Abstract:
A compressor control system including a controller for controlling the operation of a compressor, a power source unit for supplying power to the compressor, and a power converting device for subjecting the power from the power source unit to conversion processing and then supplying the power thus converted to the controller, the controller being reset on the basis of input of a reset signal to stop said compressor, is further provided with a power monitoring device for monitoring a power state (e.g., power failure or not) of the power source unit, and outputting the reset signal to the controller when the power supply of the power source unit is intercepted.

Description:
BACKGROUND OF TH INVENTION 
     1. Field of the Invention 
     The present invention relates to a compressor control system for an air conditioner, and particularly to a compressor control system for an air conditioner which improves the control of the operation of a rotary type compressor. 
     2. Description of the Related Art 
     According to most of generally-known air conditioners, air cooling/heating operation is carried out through a refrigeration cycle in which refrigerant alternately repeats condensation and evaporation, and in this refrigeration cycle the refrigerant is subjected to a high-temperature and high-pressure process and also compressed so that the refrigerant is provided with circulating power. A rotary or scroll type compressor is more frequently used to compress the refrigerant, and an induction motor or a DC motor is also more frequently used as an electric motor for these types of compressors. As one of these compressors is known a rotary type compressor  1  containing a single-phase induction motor which is driven by single-phase power as shown in FIG.  1 . 
     According to the induction motor, voltage is applied to plural coils while varying the phase of the voltage among the coils, thereby generating a rotating magnetic field, and a rotator is driven by the rotating magnetic field thus generated. In the case of the single-phase induction motor, the phase of the power source is single, and thus the voltage of the power source is applied to a primary coil while a voltage which is advanced in phase by inserting a capacitor in series is applied to an auxiliary coil, thereby generating a rotating magnetic field. This type of induction electric motor is known as a capacitor run motor type, and it is frequently used. The rotating magnetic field generated by the above capacitor run motor is more unstable than that generated by a three-phase induction motor based on a three-phase alternating power source, and the rotational force induced is more inhomogeneous. 
     The single-phase induction electric motor will be described in more detail with reference to FIG.  1 . 
     The single-phase induction motor of the compressor  1  is supplied with an alternating voltage of about 200 V from a power source unit  2 . The operation (start, stop) of the compressor  1  is controlled on the basis of an operating signal from a controller  3 . The controller  3  controls not only the compressor  1 , but also the other parts of an air conditioner. 
     The voltage from the power source unit  2  is stabilized by a power converting device  4  comprising a transformer  5 , a rectifying/smoothening circuit  6  and a voltage regulating circuit (constant-voltage circuit)  7 , and the voltage thus stabilized is finally applied to the controller  3 . When the voltage supply from the power source unit  2  is interrupted due to a power failure, a reset signal is output from the voltage regulating circuit  7  of the power converting device  4  to the controller  3  to reset the controller  3 , whereby an operating signal output from the controller  3  to the compressor  1  is extinguished. The operating signal is used to actuate the compressor  1 . 
     However, since an electrolytic capacitor is used for the rectifying/smoothening circuit  6  of the power converting device  4 , the voltage supply from the voltage regulating circuit  7  to the controller  3  is continued for several hundreds msec from the occurrence of the power failure. Therefore, no reset signal is output from the voltage regulating circuit  7  to the controller  3 , so that the controller  3  continues to operate and output the operating signal to the compressor  1 . That is, the compressor  1  continues to rotate for the above time period. 
     Furthermore, the power supply from the power source unit  2  to the compressor  1  is interrupted simultaneously with the occurrence of the power failure, and a roller  8 A of the compressor  1  continues to rotate in a normal direction A by the inertial force and finally stops as shown in FIG.  2 . When the power failure occurs in the process of compressing refrigerant, the compressed refrigerant applies its repulsive force acting in the opposite (reverse) direction B to the normal direction to the roller  8 A of the compressor  1  under the compression process indicated by a two-dotted chain line of FIG.  2 . 
     In FIG. 2, reference numeral  8 B represents a cylinder, reference numeral  8 C represents a vane, and reference numerals  8 D and  8 E represent a suction port and a discharge port provided to the cylinder  8 B. 
     In the case of a long-term (several hundreds msec or more) power failure, when the compressor  1  is in the refrigerant compressing process at the time of occurrence of the power failure, with the repulsive force induced by the compressed refrigerant, the compressor  1  starts to rotate in the reverse direction due to the interruption of the power supply to the compressor  1 . However, during the long-term power failure, the voltage supply from the voltage regulating circuit  7  to the controller  3  is interrupted, and thus the reset signal is output from the voltage regulating circuit  7  to the controller  3  to reset the controller  3 , so that the operating signal from the controller  3  to the compressor  1  is extinguished. Therefore, the reverse rotation of the compressor  1  is stopped. 
     On the other hand, in the case of a short-term (from several tens (about 40) msec to several hundreds msec or less) power failure, when the compressor  1  is in the refrigerant-compressing process at the time of occurrence of the power failure, the repulsive force induced by the compressed refrigerant causes the compressor  1  to start rotating in the reverse direction, however, the voltage supply from the voltage regulating circuit  7  to the controller  3  still continues during this power failure, so that no reset signal is output from the voltage regulating circuit  7  to the controller  3 , so that the controller  3  continues to output the operating signal to the compressor  1 . Accordingly, when the power is restored after the short-term power failure, the single-phase induction motor of the compressor  1  generates unstable rotational magnetic field, and the rotational force in the normal direction is weak, so that the compressor  1  continues to rotate in the reverse direction. 
     The reverse rotation of the compressor  1  causes increase of the pressure in the compressor  1  and heating, and lubricant oil in the compressor  1  is deteriorated, finally resulting in failure of the compressor  1 . 
     Usually, the compressor  1  is provided with a device for monitoring the pressure at the exit thereof or the operation current thereof to prevent the failure of the compressor  1 . In the reverse rotation state of the compressor, there is little variation from the normal state in the pressure at the exit and the operation current, so that the reverse rotation phenomenon cannot be detected by using the monitoring device described above. Further, even when a thermostat for detecting the increase of temperature or the like is provided to the coil of the electric motor of the compressor, it takes long time until the temperature of the coil increases to a temperature at which the thermostat operates, and thus the compressor  1  may fail due to the reverse rotation of the compressor  1 . 
     Besides, when the reset signal is output from the voltage regulating circuit  7  of the power converting device  4  to the controller  3 , depending on the power occurrence manner of the power source unit  2 , some dispersion may occur in reset time in which the reset of the controller  3  is completed, and particularly when the voltage of the power source unit  2  is reduced, the voltage regulating circuit  7  may erroneously output a reset signal to the controller  3 . 
     SUMMARY OF THE INVENTION 
     The present invention has been implemented in view of the foregoing situation, and has an object to provide a compressor control system for an air conditioner which can surely prevent the reverse rotation phenomenon of a compressor when a power failure occurs. 
     In order to attain the above object, a compressor control system according to the present invention which includes a controller for controlling the operation of a compressor, a power source unit for supplying power to the compressor, and a power converting device for subjecting the power from the power source unit to conversion processing and then supplying the power thus converted to the controller, the controller being reset on the basis of input of a reset signal to stop the compressor, is characterized by further including a power monitoring device for monitoring a power state of the power source unit, and outputting the reset signal to the controller when the power supply of the power source unit is intercepted. 
     According to the above-described compressor control system, the power monitoring device outputs the reset signal to the controller at the interception time of the power of the power source unit, and the controller is reset on the basis of the reset signal to stop the compressor. Therefore, when the electric motor of the compressor is a single-phase induction motor, the compressor is in the refrigerant-compressing process at the interception time of the power, and thus even when the compressor is about to be reversely rotated by the repulsive force of the compressed refrigerant due to the power interception, the controller to which the power is continued to be supplied from the power converting device is reset to stop the compressor, so that the reverse rotation phenomenon of the compressor can be surely prevented. 
     Further, the power monitoring device monitors the power state of the power source unit, and outputs the reset signal to the controller at the interruption time of the power, so that no reset signal is output to the controller when the voltage of the power source unit is instantaneously reduced. Accordingly, when the voltage of the power source unit is instantaneously reduced, the control device is not reset and thus the compressor is not stopped. Therefore, the malfunction of the compressor can be avoided, and the operation of the air conditioner can be performed with high reliability. 
     In the above-described compressor control system, the power monitoring device may output the reset signal after a fixed time elapses from the interruption of the power supply of the power source unit. 
     According to the above-described compressor control system, the following effect can be achieved. 
     The power monitoring device outputs the reset signal to the controller after a fixed time elapses from the interruption of the power of the power source unit, and thus if the fixed time is set to such a time that when the power interruption occurs in the compression process during which the compressor compresses refrigerant, the compressor is not reversely rotated even by the repulsive force of the compressed refrigerant, the controller is reset and thus the compressor is stopped in the case of a short-term power failure in which the power interruption state continues even after a fixed time elapses from the interruption of the power although the compressor starts to rotate in the reverse direction. Therefore, the reverse phenomenon of the compressor can be surely prevented. 
     On the other hand, in the case of a short-term power failure in which the power interruption state is finished before a fixed time elapses from the power interruption, no reset signal is output from the power monitoring device to the controller, and the compressor does not start to rotate in the reverse direction during this time, so that the compressor an be continued to rotate in the normal direction even after the extremely-short-term power failure is finished, and thus the reduction of the operation performance of the air conditioner is not induced. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram showing a conventional compressor control system for an air conditioner; 
     FIG. 2 is a plan cross-sectional view showing a cylinder portion of a compressor; 
     FIG. 3 is a diagram showing a refrigerant circuit of an air conditioner containing a compressor of FIG. 4; and 
     FIG. 4 is a block diagram showing an embodiment of a compressor control system for an air conditioner according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A preferred embodiment according to the present invention will be described hereunder with reference to the accompanying drawings. 
     FIG. 3 is a diagram showing a refrigerant circuit of an air conditioner. 
     As shown in FIG. 3, an air conditioner  10  includes an outdoor unit  11 , an indoor unit  12  and a controller  13 , and an outdoor refrigerant pipe  14  of the outdoor unit  11  and an indoor refrigerant pipe  15  of the indoor unit  12  are linked to each other through link pipes  24  and  25 . 
     The outdoor unit  11  is disposed outdoors, and the compressor  16  is disposed in the outdoor refrigerant pipe  14 . An accumulator  17  is connected to the suction side of the compressor  16  through the outdoor refrigerant pipe  14 , a four-way change-over valve  18  is connected to the discharge side of the compressor  16  through the outdoor refrigerant pipe  14 , and an outdoor heat-exchanger  19  is connected to the four-way change-over valve  18  through the outdoor refrigerant pipe  14 . An outdoor fan  20  for blowing air to the outdoor heat-exchanger  19  is disposed in the vicinity of the outdoor heat-exchanger  19 . 
     Further, the indoor unit  12  is disposed indoors, an indoor heat-exchanger  21  is disposed in the indoor refrigerant pipe  15 , and an electric expansion valve  22  is disposed in the neighborhood of the indoor heat-exchanger  21  in the indoor refrigerant pipe  15 . An indoor fan  23  for blowing air to the indoor heat-exchanger  21  is disposed in the neighborhood of the indoor heat-exchanger  21 . 
     The controller  13  controls the operation of the outdoor unit  11  and the indoor unit  12 , and more specifically, the controller  13  controls the compressor  16 , the four-way change-over valve  18  and the outdoor fan  20  of the outdoor unit  11 , and the electric expansion valve  22  and the indoor fan  23  of the indoor unit  12 . 
     The controller  13  controls the switching operation of the four-way change-over valve  18  to set the operation of the air conditioner  10  to one of cooling operation and heating operation. That is, when the controller  13  switches the four-way change-over valve  18  to the cooling operation side, refrigerant flows as indicated by solid-line arrows. In this case, the outdoor heat-exchanger  19  serves as a condenser while the indoor heat-exchanger  21  serves as an evaporator, whereby the operation state of the air conditioner is set to the cooling operation state, and the indoor heat-exchanger  21  of the indoor unit  12  cools the room. On the other hand, when the controller  13  switches the four-way change-over valve  18  to the heating operation side, the refrigerant flows as indicated by broken-line arrows. In this case, the indoor heat-exchanger  21  serves as a condenser while the outdoor heat-exchanger  19  serves as an evaporator, whereby the operation state of the air conditioner is set to the heating operation state, and the indoor heat-exchanger  21  of the indoor unit  12  heats the room. 
     In accordance with the air conditioning load of the indoor unit  12 , the controller  13  also controls the opening degree of the electric expansion valve  22  of the indoor unit  12 , and controls the fan driving system of the indoor fan  23  in the indoor unit  12 . 
     The operation control of the compressor  16  by the controller  13  is performed by using a compressor control system  30  shown in FIG. 4, and the compressor control system  30  is constructed by not only the controller  13 , but also a power source unit  31 , a power converting device  32  and a power monitoring device  33 . 
     Here, the compressor  16  provides a circulating force to the refrigerant which alternately repeats condensation and compression in a refrigerant circuit, and exposes the refrigerant to a high-temperature and high-pressure process. In this embodiment, a rotary type compressor is used as the compressor  16 . As described above, the rotary type compressor and the scroll type compressor suffer a repulsive force acting in the opposite direction (reverse direction) to the normal direction from the compressed refrigerant as described above. 
     As in the case of the prior art, a single-phase induction motor is used as an electric motor for the compressor  16 . Although the single-phase induction motor generates more unstable rotational magnetic field as compared with a three-phase induction motor and the rotational force is inhomogeneous, it has advantages that it has a simple construction and it is designed at a low cost. 
     The power source unit  31  is used to supply operating power to the air conditioner  10 . It directly supplies power to the compressor  16 , the outdoor fan  20 , the four-way change-over valve  18  and the indoor fan  23 , and also supplies converted power through the power converting device  32  to the controller  13  and the electric expansion valve  22 . The voltage supplied from the power source unit  31  is set to 200 V±10% in Japan, however, this voltage is not limited to the above range in the case of an independent electric power plant or overseas. 
     The power converting device  32  converts the alternating power of the power source unit  31  to DC power, stabilizes the voltage thus converted, and then supplies the DC power thus converted to parts driven by the DC power such as the controller  13 , the electric expansion valve  22 , etc. The power converting device  32  is constructed by a transformer  34 , a rectifying/smoothening circuit  35  and a voltage regulating (constant-voltage) circuit  36 , however, a switching power source having the same function as these parts may be used. 
     The transformer  34  transforms alternating power (voltage) of about 200 V of the power source unit  31  to low voltage power of about 24 V. The rectifying/smoothening circuit  35  conducts full wave rectification on the low voltage alternating power from the transformer  34  through a bridge diode or the like, and then smoothens the rectified power through an electrolytic capacitor to obtain DC power of 12 V. Thereafter, the voltage regulating circuit  36  stabilizes the DC power from the rectifying/smoothening circuit  35  through a power regulator or the like, and then sets it to low voltage DC power of about 5 V. 
     As shown in FIG. 3, the controller  13  controls the compressor  16 , the four-way change-over valve  18 , the outdoor fan  20 , the electric expansion valve  22  and the indoor fan  23  to control the overall air conditioner  10  as described above. Particularly for the compressor  16 , an operating signal α shown in FIG. 4 is output to a relay (not shown) or the like, and the compressor  16  is started or stopped by actuating the relay or the like, thereby controlling the operation (start, stop) of the compressor  16 . 
     The controller  13  includes a microcomputer, and it is necessary to reset the microcomputer of the controller  13  for a predetermined time after the power source is turned on because the microcomputer is often unstable at the time of power-on. The reset of the microcomputer of the controller  13  is carried out by inputting a reset signal β (high-level voltage or low-level voltage) to a reset port (not shown). When the controller  13  is reset as described above, the operating signal α to the compressor  16  is extinguished and the compressor  16  is stopped. The other parts such as the four-way change-over valve  18 , the outdoor fan  20 , the electric expansion valve  22  and the indoor fan  23  are stopped in the same manner as described above. 
     The power monitoring device  33  monitors the power state of the power source unit  31 , and outputs the reset signal β to the controller  13  at the interruption time of the power of the power source unit  31  (that is, at the time of occurrence of power failure), and it comprises a pulse generating circuit  37  and a pulse monitoring circuit  38 . 
     The pulse generating circuit  37  generates pulses which are synchronized with the frequency of the power (voltage) of the power source unit  31 , and for example pulses whose period is equal to a half of the frequency of the power (voltage) of the power source unit  31  are generated by using a photocoupler, for example. At the time of the power failure, the power supply of the power source unit  31  is interrupted, and the supply of the pulse signals from the pulse generating circuit  37  is also stopped. 
     The pulse monitoring circuit  38  monitors the pulses generated from the pulse generating circuit  37  to monitor the power state of the power source unit  31 . The pulse monitoring circuit  38  contains a timer for counting a fixed time, and outputs the reset signal β to the controller  13  after the fixed time elapses from the time when no pulse is generated from the pulse generating circuit  37  due to the power failure (for example, after several tens (about 40) msec elapse from the occurrence of the power failure). Alternatively, the reset signal can be generated as soon as the pulses terminate. 
     The fixed time counted after the occurrence of the power failure is set to such a time that when the power failure occurs in the refrigerant compressing process of the compressor, the compressed refrigerant applies its repulsive force acting in the opposition (reverse) direction to the roller (see reference numeral  8 A of FIG. 2) which rotates in the forward direction by the action of the inertial force, however, the roller of the compressor  16  does not start to rotate in the reverse direction by even the repulsive force because the inertial force exceeds the repulsive force at this time. After the fixed time elapses, the roller of the compressor  16  starts to rotate in the reverse direction with the repulsive force. 
     The pulse monitoring circuit  38  continues to output the reset signal β to the controller  13  until a predetermined time elapses from the time when the power of the power source unit  31  is restored and the power source unit  31  starts to generate pulses, and stops the output of the reset signal β to actuate the controller  13  at the stage that the inside of the computer of the controller  13  is stabilized (after the predetermined time elapses). 
     Next, the control of the operation of the compressor control system  30  at the power-failure time will be described in each of the following three cases: a long-term power-failure case (power failure for several hundreds msec or more), a short-term power-failure case (power failure for several tens (about 40) msec to several hundred msec) and an extremely-short-term power-failure case (power failure for several tens (about 40) msec or less). 
     (1) Long-term Power Failure (Power Failure for several hundreds msec or more) 
     The power supply from the power source unit  31  to the compressor  16  is interrupted simultaneously with occurrence of a power failure, and when the power failure occurs during the refrigerant-compressing process, the compressor suffers the repulsive force of the compressed refrigerant in the opposite direction to the forward rotational direction and thus it rotates in the reverse direction. During the long-term power failure, the pulse monitoring circuit  38  of the power monitoring device  33  outputs the reset signal β to the controller  13  after the fixed time elapses (several tens (about 40) msec elapses) from the occurrence of the power failure, and the controller  13  is reset. The resetting of the controller  13  extinguishes the operating signal α output from the controller  13  to the compressor  16 . Accordingly, no operating signal α is output from the controller  13  to the compressor  16 , so that the compressor  16  does not continue to rotate in the reverse direction and finally stops. 
     During the long-term power failure, the power supplied from the voltage regulating circuit  36  of the power converting device  32  to the controller  13  is intercepted after several hundreds msec elapse from the occurrence of the power failure. 
     (2) Short-term Power Failure (Power Failure for several tens (about 40) msec to several hundreds sec) 
     As in the case of the above long-term power failure, the power to be supplied from the power source unit  31  to the compressor  16  is interrupted simultaneously with the occurrence of the power failure occurs. When the power failure occurs in the refrigerant-compressing process of the compressor, the compressor suffers the repulsive force of the compressed refrigerant in the reverse direction to the normal rotational direction, and starts to rotate in the reverse direction. Further, during the short-term power failure, the power supply from the voltage regulating circuit  36  of the power converting device  32  to the controller  13  is continued. However, the pulse monitoring circuit  38  of the power monitoring device  33  outputs the reset signal β to the controller  13  after a fixed time (several tens (about 40) msec) elapses from the occurrence of the power failure, and resets the controller  13 , whereby the operating signal α output from the controller  13  to the compressor  16  is extinguished. Accordingly, in this case, the reverse rotation of the compressor  16  is also stopped without being continued. 
     (3) Extremely-short-term Power Failure (Power Failure for several tens (about 40) msec or less) 
     In this case, the power supply from the power source unit  31  to the compressor  16  is intercepted at the same time when the power failure occurs. When the power failure occurs in the refrigerant-compressing process, the compressor suffers the repulsive force of the compressed refrigerant in the reverse direction to the normal rotational direction, however, it is still under the state before it starts to rotate and rotates in the normal direction by the inertial force. During this extremely-short-term power failure, the power is supplied from the voltage regulating circuit  36  of the power converting device  32  to the controller  13 , and also no reset signal is output from the pulse monitoring circuit  38  of the power monitoring device  33  to the controller  13 , so that the controller  13  is under operation. Accordingly, when the power from the power source unit  31  is restored from the above state, the rotational force of the compressor  16  in the same normal direction as before the power failure is increased, and the air conditioner  10  continues the operation before the power failure (cooling operation or heating operation). 
     With the above construction, the compressor control system  30  of the air conditioner  10  has the following effects (1) to (3). 
     (1) The power monitoring device  33  outputs the reset signal β to the controller  13  in the long-term or short-term power failure of the power source unit  31 , and the controller  13  is reset by the reset signal β to stop the compressor  16 . Therefore, in the case where the electric motor of the compressor  16  is a single-phase induction motor, the controller  13  to which the power is continued to be supplied from the voltage regulating circuit  36  of the power converting device  32  (in the case of the short-term power failure) is forcedly reset to stop the compressor  16  even when the compressor  16  is in the refrigerant-compressing process at the time of the occurrence of the long-term or short-term power failure and thus the compressor  16  is forced to be rotated in the reverse direction by the repulsive force of the compressed refrigerant. Therefore, the reverse rotation phenomenon of the compressor can be surely prevented. 
     (2) The power monitoring device  33  monitors the power state of the power source unit  31  with the pulses generated in the pulse generating circuit  37 , and outputs the reset signal β to the controller  13  when the power is interrupted (in the case of the long-term or short-term power failure). Therefore, when the voltage of the power source unit  31  is instantaneously reduced, no reset signal β is output to the controller  13 . Accordingly, it is avoided that the controller  13  is reset and the compressor is stopped when the voltage of the power source unit is instantaneously reduced. Therefore, the misoperation of the compressor  16  can be avoided, and the reliability of the operation of the air conditioner  10  can be ensured. 
     (3) The power monitoring device  33  outputs the reset signal β to the controller  13  after a fixed time elapses from the interruption of the power of the power source unit  31  (occurrence of a power failure), and the fixed time is set to such a time that when the power failure occurs in the refrigerant-compressing process of the compressor  16 , the compressor does not start to rotate in the reverse direction by even the repulsive force of the compressed refrigerant. Therefore, in the short-term power failure in which the power interruption state is continued even when the fixed time elapses from the occurrence of the power failure, the compressor starts to rotate in the reverse direction, however, the controller  13  is reset and thus no operating signal α is output to the compressor  16 , so that the reverse phenomenon of the compressor  16  can be surely prevented. 
     On the other hand, in the extremely-short-term power failure in which the power interruption state is finished before the fixed time elapses from the occurrence of the power failure, no reset signal β is output from the pulse monitoring circuit  38  of the power monitoring device  33  to the controller  13 , and the compressor  16  does not start to rotate in the reverse direction during this period. Therefore, the compressor  16  is continued to rotated in the normal direction even after the extremely-short-term power failure is finished, so that the operation performance of the air conditioner  10  can be prevented from being lowered. 
     The present invention is not limited to the above embodiment, and various modifications may be made without departing from the subject of the present invention. 
     For example, in the above embodiment, the pulse generating circuit  37  of the power monitoring device  33  generates the pulses on the basis of the power of the power source unit  31 . However, the pulses may be generated on the basis of the power of the transformer  34  of the power converting device  32 . Further, the power monitoring device  33  may directly monitor the variation of the voltage of the power source unit without transforming the power of the power source unit  31  or the transformer  34  to pulses. 
     According to the compressor control system for the air conditioner according to the present invention, the power monitoring device monitors the power state of the power source unit, and outputs the reset signal to the controller for controlling the operation of the compressor when the power supply of the power source unit is intercepted. The controller is reset by the reset signal to stop the compressor. Therefore, even when the power failure occurs in the refrigerant-compressing process of the compressor, the reverse rotation phenomenon of the compressor can be surely prevented.