JPH0723794B2 - Air conditioner - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner provided with an electric expansion valve whose opening can be adjusted, and more particularly to limiting the maximum opening of the electric expansion valve to perform wet operation. Regarding the improvement of what was made to prevent.

(Prior Art) Conventionally, in a multi-type air conditioner configured by connecting a plurality of indoor units in parallel to one outdoor unit, the multi-unit air conditioner is provided in each high-pressure liquid refrigerant branch pipe of each indoor unit. When the capacity control for controlling the opening of the electric expansion valve according to the deviation between the room temperature and the set temperature and performing the refrigerant distribution according to the load in each room, when the deviation between the room temperature and the set temperature is large, The degree of opening of the electric expansion valve becomes too large, and the wetness of the refrigerant becomes excessive during cooling operation, while the pressure difference between the gas pipe and liquid pipe becomes too small during heating operation, resulting in piping design. There is a problem that the upper constraint becomes stronger.

In order to improve such a problem, conventionally, for example, as disclosed in JP-A-60-108633, while controlling the opening of the electric expansion valve in proportion to the deviation between the room temperature and the set temperature, During the heating and cooling, the refrigerant superheat is measured by the temperature sensors provided at the outlet and inlet pipes of each indoor heat exchanger, and the maximum opening of the electric expansion valve is limited so that the refrigerant superheat does not fall below a certain value. There is an attempt to solve the above problem due to the excessive opening of the electric expansion valve.

(Problems to be Solved by the Invention) However, in the above-mentioned conventional one, since the degree of superheat of the refrigerant at the outlet of the indoor heat exchanger is used as a control parameter for limiting the maximum opening degree of the electric expansion valve, It is necessary to provide temperature sensors near the outlet and inlet of the indoor heat exchanger to measure the temperature of the refrigerant at each place.

Therefore, since two or more sensors are required for each indoor unit and the variation in the measured value due to the temperature variation of the refrigerant and the gas-liquid mixing is large, the variation in the measured value of the superheat degree, which is a control parameter, is large and the hunting is large. There is a drawback in that

The present invention has been made in view of such a point, and an object thereof is to control the opening degree of the electric expansion valve and perform capacity control to the indoor unit other than the superheat degree as described above. The stable control parameter is used to limit the maximum opening degree of the electric expansion valve, and to perform stable control while preventing problems such as wet operation.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the solution means of the present invention is, as shown in FIG. 1, a compressor (1) and an outdoor heat exchanger (3).
In contrast to one outdoor unit (A) with a built-in and a plurality of indoor units (B) with a built-in indoor heat exchanger (5),
The target is an air conditioner in which (E) is connected in parallel.
An electric expansion valve (6) disposed in each of the high pressure liquid refrigerant branch pipes of each of the indoor units (B), (E) ...
Control for controlling the opening degree (U) of the electric expansion valve (6) corresponding to the deviation between the intake air temperature (Ta) of each indoor unit (B), ... (E) and its set temperature (Tr). And means (F). Further, the control means (F) is based on the deviation between the intake air temperature (Ta) of each indoor unit (B), ... (E) and the refrigerant evaporation temperature Te or the refrigerant condensation temperature Tc of the indoor heat exchanger (5). ), The maximum opening degree limiting means (J) for limiting the maximum opening degree (Umax) of the electric expansion valve (6) is provided.

(Operation) With the above-described configuration, in the present invention, the electric expansion valve (6) whose opening is controlled according to the deviation (Ta to Tr) between the room temperature (Ta) and the set temperature (Tr) controls the inside of each room. Appropriate refrigerant distribution is made according to the state. At that time, when the temperature difference (Ta to Tr) is too large and the opening degree of the electric expansion valve (6) becomes excessively large, the indoor unit (B), (E) ... Intake air temperature Ta and refrigerant evaporation temperature Te
Alternatively, since the maximum opening degree of the electric expansion valve (6) is limited to the value Umax corresponding to the deviation from the condensation temperature Tc, during the cooling operation,
The excessive opening of the electric expansion valve effectively prevents wet operation, and during the heating operation, the pressure difference between the gas pipe and the liquid pipe is effectively prevented from becoming too small, and stable without hunting or the like. Capacity control of the indoor unit is performed.

The maximum opening degree of the electric expansion valve (6) is limited according to the difference between the intake air temperature (Ta) and the refrigerant evaporation temperature (Te) or the condensation temperature (Tc). Since the temperature (Ta) can be detected using an existing thermostat, the number of sensors can be small.

(Embodiment) An embodiment of the present invention will be described below with reference to the drawings starting from FIG.

FIG. 2 shows a refrigerant piping system of a multi-type air conditioner to which the present invention is applied, where (A) is an outdoor unit, (B),
(C) and (D) are indoor units connected in parallel to the outdoor unit (A). Inside the indoor unit (A), a compressor (1) whose capacity is controlled by an inverter (1a) that makes the power supply frequency variable, and a solid line in the figure during cooling operation and a dashed line in the figure during heating operation The four-way switching valve (2) for switching as described above and the outdoor heat exchanger (3) are built in as main equipment, and the respective equipments (1) to (3) respectively flow the refrigerant through the refrigerant pipe (8). Connected possible. Further, the indoor units (B) ... (D) have the same configuration, each is provided with an indoor heat exchanger (5), and the high pressure liquid refrigerant pipe (8) of each indoor heat exchanger (5) has a refrigerant. Electric control valves (6) for adjusting the flow rate and reducing the pressure are connected to each other so that the refrigerant can flow.

Further, (7) is a room temperature thermostat that is installed near the air intake port of the main body casing of each of the indoor units (B) ... (D), and detects the intake air temperature, and (9) is for the outdoor unit (A). Outdoor control unit to control the operation, (1
0) is an indoor control unit that is connected in parallel to the outdoor control unit (9) by a signal line and controls the individual operation of each indoor unit (B) ... (E). Is the electric expansion valve according to the deviation value ΔTr (= Ta−Tr) between the set value Tr output from the room temperature thermostat (7) and the intake air temperature Ta as shown in the signal transmission path in FIG. A control circuit (F) as a control means for controlling the opening degree of (6), and a storage circuit (G) for storing values of a predetermined refrigerant evaporation temperature Te and condensation temperature Tc and others.
And the deviation ΔTe (= Ta−Te) or ΔTc (= Tc−) between the intake air temperature Ta and the evaporation temperature Te or the condensation temperature Tc.
Ta) and a saturation circuit that outputs a saturation signal that limits the maximum opening of the electric expansion valve (6) to the control circuit (F) according to the output signal of the comparison circuit (I). The circuit (I) is incorporated.

In FIG. 2, during cooling operation, the four-way switching valve (2) is connected as shown by the solid line, the flow of the refrigerant discharged from the compressor (1) is in the direction of the solid line arrow, and the refrigerant is the outdoor heat. Each indoor unit (B) through the exchanger (3) ...
The electric expansion valve (6) provided in the high pressure liquid refrigerant branch pipe of (E) receives a throttling action, is vaporized in the indoor heat exchanger (5), and again passes through the refrigerant pipe (8) to the compressor (1). ) Return to.

In the flow of the refrigerant, when the refrigerant is subjected to the throttling action by the electric valve (6), the indoor control unit (10)
Controls the opening degree of the electric expansion valve (6) by the following procedure.
First, the control circuit (F) receives the signal from the room temperature thermostat (7) and, as shown by the solid line in the graph of FIG. 4 (a), the deviation value (Ta) between the intake air temperature Ta and the set temperature Tr. (-Tr), the opening U of the electric expansion valve is linearly increased to continuously control the capacity of each indoor unit (B) ... (E). At this time, a deviation ΔTe between the intake air temperature Ta and the refrigerant evaporation temperature Te obtained from the storage circuit (G) is calculated in the comparison circuit (H) to calculate the saturation circuit (I).
Is the maximum opening Umax of the electric expansion valve (6) based on the relational expression of the maximum opening Umax of the electric expansion valve (6) and ΔTe stored in advance in the storage circuit (G) according to the deviation ΔTe. To decide. FIG. 5A shows the relationship between the maximum opening Umax and ΔTe stored in advance in the storage circuit (I). The maximum opening Umax is proportional to the increase in the deviation ΔT. The maximum opening Umax corresponding to the deviation ΔTe is determined according to the relational expression of the solid line graph or the broken line graph in which Umax linearly increases. The control circuit (F) receives the saturation signal Umax of the saturation circuit (I) and limits the maximum opening of the electric expansion valve (6) to the position of the broken line Umax shown in the graph of FIG. .

Next, during the heating operation, the four-way switching valve (2) is switched as indicated by the broken line, and the flow of the refrigerant is in the direction of the broken line arrow, and the indoor heat exchange of each indoor unit (B) ... (E) is performed. When the electric expansion valve (6) whose opening is controlled by the indoor control unit (10) is subjected to decompression after passing through the device (5), the indoor control unit (10) is operated by the following procedure. The opening degree of the expansion valve (6) is controlled. First, as shown by the solid line in the graph of Fig. 4 (b), the control circuit (F) changes the opening degree U to the minimum opening degree Umin according to the value of (Tr-Ta).
To linearly increase each indoor unit (B) ... (E)
The ability is controlled continuously. At this time, in the comparison circuit (H), a deviation ΔTc between the refrigerant condensing temperature Tc obtained from the storage circuit (G) and the suction air temperature Ta is calculated,
The same signal transmission as in the cooling operation is performed to determine the maximum opening Umax corresponding to the deviation ΔTc. Here, as shown in FIG. 5B, the storage circuit (G) stores a relational expression of a solid line graph proportional to an increase in the deviation ΔTc or a linearly increasing broken line graph. There is. The control circuit (F) receives the saturation signal Umax of the saturation circuit (I) and limits the maximum opening degree of the electric expansion valve (6) to the position of the broken line Umax shown in the graph of FIG. .

In the indoor control unit (10), the storage circuit (G), the comparison circuit (H), and the saturation circuit (I).
And constitute maximum opening limiting means (J) for limiting the maximum opening of the electric expansion valve (6) whose opening is controlled by the control means (F) to Umax.

The inverter (1a) keeps the refrigerant evaporation temperature of the system constant according to a change in the temperature condition and the actual number of indoor units (B) ... (E) in response to a command signal from the outdoor control unit (9). As described above, the capacity control of the compressor (1) is performed. Further, in FIG. 2, (15) is an outdoor electric expansion valve arranged in the outdoor unit (A), which is almost fully opened during the cooling operation, gradually depressurizes the refrigerant, and is squeezed during the heating operation to exhaust the refrigerant outside the room. The opening degree is controlled by the outdoor control unit (9) so as to be vaporized by the heat exchanger.

As described above, the opening degree of the electric expansion valve (6) is set to the intake air temperature.
The indoor unit (B) is controlled according to the deviation (Ta to Tr) between Ta and the set temperature Tr of the room temperature thermostat (7).
When continuously controlling the capacity of (E), the opening U of the electric expansion valve (6) is set to the maximum opening by the limiting means (J).
When the deviation (Ta-Tr) is large during the cooling operation, the opening U of the electric expansion valve (6) is prevented from becoming too large during the cooling operation to effectively prevent the wet operation. During heating operation,
When the deviation (Tr to Ta) is large, it is possible to effectively prevent the opening U of the electric expansion valve (6) from becoming too large and the pressure difference between the gas pipe and the liquid pipe from becoming too small.

Further, in the above embodiment, the room temperature thermostat (7) attached to the apparatus is used for control, and the apparatus can be manufactured at a lower cost than the conventional method in which a superheat degree that requires many special sensors is used as a control parameter. Can be configured. At this time, since the maximum opening Umax set by the limiting means (J) is determined by the intake air temperature Ta, there is no abrupt change unlike the measurement of the degree of superheat or the degree of subcooling. ,
Stable control can be performed without causing hunting.

In the above example, the values set in advance while the evaporation temperature Te and the condensation temperature Tc of the refrigerant were set constant were stored in each indoor control unit (10), but there are variations in Te and Tc in the actual system. Therefore, if the measured Te and Tc are used to calculate ΔTe and ΔTc, and Umax is controlled, finer control is possible. As a method therefor, there are a method of directly using the measured value (continuous method) and a method of setting several kinds of modes in advance and selecting according to the measured value (mode method). Also,
Especially during cooling operation, even if ΔTe is the same, if the actual condensation temperature Tc of the system fluctuates, the refrigerant flow rate of the indoor heat exchanger (5) also fluctuates slightly. As shown in FIG. 6 (a), several modes in which the gradient of the Umax-ΔTe characteristic line was changed were set, and the measured Tc
Determines which mode to use (mode method)
Or, as shown in Fig. 7 (b), Umax-ΔTe
If the gradient of the characteristic line is changed between the upper limit value and the lower limit value (coefficient method), it is possible to perform more accurate control by correcting the gradient.

In FIG. 7, the evaporation temperature Te and the condensation temperature Tc of the refrigerant are measured,
It is a figure which shows the basic composition for continuously controlling the capacity of each indoor unit (B) ... (E) described in the said Example by the electric expansion valve (6), Comprising: A compressor (1), an inverter ( 1
a), the four-way switching valve (2), the outdoor heat exchanger (3), the outdoor unit electric expansion valve (4), the indoor heat exchanger (5), and the indoor unit electric expansion valve (6) are the same as those in the above embodiment. Similarly to the above, the refrigerant pipe (8) is connected. Further, a room temperature thermostat (7) is provided in the vicinity of the air suction port of the indoor units (B) ... (E) as in the above embodiment. In FIG. 7, (Pe) and (Pc) are a low-pressure side pressure sensor and a high-pressure side pressure sensor, respectively, provided in the compressor (1), both of which convert a pressure signal into an electric signal to perform outdoor control. It is connected to the unit (9 ') by electric wiring. Figure 8 shows the outdoor control unit (9)
FIG. 3 is a block diagram showing a basic signal transmission path of an indoor control unit (10). The outdoor unit (9 ') includes a conversion circuit (k) that receives signals from the low pressure side pressure sensor (Pe) and the high pressure side pressure sensor (Pc) and converts them into a temperature signal or a mode signal. The indoor control unit (10) includes a control circuit (F) as control means, a comparison circuit (H), and a saturation circuit (I) as in the above embodiment.
And a memory circuit (G '). Here, the signal transmission path from the conversion circuit (K) is the measured value by the continuous method.
When using Te or Tc, the configuration should be changed as shown by the solid line in FIG. 8, and when using the measured value Te or Tc by the mode method or measured value Tc by the coefficient method, as shown by the broken line in FIG. Yes, FIG. 8 shows a basic configuration. When the storage circuit (G ') uses the mode method, it transmits the value of Te or Tc to be selected according to the mode signal of the conversion circuit (K) to the comparison circuit (H), and FIG. Umax shown in graph b) or b)
And the relational expression of ΔTe are stored in the conversion circuit (K).
Um to be selected according to the mode signal or coefficient signal of Tc
According to the combination, the relational expression of ax and ΔTe is transmitted to the saturation circuit (I). The memory circuit (G ') is
When the set value Te or Tc is used, the internal configuration is the same as that of the above embodiment. The comparison circuit (H), the storage circuit (G '), and the saturation circuit (I) constitute a maximum opening limiting means (J') of the electric expansion valve (6).

In FIG. 7, the functions of the inverter (1a) and the outdoor electric valve (15) arranged in the outdoor unit (A) are the same as those in the above embodiment.

FIGS. 9 (a) to 9 (h) show various combinations of the mode method or the continuous method when the maximum opening Umax of the electric expansion valve (6) is controlled by using the measured value Te or Tc during the cooling operation. In the block diagram of the signal transmission path shown, (9) is an outdoor control unit, (K) is a conversion circuit incorporated in the outdoor control unit (9), (10) is an indoor control unit, and (J ') is the indoor unit. The maximum opening limiting means (J ') built in the control unit (10) is a signal Ta from the room temperature thermostat (7) and a measured value Te from the conversion circuit (K). Alternatively, the maximum opening Umax of the electric expansion valve (6) is limited by receiving a signal relating to Tc or using a preset value Te or Tc stored in advance (the control means (F) is omitted here). ing).

As a combination of the above Tc and Te, the set value Te is shown in FIG.
Fig. 9 (b) shows that when the set value (Te) and the measured value Tc (coefficient method) are used,
Figure (c) shows the measured value Te (continuous method) and the set value Tc, and Figure 9 (d) shows the measured value Te (continuous method) and the measured value Tc (mode method). Figure (e) shows the measured value Te (continuous method) and the measured value Tc (coefficient method).
Is the 9th value when the measured value Tc (mode method) and the set value Tc are used.
The figure (g) uses the measured value Te (mode method) and the measured value Tc (mode method), and the figure 9 (h) uses the measured value Te (mode method) and the measured value Tc (coefficient method). The signal transmission path at the time is shown.

Which of those combinations is used is selected according to the capacity of the air conditioner to be applied, the number of indoor units, and the required control accuracy. Especially when using the measured values by the continuous method or the coefficient method, stable control can be performed reliably, but when such accuracy is not required, the method using the measured values by the mode method is simpler and more detailed. It is a practical method that can be controlled.

FIGS. 10 (a) and 10 (b) are signal transmissions showing examples by the continuous method and the mode method, respectively, when the maximum opening Umax of the electric expansion valve (6) is controlled using the measured value Tc during heating. The block diagram of the route has the same configuration as that of FIG.

Fig. 10 (a) shows the measured value Tc (continuous method) and the set value Te, and Fig. 10 (b) shows the measured value Tc (mode method) and the set value Tc.
The signal transmission path when using is shown.

In the combination example of FIG. 10 (a), the control is performed simply and more finely than in the above-described embodiment, and in the combination example of FIG. 10 (b), the control is more accurate.

Further, although the set value Te is used in the above-described embodiment, when particularly precise control is required, the refrigerant pressure at the common pipe outlet of the electric expansion valve (6) is used as the pressure sensor during heating operation. It is possible to correct the fluctuation of the refrigerant flow rate that may be present in the system by using the refrigerant pressure equivalent saturation temperature Teo obtained by converting it into a temperature signal measured by the mode method as described in the case of the cooling operation, The maximum opening control of the electric expansion valve (6) can be performed by various combinations by the continuous method.

Instead of using the measured value Te or Tc in the continuous method as shown in FIG. 9 (c) or FIG. 10 (a) during the cooling operation or the heating operation described above,
As shown in FIG. 11, a formula for directly reading Umax from the value of Ta is set in advance in the memory circuit (G ′) of FIG. 8, and the mode number corresponding to the actually measured value Te or Tc is converted into the conversion circuit ( K)
If the relational expression selected from the above is transmitted to the saturation circuit (I), the saturation circuit (I) directly receives the value of Ta and Umax
Therefore, the comparison circuit (H ') can be omitted.

When the refrigerant pipe length is particularly long, the actual refrigerant evaporation temperature Teo is the value T measured by the pressure sensor (Pe).
It is higher than e by the pressure loss. At this time, the correction value ΔTe is determined from the frequency of the inverter, and Teo
(= Te + ΔTe) can be used instead of Te to perform accurate control.

(Effects of the Invention) As described above, according to the present invention, in the capacity control by the electric expansion valve of the indoor unit of the air conditioner, the suction air temperature without a sudden change and the evaporation temperature or the condensation temperature of the refrigerant are set. Since the maximum opening during the opening control of the electric expansion valve is limited by using the temperature difference of the above, during the cooling operation, the wet operation accompanying the changes in the actual number of indoor units and temperature conditions can be stabilized without hunting. It can be effectively prevented in the state. Further, during the heating operation, it is possible to effectively prevent the pressure difference between the gas pipe and the liquid pipe from becoming small, so that there is a margin in setting the pipe length difference after the branch pipe, the height difference, and the like.

Furthermore, the number of sensors used can be reduced,
The cost can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention. 2 to 11 show an embodiment of the present invention, FIG. 2 is a refrigerant system piping diagram thereof, FIG. 3 is a block diagram showing a signal path of the above embodiment, FIGS. 4 (a) and 4 (b). ) Are deviations (Ta to Tr) of the opening U of the electric expansion valve (6) during the heating and cooling operation, respectively.
Fig. 5 (a) is a graph showing the relationship between the maximum opening Umax and Δ
Fig. 5 (b) is a graph showing the relationship between Te, Fig. 5 (b) is a graph showing the relationship between Umax and ΔTc, and Fig. 6 (a) and (b) are Umax and Δ when the mode method and the coefficient method are used during cooling, respectively.
Fig. 7 is a graph showing the relationship between Te and the measured values Te or Tc.
FIG. 8 is a refrigerant system diagram showing an overall configuration when using the, and FIG. 8 is a block diagram showing a signal transmission path at that time. 9 (a) to (h) and FIGS. 10 (a) and (b) are schematic block diagrams showing examples of combinations of signal transmission paths when the measured value Te or Tc is used in various methods. (I)~
(H) is during cooling, and FIGS. 10 (A) and (B) are during heating operation. FIG. 11 is a graph for obtaining the relationship between Umax and Ta by another method. (1) ... Compressor, (3) ... Outdoor heat exchanger, (5) ... Indoor heat exchanger, (6) ... Electric expansion valve, (A) ... Outdoor unit, (B), (E) ... Indoor unit , (F) ... Control means, (J) ... Maximum opening limit means.

Continuation of the front page (56) Reference JP 62-258969 (JP, A) JP 60-108633 (JP, A) JP 49-19442 (JP, A) JP 60-108632 (JP , A) JP-A-58-156164 (JP, A)

Claims (1)

[Claims] 1. A plurality of indoor units (B) having an indoor heat exchanger (5) for one outdoor unit (A) having a compressor (1) and an outdoor heat exchanger (3). ), ...
In the air conditioner in which (E) are connected in parallel, the electric expansion valves (6) respectively arranged in the high pressure liquid refrigerant branch pipes of the indoor units (B), (E) ... B), ... (E) Electric expansion valve (6) corresponding to the deviation between the intake air temperature (Ta) and its set temperature (Tr)
Means (F) for controlling the opening degree (U), the intake air temperature (Ta) of the indoor units (B), ... (E) and the refrigerant evaporation temperature (Te) of the indoor heat exchanger (5). Alternatively, a maximum opening limiting means (J) for limiting the maximum opening (Umax) of the electric expansion valve (6) by the control means (F) based on the deviation from the refrigerant condensing temperature (Tc) is provided. A characteristic air conditioner.