JP6570328B2 - Air conditioner and control method thereof - Google Patents

Description

  The present invention relates to an air conditioner and a control method thereof, and more particularly to an air conditioner having a heating function and a control method thereof.

  Conventionally, various control methods have been proposed for compressors of air conditioners. For example, Patent Document 1 (Japanese Patent Laid-Open No. 11-248229), Patent Document 2 (Japanese Patent Laid-Open No. 2006-78089), and the like have proposed control of the rotational speed.

  Lubricating oil for lubricating the compressor is used in the compressor of such an air conditioner. When heating operation is started under conditions where the outside air temperature is low (below freezing point, etc.), the viscosity of the lubricating oil becomes high due to the low temperature, and as a result, the compressor cannot be sufficiently lubricated (hereinafter, the oil level runs out). However, there was a problem that the parts were worn out and failed, and the long-term reliability of the compressor was impaired. However, the above Patent Documents 1 and 2 do not propose a solution for this oil level cut.

  For example, a method disclosed in Patent Document 3 (Japanese Patent Laid-Open No. 2006-170457) has been proposed as a method for coping with the oil level cut. In the air conditioner of Patent Document 3, the electronic expansion valve is completely closed (or closed to the extent that refrigerant does not flow) in the initial stage (when starting) when heating operation is started in a state where the outside air temperature is low. To control. Thus, the refrigerant does not return to the suction side of the compressor 5 and only the lubricating oil is returned to the suction side.

JP 11-248229 A JP 2006-78089 A JP 2006-170457 A

  In the control method of Patent Document 3 described above, when the heating operation is started, the operation is performed with the expansion valve in a substantially fully closed state, but the timing for releasing the fully closed state is not disclosed. Therefore, there is a possibility that a sufficient amount of refrigerant circulation cannot be obtained during heating operation.

  Therefore, an object of the present disclosure is to provide an air conditioner and a control method thereof that prevent a decrease in the reliability of the compressor due to running out of oil while obtaining a sufficient amount of refrigerant in heating operation.

  An air conditioner according to an aspect of the present disclosure has a movable part, and a compressor for compressing a refrigerant by periodically moving the movable part, and outdoor heat for exchanging heat between outdoor air and the refrigerant. An exchanger, an indoor heat exchanger for exchanging heat between the indoor air and the refrigerant, a fan for blowing the air after heat exchange by the indoor heat exchanger into the room, and an outdoor temperature for detecting the outdoor temperature A sensor, an indoor temperature sensor for detecting the temperature of the indoor heat exchanger, and a control unit for controlling the air conditioner.

  The control unit includes a compressor control unit for controlling the compressor. When starting the heating operation in which the refrigerant circulates in order through the compressor, the indoor heat exchanger, and the outdoor heat exchanger, when the temperature below freezing is detected by the outdoor temperature sensor, the compressor controller is movable. Control of the compressor is started so that the part moves according to the first period, and then when the temperature lower than the temperature for starting rotation of the fan is detected by the indoor temperature sensor, The compressor is controlled so that the period of motion is changed from the first period to a second period longer than the first period.

  Preferably, the control unit further includes a fan control unit for controlling the fan. The compressor control unit controls the compressor to stop for a predetermined period, and the fan control unit controls the fan to rotate for the predetermined period. The control unit controls the air conditioner so that the heating operation is started after the predetermined period has elapsed.

  Preferably, the air conditioner further includes an expansion valve for adjusting the flow rate of the refrigerant. The control unit includes a valve control unit for controlling the expansion valve. In the period from when the compressor control unit starts to control the compressor until the fan starts rotating, the valve control unit sets the expansion valve so that the flow rate of the refrigerant is smaller than the flow rate for the heating operation. To control the opening degree.

  An air conditioner according to another aspect of the present disclosure includes a movable part, and a compressor for compressing the refrigerant by periodically moving the movable part, and an outdoor for exchanging heat between the outdoor air and the refrigerant. A heat exchanger, an indoor heat exchanger for exchanging heat between the indoor air and the refrigerant, a fan for blowing the air after heat exchange by the indoor heat exchanger into the room, and an outdoor that detects the outdoor temperature A temperature sensor, an indoor temperature sensor that detects the temperature of the indoor heat exchanger, and a control unit that controls the air conditioner are provided.

  When the control unit starts heating operation in which the refrigerant circulates in order through the compressor, the indoor heat exchanger, and the outdoor heat exchanger, when the temperature below the freezing point is detected by the outdoor temperature sensor, the movable unit Control of the compressor is started to move according to a predetermined cycle. After that, when the temperature for starting the rotation of the fan is detected by the indoor temperature sensor, the control unit is configured for the heating operation in which the cycle of movement of the movable unit is shorter than the cycle from a predetermined cycle. The compressor is controlled so that the cycle changes according to the set temperature.

  According to still another aspect of the present disclosure, a method for controlling an air conditioner is provided. The air conditioner has a movable part, periodically moves the movable part to compress the refrigerant, an outdoor heat exchanger for exchanging heat between outdoor air and the refrigerant, An indoor heat exchanger for exchanging heat between air and refrigerant, a fan for blowing air after heat exchange by the indoor heat exchanger into the room, an outdoor temperature sensor for detecting the outdoor temperature, and indoor heat exchange And an indoor temperature sensor for detecting the temperature of the vessel.

  The above control method is movable when a temperature below freezing point is detected by the outdoor temperature sensor when the heating operation in which the refrigerant circulates in order through the compressor, the indoor heat exchanger, and the outdoor heat exchanger is started. When the controller starts controlling the compressor so that the unit moves according to the first period and the indoor temperature sensor detects a temperature lower than the temperature for starting the rotation of the fan, Controlling the compressor such that the period of motion changes from the first period to a second period longer than the first period.

  According to the present disclosure, it is possible to prevent a reduction in the reliability of the compressor due to the oil level running out while obtaining a sufficient amount of refrigerant in the heating operation.

It is a figure which shows typically the refrigerant circuit in the air conditioner in Embodiment 1 of this invention. It is an external view of the indoor unit 100 of the air conditioner in Embodiment 1 of the present invention. It is sectional drawing which shows schematically the internal structure of the indoor unit 100 of FIG. It is an external view of the outdoor unit 200 of the air conditioner in Embodiment 1 of the present invention. It is a figure which shows schematically the internal structure of the outdoor unit 200 of FIG. It is a block diagram which shows the hardware constitutions of the air conditioner in Embodiment 1 of this invention. It is a figure which shows roughly the function structure of the air conditioner in Embodiment 1 of this invention. It is a flowchart for demonstrating the process at the time of the heating operation start which concerns on Embodiment 1 of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

[Basic structure of air conditioner]
An air conditioner disclosed in an embodiment includes a compressor, a four-way (switching) valve, an outdoor heat exchanger, an expansion valve that adjusts a refrigerant flow rate when decompressing, an indoor heat exchanger, and an interior of the indoor heat exchanger It includes parts such as a fan for exchanging heat between the refrigerant and room air. In such an air conditioner, both the heating operation and the cooling operation are possible by switching the four-way valve.

  During heating operation, there is a refrigerant flow path (heating cycle) through which the refrigerant circulates in the order of the compressor, four-way valve, indoor heat exchanger (condenser), expansion valve, outdoor heat exchanger (evaporator), four-way valve, and compressor. Pipe connected to be configured. Thereby, the outdoor heat absorbed by the outdoor heat exchanger is released indoors by the fan in the indoor heat exchanger. On the other hand, during cooling operation, a refrigerant flow path (cooling cycle) in which refrigerant circulates in the order of the compressor, four-way valve, outdoor heat exchanger (condenser), expansion valve, indoor heat exchanger (evaporator), four-way valve, and compressor. ) Is connected to the pipe. Thereby, the heat absorbed by the indoor heat exchanger is released to the outside by the outdoor heat exchanger. In the following description, the heating operation by the heating cycle will be mainly described. In addition, about cooling operation according to a cooling cycle, since well-known control can be implemented, detailed description is not repeated here.

[Embodiment 1]
In the first embodiment, when the air conditioner starts the heating operation described above and the sub-freezing temperature is detected for the outdoor temperature, the following control for preventing the oil level from being cut is performed for the compressor. carry out. Specifically, the air conditioner starts control of the compressor so that a movable part such as a rotor of the compressor moves (rotates) according to the first period when the heating operation starts. Thereafter, immediately before the temperature of the indoor heat exchanger (more specifically, the temperature of the refrigerant in the indoor heat exchanger) rises to the temperature at which the indoor fan starts to rotate, the motion cycle of the movable part is the first. The compressor is controlled to change to a second period longer than the period. Such a change in the motion period of the movable part makes it possible to reduce the amount of low-temperature refrigerant flowing into the compressor 5 while suppressing the generation of friction due to the movement of the movable part in the compressor when the heating operation is started. It is possible to prevent the oil level from running out.

<About refrigerant circuit>
First, the refrigerant circuit in the air conditioner in the present embodiment will be described.

  FIG. 1 is a diagram schematically showing a refrigerant circuit in the air conditioner according to Embodiment 1 of the present invention.

  Referring to FIG. 1, an air conditioner includes an outdoor unit side heat exchanger (hereinafter referred to as “outdoor heat exchanger”) 1, an expansion valve 2, and an indoor unit side heat exchanger (hereinafter referred to as “indoor heat exchange”). 3), a four-way valve 4, and a compressor 5, which are sequentially connected in a closed loop. The compressor 5 has a movable part, and compresses and sends out the refrigerant by repeating the periodic motion of the movable part. The outdoor heat exchanger 1 exchanges heat between outdoor air and refrigerant. The expansion valve 2 is controlled to adjust the flow rate of the refrigerant. The indoor heat exchanger 3 performs heat exchange between the indoor air and the refrigerant in the indoor heat exchanger 3. The four-way valve 4 switches the circulation direction of the refrigerant in the cooling operation and the heating operation. The indoor fan 14 rotates to blow air after heat exchange by the indoor heat exchanger 3 into the room. In Embodiment 1, the compressor 5 has a rotor as a movable part, and compresses and sends out the refrigerant by a periodic rotational motion of the rotor. In addition, the compressor 5 is not limited to the structure using a rotor. For example, the compressor 5 may have a cylinder as a movable portion, and a piston in the cylinder may reciprocate periodically in a linear direction to compress and send out the refrigerant.

  The air conditioner further includes a temperature sensor 6 for measuring the temperature of the outdoor heat exchanger 1 and a temperature sensor 8 for measuring the temperature of the indoor heat exchanger 3. Based on the output of the temperature sensor 6, the temperature of the refrigerant inside the outdoor heat exchanger 1 or the outdoor atmospheric temperature can be measured. Further, the temperature of the refrigerant inside the indoor heat exchanger 3 can be measured based on the output of the temperature sensor 8. These temperature sensors 6, 8 are, for example, thermistors.

  The arrows in FIG. 1 indicate directions in which the refrigerant flows in the heating operation by the heating cycle and the cooling operation by the cooling cycle.

<Appearance and configuration>
(About indoor units)
FIG. 2 is an external view of the indoor unit 100 of the air conditioner according to Embodiment 1 of the present invention. FIG. 3 is a cross-sectional view schematically showing the internal configuration of the indoor unit 100 of FIG.

  Referring to FIG. 3, in addition to indoor heat exchanger 3 and temperature sensor 8 shown in FIG. 1, indoor unit 100 includes a temperature sensor 11 for measuring room temperature, an indoor fan 14, a louver 15, And a louver motor 16. Louver 15 is a wind direction guide member provided at the outlet of indoor unit 100. The louver motor 16 rotationally drives the louver 15. The plurality of louvers 15 are driven to face in the same direction.

(About outdoor unit)
FIG. 4 is an external view of the outdoor unit 200 for an air conditioner according to Embodiment 1 of the present invention. FIG. 5 is a diagram schematically showing the internal configuration of the outdoor unit 200 of FIG.

  Referring to FIG. 5, the outdoor unit 200 includes a temperature for measuring the outdoor temperature in addition to the outdoor heat exchanger 1, the four-way valve 4, the compressor 5, and the temperature sensor 6 illustrated in FIG. 1. A sensor 21 and an outdoor fan 24 are included. The temperature sensors 11 and 21 described above are, for example, thermistors.

(Functional configuration of air conditioner)
FIG. 6 is a block diagram showing a hardware configuration of the air conditioner according to Embodiment 1 of the present invention.

  Referring to FIG. 6, in addition to the configurations shown in FIGS. 1, 3, and 5, the air conditioner includes a stepping motor 12 that is driven to adjust the opening degree of expansion valve 2, and an air conditioner. It further includes a control unit 30 for performing overall control and an operation unit 36 for receiving instructions from the user.

  The control unit 30 is mounted on a circuit board (not shown) built in the indoor unit 100. Control unit 30 includes a processor 32 for performing various arithmetic processes, a timer 33, and a memory 34 for storing various programs and data. The processor 32 is configured by, for example, a CPU (Central Processing Unit). The processor 32 controls each part of the air conditioner by executing a program stored in the memory 34. The memory 34 may be a non-volatile memory such as a flash memory, for example.

  The operation unit 36 includes, for example, a power switch, a temperature adjustment key, an air volume adjustment key, a timer setting key, an operation mode switching key such as heating and cooling.

  FIG. 7 is a diagram schematically showing a functional configuration of the air conditioner according to Embodiment 1 of the present invention. Referring to FIG. 7, the processor 32 includes a compressor control unit 41 for controlling the compressor 5, a fan control unit 42 for controlling the indoor fan 14, and the expansion valve 2 via the stepping motor 12. And a valve control unit 43 for variably controlling the opening degree. The functions of these units are realized by the processor 32 executing a program stored in the memory 34.

  The compressor control unit 41 variably controls the rotation period of the rotor of the compressor 5. Specifically, the compressor 5 incorporates a motor having a rotor. The compressor control unit 41 applies a voltage signal, for example, PWM modulated (pulse width modulated) to the motor. The rotor rotates in synchronization with the period of the voltage signal, and pumps and discharges the refrigerant according to the rotation amount. Therefore, the compressor control unit 41 can change the rotation period (unit: rpm) of the rotor by changing the frequency of the voltage signal, and as a result, can change the discharge amount of the refrigerant. When the compressor 5 is configured to pump the refrigerant by the reciprocating motion of the piston, the refrigerant discharge amount can be changed by variably controlling the cycle of the piston reciprocating motion.

  The fan controller 42 changes the rotation speed (unit: rpm) of the indoor fan 14 by variably adjusting a voltage level applied to a fan motor (not shown) of the indoor fan 14.

  The valve control unit 43 variably adjusts the opening degree of the expansion valve 2 according to the number of phase excitation steps in the stepping motor 12. The expansion valve 2 is not limited to the one whose opening degree is adjusted by the stepping motor 12, and other methods may be used.

(Compressor control in heating operation)
FIG. 8 is a flowchart for explaining processing at the start of heating operation according to Embodiment 1 of the present invention. A program according to this flowchart is stored in the memory 34. The processor 32 reads a program from the memory and executes processing according to the read program. The process of FIG. 8 is performed when the outside air temperature at the start of the heating operation is a low temperature of minus 10 ° C. or less (a low temperature of 10 ° C. or less below freezing point). In other cases, processing at the time of starting normal heating operation is performed. Since this normal heating operation start process is a well-known process, description thereof will not be repeated here.

  Referring to FIG. 8, first, when a user operates a heating operation switch (not shown) of operation unit 36, processor 32 is based on outputs from operation unit 36 and based on outputs from temperature sensors 8 and 6. Then, measurement of the room temperature and the outside air temperature is started (step S1). The outside air temperature may be measured by the temperature sensor 21.

  Further, the compressor control unit 41 of the processor 32 activates the compressor 5. Specifically, the compressor control unit 41 starts control of the compressor 5 so that the rotor rotates according to, for example, 3000 rpm or more and 5000 rpm or less (corresponding to the first cycle) (step S3). Due to the rotation of the compressor 5, the refrigerant in the air conditioner starts to circulate according to the heating cycle, and the temperature of the indoor heat exchanger 3 starts to rise.

  Thereafter, the processor 32 determines whether or not the temperature of the indoor heat exchanger 3 has reached a predetermined temperature based on the output of the temperature sensor 8 (step S5).

  The predetermined temperature is a temperature immediately before the temperature of the indoor heat exchanger 3 for starting rotation of the indoor fan 14 for heating after starting the compressor 5 (hereinafter also referred to as fan rotation start temperature) (for example, Corresponds to a temperature lower by 1 ° C. than the fan rotation start temperature).

  While the processor 32 determines that the temperature of the indoor heat exchanger 3 has not yet risen to the predetermined temperature (the temperature just before the above) (NO in step S5), the refrigerant follows the heating cycle. , The process of step S5 is repeated.

  On the other hand, when it is determined that the temperature of the indoor heat exchanger 3 has reached the predetermined temperature (the immediately preceding temperature) (YES in step S5), the compressor control unit 41 determines that the rotational speed of the rotor is The compressor 5 is controlled so as to decrease to a predetermined rotational speed (step S9). Therefore, in step S9, the compressor control unit 41 controls the compressor 5 so that the rotational speed of the rotor changes to the rotational speed according to the second period longer than the first period. The rotation speed of the second period is the minimum rotation speed determined from the specifications during the heating operation, and is the rotation speed for the compressor 5 to operate stably. The rotation speed according to the second cycle is, for example, approximately 1500 rpm.

  Subsequently, the processor 32 determines whether the temperature of the indoor heat exchanger 3 has reached the fan rotation start temperature described above based on the output of the temperature sensor 8 (step S11). While it is not determined that the temperature of the indoor heat exchanger 3 is equal to or higher than the fan rotation start temperature (NO in step S11), the process of step S11 is repeated.

  On the other hand, when it is determined that the temperature of the indoor heat exchanger 3 has reached the fan rotation start temperature (YES in step S11), the fan control unit 42 activates the indoor fan 14 (step S13). As a result, the indoor fan 14 rotates in accordance with a predetermined number of rotations for heating operation, and warm air is sent out indoors.

  Thereafter, normal heating operation is performed. Specifically, the compressor control unit 41 controls the compressor 5 so that the rotation period of the rotor changes from the second period to the third period corresponding to the set temperature. The rotational speed of the rotor according to the third period is higher than the rotational speed (1500 rpm) of the second period. In addition, since normal heating operation is based on well-known operation control, description is not repeated.

  According to the processing of the above flow chart, since the outside air temperature is low and below the freezing point, the lubricating oil of the compressor 5 is cooled to increase the viscosity, and even if the lubricating effect is not obtained, the compressor 5 is out of oil level. Reliability degradation can be prevented. Specifically, the compressor control unit 41 reduces the rotational speed of the rotor of the compressor 5 when the temperature of the indoor heat exchanger 3 rises to a temperature just before the fan rotation start temperature (YES in step S5). (Step S9). Thereby, generation | occurrence | production of the friction by rotor rotation is suppressed, and it becomes possible to reduce the inflow amount of the low-temperature refrigerant | coolant to the compressor 5, and can prevent oil level cut.

  Further, in step S9, since the rotational speed of the rotor of the compressor 5 is lowered, the refrigerant circulation amount decreases, but the decrease in the rotational speed is caused by the temperature of the indoor heat exchanger 3 being changed from the immediately preceding temperature. It is limited to the implementation while rising to the fan rotation start temperature. Therefore, the refrigerant circulation amount is temporarily reduced and the influence on the temperature rise of the indoor heat exchanger 3 is extremely small. Therefore, the start of warm air blowing into the room is not delayed.

[Embodiment 2]
In the second embodiment, a modification of the first embodiment will be described. In the second embodiment, in order to prevent the oil level from running out, the indoor fan 14 is continuously rotated during the period in which the compressor 5 before the heating operation is stopped (hereinafter also referred to as compressor stagnation). Keep it. Thereby, heat exchange is implemented between the refrigerant | coolant inside the indoor heat exchanger 3, and indoor air by rotation of the indoor fan 14, and the temperature of the refrigerant | coolant in the indoor heat exchanger 3 can be raised. Therefore, it is possible to prevent the low-temperature refrigerant from flowing into the compressor 5 at the start of the subsequent heating operation. As a result, the oil level cut in the compressor 5 can be prevented.

  The period when the compressor lies down is preferably, for example, a period of 6 hours or more. For example, when the start of the heating operation is set by timer reservation, the processor 32 detects six hours before the reserved start time based on the output of the timer 33. When six hours ago is detected, the fan control unit 42 controls the indoor fan 14 to rotate. The processor 32 controls the air conditioner so that the normal heating operation is started or the heating operation of FIG. 8 is started after the lapse of 6 hours.

  Here, the fan control unit 42 controls the indoor fan 14 to rotate according to the number of rotations based on the set temperature for heating during the heating operation period. On the other hand, when the compressor lies down, the fan control unit 42 controls the indoor fan 14 so that the number of rotations is lower than the number of rotations based on the set temperature. The low rotation speed is approximately 500 rpm, for example.

  Further, when the indoor fan 14 rotates when the compressor lies down, the louver 15 is set so as to face a direction in which no wind is directly applied to a person in the room, for example, a ceiling direction in the room. This prevents cold air from directly hitting a person in the room when the compressor lies down.

[Embodiment 3]
In the third embodiment, a modification of each of the above embodiments will be described. In the third embodiment, the opening degree of the expansion valve 2 during the period from when the heating operation described above is started (the compressor 5 is started) until the temperature of the indoor heat exchanger 3 reaches the fan rotation start temperature. Limit. Thereby, the circulation amount of the refrigerant | coolant at the time of heating operation start can be decreased, and the inflow amount of the low-temperature refrigerant | coolant to the compressor 5 can be reduced. As a result, the oil level cut in the compressor 5 can be prevented.

  Specifically, during the period from the start of the heating operation (starting of the compressor 5) to the detection of the fan rotation start temperature, the valve control unit 43 has a refrigerant flow rate circulating in the air conditioner because the heating operation is performed. The opening degree of the expansion valve 2 is controlled so as to be less than the predetermined normal flow rate. Specifically, the valve control unit 43 controls the expansion valve 2 in the closing direction so that the refrigerant flow rate is, for example, 10% or less of the normal flow rate. When the temperature of the indoor heat exchanger 3 reaches the fan rotation start temperature, the valve control unit 43 controls the expansion valve 2 so as to return to the normal opening for the heating operation.

  Thus, at the start of the heating operation, the flow rate of the low-temperature refrigerant can be reduced to prevent the oil level of the compressor 5 from running out, and a sufficient amount of refrigerant can be circulated for the subsequent normal heating operation.

[Embodiment 4]
In the fourth embodiment, a modification of each of the above embodiments will be described. In the fourth embodiment, after the heating operation described above is started (the compressor 5 is started), the temperature of the indoor heat exchanger 3 reaches the fan rotation start temperature. The refrigerant flow rate in the heating cycle is decreased by increasing the rotation period (that is, decreasing the rotation speed). Thereby, the inflow amount of the low-temperature refrigerant to the compressor 5 at the start of the heating operation can be reduced, and the oil level can be prevented from running out.

  Specifically, when the outdoor temperature is below freezing when starting the heating operation, the processor 32 starts control of the compressor so that the rotor rotates at a low rotation speed according to a predetermined long cycle, and thereafter When the temperature sensor 8 detects the fan rotation start temperature, the rotation cycle of the rotor is changed. That is, the processor 32 performs compression so that the rotation period of the rotor changes from the predetermined long period to a period (high rotation number) corresponding to the set temperature for the heating operation shorter than the period. The machine 5 is controlled. Note that the predetermined long cycle corresponds to, for example, the second cycle (approximately 1500 rpm) described in the first embodiment.

  In the fourth embodiment, whether or not to perform the control for increasing the rotation period of the rotor of the compressor 5 described above may be determined based on the room temperature.

  That is, when the indoor temperature detected by the temperature sensor 8 is high even when the outdoor temperature is below freezing when starting the heating operation, the compressor 5 has a relatively warm refrigerant from the indoor heat exchanger 3 side. Since oil flows in, it is possible to avoid running out of oil. Therefore, in the fourth embodiment, when starting the heating operation, the processor 32 detects a relatively high indoor temperature (for example, 10 ° C. or higher) even if the outdoor temperature is a sub-freezing temperature. Controls the compressor 5 so that the rotor rotates at a speed according to a normal cycle (such as the first cycle of the first embodiment).

  On the other hand, when the outdoor temperature is below freezing and the indoor temperature is detected to be relatively low (for example, less than 10 ° C.), the processor 32 determines that the rotor has a predetermined long cycle (substantially). The compressor 5 is controlled to rotate at a speed according to 1500 rpm.

  Thereafter, in any case, when the processor 32 detects the fan rotation start temperature based on the output of the temperature sensor 8, the rotation period of the rotor is determined according to the set temperature of the heating from the predetermined period. The compressor 5 is controlled so as to change in the cycle.

  Each of the embodiments described above discloses a configuration for preventing the oil level of the compressor 5 from being cut, and these may be implemented individually or in combination of two or more. May be.

[Configuration of the embodiment]
The configuration of the air conditioner disclosed in each of the above embodiments will be described.

  (1) The air conditioner has a movable part (such as a rotor), and exchanges heat between the compressor 5 for compressing the refrigerant by periodically moving (rotating) the movable part, and outdoor air and the refrigerant. An outdoor heat exchanger 1 for performing heat exchange, an indoor heat exchanger 3 for exchanging heat between indoor air and refrigerant, and an indoor fan 14 for blowing air after heat exchange by the indoor heat exchanger into the room And a temperature sensor 6 that detects the outdoor temperature, a temperature sensor 8 that detects the temperature of the indoor heat exchanger 3, and a control unit 30 that controls the air conditioner.

  The control unit 30 includes a compressor control unit 41 for controlling the compressor 5. When the temperature sensor 6 detects the outdoor temperature below the freezing point when the refrigerant starts circulating heating through the compressor 5, the indoor heat exchanger 3, and the outdoor heat exchanger 1, the compressor control is performed. The unit 41 starts control of the compressor 5 so that the movable unit moves according to a first period (for example, 3000 rpm or more and 5000 rpm or less). Thereafter, when the temperature sensor 8 detects a temperature lower than a fan rotation start temperature for starting the rotation of the indoor fan 14 for heating (for example, a temperature lower by −1 ° C.), the movable part. The compressor 5 is controlled so that the motion period of the second period changes to a second period (for example, approximately 1500 rpm) longer than the first period.

  Accordingly, when the outside air temperature is low below freezing point, the lubricating oil of the compressor 5 is cooled and the viscosity becomes high, and there is a possibility that the sufficient lubricating effect is not achieved. When the temperature of the compressor 3 rises to a temperature just before the fan rotation start temperature, the compressor 5 is controlled so that the rotational speed of the compressor 5 becomes low. As a result, it is possible to suppress the generation of friction in the compressor 5 due to the periodic movement of the movable part, and to reduce the amount of low-temperature refrigerant flowing into the compressor 5. As a result, the oil level cut of the compressor 5 can be prevented.

  Further, when the indoor temperature sensor 8 detects the fan rotation start temperature after the motion cycle of the movable portion has changed to the second cycle, the compressor control unit 41 determines that the motion cycle of the movable portion is the first cycle. The compressor 5 is controlled so that it changes from 2 periods to the 3rd period (3rd period is shorter than 2nd period) according to the preset temperature of heating.

  Thus, the period during which the movable part moves in the second period can be limited to the period in which the temperature measured by the indoor temperature sensor 8 rises from the immediately preceding temperature to the fan rotation start temperature. Therefore, the refrigerant circulation amount is temporarily reduced, and the influence on the temperature rise of the indoor heat exchanger 3 can be reduced.

  (2) The air conditioner rotates only the indoor fan 14 while the compressor 5 is stopped when the compressor is sleeping. Specifically, the control unit 30 includes a fan control unit 42 for controlling the indoor fan 14. The compressor control unit 41 stops the compressor 5 during a predetermined period (when the compressor lies down). On the other hand, the fan control unit 42 controls the indoor fan 14 to rotate during the predetermined period. The control unit 30 controls the air conditioner so as to start the heating operation after the predetermined period has elapsed.

  (3) The number of rotations of the indoor fan 14 when the compressor is sleeping is low. Specifically, the fan control part 42 controls the indoor fan 14 according to the rotation speed based on the preset temperature for heating during the heating operation period. On the other hand, the indoor fan 14 is controlled so that the number of rotations is lower than the number of rotations based on the above-described set temperature during the above-described predetermined period (when the compressor lies down) prior to the heating operation.

  According to the above configurations (2) and (3), prior to the start of the heating operation, the temperature of the refrigerant inside the indoor heat exchanger 3 is raised by heat exchange with the indoor air accompanying the rotation of the indoor fan 14. I can keep it. Therefore, it is possible to prevent the low-temperature refrigerant from flowing from the indoor heat exchanger 3 into the compressor 5 at the start of the subsequent heating operation, and to prevent the oil level from running out.

  (4) When the air conditioner starts the heating operation at an outdoor temperature below the freezing point, it reduces the circulating refrigerant flow rate.

  Specifically, the air conditioner further includes an expansion valve 2 for adjusting the circulating refrigerant flow rate, and the control unit 30 includes a valve control unit 43 for controlling the expansion valve 2. During the period from when the compressor control unit 41 starts controlling the compressor 5 until the indoor fan 14 starts to rotate at the start of the heating operation, the valve control unit 43 sets the refrigerant flow rate to a normal value for the heating operation. The opening degree of the expansion valve 2 is controlled so as to be smaller than the flow rate. Thereby, the inflow amount of the low-temperature refrigerant | coolant to the compressor 5 at the time of heating operation start can be reduced, and oil level cut | off can be prevented.

  (5) When starting the heating operation at an outdoor temperature below freezing, the compressor 5 is started at a low rotation.

  Specifically, in the air conditioner, when the heating operation is started and the outdoor temperature below the freezing point is detected by the temperature sensor 6, the control unit 30 sets the movable unit to a predetermined cycle (for example, approximately When the compressor 5 starts to move in accordance with 1500 rpm), and the indoor temperature sensor 8 detects the fan rotation start temperature, the moving period of the movable part starts from the predetermined period. The compressor 5 is controlled so as to change to a shorter cycle according to the set temperature of operation.

  Thereby, the friction accompanying the periodic motion of the movable part in the compressor 5 is reduced by reducing the motion period of the movable part of the compressor 5 to a predetermined period (approximately 1500 rpm described above) at the start of the heating operation. Is suppressed, and the amount of low-temperature refrigerant flowing into the compressor 5 itself is reduced. As a result, the oil level can be prevented from being cut.

  (6) The low rotation control of the compressor 5 described in the above (5) is performed according to the room temperature and the outside air temperature. Specifically, when the heating operation is started, the control unit 30 detects a relatively high indoor temperature set in advance by the temperature sensor 8 even if the outdoor temperature below freezing is detected by the temperature sensor 6. If this happens, the compressor rotation control (5) is passed. On the other hand, when the temperature sensor 8 detects a temperature lower than the predetermined indoor temperature, the low rotation control of the compressor 5 described in the above (5) is performed.

  Thereby, even when the outdoor temperature is below freezing point, when it is determined that there is no possibility of running out of oil based on the indoor temperature, the motion cycle of the movable part of the compressor 5 at the start of the heating operation should not be reduced. Thus, it is possible to quickly perform the heating operation.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Outdoor heat exchanger, 2 Expansion valve, 3 Indoor heat exchanger, 4 Four way valve, 5 Compressor, 6, 8, 11, 21 Temperature sensor, 14 Indoor fan, 30 Control part, 32 Processor, 41 Compressor control part , 42 Fan control unit, 43 Valve control unit, 100 indoor unit, 200 outdoor unit.

Claims (4)

An air conditioner,
A compressor having a movable part, and compressing the refrigerant by periodically moving the movable part;
An outdoor heat exchanger for exchanging heat between outdoor air and the refrigerant;
An indoor heat exchanger for exchanging heat between indoor air and the refrigerant;
A fan for blowing air into the room after heat exchange by the indoor heat exchanger;
An outdoor temperature sensor for detecting the outdoor temperature;
An indoor temperature sensor for detecting the temperature of the indoor heat exchanger;
A control unit for controlling the air conditioner,
The control unit includes a compressor control unit for controlling the compressor,
In the case where a heating operation is started in which the refrigerant circulates in order through the compressor, the indoor heat exchanger, and the outdoor heat exchanger, the compression is performed when a temperature below freezing point is detected by the outdoor temperature sensor. The machine controller
Control of the compressor is started so that the movable part moves according to the first period, and then a temperature lower than a temperature for starting rotation of the fan is detected by the indoor temperature sensor. An air conditioner that controls the compressor so that the period of motion of the movable part changes from the first period to a second period that is longer than the first period. The control unit further includes a fan control unit for controlling the fan,
The compressor control unit controls the compressor to stop for a predetermined period;
The fan control unit controls the fan to rotate for the predetermined period;
The air conditioner according to claim 1, wherein the control unit controls the air conditioner to start the heating operation after the predetermined period has elapsed. An expansion valve for adjusting the flow rate of the refrigerant,
The control unit includes a valve control unit for controlling the expansion valve,
In a period from when the compressor control unit starts controlling the compressor to when the fan starts rotating, the valve control unit is configured such that the flow rate of the refrigerant is higher than the flow rate for the heating operation. The air conditioner according to claim 1 or 2, wherein the opening degree of the expansion valve is controlled so as to be reduced. A control method for an air conditioner, comprising:
The air conditioner
A compressor having a movable part, and compressing the refrigerant by periodically moving the movable part;
An outdoor heat exchanger for exchanging heat between outdoor air and the refrigerant;
An indoor heat exchanger for exchanging heat between indoor air and the refrigerant;
A fan for blowing air into the room after heat exchange by the indoor heat exchanger;
An outdoor temperature sensor for detecting the outdoor temperature;
An indoor temperature sensor for detecting the temperature of the indoor heat exchanger,
The control method is:
When a temperature below freezing point is detected by the outdoor temperature sensor when the refrigerant starts a heating operation that circulates through the compressor, the indoor heat exchanger, and the outdoor heat exchanger in order,
Starting control of the compressor such that the movable part moves according to a first period;
When the indoor temperature sensor detects a temperature that is lower than a temperature for starting rotation of the fan, the period of movement of the movable part is longer than the first period from the first period. And controlling the compressor so as to change to the second period.

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