JP2003294295A - Air conditioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive air conditioner which improves operation efficiency, secure required capacity, and also improves reliability of a compressor even under various operation or construction conditions in cooling operation. <P>SOLUTION: A target discharge temperature is calculated using a saturation temperature of intake pressure estimated with high accuracy at cooling operation, and an electric expansion valve 6 is controlled so that a discharge temperature becomes the target discharge temperature. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to control of a separation type air conditioner in which an indoor unit and an outdoor unit are connected by a connecting pipe.

[0002]

2. Description of the Related Art As a conventional method for controlling the refrigerant circulation amount of a refrigerating cycle by an electric expansion valve in a separation type air conditioner, for example, Japanese Patent No. 2912254 can be cited.

In this conventional example, the target discharge temperature is set on the Mollier diagram by the evaporation temperature, the condensation temperature and the slope characteristic line of the compressor alone, and the motor expansion is performed so that the discharge temperature of the compressor becomes the target discharge temperature. The degree of superheat of the refrigerant is controlled by controlling the refrigerant circulation amount by the valve.

[0004]

By the way, in recent years, from the viewpoint of energy saving and comfort, a separation type air conditioner equipped with an inverter in which the number of revolutions of a compressor greatly changes has become widespread. Also, from the viewpoint of increasing the degree of freedom in installation, the length of connectable pipe is required to be shorter or longer.

However, in such an air conditioner, the refrigerant circulation amount greatly changes due to the inverter, and the connecting pipe length also greatly changes. Therefore, as shown in the pressure loss relationship between the refrigerant circulation amount and the pipe length shown in FIG. The difference between the pressure of the condenser and the pressure on the discharge side of the compressor during heating operation (hereinafter referred to as pressure loss)
Also changes greatly.

As a result, as shown in the Mollier diagram shown in FIG. 5, even if the target discharge temperature is set only by the evaporation temperature and the condensation temperature and the discharge temperature control is performed, the suction point is indicated by ◯ in the figure due to the pressure loss of the connecting pipe. It was difficult to maintain the refrigerant superheat degree on the suction side of the compressor at an appropriate superheat degree.

Generally, if the refrigerant superheat degree on the suction side of the compressor is maintained at an appropriate superheat degree (generally around 5K), the operation efficiency of the compressor is increased and energy saving operation can be performed. However, if the degree of superheat of the refrigerant becomes too large, there arises a problem of insufficient capacity.

On the other hand, if the sucked refrigerant is too wet (the degree of superheat of the refrigerant is not sufficient at all), there arises a problem that the reliability of the compressor such as liquid back is lowered.

Therefore, there is also a method of correcting the target discharge temperature when the degree of superheat of the refrigerant on the suction side, which is detected by the difference between the evaporation temperature and the suction temperature, is out of a predetermined value range.

However, in this method, when the operating condition (for example, the number of revolutions of the compressor) changes, the target discharge temperature can be corrected to correct the refrigerant superheat degree on the suction side, but the working condition ( If the pipe length) changes, the refrigerant superheat on the suction side cannot be corrected.

Therefore, it is necessary for the builder to surely set the actual pipe length with a switch or the like at the time of construction, which causes problems such as an increase in product cost and an increase in construction time.

Therefore, the present invention has been made in view of the above point, and an object thereof is to perform a discharge pressure of a compressor under various operating conditions and construction conditions when performing a heating operation by controlling a discharge temperature. An inexpensive air conditioner that can control the refrigerant superheat on the suction side to a proper superheat by estimating the saturation temperature of the compressor with high accuracy, improve operating efficiency, secure necessary capacity, and improve the reliability of the compressor. Is to provide a machine.

[0013]

In order to solve the above problems, the present invention as set forth in claim 1, is a first variable temperature compressor, an outdoor heat exchanger, and a first temperature detecting device for detecting the temperatures of the outdoor heat exchanger. An outdoor unit having a temperature detecting means and an electric expansion valve whose valve opening can be controlled, and an indoor unit having an indoor heat exchanger and a second temperature detecting means for detecting the temperature of the indoor heat exchanger, In an air conditioner having a connection pipe connecting the outdoor unit and the indoor unit, a storage unit that stores a pipe length of the connection pipe in advance, and a condensation temperature detected by the second temperature detection unit during heating operation. First estimating means for estimating a saturation temperature of a discharge pressure of the compressor based on a pipe length and a rotation speed of the compressor stored in the storage means; and a first estimating means for detecting a discharge temperature of the compressor. 3 temperature detecting means and the first temperature detecting means The target discharge temperature calculating means for calculating the target discharge temperature of the compressor based on the vaporization temperature detected by the above and the saturation temperature of the discharge pressure estimated by the first estimating means, and the opening degree of the electric expansion valve. By controlling the expansion valve control means, the discharge temperature detected by the third temperature detecting means is changed to aim at the target discharge temperature.

As described above, by considering the pressure loss in the condensation temperature, the saturation temperature of the discharge pressure of the compressor can be estimated with high accuracy even if the operating condition changes, and the discharge pressure estimated with the high accuracy can be estimated. Since the target discharge temperature is calculated and the discharge temperature is controlled using the saturation temperature of 1, the actual intake refrigerant superheat degree can be controlled to an appropriate superheat degree with high accuracy even if the operating conditions change.

[0015]

In order to solve the above problems, the present invention according to claim 1 provides a variable temperature compressor, an outdoor heat exchanger, and a first temperature for detecting the temperatures of the outdoor heat exchanger. An outdoor unit having a detection unit and an electric expansion valve whose valve opening can be controlled, an indoor unit having an indoor heat exchanger and a second temperature detection unit that detects the temperature of the indoor heat exchanger, and the outdoor unit. In an air conditioner having a connection pipe connecting an indoor unit and the indoor unit, a storage unit that stores the pipe length of the connection pipe in advance, and a condensation temperature and the storage that are detected by the second temperature detection unit during heating operation. A first estimating means for estimating a saturation temperature of a discharge pressure of the compressor based on a pipe length and a rotation speed of the compressor stored in a means; and a third estimating means for detecting a discharge temperature of the compressor. By the temperature detecting means and the first temperature detecting means Target discharge temperature calculation means for calculating the target discharge temperature of the compressor based on the vaporization temperature that has been discharged and the saturation temperature of the discharge pressure estimated by the first estimation means, and the opening of the electric expansion valve is controlled. By doing
Expansion valve control means for changing the discharge temperature detected by the third temperature detection means, aiming at the target discharge temperature.

Thus, by considering the pressure loss in the condensing temperature, the saturation temperature of the discharge pressure of the compressor can be estimated with high accuracy even if the operating conditions change, and the discharge pressure estimated with the high accuracy can be estimated. Since the target discharge temperature is calculated and the discharge temperature is controlled using the saturation temperature of 1, the actual intake refrigerant superheat degree can be controlled to an appropriate superheat degree with high accuracy even if the operating conditions change.

According to a second aspect of the present invention, the variable capacity compressor, the outdoor heat exchanger, the first temperature detecting means for detecting the temperature of the outdoor heat exchanger, and a plurality of valve opening controllable parts. Of the electric expansion valve, and a plurality of indoor units having an indoor heat exchanger and a second temperature detecting means for detecting the temperature of the indoor heat exchanger are connected in parallel by connecting pipes. In the air conditioner, storage means for storing in advance the pipe length of each connection pipe to each indoor unit, each condensation temperature detected by the second temperature detection means of each indoor unit during heating operation, and The first estimating means for estimating the saturation temperature of the discharge pressure of the compressor based on the pipe length of each connecting pipe and the rotation speed of the compressor stored in the storage means, and the discharge temperature of the compressor A third temperature detecting means for detecting, and the first temperature detecting means. Of the discharge temperature of the compressor based on the evaporation temperature detected by the temperature detecting means and the saturation temperature of the discharge pressure estimated by the first estimating means; Expansion valve control means is provided for changing the discharge temperature detected by the third temperature detection means by aiming at the target discharge temperature by controlling the opening degree.

As described above, even in the multi-type air conditioner, the saturation temperature of the discharge pressure of the compressor can be estimated with high accuracy by considering the pressure loss in the condensation temperature even if the operating conditions change. The target discharge temperature is calculated using the saturation temperature of the discharge pressure estimated with high accuracy and the discharge temperature is controlled.Therefore, even if the operating conditions change, the actual intake refrigerant superheat degree is controlled to an appropriate superheat degree with high accuracy. can do.

Further, according to the present invention, the fourth temperature detecting means for detecting the suction temperature of the compressor, the evaporation temperature detected by the first temperature detecting means and the fourth temperature detecting means. Second estimation means for estimating the suction refrigerant superheat degree of the compressor based on the suction temperature detected by the means, and the discharge temperature detected by the third temperature detection means, the target calculated by the target discharge temperature calculation means. When it is within a predetermined range with respect to the discharge temperature, and the suction refrigerant superheat degree estimated by the second estimating means is out of the predetermined range,
The pipe length previously stored in the storage means is corrected.

As described above, since the pipe length is automatically corrected even when the previously stored pipe length is significantly different from the actually installed pipe length, the pipe length should be close to the actual pipe length each time the correction is performed. become. As a result, the target discharge temperature is corrected, so that the actual superheat degree of the suction refrigerant is corrected to be near the proper superheat degree even if the operating condition or the construction condition changes.

Further, according to the present invention, the abnormality detecting means for notifying the user that the installed pipe length is not appropriate when the pipe length corrected by the pipe length correcting means deviates from the predetermined pipe length. Be prepared.

As described above, when the actually installed pipe length deviates from the proper pipe length and a malfunction of the system is likely to occur, it is possible to inform the user of that fact, and as a result, a serious problem of the system is caused. It is possible to escape damage etc.

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

(Embodiment 1) FIG. 1 is a configuration diagram showing Embodiment 1 of the present invention, in which an outdoor unit 1 and an indoor unit 2 are connected by a connection pipe 8 to form a refrigeration cycle.

In FIG. 1, an outdoor unit 1 is provided with an inverter-driven variable displacement compressor 3 (hereinafter simply referred to as a compressor), an outdoor heat exchanger 5 and a four-way valve 4 for switching between heating and cooling, while indoors. The machine 2 is provided with an indoor heat exchanger 7.
Further, the liquid side main pipe of the outdoor unit 1 is provided with an electric expansion valve 6 whose valve opening can be controlled by, for example, a stepping motor or the like.

In the refrigeration cycle having the above structure, during heating, the refrigerant discharged from the compressor 3 flows from the four-way valve 4 through the gas side pipe of the connecting pipe 8 to the indoor heat exchanger 7, where it is indoors. Connection pipe 8 for heat exchange with air to condense and liquefy
After passing through the liquid side pipe, the pressure is reduced by passing through the electric expansion valve 6 and the refrigerant is easily evaporated, and flows into the outdoor heat exchanger 5 to exchange heat with the outdoor air and evaporate,
It is again sucked into the compressor 3. Further, the rotation speed of the compressor 3 is determined according to the required capacity from the indoor unit 2 (the description is omitted because it is not directly related to the present invention).

Next, a method for estimating the saturation temperature of the discharge pressure of the compressor 3 will be described. First, the first estimating means (microcomputer) estimates the saturation temperature Twd of the discharge pressure by adding the pressure loss equivalent temperature ΔT to the condensation temperature Tc obtained by the indoor heat exchanger temperature sensor 11.

Here, since the refrigerant circulation amount flowing through the refrigeration cycle is substantially proportional to the rotation speed R of the compressor 3, the pressure loss equivalent temperature ΔT is calculated by the rotation speed R of the compressor 3 and the storage means shown in the equation (2). It can be estimated from the length H (for example, 10 m) of the connection pipe 8 stored in the (memory device). Twd = Tc + ΔT (Equation (1)) ΔT = a × R × H + b (Equation (2) a and b are constants In this way, by estimating the pressure loss equivalent temperature with high accuracy. ,
The saturation temperature of the discharge pressure can also be estimated with high accuracy. Here, in order to further improve the estimation accuracy of the pressure drop equivalent temperature ΔT, the square of the rotation speed R or the like may be used for the estimation.

(Second Embodiment) FIG. 2 is a block diagram showing an example of a multi-type air conditioner according to the second embodiment of the present invention. In the case of the multi-type, first estimating means (microcomputer) Is the average pipe length Hr [= (Ha + Hb) / from each pipe length H stored in the storage means.
2] is calculated, and the average rotation speed Rr (= R / 2) of the compressor 3 is calculated.
At the same time, the average pressure loss-equivalent temperature ΔTr per chamber is calculated from the average pipe length Hr and the average rotational speed Rr according to the equation (2).

Then, the average condensing temperature Tcr [= (Tca + Tcb) / 2)] is calculated from the condensing temperature Tc of each indoor unit 2, and the average condensing temperature Tcr and the average pressure drop equivalent temperature ΔTr are calculated from the equation (1). The saturation temperature Twd of the discharge pressure is estimated. As described above, in the multi-type air conditioner, the average pressure loss equivalent temperature is estimated using the average pipe length, so that the overall pressure loss equivalent temperature can be estimated with high accuracy, and as a result, the saturation temperature of the discharge pressure can also be estimated with high accuracy. .

Next, the discharge temperature control for indirectly controlling the superheat degree of the suction refrigerant will be described. First, since the compression principle of the compressor 3 is polytropic compression, the discharge temperature at the proper superheat degree SHm can be calculated using the temperature approximation formula of polytropic compression. Therefore, the target discharge temperature calculating means (microcomputer) uses the evaporation temperature Te detected by the outdoor heat exchanger temperature sensor 10 and the saturation temperature Twd of the discharge pressure of the compressor estimated by the first estimating means to obtain the equation (3). The target discharge temperature Tdm of the compressor 3 is calculated using the temperature approximation formula. Tdm = c × Te + d × Twd + e (Equation (3) c, d, and e are constants, and the expansion valve control means (microcomputer) calculates the discharge temperature Td detected by the discharge temperature sensor 9 and the target discharge temperature Tdm. Based on the deviation DT of the electric expansion valve 6
Is calculated, and the electric expansion valve 6 is controlled every 60 seconds, for example. DT = Td-Tdm (Equation (4)) ΔK = e × DT (Equation (5)) e is a constant In this way, the target discharge is performed using the saturation temperature of the discharge pressure estimated with high accuracy. Since the temperature is calculated and the feedback control is performed, the actual superheat degree of the intake refrigerant can be controlled to the proper superheat degree SHm with high accuracy even if the operating condition changes.

Although the evaporation temperature Te is used in the calculation of the target discharge temperature Tdm, it may be corrected by the outside air temperature or the like to further improve the accuracy.

Although the deviation DT is used as the method for calculating the operating opening ΔK of the electric expansion valve 6, the same effect can be obtained by using a control method such as PID control or fuzzy control.

Next, the refrigerating cycle behavior when the actual installed pipe length and the pipe length stored in the storage means are greatly different will be described. FIG. 5 is a Mollier diagram when the above discharge temperature control is performed, and the cycle indicated by the bold line in FIG. 5 is when the actually installed pipe length is equal to the pipe length stored in the storage means. Shows the refrigeration cycle of.

From here, when the actual pipe length Ht becomes shorter than the pipe length H, the actual discharge pressure becomes a point B (● in the figure) lower than the estimated discharge pressure point A (● in the figure). The superheat degree of the suctioned refrigerant at this time becomes larger than the proper superheat degree SHm.

As a result, problems such as reduced operating efficiency and insufficient capacity are likely to occur. On the contrary, when the actual pipe length Ht becomes longer than the pipe length H, the actual discharge pressure is higher than the estimated discharge pressure A point (● in the figure) and C point (● in the figure).
Therefore, the superheat degree of the suctioned refrigerant at this time becomes smaller than the proper superheat degree SHm. As a result, the problem of lowering the reliability of the compressor, such as a decrease in operating efficiency and liquid back, is likely to occur.

Therefore, the actual installed pipe length H
The discharge temperature control when t and the pipe length H stored in the storage means are significantly different will be described with reference to the flowchart of FIG.

First, in step S1, the pipe length H is set to the initial value 1
The counters M and N are set to 0 while being set to 0 m. In step S2, the timer that counts the control interval (for example, 60 seconds) is reset, and in step S3, the timer is started.

In step S4, the evaporation temperature Te, the condensation temperature Tc, the discharge temperature Td, the compressor speed R, and the suction temperature Ts are read by the suction temperature sensor 12. In step S5, the first estimation means estimates the saturation temperature Twd of the discharge pressure, in step S6 the target discharge temperature calculation means calculates the target discharge temperature Tdm, and in step S7, the second estimation means calculates the equation (6). The intake refrigerant superheat degree SHs is estimated by using this. SHs = Ts−Te (Equation (6)) In step S8, it is determined whether the discharge temperature Td is within ± h ° C (for example, within 1 ° C) of the target discharge temperature Tdm, and Tdm ± h ° C is entered. If so, go to step S9. On the other hand, in step S8, the discharge temperature Td is Tdm ± h
If not within ℃, steps S27, S1
In S6, S17 and S18, the opening degree of the expansion valve 6 is operated by the expansion valve control means so that the discharge temperature Td becomes the target discharge temperature Tdm. In step S19, the timer waits for 60 seconds, and then the process returns to step S2 to perform feedback control.

In step S9, it is determined whether the intake refrigerant superheat degree SHs exceeds the appropriate superheat degree SHm + iK (for example, 3K). If it exceeds, it is considered that the actual pipe length Ht is shorter than the pipe length H, and the step Add 1 to the counter M that counts the number of times determined to be short in S10
At the same time, the counter N that counts the number of times determined to be long is set to 0.

In step S11, it is determined whether the counter M is α or more. If the counter M is α or more, α times (for example, 1
(0 times) Continuously, the superheat degree SHs of the suction refrigerant is the proper superheat degree SHm.
Since it exceeds + iK, it is determined that the actual pipe length Ht is really shorter than the pipe length H, and the pipe length H is corrected to be shorter by j m (for example, 5 m) in step S12.

Since the discharge temperature Td is affected by the heat capacity of the compressor 3 and the evaporation temperature Te and the condensation temperature Tc are stable, they are not immediately stable. It is possible to prevent erroneous determination when the cycle is unstable.

In steps S13 and S14, the saturation temperature Twd of the discharge pressure and the target discharge temperature Tdm are recalculated and corrected using the corrected pipe length H. After resetting the counter M in step S15, steps S16 and S1 are performed.
7, the process proceeds to S18, and the opening degree operation of the expansion valve 6 is performed so that the discharge temperature Td becomes the corrected target discharge temperature Tdm.

Further, in step S9, the degree of superheat of the intake refrigerant SH
If s does not exceed the appropriate superheat degree SHm + iK, the intake refrigerant superheat degree SHs is determined to be the appropriate superheat degree S in step S20.
Hm-i K is determined, and if it is less than Hm-i K, it is considered that the actual pipe length Ht is longer than the pipe length H. Similarly, if α times are consecutive, steps S23, S24, S25, S are performed.
At 26, the pipe length H, the saturation temperature Twd of the discharge pressure and the target discharge temperature Tdm are corrected, and the counter N is set to zero.

On the other hand, in step S20, the intake refrigerant superheat S
If Hs is above the appropriate superheat degree SHm-iK, the actual pipe length H
It is assumed that t is almost close to the pipe length H, and the pipe length H is controlled without correction.

By repeating the correction of the pipe length H as described above, the pipe length H gradually approaches the actual pipe length Ht. As a result, the target discharge temperature shown in FIG. 5 is corrected (broken line in the figure), the suction point of the compressor 3 (◯ in the figure) approaches point D, and even if the construction conditions change, the actual It is possible to correct the suction refrigerant superheat degree to be close to the appropriate superheat degree SHm.

In the case of a multi-type air conditioner, it is necessary to control the total refrigerant circulation amount as well as the individual refrigerant circulation amount to each indoor unit. Therefore, in the case of a multi-type air conditioner, first, the condensing temperature Tcn (n = a or b) of each operating device and the indoor liquid temperature sensor 13 provided in the liquid side pipe of the indoor heat exchanger 7 are detected. Each liquid temperature T
The in-room refrigerant supercooling degree SCn of each operating machine is calculated from ln using the equation (7). SCn = Tcn-Tln (Equation (7)) Then, in step S17, after calculating the operating opening ΔK (the same for all operating machines) of the electric expansion valve 6 of each operating machine, the operating opening ΔK is added. The total opening (Σ (current opening + ΔK)) of the electric expansion valves 6 of all the operated machines is calculated, and each indoor refrigerant supercooling degree SCn is set to the same value while maintaining the total opening. The opening degree of the electric expansion valve 6 is corrected to a new opening degree (new opening degree of Unit a + new opening degree of Unit b = total opening degree), and step S18
By operating the opening of each electric expansion valve 6 at
It is possible to simultaneously control the total refrigerant circulation amount and the individual refrigerant circulation amount to each indoor unit. Since various controls have been proposed and are publicly known in this respect, they are omitted from the flowchart.

In addition, the minimum pipe length Hmin and the maximum pipe length Hmax are specified for the actually installed pipe length in consideration of the reliability of the compressor such as the ratio of the oil and the refrigerant of the compressor 3 and the returning condition of the oil. .

On the other hand, as described above, the actual pipe length Ht can be estimated by the pipe length correcting means. Therefore, the abnormality detecting means (microcomputer) determines whether the pipe length H corrected by the pipe length correcting means is within the proper pipe length from the minimum pipe length Hmin to the maximum pipe length Hmax, and within the proper pipe length. L provided in the indoor unit 2 when it comes off
An ED lamp 20 (not shown) is used to indicate that the installed pipe length is not appropriate.

As a result, it is possible to inform the installer or user that the installed pipe length is not appropriate, and it is possible to prompt correction of the pipe installation. Here, in addition to the LED lamp 20, a buzzer sound, a remote control, or the like may be displayed to inform that the installation pipe length is not appropriate.

As described above, when the actually installed pipe length deviates from the proper pipe length and the system operation is apt to be defective, the system is urged to correct the pipe construction to prevent serious damage to the system. You can escape.

[0052]

Since the present invention is constructed as described above, it has the following effects.

According to a first aspect of the present invention, the variable displacement compressor, the outdoor heat exchanger, the first temperature detecting means for detecting the temperature of the outdoor heat exchanger, and the electric expansion capable of controlling the valve opening degree. An outdoor unit having a valve; an indoor unit having an indoor heat exchanger and a second temperature detecting means for detecting the temperature of the indoor heat exchanger; and a connecting pipe connecting the outdoor unit and the indoor unit. In the air conditioner, a storage unit that stores the pipe length of the connection pipe in advance, a condensation temperature detected by the second temperature detection unit during heating operation, the pipe length stored in the storage unit, and the compressor. First estimating means for estimating the saturation temperature of the discharge pressure of the compressor, third temperature detecting means for detecting the discharge temperature of the compressor, and the first temperature detecting means. Evaporation temperature detected by and the first estimation Aiming at the target discharge temperature by controlling the target discharge temperature calculating means for calculating the target discharge temperature of the compressor based on the saturation temperature of the discharge pressure estimated by the stage and the opening degree of the electric expansion valve. And expansion valve control means for changing the discharge temperature detected by the third temperature detection means.

As described above, the temperature equivalent to the pressure loss is highly accurately estimated based on the pipe length and the rotation speed of the compressor, and the temperature equivalent to the pressure loss is added to the condensation temperature, so that the compressor can be operated under various operating conditions. The saturation temperature of the discharge pressure can always be estimated with high accuracy, and the target discharge temperature of the compressor can be calculated based on the highly estimated saturation temperature of the discharge pressure of the compressor to control the discharge temperature. Thus, it is possible to always control the actual intake refrigerant superheat degree to an appropriate superheat degree under various operating conditions.

As a result, energy-saving operation can be performed, and the problem of reduced reliability of the compressor such as insufficient capacity and liquid back can be avoided.

The present invention according to claim 2 is characterized in that the variable capacity compressor, the outdoor heat exchanger, the first temperature detecting means for detecting the temperature of the outdoor heat exchanger, and a plurality of valves capable of controlling the valve opening degree. Of the electric expansion valve, and a plurality of indoor units having an indoor heat exchanger and a second temperature detecting means for detecting the temperature of the indoor heat exchanger are connected in parallel by connecting pipes. In the air conditioner, storage means for storing in advance the pipe length of each connection pipe to each indoor unit, each condensation temperature detected by the second temperature detection means of each indoor unit during heating operation, and The first estimating means for estimating the saturation temperature of the discharge pressure of the compressor based on the pipe length of each connecting pipe and the rotation speed of the compressor stored in the storage means, and the discharge temperature of the compressor A third temperature detecting means for detecting, and the first temperature detecting means. Of the discharge temperature of the compressor based on the evaporation temperature detected by the temperature detecting means and the saturation temperature of the discharge pressure estimated by the first estimating means; Expansion valve control means is provided for changing the discharge temperature detected by the third temperature detection means by aiming at the target discharge temperature by controlling the opening degree.

As described above, the average pressure loss-equivalent temperature is highly accurately estimated based on the average pipe length per room and the average number of revolutions of the compressor, and the average pressure-loss-equivalent temperature is added to the average condensation temperature. Even in this air conditioner, the saturation temperature of the discharge pressure of the compressor can always be estimated with high accuracy under various operating conditions, and the compression based on the saturation temperature of the discharge pressure of the compressor estimated with high accuracy can be used for compression. By calculating the target discharge temperature of the machine and controlling the discharge temperature, it is possible to always control the actual intake refrigerant superheat degree to an appropriate superheat degree under various operating conditions.

Further, according to the present invention as set forth in claim 3, fourth temperature detecting means for detecting the suction temperature of the compressor, evaporation temperature detected by the first temperature detecting means and the fourth temperature detecting means. Second estimating means for estimating the degree of superheat of the refrigerant sucked in the compressor on the basis of the intake temperature detected by the temperature detecting means, and the discharge temperature detected by the third temperature detecting means is calculated by the target discharge temperature calculating means. If the suction refrigerant superheat degree estimated by the second estimating means is out of the predetermined range with respect to the set target discharge temperature, the pipe length stored in the storage means in advance. Is provided with a pipe length correcting means.

In this way, the pipe length stored in advance is automatically corrected by using the suction refrigerant superheat during the discharge temperature control. Therefore, even if the actually installed pipe length changes variously, The length can be estimated.

As a result, it is possible to always control the actual intake refrigerant superheat degree near the appropriate superheat degree even under various operating conditions and construction conditions. As a result, it is possible to perform energy saving operation, and it is possible to avoid problems of compressor reliability deterioration such as insufficient capacity and liquid back.

Further, by automatically estimating the pipe length, it is not necessary for the builder to manually set the pipe length by a switch or the like provided on the electric circuit, and the switch or the like becomes unnecessary, thereby reducing the cost of the product. Can be lowered. Furthermore, a low-cost temperature sensor can be used instead of the pressure sensor that directly detects the discharge refrigerant pressure, so that the cost of the product can be reduced.

Further, according to the present invention described in claim 4, when the pipe length corrected by the pipe length correcting means deviates from the predetermined pipe length, the user is informed that the installed pipe length is not appropriate. It is provided with an abnormality detecting means.

As a result, it is possible to avoid serious damage to the system due to inadequate piping work, and the installed pipe length is within the proper pipe length, but the pipe is deformed during installation and the refrigerant flow resistance increases. Even if it does, it is possible to detect the abnormality and prompt the correction of the piping construction.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an air conditioner according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of an air conditioner according to another embodiment of the present invention.

FIG. 3 is a flowchart showing control of the air conditioner.

FIG. 4 is a graph showing a pressure loss relationship between the refrigerant circulation amount and the pipe length.

FIG. 5 is a Mollier diagram showing the refrigeration cycle behavior of the air conditioner.

[Explanation of symbols]

1 outdoor unit 2 Indoor unit 3 compressor 5 outdoor heat exchanger 6 Electric expansion valve 7 Indoor heat exchanger 8 connection piping 9 Discharge temperature sensor 10 Outdoor heat exchanger temperature sensor 11 Indoor heat exchanger temperature sensor 12 Intake temperature sensor 13 Indoor liquid temperature sensor Ha, Hb piping length Tca, Tcb Condensation temperature

Claims (4)

[Claims] 1. An outdoor unit having a variable capacity compressor, an outdoor heat exchanger, a first temperature detecting means for detecting a temperature of the outdoor heat exchanger, and an electric expansion valve having a controllable valve opening. An air conditioner having an indoor unit having an indoor heat exchanger and a second temperature detecting means for detecting a temperature of the indoor heat exchanger, and a connection pipe connecting the outdoor unit and the indoor unit, Based on the condensing temperature detected by the second temperature detecting means during the heating operation, the pipe length stored in the storing means, and the rotation speed of the compressor. First estimating means for estimating the saturation temperature of the discharge pressure of the compressor, third temperature detecting means for detecting the discharge temperature of the compressor, evaporation temperature detected by the first temperature detecting means, and Discharge pressure estimated by the first estimating means Target discharge temperature calculation means for calculating the target discharge temperature of the compressor based on the saturation temperature of the force, and the third temperature aiming at the target discharge temperature by controlling the opening degree of the electric expansion valve An air conditioner comprising: an expansion valve control means for changing the discharge temperature detected by the detection means. 2. An outdoor unit having a variable capacity compressor, an outdoor heat exchanger, a first temperature detecting means for detecting the temperature of the outdoor heat exchanger, and a plurality of electric expansion valves capable of controlling valve opening. And a plurality of indoor units each having an indoor heat exchanger and a second temperature detecting means for detecting the temperature of the indoor heat exchanger, the multi-type air conditioner being connected in parallel by connecting pipes. Storage means for storing in advance the pipe length of each connection pipe to the unit, and the second unit of each indoor unit during heating operation.
Estimating the saturation temperature of the discharge pressure of the compressor based on each condensation temperature detected by the temperature detecting means, the pipe length of each connecting pipe stored in the storage means, and the rotation speed of the compressor. No. 1 estimation means, third temperature detection means for detecting the discharge temperature of the compressor, evaporation temperature detected by the first temperature detection means, and discharge pressure estimated by the first estimation means. Target discharge temperature calculating means for calculating the target discharge temperature of the compressor based on the saturation temperature, and the third temperature detecting means aiming at the target discharge temperature by controlling the opening degree of the electric expansion valve. And an expansion valve control means for changing the discharge temperature detected by the air conditioner. 3. A fourth temperature detecting means for detecting a suction temperature of a compressor, an evaporation temperature detected by the first temperature detecting means and a suction temperature detected by the fourth temperature detecting means. A second estimating means for estimating the superheat degree of the refrigerant sucked into the compressor based on the above, and a discharge temperature detected by the third temperature detecting means are within a predetermined range with respect to the target discharge temperature calculated by the target discharge temperature calculating means. And the second
3. The air according to claim 1 or 2, further comprising: a pipe length correction unit that corrects a pipe length stored in advance in the storage unit when the intake refrigerant superheat degree estimated by the estimation unit deviates from a predetermined range. Harmony machine. 4. When the pipe length corrected by the pipe length correcting means deviates from a predetermined pipe length, an abnormality detecting means is provided to inform the user that the installed pipe length is not appropriate. Item 3. The air conditioner according to Item 3.