JP2014190561A - Air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect a compressor by detecting a current change of the compressor and to prevent a delay in compressor protection control due to detection of a condensation temperature.SOLUTION: An air conditioner, in which a refrigeration cycle includes: a compressor 1; a four-way valve 2; an indoor heat exchanger 3; an expansion valve 4; an outdoor heat exchanger 5; and a refrigerant pipe 6, comprises: a temperature sensor 7 that detects a condensation temperature of the indoor heat exchanger 3; a temperature sensor 8 that detects a condensation temperature of the outdoor heat exchanger 5; a current sensor 9 that detects a current carried to the compressor 1; and control means 10 that decrease a rotational speed of the compressor 1 if the condensation temperature detected by the temperature sensor 7 or 8 is equal to or higher than a predetermined temperature, and that further decreases the rotational speed of the compressor if the current of the compressor 1 detected by the current sensor 9 increases while the compressor 1 operates at a constant rotational speed after decreasing the rotational speed of the compressor 1.

Description

  The present invention relates to an air conditioner that protects a compressor when the discharge pressure of the compressor becomes abnormally high.

  FIG. 3 shows a configuration of a general heat pump type air conditioner. In this air conditioner, a refrigeration cycle is constituted by the compressor 1, the four-way valve 2 that switches the refrigerant circulation direction between heating and cooling, the indoor heat exchanger 3, the expansion valve 4, the outdoor heat exchanger 5, and the refrigerant pipe 6. ing. In FIG. 3, the four-way valve 2 is switched for heating operation.

  In this air conditioner, when the refrigerant discharged from the compressor 1 circulates through the refrigerant pipe 6, for example, when the user decreases the fan rotation speed of the indoor unit, the heat exchange amount in the indoor heat exchanger 3 decreases. As a result, the difference between the room temperature and the set temperature increases, which may temporarily increase the rotational speed of the compressor 1 and increase the discharge pressure. In addition, although not shown in the figure, when a plurality of indoor units are installed for one compressor, and the operation of some of them is stopped, the amount of heat exchange decreases and the compression is similarly performed. The rotation speed of the machine 1 temporarily increases, and the discharge pressure may increase. Therefore, conventionally, the discharge pressure of the compressor 1 is detected by the pressure sensor 21, and when the detected pressure exceeds a predetermined value, the control circuit 10A shifts to a protective operation for reducing the rotational speed of the compressor 1. The compressor 1 is protected (Patent Document 1). Reference numeral 9 denotes a current sensor for monitoring the current flowing through the compressor 1.

  However, since the pressure sensor 21 for detecting the discharge pressure is expensive, in the low-cost type air conditioner, as shown in FIG. 4, the temperature sensor 7 detects the condensation temperature of the indoor heat exchanger 2 in the heating operation, In the cooling operation, the condensation temperature of the outdoor heat exchanger 5 is detected by the temperature sensor 8, and the detected temperature is converted into the discharge pressure of the compressor 1 in the control circuit 10B, so that the discharge pressure does not increase too much. Reducing the number of revolutions has been done.

  FIG. 5 shows the contents of control for an example of heating operation. Here, when the condensation temperature of the indoor heat exchanger 3 detected by the temperature sensor 7 exceeds TE2 (> TE1) (when entering the zone C), the rotational speed of the compressor 1 is reduced by N1 from the present. In this state, the state of the timer 11 is seen for a preset time T1. If the condensation temperature has dropped below TE2 when time T1 has elapsed, the protection operation is canceled.

  However, when the condensing temperature exceeds TE3 (> TE2) at the elapse of time T1 (when entering zone D), the rotation speed of the compressor 1 is further reduced by N2 (≈5 × N1), In this state, the state is seen again only for time T1. If the condensation temperature has dropped below TE3 when the time T1 has elapsed, the process returns to the above-described zone C.

  However, when the condensation temperature exceeds TE4 (> TE3) when time T1 has elapsed (when entering zone E), the rotation of the compressor is stopped. As a result, if the condensation temperature falls below TE4, the zone D is restored. At this time, the rotational speed of the compressor 1 in the zone D is the previous rotational speed (the rotational speed that is reduced by N2 from the rotational speed in the zone C when the zone C is shifted to the zone D).

  Furthermore, if the condensing temperature drops below TE3 and returns to zone C when time T1 elapses, the state is further observed only for time T1. At this time, the rotational speed of the compressor 1 in the zone C is the previous rotational speed (the rotational speed that is decreased by N1 from the rotational speed in the zone B when the zone B is shifted to the zone C). Thereafter, when the temperature drops below TE2, the protection operation is released.

  By controlling the rotation speed of the compressor 1 according to the level of the detected value of the condensation temperature by the control as described above, the discharge pressure of the compressor 1 is prevented from becoming abnormally high and the protection is performed. .

JP 2003-139418 A

  However, in the method for detecting and controlling the condensation temperature by detecting the condensation temperature as described above, the temperature is influenced by the surroundings, or the temperature in the refrigerant pipe and the detected temperature detected by the temperature sensor are used. There may be a case where an accurate condensation temperature cannot be detected due to a deviation. Further, when the discharge pressure of the compressor suddenly rises, the temperature change cannot follow it, and the discharge pressure may exceed the limit value and adversely affect the compressor.

  Therefore, the reliability of the compressor is ensured by reducing or stopping the compressor more than necessary so that the reliability is not affected, and the protection operation is performed with excess or margin. On the other hand, comfort was impaired.

  An object of the present invention is to provide an air conditioner that detects a change in the current of a compressor and protects it, and prevents a delay in compressor protection control due to detection of a condensation temperature.

To achieve the above object, an air conditioner according to a first aspect of the present invention includes a compressor, a four-way valve that switches a refrigerant circulation direction between heating and cooling, an indoor heat exchanger, an expansion valve, an outdoor heat exchanger, and a refrigerant. In an air conditioner in which a refrigeration cycle is configured to include at least piping, a first temperature sensor that detects a condensation temperature of the indoor heat exchanger and a second temperature sensor that detects a condensation temperature of the outdoor heat exchanger And a current sensor that detects a current flowing through the compressor, and the condensation temperature detected by the first or second temperature sensor is equal to or higher than a predetermined temperature, the rotation speed of the compressor is reduced and the reduced And a control means for further reducing the rotational speed of the compressor when the current of the compressor detected by the current sensor increases during the subsequent operation at a constant rotational speed.
According to a second aspect of the present invention, in the air conditioner according to the first aspect of the present invention, the air conditioner includes a timer that starts measuring time when the condensation temperature is equal to or higher than the predetermined temperature, and the control means The current sensor reduces the rotation of the compressor by a predetermined number of revolutions according to the condensation temperature of the compressor and the compressor is operated at a constant number of revolutions before the timer expires. When the phenomenon that the current of the compressor detected in (4) increases occurs, the rotation speed of the compressor is decreased.

  According to the present invention, when the compressor is operated at a constant rotation speed and the compressor current increases, the rotation speed of the compressor is decreased, so that an increase in the discharge pressure of the compressor can be detected quickly. Based on this, proper compressor protection control can be realized.

It is a block diagram of the air conditioner provided with the control circuit for the compressor protection of the Example of this invention. It is a timing chart of control of compressor protection of the example. It is a block diagram of the air conditioner provided with the control circuit for the conventional compressor protection. It is a block diagram of the air conditioner provided with the control circuit for another conventional compressor protection. It is explanatory drawing of control by the control circuit of FIG.

  FIG. 1 shows an air conditioner according to one embodiment of the present invention. A refrigeration cycle is configured by the compressor 1, the four-way valve 2, which switches the refrigerant circulation direction between heating and cooling, the indoor heat exchanger 3, the expansion valve 4, the outdoor heat exchanger 5, and the refrigerant pipe 6. In FIG. 1, the four-way valve 2 is switched for heating operation. And the temperature sensor 7 for detecting the condensation temperature of the refrigerant | coolant at the time of heating operation is arrange | positioned at the indoor heat exchanger 3, and the temperature sensor 8 for detecting the condensation temperature of the refrigerant | coolant at the time of air_conditionaing | cooling operation at the outdoor heat exchanger 4. Is arranged. Furthermore, a current sensor 9 that detects the current of the compressor 1 is attached to the compressor 1. 10 is a control circuit, and 11 is a timer.

  In this embodiment, the temperature sensor 7 detects the condensation temperature of the indoor heat exchanger 4 during heating operation. In addition, the current flowing through the compressor 1 is monitored by using the current sensor 9 originally provided for current monitoring. Then, these detection signals are taken into the control circuit 10, and the rotational speed of the compressor 1 is controlled by the control circuit 10 to protect the compressor. Usually, if the rotation speed of the compressor 1 does not change and the discharge pressure does not change, the current value of the compressor 1 does not change. However, when the rotation speed of the compressor 1 is constant and the discharge pressure increases, the current value increases.

  Therefore, in the present invention, the discharge pressure of the compressor 1 increases when the current value of the compressor 1 increases even though the rotation speed of the compressor 1 is constant by using this characteristic. Estimated. The change in the current value at this time is not affected by the ambient temperature and has high followability to the discharge pressure. That is, the change in the current value also corresponds to a rapid pressure change that the temperature sensor 7 or 8 cannot follow.

  FIG. 2 shows a time chart of compressor rotation control during heating operation. This control is all performed in the control circuit 10. At time t1, for example, as described above, when the user decreases the fan rotation speed of the indoor unit, the amount of heat exchange in the indoor heat exchanger 3 decreases, and the difference between the room temperature and the set temperature increases. The rotation speed of the compressor 1 increases and the current also increases. At this time, the amount of current change increases.

  Then, at time t2 after a lapse of time from time t1, the inclination of the rise in the condensation temperature detected by the temperature sensor 7 that reacts slowly becomes abrupt.

  Thereafter, when the condensation temperature becomes equal to or higher than the temperature TE2 described in FIG. 5 at time t3, the vehicle enters the zone C in FIG. As a result, a protection instruction for reducing the rotational speed of the compressor 1 by N1 is output from the control circuit 10, and at the same time, the timer 11 starts a time counting operation. Thereafter, the compressor 1 maintains a constant rotational speed that is reduced by N1.

  Thereafter, the control circuit 10 estimates that the discharge pressure of the compressor 1 is increasing when the current shows an increasing tendency (period Ta) although the rotational speed does not change. Then, based on this estimation, the protection instruction is output again at time t4, and the rotation speed of the compressor 1 further decreases by N1.

  At time t5, the timer 11 completes a predetermined time (time until the condenser temperature changes as the compressor speed decreases, for example 120 seconds), that is, the time is up. If the condensing temperature at that time is equal to or higher than TE2 in the zone C, it is determined that the discharge pressure has increased, and the rotational speed of the compressor 1 is decreased again by N1.

  Thus, in this embodiment, by monitoring the current increase during the operation of the compressor 1 at a constant rotational speed, the increase in the discharge pressure of the compressor 1 is estimated at an early stage, and before the timer 11 times up, Since the rotation speed of the compressor 1 is reduced from the current level, the protection is complete. The rotation speed reduction control based on the current increase during the operation of the compressor 1 according to the present embodiment may be performed twice or more before the timer expires. The number of rotations to be reduced at this time is not limited to N1.

  In FIG. 2, a portion corresponding to the operation described in FIG. 5 is indicated by a wavy line. In the conventional example, the rotation speed of the compressor 1 is decreased by N1 only once before the timer 1 times out, so that there is a case where a sufficient decrease in the discharge pressure cannot be realized. On the other hand, according to the present embodiment, if the rotation speed of the compressor 1 does not change and the current of the compressor 1 increases, the rotation speed of the compressor 1 can be obtained even if the timer 11 does not expire. Is reduced again, it is possible to effectively avoid an abnormal increase in the discharge pressure of the compressor 1.

  In the above, the control in the temperature range of the zone C in FIG. 5 has been described, but also in other zones, when the rotation speed of the compressor 1 does not change and the current of the compressor 1 increases, Further, by presuming an increase in the discharge pressure of the compressor 1 and reducing the rotational speed of the compressor 1, protection of the compressor 1 can be realized.

  Further, the above is the case of the heating operation, but in the case of the cooling operation, the same can be implemented by detecting the condensation temperature of the outdoor unit heat exchanger 5 with the temperature sensor 8.

  1: compressor, 2: four-way valve, 3: indoor unit heat exchanger, 4: decompressor, 5: outdoor unit heat exchanger, 6: refrigerant piping, 7, 8: temperature sensor, 9: current sensor, 10, 10A, 10B: control circuit, 11: timer, 21: pressure sensor

Claims (2)

In an air conditioner in which a refrigeration cycle is configured to include at least a compressor, a four-way valve that switches a refrigerant circulation direction between heating and cooling, an indoor heat exchanger, an expansion valve, an outdoor heat exchanger, and a refrigerant pipe.
A first temperature sensor for detecting a condensation temperature of the indoor heat exchanger;
A second temperature sensor for detecting a condensation temperature of the outdoor heat exchanger;
A current sensor for detecting a current flowing through the compressor;
When the condensation temperature detected by the first or second temperature sensor becomes equal to or higher than a predetermined temperature, the rotational speed of the compressor is decreased, and is detected by the current sensor during operation at a constant rotational speed after the decrease. Control means for further reducing the rotational speed of the compressor when the current of the compressor increases;
An air conditioner comprising: In the air conditioner according to claim 1,
A timer that starts counting when the condensation temperature is equal to or higher than the predetermined temperature;
The control means reduces the rotation of the compressor by a predetermined number of revolutions according to the condensation temperature at the time when the timer times out,
In addition, if the phenomenon that the current of the compressor detected by the current sensor increases when the compressor is operating at a constant rotational speed before the timer expires, the rotation of the compressor An air conditioner characterized by reducing the number.

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