JP2014126309A - Air conditioner - Google Patents

Abstract

[PROBLEMS] To suppress the occurrence of a refrigerant stagnation phenomenon without unnecessarily warming a compressor.
An outdoor unit includes a heat exchanger for exchanging heat between a refrigerant and outside air, a compressor for compressing the refrigerant, a heater for heating the compressor, and detecting an outside air temperature. An outside air temperature detector and a control device. When the operation of the compressor is stopped, the control device switches heating control using the heater in multiple stages based on the outside air temperature detected by the outside air temperature detector. When the outside air temperature Ta is higher than the first outside air temperature α, the heater control A is executed. When the outside air temperature Ta is not less than the second outside air temperature β and not more than the first outside air temperature α, the heater control B is executed. When the outside air temperature Ta is lower than β, the heater control C is executed.
[Selection] Figure 3

Description

  The present invention relates to an air conditioner.

  There is known a phenomenon (so-called refrigerant stagnation phenomenon) in which, after the compressor is stopped, the refrigerant collects and condenses in the casing of the compressor having a lowered temperature and is dissolved in the refrigerating machine oil in the casing. When the refrigerant stagnation occurs, the pressure of the refrigerating machine oil rises when the compressor is restarted, so that the refrigerant dissolved in the refrigerating machine oil evaporates and a severe foaming phenomenon (forming) occurs. When a foaming phenomenon occurs in the refrigerating machine oil, the viscosity of the refrigerating machine oil decreases according to the amount of foam, so that insufficient lubrication may occur in each part of the compressor and the compressor may be damaged.

  Therefore, in one conventional technique (Patent Document 1), the outside air temperature is equal to or lower than a first set temperature at which the refrigerant may stagnate in the compressor while the compressor is stopped, and the radiator temperature detector When the detected radiator temperature is equal to or lower than a second set temperature at which it can be assumed that the inverter is not driven, restraint energization is performed on the compressor driving motor winding. Thereby, in this prior art, the temperature of the compressor is maintained to such an extent that the refrigerant stagnation phenomenon does not occur.

  In another prior art (Patent Document 2), when the compressor is stopped and the outdoor unit control unit is in the sleep state, when the air conditioner is set to the rapid heating operation mode, the temperature of the compressor is first. When the temperature is below the compressor temperature, the sleep state of the outdoor unit control unit is canceled, and control is performed in the compressor preheating mode. Thereby, in other prior art, standby power is reduced.

JP 2000-292014 A JP 2011-237110 A

  In the prior art, since the heater is always energized, the compressor may be heated more than necessary, resulting in an increase in power consumption. Further, since the heat capacities of the compressors are variously different, the compressor cannot be appropriately heated unless a heater suitable for the heat capacity of the compressor is used, and electric power is wasted.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an air conditioner capable of appropriately controlling the temperature of the compressor after the operation of the compressor is stopped.

  In order to solve the above problems, an air conditioner according to the present invention is an air conditioner in which an indoor unit and an outdoor unit are connected via a pipe and circulates a refrigerant. The outdoor unit exchanges heat between the refrigerant and the outside air. A heat exchanger for compressing the refrigerant, a compressor for compressing the refrigerant, a heater for heating the compressor, an outside air temperature detector for detecting the outside air temperature, and a control device. The control device is characterized in that, when the operation of the compressor is stopped, the heating control using the heater is switched in multiple stages based on the outside air temperature detected by the outside air temperature detector.

  According to the present invention, since heating control using a heater can be switched in multiple stages based on the outside air temperature, it is possible to suppress wasteful heating and reduce power consumption. .

It is a block diagram of an air conditioner. It is a flowchart which shows the control which heats the crankcase of a compressor. It is a state transition diagram for performing ON / OFF determination of a heater. It is a graph which shows the relationship between outside temperature and compressor temperature. It is a graph which shows a mode that the temperature of a compressor is maintained by turning on and off a heater by time proportional operation.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present embodiment, as described in detail below, the heater is controlled so as not to heat the compressor unnecessarily.

  Here, when the compressor is started from a state where the compressor has been stopped for a long time, the inventors of the present invention ensure a superheat under the compressor (temperature difference between the refrigerator oil temperature and the saturated steam temperature) of 10 deg or more. If so, it was confirmed by experiments under various outside air temperature conditions that the refrigerant stagnation phenomenon does not occur.

  Therefore, in this embodiment, as will be described later, the heater control is switched according to the outside air temperature, and the heater for heating the crankcase is controlled on and off. Thereby, in this embodiment, generation | occurrence | production of the stagnation phenomenon of a refrigerant | coolant can be effectively suppressed with less power consumption.

  Moreover, in this embodiment, the time (on time) which energizes a heater by using the thermistor for detecting the outside temperature currently used in the air conditioner, and the thermistor for detecting the temperature of a compressor is used. Can be reduced. By appropriately setting the ratio of turning on / off the energization time of the heater according to the heat capacity of the compressor, it is possible to deal with compressors having various heat capacities.

  Instead of the method of controlling the energization time of the heater by a time proportional operation, a method may be used in which the heater is composed of a plurality of independent heating wires and only a predetermined number of heating wires are energized. The amount of heat generated by the heater can be adjusted by increasing or decreasing the number of heating wires to be energized. Furthermore, you may combine the structure which adjusts the number of the heating wires to be used among several heating wires, and the structure which adjusts the electricity supply time to the heating wire to be used by time proportional operation.

A first embodiment will be described with reference to FIGS.
FIG. 1 is a configuration example of a refrigeration cycle of an air conditioner according to the present embodiment. The air conditioner includes an outdoor unit 1 and an indoor unit 2, and the outdoor unit 1 and the indoor unit 2 are connected via local refrigerant pipes 3 and 4.

  The outdoor unit 1 includes a control device 10, a compressor 11, an outdoor unit heat exchanger 12, an outdoor unit expansion valve 13, a four-way valve 14, an accumulator 15, another accumulator 16, and a compressor temperature sensor 17. And an outside air temperature sensor 18 and a crankcase heater 19. The indoor unit 2 includes an indoor unit heat exchanger 21 and an indoor unit expansion valve 22.

  The control device 10 is configured as a computer device including a microprocessor and a memory, for example, and controls the operation of the outdoor unit 1 according to a computer program stored in advance. The control device 10 also executes heater control described later.

  The compressor 11 compresses the refrigerant and discharges it to the piping. The outdoor unit heat exchanger 12 exchanges heat between the refrigerant and the outside air. By switching the four-way valve 14, the flow of the refrigerant changes, and the cooling operation and the heating operation are switched. During the cooling operation, the outdoor unit heat exchanger 12 serves as a condenser, and the indoor unit heat exchanger 21 serves as an evaporator. During the heating operation, the outdoor unit heat exchanger 12 serves as an evaporator, and the indoor unit heat exchanger 21 serves as a condenser. The accumulators 15 and 16 store liquid refrigerant from the gas-liquid mixed refrigerant, and send the gaseous refrigerant to the compressor 11.

  The compressor temperature sensor 17 is a sensor for detecting the temperature of the compressor 11 and includes a temperature detection element such as a thermistor. The compressor temperature sensor 17 is attached to the upper part (for example, the top part) of the compressor 11 and outputs an electric signal indicating the temperature of the compressor 11 to the control device 10.

  The outside temperature sensor 18 is a sensor for detecting the outside temperature, and is an example of an “outside temperature detector”. The outside air temperature sensor 18 includes a temperature detection element such as a thermistor, for example, and outputs an electric signal indicating the outside air temperature to the control device 10.

  The compressor 11 includes a compressor body (not shown) and a crankcase 11A as a sealed container that houses the compressor body. Refrigerating machine oil is always stored below the crankcase 11A so as not to run out of refrigerating machine oil and insufficient lubrication. The compressor main body has a pump function, and sucks the refrigeration oil accumulated in the crankcase 11A and supplies it to predetermined parts. The refrigerating machine oil that has lubricated predetermined portions again accumulates below the crankcase 11A. Thus, when the air conditioner is in operation (when the compressor 11 is in operation), the refrigerating machine oil circulates in the compressor 11.

  When the operation of the air conditioner is stopped (when the operation of the compressor 11 is stopped), the refrigerating machine oil is accumulated below the compressor 11. When the refrigerant gathers in the compressor 11 due to a temperature drop and a pressure drop due to the stop of the operation of the compressor 11, a refrigerant stagnation phenomenon occurs in which the refrigerant melts into the refrigerating machine oil stored under the crankcase 11A. There is a fear. Therefore, a crankcase heater (hereinafter referred to as a heater) 19 is provided below the compressor 11 to warm the refrigeration oil so that the refrigerant does not melt.

  The heater 19 is an example of a “heater” and includes, for example, one or more heating wires such as a nichrome wire. The heater 19 is energized by the control device 10. In normal cases, the main power of the air conditioner is always on during the cooling and heating periods. In the prior art, since the compressor 19 is heated by energizing the heater 19 while the original power source of the air conditioner is on, power is consumed even after the operation is stopped, and energy is wasted. In the present embodiment, as will be described later, the control of the heater 19 is switched in multiple steps according to the outside air temperature in order to reduce this energy waste as much as possible.

  FIG. 2 is a flowchart showing a process for switching the heating control using the heater 19 based on the outside air temperature after the operation of the compressor 11 is stopped. This process is executed by the control device 10. In this embodiment, a case where three different controls A to C are switched will be described. However, the present invention is not limited to this, and a configuration in which four or more different controls are switched may be used.

  When detecting that the operation of the compressor 11 has stopped, the control device 10 detects the outside air temperature Ta based on the signal from the outside air temperature sensor 18 (S1). The control device 10 determines whether or not the outside air temperature Ta is higher than a predetermined first outside air temperature α (S2).

  When it is determined that the outside air temperature Ta is higher than the first outside air temperature α (S2: YES), the control device 10 performs heater control A as “first control” described later (S3).

  When it is determined that the outside air temperature Ta is equal to or lower than the first outside air temperature α (S2: NO), the control device 10 has the predetermined outside air temperature Ta equal to or lower than the first outside air temperature α and set in advance. 2. It is determined whether or not the outside air temperature β is higher than β (β <α) (S4). When it is determined that the outside air temperature Ta is equal to or lower than the first outside air temperature α and equal to or higher than the second outside air temperature β (S4: YES), the control device 10 performs heater control B as “second control” described later. Execute.

  When it is determined that the outside air temperature Ta is lower than the second outside air temperature β (S4: NO), the control device 10 performs heater control C as “third control” described later.

  When the compressor 11 is stopped, the optimum heater control can be selected and shifted by periodically repeating the process shown in FIG.

  The first outside air temperature α and the second outside air temperature β are different for each heat capacity of the compressor 11. For example, the first outside air temperature α is set to about 10 ° C., and the second outside air temperature β is set to about 0 ° C. May be. Further, even when the heat capacities of the compressors 11 are the same, the values of the first outside air temperature α and the second outside air temperature β may be appropriately changed according to, for example, the use environment of the air conditioner.

  FIG. 3 is a state transition diagram of each heater control. The heater controls A, B, and C will be described using the state transition diagram of FIG.

  As described above, the heater control A shown in FIG. 3A is selected when the outside air temperature Ta exceeds the first outside air temperature α. When the compressor temperature Td detected by the compressor temperature sensor 17 falls below a predetermined lower limit temperature (Ta + T1), the control device 10 energizes the heater 19 to cause the heater 19 to generate heat. In the present embodiment, energizing the heater 19 is referred to as heater on, and stopping energizing the heater 19 is referred to as heater off. Here, the temperature T1 may be set to about 25 ° C., for example.

  Then, the control device 10 turns off the heater 19 when the compressor temperature Td rises to a predetermined upper limit temperature (Ta + T2). Here, the temperature T2 may be set to about 30 ° C., for example. The difference between the temperature at which the heater 19 is energized (heater on temperature (= Ta + T1)) and the temperature at which the heater 19 is deenergized (heater off temperature (Ta + T2)) is a phenomenon in which the heater on and the heater off are frequently switched. This is to suppress the occurrence of (chattering phenomenon). This is because when the chattering phenomenon occurs, the life of the switching element for controlling energization may be shortened. The magnitude of the hysteresis can be changed as appropriate.

  The heater control B shown in FIG. 3B is selected when the outside air temperature Ta is not more than the first outside air temperature α and not less than the second outside air temperature β (β <α). When the compressor temperature Td detected by the compressor temperature sensor 17 falls below a predetermined lower limit temperature (Ta + T2), the control device 10 energizes the heater 19. When the compressor temperature Td rises to a predetermined upper limit temperature (Ta + T3), the control device 10 stops energizing the heater 19. Here, the temperature T3 may be set to about 35 ° C., for example (T3> T2> T1).

  That is, when the outside air temperature Ta is not less than β ° C. and not more than α ° C., the temperature is lower than when the condition of the heater control A is satisfied, so that the refrigerant is likely to stagnate in the refrigerating machine oil. Therefore, it is necessary to make the outside air temperature condition for turning on the heater 19 stricter than in the case of the heater control A. Therefore, as described above, the heater 19 is turned on when the compressor temperature Td falls below the outside air temperature (Ta + T3), and the heater 19 is turned off when Td rises to Ta + 35 ° C.

  Here, in the heater control B, in order to shorten the ON time (energization time) of the heater 19 as much as possible, a time proportional operation is performed in which the current value supplied to the heater 19 is turned on for a predetermined time every control cycle. That is, the control apparatus 10 makes the energization time intermittent at a ratio corresponding to the deviation between the target temperature of the compressor temperature Td and the current temperature for each predetermined control cycle. For example, when the control cycle is 10 seconds, the current is supplied for 6 seconds and the remaining 4 seconds are not supplied. Thus, if the heater 19 is intermittently operated by a time proportional operation, about 10 deg of superheat under the compressor at the time of starting the compressor can be secured.

  The optimum value of the on / off time during intermittent operation varies depending on the heat capacity of the compressor 11. Therefore, for example, a plurality of types of on / off times may be stored in advance as the constant C in the memory 101 of the control device 10 and used according to the model of the compressor 11.

  The heater control C shown in FIG. 3C is selected when the outside air temperature Ta is lower than the second outside air temperature β as described above. When the outside air temperature Ta is lower than β, if the heater 19 is always turned on and the compressor 11 is not warmed, the superheat below the compressor will be reduced. Therefore, the control device 10 turns on the heater 19 when the compressor temperature Td falls below the lower limit temperature T4 (for example, about 75 ° C.), and the compressor temperature Td rises to the upper limit temperature T5 (for example, about 80 ° C.). In this case, the heater 19 is turned off.

  FIG. 4 is a graph schematically showing power consumption that can be reduced by the present embodiment. In the prior art, regardless of the outside air temperature, the heater 19 is always turned on when the compressor thermistor temperature is T5 or less.

  In contrast, in this embodiment, the heater 19 is turned on in the heater control C as in the conventional case, but the heater 19 is turned on and off intermittently in the heater control B. Further, in the heater control A, the target set temperature is set to a lower value. Therefore, in the present embodiment, since the heater 19 can be turned off at the hatched portion in FIG. 4, power consumption can be reduced accordingly.

  FIG. 5 is a diagram for explaining intermittent operation of the heater 19 in the heater control B. The horizontal axis of each graph shows time. The vertical axis indicates the compressor superheat, the heater on / off state, and the compressor temperature Td in order from the upper side of FIG.

  According to the graph shown in the lower side of FIG. 5, when the compressor 11 stops when the outside air temperature Ta is not less than the second outside air temperature β and not more than the first outside air temperature α, the compressor temperature Td gradually increases from X1 ° C. at the time of stop. When the temperature decreases to the outside air temperature Ta + 30 ° C., the heater-on condition is satisfied.

  In FIG. 5, TON represents the heater on time, and TOFF represents the heater off time. The controller 10 repeats turning on and off the heater 19 until the heater off condition is established after the heater on condition is established. TON and TOFF are numerical values that are arbitrarily changed according to the heat capacity of the compressor 11 and the like. Note that if the ON / OFF time of the heater 19 is too short, the contact life of the relay may be exceeded, so it is necessary to set the interval at which the compressor temperature Td is kept constant.

  According to this embodiment configured as described above, the compressor temperature Td is stabilized at the outside air temperature Ta + 30 ° C. or so. Therefore, the compressor 11 can be saved without being excessively heated, and the superheat under the compressor can be secured by 10 degrees or more. As a result, it is possible to suppress the occurrence of the stagnation phenomenon in which the refrigerant is dissolved in the refrigerating machine oil.

  In the present embodiment, the target set temperature for heater control and the on / off time of the intermittent operation can be appropriately changed according to the heat capacity of the compressor 11, so that it is possible to cope with a plurality of types of compressors.

  In addition, this invention is not limited to the Example mentioned above. A person skilled in the art can make various additions and changes within the scope of the present invention.

  1: outdoor unit, 2: indoor unit, 10: control device, 11: compressor, 12: outdoor unit heat exchanger, 17: compressor temperature sensor, 18: outside air temperature sensor, 19: crankcase heater, 21: indoor Machine heat exchanger

Claims (5)

In an air conditioner that connects an indoor unit and an outdoor unit via a pipe and circulates a refrigerant,
The outdoor unit is
A heat exchanger for exchanging heat between the refrigerant and the outside air, a compressor for compressing the refrigerant, a heater for heating the compressor, and an outside air temperature detector for detecting the outside air temperature And a control device,
The control device switches the heating control using the heater in multiple stages based on the outside air temperature detected by the outside air temperature detector when the operation of the compressor is stopped. Machine. The control device has a plurality of predetermined heating controls that are set to different target temperatures, as the heating control,
The plurality of predetermined heating controls include at least one control capable of adjusting the amount of heat generated by the heater.
The air conditioner according to claim 1. In the plurality of predetermined heating controls, a continuous energization operation for continuously energizing and heating the heater, and a time proportional expression for turning on a current value to energize the heater for a predetermined time every control cycle Behavior and include,
The air conditioner according to claim 2. As the plurality of predetermined heating controls, a first control, a second control, and a third control are prepared in advance,
The control device includes:
When the outside air temperature detected by the outside air temperature detector is higher than a predetermined first outside air temperature, the first control is executed.
When the outside air temperature detected by the outside air temperature detector is equal to or lower than the first outside air temperature and equal to or higher than a predetermined second outside air temperature (second outside air temperature <first outside air temperature). Executing the second control;
Executing the third control when the outside air temperature detected by the outside air temperature detector is lower than the second outside air temperature;
The air conditioner according to claim 3. The second control executes the time proportional operation, and the first control and the third control execute the continuous energization operation.
The air conditioner according to claim 4.

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