JPH06265222A - Expansion valve control device for air conditioner - Google Patents

Abstract

PURPOSE:To improve a performance of an air conditioner by a method wherein a substantial variation of a flow rate control characteristic is prevented or reduced within a region where a degree of opening of an electrical expansion valve is low when the expansion valve is closed by a method wherein there is provided a control device for controlling the expansion valve in such a manner that a valve closing speed in a closing direction is reduced when a degree of opening of the electrical expansion valve is less than a predetermined value. CONSTITUTION:As a temperature (t) of a discharging pipe detected by a temperature sensor 8 is inputted to an opening degree determining means 7 of a control device 70, a degree of opening of an expansion valve 4 corresponding to the detected temperature (t) is selected from a stored related diagram and determined. This degree of opening S is inputted to a comparing means 75 and compared with a set degree of opening S1 inputted from the opening degree setting device 72. When the determined degree of opening S is less than a set degree of opening S1, the comparing means 75 outputs an instruction of a valve closing speed deceleration starting to the speed control means 74. At the speed control means 74, if the expansion valve opening degree is less than S1, a control signal for closing the expansion valve 4 at a lower valve closing speed V1 than a valve opening speed V0 more than S1 is outputted to a pulse motor for the electrical expansion valve 4 through an output means 73.

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 expansion valve in an air conditioner.

[0002]

2. Description of the Related Art FIG. 3 shows an example of a conventional air conditioner. In FIG. 3, 1 is an inverter-driven compressor,
Reference numeral 2 is a four-way switching valve, 3 is an indoor heat exchanger, 4 is an electric expansion valve, and 5 is an outdoor heat exchanger, and these constitute a refrigeration cycle. During the cooling operation, the refrigerant circulates as indicated by the dashed arrow, and during the heating operation the refrigerant circulates as indicated by the solid arrow.

Reference numeral 6 is an inverter for operating the compressor 1 at a frequency corresponding to the load, 8 is a temperature detector for detecting the discharge pipe temperature of the compressor 1, and 7 is an electric type driven by a signal from the temperature detector 8. It is a control device that controls the opening degree of the expansion valve 4.

The opening of the expansion valve 4 is changed according to the discharge pipe temperature t of the compressor 1 detected by the temperature detector 8. As shown in FIG. 4, the expansion valve 4 has a structure in which the needle valve 42 directly connected to the rotor 41a of the pulse motor 41 is rotated to move up and down to change the valve opening. A valve opening / closing signal, that is, a pulse from the control device 7 is input to the coil 41b of.

The rotation angle θ of the needle valve 42 of the expansion valve 4 is proportional to the number n of pulses input to the pulse motor 41, and
The vertical amount of the needle valve 42 also changes in proportion to the pulse number n.

FIG. 5 shows the relationship between the valve opening of the expansion valve 4 constructed as described above, that is, the number of pulses and the flow rate of the refrigerant flowing through the valve opening. As is apparent from FIG. 5, the change ΔQ ₁ in the flow rate per pulse Δn in the low flow rate region is smaller than that ΔQ _{2 in} the high flow rate region.

[0007]

In the above-mentioned conventional apparatus, when the expansion valve 4 is closed at a constant speed and the valve opening becomes less than a predetermined value, the flow control characteristic of the expansion valve 4 changes drastically. However, there is a problem that the discharge pipe temperature t cannot be maintained at the target value. An object of the present invention is to solve the above problems and improve or improve the performance of an air conditioner by preventing or reducing a large change in the flow rate control characteristics in a region where the opening degree of the expansion valve is small during the closing operation of the expansion valve. Especially.

[0008]

The present invention has been invented in order to solve the above-mentioned problems, and its gist is to provide a closing direction when the opening degree of the electric expansion valve is a predetermined value or less. And a control device for controlling the expansion valve so as to reduce the valve closing speed.

[0009]

In the present invention, since it has the above-mentioned structure, when the opening degree of the expansion valve is less than a predetermined value, the valve closing speed in the closing direction is controlled so as to be decreased to make a large change in the flow rate control characteristic. Prevent.

[0010]

1 is a block diagram of an expansion valve control device according to the present invention. The present invention replaces the control device 7 of the air conditioner shown in FIG. 3 with a control device 70 having the function shown in FIG.

In FIG. 1, 71 is an opening determining means for determining the opening of the expansion valve 4 on the basis of the discharge pipe temperature t detected by the temperature detector 8, and 72 is the opening of the expansion valve 4. Is an opening degree setting device for setting, 75 is a comparison means, 74 is a speed control means for controlling the closing speed of the expansion valve 4, and 73 is an output means. The output of the control device 70, that is, the pulse is input to the expansion valve 4 via the control line 13.

During operation of the air conditioner, the discharge pipe temperature t of the compressor 1 detected by the temperature detector 8 is controlled by the controller.
When input to the opening degree determining means 71 of 70, the opening degree determining means 71
Determines the opening degree of the expansion valve 4 corresponding to the detected temperature t by selecting it from the relationship diagram stored in advance.

The opening S of the expansion valve 4 determined by the opening determining means 71 is input to the comparing means 75, where it is compared with the set opening S ₁ input from the opening setter 72. When the determined opening S becomes equal to or less than the set opening S ₁ , the comparison means 75 outputs a valve closing deceleration start command to the speed control means 74.

In the speed control means 74, the expansion valve opening S
_{At 1} or less, as shown in FIG. 2, a control signal for closing the expansion valve 4 at a valve closing speed V ₁ smaller than the speed V _O of the opening of S ₁ or more is electrically operated via the output means 73. Expansion valve 4
Output to the pulse motor 41 of.

[0015] That is, as shown in FIG. 2, when the valve is closed in the expansion valve 4, the opening is closed by the closing speed V _O until S _1, opening the speed V ₁ past the S ₁ Control to slow down. As described above, the expansion valve 4 is controlled by the control device 70 to have an opening degree corresponding to the discharge pipe temperature t determined by the opening degree determining means 71. Then, during the valve closing operation, is slowly allowed closed is regulated to valve closing speed V ₁ was in a predetermined opening S ₁ or less.

That is, in the expansion valve 4, the speed signal of the valve closing speed V ₁ is sent from the speed control means 74 to the pulse motor.
When input to 41, the pulse motor 41 is driven so that the speed corresponding to the speed V ₁ , that is, the time per pulse is extended, and the needle valve 42 is gently rotated. In the present invention, when the opening degree of the expansion valve 4 becomes equal to or less than the predetermined value S _{1 in} the process of closing, the valve closing speed is reduced and the expansion valve 4 is gently closed in the process until the valve is fully closed. It is possible to prevent or reduce a large change in the flow rate characteristic of the valve 4 and improve the performance of the air conditioner.

In the above embodiment, when the expansion valve 4 is closed, the valve is closed at the valve closing speed V ₁ when the opening is less than the predetermined value, but the valve closing speed is gradually increased as the opening becomes smaller. It can also be lowered. Further, when the expansion valve is opened, the valve opening speed can be increased according to the increase in the opening degree.

[0018]

According to the present invention, when the electric expansion valve is closed, the valve closing speed is reduced and the expansion valve is gradually closed at a predetermined valve opening or less, so that the flow rate control is performed as in the conventional case. It is possible to prevent or reduce drastic changes in characteristics,
Therefore, the performance of the air conditioner can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram of a control device according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram of the electric expansion valve in the above embodiment.

FIG. 3 is a system diagram of a conventional air conditioner.

FIG. 4 is a schematic sectional view of a conventional electric expansion valve.

FIG. 5 is a characteristic diagram of the expansion valve.

[Explanation of symbols]

 1 Compressor 2 Four-way switching valve 3 Indoor heat exchanger 4 Electric expansion valve 5 Outdoor heat exchanger 6 Inverter 70 Control device 71 Opening determination means 72 Opening setting device 73 Output means 74 Speed control means 75 Comparison means 8 Discharge pipe Temperature detector

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenichi Miyazawa Kenichi Miyazawa 1-chome, Asahi-cho, Nishibiwajima-cho, Nishikasugai-gun, Aichi Mitsubishi Heavy Industries, Ltd. Air Conditioning Factory

Claims (1)

[Claims] 1. An air conditioner comprising a refrigeration cycle comprising a compressor, an outdoor heat exchanger, an electric expansion valve whose opening is controlled by the temperature of the discharge pipe of the compressor, and an indoor heat exchanger. An expansion valve control device for an air conditioner, comprising a control device for controlling the expansion valve so as to reduce the valve closing speed in the closing direction when the opening degree of the electric expansion valve is equal to or less than a predetermined value.