CN1290838A - Composite air conditioner low temperature control method - Google Patents

Abstract

A low temperature control method for a composite air conditioner in which one outdoor unit is connected to one or more indoor units, comprising the following steps: a common operating procedure; opening the electronically controlled expansion valve of the operating indoor unit to a predetermined level to control The flow rate of refrigerant flowing through the indoor units in operation; and the low temperature control program, which is sequentially controlled according to the temperature change of the indoor heat exchangers in operation during the operation to prevent each indoor heat exchanger from freezing at low temperature Bypass valves, motor-controlled electronically controlled expansion valves, outdoor blowers and compressors. Therefore, regardless of the number of indoor units in operation and the cooling capacity, a cyclic operation of the refrigeration process can be formed.

Description

Composite air conditioner low temperature control method

The present invention relates to a non-inverter composite single-cooling air conditioner, in which one outdoor unit is connected with one or more indoor units and can simultaneously cool multiple rooms; in particular, it relates to a low-temperature control method for a composite air conditioner. Method Regardless of the number of operating indoor units and the cooling capacity, valves, outdoor blowers, and compressors are controlled only based on the average temperature of the operating indoor heat exchangers to prevent the heat exchangers from freezing.

As shown in FIG. 1 , generally, a composite air conditioner (such as three indoor units) is composed of a group of indoor units 10, 11, 12 respectively arranged in each room and an outdoor unit 20 arranged outside.

The outdoor unit 20 includes a compressor 30, an outdoor heat exchanger 40, an outdoor blower 41, a bypass valve 50, a first capillary 51, solenoid valves 60, 61, 62 for chambers A, B, and C, and valves for chambers A, B, and C. Capillary 70, 71, 72, main solenoid valve 80 and main capillary 81. When the bypass valve 50 is used for cooling a certain room, it bypasses a predetermined amount of refrigerant discharged from the outdoor heat exchanger 40, thereby adjusting the refrigerant flow rate of the indoor unit in operation; rooms A, B, The electromagnetic valves 60, 61, 62 of C are used for each indoor unit to open or close the flow of refrigerant, so that the initial state of each indoor unit 10, 11, 12 is selected for refrigeration according to the operating state (on/off). The capillary tubes 70, 71, 72 of chambers A, B, and C are connected to each indoor unit 10, 11, 12, so that the liquid refrigerant at room temperature and high pressure obtained after being cooled and condensed by the outdoor heat exchanger 40 is converted into a low-pressure, high-pressure refrigerant. Low temperature vaporizable refrigerant. The main solenoid valve 80 is used to discharge the refrigerant from the outdoor heat exchanger 40 and introduce the refrigerant into the capillary tubes 70, 71, 72 of the chambers A, B, and C when the air conditioner in a certain room is operating, thereby regulating the indoor units in operation. refrigerant flow. The main capillary 81 is used to reduce the vaporization pressure of the room temperature and high pressure liquid refrigerant cooled and condensed by the outdoor heat exchanger 40 when the indoor units in the second and third chambers are running. The indoor units 10, 11, 12 are equipped with indoor heat exchangers 90, 91, 92 and indoor blowers 100, 101, 102 respectively.

In the air conditioner with the above-mentioned structure, when the high-temperature, high-pressure gaseous refrigerant is discharged from the compressor 30 of the outdoor unit 20 and introduced into the outdoor heat exchanger 40, the outdoor heat exchanger 40 cools the high-temperature, high-pressure gaseous refrigerant. The agent is exchanged for heat, and the outdoor air blower 40 is used to blow air, thereby performing powerful cooling and condensation.

Referring to Fig. 2, if a certain room is cooled, the bypass valve 50 and the main solenoid valve 80 are opened to allow a certain amount of refrigerant to be discharged from the heat exchanger 40, bypassed by the bypass valve 50, and discharged by the outdoor heat exchanger. The room temperature and high pressure liquid refrigerant obtained after condensing 40 flows through the main solenoid valve 80 again.

Referring to Fig. 2, the room temperature and high pressure liquid refrigerant flowing through the main electromagnetic valve 80 flows into the capillary tube 70, 71 of the corresponding chamber A, B or C through one of the electromagnetic valves 60, 61 or 62 of the chamber A, B or C or 72 to obtain a low pressure and low temperature vaporizable refrigerant, which is then introduced into the indoor heat exchanger 90, 91 or 92 of the corresponding chamber A, B or C.

Therefore, when the low-temperature, low-pressure and easy-to-vaporize refrigerant regulated by the capillary tubes 70, 71, 72 of chamber A, B or C is vaporized and converted into gas, heat is carried out at the indoor heat exchanger 90, 91, 92. exchange, and utilize the indoor blowers 100, 101, 102 to blow air to cool down the indoor air. This cooled air is exhausted into the room to complete the cooling process. The low-temperature, low-pressure refrigerant after heat exchange at the indoor heat exchangers 90, 91, 92 of the chambers A, B, and C flows into the compressor 30 again, thereby performing cycle refrigeration.

In addition, referring to Fig. 2, when the other two chambers 2 and 3 are cooling at the same time, the bypass valve 50 and the main solenoid valve 80 are closed, allowing the room temperature and high pressure liquid refrigerant condensed by the outdoor heat exchanger 40 to flow through Main capillary 81, and flow into capillary 70, 71, 72 of chamber A, B, C through the electromagnetic valve 60,61,62 of two or three chambers, thus complete two chambers (chamber A+B, chamber B+C , room A+C) or three room (room A+B+C) refrigeration.

As mentioned above, when the refrigeration has been performed for a certain period of time, when the indoor blowers 100, 101, 102 are used to blow air for heat exchange, because of the discharge of cold air and the need for the vaporization of the refrigerant in the indoor heat exchangers 90, 91, 92 heat, the temperature of the indoor heat exchangers 90, 91, 92 decreases. When the temperature of the indoor heat exchanger drops below 0 degrees centigrade, the indoor heat exchangers 90, 91, 92 freeze, reducing the blowing volume of the indoor blowers 100, 101, 102. The freezing speed is thus further accelerated.

In order to solve the above problems, a low temperature control method is introduced below. This method controls the compressor 30, the outdoor blower 41 and the indoor blower 100, 101, 102 by detecting the temperature change of the indoor heat exchanger 90, 91, 92 during the cooling process, thereby preventing the indoor heat exchanger 90, 91, 92 from freezing .

Referring to Figure 3, when an indoor heat exchanger cools a certain room (one of the rooms A, B, and C), and its temperature is lower than -1 degrees Celsius for 6 minutes, the first step (high to low, low to Switching off) reduces the rotational speed (rev/min) of the outdoor blower 41 to perform the anti-freezing control program. In the first step of executing the anti-freezing control program, if the temperature of the indoor heat exchanger does not rise to 5 degrees Celsius within 3 minutes, then perform the second step of the anti-freezing control program, that is, turn off the compressor 30 and the outdoor blower 41, and Reduce the speed of the corresponding indoor blower for this room (one of the rooms A, B, C) (set to low speed (rpm)).

Referring to Figure 3, when multiple rooms (2 or 3 rooms) are being refrigerated, if the indoor exchanger of room A, B or C is lower than -1 degree Celsius for 6 minutes, the first step of the anti-freezing control program ( High to low, low to off conversion), that is, to reduce the rotating speed (rev/min) of the outdoor blower 41. In the first step of executing the anti-freezing control program, if the temperature of the indoor heat exchanger does not exceed 5 degrees Celsius within 3 minutes, then perform the second step of the anti-freezing control program, that is, turn off the compressor 30, the outdoor blower 41, and reduce The speed of the indoor blower for two rooms (room A+B, room B+C, room A+C) or three rooms (room A+B+C) (set to low speed (rpm)).

On the other hand, in the second step of the anti-freezing control program, if the temperature of the indoor heat exchanger rises to 5 degrees Celsius, the compressor 30, the outdoor blower 41, and the indoor blower of the operating indoor unit return to the front of the anti-freezing control program. normal operating state. In addition, if the temperature of the indoor heat exchanger exceeds 0 degrees Celsius within 6 minutes, the indoor unit stops counting for 6 minutes and operates in a normal operating state.

However, the above-mentioned conventional low-temperature control method of the composite air conditioner has the following problems. One is: in the case of cooling a room, no matter how much the load of the indoor unit in operation is, its bypass valve is always open, thereby reducing its cooling capacity in normal working conditions.

The second is: when cooling in multiple rooms, the loads of each indoor unit are different, and the temperature of the indoor heat exchanger with a high load is higher (due to the need for a higher cooling capacity) while the heat exchange in other low-load rooms The temperature is lower, thus causing freezing. Also, if any heat exchanger in a low-load room freezes, the anti-freeze control program (which is initially controllable) is executed, the speed of the outdoor blower 41 is changed or the compressor is turned off, causing an abnormal cycle so that any indoor The machine cannot perform normal cooling.

The purpose of the present invention is to solve the above-mentioned defects, one of which is to provide a low temperature control method for a composite air conditioner, which only uses the temperature of the indoor heat exchanger in operation regardless of the number and cooling capacity of the indoor units in operation The average temperature of the bypass valve, electronically controlled expansion valve, outdoor blower and compressor are controlled in sequence to prevent the heat exchanger from freezing, so as to achieve the best refrigeration cycle.

The present invention is dedicated to solving the above-mentioned defects, and another object is to provide a composite air conditioner low-temperature control method. When multiple rooms with different loads are simultaneously refrigerated, by controlling the opening degree of the electronically controlled expansion valve of the corresponding indoor unit, Prevent the corresponding indoor unit from freezing while ensuring the normal operation of indoor units in other rooms.

In order to achieve the above purpose, the low temperature control method of a composite air conditioner that is provided by the present invention in which one outdoor unit is connected to one or more indoor units and can cool multiple rooms includes the following steps:

Normal operation procedure: open the electronically controlled expansion valve of the indoor unit in operation to a certain opening degree to adapt to the number of indoor units in operation, so as to control the flow of refrigerant flowing into the indoor unit in operation;

Low-temperature control program: During the operation to prevent each indoor heat exchanger from freezing at low temperature, the bypass valve, electronically controlled expansion valve, outdoor blower and compressor are controlled in sequence according to the temperature change of the indoor heat exchanger in operation.

Fig. 1 is the refrigerant cycle flow diagram of a traditional composite air conditioner with three indoor units;

Figure 2 is a diagram of the open state of the solenoid valve according to the number of indoor units in operation in a traditional composite air conditioner with three indoor units;

Fig. 3 is the figure that traditionally carries out low temperature control according to the temperature of its heat exchanger;

Fig. 4 is the refrigerant cycle flow diagram of the composite air conditioner with three indoor units of the present invention;

Fig. 5 is the circuit block diagram of the composite air conditioner low temperature control device of the present invention;

Fig. 6 is the state diagram of each controlled component that the present invention carries out low temperature control according to the temperature of its heat exchanger;

Fig. 7 is a diagram showing the steps of low temperature control according to the speed of the outdoor blower of the present invention;

Fig. 8 is a load state diagram when the present invention returns to normal operation from the low temperature control step when a room is refrigerated;

Fig. 9 is a load state diagram when the present invention returns to normal operation from the low temperature control step when two rooms are refrigerated;

Figures 10a and 10b are flow charts of the low temperature control method when a room is refrigerated according to Embodiment 1 of the present invention;

Figures 11a and 11b are flow charts of the low temperature control method in the second embodiment of the present invention when two rooms are refrigerated.

The present invention will be described in detail below in conjunction with the embodiments and with reference to the accompanying drawings.

Fig. 4 is a refrigerant cycle flow chart of the composite air conditioner with three indoor units of the present invention, wherein the same components as the traditional composite air conditioner have adopted the same reference numerals.

Referring to Fig. 4, the composite air conditioner has three indoor units 10, 11, 12 and an outdoor unit 20, and the outdoor unit 20 is provided with a compressor 30, an outdoor heat exchanger 40, and an outdoor blower 41 for bypassing a certain amount of air. The first bypass valve 110 and the first capillary tube 111 for the refrigerant discharged from the compressor 30, the second bypass valve 120 and the second bypass valve 120 for bypassing a certain amount of refrigerant discharged from the outdoor heat exchanger 40 Two capillary tubes 121, electronically controlled expansion valves 130, 131, and 132 for rooms A, B, and C. These expansion valves are used to selectively open or close according to the operating status (on/off) of each indoor unit to complete each room. Refrigeration.

In addition, the indoor units 10, 11, 12 respectively include indoor heat exchangers 90, 91, 92, indoor blowers 100, 101, 102, and temperature sensors 140, 141 for detecting and outputting the temperature of the indoor heat exchangers 90, 91, 92. , 142.

The low temperature control method of the composite air conditioner of the present invention can be referred to FIG. 5 .

As shown in FIG. 5 , the power supply device 150 converts the AC voltage input from the AC power input terminal (not marked) into a certain DC voltage, and then outputs it to the control device 154 . The operation control device 152 is composed of a group of function keys for inputting operation modes (automatic, cooling, defrosting, blowing, etc.), adjusting air volume, adjusting set (TS) temperature, air conditioner operating status (on/off) and the like.

In order to realize the operation of the indoor units can be controlled respectively according to the average temperature of the indoor heat exchangers 90, 91, 92 in operation regardless of the number and cooling capacity of the indoor units in operation, so as to complete the optimal cooling of each indoor unit In a cycle, the control device 154 sequentially executes the first step to the fourth step. That is: open or close the first and second bypass valves 110, 120; change the electronically controlled expansion valves 130, 131, 132 of chambers A, B, and C to the optimum opening degree obtained through testing; change the speed of the outdoor blower 41 ; Turn compressor 30 on or off.

The room temperature detection device 156 is made up of temperature sensors such as detecting the indoor temperature (Tr) and the outdoor temperature (T0) of the indoor units 10, 11, 12 and outputting the temperature of the indoor heat exchangers 90, 91, 92. The compressor driving device 158 controls and drives the compressor 30 according to the comparison result of the set temperature (TS) and the room temperature (Tr).

The outdoor blower driving device controls the outdoor blower 61 to be turned on or off according to the comparison result of the set temperature (TS) and the room temperature (Tr). The indoor blower driving device 162 controls the speed of the indoor blower motor according to the set air volume and turns on or off the indoor blowers 100, 101, 102, so that the air exchanged by the indoor heat exchangers 90, 91, 92 is blown into the room .

Moreover, in order to open or close the valve according to the number of indoor units 10, 11, 12 in operation to control the flow of refrigerant, the refrigerant valve driving device 164 receives the control signal output by the control device 154, opens or closes the first 1. The second bypass valves 110, 120 either open or close the electronically controlled expansion valves 130, 131, 132, so that they are located at a set opening degree.

The operation process of the composite air conditioner low temperature control method of the present invention will be introduced in detail below.

First of all, the low temperature control method of the composite air conditioner in the cooling of one room according to the present invention can be referred to in Fig. 10a and Fig. 10b.

10a and 10b are flow charts of the low temperature control method when cooling one room per room according to the embodiment of the present invention.

When the air conditioner is powered on, the power supply device 150 converts the AC voltage input from the AC input terminal (not marked) into a constant DC voltage, and outputs it to the driving circuits and the control device 154 .

The control device 154 uses the DC voltage output by the power supply device 150 to start the air conditioner.

At the same time, the user sets the number of cooling rooms, the set temperature (TS), the set air volume, the operation selection signal and the operation start signal (hereinafter referred to as the operation signal) by operating the function keys on the control device 152, and through the operation control device 152 Input to the control device 154.

In step S1, the control device 154 judges whether a room is cooling. If it is determined that a room is cooling (that is, yes), then step S2 is performed, and the control device 154 outputs a control signal to the indoor blower motor drive device 162 and the valve drive device 164 to drive the indoor unit (room) in operation. A, B or C) indoor blowers 100, 101, 102 and electronically controlled expansion valves 130, 131, 132.

Therefore, the indoor blower motor driving device 162 controls the motor speed of the indoor blower according to the set air volume and starts the indoor blower 100 , 101 , 102 in one of the rooms A, B, and C. The valve driver 164 opens the electronically controlled expansion valve 130, 131, 132 of one of the chambers A, B, and C to a certain degree of opening (level 250: the optimum degree of opening determined through experiments), so as to meet the cooling needs of a room.

Then step S3 is executed, the control device 154 judges whether the room temperature (Tr) measured by the room temperature detection device 156 is higher than the set temperature (TS).

According to the determination result of step S3, if the room temperature Tr is higher than the set temperature TS (that is, yes), the next step S4 is executed, and the control device 154 outputs a control signal to the compressor driving device 158 to start the compressor 30 . Simultaneously, a control signal is output to the outdoor blower electric drive device 160 to drive the outdoor blower 41, and according to the outdoor temperature (when the outdoor temperature exceeds 28 degrees Celsius, its rotating speed is set to a high rotating speed, and when the outdoor temperature is 26 degrees Celsius, its rotating speed is set to is low speed) to control its speed.

The compressor drive 158 thus activates the compressor 30 via the control signal output by the control device 154 . The outdoor blower motor driving device 160 sets the outdoor blower 41 to a high or low rotational speed (rev/min) through the control signal output by the control device 154 .

When the compressor 30 and the outdoor blower 41 are turned on, the high temperature and high pressure vapor refrigerant is discharged from the compressor of the outdoor unit 20 and injected into the outdoor heat exchanger 40 in step S5. The outdoor heat exchanger 40 utilizes the air blown by the outdoor blower to exchange heat and condense the high-temperature and high-pressure vapor-state refrigeration, thereby enhancing the effect of cooling and condensation.

The room temperature, high pressure, and liquid refrigerant condensed and liquefied at the outdoor heat exchanger 40 is introduced into one of the electronically controlled expansion valves 130, 131, and 132 of the chambers A, B, and C that are opened at a certain opening degree. Level 250 (other electronically controlled expansion valves remain closed) to reduce the pressure to obtain low-temperature and low-pressure refrigerants that are easy to evaporate, and then flow into the chambers A, B, and C installed in the indoor units 10, 11, and 12 One of the heat exchangers 90,91,92.

When the low-temperature, low-pressure and easy-to-vaporize refrigerant that has been depressurized by one of the electronically controlled expansion valves 130, 131, and 132 is vaporized at the indoor heat exchangers 90, 91, and 92 of the corresponding chambers A, B, and C transformed into gas. At the same time, heat exchange is performed with the indoor air, and indoor air blowers 100, 101, 102 are used to blow air, thereby cooling the indoor air. Then this cooled air (cold air) is discharged into the room, thereby completing the cooling process of a room. The vapor refrigerant cooled in the indoor heat exchangers 90, 91, 92 of the chambers A, B, and C is reintroduced into the compressor 30 and may be recirculated.

As described above, during cooling, the room temperature detection device 156 detects the temperature TP of the indoor heat exchanger of the indoor unit in operation in step S6. At the same time, the control device 154 judges whether the temperature TP of the indoor heat exchanger of the operating indoor unit is lower than 4 degrees Celsius.

According to the determination result of step S6, if the output temperature TP of the indoor heat exchanger of the operating indoor unit is not lower than 4 degrees Celsius (ie, no), return to the previous step S5 and continue the cooling operation of one room.

On the other hand, if the output temperature TP of the indoor heat exchanger of the indoor unit in operation is lower than 4 degrees Celsius (that is, yes), then execute the next step S7, as shown in Figure 6, the heat exchange rate determined by the control device 154 Whether the time the device maintains below 4 degrees Celsius exceeds a predetermined time value (t1) (for example, t1 is 5 seconds).

According to the determination result of step S7, if the predetermined time value t1 has passed, then step S8 is executed, and the control device 154 outputs a control signal to the valve driving device 164 to open the second bypass valve 120 .

6 and 7, the valve driving device 164 opens the second bypass valve 120 according to the control signal of the control device 154, and bypasses the refrigerant discharged from the outdoor heat exchanger 40 according to a predetermined amount, thereby completing the first step of the low temperature control program. step.

After the first step of the low temperature control program is completed, as shown in FIG. 6 , step S9 is executed, and the control device 154 determines whether the temperature TP of the indoor heat exchanger is lower than 2 degrees Celsius. If it is not lower than 2 degrees Celsius (ie, no), repeat step S9.

According to the determination result of step S9, if the temperature TP of the indoor heat exchanger is lower than 2 degrees Celsius (that is, yes), then step S10 is executed, and the control device 154 judges whether the indoor heat exchanger remains lower than 2 degrees Celsius for more than a period of time. Given time value t1.

According to the determination result of step S10, if a predetermined time value has been exceeded (that is, yes), the next step S11 is executed, and the control device 154 outputs a control signal to the valve driving device 164 to drive the first bypass valve 120 .

Therefore, when the valve driving device 164 opens the first bypass valve 110 according to the output control signal of the control device 154 , the refrigerant discharged from the compressor 30 is bypassed according to a predetermined amount, thereby completing the second step of the low temperature control procedure.

As shown in Figure 6 and Figure 10a, after completing the first and second steps of the low temperature control program, step S12 is then executed, and the control device 154 judges whether the temperature TP of the indoor heat exchanger in one of the chambers A, B, and C is higher than 10 degrees Celsius.

According to the determination result of step S12, if the temperature TP of the indoor heat exchanger is higher than 10 degrees centigrade (that is, yes), then the next step S13 is executed, and the control device 154 confirms that it is set by the first and second steps of the low temperature control program. The fixed condition has been eliminated, and the valve actuator 164 closes the second bypass valve 120.

Then step S14 is executed to determine whether the temperature TP of the indoor heat exchanger is higher than 12 degrees Celsius.

As shown in Figure 6, according to the determination result of step S14, if the temperature TP of the indoor heat exchanger is higher than 12 degrees centigrade (that is, yes), then the next step S15 is executed, and the control device 154 confirms that the second step by the low temperature control program The condition set by the step is removed and the valve actuator 164 closes the first bypass valve. Then, return to step S6, and repeat its subsequent steps.

As shown in FIG. 6 , according to the determination result of step S14 , if the temperature TP of the indoor heat exchanger is higher than 12 degrees Celsius (ie, no), the next step S16 is executed. The control device 154 judges whether the temperature TP of the indoor heat exchanger in operation is lower than 0 degrees Celsius after the second step of the low temperature control program is executed.

According to the determination result of step S16, if the temperature TP of the heat exchanger in the running machine room is lower than 0 degrees Celsius (that is, yes), the next step S17 is executed. The control device 154 outputs a control signal to the outdoor blower driving device 160 to reduce the speed of the outdoor blower 41 .

Therefore, as shown in Figures 6 and 7, the outdoor blower driving device 160 reduces the speed of the outdoor blower 41 according to the control signal sent by the control device 154 (high to low, low to off), thereby completing the third step of the low temperature control program .

After the third step of the low temperature control program is completed, as shown in FIG. 6 , step S18 is executed. After changing the rotational speed of the outdoor blower 41, in step S18, the control device 154 judges whether the temperature TP of the indoor heat exchanger (a room) in operation has risen to 4 degrees Celsius (when the outdoor temperature is not higher than 26 degrees Celsius) or 8 degrees Celsius (When the outdoor temperature is higher than 28 degrees Celsius).

According to the determination result of step S18, if the temperature TP of the indoor heat exchanger is higher than 4 or 8 degrees Celsius (that is, yes), then perform step S19, as shown in Figure 6, the control device 154 outputs a control signal to the outdoor blower drive device 160. Make the outdoor blower 41 return to the initial rotation speed (low to high, off to low). Then, return to step S16.

On the other hand, as shown in FIG. 6, according to the determination result of step S18, if the temperature TP of the indoor heat exchanger is not higher than 4 or 8 degrees Celsius (ie, no), the next step S20 is executed. The control device 154 then executes the third step of the low temperature control procedure, and determines whether the temperature TP of the indoor heat exchanger is lower than -3 degrees Celsius. If the temperature of the indoor heat exchanger is not lower than -3 degrees Celsius (ie, no), repeat step S20.

As shown in FIG. 6, according to the determination result of step S20, if the temperature TP of the indoor heat exchanger is lower than -3 degrees Celsius (ie yes), then the next step S21 is executed. The control device 154 determines whether the time for which the temperature of the indoor heat exchanger is maintained at -3 degrees Celsius exceeds a predetermined time value t1.

As shown in Figures 6 and 7, according to the determination result of step S21, if the predetermined time value t1 has been exceeded (i.e. yes), then step S22 is executed, as shown in Figure 8, the control device 154 closes the compressor 30 and the outdoor blower 41, and switch the rotation speed of the indoor blower of the indoor unit in operation (set to low low rotation speed (LL)).

When the compressor 30 is in the shutdown state, the 3-minute delay and 2.5-minute pressure balance control procedures are simultaneously completed. One of the electronically controlled expansion valves 130, 131, 132 of the operating indoor unit (one room) moves to level 180, and maintains its standby state. The electronically controlled expansion valves of other indoor units that are not operating remain in their closed state. These operating procedures are completed in the fourth step of the low temperature control procedure.

Therefore, regardless of the number of operating indoor units or the cooling capacity, the low temperature control program sequentially completes the first to fourth steps in order to detect the temperature of the indoor heat exchanger of the operating indoor units (one room). Thus, when the operating indoor unit has a high load during its own operation, the bypass valve is closed, thereby ensuring the maximum cooling capacity of the operating indoor unit.

Then step S23 is executed, and the control device 154 judges whether the compressor 30 has been kept in the standby state for more than 3 minutes, that is, whether it has been delayed for 3 minutes. If it has been more than 3 minutes (that is, yes), then step S24 is executed, and the control device 154 determines whether the temperature TP of the indoor heat exchanger is higher than 6 degrees Celsius.

According to the determination result of step S24, if the temperature TP of the indoor heat exchanger is higher than 6 degrees Celsius. (Yes), then execute the next step S25, the control device 154 judges whether the room temperature TR is higher than the set temperature TS.

According to the determination result of step S25, if the room temperature TR is higher than the set temperature TS (that is, yes), the control device 154 ends the low temperature control program, and keeps the indoor unit in its normal operating state. Then, the next step S26 is executed, the control device 154 sets the compressor 30 to an open state, the outdoor air blower is in the initial state (i.e. high or low speed running state) before the low temperature control program, and the first and second bypass valves 110, 120 is in the closed state, and the running indoor unit (one room) runs at its set rotation speed. One of the electronically controlled expansion valves 130, 131, 132 corresponding to the operating indoor unit (one room) moves to level 250 and completes its normal operation. Then return to step S5, and repeat its subsequent steps.

Referring to accompanying drawings 11a and 11b, the following describes in detail the low temperature control method of the present invention when cooling multiple rooms (two or three rooms).

11a and 11b are flow charts of the low temperature control method in the second embodiment of the present invention when two rooms are refrigerated.

First, step S31 is executed, and the control device 154 judges whether to perform the cooling operation of the two rooms. If two rooms are being refrigerated (i.e. yes), then the next step S32 is executed, and the control device 154 opens the indoor units of the two rooms in the rooms A, B, and C and the two of the electronically controlled expansion valves 130, 131, and 132. Each valve should be opened to a certain degree to meet the cooling demand of the second room.

Then step S33 is executed, the control device 154 judges whether the room temperature TR is higher than the set temperature TS, if the room temperature TR is not higher than the set temperature TS (ie, no), repeat step S33. If the room temperature TR is higher than the set temperature TS (that is, yes), the next step S34 is performed.

In step S34, the control device 154 starts the compressor 30, and switches the outdoor blower to high speed (when the outdoor temperature is higher than 28 degrees Celsius) or to low speed (when the outdoor temperature is not lower than 26 degrees Celsius).

After the compressor 30 and the outdoor blower are started, step S35 is then performed to cool the two rooms. The high-temperature and high-pressure gaseous refrigerant is discharged from the compressor 30 and injected into the outdoor heat exchanger 40, and then condensed to obtain a liquid room temperature and high-pressure refrigerant.

The liquid room temperature and high pressure refrigerant condensed at the outdoor heater 40 flows into two corresponding electronically controlled expansion valves with a certain degree of opening in chambers A, B, and C, and depressurizes them, and then, the obtained low temperature , low-pressure refrigerant is injected into two of the indoor heat exchangers 90, 91, 92 of the chambers A, B, and C.

Therefore, this low-temperature and low-pressure refrigerant is vaporized in the indoor heat exchangers of the respective chambers A, B, and C. At the same time, the outside air is cooled. This cooled air is discharged into the room, thereby completing the cooling of the two rooms (room A+B, room B+C, room A+C). Then, the low-temperature and low-pressure refrigerant undergoes heat exchange at the corresponding indoor heat exchangers 90, 91, 92, and then is sent to the compressor for recirculation.

When the cooling work of the two rooms is performed, step S36 is executed, the temperature detection device 156 detects the output temperature TP of the indoor heat exchanger in operation, and the control device 154 judges whether the average temperature TPM of the two indoor heat exchangers in operation is lower than 4 degrees Celsius.

According to the determination result of step 36, if whether the average temperature TPM of the indoor heat exchanger is lower than 4 degrees Celsius (that is, no), return to step S35; if the average temperature TPM of the indoor heat exchanger is lower than 4 degrees Celsius (that is, Yes ), then execute the next step S37. The control device 154 judges whether the average temperature of the indoor heat exchanger remains below 4 degrees Celsius for more than a predetermined time value T1 (for example, T1 is 5 seconds).

According to the determination result of step S37, if the predetermined time value T1 is not exceeded (i.e., no), then repeat step S36, if the average temperature of the indoor heat exchanger remains lower than 4 degrees Celsius for more than the predetermined time value T1 (for example, When T1 is 5 seconds), then execute the next step S38. The control device 154 opens the second bypass valve to bypass a certain amount of refrigerant discharged from the outdoor heat exchanger 40 . This completes the first step of the low temperature control program.

Next, step S39 is executed, as shown in FIG. 6, the control device 154 judges whether the average temperature TPM of the indoor heat exchanger is lower than 2 degrees Celsius, if the average temperature TPM of the indoor heat exchanger is not lower than 2 degrees Celsius (that is, when no) , then repeat step S39; if the average temperature TPM of the indoor heat exchanger is lower than 2 degrees Celsius (that is, yes), then execute the next step S40. The control device 154 judges whether the average temperature TPM of the indoor heat exchanger remains lower than 2 degrees Celsius for longer than a predetermined time value T1.

According to the determination result of step S40, if the time maintained below 2 degrees Celsius does not exceed the predetermined time value T1 (i.e., no), then repeat step S40; if it has exceeded the predetermined time value T1 (i.e., yes), then execute the following A step S41. The control device 154 opens the first bypass valve to bypass a certain amount of refrigerant discharged from the compressor 30 . Thus completing the second step of the low temperature control program.

As shown in FIG. 6 , after the first and second steps of the low temperature control program are executed, step S42 is executed. The control device 154 judges whether the average temperature TPM of the indoor heat exchanger is higher than 10 degrees Celsius.

According to the determination result of step S42, as shown in FIG. 6, if the average temperature TPM of the indoor heat exchanger is higher than 10 degrees Celsius (that is, yes), the next step S43 is executed. The control device 154 confirms that the state of the first step of the low temperature control program is eliminated, and closes the second bypass valve 120 .

Then, the next step S44 is executed. As shown in FIG. 6 , the control device 154 maintains the closed state of the second bypass valve, and determines whether the TPM is higher than 12 degrees Celsius.

According to the determination result of step S44, as shown in FIG. 6, if the TPM is higher than 12 degrees Celsius (ie yes), the next step S45 is executed. The control device 154 confirms that the state of the second step of the low temperature control program has been eliminated, and closes the first bypass valve 120 . Then return to step S36, and repeat its subsequent steps.

According to the determination result of step S44, if TPM is not higher than 12 degrees Celsius (being no), then execute step S46, and control device 154 judges whether the TPM after completing the temperature control program is lower than 0 degrees Celsius, if not lower than 0 Celsius (ie no), repeat step S46.

According to the determination result of step S46, if the TPM is lower than 0 degrees (ie yes), then execute the next step S47. The control device 154 switches the rotation speed of the outdoor blower 41 (high to low, low to off), thereby completing the third step of the low temperature control procedure.

After the third step of the low-temperature control program is executed, that is, after the outdoor blower 41 switches its rotational speed, step S48 is executed. As shown in FIG. 6 , the control device 154 determines whether the TPM is higher than 4 degrees Celsius (when the outdoor temperature is lower than 26 degrees Celsius) or 8 degrees Celsius (when the outdoor temperature exceeds 28 degrees Celsius).

According to the determination result of step S48, if the TPM is higher than 4 or 8 degrees Celsius (that is, yes), the next step S49 is executed, and the control device 154 places the outdoor blower 41 at the initial speed before the third step of the low temperature control program ( low to high, off to low). Then return to step S46, and repeat its subsequent steps.

On the other hand, according to the determination result of step S48, if the TPM is not higher than 4 or 8 degrees Celsius (i.e. when no), then execute the next step S50, as shown in Figure 6, the control device 154 judges that the third step of the low temperature control program is completed. Whether the temperature TPA of the indoor heat exchanger after the step (for example, the indoor heat exchanger of room A) is lower than -3 degrees Celsius.

According to the determination result of step S50, if the temperature TPA of the indoor heat exchanger in room A is lower than -3 degrees Celsius (ie yes), then step S51 is executed. The control device 154 judges whether the time for which the temperature TPA of the indoor heat exchanger of the room A remains lower than -3 degrees Celsius exceeds a predetermined time value T1.

According to the determination result of step S51, if exceed preset time value T1 (being yes), then execute next step S52. The control device 154 moves the electronically controlled expansion valve of the indoor unit of room A to level 180, and switches the indoor blower 100 from the set speed to low low speed (LL).

Therefore, regardless of the number of indoor units in operation or their cooling capacity, what is detected is the average temperature (TPM) of the indoor heat exchanger (two rooms), thereby completing the first to third steps of the low temperature control procedure. When the loads of the indoor units are different, the electronically controlled expansion valve 130 of the indoor unit satisfies the condition of the fourth step of the low temperature control program, and its opening degree is controlled (level 180), thereby preventing the indoor unit from freezing. At the same time, an optimal circulation of refrigeration is formed.

Then step S53 is executed, and the control device 154 judges whether the temperature TPB of the indoor exchanger of room B (for example: room B) is lower than -3 degrees Celsius after completing the fourth step of the temperature control program of room A.

According to the determination result of step S53, if the temperature TPB of the indoor heat exchanger of room B is lower than -3 degrees Celsius (that is, yes), the next step S54 is executed. As shown in FIG. 6 , the control device 154 judges whether the time for which the temperature TPB of the indoor heat exchanger of the room B is maintained below -3 degrees Celsius exceeds a predetermined time value T1 .

According to the determination result of step S54, if the predetermined time value T1 has been exceeded (ie yes), then the next step S55 is executed. The control device 154 makes the temperatures TPA and TPB of the indoor heat exchangers in the chambers A and B meet the conditions of the fourth step of the low temperature control program. As shown in Figures 6 and 7, the control device 154 turns off the compressor 30 and the outdoor blower 41, and at the same time, turns the speed of the indoor blower 101 of the room B from the set speed to a low-low speed (LL) (at this time, the room The speed of the indoor blower of A has been low-low speed (LL)

When the compressor 30 is in the shutdown state, a three-minute delay and two and a half minutes pressure balance control procedures are performed. The electronically controlled expansion valve 131 of chamber B moves to stage 180 and remains in its standby state (at this time, the electronically controlled expansion valve 130 of chamber A is already at stage 180). And the corresponding electronically controlled expansion valve of the indoor unit in the shutdown state keeps its closed state. Finally, complete the fourth step of the cryogenic control program.

Next, step S56 is executed, and the control device 154 judges whether the compressor 30 has been delayed for 3 minutes. If the compressor 30 has been delayed for three minutes (that is, yes), the next step S57 is executed, and the control device 154 judges whether the temperature TPA of the indoor exchanger of the room A is higher than 6 degrees Celsius.

According to the determination result of step S57, if the temperature TPA of the indoor heat exchanger of room A is higher than 6 degrees Celsius (that is, yes), the next step S58 is executed. The control device S154 cancels the low-temperature control program of room A, and the indoor unit returns to its normal cooling operation state. Then, the control device 154 starts the compressor 30, the outdoor blower returns to its initial state (high or low speed) before executing the low temperature control program, the first and second bypass valves are closed, and the speed of the indoor blower in chamber A is the set speed . The electronically controlled expansion valve 130 of chamber A moves to level 250, returns to step S35, and repeats its subsequent steps.

On the other hand, according to the determination result of step S57, if the temperature TPA of the heat exchanger in chamber A is not higher than 6 degrees Celsius (ie, no), the next step S59 is executed. The control device 154 judges whether the temperature TPB of the indoor heat exchanger of the room B is higher than 6 degrees Celsius. If the temperature TPB of the indoor heat exchanger in room B is not higher than 6 degrees Celsius (ie no), return to step S57 and repeat the subsequent steps.

According to the determination result of step S59, if the temperature TPB of the indoor heat exchanger of room B is higher than 6 degrees Celsius (that is, yes), the next step S60 is executed. As shown in FIGS. 6 to 9, the control device 154 cancels the condition of the low temperature control program of chamber B and sets the indoor heat exchanger of chamber B to its normal cooling operation state. That is, start the compressor, the speed of the outdoor blower 41 returns to the high or low speed before the low temperature control program is executed, the first and second bypass valves 101 and 102 are closed, the indoor blower in room B blows air at the set speed, and the room B blows air at the set speed. The corresponding electronically controlled expansion valve 131 is moved to stage 250. Finally, step S35 is executed and its subsequent steps are repeatedly executed.

In addition, when the temperatures TPA and TPB of the indoor heat exchangers in rooms A and B are both higher than 6 degrees Celsius, the electronically controlled expansion valves 130 and 131 corresponding to rooms A and B are moved to level 210, and the two rooms are simultaneously refrigerated.

According to the above, the composite air conditioner low temperature control method of the present invention has the following advantages: regardless of the number or cooling capacity of the indoor units in operation, in the first to first four steps of the low temperature control program, the detected The average temperature of the indoor heat exchanger of the indoor unit during operation is used to control the bypass valve, electronically controlled expansion valve, outdoor blower and compressor in sequence, so as to prevent the indoor unit from freezing and form the best cycle refrigeration; When the load of the indoor unit is large, close the bypass valve to achieve the maximum cooling capacity of multiple rooms; The electronically controlled expansion valve is controlled to a certain opening degree (level 180), thereby preventing the indoor fan from freezing, and at the same time, allowing other indoor heat exchangers that are operating normally to perform normal refrigeration procedures.

Claims (8)

1. Off-premises station can connect one or more indoor set, the low temperature control method of composite air conditioner that a plurality of rooms are freezed, it is waited to levy and is: may further comprise the steps: a common operation sequence: with the electric control expansion valve of ongoing indoor set open to a predetermined opening degree adapting to the quantity of operating indoor set, thereby by operation indoor set control refrigerant flow; Low temperature control program: in the operating process of when it prevents every indoor heat converter low temperature, freezing, according to the variations in temperature of operating indoor heat converter, control by-passing valve according to the order of sequence, electric control expansion valve, outdoor blowers and compressor.
2. 2. the low temperature control method of composite air conditioner according to claim 1, it is characterized in that: in the low temperature control program, comprise that also an operation returns step, when the temperature of indoor heat converter is higher than default low temperature and returns temperature, carry out normal refrigerating operaton, make by-passing valve, electric control expansion valve, outdoor blowers and compressor are back to normal refrigerating operaton state.
3. 3. the low temperature control method of composite air conditioner according to claim 1 and 2 is characterized in that: when a plurality of rooms refrigeration, the temperature of each operating indoor heat converter is controlled to be the mean temperature of indoor heat converter.
4. 4. the low temperature control method of composite air conditioner according to claim 1 and 2 is characterized in that: the rotary speed of outdoor blowers (rev/min) determine by outdoor temperature.
5. An off-premises station can connect one or more indoor set, the low temperature control method of composite air conditioner that a plurality of rooms are freezed, it is waited to levy and is: may further comprise the steps; By opening the predetermined opening degree of electric control expansion valve to adapting to the quantity of operating indoor set, thereby the refrigerant flow of operating indoor set is flow through in control;

   The first step of low temperature control program: when the time that an indoor heat converter remains below first design temperature surpasses a given time value, open second by-passing valve;

   Second step of low temperature control program: after executing first step, when the time that this indoor heat converter remains below second design temperature surpasses a given time value, open first by-passing valve;

   The third step of low temperature control program: after executing second step, when indoor heat converter keeps below the 3rd design temperature, the rotating speed of change outdoor blowers (rev/min);

   The 4th step of low temperature control program: after executing third step, when the time that indoor heat converter remains below the 4th design temperature surpasses a given time value, close compressor.
6. Off-premises station can connect one or more indoor set, the low temperature control method of composite air conditioner that a plurality of rooms are freezed, it is waited to levy and is: may further comprise the steps; By opening the predetermined opening degree of electric control expansion valve to adapting to the quantity of indoor set in service, thereby the refrigerant flow of operating indoor set is flow through in control;

   The first step of low temperature control program: when the time that the mean temperature of a plurality of indoor heat converters remains below its first design temperature surpasses a given time value, open second by-passing valve;

   Second step of low temperature control program: after executing first step, when the time that the mean temperature of indoor heat converter remains below second design temperature surpasses a given time value, open first by-passing valve;

   The third step of low temperature control program: after executing second step, when the time that the mean temperature of indoor heat converter remains below the 3rd design temperature surpasses a given time value, change outdoor blowers rotating speed (rev/min);

   The 4th step of low temperature control program: after executing third step, when the time that the temperature of any one indoor heat converter remains below the 4th design temperature surpasses a given time value, change the opening degree of the electric control expansion valve of respective chambers machine.
7. 7. the low temperature control method of composite air conditioner according to claim 6, it is characterized in that: in the 4th step of low temperature control program, when the time that the temperature of each indoor heat converter remains below the 4th design temperature surpasses a given time value, close compressor.
8. 8. the low temperature control method of composite air conditioner according to claim 7, it is characterized in that: in the 4th step of low temperature control program, compressor is in closed condition, close outdoor blowers, change the opening degree of the electric control expansion valve of all operating indoor sets simultaneously, to adapt to the low temperature control program.

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