JP2008275216A - Air conditioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce power consumption of a compressor and an air distribution fan of an air conditioner and to suppress degradation of heat exchanging performance of a heat exchanger. <P>SOLUTION: This air conditioner is provided with a refrigerating cycle constituted by connecting an outdoor machine 13 comprising the compressors 1, 2, a four-way valve 3, an outdoor heat exchanger 4, an outdoor expansion valve 5 and an outdoor air distribution fan 8, and an indoor machine 12 comprising an indoor expansion valve 9 and an indoor heat exchanger 10 by a refrigerant pipe, and a power control means 21 controlling power consumption of the outdoor machine. The power control means 21 controls the increase and decrease of a rotational frequency of the outdoor air distribution fan by every control period in both of a cooling operation and a heating operation to minimize the total power of the compressor and the outdoor fan, and sets a lower limit value in the control of increase and decrease of the rotational frequency of the outdoor air distribution fan to the rotational frequency free from frost formation of the outdoor heat exchanger. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an air conditioner, and more particularly to an air conditioner that suppresses the total power of a compressor and an outdoor fan.

  In recent years, environmental problems have become a global issue, and one solution is energy saving. In addition, with the revision of JIS, APF (Annual Performance Factor) is obligated to be displayed, and there is an increasing demand for improvement of APF.

  As an energy-saving technology of an air conditioner, as described in Patent Document 1, the power consumption of a compressor during cooling operation and the power consumption of a fan motor that cools the refrigerant of a condenser are calculated, and these It is known to increase / decrease the fan motor so that the total value is minimized.

Japanese Patent Publication No. 5-118609

  However, when the technique of the above-mentioned patent document is applied as it is to the heating operation by switching the four-way valve, there is a possibility that the heat exchange capability of the evaporator is lowered.

  That is, the total value of the power consumption of the compressor and the power consumption of the blower fan that heats the refrigerant of the evaporator during the heating operation decreases as the rotational speed of the blower fan decreases. Therefore, when the rotational speed of the blower fan is lowered to suppress power consumption, the low pressure of the refrigerant is lowered and the evaporation temperature is lowered. When the evaporation temperature is lowered to 0 ° C. or less, frost is attached to the evaporator. As a result of this frost formation, the heat exchange capacity may be significantly reduced.

  Then, this invention makes it a subject to suppress the power consumption by the compressor and ventilation fan of an air conditioner, and to suppress the heat exchange capability fall of a heat exchanger.

  In order to solve the above problems, an air conditioner of the present invention includes a compressor, a four-way valve, an outdoor heat exchanger, an outdoor expansion valve, an outdoor unit including an outdoor fan, an indoor expansion valve, and an indoor heat exchanger. The refrigeration cycle is formed by connecting the provided indoor units with refrigerant pipes, and further includes power control means for controlling the power consumption of the outdoor units. This power control means performs the increase / decrease control of the rotational speed of the outdoor blower fan for each control cycle in both the cooling operation and the heating operation, minimizes the total power of the compressor and the outdoor fan, and also performs the heating operation. In some cases, the lower limit value of the increase / decrease control of the rotational speed of the outdoor fan is set to a rotational speed at which the outdoor heat exchanger does not form frost.

  That is, during normal operation during both cooling and heating operations, the total power of the compressor and the outdoor fan is minimized by increasing / decreasing the rotational speed of the outdoor fan. On the other hand, during the heating operation, the lower limit value of the rotation speed increase / decrease control of the blower fan is set to the rotation speed at which the outdoor heat exchanger does not form frost, so that the heat exchange capacity decline of the heat exchanger due to frost formation is suppressed. be able to.

  In this case, the control content of the power control means during the cooling operation can be as follows. First, the initial rotational speed of the outdoor blower fan is set near the upper limit rotational speed of the fan, and the rotational speed of the outdoor blower fan is decreased by a predetermined reduction width in the initial control cycle, and the power of the compressor and The power of the outdoor fan is detected and the total power of these is obtained, and the total power in the previous control cycle is compared with the total power in the current control cycle.

  If the total power is reduced and the reduction range is greater than a preset value, that is, the direction of increase / decrease in the number of revolutions in the previous control cycle is an appropriate direction, and is not yet near the minimum power. When it has not reached, the rotation speed of the outdoor fan is changed in the same direction as the increase / decrease direction of the rotation speed of the outdoor fan in the previous control cycle with the same increase / decrease width as the increase / decrease width in the previous control cycle.

  On the other hand, if the total power has increased, that is, if it has passed near the minimum power corresponding to the lower end of the parabola due to the increase or decrease of the rotation speed in the previous control cycle, the rotation speed of the outdoor fan is In the direction opposite to the increase / decrease direction of the rotational speed of the outdoor fan in the control cycle, the change is made with an increase / decrease width smaller than the increase / decrease width in the previous control cycle, for example, an increase / decrease width of 1/2 of the previous control cycle.

Also, when the total power is decreasing and the decrease is smaller than the preset value, that is, when it is determined that the total power is decreasing but the decrease is small and the vicinity of the minimum power is reached, or the total When the electric power is the same value, the rotational speed of the outdoor fan is maintained. Thus, the total power can be minimized by monitoring the total power and performing control for adjusting the rotation speed of the outdoor fan.
Moreover, the control content of the electric power control means at the time of heating operation can be made as follows. A temperature sensor for detecting the refrigerant temperature of the outdoor heat exchanger is provided. First, the power control means sets the initial rotational speed of the outdoor blower fan in the vicinity of the upper limit rotational speed of the fan, and a predetermined decrease width in the initial control cycle. The number of rotations of the outdoor blower fan is reduced and the compressor power and the outdoor blower fan power are detected for each control period to obtain the total power, and the total power in the previous control period and the total in the current control period are obtained. Compare with power.

  If the total power is reduced, the rotational speed of the outdoor blower fan is reduced by the same reduction width as that in the previous control cycle. When the total power is increased or equal, the rotational speed of the outdoor blower fan is reduced. Each time the rotational speed of the outdoor blower fan is reduced while maintaining the control, it is determined whether or not the detected temperature of the temperature sensor is 0 ° C. or lower. Is returned to the rotational speed before the decrease, and the rotational speed is maintained.

  Accordingly, it is possible to suppress a reduction in heat exchange capacity due to frost formation on the outdoor heat exchanger while minimizing the total power of the compressor and the outdoor fan.

  Further, the power control means controls the increase / decrease in the rotation speed of the outdoor fan so that the high pressure, low pressure, and pressure ratio of the refrigeration cycle are within a preset range in both cooling operation and heating operation. Can be configured.

  ADVANTAGE OF THE INVENTION According to this invention, the power consumption by the compressor and ventilation fan of an air conditioner can be suppressed, and the heat exchange capability fall of a heat exchanger can be suppressed.

  Hereinafter, embodiments of an air conditioner to which the present invention is applied will be described with reference to FIGS. In the following description, a so-called multi-type air conditioner in which a plurality of indoor units are connected to one outdoor unit will be described as an example. The present invention can also be applied to an air conditioner for general households that are connected in a one-to-one relationship.

  FIG. 1 is an overall configuration diagram of the air conditioner of the present embodiment. The air conditioner is configured by connecting an outdoor unit 13 and two indoor units 12 by a liquid refrigerant pipe 14 and a gas refrigerant pipe 15.

  The outdoor unit 13 includes a variable capacity compressor 1 that is controlled by changing an operation frequency with an inverter, and two fixed capacity compressors 2. Each of the compressors 1 and 2 is a four-way valve. 3 is connected in parallel. The four-way valve 3 is connected by piping to an outdoor heat exchanger 4 provided in parallel to each other, and is connected to a refrigerant amount regulator 7 via an outdoor expansion valve 5 provided for each outdoor heat exchanger 4. .

  In addition, an electric valve 6 that switches a flow path to the outdoor heat exchanger 4 is provided in a pipe connecting the four-way valve 3 and one outdoor heat exchanger 4. And the outdoor ventilation fan 8 which ventilates with respect to each outdoor heat exchanger 4 is provided.

  The high pressure side of the compressors 1 and 2 is provided with a high pressure sensor 16, the low pressure side is provided with a low pressure sensor 17, and each outdoor heat exchanger 4 is provided with a temperature sensor 18 for measuring the refrigerant evaporation temperature during heating. It has been. Furthermore, a wattmeter 19 for measuring the total power consumption of the compressors 1 and 2 and a wattmeter 20 for measuring the total power consumption of the outdoor blower fans 8 are provided. Although not shown, the detected values of the pressure sensors 16, 17, the temperature sensor 18, and the wattmeters 19, 20 are input to the power control means 21, and the output of the power control means 21 is also shown. The signal is input to each outdoor fan 8.

  Each indoor unit 12 includes an indoor expansion valve 9 and an indoor heat exchanger 10, and an indoor blower fan 11 that blows air to each indoor heat exchanger 10 is provided.

  Here, the power consumption characteristic of a general compressor will be described. The power consumption of the compressor is largely determined by (1) compressor efficiency (= compressor actual COP / compressor theoretical COP) and (2) power. Further, (1) the compressor efficiency is related to factors such as high pressure and pressure ratio (= high pressure / low pressure), and (2) the power depends on the compressor rotation speed and differential pressure (= high pressure). -Low pressure) and the density of refrigerant sucked (low pressure, due to suction SH).

  Among these items, except the compressor rotation speed, it fluctuates depending on the refrigerant pressure, and can be changed by the rotation speed of the outdoor blower fan. Therefore, by optimizing the rotation speed of the outdoor fan, the compressor efficiency can be increased and the compressor power can be reduced.

  Next, operation | movement of the air conditioner of this embodiment is demonstrated. As shown in FIG. 2, in general, the compressor efficiency should be low at a high pressure, and the pressure ratio is most effective at, for example, around 2.5.

  In the cooling operation, the high-temperature and high-pressure gas refrigerant compressed by the compressors 1 and 2 flows into the outdoor heat exchanger 4 through the four-way valve 3 as shown by the solid line arrows in the figure. Heat exchanger to condense. The condensed and liquefied refrigerant passes through the outdoor expansion valve 5, the surplus refrigerant is stored in the refrigerant amount regulator 7, and the remainder passes through the liquid refrigerant pipe 14 and is sent to the indoor unit 12. The sent liquid refrigerant flows into the indoor expansion valve 9, where it is decompressed to a low pressure to be in a low pressure two-phase state, and exchanges heat with air in the indoor heat exchanger 10 to evaporate and gasify. Thereafter, the gas refrigerant returns to the compressors 1 and 2 via the gas refrigerant pipe 15.

  During this refrigerant operation, as shown in FIG. 3, the rotational speed of the blower fan directly changes the high pressure, and the high pressure decreases as the rotational speed increases, and the pressure ratio and differential pressure decrease accordingly. . When the change in the compressor efficiency due to the change in the rotational speed is plotted in FIG. 2, it can be seen that when the fan rotational speed is increased at the normal outside air temperature, the high pressure and the pressure ratio are lowered, and the compressor efficiency is increased.

  Therefore, if the fan speed is increased, the compressor power decreases. However, since the fan power simply increases, there is a place where the total power of each of them is minimum as shown in FIG. As shown in FIG. 5, COP has the same tendency, and it can be seen that if the rotational speed is lowered from the upper limit of the rotational speed, the rotational speed at which the electric power is minimized is reached. The lower limit of the rotational speed is the rotational speed at which the high pressure is equal to or lower than the upper limit pressure.

A control flow by the power control means 21 based on these is shown in FIG. First, when the operation is started, the initial value [V ₀ ] of the outdoor blower fan rotation speed is set as the upper limit rotation speed (S1). Here, the upper limit number of rotations is the maximum number of rotations within a range that is equal to or less than the mechanical upper limit number of rotations of the fan and the high pressure and low pressure of the refrigeration cycle satisfy the minimum allowable pressure.

After a predetermined time has elapsed, the power consumption of the compressor and the fan is calculated by the wattmeters 19 and 20 to obtain the total power [P ₀ ] (S2). Subsequently, the rotational speed of the fan is reduced by a certain amount [ΔV ₀ ], for example, 10% of the current rotational speed (Vset = V ₀ −ΔV ₀ ) (S 3).

Next, the compressor has an operable pressure range, and in order to satisfy it, the high pressure sensor 16, the low pressure pressure, whether the high and low pressures of the refrigeration cycle are within the specified range. The determination is made by the sensor 17 (S4). If it is outside the specified range (NO in S4), the rotational speed is returned to the original value, and this control is terminated (S8). If within the specified range (YES in S4), the total power [P _n ] of the compressor and the fan is calculated (S5).

Then, the calculated total power [ _Pn ] is compared with the previous measurement value [ _Pn-1 ] to determine whether or not the power consumption has decreased (S6). If P _n−1 ≧ P _n and the power decreases or is equal (YES in S6), the power decrease amount [Q _n ] corresponding to ΔV _n corresponding to the power decrease rate (for example, Q _n = ΔP _n / Whether ΔV _n ) is equal to or _smaller than a predetermined value [Q _min ] is determined (S7). If it is determined that Q _n <Q _min and Q _n is not more than a predetermined value (NO in S7), the control is terminated.

On the other hand, if P _n-1 <P _{n and the} power is increased in S6 (NO in S6), the rotational speed is changed in the opposite direction to the previous time, and ΔV is set so that the rotational speed does not return to the previous rotational speed. Change by / 2 and return to (S4) (S9).

Further, the flow returns to change only _{Q n> Q min} becomes _{Q n} is (YES at S7) equal to or greater than a predetermined value, [Delta] V _n further fan speed to previous and the same direction in S7 (S4) (S10) . Here, ΔV _n is a value corresponding to Q _n (for example, ΔV _n = V _n × aQ _n a: constant) so that the power converges to the minimum rotation speed, and ΔV _n is increased if Q _n is large. , to reduce the ΔV _n the smaller the _{Q n.}

  In this way, the rotational speed of the outdoor fan 8 is controlled so that the power consumption is minimized based on the compressor efficiency, and the total of the fan power and the compressor power is minimized, thereby reducing the outdoor unit power consumption. Can be reduced.

  Next, the operation during the heating operation will be described. In the case of heating operation, the high-temperature and high-pressure gas refrigerant compressed by the compressors 1 and 2 passes through the four-way valve 3 and the gas refrigerant pipe 15 as shown by the dashed arrows in the figure, and the indoor heat exchanger of the indoor unit 12 10 where it condenses and liquefies by exchanging heat with air. The condensed and liquefied refrigerant flows into the refrigerant amount regulator 7 through the indoor expansion valve 9 and the liquid refrigerant pipe 14, and after being decompressed by the outdoor expansion valve 5, heat is exchanged with air in the outdoor heat exchanger 4 and evaporates. Gasify. The gasified refrigerant returns to the compressors 1 and 2 through the four-way valve 3.

  During such heating operation, the rotational speed of the outdoor blower fan 8 changes the low-pressure pressure although the amount of change is small. As a result, the compressor efficiency and differential pressure change. As shown in FIG. 7, in heating, the change in pressure is less as cooling, but when the number of fan rotations is increased, the pressure ratio decreases, but the high pressure and low pressure increase.

  As shown in FIG. 8, if the fan speed is decreased from the upper limit speed in the heating operation, both the compressor power and the fan power are lowered, and the COP is also raised as shown in FIG. Therefore, it can be seen that the fan rotational speed should be lowered to lower the total value of the compressor power and the fan power. However, when the fan rotation speed is decreased gradually, the evaporation temperature also decreases as the low-pressure pressure decreases, and when the evaporation temperature decreases to 0 ° C. or less, moisture contained in the air frosts on the outdoor heat exchanger. As a result, the heat exchange capacity is greatly reduced.

  So, in this invention, while suppressing the sum total of the power consumption of a compressor and the power consumption of an outdoor ventilation fan, the lower limit of a fan rotation speed is set and the frost formation to an outdoor heat exchanger is suppressed. Specifically, the lower limit of the rotational speed of the fan is set so that the evaporation temperature detected by the temperature sensor 18 does not become 0 ° C. or less. The upper limit of the rotation speed is the upper limit pressure of the low pressure.

The control flow by the power control means 21 during the heating operation is shown in FIG. Here, the same parts as the cooling operation are omitted, and only different parts will be described. When the operation is started, the initial value [V ₀ ] of the outdoor blower fan rotation speed is set to the upper limit rotation speed (S11). Here, the upper limit rotational speed is the maximum rotational speed within a range that is equal to or lower than the mechanical upper limit rotational speed of the fan and the low pressure of the cycle satisfies the maximum allowable pressure. The subsequent processing is basically the same as that during cooling operation, but in S14, processing is performed only during heating operation.

  That is, after the fan speed is changed in S13 and S17, the high pressure sensor 16 and the low pressure sensor 17 determine whether the high and low pressures of the refrigeration cycle and the upper and lower limits of the pressure ratio are within the specified ranges. Further, it is determined by the temperature sensor 18 whether the refrigerant evaporation temperature is 0 ° C. or less (S14). If it is determined that the refrigerant evaporation temperature is equal to or lower than 0 ° C. (NO in S14), the fan rotational speed is returned to the original (S18), and this control is terminated.

If the refrigerant temperature is higher than 0 ° C. (YES in S14), the total power [P _n ] of the compressor and the fan is calculated (S15), and the total power [P _n ] and the previous measured value [P _n−1 ] are calculated. To determine whether or not the power consumption has decreased (S16). Here, if the power is reduced because P _n−1 > P _n (YES in S16), the fan speed is decreased by a certain amount [ΔV ₀ ] (S17), and the process returns to S14. On the other hand, if the power does not decrease with P _n−1 ≦ P _n (NO in S16), it is considered that there is some abnormality and this control is terminated.

  As a result, based on the compressor efficiency, the rotational speed of the outdoor fan 8 is controlled so that the power consumption is minimized, and the total of the fan power and the compressor power is suppressed. Frosting can be suppressed, and as a result, a decrease in heat exchange capability of the outdoor heat exchanger can be suppressed.

It is a whole block diagram of the air conditioner of this embodiment. It is a figure which shows the relationship between the pressure ratio of a compressor, and compressor efficiency. It is a figure which shows the relationship between the rotation speed of an outdoor ventilation fan at the time of air_conditioning | cooling, and each pressure. It is a figure which shows the relationship between the power consumption of a compressor with respect to the rotation speed of the outdoor ventilation fan at the time of cooling, and the power consumption of a ventilation fan. It is a figure which shows the relationship between the rotation speed of the outdoor ventilation fan at the time of cooling, and COP. It is a flowchart of rotation speed control of the outdoor ventilation fan at the time of air_conditioning | cooling. It is a figure which shows the relationship between the rotation speed of the outdoor ventilation fan at the time of heating, and each pressure. It is a figure which shows the relationship between the power consumption of the compressor with respect to the rotation speed of the outdoor ventilation fan at the time of heating, and the power consumption of a ventilation fan. It is a figure which shows the relationship between the rotation speed of the outdoor ventilation fan at the time of heating, and COP. It is a flowchart of rotation speed control of the outdoor ventilation fan at the time of heating.

Explanation of symbols

1 Variable capacity compressor 2 Fixed capacity compressor
3 Four-way valve 4 Outdoor heat exchanger 5 Outdoor expansion valve 8 Outdoor blower fan 9 Indoor expansion valve 10 Indoor heat exchanger 11 Indoor blower fan 12 Indoor unit 13 Outdoor unit 14 Liquid connection pipe 15 Gas pipe 16 High pressure sensor 17 Low pressure sensor 18 Temperature sensors 19, 20 Wattmeter 21 Power control means

Claims (3)

A refrigeration cycle is established by connecting a compressor, a four-way valve, an outdoor heat exchanger, an outdoor expansion valve, and an outdoor unit equipped with an outdoor fan, and an indoor unit equipped with an indoor expansion valve and an indoor heat exchanger with a refrigerant pipe. An air conditioner comprising power control means for forming and controlling power consumption of the outdoor unit,
The power control means performs increase / decrease control of the rotational speed of the outdoor fan in each control cycle in both the cooling operation and the heating operation, and minimizes the total power of the compressor and the outdoor fan, An air conditioner characterized in that, during heating operation, the lower limit value of the increase / decrease control of the rotational speed of the outdoor fan is set to a rotational speed at which the outdoor heat exchanger does not form frost. The power control means sets the initial rotational speed of the outdoor blower fan in the vicinity of the upper limit rotational speed of the fan during the cooling operation, and decreases the rotational speed of the outdoor blower fan by a predetermined reduction width in the initial control cycle. In addition, the power of the compressor and the power of the outdoor blower fan are detected for each control cycle to obtain the total power, and the total power in the previous control cycle is compared with the total power in the current control cycle. ,
If the total power is reduced and the reduction range is larger than a preset value, the rotational speed of the outdoor fan is the same as the increase / decrease direction of the rotational speed of the outdoor fan in the previous control cycle. To the same increase / decrease width as the previous control cycle,
If the total power is increased, the rotation speed of the outdoor fan is increased or decreased in the opposite direction to the increase or decrease direction of the rotation speed of the outdoor fan in the previous control period, which is smaller than the increase or decrease width in the previous control period. Change
2. The rotational speed of the outdoor fan is maintained when the total power is reduced and the reduction width is smaller than a preset value or when the total power is the same value. The air conditioner described in 1. A temperature sensor that detects a refrigerant temperature of the outdoor heat exchanger, and the power control means sets an initial rotational speed of the outdoor blower fan in the vicinity of an upper limit rotational speed of the fan during heating operation, and an initial control cycle The rotational speed of the outdoor blower fan is reduced by a predetermined reduction width at the same time, and the power of the compressor and the outdoor blower fan are detected for each control cycle to obtain the total power, and in the previous control cycle Compare the total power with the total power in the current control cycle,
If the total power is reduced, the rotational speed of the outdoor blower fan is reduced by the same reduction width as the previous control cycle, and when the total power is increased or equal, the rotational speed of the outdoor blower fan is reduced. While performing control to maintain
Each time the rotational speed of the outdoor blower fan is decreased, it is determined whether or not the temperature detected by the temperature sensor is 0 ° C. or lower. When the detected temperature is 0 ° C. or lower, the rotational speed of the outdoor blower fan is decreased before the decrease. The air conditioner according to claim 1, wherein the rotational speed is maintained by returning to a number.

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