JP6557855B2 - Refrigeration cycle equipment - Google Patents

Description

  The present invention relates to control of a refrigeration cycle apparatus such as an air conditioner.

  In the conventional air conditioner, if the discharge temperature of the compressor is below the limit value, the opening degree of the throttle device is controlled so that the suction superheat degree of the compressor becomes a predetermined temperature, and the discharge temperature of the compressor is the limit value. When the pressure exceeds the value, the opening degree of the expansion device is controlled so that the discharge temperature of the compressor becomes a predetermined value (for example, Patent Document 1).

JP 2001-174075 A

  When a refrigerant with a high discharge temperature is used, if the suction superheat degree is set as a control target as in the past, the throttling device suddenly moved in the closing direction in order to quickly draw out the capacity, and an appropriate superheat degree was obtained. In some cases, the throttle device may be over-closed (over-throttle state). In an over-throttle state, the discharge temperature may rise rapidly, exceeding the limit value at which the compressor can operate normally and falling into a protective operation.

  If the discharge temperature exceeds the limit value, it will lead to damage to the compressor motor and deterioration of the refrigeration oil, so that the throttle device operates in the opening direction rapidly in an attempt to lower the discharge temperature. If the discharge temperature still does not decrease, the frequency of the compressor is suppressed, causing a rapid decrease in the discharge temperature and causing a decrease in comfort.

  In addition, if the throttle device is operated too slowly in order to avoid a sudden rise in the discharge temperature of the compressor, it takes a considerable amount of time to obtain a sufficient degree of superheat. In this case, not only is the capacity inadequate, the comfort is impaired, but the liquid refrigerant easily returns to the compressor, and the liquid compression may cause damage to the internal mechanical parts of the compressor. It was.

  In addition, when a refrigerant with a higher discharge temperature is used, operating under high load conditions may cause a situation where it is difficult to operate below the discharge temperature limit value while maintaining an appropriate degree of superheat. It was necessary to study a proper control method.

  In order to solve the above-described conventional problem, the present invention provides a suction superheat degree calculated by the suction superheat degree calculation unit when the discharge temperature detected by the discharge temperature detection unit is smaller than a predetermined discharge temperature determination value. When the flow rate of the refrigerant passing through the throttle device is adjusted so as to be a predetermined suction superheat degree setting value, and the discharge temperature is larger than a predetermined discharge temperature determination value, changes in the suction superheat degree and the discharge temperature The flow rate of the refrigerant passing through the expansion device is adjusted according to the amount.

  In the present invention, when the discharge temperature detected by the discharge temperature detection unit is larger than a predetermined discharge temperature determination value, the refrigerant flow rate passing through the throttle device is adjusted so that the discharge temperature becomes a discharge temperature set value. The discharge temperature setting value is adjusted based on the discharge temperature when the predetermined discharge temperature is exceeded, the suction superheat degree is larger than the suction superheat degree set value, and the discharge temperature is the discharge temperature. When it is smaller than the set value, the discharge temperature set value is lowered.

  In this way, by controlling suction superheat degree control and discharge temperature control in combination, it is possible to quickly extract a predetermined capacity and avoid sudden changes in discharge temperature, thereby improving the comfort and reliability of the device. Can be realized.

  According to the present invention, rapid increase or decrease in discharge temperature due to excessive operation of the throttle device can be suppressed, and deterioration of the reliability of the equipment such as deterioration of the refrigerating machine oil or burning of the compressor motor can be avoided, and the equipment is comfortable and highly reliable. Can be supplied. Furthermore, it is possible to supply a comfortable, stable and reliable device even under high load conditions.

Refrigeration cycle diagram in Embodiment 1 of the present invention Control block diagram according to Embodiment 1 of the present invention Flowchart in Embodiment 1 of the present invention Flowchart in Embodiment 2 of the present invention Flowchart in Embodiment 3 of the present invention

  The first invention includes a compressor, a condenser, a throttle device, an evaporator, a discharge temperature detection unit that detects the temperature of the refrigerant discharged from the compressor, and the degree of superheat of the refrigerant sucked into the compressor. A suction superheat degree calculation unit for calculating, when the discharge temperature detected by the discharge temperature detection unit is smaller than a predetermined discharge temperature determination value, the suction superheat degree calculated by the suction superheat degree calculation unit is a predetermined value If the flow rate of the refrigerant passing through the throttle device is adjusted so that the suction superheat degree setting value is obtained, and the discharge temperature is larger than a predetermined discharge temperature determination value, the amount of change in the suction superheat degree and the discharge temperature is set. Accordingly, the flow rate of the refrigerant passing through the expansion device is adjusted.

  According to this, since the suction superheat degree can be maintained at an optimal value while controlling the discharge temperature, the comfort and efficiency are lowered due to a sudden change in the throttle amount of the throttle device, and the discharge temperature is excessively increased. It is possible to avoid deterioration of equipment reliability such as deterioration of refrigeration oil and compressor motor, and supply of comfortable and reliable equipment can be achieved.

  According to a second aspect of the present invention, there is provided a compressor, a condenser, a throttling device, an evaporator, a discharge temperature detection unit that detects a temperature of refrigerant discharged from the compressor, and a degree of superheat of the refrigerant sucked into the compressor. A suction superheat degree calculation unit for calculating, and when the discharge temperature detected by the discharge temperature detection unit is larger than a predetermined discharge temperature determination value, the throttle device so that the discharge temperature becomes a discharge temperature set value The discharge temperature setting value is based on the discharge temperature when the predetermined discharge temperature is exceeded, and the suction superheat degree is larger than the suction superheat degree set value, When the discharge temperature is lower than the discharge temperature set value, the discharge temperature set value is lowered.

  According to this, by changing the discharge temperature setting value according to the suction superheat degree and the discharge temperature, the difference between the discharge temperature and the discharge temperature setting value can always be reduced, so that the amount of change in the aperture of the expansion device can be reduced, Rapid fluctuations in discharge temperature can be suppressed.

  According to a third invention, in the second invention, when the suction superheat degree is smaller than the suction superheat degree set value and the discharge temperature is larger than the discharge temperature set value, the discharge temperature set value is increased. is there.

(Embodiment 1)
1 is a refrigeration cycle diagram of the air-conditioning apparatus according to Embodiment 1 of the present invention, FIG. 2 is a control block diagram, and FIG. 3 is a flowchart.

  In FIG. 1, an outdoor unit 1 includes an inverter-driven capacity (frequency) variable compressor 2 (hereinafter simply referred to as a compressor), an outdoor heat exchanger 3, an outdoor blower 4, and a four-way valve 5 for switching between heating and cooling. And are provided. A compressor discharge temperature detection device (discharge temperature detection unit) 15 is provided on the discharge pipe connected to the compressor 2 or the top surface of the compressor 2, and the compressor intake temperature is provided on the suction pipe connected to the compressor 2. A detection device (intake temperature detection unit) 16 is provided. The outdoor heat exchanger 3 is provided with an outdoor heat exchanger temperature detection device 17.

  On the other hand, the indoor unit 7 is provided with an indoor fan 8 and an indoor heat exchanger 9. The indoor heat exchanger 9 is provided with an indoor heat exchanger temperature detection device 18.

  The outdoor unit 1 includes a liquid side connection portion 13 and a gas side connection portion 14. The outdoor unit 1 is connected to the indoor unit 7 by connection piping connected to the liquid side connection unit 13 and the gas side connection unit 14.

  The refrigerant liquid pipe 11, which is a pipe connecting the liquid side connecting portion 13 and the outdoor heat exchanger 3, is provided with an electric expansion valve 6, which is a throttling device capable of pulse-controlling the valve opening by a stepping motor, for example. It has been.

  The compressor 2, the outdoor heat exchanger 3, the four-way valve 5, the electric expansion valve 6, and the indoor heat exchanger 9 are connected in a ring shape to form a refrigeration cycle circuit. R32 (difluoromethane) is enclosed as a refrigerant in the refrigeration cycle circuit. R32 is a refrigerant having a tendency that the discharge temperature of the compressor 2 rapidly increases when the suction superheat degree of the compressor 2 exceeds a certain value.

  In addition, the indoor unit 7 is provided with an operation setting device 10 that sets an operation mode (cooling, dehumidification or heating) desired by a resident, a target room temperature, and instructs operation or stop. The operation setting device 10 is, for example, a remote controller.

  The outdoor unit 1 includes a control device that adjusts the rotational speed of the compressor 2, the rotational speed of the outdoor blower 4, the switching of the four-way valve 5, the opening degree of the electric expansion valve 6, and the like according to the setting of the operation setting device 10. 20 is provided.

  During the cooling or dehumidifying operation, the outdoor heat exchanger 3 serves as a condenser, and the indoor heat exchanger 9 serves as an evaporator. For this reason, the indoor heat exchanger temperature detector 18 serves as an evaporator temperature detector. During the heating operation, the indoor heat exchanger 9 serves as a condenser, and the outdoor heat exchanger 3 serves as an evaporator. For this reason, the outdoor heat exchanger temperature detector 17 serves as an evaporator temperature detector.

  In the refrigeration cycle apparatus having the above configuration, during cooling or dehumidifying operation, the refrigerant discharged from the compressor 2 flows to the outdoor heat exchanger 3 through the four-way valve 5, and the outdoor fan 4 is driven to drive the outdoor heat exchanger. 3 heat-exchanges with outdoor air and condensates. Thereafter, the flow rate of the refrigerant passes through the refrigerant liquid pipe 11 and is controlled by the electric expansion valve 6. The refrigerant decompressed by the electric expansion valve 6 evaporates in the indoor heat exchanger 9 of the indoor unit 7 and then is sucked into the compressor 2 again through the refrigerant gas pipe 12 and the four-way valve 5.

  Since this electric expansion valve 6 is pulse-controlled by a stepping motor or the like so as to have an opening corresponding to the load in the room, the refrigerant is adjusted to a flow rate corresponding to the room load.

On the other hand, during the heating operation, the refrigerant discharged from the compressor 2 flows to the indoor heat exchanger 9 through the four-way valve 5, and exchanges heat with indoor air in the indoor heat exchanger 9 by driving the indoor blower 8. To condense. Thereafter, the flow rate of the refrigerant is controlled by the electric expansion valve 6. The refrigerant decompressed by the electric expansion valve 6 evaporates in the outdoor heat exchanger 3 and then is sucked into the compressor 2 again through the four-way valve 5.

  FIG. 2 is a control block diagram of the present embodiment. The electric expansion valve 6 is connected to the control device. The control device includes an output relay circuit that controls a stepping motor and the like, and a determination device that outputs a signal to the output relay circuit. The determination device is connected to the compressor discharge temperature detection device 15, the compressor suction temperature detection device 16, the outdoor heat exchanger temperature detection device 17, the indoor heat exchanger temperature detection device 18, and the suction superheat degree detection device 19. The suction superheat degree detection device (suction superheat degree calculation unit) 19 is configured to suck the compressor 2 from the detected values of the compressor suction temperature detection device 16, the outdoor heat exchanger temperature detection device 17, and the indoor heat exchanger temperature detection device 18. The degree of superheat is calculated.

  The determination device determines, based on the outputs of these detection devices, the target discharge temperature set value, the suction superheat degree set value, the discharge temperature set value calculated from these outputs, and the predetermined discharge temperature determination value. The electric expansion valve 6 is adjusted to the calculated opening.

  Next, the control of the present embodiment will be described using the flowchart of FIG.

  The resident selects, for example, heating with the operation setting device 10 and instructs the start of operation. When the compressor 2 starts operation (S000), the compressor discharge temperature detector 15 detects the compressor discharge temperature (hereinafter simply referred to as discharge temperature) (Td1) (S001).

  The discharge temperature (Td1) is compared with a predetermined discharge temperature determination value (TdA) (S002). When the discharge temperature (Td1) is equal to or lower than the discharge temperature determination value (TdA) (Yes in S002), the suction superheat degree (SH) of the compressor 2 is detected (S003).

  The suction superheat degree (SH) is compared with a predetermined suction superheat degree set value (SHA) (S004). When the intake superheat degree (SH) is higher than the intake superheat degree set value (SHA) (Yes in S004), the electric expansion valve 6 is opened A (PLS) in the opening direction (S005). When the suction superheat degree (SH) is lower than the suction superheat degree set value (SHA) (No in S004), the suction superheat degree (SH) is compared with “suction superheat degree set value (SHA) -1 ° C.” ( S006). When the suction superheat degree (SH) is not less than “suction superheat degree set value (SHA) -1 ° C.” and not more than the suction superheat degree set value (SHA) (No in S006), the electric expansion valve 6 is not opened / closed. (S007). If the suction superheat degree (SH) is smaller than “suction superheat degree set value (SHA) −1 ° C.” (Yes in S006), the electric expansion valve 6 is closed B (PLS) in the closing direction (S008). Thus, the control is performed so as to keep the suction superheat degree (SH) at a certain appropriate value (SHA).

  That is, when the discharge temperature (Td) is smaller than the discharge temperature determination value (TdA), the opening / closing of the electric expansion valve 6 is adjusted by suction superheat degree control.

  The number of pulses in the opening direction A (PLS) and the closing direction B (PLS) of the electric expansion valve 6 is determined by the difference between the suction superheat degree (SH) and the suction superheat degree setting value (SHA). Is set to a large number of pulses.

Further, in the case of heating, the intake superheat degree is determined based on the outdoor heat exchanger temperature detected from the outdoor heat exchanger temperature detection device 17 based on the compressor intake temperature detected from the compressor intake temperature detection device 16 (during heating). (Evaporation temperature) is reduced. If this difference is large, the degree of superheat sucked into the compressor 2 increases, so that the refrigerating machine oil of the compressor 2 due to a decrease in efficiency of the compressor 2 or an increase in the temperature of refrigerant discharged from the compressor 2. Cause deterioration of compressors and compressor motors. If this difference is small, liquid-rich refrigerant is sucked into the compressor 2, leading to a reduction in efficiency of the compressor 2 and mechanical damage due to a large amount of liquid. For this reason, it is necessary to control the suction superheat degree with an appropriate value.

  Note that, in the case of cooling, the intake superheat degree is determined based on the indoor heat exchanger temperature detected from the indoor heat exchanger temperature detection device 18 from the compressor intake temperature detected from the compressor intake temperature detection device 16 (during cooling). (Evaporation temperature) is reduced.

  On the other hand, when the discharge temperature (Td1) becomes higher than the discharge temperature value (TdA) (No in S002), the suction superheat degree (SH) of the compressor is detected (S009), and the suction superheat degree (SH) is set to the predetermined suction. Comparison is made with the superheat setting value (SHA) (S010). When the intake superheat degree (SH) is higher than the intake superheat degree set value (SHA) (No in S010), the electric expansion valve 6 is opened C (PLS) in the opening direction (S011).

  When the suction superheat degree (SH) is lower than the suction superheat degree set value (SHA) (Yes in S010), it is determined whether or not the change in the discharge temperature is larger than a predetermined value. Specifically, it is determined whether or not the difference between the current discharge temperature (Td1) and the previously detected discharge temperature (Td0) is smaller than a first predetermined value (for example, 0.4 ° C.) (S012). The discharge temperature (Td0) detected last time is, for example, the discharge temperature detected in S001 in the immediately preceding control cycle.

  When the suction superheat degree (SH) is lower than the suction superheat degree set value (SHA) and the discharge temperature (Td1) detected this time is higher than the discharge temperature (Td0) detected last time by 0.4 ° C. or more (No in S012) ) Does not open or close the electric expansion valve 6 (S013). That is, it waits for the discharge temperature to stabilize with the current opening of the expansion valve.

  When the difference between the discharge temperature (Td0) detected last time and the discharge temperature (Td1) detected this time is less than 0.4 ° C. (S012), it is determined whether or not the change in the discharge temperature is larger than a predetermined value. Specifically, it is determined whether or not the difference between the current discharge temperature (Td1) and the previously detected discharge temperature (Td0) is greater than a second predetermined value (eg, 0 ° C.) (S014).

  If the change in the discharge temperature is greater than 0 ° C. (Yes in S014), the electric expansion valve 6 is closed D (PLS) in the closing direction (S015). When the change in the discharge temperature is smaller than 0 ° C. (No in S014), the electric expansion valve 6 is closed E (PLS) in the closing direction (S016). E is the number of pulses larger than D.

  That is, in the state where the opening degree of the electric expansion valve 6 is fixed (state of S013), the change in the discharge temperature becomes small (approaching the stable state), the discharge temperature (Td0) detected last time and the discharge temperature (Td1) detected this time. ) Is less than 0.4 ° C. (Yes in S012) and the change in the discharge temperature is 0 ° C. or more (Yes in S014), the electric expansion valve 6 is throttled by D (PLS) (S015). The opening degree of the expansion valve 6 is changed slowly.

  On the other hand, when the change amount of the discharge temperature becomes small (No in S014), it is determined that the throttle amount is insufficient because the discharge temperature is low. (PLS) is narrowed down (S016).

  As described above, when the discharge temperature (Td1) is higher than the discharge temperature determination value (TdA), the opening / closing of the electric expansion valve 6 is adjusted according to the amount of change in the discharge temperature.

By performing the above operation at a predetermined control interval, the suction superheat degree (SH) is continuously controlled so as to approach the target superheat degree set value (SHA). By controlling in this way, when the discharge temperature is likely to rise rapidly, the amount of operation of the expansion device can be suppressed, over-throttle and over-opening can be prevented, and a large change in the discharge temperature can be suppressed. Degree control (intake superheat degree control)
Can be performed stably.

(Embodiment 2)
FIG. 4 is a flowchart of control in the second embodiment. Since the configuration of the refrigeration cycle and the control block configuration are the same as those in the first embodiment, the description thereof is omitted.

  The resident selects, for example, heating with the operation setting device 10 and instructs the start of operation. When the compressor 2 starts operation (S100), the compressor discharge temperature detection device 15 detects the current compressor discharge temperature (Td1) (S101).

  The discharge temperature (Td1) is compared with a predetermined discharge temperature determination value (TdB) (S002). When the discharge temperature (Td1) is equal to or lower than the discharge temperature determination value (TdB) (Yes in S102), the suction superheat degree (SH) of the compressor 2 is detected (S103).

  The suction superheat degree (SH) is compared with a predetermined suction superheat degree setting value (SHA) (S104). When the suction superheat degree (SH) is higher than the suction superheat degree set value (SHA) (Yes in S104), the electric expansion valve 6 is opened A (PLS) in the opening direction (S105).

  When the suction superheat degree (SH) is not less than “suction superheat degree set value (SHA) -1 ° C.” (S106) and not more than the suction superheat degree set value (SHA) (Yes in S104), the electric expansion valve 6 Opening and closing is not performed (S107).

  If the suction superheat degree (SH) is smaller than “suction superheat degree set value (SHA) −1 ° C.” (Yes in S106), the electric expansion valve 6 is closed B (PLS) in the closing direction (S108). Thus, the control is performed so as to keep the suction superheat degree (SH) at a certain appropriate value (SHA).

  The number of pulses in the opening direction A (PLS) and the closing direction B (PLS) of the electric expansion valve 6 is determined by the difference between the suction superheat degree (SH) and the suction superheat degree set value (SHA). When it is large, the number of pulses is set to be large.

  In the case of heating, the intake superheat degree (SH) is determined based on the outdoor heat exchanger temperature (detected from the outdoor heat exchanger temperature detection device 17 from the compressor intake temperature detected from the compressor intake temperature detection device 16). The evaporation temperature during heating is reduced. When this difference is large, the suction superheat degree (SH) of the compressor 2 is increased, the efficiency of the compressor 2 is reduced, and the temperature of the refrigerant discharged from the compressor 2 is increased. Cause deterioration of compressors and compressor motors. If this difference is small, liquid-rich refrigerant is sucked into the compressor 2, leading to a reduction in efficiency of the compressor 2 and mechanical damage due to a large amount of liquid. For this reason, it is necessary to control the suction superheat degree with an appropriate value.

  On the other hand, when the discharge temperature (Td1) becomes higher than the discharge temperature value (TdB) (Yes in S102), the control shifts from the suction superheat degree control to the discharge temperature control. That is, the control target is set to the target value of the discharge temperature, and the expansion device is controlled so as to approach this target value.

  At the time of switching to this control method, the discharge temperature (Td1) at that time is set as the initial discharge temperature setting value (TdX) (S109). Next, the suction superheat degree (SH) is detected (S110).

  It is determined whether or not the suction superheat degree (SH) is larger than the suction superheat degree set value (SHA) by a predetermined value or more. Specifically, the suction superheat degree (SH) is compared with “suction superheat degree set value (SHA) + 0.5 ° C.” (S111).

  When the suction superheat degree (SH) is higher than the suction superheat degree setting value (SHA) by 0.5 ° C. or more (Yes in S111), the discharge temperature (Td1) adds a predetermined value of the discharge temperature set value (TdX). It is determined whether or not the value is smaller. Specifically, the discharge temperature (Td1) is compared with “discharge temperature set value (TdX) + 1 ° C.” (S112).

  If the suction superheat degree (SH) is higher than the suction superheat degree set value (SHA) by 0.5 ° C. or more (Yes in S111) and the discharge temperature (Td1) is lower than the discharge temperature set value (TdX) +1 (° C.) ( Since the sufficient degree of suction superheat has already been taken and there is no need to raise the discharge temperature any more, the discharge temperature set value (TdX) is lowered by a predetermined value (for example, 1 ° C.) (S113).

  In other cases, the discharge temperature set value (TdX) is not changed (S114). Specifically, when the difference between the suction superheat degree (SH) and the suction superheat degree setting value (SHA) is smaller than 0.5 ° C. (No in S111), the suction superheat degree (SH) approaches the set value. Since the suction superheat degree is clearly lower than the target and the electric expansion valve 6 needs to be further throttled, the discharge temperature set value (TdX) is not changed (S114). When the discharge temperature (Td1) is 1 ° C. or more higher than the discharge temperature set value (TdX) (No in S112), the suction superheat degree (SH) is taken and the discharge temperature (Td1) reaches the discharge temperature set value. In this case, the discharge temperature set value (TdX) is not changed (S114).

  Next, it is determined whether or not the current discharge temperature (Td1) is higher than a predetermined value (for example, 1 ° C.) by a predetermined value (for example, 1 ° C.) with respect to the discharge temperature setting value (TdX) determined as described above. Specifically, the discharge temperature (Td1) is compared with “discharge temperature set value (TdX) + 1 ° C.” (S115). If the current discharge temperature (Td1) is higher than the discharge temperature set value (TdX) by 1 ° C. or more (Yes in S115), the electric expansion valve 6 is opened C (PLS) to lower the discharge temperature (S116).

  When the discharge temperature (Td1) is smaller than the value obtained by adding 1 ° C. to the discharge temperature set value (TdX) (No in S115), the current discharge temperature (Td1) is set to a predetermined value from the discharge temperature set value (TdX). It is judged whether it is smaller than the subtracted value. Specifically, the discharge temperature (Td1) is compared with “discharge temperature set value (TdX) −1 ° C.” (S117).

  When the discharge temperature (Td1) is smaller than “discharge temperature set value (TdX) + 1 ° C.” (No in S115) and larger than “discharge temperature set value (TdX) −1 ° C.” (No in S117), the discharge temperature Since (Td1) is approaching a temperature within 1 ° C. with respect to the target discharge temperature setting value (TdX), the electric expansion valve 6 is not opened or closed (S118).

  If the discharge temperature (Td1) is lower than “discharge temperature set value (TdX) −1 ° C.” (Yes in S117), the electric expansion valve 6 is closed D (PLS) in the closing direction to increase the discharge temperature (S119). . In this way, the electric expansion valve 6 is continuously controlled so as to obtain an appropriate discharge temperature.

  In the present embodiment, when switching from the suction superheat degree control to the discharge temperature control, the discharge temperature set value (TdX) is changed according to the suction superheat degree (SH) and the discharge temperature (Td1), whereby the discharge temperature (Td ) And the discharge temperature set value (TdX) can always be reduced, so that the opening and closing of the electric expansion valve 6 is also reduced, and fluctuations in the discharge temperature (Td) can be suppressed.

For this reason, the refrigerant circulation amount fluctuates greatly, resulting in a decrease in comfort, efficiency, and reliability due to changes in equipment capacity (fluctuation in blowing temperature) (refrigerating machine oil deterioration due to excessive increase in discharge temperature and compressor) Motor deterioration). (Embodiment 3)
FIG. 5 is a flowchart of control in the third embodiment. Since the configuration of the refrigeration cycle and the control block configuration are the same as those in the first embodiment, the description thereof is omitted.

  The resident selects, for example, heating with the operation setting device 10 and instructs the start of operation. When the compressor 2 starts operation (S200), the compressor discharge temperature detection device 15 detects the current compressor discharge temperature (Td1) (S201).

  When the discharge temperature (Td1) is equal to or lower than the discharge temperature determination value (TdB) (No in S202), the suction superheat degree (SH) of the compressor is detected (S203), and the suction superheat degree (SH) is the suction superheat degree. When it is higher than the set value (SHA) (Yes in S204), the electric expansion valve 6 is opened A (PLS) in the opening direction (S205).

  When the suction superheat degree (SH) is equal to or lower than the suction superheat degree set value (SHA) (No in S204) and is equal to or higher than “suction superheat degree set value (SHA) -1 ° C.” (No in S206), the electric expansion valve 6 is not opened or closed (S207).

  When the intake superheat degree (SH) is equal to or lower than the intake superheat degree set value (SHA) (No in S204) and is lower by “1 ° C. than the intake superheat degree set value (SHA)” (Yes in S206), the electric expansion valve 6 is closed in the closing direction by B (PLS) (S208). Thus, the control is performed so as to keep the suction superheat degree (SH) at a certain appropriate value (SHA).

  The number of pulses in the opening direction A (PLS) and the closing direction B (PLS) of the electric expansion valve 6 is determined by the difference between the suction superheat degree (SH) and the suction superheat degree set value (SHA). When it is large, the number of pulses is set to be large.

  Further, in the case of heating, the intake superheat degree is determined based on the outdoor heat exchanger temperature detected from the outdoor heat exchanger temperature detection device 17 based on the compressor intake temperature detected from the compressor intake temperature detection device 16 (during heating). (Evaporation temperature) is reduced. When this difference is large, the suction superheat degree of the compressor 2 is increased, the efficiency of the compressor 2 is decreased, the deterioration of the refrigerating machine oil of the compressor 2 due to the temperature of the refrigerant discharged from the compressor 2 is increased, It causes deterioration of the compressor motor. If this difference is small, liquid-rich refrigerant is sucked into the compressor 2, leading to a reduction in efficiency of the compressor 2 and mechanical damage due to a large amount of liquid. For this reason, it is necessary to control the suction superheat degree with an appropriate value.

  On the other hand, when the discharge temperature (Td1) becomes higher than the discharge temperature value (TdB) (Yes in S202), the discharge temperature (Td1) at that time is set as the initial discharge temperature setting value (TdX) (S209). Next, the suction superheat degree (SH) is detected (S210).

  It is determined whether or not the suction superheat degree (SH) is larger than the suction superheat degree set value (SHA) by a predetermined value or more. Specifically, the suction superheat degree (SH) is compared with “suction superheat degree set value (SHA) + 0.5 ° C.” (S211).

  When the suction superheat degree (SH) is higher than “suction superheat degree set value (SHA) + 0.5 ° C.” (Yes in S211), the apparatus can be operated efficiently without further increasing the discharge temperature. Therefore, the discharge temperature set value (TdX) is not changed (S212).

  When it is determined that the suction superheat degree (SH) is not sufficient, for example, when the suction superheat degree value (SHA) is smaller than 0.5 ° C. (No in S211), the current discharge temperature (Td1) is When it approaches the discharge temperature set value (TdX) and exceeds a predetermined value, it is determined whether or not it is lower than the discharge temperature set value (TdC) set in advance as the upper limit value of the control range.

  Specifically, the discharge temperature (Td1) is compared with “discharge temperature set value (TdX) −1 ° C.” (S213).

  When the opening / closing of the electric expansion valve 6 is controlled for a while under the condition of the discharge temperature control, the suction superheat degree (SH) cannot be obtained, and the discharge temperature (Td1) tends to decrease, “discharge temperature set value (TdX) −1”. When the temperature is equal to or lower than “° C.” (No in S213), the electric expansion valve 6 continues to operate in the closing direction so as to approach the discharge temperature set value (TdX), and thus the discharge temperature set value (until the discharge temperature approaches the discharge temperature set value). TdX) is not changed (S212).

If the suction superheat degree (SH) is not obtained and the discharge temperature (td1) approaches “discharge temperature setting (TdX) −1 ° C.” or more (Yes in S213), the suction superheat degree (SH) is In order to avoid stabilization in an insufficient state, assuming that the discharge temperature (Td1) is equal to or lower than the upper limit discharge temperature set value (TdC), the suction superheat degree (SH) is set to the suction superheat degree set value ( The discharge temperature set value (TdX) is gradually increased so as to approach SHA). (For example, increase the discharge temperature set value (TdX) by 1 ° C.) (S214)
The discharge temperature set value (TdC) is a numerical value with a little margin with respect to the upper limit value of the discharge temperature at which the high discharge temperature protection operation is started, and is smaller than the compressor protection operation determination temperature. When the discharge temperature is equal to or higher than the discharge temperature set value (TdC), the electric expansion valve 6 always operates in the opening direction so as to approach the discharge temperature set value (TdX). Since the opening degree of the electric expansion valve 6 is not changed, the opening degree of the electric expansion valve 6 can be controlled stably.

  Next, it is determined whether or not the current discharge temperature (Td1) is higher by a predetermined value (for example, 1 ° C.) than the discharge temperature set value (TdX) to be changed as described above. Specifically, the discharge temperature (Td1) is compared with “discharge temperature set value (TdX) + 1 ° C.” (S215). If the current discharge temperature (Td1) is higher than the discharge temperature set value (TdX) by 1 ° C. or more (Yes in S215), the electric expansion valve 6 is opened C (PLS) to lower the discharge temperature (S216).

  When the discharge temperature (Td1) is smaller than the value obtained by adding 1 ° C. to the discharge temperature set value (TdX) (No in S215), the current discharge temperature (Td1) is set to a predetermined value from the discharge temperature set value (TdX). It is judged whether it is smaller than the subtracted value. Specifically, the discharge temperature (Td1) is compared with “discharge temperature set value (TdX) −1 ° C.” (S217).

  When the discharge temperature (Td1) is smaller than “discharge temperature set value (TdX) + 1 ° C.” (No in S215) and larger than “discharge temperature set value (TdX) −1 ° C.” (No in S217), the discharge temperature Since (Td1) is close to the target discharge temperature setting value (TdX), the electric expansion valve 6 is not opened or closed (S218).

  When the discharge temperature (Td1) is equal to or lower than “discharge temperature set value (TdX) −1 ° C.” (Yes in S217), the electric expansion valve 6 is closed by D (PLS) in the closing direction (S219). Thus, the electric expansion valve 6 is continuously controlled so as to approach the optimum discharge temperature at which an appropriate suction superheat degree (SH) can be obtained.

  By controlling in this way, even in a situation where the suction superheat degree (SH) cannot be obtained, the discharge temperature is not increased excessively and continuously at the discharge temperature closest to the state where the suction superheat degree (SH) is taken. It becomes possible to drive.

That is, when the suction superheat degree (SH) is insufficient in the suction superheat degree control, the discharge temperature is continuously raised, and eventually the operation of high discharge temperature protection is performed. In this case, however, the suction superheat degree (SH) The expansion valve is operated so as to approach the target intake superheat degree setting value (SHA), but when the discharge temperature approaches the upper limit, further temperature rise can be suppressed, and stable operation is performed without impairing comfort. Can be realized.

  In the above embodiment, 1 ° C. of “suction superheat setting value (SHA) −1 ° C.” and “discharge temperature setting value (Td1) −1 ° C.” may not be 1 ° C., for example, It may be several degrees Celsius.

  Further, the first embodiment can be implemented by combining any of the second embodiment and the third embodiment. In this case, it is desirable that the discharge temperature set value (TdB) is a value larger than the discharge temperature set value (TdA).

  As described above, this embodiment connects an outdoor unit having a variable capacity compressor, an outdoor heat exchanger, a blower, a four-way valve, and a throttle device, a heat exchanger, and an indoor unit having a blower. Provided with an indoor heat exchanger temperature detecting device for detecting the temperature of the indoor heat exchanger, and an outdoor unit for detecting the temperature of the refrigerant discharged from the compressor and the outdoor heat exchanger for detecting the temperature of the refrigerant discharged from the compressor in the outdoor unit. A heat exchanger temperature detecting device and a compressor suction temperature detecting device for detecting the temperature of refrigerant sucked into the compressor are provided, and detected from a suction superheat degree detecting device for detecting the degree of superheat on the suction side of the compressor. The throttle device is controlled so that the value of the suction superheat temperature becomes a predetermined temperature. If the discharge temperature detected by the compressor discharge temperature detection device exceeds a predetermined temperature, the current discharge temperature and the previous detection are detected. The difference from the discharge temperature In an air conditioner that controls the throttle device so that it does not operate excessively by reducing the opening / closing amount of the throttle device and predicting the change point where the discharge temperature suddenly rises, the amount of operation of the throttle device when the discharge temperature exceeds the predetermined temperature When the control is switched to the control for reducing the discharge temperature, if the change amount of the discharge temperature is large, the operation of the throttle device is stopped for a while, and the standby state is kept until the change amount of the discharge temperature converges to some extent.

  Even if the operation of the expansion device is stopped, the discharge temperature continues to change for a while, but when the amount of change gradually subsides, the control moves to the next stage, and the expansion device slowly resumes operation, and the target suction overheat It is controlled to approach the set value.

  When the load on the air conditioner is light, it is sufficient to control the throttle device with this suction superheat setting value. However, when the load on the air conditioner increases, the throttle device continues to be throttled in the closing direction to take the suction superheat. In some cases, the discharge temperature exceeds the upper limit that can be controlled by the device.

  In such a case, since the suction superheat degree cannot be controlled, it is necessary to switch to the discharge temperature control with the discharge temperature as the control target. The setting device of the discharge temperature is corrected from the state, and the expansion device is controlled slowly with the aim of an appropriate discharge temperature setting value.

  As a control method, first, the state of the suction superheat degree is observed from the discharge temperature when switching from the suction superheat degree control to the discharge temperature control as the initial discharge temperature set value up to a predetermined upper limit discharge temperature set value. While increasing or decreasing the discharge temperature set value, the control target value is determined. When the value of the suction superheat detection device exceeds a certain temperature, the discharge temperature setting value is slightly decreased, and only when the value of the suction superheat detection device is less than the predetermined temperature, the discharge temperature setting value is slightly increased. .

  However, if the discharge temperature is below a certain temperature with respect to the discharge temperature set value, that is, if the discharge temperature is considerably lower than the discharge temperature set value, the temperature of the discharge temperature set value is Do not raise.

  Only when the temperature difference between the discharge temperature and the discharge temperature set value is equal to or lower than a predetermined temperature, that is, when the discharge temperature approaches the value of the discharge temperature set value, the value of the discharge temperature set value is slightly increased.

  By incorporating the action to keep the current suction superheat level at the optimum value while controlling the discharge temperature in this way, comfort and efficiency decrease due to sudden fluctuations in the flow rate of the expansion device, and discharge temperature is excessively increased. Therefore, it is possible to avoid the deterioration of the reliability of the equipment such as the deterioration of the refrigeration oil and the deterioration of the compressor motor, which makes it possible to supply comfortable and reliable equipment.

  In particular, when controlling the discharge temperature, the temperature of the control target actually increases when the control target response is poor, such as when a compressor discharge temperature detector is installed on the top surface of the compressor with a large heat capacity. It takes some time to do.

  For example, even if the refrigerant discharge temperature is going to rise from now on, the current temperature is low, so the throttle device may be operated to the temperature rise side, resulting in an excessive throttle state. When this occurs, predict that the subsequent discharge temperature will rise or fall, and change the amount of change in the expansion device and the operation interval to find the actual temperature change point and bring it closer to the target temperature. Is possible.

  By controlling in this way, the sudden rise or fall of the discharge temperature due to excessive operation of the throttle device can be suppressed, and deterioration in the reliability of the equipment such as deterioration of refrigeration oil and burnout of the compressor motor can be avoided, making it comfortable and reliable High-quality equipment can be supplied. Further, when the discharge temperature reaches a predetermined value, switching from the suction superheat control to the discharge temperature control and slowly controlling the expansion device aiming at the discharge temperature set value, the suction superheat control controls the discharge temperature. Even under high load conditions exceeding the limit value, it is possible to provide a comfortable, stable and reliable device.

  As described above, the refrigeration cycle apparatus according to the present invention can avoid large fluctuations in the discharge temperature, appropriately control the expansion valve, and improve comfort and reliability. It can also be applied to multi-air conditioners for buildings.

DESCRIPTION OF SYMBOLS 1 Outdoor unit 2 Compressor 3 Outdoor heat exchanger 4 Outdoor fan 5 Four way valve 6 Electric expansion valve 7 Indoor unit 8 Indoor fan 9 Indoor heat exchanger 10 Operation setting apparatus 11 Refrigerant liquid pipe 12 Refrigerant gas pipe 13 Liquid side connection part 14 Gas side connection 15 Compressor discharge temperature detection device 16 Compressor suction temperature detection device 17 Outdoor heat exchanger temperature detection device 18 Indoor heat exchanger temperature detection device 19 Suction superheat degree detection device 20 Control device

Claims (3)

Compressor, condenser, expansion device, evaporator, discharge temperature detection unit for detecting the temperature of refrigerant discharged from the compressor, and suction superheat degree calculation for calculating the degree of superheat of refrigerant sucked into the compressor And when the discharge temperature detected by the discharge temperature detection unit is smaller than a predetermined discharge temperature determination value , the throttle is reduced when the suction superheat degree calculated by the suction superheat degree calculation unit is larger than a predetermined value. When the flow rate of refrigerant passing through the apparatus is increased and the suction superheat degree calculated by the suction superheat degree calculation unit is equal to or less than a predetermined value, the suction superheat degree is compared with a value that is one degree lower than the predetermined value, If it is less than this value, the flow rate of refrigerant passing through the throttle device is decreased, and if it is greater than this value, the flow rate of refrigerant passing through the throttle device is not changed, and the discharge temperature is a predetermined discharge temperature judgment value. in the case of above, the suction superheat When the change amount of the discharge temperature is less than the predetermined value when the discharge temperature is less than the predetermined value, the refrigerant flow rate passing through the throttle device is decreased, and when the change amount of the discharge temperature is the predetermined value or more, the refrigerant flow is passed. The refrigeration cycle apparatus is characterized in that the refrigerant flow rate is not changed, and the refrigerant flow rate passing through the expansion device is increased when the suction superheat degree is not less than a predetermined value . Compressor, condenser, expansion device, evaporator, discharge temperature detection unit for detecting the temperature of refrigerant discharged from the compressor, and suction superheat degree calculation for calculating the degree of superheat of refrigerant sucked into the compressor A discharge flow rate detected by the discharge temperature detection unit is greater than a predetermined discharge temperature determination value, the flow rate of the refrigerant passing through the expansion device is adjusted so that the discharge temperature becomes a discharge temperature set value. The discharge temperature setting value is adjusted based on the discharge temperature when the predetermined discharge temperature is exceeded, the suction superheat degree is larger than the suction superheat degree set value, and the discharge temperature is the discharge temperature. The refrigeration cycle apparatus characterized by lowering the discharge temperature set value when it is smaller than the set value. The refrigeration cycle apparatus according to claim 2, wherein when the suction superheat degree is smaller than the suction superheat degree set value and the discharge temperature is larger than the discharge temperature set value, the discharge temperature set value is increased. .