Patent Publication Number: US-2021188597-A1

Title: Break detection device

Description:
FIELD 
     The present invention relates to a device for detecting a wire break occurred in a rope. 
     BACKGROUND 
     Various ropes are used in an elevator apparatus. For example, a car of an elevator is suspended by a main rope in a shaft. The main rope is wound around a sheave such as a driving sheave of a traction machine. The main rope is repeatedly bent with movement of the car. Consequently, the main rope gradually deteriorates. When the main rope has deteriorated, wires included in the main rope are broken. When a large number of the wires are broken, a strand made of the wires twisted together may be broken. In the present application, a strand break is also inclusively referred to as a wire break. 
     A broken wire protrudes from a surface of the main rope. As a result, when the elevator is operated in a state where the wire is broken, the broken wire comes into contact with a device provided in the shaft. 
     PTL 1 describes an elevator apparatus. In the elevator apparatus described in PTL 1, a detection member is provided so as to face a main rope. In addition, displacement of the detection member is detected by a sensor. A wire break is detected on the basis of the displacement detected by the sensor. 
     CITATION LIST 
     Patent Literature 
     [PTL 1] JP 4896692 B 
     SUMMARY 
     Technical Problem 
     In an elevator apparatus, for each sheave, a range of a main rope that passes through the sheave is determined in advance. For example, a portion in a certain range of the main rope passes through a driving sheave. The portion that passes through the driving sheave does not necessarily pass through a suspension sheave of a counterweight. Accordingly, when it is attempted to detect a wire break using the sensor described in PTL 1, it is required to mount a sensor at a position of each of the sheaves around which the main rope is wound. For example, when a sensor is mounted at a position of the suspension sheave of the counterweight, a signal line should be connected between the counterweight and a controller. A large number of sensors are required, while a signal line should be led out from each of the sensors, resulting in a problem of a complicated configuration. Particularly in a 2:1 roping elevator apparatus using a large number of sheaves, such a problem is prominent. 
     The invention is made in order to solve such a problem as described above. An object of the invention is to provide a break detection device capable of detecting occurrence of a wire break using a simple configuration. 
     Solution to Problem 
     A break detection device of the present invention comprises a sensor of which an output signal varies when vibration occurs in a rope of an elevator, first extraction means configured to extract, from the output signal from the sensor, a vibration component in a specific frequency band, second extraction means configured to attenuate, from the vibration component extracted by the first extraction means, a steady vibration component and a progressively increasing vibration component to extract a determination signal, first detection means configured to detect, on the basis of the determination signal extracted by the second extraction means, occurrence of an abnormal variation in the output signal from the sensor, and first determination means configured to determine, when the occurrence of the abnormal variation is detected by the first detection means, whether or not the rope has a broken portion on the basis of a position of a car of the elevator at an occurrence time of the abnormal variation. 
     Advantageous Effects of Invention 
     A break detection device according to the invention includes first extraction means, second extraction means, first detection means, and first determination means. The first extraction means extracts, from an output signal from a sensor, a vibration component in a specific frequency band. The second extraction means attenuates, from the vibration component extracted by the first extraction means, a steady vibration component and a progressively increasing vibration component to extract a determination signal. The first detection means detects, on the basis of the determination signal, occurrence of an abnormal variation in the output signal from the sensor. When the occurrence of the abnormal variation is detected by the first detection means, the first determination means determines whether or not a rope has a broken portion on the basis of a position of a car of an elevator at an occurrence time of the abnormal variation. The break detection device according to the invention can detect the occurrence of a wire break using a simple configuration. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a view schematically showing an elevator apparatus. 
         FIG. 2  is a perspective view showing a return sheave. 
         FIG. 3  is a view showing a cross section of the return sheave. 
         FIG. 4  is a view for illustrating movement of a broken portion of a main rope. 
         FIG. 5  is a view for illustrating movement of the broken portion of the main rope. 
         FIG. 6  is a view for illustrating movement of the broken portion of the main rope. 
         FIG. 7  is a view showing examples of output signals from sensors. 
         FIG. 8  is a view showing examples of the output signals from the sensors. 
         FIG. 9  is a view schematically showing the elevator apparatus. 
         FIG. 10  is a view showing examples of the output signals from the sensors. 
         FIG. 11  is a view in which cross sections of the return sheave are enlarged. 
         FIG. 12  is a view showing examples of the output signals from the sensors. 
         FIG. 13  is a view showing an example of a break detection device in a first embodiment. 
         FIG. 14  is a flow chart showing an operation example of the break detection device in the first embodiment. 
         FIG. 15  is a view for illustrating an example of a function of a first extraction unit. 
         FIG. 16  is a view showing a transition of a variation occurred in a sensor signal. 
         FIG. 17  is a view showing a transition of a variation occurred in a sensor signal. 
         FIG. 18  is a view showing a transition of a variation occurred in a sensor signal. 
         FIG. 19  is a view for illustrating a transition of the variation occurred in the sensor signal. 
         FIG. 20  is a view three-dimensionally showing a transition of the variation occurred in the sensor signal. 
         FIG. 21  is a view for illustrating an example of a function of a second extraction unit. 
         FIG. 22  is a view for illustrating an example of performing the first extraction unit and the second extraction unit. 
         FIG. 23  is a view showing an example of a signal input to a subtractor. 
         FIG. 24  is a view showing an example of a signal input to the subtractor. 
         FIG. 25  is a view showing an example of a signal input to the subtractor. 
         FIG. 26  is a view showing another example which performs a function of the second extraction unit. 
         FIG. 27  is a view for illustrating another example of performing the first extraction unit and the second extraction unit. 
         FIG. 28  is a view for illustrating an example of a reproducibility determining function. 
         FIG. 29  is a view showing a cross section of the return sheave. 
         FIG. 30  is a view showing a car guided by guide rails. 
         FIG. 31  is a view showing another example of the break detection device in the first embodiment. 
         FIG. 32  is a view showing an example of a broken portion. 
         FIG. 33  is a view showing an example of a broken portion. 
         FIG. 34  is a view for illustrating an example of functions of an arithmetic unit and a determination unit. 
         FIG. 35  is a view showing examples of signals input to a subtractor of the second extraction unit. 
         FIG. 36  is a view for illustrating an example of a function of the second extraction unit. 
         FIG. 37  is a view showing an example of the break detection device in a third embodiment. 
         FIG. 38  is a view showing an example of a hardware element included in a controller. 
         FIG. 39  is a view showing another example of the hardware element included in the controller. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The invention will be described with reference to the accompanying drawings. Redundant descriptions will be appropriately simplified or omitted. In the individual drawings, the same reference numerals denote the same or corresponding parts. 
     First Embodiment 
       FIG. 1  is a view schematically showing an elevator apparatus. A car  1  moves vertically in a shaft  2 . For example, the shaft  2  is a vertically extending space formed in a building. A counterweight  3  moves vertically in the shaft  2 . The car  1  and the counterweight  3  are suspended by a main rope  4  in the shaft  2 . A roping method for suspending the car  1  and the counterweight  3  is not limited to an example shown in  FIG. 1 . The car  1  and the counterweight  3  may be suspended in the shaft  2  by 1:1 roping. 
     In the example shown in  FIG. 1 , one end portion  4   a  of the main rope  4  is supported by a fixing member provided in a top portion of the shaft  2 . The main rope  4  extends downward from the end portion  4   a . The main rope  4  is wound, from the end portion  4   a  side, around a suspension sheave  5 , a suspension sheave  6 , a return sheave  7 , a driving sheave  8 , a return sheave  9 , and a suspension sheave  10 . The main rope  4  extends upward from a portion thereof wound around the suspension sheave  10 . The other end portion  4   b  of the main rope  4  is supported by a fixing member provided in the top portion of the shaft  2 . 
     The suspension sheave  5  and the suspension sheave  6  are included in the car  1 . The suspension sheave  5  and the suspension sheave  6  are provided to be rotative with respect to, for example, a member supporting a car floor. The return sheave  7  and the return sheave  9  are provided to be rotative with respect to, for example, a fixing member in the top portion of the shaft  2 . The driving sheave  8  is included in a traction machine  11 . The traction machine  11  is provided in a pit of the shaft  2 . The suspension sheave  10  is included in the counterweight  3 . The suspension sheave  10  is provided to be rotative with respect to, for example, a frame supporting an adjustment weight. 
     A layout of the sheaves around which the main rope  4  is wound is not limited to that in the example shown in  FIG. 1 . For example, the driving sheave  8  may be disposed in the top portion of the shaft  2 . The driving sheave  8  may be disposed in a machine room (not shown) above the shaft  2 . 
     A load weighing device  12  detects a load of the car  1 . In the example shown in  FIG. 1 , the load weighing device  12  detects the load of the car  1  on the basis of a load applied to the end portion  4   a  of the main rope  4 . The load weighing device  12  outputs a load signal corresponding to the detected load. The load signal output from the load weighing device  12  is input to a controller  13 . 
     The traction machine  11  has a function of detecting a torque. The traction machine  11  outputs a torque signal corresponding to the detected torque. The torque signal output from the traction machine  11  is input to the controller  13 . 
     The controller  13  controls the traction machine  11 . The controller  13  arithmetically determines a command value for a rotation speed of the driving sheave  8 . In the traction machine  11 , the rotation speed of the driving sheave  8  is measured. An actually measured value of the rotation speed of the driving sheave  8  is input from the traction machine  11  to the controller  13 . In the controller  13 , a speed deviation signal corresponding to a difference between the command value for the rotation speed of the driving sheave  8  and the actually measured value is generated. 
     A governor  15  operates a safety gear (not shown) when a descending speed of the car  1  exceeds a reference speed. The safety gear is included in the car  1 . When the safety gear is operated, the car  1  is forcibly stopped. The governor  15  includes, for example, a governor rope  16 , a governor sheave  17 , and an encoder  18 . The governor rope  16  is coupled to the car  1 . The governor rope  16  is wound around the governor sheave  17 . When the car  1  moves, the governor rope  16  moves. When the governor rope  16  moves, the governor sheave  17  rotates. The encoder  18  outputs a rotation signal corresponding to a rotation direction and a rotation angle of the governor sheave  17 . The rotation signal output from the encoder  18  is input to the controller  13 . The encoder  18  is an example of a sensor configured to output a signal corresponding to a position of the car  1 . 
       FIG. 2  is a perspective view showing the return sheave  7 .  FIG. 3  is a view showing a cross section of the return sheave  7 . A rope guide  19  is provided on a member supporting the return sheave  7 . In an example shown in  FIGS. 2 and 3 , the rope guide  19  is provided on a shaft  7   a  of the return sheave  7 . The rope guide  19  prevents the main rope  4  from being detached from a groove of the return sheave  7 . The rope guide  19  faces the main rope  4  with a given gap being provided therebetween. 
     The rope guide  19  includes, for example, a facing portion  19   a  and a facing portion  19   b . The facing portion  19   a  faces a portion of the main rope  4  which draws apart from the groove of the return sheave  7 . The facing portion  19   b  faces the other portion of the main rope  4  which draws apart from the groove of the return sheave  7 . The return sheave  7  is used to change a direction in which the main rope  4  is moved by 180 degrees. Accordingly, the facing portion  19   a  and the facing portion  19   b  are disposed on both sides of the return sheave  7 . Unless an abnormality occurs in the main rope  4 , the main rope  4  does not come into contact with the rope guide  19 . 
       FIGS. 2 and 3  show the example in which a broken portion  4   c  protrudes from a surface of the main rope  4 . The main rope  4  is formed of a plurality of strands twisted together. Each of the strands is formed of a plurality of wires twisted together. The broken portion  4   c  is a portion with a wire break. The broken portion  4   c  may be a portion with a strand break. When the car  1  moves, the broken portion  4   c  passes through the return sheave  7 . The broken portion  4   c  comes into contact with the rope guide  19  when passing through the return sheave  7 . 
       FIGS. 2 and 3  show the return sheave  7  as an example of the sheaves around which the main rope  4  is wound. A rope guide may be provided on another sheave such as the suspension sheave  5 . A rope guide may be provided on another sheave not shown in  FIG. 1 . 
       FIGS. 4 to 6  are views for illustrating movement of the broken portion  4   c  of the main rope  4 .  FIG. 4  shows a state where the car  1  is stopped at a hall on a lowermost floor. In the state where the car  1  is stopped at the hall on the lowermost floor, the broken portion  4   c  is present between the end portion  4   a  of the main rope  4  and a portion thereof wound around the suspension sheave  5 . 
       FIG. 6  shows a state where the car  1  is stopped at a hall on an uppermost floor. In the state where the car  1  is stopped at the hall on the uppermost floor, the broken portion  4   c  is present between a portion of the main rope  4  wound around the return sheave  7  and a portion thereof wound around the driving sheave  8 . In other words, when the car  1  moves from the hall on the lowermost floor to the hall on the uppermost floor, the broken portion  4   c  passes through the suspension sheave  5 , the suspension sheave  6 , and the return sheave  7 . Even when the car  1  moves from the hall on the lowermost floor to the hall on the uppermost floor, the broken portion  4   c  does not pass through the driving sheave  8 , the return sheave  9 , and the suspension sheave  10 . The broken portion  4   c  does not necessarily pass through all the sheaves. A combination of the sheaves through which the broken portion  4   c  passes is determined by a location at which the broken portion  4   c  appears and the like. 
       FIG. 5  shows a state where the car  1  has moved halfway from the hall on the lowermost floor to the hall on the uppermost floor. In the state shown in  FIG. 5 , a portion of the main rope  4  wound around the suspension sheave  5  has the broken portion  4   c . The broken portion  4   c  comes into contact with the rope guide for the suspension sheave  5  when passing through the suspension sheave  5 . 
       FIG. 7  is a view showing examples of output signals from sensors. In a description given below, a signal output from a sensor is referred to also as a sensor signal.  FIG. 7( a )  shows a position of the car  1 . In an example shown in the present embodiment, the car  1  moves only vertically. Accordingly, a position of the car  1  is synonymous with a height at which the car  1  is present.  FIG. 7( a )  shows a change in car position when the car  1  moves from the lowermost floor to a position P and then returns to the lowermost floor. In  FIG. 7( a ) , the car position on the lowermost floor is 0. A waveform shown in  FIG. 7( a )  is acquired on the basis of the rotation signal from the encoder  18 . 
       FIG. 7( b )  shows an example of a sensor signal  FIG. 7( b )  shows a torque of the traction machine  11 .  FIG. 7( b )  shows a waveform of the torque signal output from the traction machine  11  when the car  1  moves between the lowermost floor and the position P. In  FIG. 7( b ) , a maximum torque is T q1 , while a minimum torque is −T q2 . 
       FIG. 7( c )  shows an example of a sensor signal.  FIG. 7( c )  shows a speed deviation of the rotation speed of the driving sheave  8 .  FIG. 7( c )  shows a waveform of the speed deviation signal generated in the controller  13  when the car  1  moves between the lowermost floor and the position P. 
       FIG. 7( d )  shows an example of a sensor signal  FIG. 7( d )  shows the load of the car  1 .  FIG. 7( d )  shows a waveform of the load signal output from the load weighing device  12 .  FIG. 7( d )  shows an example in which the load of the car  1  is w [kg]. 
       FIGS. 7( b ) to 7( d )  show the waveforms of ideal sensor signals. However, in real sensor signals, variations are caused by various factors. The following will describe the variations caused in the sensor signals. 
       FIG. 8  is a view showing examples of the output signals from the sensors.  FIG. 8( a )  is a view corresponding to  FIG. 7( a ) .  FIG. 8( b )  is a view corresponding to  FIG. 7( b ) .  FIG. 8( c )  is a view corresponding to  FIG. 7( c ) .  FIG. 8( d )  is a view corresponding to  FIG. 7( d ) .  FIG. 8  shows examples of waveforms obtained when the main rope  4  has the broken portion  4   c.    
     The broken portion  4   c  passes through a given sheave when the car  1  passes through a position P 1 . For example, the broken portion  4   c  passes through the return sheave  7  when the car  1  passes through the position P 1 . The broken portion  4   c  comes into contact with the rope guide  19  when passing through the return sheave  7 . As a result, when the car  1  passes through the position P 1 , vibration occurs in the main rope  4 . When the end portion  4   a  of the main rope  4  is displaced, the load signal output from the load weighing device  12  is affected thereby. That is, when the vibration occurred in the main rope  4  reaches the end portion  4   a , a variation occurs in the load signal from the load weighing device  12 . 
     Likewise, when a portion of the main rope  4  wound around the driving sheave  8  is displaced, rotation of the driving sheave  8  is affected thereby. Accordingly, when the vibration occurred in the main rope  4  reaches the portion of concern, a variation occurs in the speed deviation signal generated in the controller  13 . Also, when the portion of the main rope  4  wound around the driving sheave  8  is displaced, the torque signal output from the traction machine  11  is affected thereby. Consequently, when the vibration occurred in the main rope  4  reaches the portion of concern, a variation occurs in the torque signal from the traction machine  11 . 
     Thus, when the main rope  4  has the broken portion  4   c , variations may occur in the sensor signals. The variations in the sensor signals resulting from the broken portion  4   c  repeatedly occur at the same car position. In addition, the broken portion  4   c  suddenly appears as a result of a wire break. Consequently, the variations in the sensor signals resulting from the broken portion  4   c  suddenly occur. 
       FIG. 9  is a view schematically showing the elevator apparatus. In  FIG. 9 , illustration of the controller  13  and the governor  15  is omitted. The movement of the car  1  is guided by guide rails provided in the shaft  2 . Each of the guide rails includes a large number of rail members  20  each having the same length. A large number of the rail members  20  are vertically connected to allow each of the guide rails to be disposed to cover a movement range of the car  1 . Note that it is not necessary for all the rail members  20  included in the guide rails to have the same length. Each of the guide rails has joints between the rail members  20 . 
     When oil supplied to the guide rails is depleted, the car  1  slightly swings when passing through a joint between the rail members  20 . As described above, the main rope  4  is wound around the suspension sheave  5  and the suspension sheave  6 . Accordingly, when the car  1  swings, vibration occurs in the main rope  4 . When the oil supplied to the guide rails is depleted, variations occur in the sensor signals when the car  1  passes through the joint between the rail members  20 . When the joint between the rail members  20  have level differences, larger variations occur in the sensor signals. 
       FIG. 10  is a view showing examples of the output signals from the sensors.  FIG. 10( a )  is a view corresponding to  FIG. 7( a ) .  FIG. 10( b )  is a view corresponding to  FIG. 7( b ) .  FIG. 10( c )  is a view corresponding to  FIG. 7( c ) .  FIG. 10( d )  is a view corresponding to  FIG. 7( d ) .  FIG. 10  shows examples of waveforms obtained when the oil supplied to the guide rails is depleted. 
     The car  1  passes through a given one of the joints between the rail members  20  at a position P 2 . When the car  1  passes through this joint, the car  1  slightly swings. As a result, vibration occurs in the main rope  4  to cause a variation in the load signal from the load weighing device  12 . Likewise, when the car  1  passes through the position P 2 , a variation occurs in the speed deviation signal generated in the controller  13 . When the car  1  passes through the position P 2 , a variation occurs in the torque signal from the traction machine  11 . 
     Thus, when an amount of the oil supplied to the guide rails is reduced, variations may occur in the sensor signals when the car  1  passes through any of the joints between the rail members  20 . The variations in the sensor signals resulting from the joint between the rail members  20  repeatedly occur at the same car position. In addition, since the amount of the oil on a surface of each of the guide rails gradually decreases, the variations of the sensor signals resulting from the joint between the rail members  20  increase with a lapse of time. 
       FIG. 11  is a view in which cross sections of the return sheave  7  are enlarged.  FIG. 11( a )  is a view corresponding to a cross section along a line A-A in  FIG. 3 .  FIG. 11( a )  shows an example in which a groove formed in the return sheave  7  is abraded. In  FIG. 11( a ) , a center of the main rope  4  before the groove is abraded is denoted by a reference mark o, while the center of the main rope  4  when the groove is abraded is denoted by a reference mark o′. As shown in  FIG. 11( a ) , when the groove formed in the return sheave  7  is abraded, a position through which the main rope  4  passes is shifted. A shift in the position through which the main rope  4  passes is caused also by displacement of the shaft  7   a  of the return sheave  7 .  FIG. 11( b )  shows a cross section when the return sheave  7  is cut in a direction perpendicular to the shaft  7   a . In  FIG. 11( b ) , a shape of the return sheave  7  before the groove is abraded is denoted by a reference mark r, while the shape of the return sheave  7  after the groove is abraded is denoted by a reference mark r′. Before the groove is abraded, the return sheave  7  has a circular cross section. On the other hand, when the groove around which the main rope  4  is wound is unevenly abraded, the return sheave  7  no longer has the circular cross section, as shown in  FIG. 11( b ) . Accordingly, when the groove is unevenly abraded, the return sheave  7  is rotated to shift the position through which the main rope  4  passes. When the groove is unevenly abraded, the position through which the main rope  4  passes varies depending on an angle of the rotation of the return sheave  7 . 
     When the position through which the main rope  4  passes is shifted, vibration occurs in the main rope  4  every time the return sheave  7  rotates. Specifically, when the groove formed in the return sheave  7  is abraded, variations occur in the sensor signals when the car  1  moves. When the shaft  7   a  of the return sheave  7  is shifted, variations occur in the sensor signals when the car  1  moves. 
       FIG. 12  is a view showing examples of the output signals from the sensors.  FIG. 12( a )  is a view corresponding to  FIG. 7( a ) .  FIG. 12( b )  is a view corresponding to  FIG. 7( b ) .  FIG. 12( c )  is a view corresponding to  FIG. 7( c ) .  FIG. 12( d )  is a view corresponding to  FIG. 7( d ) .  FIG. 12  shows examples of waveforms when the groove formed in the return sheave  7  is abraded. 
     When the groove formed in the return sheave  7  is abraded, the movement of the car  1  causes vibration in the main rope  4 . This causes a variation in the load signal from the load weighing device  12 . Likewise, when the car  1  moves, a variation occurs in the speed deviation signal generated in the controller  13 . When the car  1  moves, a variation occurs in the torque signal from the traction machine  11 . 
     When abnormality thus occurs in a sheave, the movement of the car  1  may cause variations in the sensor signals. Such variations in the sensor signals resulting from the abnormality in the sheave occur irrespective of the car position.  FIG. 12  shows only variations observed in the sensor signals when the car  1  moves in a given section. Note that, when attention is focused only on a specific car position, the variations in the sensor signals resulting from the abnormality in the sheave repeatedly occur. In addition, since the abrasion of the groove gradually advances, the variations in the sensor signals resulting from the abnormality in the sheave increase with a lapse of time. 
     Factors causing variations in the sensor signals are not limited to the examples shown above. Since the main rope  4  is wound around the sheaves, there is friction between the main rope  4  and the sheaves. There is also friction between guide members included in the car  1  and the guide rails. As a result, mere movement of the car  1  causes variations resulting from such friction in the sensor signals. Note that, when attention is focused only on the specific car position, the variations in the sensor signals resulting from friction repeatedly occur. The variations in the sensor signals resulting from friction are similar to a DC component and do not increase with a lapse of time. 
       FIG. 13  is a view showing an example of a break detection device in a first embodiment. The controller  13  includes, for example, a storage unit  21 , an extraction unit  22 , an extraction unit  23 , a detection unit  24 , a car position detection unit  25 , a determination unit  26 , an operation control unit  27 , and a notification unit  28 .  FIG. 13  shows an example in which the controller  13  has a function of detecting the broken portion  4   c  present in the main rope  4 . It may be possible that a dedicated device for detecting the broken portion  4   c  is included in the elevator apparatus. Referring also to  FIGS. 14 to 28 , the following will specifically describe functions and operations of the break detection device.  FIG. 14  is a flow chart showing an operation example of the break detection device in the first embodiment. 
     The extraction unit  22  extracts, from a sensor signal, a vibration component in a specific frequency band (S 101 ). In the example shown in the present embodiment, each of the load signal, the speed deviation signal, and the torque signal can be used as the sensor signal. In another example, an acceleration signal from an acceleration meter (not shown) provided in the car  1  may be used as the sensor signal. The following will specifically describe an example in which the torque signal is used as the sensor signal. In Step S 101 , the extraction unit  22  extracts, from the torque signal, the vibration component in the specific frequency band. 
     For example, when the broken portion  4   c  shown in  FIG. 3  comes into contact with the rope guide  19 , an abnormal variation appears in the torque signal from the traction machine  11 . The abnormal variation has a vibration component in a particular frequency band corresponding to a length of the broken portion  4   c  and to a moving speed of the main rope  4 . When it is assumed that the length of the broken portion  4   c  is d [m] and the moving speed of the main rope  4  is v [m/s], a frequency f [Hz] of an abnormal vibration is given by the follow expression. 
       [Math. 1] 
         f=v/d   (1)
 
       FIG. 15  is a view for illustrating an example of a function of a first extraction unit. In the example shown in the present embodiment, the first extraction unit is the extraction unit  22 . The extraction unit  22  includes, for example, a band-pass filter  32 . For a simpler description, in the drawings and the like, the band-pass filter is referred to also as BPF. The torque signal from the traction machine  11  is input to the band-pass filter  32 . The band-pass filter  32  extracts, from the torque signal input thereto, the vibration component in the specific frequency band including the frequency f. The length d of the broken portion  4   c  is set in advance. For example, when the strand corresponding to 0.5 pitches to several pitches is raveled, a length of the raveled strand is set as the length d. The moving speed v is determined on the basis of the moving speed of the car  1 . For example, the moving speed v of the main rope  4  can be calculated from a rated speed of the car  1 . 
     As shown in  FIG. 15 , the extraction unit  22  may further include an amplifier  33 . For example, the amplifier  33  squares a signal u. In the extraction unit  22 , it may be possible to determine a square root of a signal u 2  output from the amplifier  33 . In the extraction unit  22 , it may be possible to obtain an absolute value of the signal u and add a positive sign to the signal. In the following description, a signal output from the extraction unit  22  is referred to as an output signal Y. When the extraction unit  22  includes the band-pass filter  32 , the signal output from the extraction unit  22  is referred to also as the output signal Y from the band-pass filter  32 . 
       FIG. 15  shows an example in which the extraction unit  22  includes the band-pass filter  32  to perform a filtering process on the torque signal input thereto. The extraction unit  22  may include a non-linear filter to extract the vibration component in the specific frequency band. It may be possible to apply an algorithm for an adoptive filter to the extraction unit  22  and extract the vibration component in the specific frequency band. 
     The extraction unit  23  extracts, from the vibration component extracted by the extraction unit  22 , a determination signal (S 102 ). The determination signal is a signal necessary for determining occurrence of a sudden variation in the sensor signal. The extraction unit  23  attenuates a trend component from the vibration component extracted by the extraction unit  22  to obtain the determination signal. For example, the trend component is a component indicative of a long-term changing tendency of the vibration in about most recent thousand travels of the car  1 . The trend component includes, for example, a steady vibration component and a progressively-increasing vibration component. 
       FIGS. 16 to 18  are views each showing a transition of the variation occurred in the sensor signal. In each of the  FIGS. 16 to 18 , an ordinate axis represents a value corresponding to an amplitude of the variation occurred in the sensor signal, while an abscissa axis represents the number of activations of the elevator. The abscissa axis may represent time elapsed from installation of the elevator. The abscissa axis may represent the number of times the car  1  passes through the position P 1 . 
       FIG. 16  shows a value of the output signal Y obtained when the car  1  passes through the position P 1 . At the time when the number of activations is M 1 , the broken portion  4   c  does not appear in the main rope  4 .  FIG. 16  shows an example in which the broken portion  4   c  appears in the main rope  4  when the number of activations is M 2 . As described above, the broken portion  4   c  suddenly appears as a result of a wire break. Consequently, a variation in the sensor signal resulting from the broken portion  4   c  suddenly occurs. When the broken portion  4   c  appears in the main rope  4 , the value of the output signal Y suddenly increases as compared to a value thereof immediately before. 
       FIG. 19  is a view for illustrating a transition of the variation occurred in the sensor signal.  FIG. 19  shows the transition when, after the broken portion  4   c  appears in the main rope  4 , the car  1  makes two round trips between the uppermost floor and the position P. In the example shown in  FIG. 19 , the car  1  passes through the position P 1  at a time t 1 , at a time t 2 , at a time t 5 , and at a time t 6 .  FIG. 19( b )  shows the torque of the traction machine  11 .  FIG. 19( c )  shows the value of the output signal Y. When the broken portion  4   c  appears in the main rope  4 , every time the car  1  passes through the position P 1 , the broken portion  4   c  comes into contact with the rope guide  19 . As a result, when the broken portion  4   c  appears in the main rope  4 , the output signal Y at the position P 1  continues to show a large value thereafter. 
       FIG. 17  shows the value of the output signal Y obtained when the car  1  passes through the position P 2 . As described above, the amount of the oil applied to the guide rails does not suddenly change. The amount of the oil applied to the guide rails gradually decreases to be finally depleted unless oil is supplied. Accordingly, as shown in  FIG. 17 , a variation in the sensor signal resulting from a joint between the rail members  20  gradually increases with time. Note that, as shown in  FIG. 17 , a variation in the sensor signal resulting from the abnormality in the sheave gradually increases with time, similarly to the variation in the sensor signal resulting from the joint between the rail members  20 . 
       FIG. 17  shows an example of the output signal Y having the progressively increasing vibration component. Among the vibration components extracted by the extraction unit  22 , the progressively increasing vibration component is the vibration component gradually growing with time. For example, the progressively increasing vibration component is the vibration component which varies, on the basis of the variation in the sensor signal after oil is supplied to the guide rails, at a rate such that, when the car  1  passes through the joint between the rail members  20  thousand times, the traction machine torque signal varies by 1 [N/m]. The extraction unit  23  attenuates a vibration component as shown in  FIG. 17 . 
       FIG. 18  shows the value of the output signal Y obtained when the car  1  passes through a given position. As shown in  FIG. 18 , the variation in the sensor signal resulting from friction constantly shows the same value.  FIG. 18  shows an example of the output signal Y having the steady vibration component. Among the vibration components extracted by the extraction unit  22 , the steady vibration component is the vibration component which is steadily generated, similarly to a DC component. The steady vibration component may also include a vibration component which more slowly varies than the progressively increasing vibration component. For example, a vibration component which requires the elevator to be activated (pass through the joint) 1000 or more times to allow the traction machine torque signal to vary by 1 [N/m] may also be included in the steady vibration component. The extraction unit  23  attenuates a vibration component as shown in  FIG. 18 . 
       FIG. 20  is a view three-dimensionally showing a transition of the variation occurred in the sensor signal.  FIG. 20  corresponds to a view showing the signal shown in  FIG. 16  and the signal shown in  FIG. 17  in combination. 
       FIG. 21  is a view for illustrating an example of a function of a second extraction unit. In the example shown in the present embodiment, the second extraction unit is the extraction unit  23 . The extraction unit  23  includes, for example, a low-pass filter  34  and a subtractor  35 . For a simpler description, in the drawings and the like, the low-pass filter is referred to also as LPF. The output signal Y from the band-pass filter  32  is input to the low-pass filter  34 . The output signal Y from the band-pass filter  32  and an output signal Z from the low-pass filter  34  are input to the subtractor  35 . The subtractor  35  outputs, as the determination signal, a differential signal Y-Z between the output signal Y from the band-pass filter  32  and the output signal Z from the low-pass filter  34 . The output signal Y-Z from the subtractor  35  is input to the detection unit  24 . 
       FIG. 22  is a view for illustrating an example of performing the first extraction unit and the second extraction unit.  FIG. 22( a )  shows the torque of the traction machine  11 . The torque signal shown in  FIG. 22( a )  is input to the band-pass filter  32 .  FIG. 22( b )  shows the output signal u 2  from the amplifier  33 . The output signal u 2  from the amplifier  33  is a continuous signal. The extraction unit  22  discretizes the continuous output signal u 2 . In the example shown in  FIG. 22 , the extraction unit  22  outputs the discretized signal as the output signal Y from the band-pass filter  32 . 
     For example, a section in which the car  1  moves is imaginarily divided into a plurality of vertically consecutive unit sections.  FIG. 22  shows an example in which the unit sections are set at each given height. For example, the section in which the car position ranges from 0 m to 0.3 m is set as a first unit section. The section in which the car position ranges from 0.3 m to 0.6 m is set as a second unit section. The second unit section is the section immediately above the first unit section. The section in which the car position ranges from 0.6 m to 0.9 m is set as a third unit section. The third unit section is the section immediately above the second unit section. The sections above the third unit section are similarly set. For a simpler description, in the drawings and the like, an n-th unit section is referred to also as a section n. 
     The extraction unit  22  extracts one signal for each of the unit sections to discretize the continuous output signal u 2 . For example, the extraction unit  22  extracts the signal u 2  having a maximum value in one of the unit sections as the output signal Y in the unit section. 
     The extraction unit  23  includes the low-pass filters  34  corresponding to the individual unit sections. For example, the low-pass filter  34  corresponding to the first unit section is referred to as a filter  34 - 1 . The low-pass filter  34  corresponding to the second unit section is referred to as a filter  34 - 2 . The low-pass filter  34  corresponding to the third unit section is referred to as a filter  34 - 3 . Likewise, the low-pass filter  34  corresponding to the n-th unit section is referred to as a filter  34 - n.    
     The output signal Y from the band-pass filter  32  when the car  1  moves in the first unit section is input to the filter  34 - 1 . The output signal Z from the filter  34 - 1  corresponds to the trend component in the first unit section. The output signal Z from the filter  34 - 1  is input to the subtractor  35 . The output signal Y from the band-pass filter  32  when the car  1  moves in the second unit section is input to the filter  34 - 2 . The output signal Z from the filter  34 - 2  corresponds to the trend component in the second unit section. The output signal Z from the filter  34 - 2  is input to the subtractor  35 . 
     The output signal Y from the band-pass filter  32  when the car  1  moves in the third unit section is input to the filter  34 - 3 . The output signal Z from the filter  34 - 3  corresponds to the trend component in the third unit section. The output signal Z from the filter  34 - 3  is input to the subtractor  35 . Likewise, the output signal Y from the band-pass filter  32  when the car  1  moves in the n-th unit section is input to the filter  34 - n . The output signal Z from the filter  34 - n  corresponds to the trend component in the n-th unit section. The output signal Z from the filter  34 - n  is input to the subtractor  35 . 
     The subtractor  35  outputs, as the determination signal in the first unit section, a differential signal between the output signal Y from the band-pass filter  32  and the output signal Z from the filter  34 - 1  when the car  1  moves in the first unit section. The subtractor  35  outputs, as the determination signal in the second unit section, a differential signal between the output signal Y from the band-pass filter  32  and the output signal Z from the filter  34 - 2  when the car  1  moves in the second unit section. The subtractor  35  outputs, as the determination signal in the third unit section, a differential signal between the output signal Y from the band-pass filter  32  and the output signal Z from the filter  34 - 3  when the car  1  moves in the third unit section. Likewise, the subtractor  35  outputs, as the determination signal in the n-th unit section, a differential signal between the output signal Y from the band-pass filter  32  and the output signal Z from the filter  34 - n  when the car  1  moves in the n-th unit section. 
       FIGS. 21 and 22  show an example in which a low-pass filtering process is performed on the output signal Y from the band-pass filter  32  to obtain the trend component of the output signal Y. To implement such a function, it is necessary to set a time constant of each of the low-pass filters  34  to a rather large value. 
     For example, it is assumed that TF 1  represents the number of travels of the car  1  which is required by a value of the variation in the sensor signal resulting from the joint between the rail members  20  to vary from a given normal value to an abnormal value when oil is not supplied to the guide rails. For example, the normal value is a value of the variation in the sensor signal obtained by moving the car  1  in a state where the oil is sufficiently applied to the guide rails immediately after the installation of the elevator. The abnormal value is a value of the variation in the sensor signal set in advance as an abnormal value. Furthermore, it is assumed that TF 2  represents the number of travels of the car  1  which is required by the value of the variation in the sensor signal to return from the abnormal value to the normal value as a result of a supply of the oil to the guide rails. 
     The number of travels TF 2  is smaller than the number of travels TF 1 . The time constant of each of the low-pass filters  34  is preferably set on the basis of the number of travels TF 2 . By way of example, the time constant is set such that, as a result of causing the car  1  to pass through a given joint between the rail members  20  1000±200 times, the output of the low-pass filter  34  follows a constant input value. 
     In another example, the time constant of each of the low-pass filters  34  may be changed on the basis of the number of travels of the car  1 . For example, during a period after the oil is supplied to the guide rails and before the number of travels of the car  1  reaches a reference number, the time constant of each of the low-pass filters  34  is set to a first set value based on the number of travels TF 2 . When the number of travels of the car  1  after the oil supply reaches the reference number, the time constant of each of the low-pass filters  34  is changed from the first set value to a second set value. The second set value is larger than the first set value. The second set value is set, for example, on the basis of the number of travels TF 1 . As a result, the trend component corresponding to the state of the oil can be obtained. 
       FIGS. 23 to 25  are views showing an example of the signals input to the subtractor  35 . In  FIGS. 23 to 25 , each of solid circles indicates the output signal Y from the band-pass filter  32 , while each of blank squares indicates the output signal Z from the low-pass filter  34 .  FIG. 23  shows an example in which the output signal Y shown in  FIG. 16  is input to the subtractor  35 . As described above, when the broken portion  4   c  appears in the main rope  4 , the output signal Y rapidly increases. On the other hand, the output signal Z from the low-pass filter  34  does not follow the sudden change of the output signal Y. Therefore, a difference between the output signal Y and the output signal Z suddenly increases as a result of appearance of the broken portion  4   c  in the main rope  4 . After the broken portion  4   c  appears, the difference between the output signal Y and the output signal Z gradually decreases. 
       FIG. 24  shows an example in which the output signal Y shown in  FIG. 17  is input to the subtractor  35 . As described above, when the amount of the oil on the surfaces of the guide rails decreases, the value of the output signal Y gradually increases. When a slow change as shown in  FIG. 17  appears in the output signal Y, the output signal Z follows the change of the output signal Y. Accordingly, in the example shown in  FIG. 24 , the output signal Y and the output signal Z have similar values. 
       FIG. 25  shows an example in which the output signal Y shown in  FIG. 18  is input to the subtractor  35 . When a slow change as shown in  FIG. 18  appears in the output signal Y, the output signal Z follows the change of the output signal Y. Accordingly, in the example shown in  FIG. 25  also, the output signal Y and the output signal Z have similar values. 
     Note that, to prevent erroneous detection, as an initial value of the low-pass filter  34 , a value other than 0 is preferably set. In a case where 0 is output as an initial value of the output signal Z from the low-pass filter  34 , when a large value is output as an initial value of the output signal Y due to, for example, passage of the car  1  through a joint between the rail members  20 , a value of the determination signal Y-Z suddenly increases to cause erroneous detection. At this time, the determination signal Y-Z presents a difference between the initial value of the output signal Y and the initial value of the output signal Z. When a value other than 0 is set as the initial value of the output signal Z, even when a large value is output as the initial value of the output signal Y, the value of the determination signal Y-Z does not suddenly increase. As a result, it is possible to prevent erroneous detection. As the initial value of the low-pass filter  34 , for example, a value obtained by multiplying a value of a first threshold described later by a factor of not less than 1 is preferably set. 
       FIG. 21  and  FIG. 22  show an example in which the extraction unit  23  includes the low-pass filter  34 . The extraction unit  23  may extract the determination signal without including the low-pass filter  34 . For example, the extraction unit  23  may arithmetically determine the trend component of the vibration on the basis of a moving average value of the output signal Y from the band-pass filter  32 . For example, the extraction unit  23  arithmetically determines the moving average value from the most recently produced twenty output signals Y. In another example, the extraction unit  23  may arithmetically determine the trend component of the vibration using a machine learning algorithm such as a neural network. That is, the extraction unit  23  may have a leaning function. The foregoing is only exemplary. For example, the extraction unit  23  may arithmetically determine the moving average value from any number of the most recently produced output signals Y. Any number mentioned above is, for example, any number from ten to one hundred. 
       FIG. 26  is a view showing another example which performs the function of the second extraction unit. The extraction unit  23  includes, for example, a high-pass filter  36 . For a simpler description, in the drawings and the like, the high-pass filter is referred to also as HPF. When the low-pass filter  34  shown in  FIG. 21  is designed using a first-order-lag transfer function, the output signal Y-Z from the subtractor  35  is given by Expression 2 shown below. 
     
       
         
           
             
               
                 
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     In Expression 2, s represents a Laplace operator, while r represents a time constant. The transfer function in Expression 2 is a transfer function of a first-order high-pass filter. That is, in the example shown in  FIG. 26  also, the extraction unit  23  can perform the same function as that performed in the example shown in  FIG. 21 . In the example shown in  FIG. 26 , the output signal Y from the band-pass filter  32  is input to the high-pass filter  36 . The high-pass filter  36  outputs, as the determination signal, a signal corresponding to the output signal Y-Z from the subtractor  35 . 
       FIG. 27  is a view for illustrating another example of performing of the first extraction unit and the second extraction unit.  FIG. 27  shows the example in which the extraction unit  23  includes the high-pass filter  36 .  FIG. 27( a )  shows the torque of the traction machine  11 . The torque signal shown in  FIG. 27( a )  is input to the band-pass filter  32 .  FIG. 27( b )  shows the output signal u 2  from the amplifier  33 . The extraction unit  22  discretizes the continuous output signal u 2 . In the same manner as in the example shown in  FIG. 22 , the extraction unit  22  outputs the discretized signal as the output signal Y from the band-pass filter  32 . 
     In the example shown in  FIG. 27  also, the section in which the car  1  moves is imaginarily divided into the plurality of vertically consecutive unit sections. For example, the extraction unit  22  extracts the signal u 2  having a maximum value in one of the unit sections as the output signal Y in the unit section. 
     The extraction unit  23  includes the high-pass filters  36  corresponding to the individual unit sections. For example, the high-pass filter  36  corresponding to the first unit section is referred to as a filter  36 - 1 . The high-pass filter  36  corresponding to the second unit section is referred to as a filter  36 - 2 . The high-pass filter  36  corresponding to the third unit section is referred to as a filter  36 - 3 . Likewise, the high-pass filter  36  corresponding to the n-th unit section is referred to as a filter  36 - n.    
     The output signal Y from the band-pass filter  32  when the car  1  moves in the first unit section is input to the filter  36 - 1 . The filter  36 - 1  outputs a signal obtained by attenuating the trend component from the output signal Y. The output signal Y-Z from the filter  36 - 1  is the determination signal in the first unit section. The output signal Y from the band-pass filter  32  when the car  1  moves in the second unit section is input to the filter  36 - 2 . The filter  36 - 2  outputs a signal obtained by attenuating the trend component from the output signal Y. The output signal Y-Z from the filter  36 - 2  is the determination signal in the second unit section. 
     The output signal Y from the band-pass filter  32  when the car  1  moves in the third unit section is input to the filter  36 - 3 . The filter  36 - 3  outputs a signal obtained by attenuating the trend component from the output signal Y. The output signal Y-Z from the filter  36 - 3  is the determination signal in the third unit section. Likewise, the output signal Y from the band-pass filter  32  when the car  1  moves in the n-th unit section is input to the filter  36 - n . The filter  36 - n  outputs a signal obtained by attenuating the trend component from the output signal Y. The output signal Y-Z from the filter  36 - n  is the determination signal in the n-th unit section. 
     The detection unit  24  detects, on the basis of the determination signal extracted by the extraction unit  23 , occurrence of an abnormal variation in the sensor signal (S 103 ). The detection unit  24  detects, as the abnormal variation, a sudden variation occurred in the sensor signal. For example, the detection unit  24  determines whether or not a value of the determination signal extracted by the extraction unit  23  exceeds the first threshold. When the value of the determination signal extracted by the extraction unit  23  exceeds the first threshold, the detection unit  24  detects the occurrence of the abnormal variation in the sensor signal. The first threshold is stored in advance in the storage unit  21 . 
     The controller  13  may set the first threshold by performing a specific operation in which the car  1  actually moves. For example, when the installation of the elevator is completed, a setting operation for setting the first threshold is performed. In the setting operation, the car  1  moves from the lowermost floor to the uppermost floor. The car  1  may moves from the uppermost floor to the lowermost floor. The signal Y output from the extraction unit  22  when the car  1  moves between the lowermost floor and the uppermost floor is stored in the storage unit  21 . Then, a value obtained by multiplying a maximum value of the output signal Y stored in the storage unit  21  by a factor is set as the first threshold. The factor is a value of not less than 1. The factor may be 2. The factor may be adjusted depending on a magnitude of vibration occurring in the car  1  during a normal operation. 
     The controller  13  may perform a specific operation in which the car  1  actually moves and thus update the set first threshold. For example, at night when the elevator is used less frequently or the like, an updating operation for updating the first threshold is performed. Details of the updating operation may be the same as those of the setting operation descried above. For example, the controller  13  periodically performs the updating operation to update the first threshold. For example, the updating operation is monthly performed. This allows the first threshold to be appropriately reset on the basis of a state of the elevator. 
     The controller  13  may perform the setting operation a plurality of times at different speeds of the car  1 . For example, the controller  13  performs a first setting operation, while moving the car  1  at a first speed. By performing the first setting operation, the controller  13  sets a lower-speed first threshold. The controller  13  moves the car  1  at a second speed to perform a second setting operation. The second speed is higher than the first speed. By performing the second setting operation, the controller  13  sets a higher-speed first threshold. In the elevator apparatus in which a maximum speed of the car  1  can be changed, the detection unit  24  selects the appropriate first threshold corresponding to the maximum speed of the car  1 . For example, when a higher-speed-mode operation is performed, the detection unit  24  compares the value of the determination signal to the higher-speed first threshold. When a lower-speed-mode operation is performed, the detection unit  24  compares the value of the determination signal to the lower-speed first threshold. Likewise, the controller  13  may perform a plurality of updating operations at different speeds of the car  1 . 
     It may be possible that a lower-limit value of the first threshold is stored in the storage unit  21 . For example, when the first threshold calculated through execution of the setting operation has not reached the lower limit value, the lower limit value is set as the first threshold. When the first threshold calculated through execution of the updating operation has not reached the lower limit value, the lower limit value is set as the first threshold. Thus, it is possible to prevent an extremely small value from being set as the first threshold. 
     The car position detection unit  25  detects the position of the car  1 . For example, the car position detection unit  25  detects the car position on the basis of the rotation signal output from the encoder  18 . The car position detection unit  25  may detect the car position by another method. For example, the traction machine  11  includes an encoder. The encoder included in the traction machine  11  is also an example of the sensor configured to output a signal corresponding to the position of the car  1 . The car position detection unit  25  may detect the car position on the basis of the encoder signal from the traction machine  11 . The function of detecting the position of the car  1  may be included in the governor  15 . The function of detecting the car position may be included in the traction machine  11 . In such cases, a signal indicative of the position of the car  1  is input to the controller  13 . 
     When the occurrence of an abnormal variation in the sensor signal is detected by the detection unit  24 , the car position at an occurrence time of the abnormal variation is stored in the storage unit  21 . For example, in a case where the section in which the car  1  moves is divided into a plurality of unit sections, when the detection unit  24  detects an abnormal variation, information for specifying the unit section in which the variation occurred is stored in the storage unit  21 . 
     When the occurrence of the abnormal variation in the sensor signal is detected by the detection unit  24 , the determination unit  26  determines whether or not the main rope  4  has the broken portion  4   c  (S 104 ). When the occurrence of the abnormal variation is detected by the detection unit  24 , the determination unit  26  makes the determination on the basis of the car position at the occurrence time of the abnormal variation. For example, the determination unit  26  includes a reproducibility determining function  26 - 1  and a break determining function  26 - 2 . The reproducibility determining function  26 - 1  determines whether or not the car position at which the abnormal variation occurred has reproducibility (S 104 - 1 ). The break determining function  26 - 2  determines, on the basis of the result of the determination by the reproducibility determining function  26 - 1 , whether or not the main rope  4  has the broken portion  4   c  (S 104 - 2 ). 
       FIG. 28  is a view for illustrating an example of the reproducibility determining function  26 - 1 .  FIG. 28( a )  shows the most recent determination signal obtained when the car  1  moves from a position 0 to the position P. In the example shown in  FIG. 28( a ) , at each of the position P 1  and a position P 3 , the value of the determination signal exceeds a first threshold TH 1 .  FIG. 28( b )  shows the determination signal obtained when the car  1  previously moved in the same section. In other words, the determination signal shown in  FIG. 28( a )  is the signal acquired when the car  1  moves again in the same section immediately after the determination signal shown in  FIG. 28( b )  is acquired. In the example shown in  FIG. 28( b ) , at the positions P 1 , P 3 , and P 4 , the values of the determination signal exceed the first threshold TH 1 . 
     The reproducibility determining function  26 - 1  determines that there is reproducibility, for example, in a case where, when the car  1  passes through the same position a plurality of times, the value of the determination signal consecutively exceeds the first threshold twice. For example, at each of the positions P 1  and P 3 , the value of the determination signal consecutively exceeds the first threshold TH 1  twice. Accordingly, the reproducibility determining function  26 - 1  determines that there is reproducibility at each of the positions P 1  and P 3 . On the other hand, at the position P 4 , a most recent value of the determination signal does not exceed the first threshold TH 1 . In such a case, the reproducibility determining function  26 - 1  does not determine that there is reproducibility at the position P 4 . The reproducibility determining function  26 - 1  determines that the value at the position P 4  shown in  FIG. 28( b )  resulted from an event having no reproducibility. For example, the reproducibility determining function  26 - 1  determines that the value at the position P 4  shown in  FIG. 28( b )  resulted from a passenger jumping up and down in the car  1 . 
     Note that, when the section in which the car  1  moves is divided into a plurality of unit sections, for example, a determination as shown below is made. In a case where, when the car  1  passes through a given unit section a plurality of times, the value of the determination signal consecutively exceeds the first threshold twice, the reproducibility determining function  26 - 1  determines that there is reproducibility in the given unit section. For example, when the value of the determination signal obtained when the car  1  passes through a fifth unit section consecutively exceeds the first threshold TH 1  twice, the reproducibility determining function  26 - 1  determines that there is reproducibility in the fifth unit section. 
     The reproducibility determining function  26 - 1  may determine that there is reproducibility when the value of the determination signal consecutively exceeds the first threshold three or more times. The number of times based on which the reproducibility determining function  26 - 1  determines that there is reproducibility is arbitrarily set. 
     When it is determined by the reproducibility determining function  26 - 1  that the car position at which the abnormal variation occurred has reproducibility, the break determining function  26 - 2  determines that the broken portion  4   c  is present in the main rope  4 . When it is determined by the break determining function  26 - 2  that the broken portion  4   c  is present, the operation control unit  27  stops the car  1  at the nearest floor (S 105 ). Also, the notification unit  28  notifies a management company for the elevator (S 106 ). 
     The break detection device shown in the present embodiment uses the sensor of which the output signal varies when vibration occurs in the main rope  4  to detect the presence of the broken portion  4   c . As the sensor signal, for example, the load signal, the speed deviation signal, and the torque signal can be used. Accordingly, the break detection device shown in the present embodiment need not include a dedicated sensor to determine the presence or absence of the broken portion  4   c . As long as there is at least one sensor, the presence of the broken portion  4   c  can be detected. The break detection device need not include a large number of sensors to determine the presence or absence of the broken portion  4   c . This allows a configuration of the break detection device to be simplified. 
     In the break detection device shown in the present embodiment, by attenuating the trend component from the vibration component extracted by the extraction unit  22 , the determination signal is extracted. Accordingly, even when a variation resulting from any of the joints between the rail members  20  is included in the sensor signal, detection accuracy does not deteriorate. Even when a variation resulting from an abnormality in any of the sheaves is included in the sensor signal, the detection accuracy does not deteriorate. The break detection device shown in the present embodiment can accurately detect the presence of the broken portion  4   c.    
     In the present embodiment, the description has been given of an example in which, during a period from when the car  1  starts to move to when the car  1  stops, the break detection device constantly performs the same operation. This is only exemplary. For example, in the elevator apparatus, when the car  1  starts to move, a transient response resulting from a difference between a mass of the car  1  and a mass of the counterweight  3  occurs in speed control. Accordingly, immediately after the car  1  starts to move, a variation is likely to occur in the torque signal from the traction machine  11  and the like. To prevent the detection accuracy from being degraded by such a variation, the function of the extraction unit  22  may be stopped immediately after the car  1  starts to move. Alternatively, immediately after the car  1  starts to move, the output signal Y from the band-pass filter  32  may be forcibly set to 0. 
     In another example which prevents the degradation of the detection accuracy, immediately after the car  1  starts to move, the detection unit  24  may detect the occurrence of an abnormal variation in the sensor signal when the value of the determination signal exceeds a second threshold. The second threshold is larger than the first threshold. Note that the expression “immediately after the car  1  starts to move” means, for example, a period from when the car  1  starts to move to when the speed of the car  1  becomes a speed V 1 . The speed V 1  is stored in advance in the storage unit  21 . The expression “immediately after the car  1  starts to move” may means a period after the car  1  starts to move to when an acceleration rate of the car  1  becomes constant. 
     In the elevator apparatus, ripple occurs in the torque of the traction machine  11 . To prevent the detection accuracy from being degraded by the torque ripple, immediately after the car  1  starts to move and immediately before the car  1  stops, the function of the extraction unit  22  may be stopped. Alternatively, immediately after the car  1  starts to move and immediately before the car  1  stops, the output signal Y from the band-pass filter  32  may be forcibly set to 0. 
     In still another example which prevents the degradation of the detection accuracy, immediately after the car  1  starts to move and immediately before the car  1  stops, the detection unit  24  may detect the occurrence of an abnormal variation in the sensor signal when the value of the determination signal exceeds a third threshold. The third threshold is larger than the first threshold. Note that the expression “immediately after the car  1  starts to move and immediately before the car  1  stops” means, for example, a period during which the speed of the car  1  is lower than a speed V 2 . The speed V 2  is stored in advance in the storage unit  21 . The speed V 2  is set to, for example, a speed at which a frequency band of the torque ripple of the traction machine  11  falls outside a particular frequency band resulting from contact of the broken portion  4   c  with the rope guide. 
     In the example shown in the present embodiment, the section in which the car  1  moves is divided into the plurality of unit sections. The following will describe a preferred example of the division. 
     In the example shown in  FIG. 22 , when the occurrence of an abnormal variation in the sensor signal is detected by the detection unit  24 , for example, a number of the unit section in which the abnormal variation occurred is stored in the storage unit  21 . When the section in which the car  1  moves is divided into n unit sections, the storage unit  21  is required to have n storage regions each for storing the occurrence of the abnormal variation. As a result, when the number of the divided unit sections increases, the position at which the broken portion  4   c  is present can accurately be specified, but a capacity of the storage unit  21  should be increased. On the other hand, when the number of the divided unit sections is small, the capacity of the storage unit  21  need not be increased, but the position at which the broken portion  4   c  is present cannot accurately be specified. 
       FIG. 29  is a view showing a cross section of the return sheave  7 . In an example shown in  FIG. 29 , the broken portion  4   c  of the main rope  4  comes into contact with the facing portion  19   b  of the rope guide  19 , and then comes into contact with the facing portion  19   a  thereof. A variation occurring in the sensor signal when the broken portion  4   c  comes into contact with the facing portion  19   b  and a variation occurring in the sensor signal when the broken portion  4   c  comes into contact with the facing portion  19   a  need not successfully be detected as different abnormal variations. When it is assumed that L 1  represents a length of a section of the main rope  4  between a portion of the main rope  4  facing the facing portion  19   b  and a portion thereof facing the facing portion  19   a , even when a height of each of the unit sections is larger than the rope length L 1 , no problem is encountered. For example, the rope length L 1  is determined on the basis of a smallest one of the sheaves around which the main rope  4  is wound. The rope length L 1  may be determined on the basis of a most commonly-sized one of the sheaves around which the main rope  4  is wound. 
       FIG. 30  is a view showing the car  1  guided by the guide rails. As described above, each of the guide rails includes the plurality of rail members  20 . Preferably, a variation occurring in the sensor signal when the car  1  passes through a given joint between the rail members  20  and a variation occurring in the sensor signal when the car  1  passes through a joint located immediately above the given joint are detected as different abnormal variations. When it is assumed that L 2  represents a length of each of the rail members  20 , the height of the unit section is preferably smaller than the length L 2  of the rail member  20 . For example, the length L 2  is determined on the basis of the rail member  20  which is shortest among the rail members  20 . The length L 2  may be determined on the basis of a length of the most commonly-used one of the rail members  20 . 
     When it is assumed that H represents the height of each of the unit sections, it is optimum that the height H of the unit section satisfies the following condition: 
       [Rope Length  L 1]≤[Height  H ]≤[Length  L 2 of Rail Member 20].
 
     In the example described in the present embodiment, the presence of the broken portion  4   c  is detected without consideration of a direction in which the car  1  moves. This is only exemplary. It may be possible to detect the presence of the broken portion  4   c  by separately considering a case where the car  1  moves upward and a case where the car  1  moves downward. 
     In such a case, when the occurrence of an abnormal variation in the sensor signal is detected by the detection unit  24 , the car position and a moving direction of the car  1  when the variation occurred are stored in the storage unit  21 . The reproducibility determining function  26 - 1  determines whether or not the car position at which the abnormal variation occurred has reproducibility in consideration also of the moving direction of the car  1 . 
     When consideration is given to the moving direction of the car  1 , for example, a setting operation for ascent in which the car  1  moves from the lowermost floor to the uppermost floor is performed, and a first threshold for ascent is set. A setting operation for descent in which the car  1  moves from the uppermost floor to the lowermost floor is performed, and a first threshold for descent is set. In addition, an updating operation for ascent in which the car  1  moves from the lowermost floor to the uppermost floor is performed, and the first threshold for ascent is updated. A setting operation for descent in which the car  1  moves from the uppermost floor to the lowermost floor is performed, and the first threshold for descent is updated. The reproducibility determining function  26 - 1  determines that there is reproducibility in a case where, for example, when the car  1  passes through the same position in the same direction, the value of the determination signal consecutively exceeds the first threshold twice. 
     In the example described in the present embodiment, the reproducibility determining function  26 - 1  determines that there is reproducibility in the case where, when the car  1  passes through the same position, the value of the determination signal consecutively exceeds the first threshold a plurality of times. This is only exemplary. The determination unit  26  may determine whether or not the main rope  4  has the broken portion  4   c  on the basis of a frequency with which the occurrence of an abnormal variation is detected by the detection unit  24  when the car  1  passes through the same position. 
     For example, when the occurrence of an abnormal variation in the sensor signal is detected by the detection unit  24 , the car position at an occurrence time of the abnormal variation is stored in the storage unit  21 . When the section in which the car  1  moves is divided into a plurality of unit sections, the number of the unit section in which the variation occurred is stored in the storage unit  21 . For example, in the storage unit  21 , storage regions corresponding to the individual unit sections are formed. In a case where the occurrence of an abnormal variation when the car  1  moves in a given one of the unit sections is detected by the detection unit  24 , 1 is stored in the storage region corresponding to the given unit section. In a case where the occurrence of an abnormal variation when the car  1  moves in a given one of the unit sections is not detected by the detection unit  24 , 0 is stored in the storage region corresponding to the given unit section. 
     The reproducibility determining function  26 - 1  arithmetically determines, for example, a moving average value of the values stored in the storage regions as the foregoing frequency. For example, the reproducibility determining function  26 - 1  arithmetically determines the moving average value when the car  1  passes through the same position four times. The break determining function  26 - 2  determines whether or not the main rope  4  has the broken portion  4   c  on the basis of the frequency arithmetically determined by the reproducibility determining function  26 - 1 . For example, the break determining function  26 - 2  determines that the main rope  4  has the broken portion  4   c  when the moving average value arithmetically determined by the reproducibility determining function  26 - 1  exceeds the first determination threshold. The first determination threshold is stored in advance in the storage unit  21 . 
       FIG. 31  is a view showing another example of the break detection device in the first embodiment. In the example shown in  FIG. 31 , the controller  13  is different from that in the example shown in  FIG. 13  in further including an arithmetic unit  29 . 
     In the example shown in  FIG. 31 , the storage unit  21  stores a determination score for determining whether or not the broken portion  4   c  is present. The arithmetic unit  29  arithmetically determines the determination score on the basis of the result of the detection by the detection unit  24 . For example, when the occurrence of an abnormal variation in the sensor signal is detected by the detection unit  24 , the car position at the occurrence time of the abnormal variation is associated with the determination score and stored in the storage unit  21 . The determination unit  26  determines whether or not the main rope  4  has the broken portion  4   c  on the basis of the determination score stored in the storage unit  21 . Note that, when the section in which the car  1  moves is divided into a plurality of unit sections, the determination scores corresponding to the individual unit sections are stored in the storage unit  21 . 
       FIGS. 32 and 33  are views showing examples of the broken portion  4   c .  FIG. 32  shows the example in which the broken portion  4   c  goes away from the return sheave  7  toward a tip end thereof. When the broken portion  4   c  protrudes from a surface of the main rope  4  as shown in  FIG. 32 , the broken portion  4   c  comes into contact with the rope guide  19  when passing through the return sheave  7 .  FIG. 33  shows the example in which the broken portion  4   c  is disposed so as to extend along a surface of the return sheave  7 . When the broken portion  4   c  protrudes from the surface of the main rope  4  as shown in  FIG. 33 , the broken portion  4   c  does not come into contact with the rope guide  19  when passing through the return sheave  7 . Consequently, even when the broken portion  4   c  passes through the return sheave  7 , no vibration occurs in the main rope  4 . 
     An orientation of the broken portion  4   c  may be changed as a result of contact of the broken portion  4   c  with the rope guide  19 . When the orientation of the broken portion  4   c  is changed from the orientation shown in  FIG. 32  to the orientation shown in  FIG. 33 , variation no longer occurs in the main rope  4  even though the broken portion  4   c  passes through the return sheave  7 . On the other hand, the orientation of the broken portion  4   c  may be changed when the broken portion  4   c  is pressed by a surface of the groove on passing through the return sheave  7 . The orientation of the broken portion  4   c  may be changed when the wire or the strand is further raveled. When the orientation of the broken portion  4   c  is changed from the orientation shown in  FIG. 33  to the orientation shown in  FIG. 32 , vibration occurs in the main rope  4  when the broken portion  4   c  passes through the return sheave  7 . 
       FIG. 34  is a view for illustrating an example of the functions of the arithmetic unit  29  and the determination unit  26 .  FIG. 34( a )  shows the position of the car  1 .  FIG. 34( b )  shows the torque of the traction machine  11 .  FIG. 34( c )  shows the determination signal.  FIG. 34( d )  shows an example of transition of the determination score. 
     In the example shown in  FIG. 34 , the car  1  makes two round trips between the lowermost floor and the position P. The car  1  passes through the position P 1  at a time t 1 , at a time t 2 , at a time t 5 , and at a time t 6 .  FIG. 34  shows the example in which the main rope  4  has the broken portion  4   c . The broken portion  4   c  passes through the return sheave  7  at the time t 1 , at the time t 2 , at the time t 5 , and at the time t 6 . As described above, even when the main rope  4  has the broken portion  4   c , the broken portion  4   c  does not always come into contact with the rope guide  19 . In the example shown in  FIG. 34 , the broken portion  4   c  comes into contact with the rope guide  19  at the time t 1 , at the time t 5 , and at the time t 6 . The broken portion  4   c  does not come into contact with the rope guide  19  at the time t 2 . 
     For example, when the broken portion  4   c  comes into contact with the rope guide  19  at the time t 1 , the value of the determination signal exceeds the first threshold. As a result, the detection unit  24  detects the occurrence of an abnormal variation in the sensor signal. For example, a case where the position P 1  is included in an eighth unit section is considered. At the time t 1 , the determination score of the eighth unit section is set to an initial value. For example, the initial value is 0. When the occurrence of an abnormal variation is detected by the detection unit  24  when the car  1  passes through the eighth unit section, the arithmetic unit  29  adds a given value to the determination score of the eighth unit section.  FIG. 34( d )  shows the example in which the given value to be added is 5. 
     The determination unit  26  determines whether or not the determination score stored in the storage unit  21  exceeds a second determination threshold. The second determination threshold is stored in advance in the storage unit  21 .  FIG. 34( d )  shows the example in which the second determination threshold is 10. At the time t 1 , the determination score of the eighth unit section has not exceeded the second determination threshold. When the determination score has not exceeded the second determination threshold, the determination unit  26  determines that the main rope  4  does not have the broken portion  4   c.    
     The car  1  passes the position P 1  again at the time t 2 . At the time t 2 , the broken portion  4   c  does not come into contact with the rope guide  19 . When the occurrence of an abnormal variation is not detected by the detection unit  24  when the car  1  passes through a position at which the determination score is not 0, the arithmetic unit  29  reduces the determination score at that position. At the time t 2 , the determination score of the eighth unit section is not 0. At the time t 2 , the arithmetic unit  29  reduces a given value from the determination score of the eighth unit section.  FIG. 34( d )  shows the example in which the given value to be reduced is 1. 
     At the time t 5 , the car  1  passes through the position P 1  again. At the time t 5 , the detection unit  24  detects the occurrence of an abnormal variation in the sensor signal. Consequently, the arithmetic unit  29  adds 5 to the determination score of the eighth unit section stored in the storage unit  21 . At the time t 5 , the determination score of the eighth unit section has not exceeded the second determination threshold. Accordingly, the determination unit  26  determines that the main rope  4  does not have the broken portion  4   c.    
     Subsequently, at the time t 6 , the car  1  passes through the position P 1  again. The detection unit  24  detects the occurrence of an abnormal variation in the sensor signal at the time t 6 . Consequently, the arithmetic unit  29  further adds 5 to the determination score of the eighth unit section stored in the storage unit  21 . The determination score of the eighth unit section stored in the storage unit  21  becomes 14 at the time t 6 . At the time t 6 , the determination score of the eighth unit section exceeds the second determination threshold. Accordingly, the determination unit  26  determines that the main rope  4  has the broken portion  4   c  at the time t 6 . 
     In the example shown in  FIG. 34 , even when a time period during which the broken portion  4   c  does not come into contact with the rope guide  19  appears, it is possible to detect the presence of the broken portion  4   c.    
     In a case where the section in which the car  1  moves is not divided into a plurality of unit sections, when the car  1  passes through the car position stored in the storage unit  21  again and the detection unit  24  detects an abnormal variation at that moment, a given value is added to the determination score at the position. When the car  1  passes through the position of concern again and an abnormal variation is not detected by the detection unit  24  at that moment, a given value is subtracted from the determination score at the position. In such a case, as long as a distance from the car position stored in the storage unit  21  to the position is equal to or smaller than a reference distance, the position may be regarded as identical to the stored car position. The reference distance is set to, for example, the rope length L 1 . 
     Preferably, the second determination threshold is equal to or more than twice the value to be added to the determination score. As long as the second determination threshold is equal to or more than twice the value to be added to the determination score, it is possible to inhibit erroneous detection resulting from an event having no reproducibility. In consideration also of the probability that the broken portion  4   c  does not consecutively come into contact with the rope guide  19 , the value to be subtracted from the determination score is preferably equal to or less than one half of the value to be added. 
     The second determination threshold may be variable depending on a magnitude of the determination signal. For example, as the second determination threshold, a first value and a second value are set in advance. The second value is larger than the first value. When the magnitude of the determination signal is equal to or less than a reference value, as the second determination threshold, the second value is used. Specifically, when such a variation as to allow the magnitude of the determination signal to exceed the reference value occurs in the sensor signal, the presence of the broken portion  4   c  can be detected at an early stage. By way of example, when Condition 1 shown below is satisfied, the second determination threshold is set to 15. When Condition 2 shown below is satisfied, the second determination threshold is set to 10. 
       [First Threshold]≤[Determination Signal]≤2×[First Threshold]  Condition 1:
 
       2≤[First Threshold]&lt;[Determination Signal]  Condition 2:
 
     Second Embodiment 
       FIG. 35  is a view showing examples of signals input to the subtractor  35  of the second extraction unit. In  FIG. 35 , each of broken lines represents the output signal u 2  from the amplifier  33 . Specifically, each of the broken lines represents the output signal Y before discretization. Each of blank circles represents the discretized output signal Y. Each of solid lines represents the output signal Z from the low-pass filter  34 . In  FIG. 35 , each of abscissa axes represents the car position.  FIG. 35  shows signals obtained when the car  1  passes through an (n−1)-th unit section, the n-th unit section, and an (n+1)-th unit section. 
       FIG. 35( a )  shows an example in which, in the n-th unit section, an output signal Y(n) exceeding the first threshold is present. When the output signal Y(n) is generated due to a joint between the rail members  20 , an output signal Z(n) in the n-th unit section follows the output signal Y(n). A value of the output signal Z(n) becomes similar to a value of the output signal Y(n). Consequently, an output signal Y(n)-Z(n) serving as the determination signal in the n-th unit section has a value smaller than the first threshold. In the example shown in  FIG. 35( a ) , in each of the (n−1)-th unit section, the n-th unit section, and the (n+1)-th unit section, the detection unit  24  does not detect the occurrence of an abnormal variation in the sensor signal. 
       FIG. 35( b )  shows the signal when, immediately after the signal shown in  FIG. 35( a )  is acquired, the car  1  passes through the (n−1)-th unit section, the n-th unit section, and the (n+1)-th unit section again. In the example shown in  FIG. 35( b ) , in the (n−1)-th unit section, there is an output signal Y(n−1) exceeding the first threshold. The output signal Y(n−1) shown in  FIG. 35( b )  corresponds to the output signal Y(n) shown in  FIG. 35( a )  that is shifted into the (n−1)-th unit section. Such an event occurs as a result of, for example, elongation of the main rope  4 . 
     In the example shown in  FIG. 35( b ) , an output signal Z(n−1) in the (n−1)-th unit section does not follow a rapid change of the output signal Y(n−1). As a result, when an output signal Y(n−1)-Z(n−1) serving as the determination signal in the (n−1)-th unit section is larger than the first threshold, the break determining function  26 - 2  may determine that the broken portion  4   c  is present. Note that, in the n-th unit section, the output signal Y(n) rapidly decreases. The output signal Z(n) does not follow a rapid change of the output signal Y(n). Accordingly, an output signal Y(n)-Z(n) serving as the determination signal in the n-th unit section has a negative value. 
     In the present embodiment, a description will be given of a function for preventing such erroneous detection. An example of the break detection device in the present embodiment is the same as the example shown in  FIG. 13 . As a function not disclosed in the present embodiment, any of the functions disclosed in the first embodiment may be adopted. For example, the controller  13  may further include the arithmetic unit  29 . 
       FIG. 36  is a view for illustrating an example of the function of the second extraction unit.  FIG. 36( a )  is a view corresponding to  FIG. 35( a ) .  FIG. 36( b )  is a view corresponding to  FIG. 35( b ) . In the example shown in the present embodiment, the extraction unit  23  outputs, as the determination signal, the signal Y-Z in consideration also of values of the output signals in adjacent unit sections in regard to the output signal Z from the low-pass filter  34 . For example, the extraction unit  23  outputs the determination signal as shown below. 
       ( n− 1)-th Unit Section:  Y ( n− 1)−max( Z ( n− 2), Z ( n− 1), Z ( n ))
 
         n -th Unit Section:  Y ( n )−max( Z ( n− 1), Z ( n ), Z ( n+ 1))
 
       ( n+ 1)-th Unit Section:  Y ( n+ 1)−max( Z ( n ), Z ( n+ 1), Z ( n+ 2))
 
     The following will describe an example in which the determination signal in the n-th unit section is arithmetically determined. The n-th unit section is the section immediately below the (n+1)-th unit section and immediately above the (n−1)-th unit section. The extraction unit  23  specifies, from among the output signal Z(n) in the unit section of concern, the output signal Z(n−1) in the unit section immediately below, and the output signal Z(n+1) in the unit section immediately above, the output signal having a maximum value. In the example shown in  FIG. 36( a ) , the output signal Z(n) has a largest value from among the foregoing three signals. The extraction unit  23  outputs, as the determination signal, a differential signal between the output signal Y(n) in the unit section of concern and the output signal Z(n) specified as the signal having the largest value. 
     The extraction unit  23  similarly arithmetically determines the determination signal also for each of the (n−1)-th unit section and the (n+1)-th unit section. In the example shown in  FIG. 36( a ) , the determination signals are arithmetically determined as shown below. 
       ( n− 1)-th Unit Section:  Y ( n− 1)− Z ( n )&lt;0
 
         n -th Unit Section:  Y ( n )− Z ( n )≈0
 
       ( n+ 1)-th Unit Section:  Y ( n+ 1)− Z ( n )&lt;0
 
     It is assumed that, in the example shown in  FIG. 36( a ) , a value of the output signal Z(n−2) is smaller than a value of the output signal Z(n), and that a value of the output signal Z(n+2) is smaller than the value of the output signal Z(n). 
       FIG. 36( b )  shows the signal when, immediately after the signal shown in  FIG. 36( a )  is acquired, the car  1  passes through the (n−1)-th unit section, the n-th unit section, and the (n+1)-th unit section again. The output signal Y(n−1) shown in  FIG. 36( b )  corresponds to the output signal Y(n) shown in  FIG. 36( a )  that is shifted into the (n−1)-th unit section. 
     In the example shown in  FIG. 36( b ) , the determination signals are arithmetically determined as follows. 
       ( n− 1)-th Unit Section:  Y ( n− 1)− Z ( n )≈0
 
         n -th Unit Section:  Y ( n )− Z ( n )&lt;0
 
       ( n+ 1)-th Unit Section:  Y ( n+ 1)− Z ( n )&lt;0
 
     In the example shown in the present embodiment, it is possible to prevent a variation in the sensor signal resulting from any of the joints between the rail members  20  from being erroneously detected as a variation in the sensor signal resulting from the broken portion  4   c.    
     Third Embodiment 
       FIG. 37  is a view showing an example of the break detection device in a third embodiment. In the example shown in  FIG. 37 , the controller  13  is different from that in the example shown in  FIG. 13  in that the controller  13  further includes a detection unit  30  and a determination unit  31 . As a function not disclosed in the present embodiment, any of the functions disclosed in the first or second embodiment may be adopted. For example, the controller  13  may further include the arithmetic unit  29 . 
     The detection unit  30  detects, on the basis of a vibration component extracted by the extraction unit  22 , occurrence of an abnormal variation in the sensor signal. For example, the detection unit  30  determines whether or not a value of the vibration component extracted by the extraction unit  22  has exceeded a fourth threshold. When the value of the vibration component extracted by the extraction unit  22  has exceeded the fourth threshold, the detection unit  30  detects the occurrence of an abnormal variation in the sensor signal. The fourth threshold is stored in advance in the storage unit  21 . 
     The determination unit  31  determines a specific abnormality occurred in the elevator on the basis of a result of the detection by the detection unit  24  and a result of the detection by the detection unit  30 . The determination unit  31  determines an abnormality other than the presence of the broken portion  4   c . Accordingly, when the occurrence of an abnormal variation is not detected by the detection unit  24  and the occurrence of an abnormal variation is detected by the detection unit  30 , the determination unit  31  determines the occurrence of a specific abnormality 
     For example, the determination unit  31  specifies a number N 1  of times the occurrence of an abnormal variation is detected by the detection unit  30 . For example, the determination unit  31  determines the number N 1  of times the car  1  moves from the lowermost floor to the uppermost floor. When the occurrence of an abnormal variation is not detected by the detection unit  24 , the occurrence of an abnormal variation is determined by the detection unit  30 , and the foregoing specified number N 1  of times is larger than a reference number, the determination unit  31  determines the occurrence of an abnormality in any of the sheaves. When the occurrence of an abnormal variation is not detected by the detection unit  24 , the occurrence of an abnormal variation is determined by the detection unit  30 , and the foregoing specified number N 1  of times is smaller than the reference number, the determination unit  31  determines the occurrence of an abnormality in any of the joints between the rail members  20 . 
     When the occurrence of a specific abnormality is determined by the determination unit  31 , the operation control unit  27  stops the car  1  at a nearest floor. The notification unit  28  notifies the management company for the elevator. In the example shown in the present embodiment, it is possible to detect an abnormality in any of the joints between the rail members  20  and an abnormality in any of the sheaves. 
     In the example described in each of the first to third embodiments, the broken portion  4   c  occurred in the main rope  4  is detected. The break detection device may detect a broken portion occurred in another rope used for the elevator. 
     In each of the first to third embodiments, each of the units denoted by the reference numerals  21  to  31  shows a function included in the controller  13 .  FIG. 38  is a view showing an example of a hardware element included in the controller  13 . For example, the controller  13  includes, as a hardware resource, processing circuitry  39  including a processor  37  and a memory  38 . A function of the storage unit  21  is implemented by the memory  38 . The controller  13  implements a function of each of the units denoted by the reference numerals  22  to  31  through execution of a program stored in the memory  38  by the processor  37 . 
     The processor  37  is referred to also as a CPU (Central Processing Unit), a central processor, a processing device, an arithmetic device, a microprocessor, a microcomputer, or a DSP. As the memory  38 , a semiconductor memory, a magnetic disc, a flexible disc, an optical disc, a compact disc, a mini disc, or a DVD may also be used. Usable semiconductor memories include a RAM, a ROM, a flash memory, an EPROM, an EEPROM, and the like. 
       FIG. 39  is a view showing another example of the hardware element included in the controller  13 . In the example shown in  FIG. 39 , the controller  13  includes, for example, processing circuitry  39  including a processor  37 , a memory  38 , and dedicated hardware  40 .  FIG. 39  shows the example in which any of the functions of the controller  13  is implemented using the dedicated hardware  40 . It may be possible to implement all the functions of the controller  13  using the dedicated hardware  40 . As the dedicated hardware  40 , a single circuit, a composite circuit, a programmed processor, a parallel-programmed processor, an ASIC, an FPGA, or a combination thereof can be used. 
     INDUSTRIAL APPLICABILITY 
     The break detection device according to the invention can be used to detect a broken portion occurred in a rope of an elevator. 
     REFERENCE SIGNS LIST 
       
     
       
         
           
               
               
               
               
               
             
               
                   
               
             
            
               
                 1 car, 
                 2 shaft, 
                 3 counterweight, 
                 4 main rope, 
                 4a end portion, 
               
               
                 4b end portion, 
                 4c broken portion, 
                 5 suspension sheave, 
                 6 suspension sheave, 
                 7 return sheave, 
               
               
                 7a shaft, 
                 8 driving sheave, 
                 9 return sheave, 
                 10 suspension sheave, 
                 11 traction machine, 
               
               
                 12 load weighing device, 
                 13 controller, 
                 15 governor, 
                 16 governor rope, 
                 17 governor sheave, 
               
               
                 18 encoder, 
                 19 rope guide, 
                 19a facing portion, 
                 19b facing portion, 
                 20 rail member, 
               
               
                 21 storage unit, 
                 22 extraction unit, 
                 23 extraction unit, 
                 24 detection unit, 
                 25 car position 
               
               
                   
                   
                   
                   
                 detection unit, 
               
               
                 26 determination unit, 
                 26-1 reproducibility 
                 26-2 break determining 
                 27 operation control unit, 
                 28 notification unit, 
               
               
                   
                 determining function, 
                 function, 
               
               
                 29 arithmetic unit, 
                 30 detection unit, 
                 31 determination unit, 
                 32 band-pass filter, 
                 33 amplifier, 
               
               
                 34 low-pass filter, 
                 35 subtractor, 
                 36 high-pass filter, 
                 37 processor, 
                 38 memory, 
               
               
                 39 processing circuitry, 
                 40 dedicated hardware