JPH01305265A - Refrigerating air conditioner - Google Patents

Abstract

PURPOSE:To prevent a hunting by calculating a heating degree difference with a heating degree of the difference of a refrigerant gas temperature and a saturation temperature and a target heating degree, and controlling the interval of the opening operations of an expansion valve in response to a variation from that at the time of previous detection. CONSTITUTION:The pressure of refrigerant gas to be sucked into a refrigerating compressor 1 is detected by a pressure sensor 5, and its temperature is detected by a temperature sensor 6. A controller 8 calculates the saturation temperature of the refrigerant with respect to the detection pressure and further heating degree S by the difference between the saturation temperature and the detection temperature, and obtains a heating degree difference D by the difference between the degree S and a target heating degree. Then, a variation DELTAD is calculated by the difference between the difference D and the heating degree difference at the time of previous detection, the interval of the opening operations of an electric expansion valve 4, i.e., the opening operation per unit time is altered in response to the variation DELTAD, and a control system is followed to a varying load. Thus, it can prevent the control system from hunting.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a refrigeration and air conditioning system in which the flow rate of refrigerant is controlled by an expansion valve.

[Conventional technology]

FIG. 4 shows a block diagram of a conventional refrigeration and air conditioning system disclosed in, for example, Japanese Patent Application Laid-Open No. 60-178254. A condenser cools the refrigerant gas from the compressor 1 and converts it into a high-pressure refrigerant liquid; 15 is a temperature-type automatic expansion valve that reduces the pressure of the refrigerant liquid from the condenser 2; 3 is a temperature-type automatic expansion valve 1;
The refrigerant gas is sent to the refrigerant compressor 1 by the evaporator which performs a cooling action by heat-exchanging the refrigerant liquid from 5 and converting it into refrigerant gas. 16 is a temperature sensing cylinder for detecting the temperature of the refrigerant gas sent to the refrigerant compressor 1 and generating refrigerant pressure to make the detected temperature the saturation temperature of the refrigerant; 17 is a temperature sensing tube for detecting the temperature of the refrigerant gas sent to the refrigerant compressor 1; Pressure and temperature type automatic expansion valve 15
This is a pressure equalizing pipe to lead to.

Next, the operation will be explained. The high-temperature, high-pressure refrigerant gas compressed by the refrigerant compressor 1 is sent to the condenser 2 and condensed to become a high-pressure refrigerant liquid, and this refrigerant liquid is depressurized by the thermostatic automatic expansion valve 15 and sent to the evaporator Sent to 3.

The low-pressure refrigerant gas obtained by the heat exchange action of the evaporator 3 is sent to the refrigerant compressor 1 again.

In the above operation cycle, the refrigerant flow rate is controlled mainly by the thermostatic automatic expansion valve 15 as follows. P8. The pressure that makes the temperature of the refrigerant gas detected by the extreme temperature point 16 the saturation temperature of the refrigerant. The pressure of the refrigerant gas guided by the pressure equalization pipe 17 is PS The value obtained by converting the static heating degree setting value set in the temperature type automatic expansion valve 15 into the internal spring pressure is PS. When Ps>P+Pi, the temperature type automatic expansion valve 15 The expansion valve 15 is opened, and when PS<P+PS, the valve is closed. If the heating degree of the refrigerant gas sent to the refrigerant compressor 1 maintains the static heating degree setting value and the road-to-road value and stable operation is performed, PS = P + Pff, and the temperature-type automatic expansion valve 15 The valve opening degree of is kept constant. However, since the heating degree changes depending on the operating conditions, the valve opening degree changes according to the above relational expression. That is, when the heating degree of the refrigerant gas becomes larger than the static heating degree setting value, the valve opens, and when it becomes smaller, the valve closes. As described above, the valve opening degree of the thermostatic automatic expansion valve 15 is continuously controlled according to the degree of heating of the refrigerant gas sent to the refrigerant compressor 1, and the valve opening degree control amount is determined by the three pressures PS. , determined by PSPS.

[Problem to be solved by the invention]

Conventional refrigeration and air conditioners are configured as described above, so whether the refrigerant circulation amount is large or small for the same change in heating degree, the valve opening degree of the thermostatic automatic expansion valve 15 will change depending on the heating degree. Therefore, when the amount of refrigerant circulating is small, such as during low-load operation, the valve may be opened too quickly.
For this reason, the pressure, heating degree, etc. of the refrigerant gas sent to the refrigerant compressor 1 change rapidly, making it easy for hunting to occur, and in some cases, the valve opening becomes too large, causing a backflow of refrigerant liquid. There is a risk of this happening, and there are other problems such as it is difficult to prevent such a thing due to the mechanism and operation of the thermostatic automatic expansion valve 15.

This invention was made to solve the above-mentioned problems, and by controlling the valve opening according to the operating load, hunting does not occur even during low-load operation. Another object of the present invention is to obtain a refrigeration and air conditioning system that has good followability even during high-load operation.

[Means to solve the problem]

The refrigeration air conditioner according to the present invention detects the pressure and temperature of the refrigerant gas sent to the refrigeration compressor 1 with a detection means, determines the degree of heating from the difference between the saturation temperature of the refrigerant with respect to the pressure and the above temperature, and determines the degree of heating. A heating degree difference is determined from the heating degree and the target heating degree, and a difference between this heating degree difference and the previous heating degree difference is determined, and the valve opening operation interval of the expansion valve is controlled by the calculation control unit according to this difference. This is how it was done.

(Function) The refrigeration air conditioner according to the present invention changes the valve opening operation interval of the expansion valve according to the difference between the current heating degree difference and the previous heating degree difference, thereby increasing the valve opening per unit time. The manipulated variable is changed, and the control system follows the changing load.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, i, 2.3 correspond to the same reference numerals in FIG. 4, so their explanation will be omitted. Reference numeral 4 designates an expansion valve in place of the thermostatic automatic expansion valve 15 shown in FIG. 4, and an electric expansion valve is used in this embodiment. 5 is a pressure sensor as a detection means consisting of a semiconductor sensor etc. that detects the pressure of the refrigerant gas sent to the refrigeration compressor 1; 6゛ is a temperature sensor as a detection means consisting of a thermistor etc. for detecting the temperature of the refrigerant gas; 7 is a cable for taking out the operating signal of the refrigerant compressor 1; 8 is a control to which the operating signal, pressure detection signal and temperature detection signal are applied, and also controls the electric expansion valve 4.

FIG. 2 shows the configuration of the controller 8, where 9 is an input section to which an operating signal from the refrigeration compressor 1, a pressure detection signal from the pressure sensor 5, and a temperature detection signal from the temperature sensor 6 are applied, and 10 is an input section 9. an A/D converter that converts the pressure detection signal and temperature detection signal sent from the 11 into digital signals;
12 is a storage unit that temporarily stores the digital signals and the operating signal sent from the input unit 9 and also stores the calculation results described later; 12 is a calculation unit that performs a predetermined calculation described below based on the data stored in the storage unit 11; 18 is a valve opening operation timer for setting the interval of valve opening operation of the electric expansion valve 4;
3 is an output section that sends a control signal to the electric expansion valve 4; 14 is an input section 9, an A/D conversion section 10, a storage section 11, an arithmetic section 12, a valve opening operation timer 18, an output section 13, etc.; This is a control unit that performs predetermined operation control at timing. The control unit 14, the calculation unit 12, and the storage unit 11 are connected to the calculation control unit 19.
Configure.

Next, the operation will be explained.

When the refrigerant compressor 1 is driven and its operating signal is applied to the controller 8 through the cable 7, a pressure detection signal and a temperature detection signal are obtained from the pressure sensor 5 and temperature sensor 6 as detection means.

These signals are passed through the input section 9, converted into digital signals by the A/D conversion section 10, and stored in the storage section 11. The calculation unit 12 performs the following calculation based on the detected pressure PS and temperature TS stored in the storage unit 11.

First, the saturation temperature T't's of the refrigerant with respect to the pressure PS is calculated, and then the difference between the temperature TS and the saturation temperature TS is calculated to determine the degree of heating 5=TS Tps. Next, a heating degree difference D between this heating degree S and a target heating degree S0 set in advance by a setting device (not shown) and stored in the storage unit 11
=S-3, and stores this in the storage unit 11. The control section 14 creates a control signal according to the stored heating degree difference, and changes the valve opening degree of the electric expansion valve 4 to D through the output section 13.
=j=0, that is, 30 in S. As a result, when D>O, the valve opening becomes large, when D<0, the valve opening becomes small, and when D is 0, the valve opening is maintained as it is.

In addition to the above valve opening degree control, the time interval T of valve opening degree manipulation is determined as follows. A case will be described in which the heating degree S changes by ΔS and the heating degree difference changes by ΔD when performing the next valve opening degree operation after the previous valve opening degree operation is performed. Heating degree change ΔS which is the result of the previous valve opening degree operation
When is extremely small and Δ3+Q, that is, when the difference in heating degree hardly changes and is O in D, when ID1>>0,
Shorten the interval T between the next valve opening operations. On the contrary, ΔS is large and ΔD4-0. When IΔDl>>0 and the positive or negative sign of D is reversed, that is, when it changes from S>So to S<S or from S<So to S>S, the next valve opening is Increase the interval T between operation.

In addition, in cases other than the above, that is, D'FO, lΔD1〉〉O
When there is no reversal of the sign of D, or when ΔD is 0, IDI>
>0, the interval T of valve opening operation is not changed.

The valve opening degree operation timer 18 is set based on each T determined in this way. In addition, ID is 0 in ΔD mentioned above.
The state of I>>O means that in high-load operation, if the control amount ΔV of the electric expansion valve 4 at one time for a certain heating degree difference is fixed, D will be controlled to O unless T is shortened. This is a situation where it is difficult to do so. Further, a state in which the sign of D is reversed is an operating state in which hunting will occur if T is not made long during low-load operation.

FIG. 3 shows a controller 8 for carrying out the above-mentioned operations.
A flowchart of the signal processing performed in is shown. First, in step 5T(1), predetermined data such as pressure P3+temperature TS are input. These data are stored in the storage unit 11 after the pressure detection signals and temperature detection signals from the pressure sensor 5 and temperature sensor 6 are converted into digital signals by the A/D conversion unit 10 via the input unit 9. It is obtained by

Next, in step 5T(2), an operation signal from the refrigeration compressor 1 is waited for. While the operation signal is not received, the valve opening operation timer 18 is reset in step 5T(3), and then step 5T
Return to (1) and step 5T (1), 5T (2), 5T
(3).

The routine of 5T(1) is repeated. Next, when the operation signal is input, the process proceeds to step 5T(4), where it is determined whether the valve opening degree operation timer 18 has counted up.

When the valve opening operation timer 18 does not count up,
Return to step 5T(1) and input data and step 5
Repeat the operation signal input determination routine in T(2).

When the valve opening degree operation timer 18 counts up, proceed to step 5T(5) to calculate the heating degree S, then calculate the heating degree difference in step 5T(6), and then proceed to step 5T(7) to calculate the heating degree S. , the current heating degree difference and the previous heating degree difference D
Find the change ΔD in the difference from L. Next, this obtained Δ
It is determined in step 5T(8) whether D is 0 within ΔD. If D+O, step S T (9
), it is determined whether IDI>>O. IDI>
If >0, in step 5TQO), the valve opening operation timer 18 is set to T, which is shorter than the previous valve opening operation interval T. If IDI>>O, in step 5TOD,
Set the valve opening degree operation timer 18 to T, the same as last time. If ΔD4-O is not determined in step 5T(8), the process proceeds to step 5TO2), where it is determined whether the sign of D has been inverted. If the sign of D is inverted, step 5
At TQ3), the valve opening degree operation timer 18 is set to a longer T than the previous time. If the sign of D is not reversed, step 5T
(At step 10, set the valve opening operation timer 18 to the same T as last time. Step ST (5) to step 5TQ3)
The series of processes up to this point are performed in the calculation section 12, and the calculation results are temporarily stored in the storage section 1. Finally step 5T
Q4) sends a control signal corresponding to the valve opening operation interval T stored in the storage section 11 to the electric expansion valve 4 through the output section 13 to control the valve opening operation interval. The operations from step 5T(1) to step 5T(14) described above are repeated many times at the cycle of controlling the valve opening while the refrigeration air conditioner is operating.

In the above embodiment, a thermistor is used as the temperature sensor 6, but a platinum resistance thermometer, a thermocouple, or the like may also be used.

[Effects of the Invention] As described above, according to the present invention, the heating temperature difference calculated based on the pressure and temperature of the refrigerant gas sent to the refrigerant compressor by the calculation control unit and the previously calculated heating temperature difference Since the valve opening operation interval T of the expansion valve is controlled according to the change due to the difference from DL, it has good followability to fluctuations in operating load, and especially during low-load operation, there is no sign of hunting. It is possible to reliably capture the occurrence of hunting and prevent hunting, which has the effect of providing excellent stability and safety.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a refrigeration air conditioner according to an embodiment of the present invention, FIG. 2 is a block diagram showing the configuration of a controller in the device, FIG. 3 is a flowchart showing the operation of the device, and FIG. 4 is a block diagram showing the configuration of a controller in the device. It is a block diagram showing a conventional refrigeration air conditioner. 1 is a refrigerant compressor, 4 is an electric expansion valve, and 5 is a pressure sensor (
6 is a temperature sensor (detection means), 8 is a controller, and 19 is an arithmetic control section. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. 1 Valley certain pressure, resistance ゛ 2nd: ) 9:1 No. j1 leaf ・199 Figure 3

Claims (1)

[Claims] In a refrigeration air conditioner that controls a refrigerant flow rate by controlling the opening degree of an expansion valve, a detection means for detecting a temperature T_S and a pressure P_S of refrigerant gas sent to a refrigerant compressor; Based on this, the saturation temperature T_P_S of the refrigerant with respect to this pressure P_S is calculated, the heating degree S is calculated from the difference between this saturation temperature T_P_S and the above temperature T_S, and the heating degree S and the preset target heating degree S_0 are calculated. A heating degree difference D is calculated from the difference, a change amount ΔD due to the difference between this heating degree difference D and the heating difference D_L obtained at the previous detection is calculated, and the valve opening of the expansion valve is calculated according to this change amount ΔD. 1. A refrigeration and air conditioner comprising: a calculation control unit that controls frequency operation intervals.