JPH05133618A - Air conditioner - Google Patents

Abstract

PURPOSE:To stabilize refrigerating cycle over the whole range of capacity control for a compressor by providing two kinds of electric expansion valves which have different refrigerating capacities in an air conditioner that controls the degree of throttling of refrigerating cycle by electric expansion valve. CONSTITUTION:The refrigerating cycle of an air conditioner is constituted of a compressor 1, four-way valve 2, heat exchangers 3, 4, electric expansion valves 5,6, and accumulator 7. A control section 8 controls the compressor 1, electric expansion valves 5,6 based on the information of a pressure sensor 9 and temperature sensor 10. In this case the expansion valve 5 has a larger refrigerating capacity than the expansion valve 6. When the flow rate of the coolant decreases by the control of compressor capacity and a small degree of opening is required for the electric expansion valve, control is carried out by using the electric expansion valve 6 which has smaller refrigerating capacity, and when a large coolant flow rate is required and a large degree of opening is required for electric expansion valve, control is made by using the electric expansion valve 5 of larger refrigerating capacity or both of the electric expansion valves. A stable refrigerating cycle that is stable over the whole range of capacity control for the compressor is thereby realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner for controlling the degree of refrigeration cycle throttling by means of an electric expansion valve.

[0002]

2. Description of the Related Art In a conventional device, as described in Japanese Patent Laid-Open No. 56-44567, the throttle degree is controlled by one electric expansion valve for one refrigeration cycle.

[0003]

In the above-mentioned prior art, since the influence of the opening difference of the electric expansion valve on the refrigeration cycle is greater in the small opening range than in the large opening range, air conditioning is performed. There is a problem that it is not possible to control with the same accuracy over the entire capacity control range of the compressor of the device.

An object of the present invention is to realize a stable refrigeration cycle over the entire capacity control range of the compressor by reducing the influence of the opening deviation in the small opening range of the electric expansion valve. .

[0005]

In order to achieve the above object, two kinds of electric expansion valves having different refrigerating capacities are provided in one refrigerating cycle, and the compressor capacity is controlled by an air conditioning load to be predetermined. If the value is less than or equal to a predetermined value, the smaller capacity of the expansion valves is used for control, and if the capacity of the compressor exceeds the specified value, the larger capacity is used to control the refrigeration cycle. I do.

Alternatively, when the required opening degree of the electric expansion valve for controlling the degree of throttling in the decompression section of the refrigeration cycle to be an appropriate value is less than or equal to a predetermined value, the two types of electric Control is performed using the smaller capacity of the expansion valves, and if the required opening of the electric expansion valve exceeds a specified value, use both large capacity and small capacity electric expansion valves. Control and fine-tune the throttling degree with a small capacity electric expansion valve.

[0007]

As described above, when the compressor capacity is controlled to be small by the air conditioning load, the electric expansion valve having a small capacity can control the throttling degree for accurate control, resulting in a large air conditioning load. When a large amount of refrigerant is required, a large amount of refrigerant can be circulated by a large capacity electric expansion valve.

Alternatively, in controlling the throttle degree in the refrigeration cycle, when the refrigerant circulation amount is small and the electric expansion valve needs to be controlled in a small opening range, the required expansion valve opening amount is By using the fact that the value becomes equal to or less than the predetermined value set in advance as a judgment factor, the electric expansion valve having a small capacity is used to control the throttling degree, whereby the control can be performed accurately.
Further, when the required expansion valve opening amount exceeds a predetermined value, a large capacity electric expansion valve is used in combination with a small capacity one to secure the necessary refrigerant circulation amount,
By finely adjusting the degree of throttling using an electric expansion valve having a small capacity, accurate control can be achieved.

[0009]

Embodiments of the present invention will be described below with reference to FIGS.

FIG. 1 shows the structure of a refrigerating cycle of an air conditioner, FIG. 2 shows flow characteristics of an electric expansion valve having two kinds of refrigerating capacities, and FIG. 3 shows control in the first embodiment. FIG. 4 is a diagram showing switching of the expansion valve at the time, and FIG. 4 is a diagram showing a refrigerant flow rate characteristic at the time of controlling the expansion valve in the second embodiment.

<First Embodiment> As shown in FIG. 1, a compressor 1, a four-way valve 2, heat exchangers 3 and 4, electric expansion valves 5 and 6, and an accumulator 7 are connected by pipes to form an air conditioner. As a refrigeration cycle. The capacity of the compressor 1 can be controlled by changing the input frequency, and is controlled by the control unit 8 according to the air conditioning load. The heat exchangers 3 and 4 act as a condenser or an evaporator by switching the four-way valve 2, and cooling or heating operation is performed.
Regarding the electric expansion valves 5 and 6, the control unit 8 detects the discharge pressure of the refrigerant by the pressure sensor 9 and the discharge gas temperature of the refrigerant by the temperature sensor 10, and the discharge pressure is detected by the microcomputer installed in the control unit 8. From the discharge temperature of the refrigerant from the difference between the discharge gas temperature and the condensation temperature, and the target discharge side superheat determined from the compressor operating frequency at that time. The flow rate of the refrigerant is changed by changing the degree of throttling by the expansion valve so as to obtain a target value. FIG. 2 shows the flow rate characteristic of the electric expansion valve. The electric expansion valve described in this embodiment is fully closed at the opening a and can be changed to the opening d. Here, as a feature of the electric expansion valve, there is a tolerance in the flow rate value at a certain expansion valve opening, but the refrigerant flow rate itself is small in the small opening range, and the influence of the flow rate tolerance on the overall flow rate is the large opening range. Tends to be larger than. Therefore, in the small opening range, there may be a flow rate difference that cannot be ignored between the upper limit value and the lower limit value of the tolerance, which may adversely affect the control. Therefore, as shown in FIG. It is desirable not to use the expansion valve at an opening lower than the expansion valve opening b. Further, in the large opening range, control is impossible beyond the upper limit opening d, so it is desirable to set a margin to a predetermined opening c so as not to fall into such a state. Therefore, when using the electric expansion valve, it is necessary to use the expansion valve opening b to c which is in the middle of the entire opening range. However, as in the conventional case, one electric expansion valve for one refrigeration cycle may have to be used beyond the above-mentioned expansion valve use range when the control range of the compressor capacity is wide. Therefore, in this embodiment, as shown in FIG. 2, two types of expansion valves having different flow rate characteristics are arranged in one refrigeration cycle. As shown in FIG. 2, the electric expansion valve 5 has the characteristic of the refrigerant flow rate h at the maximum opening d, and the expansion valve 6 has the characteristic of the refrigerant flow rate g at the maximum opening d as well.
Has a refrigeration capacity greater than 6. In this example,
As shown in FIG. 3, when the frequency of the compressor rises, the frequency becomes jHz.
Until the temperature reaches, the electric expansion valve 6 with a small refrigerating capacity is used, and when the compressor frequency is jHz or higher, the expansion valve 5 with a large refrigerating capacity is used for control, and when the compressor frequency falls, the frequency is iHz. The expansion valve 5 having a large refrigerating capacity is used until it becomes, and the control is performed by switching to the expansion valve 6 having a small refrigerating capacity when the frequency becomes iHz or less. By performing such control, the electric expansion valve is switched to an expansion valve having an appropriate refrigeration capacity in accordance with the capacity of the compressor, so that it is possible to control in the middle part of the entire opening range of the expansion valve, It is possible to control with high accuracy over the entire compressor capacity control range.

<Second Embodiment> The structure of the refrigeration cycle in this embodiment is the same as that in the first embodiment.
In the present embodiment, as shown in FIG. 4, two electric expansion valves having different refrigerating capacities are used in a range where the compressor capacity is small and the refrigerant flow rate is small, so that only the expansion valve 6 having the smaller refrigerating capacity is used for the refrigerant flow rate e. The range from to f is controlled between the expansion valve openings b to c. When the compressor capacity is large and a large refrigerant flow rate is required for the refrigeration cycle, the amount up to the refrigerant flow rate j is shared by instructing the expansion valve 5 having the larger refrigeration capacity to the expansion valve opening i. The flow rate is changed by the expansion valve 6 having a small refrigerating capacity from the opening degree b'to the c'and shared. In FIG. 4, the shaded portion indicated by k indicates the refrigerant flow rate adjustment range by the expansion valve 6, and the shaded portion indicated by l indicates the amount of cold electricity that can be flowed by using the expansion valve 5. In this way, depending on the required refrigerant flow rate, the two types of electric expansion valves can be used separately for fine adjustment of the refrigerant flow rate and for sharing the basic flow rate. It is possible to control the entire area with high accuracy.

[0013]

According to the present invention, in the air conditioner for controlling the throttle degree of the refrigeration cycle by the electric expansion valve,
By reducing the influence of the opening deviation in the small opening range of the expansion valve, it is possible to realize a stable refrigeration cycle over the entire capacity control range of the compressor.

[Brief description of drawings]

FIG. 1 is a refrigeration cycle system diagram of an air conditioner.

FIG. 2 is a characteristic diagram of a flow rate of an electric expansion valve.

FIG. 3 is an explanatory diagram of expansion valve control in the first embodiment.

FIG. 4 is an explanatory diagram of expansion valve control in the second embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Compressor, 2 ... Four-way valve, 3 ... Heat exchanger, 4 ... Heat exchanger, 5 ... Electric expansion valve, 6 ... Electric expansion valve, 7 ... Accumulator, 8 ... Control part, 9 ... Pressure sensor, 10 ... Temperature sensor.

Claims (1)

[Claims] 1. An air conditioner comprising a compressor, a condenser, and an evaporator capable of controlling the capacity, and comprising an electric expansion valve as a pressure reducing device to constitute a refrigeration cycle, and two kinds of electric expansions having different refrigerating capacities. An air conditioner characterized by having a valve.