JP3381753B2 - Air conditioning system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioning system of a type in which a refrigerant is circulated from an outdoor unit to an indoor unit during cooling.

[0002]

2. Description of the Related Art In this type of air conditioning system, FIG.
As shown in FIG. 1, the outdoor unit 1 that operates as a condenser during cooling
, The liquid refrigerant is gravity flowed down to the indoor unit 2 that operates as an evaporator, or is pressure-fed using a pump, is evaporated in the evaporation coil 7 of each indoor unit 2 and is returned to the outdoor unit 1 as a refrigerant vapor. , The opening degree of the expansion valve 4 interposed on the upstream side of each indoor unit 2, the temperature difference detected by the refrigerant temperature sensors 5a and 5b provided at the inlet and outlet of the outdoor unit 2 (superheat degree = Tb-Ta). Is controlled to be a constant value. This allows the heat exchange to be effectively performed by changing the state of the refrigerant liquid at an appropriate position in the evaporation coil 7, and
This is to prevent the refrigerant from becoming unevenly distributed to the indoor unit 2 having a small indoor load due to an increase in the flow resistance of the refrigerant due to the active evaporation of the refrigerant in the indoor unit 2 having a large indoor load.

The reason why the state of the refrigerant in the evaporation coil 7 of the indoor unit 2 is monitored by the degree of superheat, that is, the temperature difference between the inlet and outlet temperature sensors 5a and 5b is that the state inside the coil 7 normally changes. Temperature difference between the entrance and the exit (Tb-T
Although a) is about 5 ° C., since the outdoor unit 1 is on / off controlled, the fluctuation range of the temperature of the refrigerant sent from the outdoor unit 1 is relatively large, for example, 7 ± 5 ° C., and therefore the outlet temperature This is because it is not possible to accurately detect the presence or absence of a state change in the coil 7 or the liquid surface position only with the coil. Further, since the variation width of the temperature on the inlet side of the evaporation coil 7 is large as described above, it is usual to set the target value of the temperature difference to a large value.

[0004]

In the above system, when the outdoor unit 1 is on / off operated in response to a change in the cooling load, a partial load operation is performed when some of the plurality of indoor units 2 are operating. The outdoor unit 1 is "off" to "low"
Alternatively, when the temperature is switched from “low” to “high”, the outlet temperature and pressure of the outdoor unit 1 decrease, so that each indoor unit 2
The pressure in front of the expansion valve 4 also decreases. However, at that time, the temperature difference between the inlet and outlet of the indoor unit 2 does not change suddenly, so the expansion valve 4
Does not change, and as a result, the amount of refrigerant supplied to the indoor unit 2 becomes insufficient due to the pressure drop before the expansion valve, and the capacity of the indoor unit 2 decreases.

Of course, in such a case, the temperature difference (Tb-Ta) detected by the temperature sensors 5a and 5b at the inlet and outlet becomes larger than the target superheat degree, so the expansion valve 4 is opened to correct this. Directionally controlled, which is temperature sensor 5
a, 5b after detecting the rise in temperature difference,
Moreover, since the opening degree of the expansion valve 4 is only corrected little by little, a sudden change in the refrigerant delivery pressure cannot be followed, and there is a problem that a considerable time delay occurs until the room temperature returns to normal. The present invention solves the above problems and provides an air conditioning system of this type in which the superheat control of the indoor unit 1 can follow a discontinuous change in the refrigerant pressure due to a sudden change in the load of the outdoor unit. It is intended.

[0006]

The present invention is based on FIG. 1 and Table 1.
As shown in FIG. 3, the refrigerant condensed in the outdoor unit 1 is sent to the plurality of indoor units 2, the refrigerant is evaporated in each indoor unit 2 and returned to the outdoor unit 1, and the branch refrigerant on the upstream side of each indoor unit 2 In the air conditioning system, the opening degree of the expansion valve 4 provided in the pipe 3 is controlled so that the temperature difference (Tb-Ta) of the refrigerant at the inlet and outlet of the indoor unit 2 becomes a predetermined value.
Depending on the temperature or pressure (Claim 1) detected by the refrigerant temperature sensor 12 or the refrigerant pressure sensor provided at the outlet of the outlet, if necessary, after a certain delay time (Claim 2) or the detected temperature. Alternatively, a means for switching the control target value of the temperature difference (Tb-Ta) to a plurality of stages according to the time rate of change in pressure (claim 3) is provided.

[0007]

In the conventional configuration of FIG. 2, when the load suddenly changes due to, for example, one of the plurality of indoor units 2 becoming unloaded, the outdoor unit 1 detects this by the delivery temperature T or pressure of the refrigerant liquid. Then, in Table 4, the refrigerator input is switched from “high” to “low” or from “low” to “off”, but the target superheat degree (difference between inlet and outlet temperatures) is 6.0 ° C. and is constant. Temperature difference (Tb-Ta) even if the temperature T changes
Since there is no sudden change, there is a considerable time delay until the opening degree of the expansion valve 4 is corrected to some extent, so that the refrigerant flows more than necessary and the indoor air is temporarily supercooled.
There was a drawback that it took time to restore the room temperature to normal. On the other hand, according to the configuration of the present invention in FIG. 1, as shown in Table 1, the refrigeration input of the outdoor unit 1 is discontinuously changed to “OFF”, “Low”, “High” at the same time when the load suddenly changes. Since the superheat degree which is the control target of the expansion valve 4 is also switched, the temperature difference (Tb-Ta) of the refrigerant at that time largely deviates from the target superheat degree, and therefore the expansion valve 4
The degree of opening can be corrected immediately and significantly to cope with a sudden change in load.

According to the second aspect of the invention, the change in the refrigerant temperature or the pressure has a large inertia, and after the load is changed suddenly and the refrigerating input of the outdoor unit is switched, the effect thereof is the change in the outlet temperature T or the pressure. Since it takes some time to appear, the timing for opening and closing the expansion valve 4 may be too early depending on the conditions such as the system scale, and a delay time is provided to adjust this. Further, according to the configuration of claim 3, it is not necessary to consider the delay time,
Moreover, in order not to miss the timing of opening and closing the expansion valve 4, when the time rate of change in temperature exceeds a certain value, it is predicted that a peak or a trough of the temperature curve will come after a certain time, and the target superheat degree is set in advance. It is designed to be switched.

[0009]

FIG. 1 shows an embodiment of an air conditioning system according to the present invention. The outdoor unit 1 is, for example, an absorption refrigerator 1a.
And a cooling tower 1b, which is installed at a position higher than any of the plurality of indoor units 2 such as on the roof of a building, and the refrigerant liquid condensed by the condenser of this outdoor unit 1 (for example, R22,
R134a) is allowed to naturally flow down to the plurality of indoor units 2 through the refrigerant pipe 8 on the sending side by its own weight to evaporate the refrigerant in each indoor unit 2 and to the outdoor unit 1 through the refrigerant pipe 7 on the returning side. It is designed to be refluxed. In each indoor unit 2, the indoor air sucked by the fan 6 is cooled by the evaporation coil 7 and blown out into the room.
The temperature rise (Tb-Ta) in the evaporation coil is monitored by the refrigerant temperature sensors 5a and 5b provided at the inlet and outlet of the evaporator, and the opening degree of the expansion valve 4 is proportionally controlled by this detection output, whereby the evaporation coil It is controlled so that the evaporation of the refrigerant is completed at an appropriate position within 7. Reference numeral 10 is a control device for the indoor unit 2.

On the other hand, the temperature T of the refrigerant sent from the outdoor unit 1
Is output from a refrigerant temperature sensor 12 provided in the refrigerant pipe 8 near the outlet of the outdoor unit 1, and the gas burner 1 of the refrigerator is
Fuel control valve 13 for supplying fuel gas to No. 4 is set to "high""low"
By controlling in three stages of “OFF”, the control signals are maintained in a certain range. The control signals of these three stages are sent to the fuel control valve 13 and, at the same time, from the control device 11 of the outdoor unit 1 to the indoor unit 2. It is also sent to the control device 10 of FIG. 1 and used as a signal for switching the superheat degree, which is the control target of the expansion valve 4, in three steps. Table 1 shows the refrigerant delivery temperature T of the outdoor unit 1,
It shows the relationship between the fuel supply amount that is the input of the absorption refrigerator 1a and the target superheat degree (Tb-Ta) of the expansion valve 4 of the indoor unit 2.

In Table 1, when the load of the outdoor unit 1 does not fluctuate much, the refrigerator 1a is refrigerating with a "low" fuel supply amount, and at this time, the indoor unit 2 responds to changes in room temperature. Then, the temperature of the room temperature is adjusted so as to maintain a constant value by the change in the opening degree of the expansion valve 4 in proportion to the change in the outputs of the refrigerant temperature sensors 5a and 5b (deviation from the superheat degree of 6.0 ° C.). Here, when the indoor units 2 in the other rooms all simultaneously start operating and the load of the outdoor unit 1 rises above a certain range and, for example, the temperature T of the temperature sensor 12 exceeds 7 ° C., control is performed. The device 11 switches the outdoor unit input, that is, the fuel control valve 13 of the refrigerator to "high", and at the same time, the control device 1
The target degree of superheat for controlling the expansion valve 4, that is, the temperature difference between the temperature sensors 5a and 5b (Tb-T).
The target value of a) is switched to 5.0 ° C. Therefore expansion valve 4
The opening degree, which has been controlled in the vicinity of the superheat degree of 6.0 ° C. until now, is controlled in the opening direction by the amount corresponding to 1.0 ° C. at a stroke, and the temperature T of the refrigerant sent from the outdoor unit 1 is controlled. Respond swiftly to the sudden rise in.

In this respect, in the conventional method (Table 4) in which the target superheat degree is not switched, the temperature of the refrigerant entering the indoor unit 2 starts to rise due to the increase in the load of the outdoor unit 1, and the evaporation in the evaporation coil 7 is increased. Since the point moves to the inlet side, the degree of superheat is 6.0.
Although the temperature increases above 0 ° C., the change from the expansion valve 4 is very small because the deviation from 6.0 ° C. is still small immediately after switching, and the sudden change in load cannot be followed. However, according to the method of the present invention, since the target degree of superheat switches to 5.0 ° C. immediately after switching, the deviation from the target increases at once, and the expansion valve 4 does not have to wait for the temperature of the temperature sensor 5b to rise. It can respond immediately and respond to sudden changes in load. It should be noted that as the scale of the system increases, the time until the effect of the sudden change in load appears in the indoor unit 2 also increases, and the timing of switching the target superheat degree may occur too early. In such a case, a certain delay time may be provided between the switching time point of the outdoor unit input and the switching time point of the target superheat degree by utilizing the timekeeping mechanism of the microcomputer constituting the control device 11. .

Table 2 shows another embodiment of the present invention. The target degree of superheat of the indoor unit 2, that is, the temperature sensors 5a, 5
A plurality of control target values of the temperature difference (Tb-Ta) detected by b are determined according to the time change rate (dT / dt) of the temperature T detected by the refrigerant temperature sensor 12 provided at the outlet of the outdoor unit 1. It is provided with a means for switching between stages. This is because the control of the refrigerant delivery temperature from the outdoor unit 1 has a large inertia, the refrigerant delivery temperature T exceeds 7 ° C., and the outdoor unit input is “high”.
After switching to, the sending temperature T continues to rise for a while, and if the load fluctuates significantly, for example, 12
Since the temperature may rise to ℃, when the gradient of rise or fall of the refrigerant delivery temperature becomes a certain level or more, a signal for switching the target superheat degree is sent to the indoor unit 2 in advance, and the correction operation of the expansion valve 4 is started. It was made to let. According to this configuration, the target superheat degree is switched after waiting for the effect of the switching of the refrigerator input to actually appear in the outlet temperature, so it is not necessary to consider the delay time as described above. The time rate of change (dT / dt) of the temperature can be easily obtained by, for example, reading the output of the temperature sensor 12 at intervals of 30 seconds and taking the difference from the previous data.

Table 3 shows still another embodiment. The air volume of the fan 6 of the indoor unit 2 is the indoor temperature, that is, the indoor unit 2
3 levels of "strong""medium""weak" automatically by the output of a temperature sensor (not shown) provided at the air intake port, but when the manual switch is operated. The switching of the fan air volume causes a sudden change in the load of the indoor unit 2 to move the evaporation point in the evaporation coil 7, which lowers the heat exchange efficiency and reduces the heat exchange efficiency in the return refrigerant pipe 9. Since the liquid refrigerant mixes and hinders the circulation of the refrigerant, the switching of the target superheat degree is performed by the fan air flow rate of the indoor unit 2 in each of the three stages depending on the refrigerant delivery temperature of the outdoor unit 1 described above. It can be done in stages.

[0011]

As described above, according to the configuration of the present invention, when the load of the outdoor unit 1 suddenly changes, the superheat degree which is the control target of the expansion valve 4 is also switched at the same time, so the refrigerant at that time is changed. That is, the temperature difference of 1 largely deviates from the control target value (target superheat degree). Therefore, the opening degree of the expansion valve 4 can be corrected immediately and greatly to cope with a sudden change in the load of the outdoor unit 1. There are advantages. In the above-described embodiment, the load fluctuation of the outdoor unit 1 is detected by the refrigerant temperature sensor 12 provided at the outlet of the outdoor unit 1, but the same effect can be obtained by detecting the pressure change with the temperature. can get.

[Table 1]

[Table 2]

[Table 3]

[Table 4]

[Brief description of drawings]

FIG. 1 is a schematic system diagram of an embodiment of the present invention.

FIG. 2 is a schematic system diagram of a conventional example.

[Explanation of symbols]

1 outdoor unit 2 Indoor unit 3 branch refrigerant piping 4 expansion valve 5a Temperature sensor at indoor unit inlet 5b Indoor unit outlet temperature sensor 6 fans 7 evaporation coil 8 Feeding side refrigerant piping 9 Return side refrigerant piping 10 Indoor unit control device 11 Outdoor unit control device 12 Temperature sensor at outdoor unit outlet 13 Fuel control valve 14 gas burner

─────────────────────────────────────────────────── ─── Continuation of the front page (73) Patent holder 390003333 Shinko Industrial Co., Ltd. 1-4-5 Minamimorimachi, Kita-ku, Osaka-shi, Osaka (73) Patent holder 000003621 Takenaka Corporation Central Osaka-shi, Osaka 4-1-1, Honcho, Ku (72) Noboru Kobayashi 4-1-2, Hirano-cho, Chuo-ku, Osaka City In Osaka Osaka Gas Co., Ltd. (72) Takeshi Okumura 4-1-1, Hirano-cho, Chuo-ku, Osaka No. 2 Osaka Gas Co., Ltd. (72) Inventor Seiichiro Fujimaki 1-5-20 Kaigan, Minato-ku, Tokyo Tokyo Gas Co., Ltd. (72) Inventor Toshiharu Shimizu 19-18 Sakurada-cho, Atsuta-ku, Nagoya Toho Gas Co., Ltd. (72) Inventor Shinji Tonmiya 1-42 Mita, Minato-ku, Tokyo Yazaki Corporation (72) Inventor Yasutoshi Yoshida 1-4-5 Minamimorimachi, Kita-ku, Osaka Shinko Industrial stock In-house (72) Inventor Nozomu Kusumoto 4-1-1-13 Honmachi, Chuo-ku, Osaka Inside Takenaka Corporation (56) References JP-A-3-195838 (JP, A) JP-A-7-4758 (JP, A) ) JP-A-3-181727 (JP, A) JP-A-3-186128 (JP, A) JP-A-2-89940 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) F24F 5/00

Claims (3)

(57) [Claims] 1. A refrigerant condensed in an outdoor unit is sent to a plurality of indoor units, and the refrigerant is evaporated in each indoor unit to be returned to the outdoor unit, and is also installed in a branch refrigerant pipe on the upstream side of each indoor unit. In an air conditioning system in which the opening of the expansion valve is controlled so that the temperature difference detected by the refrigerant temperature sensor provided at the inlet / outlet of the indoor unit becomes a predetermined value, the refrigerant temperature sensor provided at the outlet of the outdoor unit Alternatively, according to the temperature or pressure detected by the refrigerant pressure sensor, the refrigerating input of the outdoor unit is switched to a plurality of stages, and a means for switching the control target value of the temperature difference to a plurality of stages is provided. 2. The air conditioning system according to claim 1, wherein a constant delay time is provided between a switching time point of the refrigeration input of the outdoor unit and a switching time point of the control target value of the temperature difference. 3. The refrigerant condensed in the outdoor unit is sent to a plurality of indoor units, the refrigerant is evaporated in each indoor unit to be returned to the outdoor unit, and the refrigerant is interposed in the branch refrigerant pipe on the upstream side of each indoor unit. In an air-conditioning system that controls the opening of the expansion valve so that the temperature difference between the refrigerant at the inlet and outlet of the indoor unit becomes a predetermined value, the control target value of the temperature difference is the refrigerant temperature at the outlet of the outdoor unit. An air conditioning system provided with means for switching to a plurality of stages according to a time change rate of temperature or pressure detected by a sensor or a refrigerant pressure sensor.