JPH02213639A - Air conditioner for multi rooms - Google Patents

Abstract

PURPOSE:To improve a distributing performance of refrigerant, eliminate a refrigerant recovering circuit, enable a pair of pipes to be worked from an outdoor unit and further reduce a cost of piping work by a method wherein a heat exchanger for use in heat exchanging between a gas pipe and a liquid distributing pipe is provided, a liquid branch pipe is provided with an expansion valve driven with an electrical signal and the refrigerant is properly distributed while a sub-cooling operation is kept constant during cooling operation. CONSTITUTION:During cooling operation, a high pressure gas refrigerant from a compressor 1 is liquified by an outdoor heat exchanger 3, heat exchanged with a gas pipe side refrigerant through a heat exchanger 6, pressure of the refrigerant is reduced by expansion valves 11a to 11c, the refrigerant is evaporated by indoor heat exchangers 15a to 15c so as to cool an interior of the room. The evaporated refrigerant is heat exchanged with another refrigerant in a liquid side pipe 8 with a heat exchanger 6, the refrigerant returns to an outdoor unit 5, passes through an accumulator 4 and then it returns to the compressor 1. At this time, a sub-cool at an outlet of the indoor heat exchanger 3 is kept constant by a pressure sensor 21 and a thermistor 22 at the outlet of the outdoor heat exchanger 3 and at the same time, a degree of opening of all the expansion valves is restricted in response to a size of each of the indoor units 16a to 16c through capability setting switches 24a to 24c and then the expansion valves 11a to 11c are controlled by a controlling means 25 in such a way as the refrigerant flow is properly distributed.

Description

[Detailed description of the invention]

[Industrial Application Wl] This invention relates to a multi-room air conditioner in which a plurality of indoor units are connected to one outdoor unit. [Prior Art] Conventionally, as this type of multi-room air conditioner, for example,
The multi-room air conditioner described in Japanese Patent No. 5-28993 can be mentioned. FIG. 11 is an overall configuration diagram of a conventional multi-room air conditioner known from the above-mentioned publication. In the figure, 1 is a compressor, 2 is a four-way switching valve that is connected to the compressor 1 and switches between cooling and air conditioning cycles, and 3 is one side connected to the four-way switching valve 2. On the other hand, there is an outdoor heat exchanger in which an expansion valve 31 and a receiver 33 are connected in series; 4 is an accumulator connected between the compressor 1 and the four-way switching valve 2; 32 is an accumulator connected in parallel with the expansion valve 31; These check valves constitute the main circuit section of the air conditioner. Further, 15a and 15b are branched in parallel from the main circuit, and between the four-way switching valve 2 and the receiver 33, gas side solenoid valves 34a and 34b and wave adjustment solenoid valve 35a,
35b, each of these heat exchangers @15a, 15b has an expansion valve 37a, between each wave harmonic solenoid valve 35g, 35b.
37b and the parallel circuits of the check valves 36a and 36b are connected in series. In addition, 5 is an outdoor unit, 16a, 1
6b indicates an indoor unit. In this conventional multi-room air conditioner, by switching the four-way switching valve 2, the cooling operation is performed as shown by the solid line arrow, and the heating operation is performed as shown by the dotted line arrow. , 15b, that is, a plurality of indoor units 16a,
16b is provided with expansion valves 37a and 37b for cooling.
Load imbalance in b or each room Ia16 a,
The main purpose of this is to supply an appropriate amount of refrigerant even if the installed positions of the refrigerant 16b are not relatively uniform. However, [l! During air conditioner operation, there is no means to distribute an appropriate amount of refrigerant to the plurality of indoor units 16a, 16b, and the circuit configuration is not necessarily sufficient for a multi-room air conditioner. Furthermore, during cooling operation, the amount of refrigerant is distributed to each indoor unit 16a, f6b by the expansion valves 37a, 37b.
Since there is no means to correct the influence of other indoor units, each indoor unit is influenced by other indoor units, which tends to cause a hunting phenomenon in the distribution of refrigerant. The degree of superheating (hereinafter referred to as superheat) at the outlet of 15b is controlled to a constant value, and when the superheat is too high, indoor heat exchangers 15a and 1
5b's efficiency decreases, and the cooling capacity tends to decrease. In other words, this is because, as can be seen from the characteristic diagram in Figure 12, which shows the relationship between the refrigerant state at the heat exchanger outlet and the average heat transfer coefficient, when the heat exchange distillate outlet enters the superheat region, the performance decreases rapidly. For example, in the case of an indoor heat exchanger 15a having multiple paths as shown in the block diagram of the heat exchanger 15a of a general indoor unit 16a in FIGS. 13(1) and 13(b), the overall Even if the superheat is appropriate, if the superheat for each pass varies, the performance of the path with a large superheat will deteriorate, which will further contribute to the decline in cooling capacity. In addition, in FIGS. 13(a) and 13(b), 45 is a snow distribution, 46a to 46c are distribution pipes, 47a to 47c are evaporator paths, and 48 is a ladder. In addition, the conventional multi-room air conditioner has a receiver 33 that stores surplus refrigerant due to changes in operating conditions because of the super-seven control by the expansion valves 37a and 37b during cooling operation.
An accumulator 4 and two refrigerant absorption containers are required to prevent liquid from returning to the compressor 1 in a transient state. Furthermore, in conventional multi-room air conditioners, the confluence point P of the wave harmonic branch circuit during heating operation is a high-pressure liquid refrigerant, and if even one of the indoor units is stopped, this stop circuit In order to recover the refrigerant inside, a refrigerant recovery circuit that is connected to the low pressure circuit of the compressor via a check valve and a capillary tube is required, which makes the refrigerant circuit complicated. Note that the refrigerant recovery circuit is omitted in FIG. 11. In addition, in a general air conditioner with so-called one-to-one correspondence, in which one indoor unit corresponds to one outdoor unit, the first
As shown using the same reference numerals in Figure 4, the indoor unit 16 is not provided with an expansion valve for controlling the refrigerant, and the outdoor unit 5 has an emergency system in which both cooling and heating are controlled by a capillary tube 40. Usually, the circuit configuration is simple and inexpensive. However, conventional multi-room air conditioners require a large number of units to be produced.
One-to-one compatible indoor units that can be obtained at a relatively low cost cannot be used as is (<, the cost of the indoor unit becomes relatively high as it becomes a dedicated unit. On the other hand, in the field of building air conditioning, the cost of the indoor unit is relatively high. Multi-room air conditioners are becoming popular due to constraints on installation space, but the conventional multi-room air conditioner shown in Figure 11 generally extends from the rooftop where the outdoor unit is installed to the floor where the indoor unit is installed. It is necessary to construct refrigerant piping for the number of indoor units, which increases the construction cost and increases the exclusive area of the building's pipe shaft.As shown in the diagram, there is a floor where the indoor units are installed from the outdoor units. An air conditioner that can be constructed with a single pair of piping was published in Japanese Patent Application Publication No. 1983-
This is proposed in Japanese Patent No. 102046. Note that in FIG. 15, the same reference numerals and symbols as in FIG. 11 indicate the same or corresponding components as those of the first conventional multi-room air conditioner, and the explanation thereof will be omitted. In FIG. 15, 38a and 38b are electric expansion valves that perform the functions of the wave-adjusted solenoid valves 35a and 36b and expansion valves 37a and 37b in FIG. 11, and 14 is an electric expansion valve 38a and 38b and a gas side solenoid valve 34a. , 34b, a branching unit containing
39a and 39b are capillary tubes provided between each of the indoor heat exchangers 15a and 15b of the indoor units 16a and 16b and the harmonic electric expansion valves 38a and 38b of the branch unit 14. Moreover, 19 and 20 are piping paths that connect the indoor units 16a and 16b and the outdoor unit 5. In this conventional multi-room air conditioner, the refrigerant is circulated as indicated by the solid line arrow during cooling operation and as indicated by the dotted line arrow during heating operation by switching the four-way switching valve 2. Here, during cooling operation, the electric expansion valves 38a and 38b distribute cooling to the indoor units 16a and 16b, and during heating operation, the electric expansion valve is fully opened, and the capillary tubes 39m and 3
9b, the indoor unit 16a. The distribution of the refrigerant to the refrigerant 16b is corrected, and the pressure reduction is performed by the expansion valve 31.

[Problems to be Solved by the Invention] However, in the case of this type of multi-room air conditioner, the means for distributing refrigerant to the indoor units during heating operation is improved compared to the conventional example shown in Fig. 13. But super tl knee 1-
For control purposes, the distribution performance during cooling operation is similar to that of the conventional example shown in FIG. 11, and a receiver 33 and a refrigerant recovery circuit are also required. In addition, in both the former conventional example and the latter conventional example, when the indoor unit is stopped, the refrigerant is shut off by the gas-side solenoid valves 34a and 34b during yJ room operation, so when additional operation is performed, the high-pressure gas refrigerant is used to heat the room. Exchanger 15a. 15b and may generate refrigerant noise on the indoor unit side. Therefore, although this invention is a simple refrigerant circuit, it
It can be directly connected to standard indoor units used in air conditioners, and at the same time allows for proper refrigerant distribution during cooling/heating operations to multiple indoor units, and no refrigerant recovery circuit is required, making it possible to adjust the amount of refrigerant using just the accumulator. This makes it possible to prevent the generation of refrigerant noise even during additional operation of the indoor unit.Furthermore, it is a multi-room air conditioner with a high degree of freedom in installation. The challenge is to provide this information. [Means for Solving the Problems] A multi-room air conditioner according to the present invention includes a branch 2-two unit 14
Gas side branch pipes 9a to 9c and liquid branch pipes 10a to 10.
c and a heat exchanger 6 for mutually exchanging heat between the gas pipe 7 and the liquid pipe 8, and the Wl side branch pipes 10a to 10.
Expansion valves 11a to 11c driven by electric signals are arranged in c to form a refrigerant circuit, and a temperature detector 23a is arranged in the liquid branch pipes 10a to 10c and the cooling outlet pipe of the outdoor heat exchanger 3. ~23c, 22, a detection means 21 for detecting the high pressure or saturation temperature on the output side of the compressor, a capacity setting switch for setting the capacity of the indoor unit, and temperature and pressure or saturation temperature detection obtained by the temperature detectors. and control means for controlling the expansion valves 11a to llc based on the pressure or saturation temperature obtained by the means and the signal from the capacity setting switch. Further, in the multi-room air JiC conditioner according to another invention of the present invention, in the refrigerant circuit of the above-mentioned invention, temperature is detected in each of the gas side branch pipe, the liquid branch pipe, and the cooling outlet pipe of the outdoor heat exchanger. and a detection means for detecting the high pressure or saturation temperature on the output side of the compressor, and the temperature obtained by each of the temperature detectors and the pressure obtained by the pressure or saturation temperature detection means. Alternatively, a control means for controlling the expansion valve based on the saturation temperature is provided.

[Effect]

In the multi-room air conditioner of the present invention, during heating operation, the high pressure or saturation temperature on the outlet side of the compressor detected by the detection means and the temperature of each liquid branch pipe detected by the temperature sensor are detected. Based on the detected temperature, the expansion valve is controlled by the control means so as to keep the outlet subcool of the indoor heat exchanger constant, and during cooling operation, the temperature is The outlet subcooling of the outdoor heat exchanger is kept constant based on the pressure or saturation temperature detected by the detector and the detected temperature, and at the same time, the overall expansion valve opening is adjusted based on the size of each indoor unit registered by the capacity setting switch. The expansion valve is controlled by a control means to dispense. According to another aspect of the present invention, the expansion valve is controlled by the control means ζ in the same manner as described above during the heating operation, and the expansion valve is connected to the detection means and the outdoor heat exchanger during the cooling operation. At the same time, the subcooling at the outlet of the outdoor heat exchanger is made constant by a temperature sensor installed on the outlet side piping, and at the same time, the gas side branch It is controlled by control means to equalize the temperature of the tube. Therefore, during cooling and heating operations, the degree of subcooling can be controlled while balancing the supply of refrigerant to a plurality of indoor units.

【Example】

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a refrigerant circuit diagram of a multi-room air conditioner according to a first embodiment of the present invention, and FIG. 2 is a block diagram of a control means for a multi-room air conditioner according to an embodiment of the present invention. In FIG. 1, 1 is a compressor, 2 is a four-way switching valve, 3 is an outdoor heat exchanger, and 4 is an accumulator, and the refrigerant circuit of the outdoor unit 5 is constructed by sequentially connecting the above components. Reference numeral 6 denotes a heat exchanger configured by, for example, closely welding the gas piping 7 and the liquid piping 8 to each other so that the gas piping 7 and the liquid piping 8 exchange heat with each other. 9c, and the liquid pipe 8 is connected to the liquid branch pipes 10a to 10c via a check valve 13 connected in parallel with the series circuit of the heat exchanger 6 and the check valve 12, and The branch pipes 10a to 10c are provided with expansion valves 11 that are driven by electric signals.
a~11. c is arranged to constitute a refrigerant circuit of the branch unit 14. In addition, 15a to 15c are indoor units 16a
It is an indoor heat exchanger built in ~16c, and the indoor unit 16
a to 16c and the branch unit 14 are connected by multiple pairs of branch communication pipes (gas side branch communication pipes 17a to 17c and liquid return branch communication pipes 18a to 18c), and the branch unit 14 and the outdoor unit 5 are connected to one pair of main communication pipes. They are connected by pipes (gas side main communication pipe 19 and harmonic main communication pipe 20) to form a refrigeration cycle. 2 is a pressure sensor which is a pressure detection means for detecting the discharge pressure of the compressor; 22 is a thermistor which is a temperature detector which detects the outlet temperature of the outdoor heat exchanger 3 during cooling operation; and 23a to 23c are sensors during heating operation. Thermistors 24a to 24c are temperature detectors that detect the temperature of the liquid side branch pipes 10a to 10c.
A capacity setting switch for setting the capacity of the controller 16c is connected to an input circuit 52 of the control means 25, which will be described later. 25 takes in the temperature and pressure signals and supplies the expansion valves 11a to 11.
It is a control means for controlling the FIG. 2 is a block diagram of the control means 25, which basically consists of an analog/digital (A/D) conversion word 51, an input circuit 5
2. Central processing unit (CPU) 53, memory 54. Output circuit 55. It is composed of an output buffer 56. The capacity setting switches 24a to 24c are composed of, for example, 3-bit switches, and each can be set in eight ways depending on the capacity of the indoor units 16a to 16c. Note that the input/output section shows only an example of the thermistor 22, which is a temperature detector that detects the outlet temperature of the outdoor heat exchanger 3 during cooling operation, and the expansion valve 11a. Next, the operation of the multi-room air conditioner of this embodiment having the above configuration will be explained. The high-pressure gas refrigerant discharged from the compressor 1 during cooling operation is
It passes through the four-way switching valve 2 and is liquefied by the outdoor heat exchanger, passes through the harmonic main connecting pipe 20, is guided to the branch unit 14, and is exchanged with the gas pipe side refrigerant by the heat exchanger 6 to obtain a large subcooling, and is then liquefied. Liquid side branch pipes 10a to 10c pass through the upper valve 12
guided by. Here, the pressure is reduced by the expansion valves 11a to 11c, and it passes through the harmonic branch connection pipes 18a to 18c to the indoor heat exchangers 15a to 15c.
15c, where it evaporates and cools the room. The evaporated refrigerant passes through the gas side branch communication pipes 17a to 17c,
The refrigerant is guided to the branch unit 14, collected here, and exchanges heat with the refrigerant in the wave modulation pipe 8 in the heat exchanger 6, then returns to the outdoor unit 5 through the gas side main communication pipe 19, and is connected to the four-way switching valve 2. A cycle is formed in which the air returns to the compressor 1 via the accumulator 4, thereby performing cooling operation. At this time, the pressure sensor 21 and the thermistor 22 at the outlet of the outdoor heat exchanger 3 keep the subcool at the outlet of the outdoor heat exchanger 3 constant, and at the same time, the capacity setting switch: P24a ~
Depending on the size of each indoor unit 16a to 16c registered by 24c, the total! The expansion valves 11a-
llc. FIG. 3 is a flowchart 1 for explaining an example of control of the expansion valves 11a to 11C during cooling operation by the control means 25 of this embodiment. First, when the control is started, in step S1, the high pressure of the high pressure refrigerant gas discharged from the compression PA1 is detected by the pressure sensor 21.
The saturation temperature t2 detected by and converted from the pressure is input, and in step S2, the thermistor 22 provided on the output side of the outdoor heat exchanger 3 detects the outlet temperature t2 of the outdoor heat exchanger 3. Temperature t2 is input. In step S3, the subcool SC as a difference between these temperatures is calculated as 5C=t, -t2. In step S4, subcool target value SC
It is determined whether the absolute value of the difference from 0 is 13cm5C01 is 3℃ or less, and if it is 3℃ or less, the total opening degree NJ
is not changed and the process moves to step S6. In addition, when it is determined that the deviation l5C-3Col from the input subcool target value SCo as the subcool setting value exceeds 3°C, the total value N of each expansion valve opening is calculated using the formula % in step S5. %). Here, NJ: Opening degree of each expansion valve NJ: Opening degree of each expansion valve before change A: Positive constant determined by experiment If the opening degree of the expansion valves 11a to 11C is small, adjust the overall opening degree of the expansion valves 11a to 11C to the open direction, and if the opening degree is small, adjust the opening degree to the closed direction.
Move on to 6. In step S6, the capacity codes QJ (=Q, -Q,) of each of the indoor units 16a to 16C in operation are read from the capacity setting switches 24a to 24c. Then, in step S7, the total opening xsB N J is distributed according to the size of QJ,
In step S8, the new opening degree N of each expansion valve 11a-lie is output, and this blowing is completed by I%. According to this flowchart, the subcooling adjustment and each indoor unit 16a to 1
It is controlled to appropriately distribute the refrigerant to 6c. That is, as can be seen from the characteristic diagram shown in FIG. 12, which shows the relationship between the refrigerant state at the outlet of the heat exchanger and the average heat transfer coefficient,
When the outlet enters the superheat region, the performance deteriorates rapidly, so it can be seen that using the outlet in a wet state (dryness x 0.9 or so) is important for improving performance. The above control utilizes this, and the subcool is actively increased (taken) by the heat exchanger 6 of the branch unit 14.
The outlet of the indoor heat exchangers 15a to 15c is kept in a humidity state of 9, and at the same time, even if the dryness of the outlet varies slightly in each circuit, stable performance is obtained. In distributing the refrigerant to the indoor units 16a to 16c, the distribution to each indoor unit 16a to 16C is adjusted according to the refrigerant condition at the outlet of the indoor heat exchangers 15a to 15c without applying feedback. Indoor units 16a-1
Even by distributing the total opening according to the capacity ratio of 6C, sufficient distribution performance can be ensured and controllability can be improved. At the same time, outdoor heat exchange N3 can also be used effectively since appropriate subcooling is achieved with outdoor heat exchange N3. As a matter of course,
The amount of refrigerant is charged so that the outlets of the indoor heat exchangers 1i 15 a to 15C are kept moist even when all the indoor units 16a to 16c are operated. In addition, the heat exchanger 6 of the branch unit 14 suffers pressure loss in the extension piping due to the height difference between the outdoor unit 5 and the indoor units 16a to 16c, and the expansion valve 11a
The refrigerant in front of ~11C flashes and the expansion valves 11a~l
It can also serve to prevent the flow characteristics of the lc from changing. Furthermore, when the number of operating indoor units 16a to 16e decreases, the number of indoor units 16a to 16 that have stopped is
It also has the function of stopping the refrigerant supply by fully closing the expansion valves 11a to 11c of c, and at the same time, allowing excess refrigerant to be stored in the accumulator 4. In addition, during heating operation, the high-temperature, high-pressure gas refrigerant discharged from the compressor 1 is transferred to the four-way switching valve 2, which switches the flow path as shown by the dotted line.
The branch unit 1 is connected via the gas side main connection pipe 19.
4, the refrigerant is divided into gas side branch pipes 9a to 9C,
It is led to indoor heat exchange @ 15a to 15C via gas side branch communication pipes 17a to 17c. Indoor heat exchanger 15a
The refrigerant liquefied in ~15c is transferred to the harmonic branch connection pipes 18a~1
8c to the branch unit 14, and the liquid side branch pipe 10
The pressure is reduced by the expansion valves 11a to 11c provided at a to 10c, and the refrigerant becomes a two-phase refrigerant with a check valve 13 and a harmonic main communication pipe 20.
It returns to the outdoor unit 5 through the outdoor heat exchanger 3, evaporates in the outdoor heat exchanger 3, and then passes through the four-way switching valve 2. A heating operation is performed by configuring a cycle that returns to the compressor 1 via the accumulator 4. During heating operation, when the heat exchanger 6 is activated, its capacity is reduced, so the check valve 12 prevents low-pressure refrigerant from flowing into the heat exchanger 6, thereby preventing heat exchange. At this time, pressure sensor 2
1 and the thermistor 23 provided in the liquid side branch pipes 10a to 10c.
The control means 25 controls the expansion valves 118 to 11c so as to keep the outlet subcools of the indoor heat exchangers 15a to 15c constant by a to 23c. FIG. 4 is a flowchart illustrating an example of control of the expansion valves 11a to 11ie during heating operation by the control means 25 of this embodiment. First, when the control is started, high pressure is detected by the pressure sensor 21 in step 321, and the saturation temperature T, which is converted from the pressure, is input, and in step 822, the temperatures T, . T3 is detected, the temperatures T and .about.T3 are input, and in step 323, subcools SC and .about.SC3 as these temperature differences are calculated using formula 3. At step 824, the average value 5CAV of each subflule is calculated using the formula %. In step 325, the average value of subcool is 5
Absolute value of the difference between CAV and subcool target value S00 13
It is determined whether the cA V SCol is 3°C or less,
If the temperature is 3° C. or lower, the process moves to step S27. Difference l from the target subcool S00 input as the subcool setting value
When it is determined that 5CAV 5Col exceeds 3° C., in step 326, the total opening degree of each expansion valve 11a to 11C is calculated using the formula %. Here, NJ: Opening degree of each expansion valve NJ: Opening degree of each expansion valve before change C: Positive constant determined by experiment The sum of the opening degrees of each expansion valve 11a to llc is calculated, and the average subcool If it is thick, use the expansion valve fla
The opening degree of the entire ~liC is adjusted in the opening direction, or if it is small, in the closing direction, and the process moves to step 327. In step S27, it is determined whether the deviation Is CJ S CA vi of each subcool is 2° C. or less. If the deviation is 2° C. or less, the variable is set to zero in step 32B and the process moves to step 330. If the deviation exceeds 2°C, step 32
At step 9, a predetermined constant D0 is set as the variable, and the process moves to step 830. Then, in step 330, each expansion valve opening degree NJ is calculated using the calculation formula % formula %, and in step 331, each expansion valve 118 to
The new opening degree Nu of lie is output and this routine ends. Note that each I! in step 330 ! ! Zhang valve 11a-l
D in the calculation of the new opening of ie is a positive constant determined by experiment, and according to this calculation formula, the subcools of the liquid branch pipes 10a to 10c are the indoor units 16a to 16 with higher subcools.
c is adjusted to a constant target value by increasing the valve opening degree, and by decreasing the valve opening degrees for the indoor units 16a to 16c with lower subcooling. According to this flowchart 1-, the refrigerant is corrected by the overall movement of the average subcool and by the deviation of each individual subcool, taking into account the influence of the operating status of other indoor units lea to 16c. The amount is distributed,
＃He has a very good personality. When the number of operating indoor units 16a to 16c decreases,
Expansion valve 11a corresponding to stopped indoor units 16a to 16c
~lie is completely closed to stop the flow of refrigerant. Excess refrigerant is stored in accumulator 4 in the same way as during cooling operation.
It can be stored inside. Indoor heat exchangers 15a to 16c of stopped indoor units 16a to 16c
15c, the refrigerant gradually condenses, but since the liquid pipe 8 side is the low pressure side, the expansion valves 11a to 11 are installed as necessary.
If c is opened for a certain period of time, the refrigerant can be recovered. Furthermore,
Since the indoor heat exchangers N15a to 15c are always connected to the high pressure circuit, no refrigerant noise is generated even if the indoor units 16a to 16c are additionally operated. In addition, the expansion valves 11a to 11c, which are compatible with the indoor units 16a to 16c for both cooling and heating, provide a throttling function and each indoor unit 16.
Since it has the function of distributing the amount of refrigerant to a to 16c,
Differences in length of gas side branch connecting pipes 17a to 17c and harmonic branch connecting pipes 18a to 18c and indoor units 16a to 16c
Differences in flow rate due to differences in height are automatically corrected by the control means 25, and a proper flow rate can be ensured in any situation.Furthermore, piping construction can be carried out using a pair of piping from the outdoor fi 5 and branching from the middle. It becomes possible. Furthermore, since it is not necessary to provide the indoor units 16a to 16c with a throttle mechanism, they can easily be combined with standard indoor units that do not have the throttle mechanism. FIG. 5 is a refrigerant circuit diagram of a multi-room air conditioner according to a second embodiment of the present invention. In the drawings, the same reference numerals and symbols as in the first embodiment indicate constituent parts that are the same as or correspond to those in the first embodiment, and redundant explanation will be omitted here, and only the differences will be explained. In this embodiment, instead of the pressure sensor 21 of the first embodiment,
A saturation temperature detection circuit 26 is used, and the temperature is detected by a temperature sensor 27 which is a saturation temperature detection means that directly detects the saturation temperature instead of pressure. This detection circuit 2
6 is composed of a heat exchanger 29, a capillary tube 28, and a temperature sensor 27, and the refrigerant at the outlet of the compressor 1 is cooled by the heat exchanger 29, becomes a two-phase medium, and is reduced in pressure by the capillary tube 28 to the suction pressure of the compressor 1. It becomes a low-temperature two-phase refrigerant and is used in heat exchanger 2.
By exchanging heat at step 9, the refrigerant becomes a low-pressure refrigerant with the enthalpy of the refrigerant at the compressor outlet, completing the cycle. FIG. 6 is a Mollier diagram showing the state of the refrigerant in the saturation temperature detection circuit of the multi-room air conditioner according to the embodiment of FIG. B
, C, and D represent the states of the refrigerant in a normal refrigeration cycle. Further, E indicates the inlet state of the capillary tube 28, and by attaching the temperature sensor 27 at this location, it becomes possible to detect the high pressure saturation temperature without using a pressure sensor. In addition, in this example, the flowchart of the first example 1-
In step S1 and step S21, the saturation temperature t is directly detected. FIG. 7 is a refrigerant circuit diagram of a multi-room air conditioner according to a third embodiment of the present invention. In the drawings, the same reference numerals and symbols as in the first embodiment indicate constituent parts that are the same as or correspond to those in the first embodiment, and redundant explanation will be omitted here.
Only the differences will be explained. In the third embodiment of the present invention, a capacity setting switch 24 that can set the capacity of a plurality of indoor units in the first embodiment is used.
Thermistors 24d to 24f, which are temperature detectors for detecting the temperature of the gas side branch pipes 9a to 9c during cooling operation, are arranged in the gas side branch pipes 9a to 9c, respectively, in place of the a to 24c,
The detected temperature detected by the thermistors 24d to 24f, the detected temperature detected by the thermistor 22 that detects the outlet temperature during cooling operation, and the pressure signal from the pressure sensor 21 are taken into the control means 25 to control the expansion valves 11a to llc. The opening degree is controlled. FIG. 8 is a block diagram of the control means in the third embodiment, which basically includes the AID converter 51 as in the first embodiment.
．． It is composed of an input circuit 52, a central processing unit CPU53, a memory 54, an output circuit 55, and an output buffer 56. Note that, as in the first embodiment, only an example of the thermistor 22 and the expansion valve 11a are shown as the input/output section. Even with the above configuration, the pressure sensor 21 is
The thermistor 22 at the outlet of the outdoor heat exchanger 3 makes the subcooling at the outlet of the outdoor heat exchanger 3 constant, and at the same time, the thermistors 24d to 2 disposed in the gas side branch pipes 9a to 9C
4f, the control means 25 can control the opening degrees of the expansion valves 11a to 11c so as to equalize the temperature of the gas side branch pipes 98 to 9C. FIG. 9 is a flowchart for explaining the control of the expansion valves 11a to llc during cooling operation by the control means 25 of the third embodiment. First, when the control is started, the high pressure of the high pressure refrigerant gas completely discharged from the compressor 1 is detected by the pressure sensor 21 in step 341 as in the first embodiment, and the saturation temperature t, which is converted from the pressure, is detected. input, and by the thermistor 22 provided on the output side of the outdoor heat exchanger 3 in step 342,
The outlet temperature t2 of the outdoor heat exchanger 3 is detected, and this outlet temperature t2 is input. In step 843, the subcool SC as the difference between these temperatures is calculated as 5C=t, -t2. In step 344, the subcool target value S
It is determined whether the absolute value l5c-3C01 of the difference with Co is less than 3°C, and if it is less than 3°C, the total opening degree is
The process moves to step 846 without changing J. In addition, the input subcool target value SC as the subcool setting value
When it is determined that the deviation l5c-scol from
is calculated using the formula % formula %). Here, NJ: Opening degree of each expansion valve NJ: Opening degree of each expansion valve before change A: A positive constant determined by experiment The sum of the opening degrees of each expansion valve NJ is calculated, and the subcool is thick. If the opening is small, adjust the overall opening of the expansion valves 11a to 11C to open, and if the opening is small, adjust the opening to close.Step 3
Moving on to 46. In step 846, the temperature detection @T, -T3 of the gas side branch pipes 93-9C is inputted by the thermistors 24d-24f, and in step 347, the average (II
! T A V is calculated, and in step S48 the deviation IT
It is determined whether J TAVI is below 2°C. If the deviation is 2 degrees Celsius, the variable B is set to zero in step/349 and the process moves to step 351. If the deviation exceeds 2° C., a predetermined constant 80 is set to variable B in step S50, and the process moves to step 851. Then, in step 351, the opening degree NJ of each expansion valve 11a to 11b is calculated using the calculation formula % formula %, and in step 352, each 11t! Zhang Ben 1
The new opening degrees N of 1a to 11C are output and this routine ends. That is, each expansion valve 11a in step 352
B in the formula for calculating the new opening degree of ~11C is a positive constant determined by experiment, and according to this formula, the gas side branch pipe 9a~
The temperature of 9C is determined by increasing the opening degree of each expansion valve 11a-lie for indoor units 16a-16c with a higher temperature, and by increasing the opening degree of each expansion valve 11a-lie for indoor units 16a-16c with a lower temperature.
1a-11Cf) Adjust temperature by reducing rM degrees. In this way, according to the flowchart of the third embodiment, control is performed so that the subcool adjustment and the temperature of the gas side branch pipe match. That is, as can be seen from the characteristic diagram shown in FIG. 12, which shows the relationship between the refrigerant state at the outlet of the heat exchanger and the average heat transfer coefficient,
When the outlet enters the super beat region, the performance deteriorates rapidly, so it can be seen that using the outlet in a wet state (dryness x 0.9 or so) is important for improving performance. The above-mentioned control utilizes this, and actively increases the subcooling level by the heat exchanger 6 of the branch unit 14, keeping the outlets of the indoor heat exchangers 15a to 15c in a moist state, and at the same time, dampens the dryness of the outlet. Even if there are slight changes in each circuit, stable performance is obtained, and controllability is very good when distributing refrigerant to multiple indoor units 18a to 16c. At the same time, the outdoor heat exchanger 3 can also be used effectively since the outdoor heat exchanger 3 provides appropriate subcooling. Naturally, indoor unit 16
Indoor heat exchanger 153 even when all a to 16c are not operated.
The amount of refrigerant is charged so that the outlet of ~15c becomes wet. Furthermore, the heat exchanger 6 of the branch unit 14 is connected to the outdoor unit 5.
Pressure loss occurs in the extension piping due to height differences between the indoor units 16a to 16c, and the refrigerant before and after the expansion valves 11a to 11C flashes, changing the flow characteristics of the HH expansion valves 11a to llc. It can also play a role in preventing this. Furthermore, when the number of operating indoor units 16a to 16c decreases, the refrigerant supply is stopped by fully closing the expansion valves 11a to llc of the stopped indoor units 16a to 16c, and at the same time, excess refrigerant is drained into the accumulator 4. It is also the same as the first embodiment in that it has the function of being able to store the water in the water. Also, during the heating operation in this third* embodiment, the expansion valve is controlled by the control means 25, as in the heating operation in the first embodiment described above, and the control flow is as follows: Since it is similar, it will be omitted. In the multi-room air conditioner according to the third embodiment of the present invention, the expansion valve is controlled by a microcomputer as in the first embodiment, which is convenient even when the compressor is frequency controlled by an inverter. good. FIG. 10 is a refrigerant circuit diagram of a multi-room air conditioner according to a fourth embodiment of the present invention. In the drawings, the same reference numerals and symbols as in the third embodiment indicate constituent parts that are the same as or correspond to those in the third embodiment, and redundant explanation will be omitted here, and only the differences will be explained. Similar to the second embodiment, this embodiment uses a saturation temperature detection circuit 26 instead of the pressure sensor 21 of the third embodiment, and is a saturation temperature detection means that directly detects the saturation temperature instead of pressure. A certain temperature sensor 27 detects the temperature. This detection circuit 26 is composed of a heat exchanger 29, a capillary tube 28, and a humidity sensor 27. The refrigerant at the outlet of the compressor 1 is cooled by the heat exchanger 29, and becomes a two-phase refrigerant in the capillary tube 28 until it reaches the suction pressure of the compressor 1. It is depressurized, becomes a low-temperature two-phase refrigerant, and by exchanging heat with N29, it becomes a low-pressure refrigerant with the enthalpy of the refrigerant at the compressor outlet, completing the cycle. The Mollier diagram showing the state of the refrigerant in the saturation temperature detection circuit of the multi-room air conditioner according to the fourth embodiment is the same as FIG. 6 in the second embodiment, so the explanation will be omitted. In this embodiment, the saturation temperature t is directly detected in step 541 during cooling operation and step 541 during heating operation in the flowchart of the second embodiment. Furthermore, in the first to fourth embodiments, although not shown, if the temperature of the piping near the center of the indoor/outdoor heat exchanger is detected, the high pressure saturation temperature during cooling/heating operation can also be detected. Not even.

【Effect of the invention】

As described above, in the multi-room air conditioner of the present invention, the branch unit is provided with a heat exchanger for mutually exchanging heat between the gas side branch pipe, the liquid side branch pipe, and the gas pipe and the liquid pipe. The refrigerant circuit is configured by arranging an expansion valve driven by an electric signal, and the control means controls the refrigerant to be appropriately distributed according to the capacity of each indoor unit while keeping the subcool constant during cooling operation. During cooling operation, the subcooling of the liquid side branch pipe section, that is, the outlet of multiple indoor heat exchangers, can be kept constant, so the refrigerant distribution performance is good, and there is no need for a receiver or refrigerant recovery circuit. Since construction can be completed halfway with paired piping, it is possible to reduce the area occupied by pipe shafts in buildings, etc. and the cost of piping work. Furthermore, since the indoor heat exchanger is always on the high-pressure side circuit during heating operation, no refrigerant noise is generated when the indoor unit is additionally operated. Furthermore, since the indoor unit does not require a diaphragm mechanism, it is possible to combine one outdoor unit with a standard indoor unit in which one indoor unit is used. Furthermore, in another aspect of the present invention, the same effect as described above can be achieved by controlling the temperature of the gas side branch pipes to be uniform while keeping the subcool constant during cooling operation using the control means.

[Brief explanation of the drawing]

FIG. 1 is a refrigerant circuit diagram of a multi-room air conditioner according to a first embodiment of the present invention, FIG. 2 is a block diagram of a control means for a multi-room air conditioner according to the first embodiment, and FIG. Flowchart 1 for explaining an example of the control of the expansion valve during the cooling operation by the control means of the first embodiment, and FIG. 4 illustrate an example of the control of the expansion valve during the FJ air conditioner operation by the control means of the first embodiment. Flowchart 1. FIG. 5 is a refrigerant circuit diagram of the multi-room air conditioner according to the second embodiment, and FIG. 6 is a flowchart of the saturation temperature detection circuit of the multi-room air conditioner according to the embodiment of FIG. A Mollier diagram showing the state of the refrigerant, FIG. 7 is a refrigerant circuit diagram of a multi-room air conditioner according to the third embodiment of the present invention, and FIG. 8 is a control means for the multi-room air conditioner according to the third embodiment. , FIG. 9 is a flowchart explaining an example of control of the expansion valve during cooling operation by the control means of the third embodiment, and FIG. 10 is a refrigerant circuit diagram of a multi-room air conditioner according to the fourth embodiment. , FIG. 11 is a refrigerant circuit diagram of a conventional multi-room air conditioner, and FIG. 12 is a characteristic diagram showing the relationship between the refrigerant state at the outlet of the heat exchanger and the average heat transfer coefficient.
Figures 13(,) and (b) are partially cutaway schematic front and side views showing the connection state of the refrigerant circuit of a general heat exchanger, and Figure 14 shows one indoor unit for one outdoor unit. FIG. 15 is a refrigerant circuit diagram of a general air conditioner that is used with connected units, and FIG. 15 is a refrigerant circuit diagram of another conventional multi-room air conditioner. In the figure, 1.Compressor, 2.4-way switching valve, 3.Outdoor heat exchanger, 4.Accumulator, 5.Outdoor unit, 6.Heat exchanger, 7.Gas piping, 8.Liquid. Piping, 9a, 9b. 9 c = gas side branch pipe, 10a, 10b, 10c,
- Liquid side branch pipe, lla, llb, 1lc - expansion valve, 14
... Branch unit, 15a, 15b, 15cm heat exchanger, 16a, 16b, 16cm indoor unit, 17a, 17b,
17cm gas side branch connection piping, 18a, 18b, 18c
--- Wave harmonic branch connection piping, 19... Gas side main connection piping,
20... Wave harmonic main connection piping, 21... Pressure sensor, 22
, 23a, 23b, 23c. 24d-24f-thermistor, 24a, 24b. 24c... Capacity setting switch, 25... Control means. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (2)

[Claims] (1) An outdoor unit that can switch between air conditioning and heating, in which a compressor, four-way switching valve, outdoor heat exchanger, and accumulator are sequentially connected to form a refrigerant circuit, a gas-side branch pipe that branches the gas pipe into multiple parts, and a liquid pipe. The liquid side branch pipe has multiple branches, the gas pipe and the liquid pipe are equipped with a heat exchanger to exchange heat with each other, and the liquid branch pipe is connected in series with an expansion valve driven by an electric signal. A refrigeration cycle is constructed by connecting a branch unit with a built-in indoor heat exchanger and a plurality of indoor units each having a built-in indoor heat exchanger through a pair of main connecting pipes and multiple pairs of branch connecting pipes, and connecting the liquid side branch pipes and outdoor heat a temperature detector disposed on the cooling outlet pipe of the exchanger, a detection means for detecting the high pressure or saturation temperature on the output side of the compressor, a capacity setting switch for setting the capacity of the plurality of indoor units, and the temperature A control means for controlling the expansion valve based on the temperature and pressure obtained by the detector or the pressure or saturation temperature obtained by the saturation temperature detection means and the signal from the capacity setting switch. Room air conditioner. (2) An outdoor unit that can be switched between cooling and heating, in which a compressor, a four-way switching valve, an outdoor heat exchanger, and an accumulator are sequentially connected to form a refrigerant circuit, and a gas side branch pipe that branches the gas piping into multiple parts;
The liquid side branch pipe that branches the liquid pipe into multiple parts, and the gas pipe and the liquid pipe are equipped with a heat exchanger to mutually exchange heat, and the liquid branch pipe is connected in series with an expansion valve that is driven by an electric signal. A refrigeration cycle is constructed by connecting the branch unit configured as shown in FIG. , a temperature detector disposed in the liquid side branch pipe and the cooling outlet pipe of the outdoor heat exchanger, and a detection means for detecting the high pressure or saturation temperature on the output side of the compressor, and the humidity detected by each of the humidity detectors. 1. A multi-room air conditioner, comprising: a control means for controlling the expansion valve based on the temperature obtained by the expansion valve, and the pressure or saturation temperature obtained by the pressure or saturation temperature detection means.