JPH07117306B2 - Air conditioner - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement of an oil return device in a refrigerant circuit used in an air conditioner, and particularly to a compressor capable of performing capacity control operation in a good state. The purpose is to drive in.

<Prior Art> Conventionally, there is an apparatus of this type shown in FIG. In the figure, (1) is a compressor, (2) is a four-way valve, (3) is an outdoor heat exchanger, (4) is a decompressor, (5) is an indoor heat exchanger, (6) is an accumulator, and (6a). ) Is an oil return device constructed by forming a drill hole in the outflow pipe of the accumulator (6), and (11) and (12) are a gas side extension pipe and a liquid side extension pipe, respectively. In the figure, solid arrows indicate the refrigerant flow direction during the cooling operation, and dashed arrows indicate the cooling flow direction during the heating operation.

Next, the operation during the cooling operation will be described. The high-temperature and high-pressure gas refrigerant that has been compressed and discharged by the compressor (1) flows into the outdoor heat exchanger (3) through the four-way valve (2) and radiates heat to the outdoor air, while the refrigerant is It is condensed to become a high-pressure liquid refrigerant, is decompressed by the decompression device (4), becomes a low-pressure gas-liquid mixed refrigerant, and is supplied to the indoor heat exchanger (5) through the liquid side extension pipe (12). In the indoor heat exchanger (5),
While collecting heat from room air to cool it, the refrigerant evaporates into a low-pressure gas refrigerant, which flows into the accumulator (6) through the gas side extension pipe (11) and the four-way valve (2). In the accumulator (6), the liquid refrigerant and the gas refrigerant that have not completely evaporated in the indoor heat exchanger (5) are separated to separate them from the compressor (1).
While sucking into the compressor (1) through the oil return device (6a), the mixed liquid of the refrigerant and the refrigerating machine oil accumulated at the bottom of the accumulator (6) is sucked into the compressor (1) for lubrication. Keep the required amount of oil properly.

Next, the operation during the heating operation will be described. The high-temperature high-pressure gas refrigerant discharged by compressing the gas refrigerant in the compressor (1) is supplied to the indoor heat exchanger (5) through the four-way valve (2) and the gas side extension pipe (11), While radiating heat to the air to heat it, the refrigerant condenses into high-pressure liquid refrigerant.
This liquid refrigerant flows into the pressure reducing device (4) through the liquid side extension pipe (12), is reduced in pressure by the pressure reducing device (4), becomes a low-pressure gas-liquid mixed refrigerant, and is supplied to the indoor heat exchanger (3), Heat is taken from the outdoor air, becomes a low-pressure gas refrigerant, and flows into the accumulator (6) through the four-way valve (2). The accumulator (6) separates the gas refrigerant and the liquid refrigerant, while returning the refrigerating machine oil necessary for the compressor (1), as in the cooling operation.

Further, the accumulator (6) has a function of recovering the excess refrigerant amount generated due to the difference between the refrigerant amounts required during the cooling operation and the heating operation. That is, in the case of the refrigerant circuit configuration as shown in FIG. 5, during the cooling operation, the refrigerant state in the liquid side extension pipe (12) is a low-pressure gas-liquid mixed refrigerant, so that the required refrigerant amount is relatively small. On the other hand, during heating operation, the refrigerant state in the liquid side extension pipe (12) becomes high pressure liquid refrigerant,
The specific weight is large and the required amount of refrigerant is large. Therefore, during the cooling operation, a large amount of the refrigerant liquid stays in the accumulator (6). This stagnant amount of excess refrigerant is
The larger the pipe lengths of 1) and (12), the larger.

The mixed liquid flow rate of the liquid refrigerant and the refrigerating machine oil flowing into the compressor (1) via the oil return device (6a) fluctuates so as to simply satisfy the following pressure equation.

ΔP ₁ + ΔP ₂ = ΔP ₃ ΔP ₁ : Loss that occurs when the gas refrigerant flows into the accumulator outflow pipe and the pipe friction loss in the outflow pipe ΔP ₂ : Liquid column pressure due to the height of the liquid surface in the accumulator ΔP ₃ : The oil return device (Differential pressure before and after drilling) That is, ΔP ₁ increases as the flow velocity of the gas refrigerant increases, and ΔP ₂ increases as the amount of excess refrigerant liquid inside the accumulator (6) increases. The differential pressure ΔP ₃ across the oil device (6a) increases, resulting in an increase in the mixed liquid flow rate. Therefore, during the cooling operation, a larger amount of the mixed liquid flows into the compressor (1) than during the heating operation.

[Problems to be Solved by the Invention]

As described above, in the conventional air conditioner, the oil return device (6a) of the accumulator (6) is uniquely configured,
If the excess refrigerant liquid in the accumulator (6) is large,
The oil return capacity of the oil return device (6a) becomes excessively large, and as a result, the amount of liquid back flowing into the compressor (1) increases, causing failure of the compressor (1) or causing the compressor (1) to fail. There was a problem that operating efficiency was reduced. As described above, it is possible to reduce the size of the drill hole of the oil return device (6) in order to avoid excessive liquid back, but in this case, the excess refrigerant liquid in the accumulator (6) is small. In this case, there is a problem that a sufficient oil return capacity cannot be obtained, a large amount of refrigerating machine oil is stagnated in the accumulator (6), and the compressor (1) is not sufficiently lubricated to cause an accident. Furthermore, since the discharge gas temperature is likely to rise and an appropriate amount of liquid back is not ensured during high compression ratio operation, the discharge gas temperature overheats, which adversely affects the life of the air conditioner.

When the compressor (1) used in the air conditioner is of a variable capacity type, the range of the gas flow velocity becomes wide, and when the gas flow velocity is small, it is generated by the excess refrigerant liquid in the accumulator (6). As the influence of the liquid column pressure ΔP ₂
If the oil return device (6a) is selected for high-capacity operation, extreme liquid back will occur during small-capacity operation.

The present invention has been made in order to solve such a problem, and is not affected by the operating capacity of the excess refrigerant liquid in the accumulator (6) and the compressor (1), and has a proper liquid level and a sufficient amount of oil return. To maintain the operating condition of the compressor (1) in good condition.

[Means for Solving the Problems]

An air conditioner according to the present invention has a compressor capable of adjusting a compression capacity, a four-way valve, an outdoor heat exchanger, a pressure reducing device, an indoor heat exchanger, and a refrigerant circuit in which an accumulator is pipe-connected,
In an air conditioner that performs capacity control, a suction pipe that connects the accumulator and the compressor, an oil return device that connects the bottom of the accumulator, and a pipe connection in parallel with the oil return device, and the flow rate is continuously controlled. Flow control device, operating capacity control means for controlling the operating capacity of the compressor, and valve opening control means for controlling the valve opening of the flow control device according to the operating capacity by the operating capacity control means. And the valve opening of the flow rate control device is increased in accordance with an increase in the operating capacity of the compressor.

Further, the discharge temperature detecting means provided in the discharge pipe connecting the compressor capable of adjusting the compression capacity and the four-way valve, and the time measuring means for measuring the time when the temperature detected by the discharge temperature detecting means is outside the predetermined temperature range are provided. When the time measuring means measures the time outside the predetermined temperature range for a predetermined time, the valve opening control means corrects the valve opening of the flow rate control device.

Further, by comparing the cooling operation and the heating operation, the reference valve opening degree of the flow control device in the operation mode in which the excess refrigerant amount in the accumulator increases is smaller than the reference valve opening degree in the operation mode in which the excess refrigerant amount decreases. It was done.

[Action]

According to the present invention, the valve opening degree of the flow rate control device is increased according to the increase of the operating capacity of the compressor. Further, when the discharge temperature is out of the set temperature range for a predetermined time, the valve opening of the flow rate control device is corrected. Also, when the amount of surplus refrigerant in the accumulator changes depending on the operation mode, the reference valve opening of the flow rate control device is changed accordingly.

〔Example〕

FIG. 1 is an overall configuration diagram of an air conditioner according to an embodiment of the present invention. In the figure, (1) (2) (3) (4)
(5), (11) and (12) are the same as those of the conventional air conditioner shown in FIG. (6) is an accumulator, and the outflow pipe is located in the upper part. Reference numeral (7) is an oil return device connected to the bottom of the accumulator (6) and the suction pipe (10), and is composed of a capillary tube or pipe orifice, and in terms of flow characteristics, the minimum operating capacity of the compressor (1). To match. (8) is an electric expansion valve which is a flow control device connected in parallel with the oil return device (7), and the passing flow rate can be changed by an electric signal. (13) is a discharge temperature detecting means provided in a discharge pipe (9) connecting the compressor (1) and the four-way valve (2), and (23) is a temperature detected by the discharge temperature detecting means (13). Time measuring means for measuring time when the temperature is out of the temperature range, (22) is an indoor heat exchanger (5)
Capacity control means for determining the operating capacity of the compressor (1) according to the temperature state and operating mode in the section, (21)
Is a valve opening degree control means for controlling the valve opening degree of the electric expansion valve (8) based on the output signals of the operating capacity control means (22) and the timing means (23).

In addition, the solid line arrow in the figure indicates the refrigerant flow direction during the cooling operation,
The dashed arrow indicates the direction of refrigerant flow during heating operation. The operation on the refrigerant side during the cooling operation and the heating operation is exactly the same as that of the conventional air conditioner shown in FIG.
The operation of the electric expansion valve (8) will be described.

FIG. 2 is a characteristic diagram for setting the reference opening degree Sa of the electric expansion valve (8) by the valve opening control means (21) according to the operating capacity Q of the compressor (1), and (25) is The reference opening diagram during cooling operation, (26) shows the reference opening diagram during heating operation, and when the operating capacity Q of the compressor (1) is less than a predetermined value, the reference opening Sa
Is set to 0. Like the conventional air conditioner, the flow rate of the mixed liquid of the refrigerant liquid and the refrigerating machine oil flowing through the oil return device (7) and the electric expansion valve (8) is simply enough to satisfy the following pressure formula. Become.

ΔP ₁ + ΔP ₂ = ΔP ₃ ΔP ₁ : Loss generated when gas refrigerant flows into the accumulator outflow pipe and pipe friction loss in the outflow pipe ΔP ₂ : Liquid column pressure due to liquid level in accumulator ΔP ₃ : Returning device (7) or the differential pressure generated before and after the electric expansion valve (8) In other words, as explained in the conventional air conditioner, during the cooling operation, the refrigerant state in the liquid side extension pipe (12) is a low pressure gas-liquid mixture. Since it becomes a refrigerant, a large amount of excess refrigerant liquid is retained inside the accumulator (6), and the liquid column pressure Δ caused by the liquid level height Δ
P ₂ is large. In this state, when the operating capacity Q of the compressor (1) is relatively small, the electric expansion valve (8)
The reference opening Sa of is set to 0, and the mixed liquid of the refrigerant liquid and the refrigerating machine oil is supplied to the compressor (1) only by the oil return device (7),
In addition, the flow path resistance of the oil return device (7) is selected so that the flow rate of the mixed liquid passing through the oil return device (7) becomes appropriate. When the operating capacity Q of the compressor (1) increases, the refrigerant gas flow velocity increases, so the loss ΔP ₁ generated in the outflow pipe of the accumulator (6) increases. As a result, the differential pressure ΔP ₃ generated in the oil return device (7) increases and the flow rate of the mixed liquid increases. However, since the mixed liquid flow rate of the oil return device (7) has characteristics as shown in FIG. 3 with respect to the operating capacity Q of the compressor (1), when the operating capacity Q of the compressor (1) increases. The ratio of the mixed liquid flow rate becomes small and the flow rate becomes relatively insufficient. Therefore, as shown in FIG. 2, the valve opening of the electric expansion valve (8) is increased in accordance with the increase of the operating capacity Q,
The amount of the mixed liquid of the refrigerant liquid and the refrigerating machine oil passing through the electric expansion valve (8) is changed to achieve an appropriate oil return and liquid back amount at any operating capacity Q.

Further, during the heating operation, the state of the refrigerant inside the liquid side extension pipe (12) becomes a high-pressure liquid refrigerant, so that the refrigerant liquid inside the accumulator (6) becomes small and the liquid column pressure ΔP ₂ due to the liquid level height.
Becomes smaller than that during the cooling operation, and the oil return capacity of the oil return device (7) becomes small, so that the flow rate of the mixed liquid of the refrigerant liquid and the refrigerating machine oil becomes small. Therefore, during the heating operation, the reference opening degree Sa of the electric expansion valve (8) is set to be larger than that during the cooling operation as shown in FIG. 2 so that an appropriate amount of oil return and liquid back amount can be obtained. There is.

The adjustment of the amount of oil return and liquid back as described above depends on the amount of surplus liquid in the accumulator (6). Therefore, depending on the outdoor air temperature / indoor air temperature conditions or the length of the extension pipes (11) (12). Since it is assumed that an appropriate value cannot always be set, the discharge temperature detecting means (13) detects the temperature of the discharge pipe (9) that changes depending on the flow rate of the mixed liquid of refrigerant liquid and refrigerating machine oil, and When the time outside the range is measured by the time measuring means (23) and the discharge temperature continues to be equal to or higher than the set temperature for a predetermined time, it is judged that the mixed liquid flow rate is insufficient and the valve of the electric expansion valve (8) is opened. Correct the increase. When the discharge temperature continues to be equal to or lower than the set temperature for a predetermined time, it is determined that the flow rate of the mixed liquid is excessive and the valve opening degree of the electric expansion valve (8) is corrected to be decreased. Note that the above-mentioned valve opening correction amount is different from the above because the rate of change in the mixed liquid flow rate depending on the opening of the electric expansion valve (8) during cooling operation and heating operation is different ( The flow rate changes greatly during cooling operation with a large ΔP ₂ ) It is changed according to the operation mode.

Next, the control state of the valve opening control means (21) of the electric expansion valve (8) of the air conditioner according to this embodiment will be described with reference to the flowchart shown in FIG. In step (41), the compressor (1) is started, and in step (42), the operating capacity control means (22) determines the operating capacity of the compressor (1) to operate at a predetermined operating capacity, and then in step (43). Distinguish between cooling operation and heating operation with the standard opening diagram (25) (26) shown in Fig. 2.
Based on the standard opening degree according to the operating capacity Q of the compressor (1)
Set Sa in step (44) or (45). In step (46), it is judged whether or not the temperature detected by the discharge temperature detecting means (13) is within the predetermined temperature range. If it is within the predetermined temperature range, the timer of the time measuring means (23) is set in step (60). After resetting and proceeding to step (61), the opening correction amount ΔS is set to 0, and the valve opening S of the electric expansion valve (8) is output as the reference opening Sa in step (59). On the other hand, step (4
If the discharge temperature is out of the specified temperature range in 6), proceed to steps (47) and (48), set the timer of the time measuring means (23), and set the time outside the specified temperature range in step (49). It is determined whether or not a predetermined time has elapsed, and if the predetermined time has not elapsed, the valve opening S of the electric expansion valve (8) is left at the reference opening Sa in step (59). If the discharge temperature is outside the specified temperature range and continues for the specified time, step (50)
To reset the timer and proceed to step (51). If the discharge temperature is equal to or higher than the first predetermined temperature, proceed to steps (52) (53) (54). ΔS is set to ΔS ₁ , and the opening correction amount ΔS is set to ΔS during heating operation.
After adding S ₂ , the process proceeds to steps (55) and (59), where the valve opening S of the electric expansion valve (8) is ΔS + Δ with respect to the reference opening Sa.
Increase correction by S ₁ or ΔS + ΔS ₂ . The opening correction amount is ΔS ₁ <ΔS ₂ because the amount of liquid in the accumulator (6) is large during the cooling operation. When the discharge temperature is equal to or lower than the second predetermined temperature (where, the first predetermined temperature> the second predetermined temperature), steps (51) (55) (56)
(57) Go to (58), the opening correction amount ΔS during cooling operation
From ΔS ₁ and from the opening correction amount ΔS to ΔS ₂ during heating operation.
And proceeds to step (59) to correct the valve opening S of the electric expansion valve (8) by ΔS with respect to the reference opening Sa. When the discharge temperature is within the predetermined temperature range during the timer counting, the process proceeds to step (60) at step (46) to set the opening correction amount ΔS to 0 and cancel the correction. If the discharge temperature continues to be outside the planned temperature range, the steps (53) and (54) are performed at predetermined time intervals.
Alternatively, the opening degree correction is repeated by steps (57) and (58).

In this embodiment, the setting of the reference opening Sa and the opening correction amount ΔS is set to be larger during the heating operation than during the cooling operation. However, the air conditioner in which the decompression device (4) is provided on the indoor side is used. In the case of the air conditioner, since the excess refrigerant in the accumulator (6) increases during the heating operation, it is necessary to reduce the reference opening S ₂ and the opening correction amount ΔS ₂ during the heating operation.

Further, in this embodiment, the oil return device (7) is provided outside the accumulator (6). However, like the conventional air conditioner, the oil return device (7) is provided with a drill hole provided in the outflow pipe inside the accumulator (6). May be.

〔The invention's effect〕

A flow rate control device connected in parallel with the oil return device to control the flow rate continuously, operating capacity control means for controlling the operating capacity of the compressor, and the operating capacity control means for operating capacity Since the valve opening control means for controlling the valve opening of the flow control device is provided and the valve opening of the flow control device is increased in accordance with the increase in the operating capacity of the compressor, the compression capacity can be adjusted. Depending on the compression capacity of the compressor, the amount of oil returned to the compressor and the amount of refrigerant liquid can be continuously controlled steplessly, and an appropriate amount of oil return and liquid back amount can be obtained regardless of the operating capacity. The compression capacity control operation is performed well.

Further, when the time measuring means measures the time of the temperature of the discharge pipe being out of the predetermined temperature range for a predetermined period of time, the valve opening control means corrects the valve opening of the flow rate control device to obtain the oil return amount and The liquid back amount can be set to a more appropriate value without being affected by temporary temperature fluctuations.

Further, by setting the reference valve opening of the flow control device in the operation mode in which the excess refrigerant amount in the accumulator increases to be smaller than the reference valve opening in the operation mode in which the excess refrigerant amount decreases, the excess in the accumulator depending on the operation mode. When the refrigerant flow rate changes, the reference valve opening degree of the flow rate control device is changed accordingly, so that an appropriate oil return amount and liquid back amount can be obtained regardless of the operation mode.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an air conditioner according to an embodiment of the present invention, and FIG. 2 is a valve opening characteristic diagram of the same electric expansion valve,
FIG. 3 is a flow rate characteristic diagram of the oil return device, FIG. 4 is a control flow chart by the valve opening control means of the electric expansion valve, and FIG. 5 is an overall configuration diagram of a conventional air conditioner. In the figure, (1) is a compressor, (2) is a four-way valve, (3) is an outdoor heat exchanger, (4) is a decompression device, (5) is an indoor heat exchanger,
(6) is an accumulator, (7) is an oil return device, (8) is an electric expansion valve, (13) is discharge temperature detection means, (21) is valve opening control means, and (22) is operating capacity control means. , (23) is a timekeeping means. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (3)

[Claims] 1. An air conditioner which has a refrigerant circuit in which a compressor capable of adjusting a compression capacity, a four-way valve, an outdoor heat exchanger, a pressure reducing device, an indoor heat exchanger and an accumulator are connected by piping, and which controls a capacity, A suction pipe that connects the accumulator and the compressor, an oil return device that connects the bottom of the accumulator, a pipe connection in parallel with the oil return device, and a flow rate control device that continuously controls the flow rate, and the compression unit. An operating capacity control means for controlling the operating capacity of the compressor, and a valve opening control means for controlling the valve opening of the flow rate control device according to the operating capacity by the operating capacity control means. An air conditioner characterized in that the valve opening degree of the flow rate control device is increased according to the increase. 2. A discharge temperature detecting means provided in a discharge pipe connecting a compressor capable of adjusting a compression capacity and a four-way valve, and a time measuring means for measuring a time when a temperature detected by the discharge temperature detecting means is outside a predetermined temperature range. And, when the time measuring means continuously measures a time outside the predetermined temperature range for a predetermined time,
The air conditioner according to claim 1, wherein the valve opening control means corrects the valve opening of the flow control device. 3. A cooling operation and a heating operation are compared with each other, and a reference valve opening of a flow control device in an operation mode in which the amount of surplus refrigerant in the accumulator increases and a reference valve opening in an operation mode in which the amount of surplus refrigerant decreases. The air conditioner according to claim 1 or 2, wherein the air conditioner has a smaller size.