JPH0745976B2 - Refrigeration cycle controller - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigeration cycle control device using an electric expansion valve.

BACKGROUND ART In recent years, as a device for controlling the refrigerant flow rate of a refrigeration cycle,
Development of an electrically driven expansion valve that can be controlled in various ways by a microcomputer is in progress.

An example of the conventional refrigeration cycle control device using the above-described electric expansion valve will be described below with reference to the drawings.

FIG. 4 shows the structure of the refrigeration cycle. In FIG. 4, 1 is a compressor, 2 is a heat exchanger, 3 is an electric expansion valve, 4 is a heat exchanger, 5 is a blow-out temperature sensor for detecting the blow-out temperature, and 6b is an electric type by the signal of the discharge temperature sensor 5. It is a control device that controls the expansion valve 3.

FIG. 5 is a block diagram of the control device. The control device 6b includes a temperature detecting means 7 including a discharge temperature sensor 5 and the like, a target temperature setting means 8 for setting a target value of the discharge temperature according to the operating condition of the refrigeration cycle, an output of the discharge temperature detecting means 7 and a target temperature setting means Temperature comparison means 9 for comparing the outputs of 8 and valve opening calculation means for calculating the valve opening by the output of the temperature comparison means
10. The valve opening output means 15 outputs the valve opening according to the output of the valve opening calculation means.

The operation of the refrigeration cycle and the control circuit configured as described above will be described with reference to FIGS. 7 and 8.

FIG. 7 is a flowchart showing the operation of the electric expansion valve 5, and FIG. 8 shows changes in typical discharge temperature, valve opening of the electric expansion valve 5, and EER of the refrigeration cycle. .

As the operation, first, the temperature difference ΔTd between the discharge temperature Td detected by the discharge temperature detection means 7 including the discharge temperature sensor 5 and the temperature Ts set by the target temperature setting means 8 is calculated by the temperature comparison means 9
Ask in. Then, the valve opening degree according to the temperature difference ΔTd is determined by the valve opening degree calculation means 10, and the valve opening degree output means 15 changes the opening degree of the electric expansion valve 5. If the discharge temperature Td is significantly different from the target value Ts, the valve opening degree calculation means 10 changes the valve opening degree of the electrically driven expansion valve 5 to a large value.
As Td approaches the target value Ts, the degree of change in the valve opening is reduced, and if the discharge temperature Td falls within the temperature range of the target value Ts ± ΔTh, the valve opening is not changed and the discharge temperature Td is changed to the target value Ts. It is something that tries to get closer to. In addition, the valve opening degree set once is held for a certain period of time.

Problems to be Solved by the Invention However, in the above-described configuration, the target value of the discharge temperature Td is a region having a temperature width of Ts ± ΔTh, and the EER of the refrigeration cycle is the highest, and the target discharge temperature Ts is accurate. Is difficult to approach, and there is a possibility that the discharge temperature Td will bend toward both ends of the temperature range ± ΔTh. These have a problem that it takes time until the discharge temperature Td is stabilized by performing the valve opening changing operation again even with a slight disturbance.

In view of the above problems, the present invention provides a highly efficient and highly stable refrigeration cycle that more accurately brings the discharge temperature Td closer to a target value and eliminates unnecessary changes in valve opening even with respect to disturbance. It is an object.

Means for Solving the Problems In order to solve the above problems, the control device of the refrigeration cycle of the present invention has the same temperature detecting means, target temperature setting means, temperature comparing means, and valve opening degree as those of the conventional control device. A calculation means, a valve opening output means, and a new valve opening comparison means, a maximum valve opening storage means, a minimum valve opening storage means, and an average valve opening calculation means are provided in the preceding stage of the valve opening output means. A temperature dead zone generating means is provided.

The present invention has the above-described configuration, and the valve opening degree comparing means detects whether the output of the valve opening degree calculating means is the maximum valve opening degree or the minimum valve opening degree up to the present time. When it is detected that the valve opening at that time is stored in the maximum valve opening storage means, and when it is detected as the minimum valve opening, the valve opening at that time is set to the minimum valve opening. Store in the storage means. Since the maximum value and the minimum value of the valve opening degree occur because the discharge temperature hunts around the target value, the average value of the minimum valve opening degree and the maximum valve opening degree is calculated by the average valve opening degree calculation means. When found, the valve opening degree is the most appropriate valve opening degree for making the discharge temperature the target value, so the discharge temperature can be controlled with high accuracy.

Further, when the output of the average valve opening calculating means is generated, a temperature dead zone for stopping the change of the valve opening is set on the plus side and the minus side of the temperature of the target value, and the temperature dead zone generating means is set to the average valve opening calculating means. By connecting to the outlet of, the discharge temperature does not come out of the temperature dead zone and stable control is possible even if the discharge temperature accurately approaching the target value fluctuates to some extent due to disturbance.

Embodiment Hereinafter, a refrigeration cycle control device according to an embodiment of the present invention will be described.

FIG. 1 is a refrigeration cycle diagram of one embodiment, in which the compressor 1,
The heat exchanger 2, the electric expansion valve 3, and the heat exchanger 4 are connected in an annular shape. The valve opening degree of the electrically driven expansion valve 3 is controlled by the control device 6a which uses the temperature detected by the discharge temperature sensor 5 as an input signal. In the figure, the solid line arrow indicates the flow direction of the refrigerant.

FIG. 2 is a block diagram of the control device 6a. The output of the temperature detecting means 7 and the output of the target temperature setting means 8 are compared by the temperature comparing means 9, and the valve opening degree calculating means 10 determines the valve opening degree according to the output.

The valve opening comparison means 11 detects whether the obtained valve opening is the maximum valve opening up to the present or the minimum valve opening, and when it is detected as the maximum valve opening, then, The valve opening degree is stored in the maximum valve opening storage means 12, and when it is detected as the minimum valve opening degree, the valve opening degree at that time is stored in the minimum valve opening storage means 13. This maximum straightness and minimum value are average valve opening calculating means 14
To the average valve opening ((maximum valve opening + minimum valve opening) /
2) is output from the valve opening output means 15, and at this time, the temperature dead zone generating means 16 generates a temperature dead zone for stopping the change of the valve opening on the plus side and the minus side of the target temperature.

FIG. 3 is a flowchart of the control of this embodiment. Fourth
The figure shows changes in the discharge temperature, changes in the valve opening, and changes in the EER of the refrigeration cycle with respect to the target temperature Ts.

Hereinafter, FIGS. 3 and 4 will be described.

The discharge temperature Td is detected and compared with the target temperature Ts. As a result, when the discharge temperature is low, the valve opening is reduced by ΔP. The valve opening is maintained as it is for Δt time, and the discharge temperature Td and the target temperature Ts are compared again. At this time, the discharge temperature Td is the target temperature Ts
If it is higher, the valve opening is increased by Δp, and the valve opening before the increase is stored as the minimum valve opening (P _MIN ). Similarly, the discharge temperature Td is repeatedly compared with the target temperature Ts every Δt time, and when the discharge temperature Td changes from a state higher than the target temperature Ts to a state lower, that is, the change in the valve opening degree changes from ΔP increase to ΔP decrease. At this time, the valve opening before decreasing by ΔP is set to the maximum valve opening (P _MAX ).

When the maximum valve opening (P _MAX ) and minimum valve opening (P _MIN ) are confirmed, the valve opening is changed to the average value ((P _MAX + P _MIN ) / 2).

Furthermore, when the output of the average valve opening calculation means 14 occurs,
Ts + ΔT on the plus and minus sides of the target temperature Ts
A temperature line of h, Ts-ΔTh is provided, and the detected discharge temperature Td
When Ts + ΔTh or less and Ts−ΔTh or more, the opening degree of the electric expansion valve is not changed.

As a result, the discharge temperature Td can be brought closer to the target temperature Ts faster and more accurately, and a refrigeration cycle with high efficiency and high stability against external disturbance can be realized.

As described above, according to the present invention, the temperature of the predetermined portion of the refrigeration cycle is detected by the temperature detecting means, the output of the target temperature setting means is compared with the temperature comparing means, and the valve is opened according to the output of the temperature comparing means. In the control device that determines the valve opening by the degree calculation means and changes the valve opening of the electric expansion valve by outputting from the valve opening output means, the valve opening comparison means for determining the maximum valve opening and the minimum valve opening,
A maximum valve opening storage means for storing the maximum valve opening and the minimum valve opening, a minimum valve opening storage means, and an average valve opening calculation means for obtaining an average valve opening of the maximum valve opening and the minimum valve opening are provided. Further, when the output of the average valve opening calculation means is generated, a dead zone for stopping the change of the valve opening is provided on the plus side and the minus side of the output of the target temperature setting means, so that the valve for adjusting the discharge temperature to the target temperature is provided. The opening can be calculated as the average valve opening of the maximum valve opening and the minimum valve opening, and the discharge temperature can be brought closer to the target temperature faster and more accurately, and a highly efficient refrigeration cycle can be realized. At the same time, a refrigeration cycle with high stability against disturbance can be realized.

[Brief description of drawings]

FIG. 1 is a refrigeration cycle diagram showing an embodiment of the present invention, and FIG.
FIG. 3 is a block diagram of the control device of the present invention, FIG. 3 is a flow chart showing the control contents of the control device, and FIG. 4 is a time chart showing typical discharge temperature, valve opening degree and EER characteristic in the refrigeration cycle, 5 and 6 are a refrigeration cycle diagram of a conventional example and a block diagram of a control device, FIG. 7 and FIG.
The figure is a flow chart showing the control contents of a conventional example and a time chart showing changes in typical discharge temperature, valve opening, and EER characteristics. 1 ... compressor, 2,4 ... heat exchanger, 3 ... motorized expansion valve, 11 ... valve opening comparison means, 12 ... maximum valve opening storage means, 13 ... minimum valve opening memory Means, 14 ... Average valve opening calculation means, 7 ... Temperature detection means, 8 ... Target temperature setting means,
9: temperature comparison means, 10: valve opening calculation means, 15: valve opening output means, 16: temperature dead zone generation means.

Claims (1)

[Claims] 1. A refrigeration cycle is constituted by a compressor, a heat exchanger, an electric expansion valve, etc., temperature of a predetermined portion of the refrigeration cycle is compared by a temperature detecting means, and the detected temperature and a target of a target temperature setting means. The temperatures are compared by the temperature comparison means, and when the detected temperature is equal to or higher than the target temperature, the electric expansion valve is opened by a certain amount
When the detected temperature is lower than the target temperature, in the control device including the valve opening output means for closing the electric expansion valve by a certain amount, the operation of the electric expansion valve is changed from the opening operation to the closing operation. In this case, the maximum valve opening calculation means that sets the valve opening immediately before the closing operation to the maximum opening, and when the closing operation changes to the opening operation, the valve opening immediately before the opening operation changes to the minimum valve opening. A minimum valve opening calculation means that is an opening, and an average valve opening that determines an average valve opening from the maximum valve opening and the minimum valve opening when the maximum valve opening and the minimum valve opening are determined. And an output of the average valve opening calculation means is output to the valve opening calculation means to maintain the valve opening of the electric expansion valve at the average valve opening and to open the average valve opening. When the output of the temperature calculation means is generated, the target temperature and the temperature detection means Controller outgoing refrigeration cycle temperature dead zone is not carried out a comparison of the temperature is provided to span the positive and negative sides around the target temperature.