JP2755037B2 - Refrigeration equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerating apparatus having an electric expansion valve for controlling a degree of superheat.

[0002]

2. Description of the Related Art In a refrigeration system in which a condenser, an electric expansion valve, and an evaporator are connected to a compressor having a variable compression capacity,
2. Description of the Related Art In order to ensure the performance of a refrigeration system and prevent the reliability of a compressor from being reduced due to the reflux of a liquid refrigerant, it has been conventional to control the degree of superheat of the refrigerant by adjusting the opening of an electric expansion valve.

In the first conventional example of superheat control, a suction temperature of a compressor is detected, and an evaporation saturation temperature is detected by using a pressure sensor or a bypass capillary, and the superheat degree is determined from the suction temperature and the evaporation temperature. And the opening degree of the electric expansion valve is controlled so that the degree of superheat is controlled within a predetermined range.

A second conventional example is disclosed in, for example,
267656 can be mentioned. In this conventional example, the operating frequency Hz of the compressor during the heating operation,
The condensing temperature Tc and the evaporating temperature Te (or the outside air temperature), and during the cooling operation, the operating frequency Hz of the compressor and the evaporating temperature T
e, detecting the condensation temperature Tc (or the outside air temperature),
The target discharge temperature of the refrigerant discharged from the compressor is derived based on these parameters, and the opening degree of the electric expansion valve is controlled so that the refrigerant discharge temperature from the compressor approaches the target discharge temperature.

[0005]

However, the first problem is to be solved.
In the conventional refrigeration apparatus, there are problems that the pressure sensor is expensive and that there is a capacity loss due to the bypass capillary.

In the second prior art, when the operating frequency of the compressor changes frequently due to the slow follow-up of the discharge temperature, a considerable delay time occurs. If the discharge temperature is not higher than a certain temperature at the time of startup, there is a problem that there is no linear relationship with the degree of superheat.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional disadvantages, and an object of the present invention is to provide a refrigerating apparatus that controls the degree of superheat by adjusting the degree of opening of an electric expansion valve at low cost and with high accuracy. To provide a refrigeration apparatus capable of controlling the temperature.

[0008]

Accordingly, a refrigeration apparatus according to the present invention, as shown in FIG.
A condenser 3 connected to a condenser 3, an electric expansion valve 4, and an evaporator 5; a compression capacity grasping means 20 for grasping a compression capacity Hz of the compressor 1; Temperature sensors 10, 11, 1 for detecting at least one of temperature Tc, evaporation temperature Te in the evaporator, and outside air temperature T
2, operating condition storage for storing the target discharge temperature of the refrigerant discharged from the compressor 1 and the reference opening of the electric expansion valve 4 required at that time in relation to the compression capacity Hz and the detected temperature Tc. Means 21, a discharge temperature sensor 13 for detecting a refrigerant discharge temperature from the compressor 1, a device operation under specific operation conditions, and opening of the electric expansion valve 4 when a target discharge temperature is obtained under the operation conditions. Grasping means 22 for grasping the difference between the degree and the reference opening, and an opening for controlling the opening of the electric expansion valve 4 by correcting the reference opening in the operating condition storage means 21 with the deviation. A control means 23 is provided.

[0009]

In the refrigerating apparatus, the refrigerant discharged from the compressor 1 is first condensed in the condenser 3, then reduced in pressure by the electric expansion valve 4, evaporated in the evaporator 5, and returned to the compressor 1. . In such an operation state of the refrigeration apparatus, for example, the condensation temperature Tc of the condenser 3 is detected by the temperature sensor 10 and the compression capacity Hf of the compressor 1 is determined by the compression capacity determination unit 20. The operating condition storage means 21 stores the detected temperature T
The target discharge temperature Tm for providing an appropriate degree of superheat based on c and the compression capacity Hz, and the reference opening of the electric expansion valve 4 at that time are stored. On the other hand, the discharge temperature sensor 13 detects the temperature To of the refrigerant discharged from the compressor 1. The deviation grasping means 22 includes:
The difference between the valve opening of the electric expansion valve 4 when the discharge refrigerant temperature To reaches the target discharge temperature Tm and the reference opening is grasped. Then, the opening control means 23 corrects the above-mentioned reference opening with this deviation, adjusts the opening of the electric expansion valve 4 with the corrected reference opening, and controls the degree of superheat.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, specific embodiments of the refrigeration apparatus of the present invention will be described in detail with reference to the drawings. FIG. 2 shows a case where the present invention is applied to an air conditioner. In this figure, this air conditioner has an outdoor unit X and an indoor unit Y.
The discharge pipe 1a and the suction pipe 1b of the compressor 1 are connected to the refrigerant pipe 9 via the four-way switching valve 2. An outdoor heat exchanger 3, an electric expansion valve 4, a closing valve 6, an indoor heat exchanger 5, and a closing valve 7 are sequentially provided in the refrigerant pipe 9. An accumulator 15 is provided in the suction pipe 1b. Further, an outdoor fan 16 is provided in the outdoor unit X, and an indoor fan 1 is provided in the indoor unit Y.
7 are provided.

The outdoor heat exchanger 3 and the indoor heat exchanger 5 are provided with temperature sensors 11 and 10, respectively.
The detection signals of the temperature sensors 10 and 11 and the detection signal of the outside air temperature sensor 12 are input to the operating condition storage unit 21. Further, the compressor 1 is connected to a compression capacity grasping means 20 for grasping the compression capacity of the compressor 1 by detecting the operating frequency Hz. It is output to the storage means 21. As shown in FIGS. 4 and 5, the operating condition storage means 21 is required for the target discharge temperature Tm of the discharged refrigerant corresponding to the outside air temperature T measured by the outside air temperature sensor 12 for each operation frequency Hz, and at that time. The number of reference pulses proportional to the reference opening of the electric expansion valve 4 can be read.

On the other hand, a discharge temperature sensor 1
3 is attached to detect the discharged refrigerant temperature To. The deviation grasping means 22 calculates the number of pulses proportional to the actual valve opening of the electric expansion valve 4 when the discharged refrigerant temperature To reaches the target discharge temperature Tm, and the number of reference pulses proportional to the reference opening. Figure out the difference. Then, the opening control means 23 corrects the reference pulse number with this deviation, adjusts the subsequent opening of the electric expansion valve 4 with the corrected pulse number, and controls the degree of superheat.

Next, the operation of the air conditioner during the heating operation will be described. First, the four-way switching valve 2 is switched in the opposite direction to the state shown in FIG. 2 to flow the refrigerant in the counterclockwise direction. The high-temperature discharged refrigerant is condensed in the indoor heat exchanger 5 functioning as a condenser, and at the same time, discharges heat into the room to heat it. The outdoor heat exchanger 3 functioning as an evaporator absorbs heat from the outside to evaporate. Then, it is returned to the compressor 1.

At this time, a procedure for determining the deviation (correction amount) by the deviation grasping means 22 will be described with reference to a flowchart of FIG. In step S1, the operating frequency Hz of the compressor 1 grasped by the compression capacity grasping means 20 is represented by:
Based on the outside air temperature T detected by the outside air temperature sensor 12, the data of FIG. 4 stored in the operating condition storage unit 21 is read to determine the number of reference pulses proportional to the reference opening. The opening degree of the electric expansion valve 4 is determined based on the reference pulse number. For example, when the outside air temperature T is 10 ° C. and the operating frequency Hz is 60 Hz, the reference pulse number is determined to be 95 pulses. Incidentally, the target discharge temperature Tm at this time can be read as 75 ° C. from FIG.

In step S2, it is determined whether or not the operating frequency Hz of the compressor 1 is constant. If the operating frequency Hz is constant (YES), the flow proceeds to step S3. For example, if the above value becomes constant at 60 Hz, the process proceeds to step S3.

In step S3, the discharge temperature T of the compressor 1
It is determined whether or not o is stable. For example, it is determined whether or not the discharge temperature is stable by determining whether the difference between the current discharge temperature and the previous discharge temperature is within a certain temperature range. When the discharge temperature To is stable (YE
S) proceeds to step S4. If not stable (N
O) will be repeated again from step S2. At this time, the count number described later is cleared.

In steps S4 and S5, steps S2,
It is determined whether or not the operating frequency Hz and the discharge temperature To, which have been determined to be constant in S3, continue for a predetermined time. That is, the stable state is counted in step S4,
5 that will count the number n of the predetermined number of times n ₁ or more, and the flow proceeds only to the next step S6 when it is determined that stable (YES). If n is less than ₁ (NO),
It will be repeated from step S2 to a predetermined number of times n ₁ or more. For example, if the operation frequency Hz is 60 Hz and the discharge temperature To is stable at 79 ° C. for a certain time, step S
Go to 6.

In step S6, a stable discharge temperature To
And the target discharge temperature Tm that can be read from FIG. 5 are calculated. In the above case, To is 79 ° C. and Tm is 75 ° C., so the temperature difference is + 4 ° C.

In step S7, based on the temperature difference,
The valve opening of the electric expansion valve 4 is adjusted so that the target discharge temperature Tm is obtained by changing the number of pulses. In the above case, To is 79
Since C and Tm are 75C, the number of pulses is adjusted so that To becomes 75C.

In step S8, the number of pulses corresponding to the valve opening and the target discharge temperature Tm when the discharge temperature To becomes equal to the target discharge temperature Tm by the control in step S7.
The difference from the reference pulse number corresponding to the above is grasped, and this is determined as the correction amount. In the above case, the number of pulses is adjusted so that the discharge temperature To is from 79 ° C. to the target discharge temperature Tm.
° C, and if the number of pulses is 98, the reference pulse number is 95 and the correction amount is determined to be +3 pulses.

Thereafter, the opening control means 23 corrects the number of reference pulses stored in the operating condition storage means 21 based on the correction amount, adjusts the opening of the electric expansion valve 4 to reduce the degree of superheat. Will be in control. It should be noted that the above-mentioned amount of correction may be determined at a representative frequency Hz when the power is turned on, or may be performed at regular intervals or each time a significant change in the outside temperature or the like occurs. .

As described above, in this air conditioner, a table (FIG. 4) showing a reference opening degree for a parameter (for example, an operating frequency Hz, an outside air temperature T) having a large effect on the flow rate of the electric expansion valve 4 is prepared. Then, feedforward control is performed based on this. On the other hand, similarly, a table (FIG. 5) of the target discharge temperatures Tm for the above parameters is also prepared. Then, the difference between the opening of the electric expansion valve 4 and the reference opening when the discharge temperature To becomes equal to the target discharge temperature Tm is determined, and this difference is determined as a correction amount. Thereafter, each value of the reference opening is corrected based on this correction amount, and the degree of superheat is controlled by adjusting the opening of the electric expansion valve 4. Therefore, unlike the case of feedback control, there is no delay. Simple and accurate control becomes possible.

Although a specific embodiment of the refrigerating apparatus of the present invention has been described above, the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the present invention. It is. For example, in the above embodiment, a case where the present invention is applied to an air conditioner is illustrated, but the present invention can be applied to other refrigeration apparatuses. The temperature sensor may be any sensor that measures any one of the condensation temperature, the evaporation temperature, and the outside air temperature, or a part or all of them.

[0024]

As described above, in the refrigerating apparatus of the present invention,
The cost can be reduced compared to the method of directly detecting the degree of superheat using a pressure sensor or a bypass capillary, and even if the state changes due to disturbance, it can follow the feedback control faster than the feedback control.
The degree of superheat can be controlled accurately.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing a full rest configuration of a refrigeration apparatus of the present invention.

FIG. 2 is a piping system diagram of the embodiment.

FIG. 3 is a flowchart illustrating a procedure for determining a correction amount.

FIG. 4 is a table schematic diagram of a reference pulse number proportional to a reference opening degree of the electric expansion valve.

FIG. 5 is a schematic diagram of a target discharge temperature table.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Compressor 3 Condenser 4 Electric expansion valve 5 Evaporator 10 Temperature sensor 11 Temperature sensor 12 Temperature sensor 13 Discharge temperature sensor 20 Compression capability grasping means 21 Operating condition storage means 22 Deviation grasping means 23 Opening control means

Claims (1)

(57) [Claims] 1. A refrigerating apparatus comprising a compressor (1) having a variable compression capacity, a condenser (3), an electric expansion valve (4), and an evaporator (5) connected to the compressor (1). (1) a compression capacity grasping means (20) for grasping the compression capacity (Hz); and a condensing temperature (Tc) in the condenser (3), an evaporation temperature (Te) in the evaporator, and an outside air temperature (T). A temperature sensor (10) (11) (12) for detecting at least one of the temperatures, and a target discharge of the refrigerant discharged from the compressor (1) in relation to the compression capacity (Hz) and the detected temperature (Tc). An operating condition storage means (21) for storing a temperature and a reference opening of the electric expansion valve (4) required at that time, and a discharge temperature sensor for detecting a refrigerant discharge temperature from the compressor (1) ( 13), the apparatus is operated under specific operating conditions, and the target discharge temperature is controlled under the operating conditions. A deviation grasping means (22) for grasping a difference between the opening degree of the electric expansion valve (4) when the degree is obtained and the reference opening degree, and a reference opening degree in the operating condition storage means (21). A refrigerating apparatus characterized by further comprising an opening control means (23) for controlling the opening of the electric expansion valve (4) by correcting the opening.