JPH031049A - Air conditioner - Google Patents

Abstract

PURPOSE:To keep an adequate flow rate of return oil for maintaining a compressor under good operating conditions even when the operating capacity of the compressor is changed, by a method wherein in case the time period counted by a timer is more than a specified one, the operating capacity of the compressor is lowered for a certain time period by an operating capacity controller, and the valve lift of an electric expansion valve is increased to a specified value or more for a certain time period by a valve lift controller. CONSTITUTION:When the load on a refrigerant circuit is large and so the operating capacity CP of a compressor 1 becomes large, it is judged whether the operating capacity is less than the pre-set control value CPO or not, and if it is larger than the control value CPO, a timer 10 begins to count the time, and when the accumulated time period T1 becomes larger than the pre-set control value T01, an oil recovery action takes place. That is, the operating capacity CP of the compressor 1 is temporarily reduced by an operating capacity controller 13 and the valve lift of an electric expansion valve 9 is increased by a valve lift controller 14. When the oil recovery action starts, the timer 10 counts the oil recovery time period T2, and when the accumulated time period T2 reaches the oil recovery action maximum limit time period T01, the oil recovery action finishes, the operating capacity CP of the compressor is returned to the original state, and the valve lift of the electric expansion valve is reset to the original state.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a refrigeration cycle and control device for an air conditioner, and in particular, an oil return system for an air conditioner using a compressor with adjustable compression capacity. It is related to.

[Conventional technology] A conventional device of this type is shown in FIG.

In the figure, +11 is the compressor, (2) is the four-way valve, and (3)
is an outdoor heat exchanger, (4) is a pressure reducing device, (5) is an indoor heat exchanger, (6) is an accumulator, and (6a) is configured by drilling a hole in the middle of the outflow pipe of the accumulator (6). The oil return device, ■ and side are the gas side extension piping and the source side extension piping, respectively. There is.

Next, the operation during cooling operation will be explained. Compressor (1
), the discharged high-temperature, high-pressure gas refrigerant flows into the outdoor heat exchanger (3) via the four-way valve (2) and radiates heat to the outdoor air, while the refrigerant condenses and becomes high-pressure. The refrigerant becomes a liquid refrigerant, is depressurized by the pressure reducing device (4), becomes a low-pressure gas-liquid mixed refrigerant, and is supplied to the indoor heat exchanger (5). In the indoor heat exchanger (5), heat is collected from the indoor air for cooling, while the refrigerant evaporates to become a low-pressure gas refrigerant, which is then transferred to the accumulator (6) via the gas side extension pipe αυ and four-way valve port.
). In the Akyemulator (6), the liquid refrigerant and gas refrigerant that were not completely evaporated in the indoor heat exchanger (5) are separated and sucked into the compressor (11).
6) The mixed liquid of refrigerant and refrigeration oil accumulated at the bottom of the compressor (1) is sucked into the compressor (1) through the oil return device (6a), and the amount of oil necessary for lubricating the inside of the compressor (11) is adjusted appropriately. Hold.

Next, the operation during heating operation will be explained. compressor +1
The gas refrigerant is compressed in step 1, and the discharged high-temperature, high-pressure gas refrigerant is supplied to the indoor heat exchanger (5) via the four-way valve (2) and the gas side extension pipe αD, and radiates heat to indoor air for heating. Meanwhile, the refrigerant condenses and becomes a high-pressure liquid refrigerant. This liquid refrigerant flows into the pressure reducing device (4), where it is depressurized and becomes a low-pressure gas-liquid mixed refrigerant, and is supplied to the outdoor heat exchanger (3), where it collects heat from the outdoor air and converts it into a low-pressure gas. It becomes a refrigerant and flows into the accumulator (6) via the four-way valve (2). The Akiemulator (6) separates gas refrigerant and liquid refrigerant as in the cooling operation, and returns the refrigerating machine oil necessary for the compressor (11).

Further, the accumulator (6) has the ability to recover the surplus amount of refrigerant generated due to the difference in the amount of refrigerant required during cooling operation and heating operation. In other words, in the case of the refrigerant circuit configuration shown in Fig. 3, during heating operation, the refrigerant state in the liquid side extension pipe @ is a low-pressure gas-liquid mixed refrigerant, so the amount of refrigerant required is relatively small. During cooling operation, the state of the refrigerant in the light side extension pipe (2) becomes a high-pressure liquid refrigerant, so the specific weight is also large and the required amount of refrigerant increases. Therefore, during heating operation, a large amount of refrigerant liquid remains in the accumulator (6). This stagnant surplus refrigerant amount is
The number increases as the piping length increases.

The flow rate of the mixture of liquid refrigerant and refrigerating machine oil flowing into the compressor (1) via the oil return device (6a) is simply determined by the pressure equation shown below.

Δ Pl + Δ Pt - ΔP3 ΔPI: Loss generated when the gas refrigerant flows into the Akiem outflow pipe and pipe friction loss in the outflow pipe ΔP8: Liquid column pressure due to the liquid level height inside the Akiem unit, ΔP: Oil return device (Kiri In other words, the faster the flow rate of the gas refrigerant, the larger ΔP becomes, and the larger the amount of surplus refrigerant inside the Akiemulator (6), the larger PI becomes. 6a) The differential pressure before and after increases, resulting in an increase in the flow rate of the mixed liquid.

[Problem to be solved by the invention]

As mentioned above, in conventional air conditioners, Akiemulator (
Since it uniquely constitutes the oil return device (6a) in 6),
When the load is heavy (or the amount of refrigerant circulated is large), the amount of oil discharged from the compressor increases, which can lead to a lack of oil in the compressor, leading to failure.

In addition, when the compressor (1) used in the air conditioner is of a variable capacity type, the capacity control range of the compressor becomes wider, the amount of oil discharged under heavy loads is significant, and oil shortage conditions are also noticeable. become.

In addition, if you just want to increase the amount of oil returned, you can make the drill hole of the accumulator oil return device (6a) larger, but in that case, the refrigerant from the accumulator will be easily sucked into the pressure machine in a liquid state, and the liquid There is a possibility of compressor failure due to compression.

This invention was made to solve this problem, and is an air conditioner that maintains a good operating condition of the compressor by ensuring an appropriate amount of oil return even if the operating capacity of the compressor changes. The purpose is to obtain.

[Means to solve the problem]

In the air conditioner according to the present invention, the operating capacity of the compressor is reduced by a predetermined time when the measured time is greater than or equal to a predetermined value, using a timing means that measures when the operating capacity of the compressor is greater than or equal to a predetermined value. At the same time, the valve opening degree of an electric expansion valve connected between the bottom of the accumulator and the suction pipe of the compressor is set to a predetermined value or more.

[Effect]

In this invention, when the operating capacity of the compressor continues to be at or above a predetermined value for a predetermined time or more, the operating capacity of the compressor is reduced for a predetermined time, and the suction pipe of the compressor is opened from the bottom of the Akiemulator for a predetermined time. Since the opening of the electric expansion valve connected between A reasonable amount can be secured.

〔Example〕

FIG. 1 is an overall configuration diagram of an air conditioner according to an embodiment of the present invention. In FIG. 1, fl), +21, +
31.

(41 (51, (61, and OD, @ are the same as the air conditioner shown in Figure 3, (7) is the suction pipe, (8
) is an oil return circuit connected between the accumulator (6) and the suction pipe (7), and (9) is an electric expansion valve that controls the flow of refrigerant in the oil return circuit; A timing means for timing when the operating capacity of the machine is above a predetermined value, α is an operating capacity control means for the compressor, and (b) is a valve opening degree control for controlling the valve opening degree of the electric expansion valve (9). It is a means.

In addition, the solid line arrow in the figure indicates the refrigerant flow direction during cooling operation.
The broken line arrow indicates the refrigerant flow direction during heating operation.The refrigerant flow during cooling operation and heating operation is exactly the same as that of the conventional air conditioner shown in Fig. 3, so the explanation will be omitted. ! The operation during rotation will be explained.

Figure 2 shows the operating capacity control means Q31 and the valve opening control means.

It is a flowchart which shows the control state of the time measurement means O1.

Step a! When the operation starts at step 9, the compressor controls the operating capacity according to the operating condition, and the electric expansion valve (9) connected from the bottom of the accumulator to the middle of the suction pipe of the compressor is opened. The temperature is increased or decreased depending on the operating capacity of the compressor.

In other words, if the operating capacity of the compressor is large (the amount of oil discharged is large), the valve opening degree is set large to increase the amount of oil returned; The opening degree is set small to reduce the amount of oil returned.In this way, oil is returned to the compressor using the oil return device (
6a) and an oil return circuit (8) consisting of the electric expansion valve.
It consists of

In such a refrigerant circuit, when the load is large and the operating capacity C2 of the compressor becomes large, the preset control value C2 increases.
It is determined in step O1 whether or not the angle is 2° or less, and the control value C, is determined.

If this is the case, the timer Ql starts counting the time, and if the cumulative time T1 reaches a preset control value 701 or more in step αη, the oil recovery operation shown in step Qll is performed, that is, temporary compression. When the oil recovery operation starts, which reduces the operating capacity C9 of the machine and increases the opening degree of the electric expansion valve, the timer α counts the oil recovery time T2, and in step Ql the accumulated time is counted. T3
is the maximum regulation time T for the predetermined oil recovery operation. 8, as shown in step (to), the oil recovery operation is ended, the compressor operating capacity C2 is returned to the initial state, and the valve opening of the electric expansion valve is also reset to the initial state.

In other words, in the refrigerant circuit according to this embodiment, if the operating capacity of the compressor is large (and the amount of oil discharged from the compressor increases, and the amount of oil in the compressor becomes insufficient), - In addition to reducing the operating capacity and suppressing the oil discharge amount, the valve opening degree of the electric expansion valve (9) is increased, and the
) is configured to recover oil from

Furthermore, after the oil recovery operation is performed for a certain period of time to ensure the amount of oil, the normal operating state is restored.

〔Effect of the invention〕

Since this invention is configured as described above, it produces the effects described below.

The valve opening of the electric expansion valve in the oil return circuit is controlled according to the operating capacity of the compressor to ensure the amount of oil returned, but the valve opening is determined solely by the operating capacity. Driving capacity it h<
If the valve opening is set large when the oil discharge amount is large, more refrigerant will return to the compressor, making it impossible to cope with transient liquid back-up conditions, causing liquid compression, and causing the compressor to shut down. There was a risk of failure, and the load was a corresponding load considering unit variations. However, in the control of the present invention, if the operating capacity of the compressor continues to be at or above a predetermined value for a predetermined period of time, the compression reduce the operating capacity of the machine,
By suppressing the amount of oil discharged, increasing the valve opening of the electric expansion valve, and performing an oil recovery operation to recover oil from the accumulator, the compressor will never run out of oil and will not malfunction. Improves reliability.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of an air conditioner according to an embodiment of the present invention, FIG. 2 is a control flowchart regarding the oil recovery operation of this air conditioner, and FIG. 3 is a diagram of a fleet configuration of a conventional air conditioner. . In the figure, +11 is a compressor, (2) is a four-way valve, (3) is an outdoor heat exchanger, (4) is a pressure reducing device, and 5) is an indoor heat exchanger.
(6) is an accumulator, (7) is an oil return circuit, (9) is an electric expansion valve, aS is a timing means, (l is an operating capacity control means, and (14) is a valve opening degree control means. The same reference numerals in each figure indicate the same or equivalent parts. Agent Masuo Oiwa Figure 2 Figure 3

Claims (1)

[Claims] A refrigerant circuit consisting of a compressor with adjustable compression capacity, a four-way valve, an outdoor heat exchanger, a pressure reduction device, an indoor heat exchanger, and an accumulator, and a suction side of the compressor from the bottom of the accumulator through an electric expansion valve. an oil return circuit pipe-connected to the compressor, an operating capacity control means for controlling the operating capacity of the compressor, a valve opening degree control means for controlling the valve opening degree of the electric expansion valve provided in the oil return circuit, and the compressor. and a timer for timing when the operating capacity of the compressor is equal to or greater than a predetermined value, and when the time measured by the timer is equal to or greater than the predetermined time, the operating capacity control means controls the compressor for a predetermined time. An air conditioner characterized in that the operating capacity is reduced and the valve opening degree of the electric expansion valve is kept at a predetermined value or more for a predetermined time by the valve opening degree control means.