However, in this case, a difference from the actual saturation temperature occurs due to the flow rate of the refrigerant and the presence of the flash gas. Therefore, the temperature sensor 3 provided on the suction side of the compressor 21 is used.
1. Temperature sensor 32 provided on discharge side and outdoor heat exchanger 2
4, each temperature detection value TS of the temperature sensor 33 provided on the input side,
It was necessary to correct the pseudo saturation temperature TG by TD and TE. For this reason, a large number of temperature sensors are required to determine the actual degree of superheat, and a complicated correction operation has to be performed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and more precisely detects the degree of superheat of a refrigerant based on temperature information of a minimum necessary temperature sensor used for controlling a refrigeration cycle. It is another object of the present invention to provide a control device for an electric expansion valve that controls the electric expansion valve according to the degree of superheat.

[0009]

The present invention will be described below together with its principle. Now, as shown in FIG.
An electric expansion valve 25 is provided upstream of the outdoor heat exchanger 24 as an evaporator, and the refrigerant circulates in the direction of arrow A. A temperature sensor 51 is provided at the outlet side of the indoor heat exchanger.
The temperature sensors 52 are provided between the electric expansion valve 25 and the outdoor heat exchanger 24, that is, on the inlet side of the outdoor heat exchanger 24 to detect the temperature of the refrigerant.

Here, when the throttle amount of the electric expansion valve 25 is small and the circulation amount of the refrigerant is large, the temperature of the refrigerant exiting the electric expansion valve 25 is indicated by a solid line P in FIG. Changes to Conversely, when the throttle amount of the electric expansion valve 25 is large and the circulation amount of the refrigerant is small, the temperature of the refrigerant that has exited the electric expansion valve 25 changes as indicated by the dashed-dotted line Q in FIG. I do. Among them, the electric expansion valve 25 when the circulation amount is small
, The temperature TC2 detected by the temperature sensor 52 is assumed to be the evaporation temperature TG. From the state of these temperature changes and the properties of the refrigerant, the following a to h
You can guess the content of the term. a. If there is a pressure difference between the inlet side and the outlet side of the outdoor heat exchanger 24 as an evaporator (hereinafter, also referred to as pressure loss or flow rate pressure loss), a temperature displacement TGX occurs. b. When the throttle amount by the electric expansion valve is large, the circulation amount of the refrigerant decreases and the flow pressure loss decreases, so that the temperature TC2 on the inlet side of the outdoor heat exchanger 24 approaches the evaporation temperature TG without limit. c. The temperature displacement TGX due to the flow rate pressure loss changes depending on the relationship between the refrigerant circulation amount and the flow rate pressure loss of the outdoor heat exchanger 24. d. If the circulation amount of the refrigerant is constant, it is considered that the temperature displacement TGX due to the flow pressure loss is also constant. e. However, even if the flow pressure loss is constant, the value of the temperature displacement TGX changes depending on the temperature of the refrigerant. f. The displacement of the temperature displacement TGX is obtained from the relationship between the saturation pressure of the refrigerant and the refrigerant temperature. g. From the above, the evaporation temperature TG is obtained by the following equation. TG = TC2-TGX (1) h. If this evaporation temperature TG is known, the degree of superheat SH can be obtained by the following equation. SH = TC1-TG (2) Whether the above guess is appropriate or not will be verified by comparing it with actual operation data. Among various refrigerants used in the air conditioner, for example, the relationship between the saturation pressure and the refrigerant temperature of R22 is shown in FIG. 8. FIG. 9 is a graph showing the relationship between the displacement of the refrigerant pressure, that is, the pressure loss and the displacement of the saturation temperature, using the temperature of the refrigerant as a parameter from this diagram. If the detected value TC2 of the temperature sensor 52 is used as the temperature of the refrigerant, each value in the table corresponds to a temperature displacement TGX obtained by converting a pressure loss determined according to the evaporation temperature into a temperature. As shown in FIG. 12, a temporary superheat degree SH0 obtained by subtracting the refrigerant temperature TC2 on the inlet side from the refrigerant temperature TC1 on the outlet side of the outdoor heat exchanger 24 is assigned to the pressure loss in the table.

As shown in FIG. 10, in a multi-type air conditioner in which three indoor units are connected to one outdoor unit, the pipe lengths of the A, B, and C rooms are equal to each other. All of the indoor units are operated in the cooling mode defined by JIS. At this time, the relationship between the temperature difference between the inlet side temperature and the outlet side temperature of the indoor unit acting as an evaporator (outlet side temperature−inlet side temperature) and the cooling capacity was examined, and the actual operation shown in the diagram of FIG. Data was obtained. This diagram shows the degree of superheat and the evaporation pressure as parameters.
In this case, the load demand of each of the rooms A, B and C is 100
%, 80% and 50%.

If the difference between the temperature TC2 on the inlet side and the temperature TC1 on the outlet side is 1 ° C. when the degree of superheat of the indoor unit in the room A is 5K, the evaporation pressure corresponding to the load requirement of 100% Is assumed to be 5.2 (Kg / cm ² ), so that the following equation holds. TC1 = 5 + 5.2 = 10.2 [° C.] (3) TC2 = 1 + 10.2 = 11.2 [° C.] (4) Accordingly, the error between TC2 and the evaporating temperature is 6 [° C.], as shown in FIG. The values in the chart (SH0 is “〜1” and TC2 is “10
15 ").

Next, in the indoor unit of the room B, TC2-TC
1 = −7 ° C. Also in this indoor unit, the evaporating pressure is 5.2 (Kg / cm ² ), and the superheat degree corresponding to the cooling capacity of 80% is 12 in this evaporating pressure range.
It becomes K. Then, the following equation is established. TC1 = 12 + 5.2 = 17.2 [° C.] (5) TC2 = −7 + 17.2 = 10.2 [° C.] (6) Accordingly, the error between TC2 and the evaporation temperature is 5 [° C.], and FIG. (SH0 is “6 to 10” and TC2 is “1”
0 to 15 ”).

Next, in the indoor unit of the room C, TC2-TC
It is assumed that 1 = −16 ° C. Also in this indoor unit, the evaporating pressure is 5.2 (Kg / cm ² ), so that within this evaporating pressure range, the degree of superheat corresponding to 50% of the cooling capacity is 1
8K. Then, the following equation is established. TC1 = 18 + 5.2 = 23.2 [° C.] (7) TC2 = −16 + 23.2 = 7.2 [° C.] (8) Accordingly, the error between TC2 and the evaporation temperature is 2 [° C.] and FIG. (Values at hatched positions where SH0 is “14 to 16” and TC2 is “5 to 10”).

From the actual operation data shown in FIG.
The error between C2 and the evaporating temperature was calculated backward, and it was confirmed that the temporary degree of superheat determined in advance corresponding to the pressure loss was appropriate.

Therefore, the control device for the electric expansion valve according to the present invention detects the refrigerant temperature TC1 on the outlet side and the refrigerant temperature TC2 on the inlet side of the evaporator having the electric expansion valve upstream. On the other hand, the refrigerant temperature characteristic table shown in FIG. 12 in which the superheat degree SH0 and the temperature displacement TGX are associated with each other using the detected temperature TC2 as a parameter and the value of TC1-TC2 as the temporary superheat degree SH0 is stored in the storage means. From the refrigerant temperature characteristic table to calculate the evaporation temperature TG, and further subtract the TG from TC1 to determine the refrigerant superheat degree. Further, based on the refrigerant superheat degree, the electric expansion valve It controls the opening degree, thereby detecting the degree of superheat of the refrigerant more accurately, based on the temperature information of the minimum necessary temperature sensor used for controlling the refrigeration cycle, It is possible to control the motorized expansion valve according to the degree of superheat.

Further, in the control device for the electric expansion valve according to the present invention, when the multi-type air conditioner is operated in the cooling mode, the electric expansion valve is provided on the upstream side of the indoor heat exchanger acting as an evaporator. The present invention is applied to a refrigeration cycle having a valve, and controls these electric expansion valves using the control system according to the first aspect.

Further, in the control device for the electric expansion valve according to the third aspect, the indoor heat exchanger is housed in an outdoor unit that houses the compressor, the four-way switching valve, the outdoor heat exchanger, and the electric expansion valve. This is applied to the so-called refrigeration cycle of a custom air conditioner that connects indoor units, and when this air conditioner is operated in the heating mode, the refrigerant flows in the order of an electronic expansion valve, an outdoor heat exchanger, and a compressor. In controlling the electric expansion valve in the case of circulating water, a temperature sensor which is often installed in a pipe on the suction side of the compressor is used as the first temperature detecting means. , An existing temperature sensor can be used.

The electric expansion valve used in the refrigeration cycle of a custom air conditioner is provided in an indoor unit or an outdoor unit. The control device for the electric expansion valve according to the fourth aspect is essentially a compressor, a four-way switching valve, an outdoor heat exchanger, an electric expansion valve, and an indoor heat exchanger, regardless of the installation position of the electric expansion valve. , An electric expansion valve of a refrigeration cycle in which a four-way switching valve and a compressor are sequentially connected.

On the other hand, frost may form on the outdoor heat exchanger during operation in the heating mode. As one method for dealing with this frost formation, the temperature TE on the inlet side of the outdoor heat exchange is detected, and the rotation speed of the outdoor fan is changed. By changing the rotation speed, the inlet side temperature TE of the outdoor heat exchanger as the evaporator is changed.
The relationship between pressure drop and pressure loss also changes. Accordingly, the displacement (correction value) TGX of the evaporation temperature with respect to the inlet-side temperature TE of the evaporator is as shown in FIG. Therefore, the control device for the electric expansion valve according to claim 5 detects the temperature on the discharge side of the compressor when the rotation speed of the outdoor fan is changed and controlled by the temperature TE on the inlet side of the outdoor heat exchanger. Since the degree of superheat is corrected in accordance with the temperature detection value of the third temperature detecting means, and the opening target value of the electric expansion valve is corrected based on the corrected degree of superheat, the number of rotations of the outdoor fan is controlled. Even in this case, the degree of superheat of the refrigerant can be detected more accurately, and the electric expansion valve can be controlled according to the degree of superheat.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on preferred embodiments shown in the drawings. FIG. 2 is a schematic configuration diagram of the first embodiment of the present invention. In the figure, the same elements as those in FIG. 14 showing the conventional apparatus are denoted by the same reference numerals, and the description thereof will be omitted. This shows a part corresponding to the outdoor unit in the refrigeration cycle constituting the air conditioner. When the refrigeration cycle is operated in the heating mode, the refrigerant circulates in the direction of arrow A, and the outdoor heat exchanger 24 acts as an evaporator. An electric expansion valve 25 is provided upstream of the outdoor heat exchanger 24. In order to control the degree of opening of the electric expansion valve 25, a temperature sensor 51 is provided on the outlet side of the outdoor heat exchanger 24, and a temperature sensor 52 is provided on the inlet side, and the detection signals of these temperature sensors are overheated. Added to the degree control system 10. The superheat control system 10 is configured to control the opening of the electric expansion valve 25 based on the detected temperature values TC1 and TC2. In this embodiment, the temperature detection values TC1, TC1,
In order to control the electric expansion valve 25 based on TC2, the pseudo saturation temperature detection circuit including the capillary tube 29 and the temperature sensor 34 in FIG. 14 is eliminated.

FIG. 1 is a functional block diagram showing a detailed configuration when the overheating temperature control system is constituted by a microprocessor (CPU). As shown in FIG. 12, the refrigerant temperature characteristic storage means 11 uses the temperature TC2 on the inlet side of the outdoor heat exchanger 24 as a parameter to temporarily store the degree of superheat SH0.
And a refrigerant temperature characteristic indicating the relationship between the temperature and the displacement TGX of the saturation temperature. The temporary superheat degree calculating means 12 inputs the refrigerant temperature TC1 on the outlet side of the outdoor heat exchanger 24 and the refrigerant temperature TC2 on the inlet side detected by the temperature sensor 51, and the temporary superheat is calculated by the following equation. Degree S
H0 is calculated and added to the temperature displacement search means 13. SH0 = TC1-TC2 (9) The temperature displacement search means 13 inputs the provisional degree of superheat SH0 and the refrigerant temperature TC2 detected by the temperature sensor 52, and searches the refrigerant temperature characteristic storage means 11 for each input. Saturation temperature displacement T corresponding to SH0 and TC2
Read GX. The displacement TGX of the saturation temperature read from the refrigerant temperature characteristic storage means 11 is calculated by the evaporating temperature calculation means 1
Added to 4. The evaporating temperature calculating means 14 inputs the refrigerant temperature TC2 on the inlet side of the outdoor heat exchanger 24 detected by the temperature sensor 52 in addition to the saturation temperature displacement TGX, and calculates the evaporating temperature TG according to the following equation. TG = TC2−TGX (10) Then, the refrigerant superheat degree calculating means 15 receives the calculated evaporation temperature TG and the refrigerant temperature TC1 on the outlet side of the outdoor heat exchanger 24 detected by the temperature sensor 51, and receives the following equation. To calculate the actual superheat degree SH. SH = TC1-TG (11) The superheat degree SH calculated by the refrigerant superheat degree calculation means 15 is added to the expansion valve opening degree control means 16, and the expansion valve opening degree control means 1
6 controls the opening degree of the electric expansion valve 25 so that the degree of superheat SH follows a predetermined value. The electric expansion valve 25 is, for example, driven by a pulse motor with the number of pulses at the time of full opening being 500, and various details have been proposed and publicly known, and thus detailed description thereof will be omitted. In addition, instead of the temperature sensor 51 provided on the outlet side of the outdoor heat exchanger 24, the temperature detection value TS of the temperature sensor 31 provided in the system which is drawn into the compressor 21 after passing through the four-way switching valve 23 is used. be able to.

Thus, according to the first embodiment shown in FIGS. 1 and 2, the superheat degree of the refrigerant can be more accurately determined based on the minimum necessary temperature information of the temperature sensor used for controlling the refrigeration cycle. In addition to the detection, the electric expansion valve can be controlled according to the degree of superheat.

FIG. 3 is a schematic configuration diagram of a second embodiment of the present invention. This shows a case where three indoor units 2A, 2B, 2C are connected to one outdoor unit 1 as an example of a multi-type air conditioner, and the indoor heat exchange constituting each indoor unit 2A, 2B, 2C is shown. The electric expansion valves 25A, 25B, 25C are connected in series with the devices 41A, 41B, 41C.
Assuming that the refrigerant circulates in the direction of the arrow when operating the multi-type air conditioner in the cooling mode, the electric expansion valves 25A, 25B, and 25C are connected to the indoor heat exchanger 41, respectively.
A, 41B, and 41C are provided on the upstream side. In order to control the degree of superheat of the refrigerant on the outlet side of the indoor heat exchangers 41A, 41B, 41C, these indoor heat exchangers 4
A temperature sensor 51 is provided on the outlet side of each of the indoor units 2A, 2B, and 2C.
A superheat control system 10A, 10B, 10C for controlling the degree of opening of the electric expansion valves 25A, 25B, 25C for each of B, 2C is provided. These superheat control systems 10A, 10A
B and 10C have the same configuration as the superheat control system 10 shown in FIG. Thereby, the superheat degree control explained in principle with reference to FIG. 10 becomes possible.

FIG. 4 shows a configuration example of a third embodiment of the present invention. In a refrigeration cycle constituting a so-called custom air conditioner, one indoor unit is connected to one outdoor unit. Applied. Figure 4
(A) shows a compressor 21, a four-way switching valve 23,
Outdoor heat exchanger 24, electric expansion valve 25, indoor heat exchanger 4
1, a refrigeration cycle in which the four-way switching valve 23 and the compressor 21 are sequentially connected. Among these, only the indoor heat exchanger 41 is housed in the indoor unit 4A, and all other components are housed in the outdoor unit 3A. Have been. In order to control the refrigeration cycle, a temperature sensor 31 is provided on a pipe on the suction side of the compressor 21, and a temperature sensor 32 is provided on a pipe on the discharge side, between the outdoor heat exchanger 24 and the electric expansion valve 25. A temperature sensor 33 is provided, and a temperature sensor 35 is provided on the outlet side of the indoor heat exchanger 41, assuming that the refrigerant circulates in the direction of the arrow A during the operation in the heating mode. When operating in the heating mode, the superheat degree control system 10A
Is the temperature TC1 on the outlet side of the evaporator, and the detected temperature TE of the temperature sensor 33 is the temperature T1 on the inlet side of the evaporator.
The opening degree of the electric expansion valve 25 is controlled as C2. on the other hand,
At the time of operation in the cooling mode in which the refrigerant circulates in the direction of arrow B, the detected temperature TS of the temperature sensor 31 is set as the temperature TC1 on the outlet side of the evaporator, and the detected temperature TC of the temperature sensor 35 is set as the temperature TC2 on the inlet side of the evaporator. The opening of the electric expansion valve 25 is controlled.

In the refrigerating cycle shown in FIG. 4B, only the indoor heat exchanger 41 is provided in the indoor unit 4B, and the temperature sensor 35
4A is different from that of FIG. 4A in that it is provided in the outdoor unit 3B. Also in this case, the superheat degree control system 10B sets the detected temperature TS of the temperature sensor 31 to the temperature TC1 on the outlet side of the evaporator and the detected temperature T of the temperature sensor 33 during the operation in the heating mode.
Let E be the temperature TC2 on the inlet side of the evaporator,
5 is controlled. On the other hand, during the operation in the cooling mode in which the refrigerant circulates in the direction of the arrow B, the detected temperature TS of the temperature sensor 31 is set to the temperature TC1 on the outlet side of the evaporator, and the detected temperature TC of the temperature sensor 35 is set to the temperature on the inlet side of the evaporator. The opening of the electric expansion valve 25 is controlled as TC2. FIG. 4C shows an example in which the indoor unit 4C is provided with the electric expansion valve 25 in addition to the indoor heat exchanger 41. Among them, the temperature sensor 35 is provided between the indoor heat exchanger 41 and the electric expansion valve 25. Is provided. In this case, during operation in the heating mode, the superheat control system 10C sets the detected temperature TS of the temperature sensor 31 to the temperature TC1 on the outlet side of the evaporator, and sets the detected temperature TE of the temperature sensor 33 to the temperature on the inlet side of the evaporator. The opening of the electric expansion valve 25 is controlled as TC2. On the other hand, during the operation in the cooling mode in which the refrigerant circulates in the direction of the arrow B, the detected temperature TS of the temperature sensor 31 is set to the temperature TC1 on the outlet side of the evaporator, and the detected temperature TC of the temperature sensor 35 is set to the temperature on the inlet side of the evaporator. The opening of the electric expansion valve 25 is controlled as TC2.

Thus, in various types of air conditioners, the degree of superheat of the refrigerant is more accurately detected based on the minimum necessary temperature information of the temperature sensor used for controlling the refrigeration cycle, and the degree of superheat is determined in accordance with the degree of superheat. The electric expansion valve can be controlled.

FIG. 5 is a block diagram showing the configuration of the fourth embodiment of the present invention. In the drawing, the same elements as those in FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted. This embodiment shows another example of the configuration of the superheat control system. For the elements shown in FIG. 1, a temperature sensor provided on the discharge side of the compressor instead of the expansion valve opening control means 16 is used. 32 detected temperature T
D, the degree of superheat SH is corrected to control the degree of opening of the motor-operated expansion valve 25, and expansion valve opening control means 16A is used. Further, the detected temperature TE of the temperature sensor 33 provided on the inlet side of the evaporator is used. The configuration differs from FIG. 1 in that the outdoor fan control means 43 controls the rotation speed of the outdoor fan 42 based on this.

In the multi-type air conditioner, in the heating operation mode, the outdoor fan control means 43 determines the load state based on the refrigerant temperature TE on the inlet side of the evaporator, and changes the rotation speed of the outdoor fan 42 to a light wind or a weak wind. In addition, the rotation speed is switched to three stages corresponding to strong winds, and the detection value of the degree of superheat is corrected. The expansion valve opening control means 16A shown in FIG. 5 corrects the degree of superheat SH and controls the opening of the electric expansion valve 25 in accordance with the correction. Hereinafter, regarding the correction of the degree of superheat,
This will be described in detail below with reference to the tables in FIGS. 6 (a), 6 (b) and 6 (c).

First, the outdoor fan control means 43 drives the rotation speed of the outdoor fan 42 to one of light wind, weak wind, and strong wind according to the temperature TE on the inlet side of the evaporator. Further, the expansion valve opening degree control means 16A corrects the degree of superheat SH by an α value shown in FIG. 6A in accordance with the temperature TD on the discharge side of the compressor detected by the temperature sensor 32. That is, the degree of superheat SH obtained by the refrigerant superheat degree calculating means 15 and the degree of superheat SH shown in FIG.
The current superheat degree ΔT is calculated by the following equation using the correction value α of (a). ΔT = SH−α (12) Next, the expansion valve opening degree control means 16A calculates the superheat degree Δ
As shown in FIG. 6B, it is determined from the T and the correction value α to which of the seven zones A to G the superheat degree ΔT belongs.

Next, the number of pulses of the pulse motor for driving the electric expansion valve 25 is changed by the value shown in FIG. 6C according to the current superheat zone and the previous superheat zone. In this case, the number of pulses 500 corresponds to the full opening of the electric expansion valve 25, and the expansion valve opening degree control means 16A sets the lower limit to 70 pulses and sets the upper limit to 500 pulses in the range shown in FIG. Is corrected for the opening degree corresponding to.

Thus, according to this embodiment, during the heating operation using the outdoor heat exchanger as the evaporator, even in the case where the number of revolutions of the outdoor fan is switched in accordance with the temperature on the inlet side, the experiment was previously obtained. By the correction of the degree of superheat by the correction value and the change of the opening of the electric expansion valve accompanying this,
Even when the air conditioning load fluctuates greatly from a low temperature range to a high temperature range, the degree of superheat can be appropriately controlled.

In the embodiment shown in FIG. 5, TE
As described in the third embodiment shown in FIG. 4, the same sensor can be used as the temperature sensor 33 for detecting the temperature and the temperature sensor 52 for detecting the TC2.

[0034]

As is apparent from the above description, according to the control device for the electric expansion valve according to the first aspect, the refrigerant temperature and the refrigerant temperature at the outlet side of the evaporator having the electric expansion valve in the upstream portion are determined. While detecting the refrigerant temperature on the inlet side, the temperature difference is used as a temporary superheat degree, and the temperature on the inlet side is used as a parameter, using the refrigerant temperature characteristic table in which the temporary superheat degree and the temperature displacement are associated with each other. Is calculated, and the degree of superheat of the refrigerant is obtained from the evaporation temperature to control the opening of the electric expansion valve.Therefore, based on the temperature information of the minimum necessary temperature sensor used for controlling the refrigeration cycle. Thus, the degree of superheat of the refrigerant can be detected more accurately, and the electric expansion valve can be controlled according to the degree of superheat.

Further, the pseudo-saturation temperature detecting circuit used in the conventional device can be eliminated.

According to a second aspect of the present invention, when the multi-type air conditioner is operated in the cooling mode,
Applied to a refrigeration cycle equipped with an electric expansion valve on the upstream side of the indoor heat exchanger acting as an evaporator, respectively.
Thereby, substantially the same effect as that of the first aspect can be obtained.

A control unit for an electric expansion valve according to a third aspect of the present invention is an indoor unit in which an indoor heat exchanger is housed in an outdoor unit in which a compressor, a four-way switching valve, an outdoor heat exchanger, and an electric expansion valve are housed. The present invention is applied to a refrigeration cycle of a custom air conditioner in which a compressor is connected, and in addition to obtaining substantially the same effects as those described in claim 1, as a first temperature detecting means, a suction side of a compressor is provided. There is an advantage that a temperature sensor often installed in a pipe can be used.

According to a fourth aspect of the present invention, there is provided a control device for an electric expansion valve in which a compressor, a four-way switching valve, an outdoor heat exchanger, an electric expansion valve, an indoor heat exchanger, a four-way switching valve, and a compressor are sequentially connected. Since the electric expansion valve of the refrigeration cycle is controlled, substantially the same effects as those of the first aspect can be obtained.

The control device for the electric expansion valve according to the fifth aspect detects the temperature on the discharge side of the compressor when the rotational speed of the outdoor fan is changed and controlled by the temperature on the inlet side of the outdoor heat exchanger. Since the degree of superheat is corrected in accordance with the temperature detection value of the third temperature detecting means, and the opening target value of the electric expansion valve is corrected based on the corrected degree of superheat, the number of rotations of the outdoor fan is controlled. Even in this case, the degree of superheat of the refrigerant can be detected more accurately, and the electric expansion valve can be controlled according to the degree of superheat.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing a detailed configuration of a superheat control system, which is a main component of a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a first embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of a second embodiment of the present invention.

FIG. 4 is a system diagram showing various configuration examples according to a third embodiment of the present invention.

FIG. 5 is a functional block diagram showing a detailed configuration of a superheat control system, which is a main component of a fourth embodiment of the present invention.

FIG. 6 is a table for explaining the operation of the fourth embodiment shown in FIG. 5;

FIG. 7 is a diagram showing a part of a refrigeration cycle and showing a change in temperature of a refrigerant in order to explain the principle of the present invention.

FIG. 8 is a diagram showing a relationship between a representative refrigerant saturation pressure and a refrigerant temperature.

FIG. 9 is a chart expressing a relationship between a typical refrigerant pressure displacement and a saturation temperature displacement using temperature as a parameter.

FIG. 10 is a block diagram showing a configuration example of an air conditioner for demonstrating the principle of the present invention.

11 is an actual operation characteristic diagram showing the relationship between the cooling capacity of the air conditioner shown in FIG. 10 and the temperature difference between the inlet side and the outlet side of the evaporator, using the degree of superheat and the evaporation temperature as parameters.

12 is a chart expressing the relationship between the pressure displacement and the saturation temperature displacement shown in FIG. 9 by replacing the relationship between the provisional degree of superheat and the saturation temperature displacement.

FIG. 13 is a diagram showing the relationship between the evaporation temperature of the refrigerant and the temperature on the evaporator inlet side, using pressure loss as a parameter.

FIG. 14 is a diagram showing a part of a refrigeration cycle for explaining a conventional method of obtaining a degree of superheat in controlling an electric expansion valve.

[Explanation of symbols]

 1, 3A, 3B, 3C Outdoor unit 2A, 2B, 2C, 4A, 4B, 4C Indoor unit 10, 10A, 10B, 10C Superheat degree control system 11 Refrigerant temperature characteristic storage means 12 Temporary superheat degree calculation means 13 Temperature displacement search means 14 Evaporation temperature calculation means 15 Refrigerant superheat degree calculation means 16, 16A Expansion valve opening degree control means 21 Compressor 23 Four-way switching valve 24 Outdoor heat exchanger 25 Electric expansion valve 30 Accumulator 31, 32, 33, 34, 51, 52 Temperature sensor 41, 41A. 41B, 41C Indoor heat exchanger

Claims (5)

[Claims] 1. A first temperature detecting means for detecting a refrigerant temperature at an outlet side of an evaporator and an inlet for controlling a superheat degree of a refrigerant in a refrigeration cycle having an electric expansion valve upstream of the evaporator. A controller for controlling the degree of opening of the motor-operated expansion valve on the basis of the respective detected values of the second temperature detecting means for detecting the refrigerant temperature of the evaporator; The difference between the temperature of the inlet side and the temporary superheat degree, the relationship between the pressure displacement of the refrigerant used in the refrigeration cycle and the saturation temperature displacement corresponding to this pressure displacement, the predetermined temporary superheat degree and A refrigerant temperature characteristic storage unit that stores a refrigerant temperature characteristic table expressing the temperature of the refrigerant as a parameter, while replacing the relationship with the displacement of the saturation temperature, the first temperature detection unit, and the second temperature detection Before the difference between each detection value of the means A temporary superheat degree calculating means for calculating a temporary superheat degree, and a value calculated by the temporary superheat degree calculating means by searching the refrigerant temperature characteristic storage means with the detected value of the second temperature detecting means as a refrigerant temperature. A temperature displacement search means for obtaining a displacement of the saturation temperature corresponding to the temporary degree of superheat; and a detection value of the second temperature detection means, using the displacement of the saturation temperature obtained by the temperature displacement search means as a correction value. Evaporating temperature calculating means for subtracting the correction value from the above to obtain the actual evaporating temperature of the refrigerant at the outlet side of the evaporator; and subtracting the actual evaporating temperature from the detected value of the first temperature detecting means to obtain the degree of superheat of the refrigerant. A control device for an electric expansion valve, comprising: a refrigerant superheat degree calculating means for outputting as the following; and an expansion valve control means for controlling an opening degree of the electric expansion valve based on the refrigerant superheat degree. 2. The refrigerating cycle, wherein a plurality of indoor heat exchangers each forming an indoor unit are connected to an outdoor heat exchanger forming an outdoor unit, and the plurality of indoor heat exchangers are respectively provided at an inlet side of the indoor heat exchanger. 2. A multi-type air conditioner which operates in a cooling mode by providing an electric expansion valve and comprises a multi-type air conditioner, wherein the electric expansion valves of the refrigeration cycle are respectively controlled. Control device for electric expansion valve. 3. The air conditioner according to claim 1, wherein the refrigeration cycle includes an indoor unit containing the indoor heat exchanger connected to an outdoor unit containing the compressor, the four-way switching valve, the outdoor heat exchanger, and the electric expansion valve. When operating this air conditioner in the heating mode, the four-way switching valve, the electronic expansion valve, the outdoor heat exchanger, the electric expansion valve in the case of circulating the refrigerant in order of the compressor. To be controlled, the first
The control device for an electric expansion valve according to claim 1, wherein the temperature detecting means is provided in a pipe on a suction side of the compressor. 4. The refrigeration cycle forms an air conditioner in which a compressor, a four-way switching valve, an outdoor heat exchanger, an electric expansion valve, an indoor heat exchanger, the four-way switching valve, and the compressor are sequentially connected. The control device for an electric expansion valve according to claim 1, wherein the electric expansion valve of the refrigeration cycle is controlled. 5. When the refrigeration cycle is operating in a heating mode, the outdoor fan control means controls the number of revolutions of the outdoor fan in accordance with the refrigerant temperature on the inlet side of the outdoor heat exchanger. And a third temperature detecting means for detecting a refrigerant temperature on a discharge side of the compressor, wherein the expansion valve opening control means controls an opening target of the electric expansion valve in accordance with a temperature detection value of the third temperature detecting means. 5. The control device for an electric expansion valve according to claim 3, wherein the value is corrected.