Abstract:
A centrifugal separator facilitates maintenance with a function that provides the user with useful data for investigating the causes of failures and for preventing their recurrence, such as data needed to determine the appropriate management and replacement frequency of consumable parts. The centrifugal separator also has a storing unit for recording the number of times that the door is opened and closed, operation records of the drive unit by each shaft, and the number of operations performed by operating function, as well as a display unit for displaying the data. The centrifugal separator also includes a function for displaying messages prompting the user to perform maintenance when the aforementioned performance data reach a predetermined value.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a centrifugal separator and the maintenance thereof.  
         [0003]     2. Description of Related Art  
         [0004]     If the drive unit or rotor of a conventional centrifugal separator becomes damaged while a customer is using the centrifugal separator, such damage can have an enormous effect on the customer&#39;s business, not only due to the loss of the sample undergoing centrifugation and the cost of repair work to the centrifugal separator, but also due to the lost time while the centrifugal separator is being repaired.  
         [0005]     Since the customer might suffer great losses when the drive unit or rotor break down or incur damage, the life of the drive unit and rotor is specified in advance. Here, the life of the drive unit denotes the estimated usage time, while the life of the rotor denotes the estimated number of uses and the usage time. Operation records of the drive unit and rotor must be maintained so that these components are not used past their estimated life. Conventionally, the user has had to meticulously record the operation records each time the centrifugal separator was used. A centrifugal separator capable of automating the management of the operation records described above is also well known in the art. Such centrifugal separators that employ a method for managing operation records and a method for managing the rotor life have been disclosed in Japanese patent No. 2671642 and Japanese patent-application publication No. 2001-104835.  
       SUMMARY OF THE INVENTION  
       [0006]     When a failure occurs, centrifugal separators normally display a unique alarm that can help in identifying the cause of the failure. In addition to displaying a unique alarm when a failure occurs, some centrifugal separators possess a function for storing the control state (operational status) of the centrifugal separator in a time sequence, and a function for displaying details of the failure and the control state of the centrifugal separator during the failure in a time sequence when the repairperson performs a predetermined operation.  
         [0007]     However, if the part that fails is a relatively minor moving part, such as a gas spring or a door hinge, the usage time and number of uses are still listed to provide a rough guideline for the frequency in which such consumable parts should be replaced. This data can be used in operation manuals or the like for recommending the periodic replacement of such parts.  
         [0008]     With these types of centrifugal separators, either the user has had to meticulously record the operation records of the drive unit, or the centrifugal separator has means for automatically recording the operation records of the drive unit. On the other hand, some centrifugal separators are provided with a plurality of shafts that can be selected to suit the shape of the rotor. It has been sufficient to manage the operation records of the drive unit (accumulated operating time, accumulated number of rotations, and accumulated number of operations) regardless of the rotor being used for centrifugal separators with only a single shaft. However, the same management of operation records is insufficient for centrifugal separators with drive units having a plurality of shafts.  
         [0009]     In view of the foregoing, it is an object of the present invention to provide a centrifugal separator that is easy to perform maintenance.  
         [0010]     In order to attain the above and other objects, the present invention provides a centrifugal separator for selectively mounting and rotating a rotor among a plurality of rotors each having a kind or a size different from each other. The centrifugal separator includes a main body, a power generator, a plurality of shafts, and a storing unit. The main body has a rotor chamber that accommodates the selected rotor. The power generator is supported by the main body and has an output shaft which generates rotation torque. The plurality of shafts extends in the rotor chamber and is disposed concentrically. The storing unit stores data indicative of operation records for each of the plurality of shafts.  
         [0011]     The centrifugal separator according to the present invention can easily provide the user or repairperson with information serving as a guideline for parts replacement and maintenance, enabling the user or repairperson to obtain accurate information regarding the usage of the centrifugal separator that is necessary for investigating the cause of a failure and preventing its recurrence. Hence, the present invention can provide a centrifugal separator that is easy to maintain. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     The above and other objects, features and advantages of the invention will become more apparent from reading the following description of the embodiments taken in connection with the accompanying drawings in which:  
         [0013]      FIG. 1  is an explanatory diagram showing the structure of a centrifugal separator according to an embodiment of the present invention;  
         [0014]      FIG. 2  is a cross-sectional view of a drive unit in the centrifugal separator according to the embodiment;  
         [0015]      FIG. 3  is an explanatory diagram showing storage areas in SRAM provided in the centrifugal separator of the embodiment;  
         [0016]      FIG. 4  is an explanatory diagram showing storage areas in EEPROM provided in the centrifugal separator of the embodiment;  
         [0017]      FIG. 5  is an explanatory diagram showing the construction of a door switch;  
         [0018]      FIG. 6  is a flowchart illustrating steps in a process according to the embodiment for recording records of the accumulated number of times the door is opened and closed;  
         [0019]      FIG. 7  is a flowchart illustrating steps in a process according to the embodiment for recording records of the accumulated time during which the door is open and during which the door is closed while the motor is idle;  
         [0020]      FIG. 8  is a flowchart illustrating steps in a process according to the embodiment for recording operation records by each shaft;  
         [0021]      FIG. 9  is a flowchart illustrating steps in a process according to the embodiment for recording operation records by operating function;  
         [0022]      FIG. 10  is an explanatory diagram showing a sample view of the display unit in a conventional centrifugal separator;  
         [0023]      FIG. 11  is an explanatory diagram showing a sample view of the display unit in the centrifugal separator according to the embodiment;  
         [0024]      FIG. 12  is an explanatory diagram showing another sample view of the display unit in the centrifugal separator according to the embodiment;  
         [0025]      FIG. 13  is a cross-sectional view of a drive unit in a centrifugal separator according to a first modification;  
         [0026]      FIG. 14  is a cross-sectional view of a drive unit in a centrifugal separator according to a second modification; and  
         [0027]      FIG. 15  is a cross-sectional view of a drive unit in a centrifugal separator according to a third modification. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0028]     A centrifugal separator according to an embodiment of the present invention will be described while referring to  FIGS. 1 through 12 .  
         [0029]     As shown in  FIG. 1 , a centrifugal separator  1  includes a main body (casing)  15  provided with a rotor chamber  3 , a control panel  10 , a door  2 , a rotor  4 , a cooling machine  5 , a drive unit  6 , a temperature sensor  7 , a door switch  8 , a rotor detector  9 , and a control unit  20 . All of the aforementioned components of the centrifugal separator  1  are accommodated within the main body  15 , except the control panel  10  and the door  2 . The drive unit  6  is supported by the main body  15 . A personal computer  27  is connected to the centrifugal separator  1  via an external connector  28  described later. The control unit  20  is also disposed inside the main body  15 , but is shown outside the main body  15  in  FIG. 1  for explanatory purposes.  
         [0030]     The control panel  10  is disposed on top of the main body  15  and includes an operating unit  10   b  for inputting operating conditions and the like, including rotational speed, operating time, and preset temperature; and a display unit  10   a  for displaying the operating conditions inputted via the operating unit  10   b  and the operating status. The operating unit  10   b  includes switches  10   c  and  10   d . An opening  15   a  is also formed in the top portion of the main body  15 . The door  2  is positioned over the opening  15   a  and is capable of opening and closing to expose the rotor chamber  3  positioned below the opening  15   a . The drive unit  6  is disposed below the center part of the rotor chamber  3  for driving the rotor  4  to rotate. The rotor  4  selected from among a plurality of types of rotors is mounted to suit the operating conditions and the volume of samples to undergo centrifugation. For example, the plurality of types of rotors has a kind or a size different from each other. The selected rotor  4  is detachably mounted on the drive unit  6  via a crown portion  33  ( FIG. 2 ) disposed on top of the drive unit  6 . A rotor identifying portion (not shown) is provided on the bottom of the rotor. The rotor detector  9  is disposed in the bottom of the rotor chamber  3  for reading an identifier provided on the rotor identifying portion. The identifier is specific to each type of rotor. In the present embodiment, the rotor detector  9  is a magnet sensor. The identifier includes a plurality of magnets that is in a specific arrangement in a ring shape on the bottom of the rotor and thus generates a specific magnet pattern. Therefore, the rotor detector  9  can detect the specific magnet pattern and identify the selected (mounted) rotor  4 . However, the rotor detector  9  and the identifier may be different type of detector and identifier other than a magnet sensor and magnets.  
         [0031]     Refrigerant piping  50  is provided around the periphery of the rotor chamber  3  for cooling the same, while the cooling machine  5  is disposed in the bottom of the main body  15  for circulating the coolant in the refrigerant piping  50 . The control unit  20  controls the drive unit  6  and the cooling machine  5  based on operating conditions inputted via the operating unit  10   b  and output signals received from the door switch  8 , rotor detector  9 , and temperature sensor  7 , and displays various data on the display unit  10   a . In the present embodiment, both the drive unit  6  and the cooling machine  5  are driven by a drive circuit  26 , but may be driven by separate drive circuits instead.  
         [0032]     The control unit  20  accommodates a central processing unit (CPU)  21 , a static random access memory (SRAM)  22  capable of high-speed reading and writing, an electrically erasable programmable read only memory (EEPROM)  23  which is nonvolatile and has an electrical reading and writing capacity, a battery  25  for preserving data stored in the SRAM  22  when the power source to the centrifugal separator is shut off, and a read only memory (ROM)  24  for storing control programs executed by the CPU  21 . A external connector  28  is also provided on the main body  15  for connecting the control unit  20  (CPU  21 ) with the external personal computer  27 . The ROM  24  has a storage area  24   a  for storing a data set that includes various data for controlling the rotor (maximum rotational speed, temperature control data, minimum rotational radius, maximum rotational radius, selected shaft, etc.). The control unit  20  is configured so that service personnel or the like may later add new rotor control data to the EEPROM  23  that was not included when the centrifugal separator  1  was shipped.  
         [0033]     The CPU  21  transmits signals to the drive circuit  26  according to operating conditions for the centrifugal separator  1  received from the operating unit  10   b  for controlling the drive unit  6  and the cooling machine  5  so that the rotor  4  operates at a desired rotational speed and temperature for the inputted operating time. The operating conditions include rotor number, rotational speed, operating time, control temperature, acceleration gradient, deceleration gradient, etc. As described earlier, the identifier (not shown) formed in a ring shape is disposed on the bottom of the rotor  4  for providing an identification number of the rotor  4 . The control unit  20  can obtain control data suitable for a variety of rotors by extracting data from the storage area  24   a  or the EEPROM  23  that corresponds to the type of rotor detected by the rotor detector  9  while the rotor is accelerating, and temporarily storing the data in the SRAM  22 . The control unit  20  also includes the external connector (external communication port)  28  that enables data communications with the personal computer  27  by connecting the personal computer  27  to the external connector  28  provided in the main body  15  with an RS232C cable. A universal serial bus (USB), local area network (LAN), or the like are other conceivable methods of communication.  
         [0034]      FIG. 2  is a cross-sectional vies showing the drive unit  6  for driving the selected rotor. For the convenience of description,  FIG. 2  shows separate rotors in the left and right sides, when actually each rotor is symmetrical left-to-right. The drive unit  6  is provided with both an elastic shaft  30  and a high-rigidity shaft  31  that share the same axis, in other words, concentric or coaxial. The shaft to be used is dependent on the rotor selected by the user.  
         [0035]     More specifically, the drive unit  6  includes an induction motor  62  having an output shaft  66 , an end bracket  61  which also serves as a housing of the induction motor  62 , the elastic shaft  30  as a rotation drive shaft, the high-rigidity rotation shaft  31  as a support shaft, and a crown portion  33 . The elastic shaft means a shaft which causes elastic deformation such as flexure within operational rotation speed range, and the high-rigidity shaft means a shaft which is rigid within operational rotation speed range. The output shaft  66  is supported rotatably by bearings  34  provided in the end bracket  61  to sustain thrust loads from the output shaft  66 .  
         [0036]     The upper end side of the output shaft  66  is coaxially connected to the lower end of the elastic shaft  30 , and the elastic shaft  30  extends upwards in the rotor chamber  3 . The crown portion  33  is fixed to an upper end of the elastic shaft  30 . The elastic shaft  30  is designed to have a primary natural frequency within a low-speed range (several ten to several hundred rpm). The crown portion  33  has an upper end implanted with a pair of pins  32 A extending vertically upward to be engaged with one of rotors  36  and  38 , and has a lower end formed with a tapered portion  33 A.  
         [0037]     Immediately below the crown portion  33 , the high-rigidity shaft  31  is supported by a bearing  35  provided in the end bracket  61 . The high-rigidity shaft  31  is rotatable about an axis concentric (coaxial) with the elastic shaft  30  and the end bracket  61 . A hollow portion is formed in the center part of the high-rigidity shaft  31 , in order to allow the elastic shaft  30  to be inserted loosely. A tapered portion  31 A is formed at the upper portion of the shaft  31 , and the lower portion thereof forms a reduced-diameter portion which is engaged with the bearing  35 .  
         [0038]     The left half of  FIG. 2  shows a situation in which the angle rotor  36  is mounted. The angle rotor  36  is connected only to the crown portion  33 , and is spaced away from the high-rigidity shaft  31  avoiding contact nor engagement with the high-rigidity shaft  31 . A pair of pins not shown protrude downwardly from the angle rotor  36 . The pair of pins are positioned on the identical imaginary circle of the pair of pins  32 A of the crown portion  33 . Therefore, when the angle rotor  36  is positioned above the crown portion  33  and set on the crown portion  33 , the pins  32 A of the crown portion  33  contact the pins of the angle rotor  36  due to rotation of the elastic shaft  30 , so that the rotation torque of the elastic shaft  30  can be transmitted to the angle rotor  36 .  
         [0039]     The right half of  FIG. 2  shows a situation in which the swing rotor  38  is mounted. The swing rotor  38  has radially extending arms  39 , and buckets  40  are pivotally movably supported to the arms  39  through pins not shown. Note that the situation shown in  FIG. 2  shows that the buckets  40  pivotally moved horizontally due to centrifugal force, performing centrifugal separation on the samples. A base portion of each arm  39  is provided with a coupling portion having a first concave portion  39   a  and a second concave portion  39   b . The first concave portion  39   a  does not contact the top and outer peripheral portion of the crown portion  33  nor the tapered portion  33 A, and a second concave portion  39   b  has a tapered portion contactable with the tapered portion  31 A of the high-rigidity shaft  31 . A pair of pins  32 B protrude downward from the rotor  38 . The swing rotor  38  and the crown portion  33  can be engaged and connected with each other only through the pins  32 A and  32 B. The swing rotor  38  contacts the tapered portion  31 A and is mounted on the high-rigidity shaft  31 . Accordingly, if the swing rotor  38  is positioned above the crown portion  33  and set on the tapered portion  31 A, the pins  32 A of the crown portion  33  is brought into contact with the pins  32 B of the swing rotor  38  upon rotation of the elastic shaft  30 , so that the rotation torque of the elastic shaft  30  can be transmitted to the swing rotor  38 . Also, the mass of the swing rotor  38  cannot be received by the crown portion  33  but by the tapered portion  31 A of the high-rigidity shaft  31 .  
         [0040]     In case of performing centrifugal separation using the angle rotor  36  with the structure described above, power connection can be provided only between the angle rotor  36  and the crown portion  33  by merely setting the angle rotor  36  on the crown portion  33 . Therefore, the thrust load and radial load from the angle rotor  36  are received by the tapered portion  33 A of the crown portion  33 , so that the angle rotor  36  is rotationally driven by the elastic shaft  30 .  
         [0041]     On the other hand, in case of performing centrifugal separation using the swing rotor  38 , the mass of the swing rotor  38  is supported only by the high-rigidity shaft  31 , and the swing rotor  38  and the crown portion  33  are connected only by the pins  32 A and pins  32 B. Therefore, the thrust load and radial load from the swing rotor  38  are received by the tapered portion  31 A of the high-rigidity shaft  31 , and the rotation of the swing rotor  38  is supported by the bearing  35 . That is, the rotation of the swing rotor  38  generated by the elastic shaft  30  is transmitted to the high-rigidity shaft  31  which supports the mass of the swing rotor  38  via the friction force of the tapered portion  31 A. The high-rigidity shaft  31  then rotates relative to the end bracket  61  via the bearing  35 . In other words, when the swing rotor  38  is rotated, the elastic shaft  30  merely transmits the rotation torque, so that the swing rotor  38  is supported by the high-rigidity shaft  31  and rotated together with the high-rigidity shaft  31 .  
         [0042]     As has been described above, the angle rotor  36  selects automatically the elastic shaft  30  at the time of setting. On the other hand, the swing rotor  38  can be supported automatically by the high-rigidity shaft  31  at the time of setting.  
         [0043]     As shown in  FIG. 3 , the SRAM  22  of the control unit  20  is provided with storage areas  22   a - 22   k  for storing various data indicative of operation records. In the present embodiment, the swing rotor  38  is used as a high-rigidity shaft rotor and the angle rotor  36  is used as an elastic shaft rotor. However, this is only an example, and the angle rotor  36  may be used as a high-rigidity shaft rotor and the swing rotor  38  may be used as an elastic shaft rotor. The SRAM  22  includes storage areas for accumulated operating time for high-rigidity shaft rotor  22   a , accumulated number of operations for high-rigidity shaft rotor  22   b , accumulated operating time for elastic shaft rotor  22   c , accumulated number of operations for elastic shaft rotor  22   d , accumulated power-on time during idle state while door is open  22   e , accumulated power-on time during idle state while door is closed  22   f , accumulated number of pulse operations  22   g , accumulated number of program operations  22   h , accumulated number of RCF operations  22   i , accumulated power-on time by preset temperature during idle state while door is closed  22   j , accumulated number of times that door was opened and closed  22   k , and the like. While not shown in  FIG. 3 , the storage area  22   j  for storing the accumulated power-on time by preset temperature when the system is idle and the door closed is further divided into smaller storage areas based on temperature.  
         [0044]      FIG. 4  shows storage areas  23   a - 23   f  provided in the EEPROM  23  for storing the most important data in the SRAM  22  when the battery  25  becomes drained and can no longer maintain the data in the SRAM  22 . The EEPROM  23  includes accumulated operating time for high-rigidity shaft rotor  23   a , accumulated number of operations for high-rigidity shaft rotor  23   b , accumulated operating time for elastic shaft rotor  23   c , accumulated number of operations for elastic shaft rotor  23   d , accumulated power-on time during idle state while door is open  23   e , accumulated power-on time during idle state while door is closed  23   f , and the like. However, the storage areas  23   a - 23   f  are merely provided to avoid the problem of losing data in the SRAM  22  due to a depleted battery  25  and are not necessarily essential.  
         [0045]     While not requiring a battery to preserve data, the EEPROM  23  is limited in the number of times it can be reprogrammed. Hence, the EEPROM  23  cannot be frequently reprogrammed and requires a large capacity in order to copy all the data in the SRAM  22 , resulting in a high cost. However, this cost can be reduced by assigning priorities to the data and storing only the most important data in the EEPROM  23 , thereby reducing the required capacity of the EEPROM  23 .  
         [0046]     Next, a method of detecting the open and closed state of the door will be described with reference to  FIG. 5 . The door switch  8  is mounted on the main body  15  of the centrifugal separator  1  via a door lock holder  11 . A door hook  2   b  is mounted on the inner surface of the door  2  at a position in which the door hook  2   b  can be inserted through an opening  15   b  in the main body  15 .  
         [0047]     A solenoid  12  and a lock bar  13  are provided in the door lock holder  11 . The lock bar  13  is connected to the solenoid  12  and can be drawn in (a state indicated by the solid line) and pushed out (a state indicated by the dotted line) according to energizing and de-energizing of the solenoid  12 . Thus, when the centrifugal separator  1  is powered on, the CPU  21  energizes the solenoid  12  to draw in the lock bar  13  (the solid line). In this state, the door  2  can be opened and closed. When the door  2  is closed, the door hook  2   b  pushes a pivotable hinge lever  8   f  down, so that the CPU  21  can detect a door close state as described later. Subsequently, when a start switch (not shown) on the operating unit  10   b  is pushed, the CPU  21  de-energizes the solenoid  12 , so that the lock bar  13  is pushed out by a spring (not shown) provided in the solenoid  12  and is inserted into a hole (not shown) formed in the door hook  2   b. In this way, the door    2  can be maintained at a locked state (the door close state).  
         [0048]     The door switch  8  is configured of a switch unit  8   a  having the hinge lever  8   f  and a spring  8   e  that urges one end of the hinge lever  8   f  upward. As indicated by the dashed lines in  FIG. 5 , when the door  2  is in an open state, the spring  8   e  pushes the hinge lever  8   f  upward, while the opposite end of the hinge lever  8   f  presses against a button  8   b . When the door  2  is closed, the door hook  2   b  presses down on the hinge lever  8   f  in the direction indicated by an arrow in  FIG. 5 , changing the position of the hinge lever  8   f  from that indicated by the dashed line to that indicated by a solid line in  FIG. 5  and releasing the button  8   b . The switch unit  8   a  also includes terminals  8   c  and  8   d . Electricity is not conducted between the terminals  8   c  and  8   d  when the button  8   b  is not pushed by the hinge lever  8   f  and is conducted when the button  8   b  is pushed (the reverse is also possible), enabling the CPU  21  in the control unit  20  ( FIG. 1 ) to detect whether the door  2  is open or closed.  
         [0049]      FIG. 6  is a flowchart showing steps in a process for recording the accumulated number of times that the door is opened and closed according to the present embodiment. First, a method for counting the number of times that the door is opened and closed will be described. Step is hereinafter abbreviated as “S”.  
         [0050]     When the power to the centrifugal separator  1  is turned on, in S 1  the CPU  21  copies (backs up) various previously accumulated data stored in the storage areas  22   a - 22   f  of the SRAM  22  ( FIG. 3 ) to the storage areas  23   a - 23   f  of the EEPROM  23  ( FIG. 4 ).  
         [0051]     In S 2  the CPU  21  determines whether the door  2  has been moved to the closed position. If the door has been moved to the closed position (S 2 : YES), that is, the door switch  8  has been switched from the non-conducting position to the conducting position, then in S 3  the CPU  21  reads the previous accumulated number of times that the door was opened and closed from the storage area  22   k  of the SRAM  22 , adds 1 to this number to indicate the door was closed again, and stores the new value in the storage area  22   k . In S 4  the CPU  21  determines whether the accumulated open/close times for the door has reached a predetermined value (target life) If the accumulated open/close times have reached the predetermined value (S 4 : YES), then in S 5  the CPU  21  displays an alarm on the display unit  10   a  and returns to S 2 . If the accumulated open/close times have not reached the predetermined target life (S 4 : NO), then the CPU  21  skips S 5  and returns to S 2 . The process described above is repeatedly executed until the power to the centrifugal separator  1  is shut off.  
         [0052]     More specifically, when the power to the centrifugal separator  1  is turned on in S 1 , the various previously accumulated data stored in the storage areas  22   a - 22   f  is copied to the storage areas  23   a - 23   f  to be saved as backup data.  
         [0053]     When the door  2  is closed, the door switch  8  transmits a signal to the CPU  21 . Upon receiving the signal, the CPU  21  determines that one open/close operation has been performed (S 2 : YES), reads the accumulated open/close number from the storage area  22   k , adds 1 to this number to indicate that another open/close operation was performed, and re-stores the value in the storage area  22   k  (S 3 ). In S 4  the new value for the accumulated open/close number is compared to a predetermined value (estimated number of open/close operations in its life). If the number is the same as or greater than the predetermined value (S 4 : YES), then in S 5  the CPU  21  displays an alarm on the display unit  10   a , informing the user that the gas spring and other moving parts require maintenance.  
         [0054]      FIG. 7  is a flowchart showing steps in a process according to the present embodiment for recording the accumulated time in which the door is open and closed.  
         [0055]     When the power to the centrifugal separator  1  is turned on, in S 11  the CPU  21  copies (backs up) various previously accumulated data stored in the storage areas  22   a - 22   f  to the storage areas  23   a - 23   f , In S 12  the CPU  21  resets a one-second timer. In S 13  the CPU  21  determines whether one second has elapsed after the one-second timer was reset.  
         [0056]     If the CPU  21  determines that one second has elapsed (S 13 : YES), then in S 14  the CPU  21  determines whether the drive unit  6  is idle (halted) or operating. If the drive unit  6  is operating (S 14 : NO), the CPU  21  jumps to S 17 , resets the one-second timer, and returns to S 13 . However, if the drive unit  6  is idle (S 14 : YES), then in S 15  the CPU  21  determines whether the door is open. If the door is open (S 15 : YES), the CPU  21  advances to S 16 . If the door is closed (S 15 ; NO), the CPU  21  advances to S 18 . When the CPU  21  determines that the door  2  is open (S 15 : YES), in S 16  the CPU  21  reads the accumulated power-on time during an idle state while the door is open from the storage area  22   e  of the SRAM  22 , adds 1 second to this time, and re-stores the time in the storage area  22   e . Next, in S 17  the CPU  21  resets the one-second timer and returns to S 13 .  
         [0057]     However, when the door  2  is closed in S 15  (S 15 : NO), in S 18  the CPU  21  reads the accumulated power-on time during an idle state when the door is closed from the storage area  22   f  of the SRAM  22 , adds 1 second to this value, and stores the new value in the storage area  22   f . In order to record the accumulated power-on time for the preset temperature inputted via the operating unit  10   b , in S 19  the CPU  21  reads the accumulated power-on time for the preset temperature during an idle state when the door is closed, from the storage area  22   j , adds 1 second to the value, and stores the new value in the storage area  22   j . Next, in S 17  the CPU  21  resets the one-second timer and returns to S 13 .  
         [0058]     More specifically, when the power to the centrifugal separator  1  is turned on, in S 11  the CPU  21  copies previously accumulated data from the storage areas  22   a - 22   f  to the storage areas  23   a - 23   f  to be saved as backup data. Next, in S 12  the CPU  21  resets the one-second timer and in S 14  determines whether the drive unit  6  (the motor  62 ) is idle or operating based on whether power is being supplied from the drive circuit  26  to the drive unit  6 . If the drive unit  6  is operating (power is being supplied) (S 14 : NO), in S 17  the CPU  21  resets the one-second timer without storing the elapsed time in the storage area of the SRAM  22 .  
         [0059]     However, if the drive unit  6  is idle (power is not being supplied) (S 14 : YES), then the CPU  21  stores the accumulated power-on time when the door  2  is in an open state (S 16 ) and a closed state (S 18 ). Further, the CPU  21  records the accumulated power-on time for a preset temperature inputted via the operating unit  10   b  for the period in which the door is closed (S 19 ). Through these operations, the condensation state in the rotor chamber  3  and the operating state of the cooling machine  5  can be known.  
         [0060]     By repeatedly executing the process described above until the power is turned off, the centrifugal separator  1  can accurately record the open and closed status of the door when the drive unit  6  is idle. While the present embodiment describes a method for counting accumulated time using a one-second timer, any method may be used to measure time. With the process described above, it is possible to learn how much pre-cooling operation is performed by the centrifugal separator  1  having a cooling function. Here, the pre-cooling operation means operation in which the selected rotor  4  is set in the rotor chamber  3  and the rotor  4  is cooled without operating the drive unit  6 . Further, by recording accumulated data by preset temperature, the user can surmise the condensation state in the rotor chamber  3  to gauge when maintenance of the drive unit  6  is necessary, facilitating maintenance of the centrifugal separator  1 .  
         [0061]     With the centrifugal separator  1  of the present embodiment, the accumulated power-on time during an idle state when the door is open and when the door is closed, the accumulated power-on time by preset temperature during an idle state when the door is closed, and the accumulated number of times the door is opened and closed stored in the storage areas  22   e ,  22   f ,  22   j , and  22   k  can be displayed on the display unit  10   a.    
         [0062]     Further, by operating the switch  10   c  on the operating unit  10   b , the user can switch the display between the accumulated power-on time during an idle state when the door is open, the accumulated power-on time during an idle state when the door is closed, the accumulated power-on time by preset temperature during an idle state when the door is closed, and the accumulated number of times the door is opened and closed. Further, data can be transmitted to and received from an external device having a storage unit or a display unit, such as the personal computer  27 , that is connected via the external connector  28 .  
         [0063]     Next, a method for managing operation records of the drive unit  6  will be described. As described earlier, the angle rotor  36  ( FIG. 2 ) is both supported and driven to rotate by the elastic shaft  30 , while the swing rotor  38  is axially supported by the high-rigidity shaft  31 , but driven to rotate by the elastic shaft  30 . Accordingly, it is not sufficient to manage only the operation records of the drive unit  6  (accumulated operating time, accumulated number of rotations, and accumulated number of operations) without consideration for the rotor being used, as in the conventional method.  
         [0064]     With the centrifugal separator  1  according to the present embodiment, it is possible to learn precise operation records (usage records) for the bearing  34  of the elastic shaft  30  or the bearing  35  of the high-rigidity shaft  31  by recording the operation records separately for each shaft, enabling the user to replace the bearing  34  and/or the bearing  35  according to the operation records for each shaft before damage occurs. Unlike the conventional method of managing operation records of the drive unit  6  regardless of the rotor being used, the method of the present embodiment facilitates maintenance of the drive unit  6  and extends the life of the bearings  34  and  35 , unless one of the shafts  30  and  31  is used a lot more frequently or longer than the other shaft.  
         [0065]     Next, the configuration for managing the operation records of each shaft in the drive unit  6  will be described. As described earlier, the identifier (not shown) is provided on the identifying portion on the bottom of each rotor for identifying the selected rotor. Through the detection of the rotor detector  9 , the CPU  21  detects the type of rotor (rotor identification number), reads a control data set for the determined rotor stored in the storage area  24   a  of the ROM  24  and the EEPROM  23 , and determines which shaft to use for the selected rotor.  
         [0066]      FIG. 8  is a flowchart showing steps in a process according to the present embodiment for recording operation records by each shaft.  
         [0067]     When the power to the centrifugal separator  1  is turned on, in S 21  the CPU  21  copies (backs up) various previously accumulated data stored in the storage areas  22   a - 22   f  to the storage areas  23   a - 23   f . In S 22  the CPU  21  waits until the drive unit  6  begins rotating.  
         [0068]     When the drive unit  6  begins operating (S 22 : YES), in S 23  the rotor detector  9  detects the type of rotor that is rotating, and the CPU  21  determines the rotor identification number based on the detection by the rotor detector  9  and extracts the relevant rotor data from control data sets by rotor number in the storage area  24   a  or the EEPROM  23 . In S 24  the CPU  21  determines which shaft the selected rotor employs. If the CPU  21  determines in S 24  that the rotor employs the high-rigidity shaft  31  (S 24 : YES), then in S 25  the CPU  21  reads the previously accumulated number of operations for the high-rigidity shaft rotor from the storage area  22   b , adds 1 to the number, and stores the new value back in the storage area  22   b.    
         [0069]     In S 26  the CPU  21  resets a one-second timer. In S 27  the CPU  21  determines whether one second has elapsed based on the one-second timer. If one second has not elapsed (S 27 : NO), then in S 30  the CPU  21  determines whether the drive unit  6  is idle, in other words, whether rotations of the drive unit  6  have halted, and returns to S 22  if the drive unit  6  is idle (S 30 : YES). However, if the drive unit  6  is operating (S 30 : NO), then the CPU  21  returns to S 27  and loops between S 27  and S 30  until one second has elapsed. When the CPU  21  determines in S 27  that one second has elapsed (S 27 : YES), the CPU  21  advances to S 28 .  
         [0070]     In S 28  the CPU  21  reads the previously accumulated operating time for the high-rigidity shaft rotor from the storage area  22   a , adds one second to the accumulated operating time, and stores the new value back in the storage area  22   a . In S 29  the CPU  21  resets the one-second timer. In S 30  the CPU  21  again determines whether the drive unit  6  is operating and returns to S 27  if the drive unit  6  is still operating (S 30 : NO). Hence, the accumulated operating time for the high-rigidity shaft rotor is incremented until the drive unit  6  is halted. When the drive unit  6  is stopped (S 30 : YES), the CPU  21  returns to S 22  and continually monitors the drive unit  6  until the drive unit  6  again begins to rotate.  
         [0071]     If the CPU  21  determines in S 24  that the current rotor employs the elastic shaft  30  (S 24 : NO), then in S 31  the CPU  21  reads the previously accumulated number of operations for the elastic shaft rotor from the storage area  22   d , adds 1 to the value, and stores the new value back in the storage area  22   d.    
         [0072]     In S 32  the CPU  21  resets the one-second timer. In S 33  the CPU  21  determines whether one second has elapsed based on the one-second timer. If one second has not elapsed (S 33 : NO), then in S 36  the CPU  21  determines whether the drive unit  6  is idle, in other words, whether rotations of the drive unit  6  have halted, and returns to S 22  if the drive unit  6  is idle (S 36 ; YES). However, if the drive unit  6  is operating (S 36 : NO), then the CPU  21  returns to S 33  and loops between S 33  and S 36  until one second has elapsed. When the CPU  21  determines in S 33  that one second has elapsed (S 33 : YES), the CPU  21  advances to S 34 .  
         [0073]     In S 34  the CPU  21  reads the previously accumulated operating time for the elastic shaft rotor from the storage area  22   c , adds one second to this time, and stores the new value back in the storage area  22   c . In S 35  the CPU  21  resets the one-second timer. In S 36  the CPU  21  again determines whether the drive unit  6  is operating and returns to S 33  if the drive unit  6  is still operating (S 36 : NO). Hence, the accumulated operating time for the elastic shaft rotor is incremented until the drive unit  6  is halted. When the CPU  21  determines in S 36  that the drive unit  6  is idle (S 36 : YES), the CPU  21  returns to S 22  and monitors the drive unit  6  until the drive unit  6  again begins to rotate.  
         [0074]     More specifically, when the power to the centrifugal separator  1  is turned on, previously accumulated data stored in the storage areas  22   a - 22   f  is copied to the storage areas  23   a - 23   f  of the EEPROM  23  and saved as backup data (S 21 ). Next, when the drive unit  6  begins rotating (S 22 : YES), the rotor detector  9  detects the identifier provided on the bottom of the rotor to determine the type of rotor. The CPU  21  determines the rotor identification number for the detected rotor type and extracts relevant rotor information (specifications) from control data stored for the rotor in either the storage area  24   a  or the EEPROM  23  (S 23 ).  
         [0075]     Since the extracted rotor information includes information for the shaft used for the currently operating rotor, the CPU  21  can determine which shaft is being used by the currently operating rotor (S 24 ) and can increment only the accumulated number of operations for the shaft being used (S 25 , S 31 ).  
         [0076]     For example, when the current rotor employs the high-rigidity shaft (S 24 : YES), in S 25  the CPU  21  reads data stored in the storage area  22   b  for the accumulated number of operations for the high-rigidity shaft rotor, increments the value by one, and stores the result in the storage area  22   b . Each time one second elapses (S 27 : YES), in S 28  the CPU  21  reads the accumulated operating time for the high-rigidity shaft rotor from the storage area  22   a , increments the value by one second, stores the result back in the storage area  22   a , and subsequently in S 29  resets the one-second timer. Accordingly, the accumulated operating time in units of seconds can be stored for each shaft. Similarly, when the elastic shaft rotor is used (S 24 : NO), the CPU  21  increments the accumulated number of operations for the elastic shaft rotor in the storage area  22   d  (S 31 ) and the accumulated operating time for the elastic shaft rotor in the storage area  22   c  (S 34 ).  
         [0077]     While the embodiment describes one method for counting accumulated time using a one-second timer, any method may be employed for measuring time. With this process, operation records can accurately be recorded for different shafts in a centrifugal separator having both a high-rigidity shaft and an elastic shaft, thereby facilitating maintenance.  
         [0078]     Unlike the conventional method for determining the life span of a drive unit simply by managing the accumulated number of operations and accumulated operating time, the centrifugal separator  1  of the present embodiment can manage operation records for the high-rigidity shaft  31  and the elastic shaft  30  separately. Accordingly, it is possible to preset estimated values for the accumulated number of operations and operating time in the life for each of the bearings  34  and  35  and to display an alarm on the display unit  10   a  for each bearing when the life of the bearing has expired. Therefore, the bearings  34  and  35  can be replaced based on their individual operation records, and the drive unit  6  can be replaced before the elastic shaft incurs damage. Accordingly, the life of the drive unit  6  can be extended, unless one of the shafts is used a lot more frequently or longer than the other shaft.  
         [0079]     In the centrifugal separator  1  according to the present embodiment, the accumulated operating time and accumulated number of operations for the high-rigidity shaft rotor and the accumulated operating time and accumulated number of operations for the elastic shaft rotor stored in the storage areas  22   a - 22   d  can be displayed on the display unit  10   a.    
         [0080]     The content on the display unit  10   a  can be switched between each of these types of data by operating the switch  10   c  on the operating unit  10   b . Further, data can be exchanged between an external device having a storage unit or a display unit, such as the personal computer  27 , that is connected to the control unit  20  via the external connector  28 .  
         [0081]      FIG. 9  is a flowchart showing steps in a process according to the present embodiment for recording operation records by operating function.  
         [0082]     The centrifugal separator  1  has various operating functions, such as a pulse operation in which operations continue only while a pulse switch provided on the operating unit  10   b  is pressed down; a program operation (also called a memory operation) in which operations are performed by calling operating conditions stored in memory when needed; and an RCF operation in which centrifugal acceleration is set as the operating condition of the centrifugal separator instead of the rotational speed. Data for performing these operations are stored in the control unit  20 . Further, the control unit  20  controls the centrifugal separator  1  according to these various operating functions.  
         [0083]     As shown in  FIG. 9 , in S 41  the CPU  21  waits until the drive unit  6  begins rotating (S 41 : NO). Once the drive unit  6  begins rotating (S 41 : YES), the CPU  21  determines in S 42 -S 44  whether the operating function is a pulse operation, a program operation, an RCF operation, or a normal operation. If the CPU  21  determines in S 42  that the operating function is a pulse operation, then in S 45  the CPU  21  reads the accumulated number of pulse operations from the storage area  22   g  in the SRAM  22  and increments the number of pulse operations by  1 .  
         [0084]     If the CPU  21  determines in S 43  that the operating function is a program operation (S 43 : YES), then in S 46  the CPU  21  reads the accumulated number of program operations from the storage area  22   h  in the SRAM  22  and increments the number of program operations by  1 .  
         [0085]     If the CPU  21  determines in S 44  that the operating function is an RCF operation (S 44 : YES), then in S 47  the CPU  21  reads the accumulated number of RCF operations from the storage area  22   i  in the SRAM  22  and increments the number of RCF operations by 1. If the CPU  21  determines in S 42 -S 44  that the operating function is none of the pulse operation, program operation, or RCF operation (S 42 -S 44 : NO), then the CPU  21  determines that the operating function is a normal operation. In S 48  the CPU  21  determines whether the drive unit  6  has halted. If the drive unit  6  has not halted (S 48 : NO), then the CPU  21  loops back to S 48 . When the CPU  21  determines that the drive unit  6  has halted (S 48 : YES), then the CPU  21  returns to S 41 . By incrementing the values stored in the corresponding storage areas  22   g - 22   i  as described above according to the operations, the accumulated number of operations can be recorded for each operating function.  
         [0086]      FIG. 10  shows an example of content displayed on the display of a conventional centrifugal separator, while  FIGS. 11 and 12  show examples of content displayed on the display unit  10   a  of the centrifugal separator  1  according to the present embodiment.  
         [0087]     Since the centrifugal separator  1  of the present embodiment can record operation records separately for various operating functions, the user&#39;s methods and patterns of use can be known accurately. By performing maintenance according to these methods and patterns of use, it is possible to perform optimal preventative maintenance for individual centrifugal separators and to obtain accurate information regarding usage conditions of the centrifugal separators that is necessary for investigating causes of failures and for preventing their recurrence, thereby facilitating maintenance.  
         [0088]     Further, it is possible to know the operating function most frequently used by the user, making it possible to display the most frequently used operating function on the display unit  10   a  first when the power to the centrifugal separator  1  is turned on, thereby further improving user-friendliness. For example, rather than displaying an operating function list  40  ( FIG. 10 ) and having the user select from the operating function list  40  using the operating unit  10   b , the control unit  20  can display an input screen based on the most frequently used function, such as a program operation input screen  41  ( FIG. 11 ) or an RCF operation input screen  42  ( FIG. 12 ), when the power to the centrifugal separator  1  is turned on.  
         [0089]     In the centrifugal separator  1  according to the present embodiment, the accumulated number of pulse operations, accumulated number of program operations, and accumulated number of RCF operations stored in the storage areas  22   g - 22   i  can be displayed on the display unit  10   a. Further, the user can switch the display unit    10   a  between these different accumulated numbers by operating the switch  10   d  on the operating unit  10   b . Further, data can be transmitted to and received from an external device having a storage unit or a display unit, such as the personal computer  27 , that is connected via the external connector  28 .  
         [0090]     Maintenance of the cooling machine  5  can also be improved by storing, in the SRAM  22 , the accumulated time during which the control unit  20  drives the cooling machine  5 .  
         [0091]     While the invention has been described in detail with reference to the specific embodiment thereof, it would be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention.  
         [0092]     A centrifugal separator according to a first modification will be described with reference to  FIG. 13 . The first modification enables selective setting of the above-described swing rotor  38  or a second swing rotor  138  which is larger than the swing rotor  38 . Therefore, in addition to the high-rigidity shaft  31  in the above-described embodiment, a second high-rigidity shaft  231  is provided rotatably and coaxially, outside in the radial direction of the high-rigidity shaft  31 . The second high-rigidity shaft  231  is rotatably supported by the end bracket  261  via the bearing  235 . A tapered portion  231 A capable of contacting a tapered surface of the second swing rotor  138  is formed in the outer peripheral surface of the high-rigidity shaft  231 . The thrust load and the radial load from the swing rotor  138  are received by the tapered portion  231 A, and the swing rotor  138  is rotatably supported by the end bracket  261  via the bearing  235  through the second high-rigidity shaft  231 . The swing rotor  138  is supported by the second high-rigidity shaft  231  and rotated together with the high-rigidity shaft  231 . The large swing rotor  138  is supported by the bearing  235  which has a large load resistive capacity.  
         [0093]     A centrifugal separator according to a second modification will be described with reference to  FIG. 14 . In the second modification, the length of upward protrusion of the output shaft  166  of the motor  62  is increased, and an elastic rotation shaft  30  is coaxially coupled with the top end portion of the protrusion. Further, a hollow high-rigidity rotation shaft  331  is coaxially coupled with the outer circumferential surface of the top end portion of the output shaft  166 . A tapered surface  331 A is formed in the outer peripheral surface of the high-rigidity rotation shaft  331  for receiving the swing rotor  38 . When the swing rotor  38  is set, the tapered surface of the concave portion of the swing rotor  38  contacts the tapered surface  331 A of the high-rigidity rotation shaft  331 . Rotation torque of the induction motor  62  is directly transmitted to the high-rigidity rotation shaft  331 , so that the rotation force can be transmitted to the swing rotor  38  by the friction force of the tapered surface  331 A. Accordingly, in the second modification, the high-rigidity rotation shaft  331  serves as drive shaft when the swing rotor  38  is mounted.  
         [0094]     A centrifugal separator according to a third modification will be described with reference to  FIG. 15 . In the embodiment and modifications described above, each of the high-rigidity shafts  31 ,  231 , and  331  is a rotation shaft. However, in the third modification, a high-rigidity shaft as a support shaft is a fixed (unrotatable) shaft  431 . A bearing support portion of an end bracket  461  is used directly as the fixed shaft  431 . An outer peripheral surface of the fixed shaft  431  in an upper end side forms a reduced outer diameter portion, and two bearings  335  are assembled to the reduced outer diameter portion. Further, an inner peripheral surface of a concave portion  338   b  in a coupling portion  337  of a swing rotor  338  is engagable with an outer race of the bearings  335 , so that the swing rotor  338  is rotatable about the bearing support portion (fixed shaft)  431  via the bearings  335 .  
         [0095]     In addition, the motor serving as the power generator is not limited to the induction motor but various motors are available, e.g., an electric motor such as a DC motor, and a fluid-operated motor such as an air turbine and an oil turbine as long as rotation torque can be obtained.  
         [0096]     Further, rotors are not limited to those shown in the foregoing embodiment and modifications but various rotors are available as long as those rotors have shapes which fit into the crown portion or the tapered portion.