BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a hermetic compressor driving device. 
         [0003]    2. Description of the Related Art 
         [0004]    A conventional driving device for a hermetic compressor including a motor and a compression mechanism unit is exemplified by a driving device that converts an alternating current of a commercial alternating-current power supply into a direct current; uses a switching circuit to convert the converted direct current into a three-phase pseudo alternating current; and then applies the three-phase pseudo alternating current to the respective phase windings of the motor. In such a driving device, in order to sequentially switch a plurality of phase windings that are connected from the switching circuit to these phase windings, voltages induced in phase windings in a nonconductive state among these phase windings are detected; the rotor position of the motor is detected by using the detected voltages; and the switching timing of the switching circuit is controlled according to the detected position. Such a driving device includes a normally open contact that is closed when the pressure or temperature in a hermetic case (a hermetic compressor) abnormally increases and a current limiting element that is directly connected to the normally open contact. In this driving device, when the pressure or temperature abnormally increases, any of two unconnected phase windings among the respective phase windings are connected to each other; an overload current in a current flowing via the current limiting element is detected; and then the switching operation of the inverter is stopped, thereby preventing the pressure or temperature of the hermetic compressor from abnormally increasing. 
         [0005]    For example, Japanese Patent Application Laid-open No. 2009-156236 discloses a compressor driving device in which, when the pressure in a hermetic compressor abnormally increases, a normally open contact and a current limiting element included in a protection device in the hermetic compressor are activated so that the compressing operation of the hermetic compressor is stopped, thereby controlling the pressure in the hermetic compressor so as not to increase more than a predetermined value. Japanese Patent Application Laid-open No. 2009-156236 also discloses a technique in which, when the normally open contact of the compressor driving device is operated, as the current limiting element in the hermetic compressor is connected with the windings, a short path passing through a switching element and the current limiting element is formed between bus voltages. 
         [0006]    However, according to the conventional technique described above, even when a refrigerant load is temporarily increased, the normally open contact is operated in accordance with the pressure increase in the hermetic compressor, and thus an overload current flows through a switching element of the switching circuit via the current limiting element. Therefore, a case occurs where the current limiting element within the hermetic compressor and the switching element of the switching circuit are damaged. As a result, with the conventional technique, there is a problem in that, although a temporal increase of a refrigerant load is the cause of the pressure increase, a circuit board or the hermetic compressor still needs to be replaced or repaired. 
         [0007]    When a hermetic compressor having an HPS (High Pressure Switch) incorporated therein is used to stop operations safely, phase windings are opened when the pressure within the hermetic compressor reaches a predetermined value or more. Therefore, even when the pressure increase is due to a temporal increase in the refrigerant load, there is a problem in that the pressure within the hermetic compressor is increased and the HPS does not operate in a desirable way. 
       SUMMARY OF THE INVENTION 
       [0008]    It is an object of the present invention to at least partially solve the problems with the conventional technology. 
         [0009]    The present invention relates to a hermetic compressor driving device that drives a hermetic compressor provided with a high pressure switch therein. The hermetic compressor driving device includes: a parameter detection unit that detects an overcurrent, a bus voltage, and an open phase that are generated when an opening operation of the high pressure switch provided within the hermetic compressor is performed; a temperature detection unit that detects a temperature of the hermetic compressor; and a control unit to which data acquired by the parameter detection unit and the temperature detection unit is input. The control unit, when detecting an abnormality on the basis of the data, determines whether or not the abnormality is a resumable abnormality, when determining that the abnormality is a resumable abnormality, outputs a drive signal again, and when determining that the abnormality is not a resumable abnormality, outputs an abnormality signal so as to stop the driving of the hermetic compressor. 
         [0010]    The above and other objects, features, advantages and technical and industrial significance of this invention will be better understood by reading, and considering in connection with the accompanying drawings, the following detailed description of presently preferred embodiments of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a diagram illustrating an example of a configuration of a hermetic compressor driving device according to an embodiment of the present invention; and 
           [0012]      FIGS. 2A and 2B  are a flowchart showing an example of the control performed when detecting an abnormality in the hermetic compressor driving device according to the embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0013]    Exemplary embodiments of a hermetic compressor driving device according to the present invention will be described below in detail with reference to the accompanying drawings. The present invention is not limited to the embodiments. 
       Embodiment 
       [0014]      FIG. 1  is a diagram illustrating an example of a configuration of a hermetic compressor driving device according to an embodiment of the present invention. A hermetic compressor driving device  10 , connected to a commercial alternating-current power supply  1 , drives a hermetic compressor  20 . 
         [0015]    The hermetic compressor  20  includes phase windings  21 ,  22 , and  23  and a High Pressure Switch (HPS)  24 . The hermetic compressor  20  has a mechanism in which, when the pressure in the hermetic compressor  20  becomes larger than a predetermined value (a threshold), the HPS  24  mechanically opens any one phase of or all three phases of the phase windings  21 ,  22 , and  23 , and the compressing operation of the hermetic compressor  20  is mechanically stopped; and then, when the pressure again becomes less than the predetermined value (the threshold), the phase windings  21 ,  22 , and  23  are reconnected and driving of the hermetic compressor  20  can be resumed. Here, the predetermined value (the threshold) can be a constant value, or it can be a value that varies with hysteresis. 
         [0016]    The hermetic compressor driving device  10  includes a power rectifier unit  11 , a voltage detection unit  12 , an overcurrent detection unit  13 , a control unit  14 , a switching circuit  15 , and a position and open-phase detection unit  16 . The power rectifier unit  11  is a rectifier that converts an alternating current of the commercial alternating-current power supply  1  into a direct current. The voltage converted into a direct current is applied to the switching circuit  15  via the voltage detection unit  12  and the overcurrent detection unit  13 . The voltage detection unit  12  detects a voltage between buses and outputs the detected voltage to the control unit  14 . The overcurrent detection unit  13  detects a current flowing in the switching circuit  15  and outputs the detected current to the control unit  14 . 
         [0017]    The switching circuit  15  includes switching elements  15   a (U+),  15   b (V+),  15   c (W+),  15   d (U−),  15   e (V−), and  15   f (W−); converts a direct-current voltage that is input thereto into a three-phase pseudo alternating-current voltage; and outputs the converted voltage. The phase winding  21  is connected between the switching elements  15   a (U+) and  15   d (U−); the phase winding  22  is connected between the switching elements  15   b (V+) and  15   e (V−); and the phase winding  23  is connected between the switching elements  15   c (W+) and  15   f (W−). 
         [0018]    The position and open-phase detection unit  16  is connected to a conduction line disposed between the switching circuit  15  and the hermetic compressor  20 . The position and open-phase detection unit  16  detects voltages induced in phase windings in a nonconductive state among the phase windings  21 ,  22 , and  23 ; detects, depending on the detected voltages, the rotation position of a rotor within the hermetic compressor  20 ; and outputs the detected rotation position of the rotor to the control unit  14 . 
         [0019]    A temperature detection element  30  is connected to (the outside of) the hermetic compressor  20 ; and a temperature detection unit  17  detects the temperature of the hermetic compressor  20  using the temperature detection element  30 , and the detected temperature is output to the control unit  14 . The power rectifier unit  11 , the control unit  14 , the switching circuit  15 , and the position and open-phase detection unit  16  constitute an inverter that supplies a drive voltage to the phase windings  21 ,  22 , and  23  of the hermetic compressor  20 . 
         [0020]    The control unit  14  supplies a drive signal for controlling the switching ON and OFF of at least the switching elements  15   a  to  15   f  that are included in the switching circuit  15 , and it stops the supply of the drive signal to the switching elements  15   a  to  15   f  when an abnormality is detected. The drive signal is generated according to detection results of respective detection units input to the control unit  14 . Here, examples of the time of detecting an abnormality include the time when an open phase was detected by the position and open-phase detection unit  16 ; a time when an abnormality in a bus voltage was detected by the voltage detection unit  12 ; or a time when an overcurrent was detected by the overcurrent detection unit  13 . 
         [0021]    As described above, when there is an abnormality in which the pressure in the hermetic compressor  20  is larger than a predetermined value (a threshold), the HPS  24  is operated and the compressing operation of the hermetic compressor  20  is mechanically stopped. Exemplifications of when the HPS  24  is operating in this way can be a case in which an open phase in a compressor winding occurs (when detecting an open phase), a case in which an abnormality in a bus voltage occurs (when detecting an abnormality in a bus voltage), or a case in which an abnormality in a compressor drive current occurs (when detecting an overcurrent). 
         [0022]    The position and open-phase detection unit  16  detects, by using a current sensor (not illustrated), a current flowing in the phase windings  21 ,  22 , and  23  when the switching elements  15   a  to  15   f  of the switching circuit  15  are driven. The control unit  14  determines the position and the open phase according to the current detected by the current sensor. When the HPS  24  is operated, the phase windings  21 ,  22 , and  23  are opened, and thus no current flows in the phase windings  21 ,  22 , and  23  even when the switching elements  15   a  to  15   f  are driven (for example, a current of 0 amperes is output from the position and open-phase detection unit  16 ). Accordingly, it is determined that an open phase abnormality has occurred. 
         [0023]    The control unit  14  monitors the value of a bus voltage output from the voltage detection unit  12 ; and when the value of the bus voltage is not within a predetermined range, it is determined that a bus voltage abnormality has occurred. 
         [0024]    The overcurrent detection unit  13  monitors the current flowing in the switching circuit  15  that operates as an inverter; and when the current exceeds a predetermined value, the overcurrent detection unit  13  outputs a signal to the control unit  14  and the control unit  14  determines that an overcurrent abnormality has occurred. 
         [0025]      FIG. 2  is a flowchart illustrating an example of the control performed when detecting an abnormality in the hermetic compressor driving device according to the embodiment of the present invention. First, the process starts to cause the hermetic compressor driving device  10  to drive the hermetic compressor  20  (Step S 1 ). After driving the hermetic compressor  20 , the control unit  14  acquires data (such as data indicating positions and any open phases, currents, voltages, and currents flowing in the phase windings  21 ,  22 , and  23 ) from the voltage detection unit  12 , the overcurrent detection unit  13 , and the position and open-phase detection unit  16  (Step S 2 ). 
         [0026]    Subsequently, the control unit  14  determines whether a current (a circuit current) flowing in the switching circuit  15  is equal to or less than an overcurrent threshold (Step S 3 ). As a result of the determination at Step S 3 , when it is determined that the current (the circuit current) flowing in the switching circuit  15  is equal to or less than the overcurrent threshold (YES at Step S 3 ), the control unit  14  determines whether a bus voltage is within a threshold (including the case where the bus voltage is equal to the threshold) (Step S 4 ). When, as a result of the determination at Step S 3 , it is determined that the current (the circuit current) flowing in the switching circuit  15  is not equal to or less than the overcurrent threshold (NO at Step S 3 ), the control unit  14  detects an overcurrent abnormality (Step S 8 ). 
         [0027]    When, as a result of the determination at Step S 4 , it is determined that the bus voltage is within the threshold (YES at Step S 4 ), the control unit  14  determines whether a compressor current (a current flowing in the phase windings  21 ,  22 , and  23 ) is 0 amperes (Step S 5 ). When, as a result of the determination at Step S 4 , it is determined that the bus voltage is not within the threshold (NO at Step S 4 ), the control unit  14  detects a bus voltage abnormality (Step S 7 ). 
         [0028]    When, as a result of the determination at Step S 5 , it is determined that the compressor current (the current flowing in the phase wirings  21 ,  22 , and  23 ) is 0 amperes (YES at Step S 5 ), the control unit  14  detects an open phase abnormality (Step S 6 ). When, as a result of the determination at Step S 5 , it is determined that the compressor current (the current flowing in the phase wirings  21 ,  22 , and  23 ) is not 0 amperes (NO at Step S 5 ), the process returns to Step S 2  and data acquisition is performed. 
         [0029]    Note that the order of the determinations at Steps S 3 , S 4 , and S 5  is not limited to the above example. That is, the determinations can be performed with the following orders of Steps: Steps S 3 , S 5 , and S 4 , Steps S 4 , S 3 , and S 5 , Steps S 4 , S 5 , and S 3 , Steps S 5 , S 3 , and S 4 , or Steps S 5 , S 4 , and S 3 . 
         [0030]    When an open phase abnormality is detected (Step S 6 ), assumed problems include, for example, disconnection of the phase windings  21 ,  22 , and  23  of the hermetic compressor  20 ; disconnection of wirings in the hermetic compressor driving device  10 ; a malfunction of the hermetic compressor  20 ; a malfunction of an inverter substrate of the hermetic compressor driving device  10 ; and an undesirable operation of the HPS  24 . If the open phase abnormality is assumed to be due to an operation of the HPS  24  and if the open phase abnormality is caused by a pressure increase of the hermetic compressor  20  due to a temporal refrigerant increase, it is not a malfunction; therefore any repairing or replacing work is not necessary. In this manner, in a case where any repairing or replacing work is not necessary, driving of the hermetic compressor  20  can be resumed. 
         [0031]    When an open phase abnormality is detected (Step S 6 ), the control unit  14  determines whether the time after starting the driving of the hermetic compressor  20  (Step S 1 ) is equal to or less than a predetermined time (a threshold time) (Step S 9 ). In this case, the threshold time is 3 minutes, for example. As a result of the determination at Step S 9 , when it is determined that the time after starting the driving (activating) of the hermetic compressor  20  is equal to or less than the threshold time (3 minutes, for example) (when YES at Step S 9 ), the control unit  14  determines that there is an early abnormality (faulty wiring or disconnection) (Step S 10 ); and in order not to resume the driving of the hermetic compressor  20 , the control unit  14  outputs an abnormality signal to an external destination (Step S 30 ), and the process is ended. Due to the output of the abnormality signal, a user recognizes the presence of an abnormality and handles the abnormality by repairing, replacement, and the like. 
         [0032]    As a result of the determination at Step S 9 , when it is determined that the time after starting the driving (activating) of the hermetic compressor  20  is not within the threshold time (3 minutes, for example) (NO at Step S 9 ), the cause of the open phase abnormality is not an early abnormality; and it is assumed that the cause is a malfunction of the hermetic compressor  20  during driving or an operation of the HPS  24 . In this case, when the HPS  24  is operated, the pressure in the hermetic compressor  20  becomes high and the temperature of the hermetic compressor  20  also becomes high. The temperature detection unit  17  acquires the temperature of the hermetic compressor  20  by the temperature detection element  30  and transmits the acquired temperature to the control unit (Step S 11 ); and then the control unit  14  determines whether the acquired temperature of the hermetic compressor  20  is equal to or larger than a temperature threshold (Step S 12 ). In this case, the temperature threshold of the hermetic compressor  20  is 150° C., for example. 
         [0033]    As a result of the determination at Step S 12 , when it is determined that the temperature of the hermetic compressor  20  is equal to or higher than the temperature threshold (150° C.) (YES at Step S 12 ), the position and open-phase detection unit  16  determines whether there is any open phase in the phase windings  21 ,  22 , and  23  (Step S 13 ); and the control unit  14  determines whether there is any open phase abnormality (Step S 14 ). When the temperature of the hermetic compressor  20  is less than the temperature threshold (NO at Step S 12 ), the control unit  14  determines that there is a malfunction of the hermetic compressor  20  (Step S 15 ), and it outputs an abnormality signal to an external destination (Step S 30 ). Due to the output of the abnormality signal, the user recognizes the presence of an abnormality and handles the abnormality by repairing, replacement, and the like. 
         [0034]    When, as a result of the determination at Step S 14 , it is determined that there is an open phase abnormality (YES at Step S 14 ), the control unit  14  determines whether the time after starting the driving (activating) of the hermetic compressor  20  is equal to or less than a predetermined time (a threshold time of 3 minutes) (Step S 16 ). When, as a result of the determination at Step S 16 , it is determined that the time after starting the driving (activating) of the hermetic compressor  20  is within the predetermined time (the threshold time of 3 minutes) (YES at Step S 16 ), the position and open-phase detection unit  16  checks again as to whether there is any open phase in the phase wirings  21 ,  22 , and  23  (Step S 13 ). This operation means that, until the phase open state is cancelled or until the predetermined time (the threshold time of 3 minutes) elapses after starting the driving (activating) of the hermetic compressor  20 , the operation is repeated to check whether there is any open phase in the phase wirings  21 ,  22 , and  23  (Step S 13 ); to determine whether there is any open phase abnormality (Step S 14 ); and to check whether the determination of the time after starting the driving of the hermetic compressor  20  is equal to or less than the threshold (3 minutes) (Step S 16 ). 
         [0035]    When, as a result of the determination at Step S 14 , the process branches to NO, the control unit  14  determines whether any overcurrent abnormality is detected in the overcurrent detection unit  13  (Step S 17 ). When, as a result of the determination at Step S 17 , it is determined that an overcurrent abnormality is detected (YES at Step S 17 ), the control unit  14  determines that there is a malfunction of the hermetic compressor  20  or a malfunction of an inverter substrate (Step S 18 ), and it outputs an abnormality signal to an outside destination (Step S 30 ). Upon the output of the abnormality signal, the user recognizes an abnormality and handles the abnormality by repairing, replacement, and the like. When, as a result of the determination at Step S 17 , it is determined that no overcurrent abnormality is detected (NO at Step S 17 ), it is assumed that the pressure in the hermetic compressor  20  has increased due to a temporal refrigerant increase and the HPS is operated; and then the control unit  14  determines that driving of the hermetic compressor  20  can be resumed (Step S 19 ), stands by for a predetermined time (3 minutes, for example) (Step S 20 ), and outputs a drive signal again (Step S 21 ). 
         [0036]    Although not illustrated, it is also possible to perform a process of counting the number of times an abnormality [is detected/detection is performed?] in a specified time (30 minutes, for example) after activating the hermetic compressor  20 , and when the counted number exceeds a preset number (three times, for example), it is determined as a malfunction of the hermetic compressor  20  and an abnormality signal is output to an external destination; and when the counted number within the specified time (30 minutes, for example) has not exceeded the preset number (three times, for example), the counted number is reset. Because there is a possibility of faulty wiring and the like occurring before the elapsing of a threshold time after activating the hermetic compressor  20 , an abnormality signal is output to an external destination (Step S 30 ). 
         [0037]    Meanwhile, when the process branches to NO (Step S 7 ) as a result of the determination at Step S 4 , or when the process branches to NO (Step S 8 ) as a result of the determination at Step S 3 , in order to check whether the phase windings  21 ,  22 , and  23  are in a nonconductive state due to an operation of the HPS  24 , the position and open-phase detection unit  16  checks whether there are any open phases in the phase windings  21 ,  22 , and  23  (Step S 22 ); and the control unit  14  determines whether there is any open phase abnormality (Step S 23 ). When, as a result of the determination at Step S 23 , it is determined that there is an open phase abnormality (YES at Step S 23 ), the process proceeds to Step S 11 , and subsequent processes are the same as those described above. As a result of the determination at Step S 23 , when it is determined that there is no open phase abnormality (NO at Step S 23 ), the control unit  14  determines whether there is any overcurrent abnormality (Step S 24 ). When, as a result of the determination at Step S 24 , the process branches to YES, the control unit  14  determines that there is an overcurrent abnormality (Step S 25 ), and outputs an abnormality signal to an external destination (Step S 30 ). 
         [0038]    When, as a result of the determination at Step S 24 , the process branches to NO, there is a high possibility that the hermetic compressor  20  has been affected by fluctuations of the commercial alternating-current power supply  1 ; and thus the control unit  14  determines whether the bus voltage is abnormal (Step S 26 ). When, as a result of the determination at Step S 26 , the process branches to YES, the control unit  14  determines whether the number of detections (abnormality detections) is equal to or less than a preset number of times (ten times, for example) (Step S 27 ). When, as a result of the determination at Step S 27 , it is determined that the number of detections is equal to or less than the preset number of times (ten times, for example) (YES at Step S 27 ), it is again determined whether the bus voltage is abnormal (Step S 26 ). When, as a result of the determination at Step S 27 , it is determined that the number of detections exceeds the preset number of times (ten times, for example) (NO at Step S 27 ), the control unit  14  determines that there is an abnormality in the bus voltage (Step S 28 ) and outputs an abnormality signal to an external destination (Step S 30 ). 
         [0039]    When, as a result of the determination at Step S 26 , the process branches to NO, that is, when the determination has ended before the number of detections reaches a preset number of times (NO at Step S 26  after YES at Step S 27 ), the control unit  14  determines that driving of the hermetic compressor  20  can be resumed (Step S 29 ), stands by for a predetermined time (a threshold time of 3 minutes) (Step S 20 ), and outputs a drive signal again (Step S 21 ). 
         [0040]    Although not illustrated, also in this case, it is possible to perform a process in which the number of abnormality detections in a specified time (30 minutes, for example) after activating the hermetic compressor  20  is counted, and when the counted number exceeds a preset number (three times, for example), it is determined there is a malfunction of the hermetic compressor  20  and an abnormality signal is output to an external destination; and when the counted number within the specified time (30 minutes, for example) has not exceeded the preset number (three times, for example), the counted number is reset. Because there is a possibility of faulty wiring and the like occurring before the elapsing of a threshold time after activating the hermetic compressor  20 , an abnormality signal is output to an external destination (Step S 30 ). 
         [0041]    As described above, according to the above embodiment, when there is an abnormality, it is possible, for example, to determine whether either it is an abnormality that is caused by a temporal increase of a refrigerant load and it is thus an abnormality that allows driving of the hermetic compressor to be resumed or it is an abnormality that requires repair or replacement. While the hermetic compressor driving device described in the present embodiment is suitable for an air conditioner, the application of the present invention is not limited thereto, and the invention can be also applied to other types of devices that are connected to an alternating-current power supply and include a hermetic compressor. 
         [0042]    The present invention is not limited to the configurations described in the above embodiment; and additions, modifications, and omissions to or from the configuration can be made without departing from the scope of the invention. 
         [0043]    According to the present invention, it is possible to obtain a hermetic compressor driving device that determines whether an operation of an HPS is due to a pressure increase caused by a temporal increase of a refrigerant load; and that, if it is a pressure increase caused by a temporal increase of a refrigerant load, can resume the driving of a hermetic compressor. 
         [0044]    Although the invention has been described with respect to specific embodiments for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art that fairly fall within the basic teaching herein set forth.
A hermetic compressor driving device, which drives a hermetic compressor provided with an HPS (High Pressure Switch) therein, includes parameter detection units (a voltage detection unit, an overcurrent detection unit, and a position and open-phase detection unit) that detect an overcurrent, a bus voltage, and an open phase, which are generated during the opening operation of the HPS within the hermetic compressor; a temperature detection unit that detects the temperature of the hermetic compressor; and a control unit to which data acquired by the parameter detection units and the temperature detection unit is input. When detecting an abnormality on the basis of the data and upon determining the abnormality as a resumable abnormality, the control unit outputs a drive signal; and, upon determining the abnormality as being not a resumable abnormality, outputs an abnormality signal so as to stop the driving of the hermetic compressor.