Abstract:
An auxiliary power supply unit, which is attachable to and detachable from an apparatus, includes a charge unit configured to store electric charge, a terminal configured to establish electrical connection for discharge with the apparatus, and a discharge unit situated between the charge unit and the terminal to provide a discharge path that electrically connect the charge unit to the apparatus, the discharge path having an open/closed state thereof controlled during a period when an electric power is supplied from the apparatus, the discharge path being opened in response to a stoppage of supply of the electric power from the apparatus.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to an auxiliary power unit and image forming apparatus.  
         [0003]     2. Description of the Related Art  
         [0004]     Image forming apparatuses are provided with an image forming unit for forming a toner image on a record medium and a fuser unit or the like for fixing the toner image by pressing and heating the record medium on which the toner image is formed. The fuser unit includes fusing rollers for heating the record medium, and these fusing rollers are heated to a predetermined temperature by a heater. In so doing, the heater consumes a significant amount of power.  
         [0005]     In image forming apparatuses, especially in high-speed image forming apparatuses, the electric power may sometimes be set to 200 V in order to obtain a high power. A commercial power typically used in offices in Japan is 100 V (15 A). In order to set the power of an image forming apparatus to 200 V, thus, a special electric work needs to be performed with respect to the power supply facility at the place where the image forming apparatus is installed. This is not convenient, and is not an effective way to cope with the situation.  
         [0006]     Some image forming apparatuses thus use a 100-V power, and drop the speed of image formation or temporarily suspend the operation of image formation when the temperature of the fusing rollers drops to such temperature as to cause a failure of fusing due to the lack of electric power supply. This however reduces productivity. It should be noted that the time required for the fusing rollers to reach a predetermined temperature after the power-on is dependent on the capacity of the power supply. Because of this, the operation of image formation cannot be performed for a longer period of time until the fusing rollers reach a predetermined temperature than when a 200-V power is used. This is another factor to reduce the productivity.  
         [0007]     In order to overcome the problem of the lowering of productivity, the technologies disclosed in Patent Document 1, Patent Document 2, and Patent Document 3 may be used.  
         [0008]     Patent Document 1 discloses a technology in which a battery is provided as a built-in component in an image forming apparatus, and supplies power to the fuser unit when the temperature of the fusing rollers drops below a predetermined temperature at the time of consecutive copying, thereby eliminating a down time of the image forming apparatus.  
         [0009]     Patent Document 2 discloses a technology in which a first heater driven by an alternating current power supply and a second heater driven by a battery charged by a charger are provided, thereby reducing a startup time of the fuser unit.  
         [0010]     Patent document 3 discloses a technology in which an auxiliary power is provided detachably for the image forming apparatus, thereby preventing the leakage of the electrolytic solution of the secondary battery from damaging surrounding components.  
         [0011]     More often than not, a commercial power supply is not only used for an image forming apparatus but also used for other office equipment attached thereto. In such cases, a large electric current may flow into the breaker at the time of power-on of the image forming apparatus or return from the power consumption mode, resulting in the severing of the breaker. In order to avoid such a problem, typically, the maximum power consumption of the image forming apparatus is specified in the operation manual, catalog, or the like.  
         [0012]     Some users (clients) of image forming apparatuses may not feel inconvenience even if the speed of image formation drops at the time of consecutive image formation, or even if there is a break time in the image forming operation. Further, there may be users who do not mind even if the startup time is lengthy. Also, the problem of breaker severing may differ depending on the usage of power supply at user offices. Moreover, if an auxiliary power supply and associated control circuit are provided in an image forming apparatus as in a conventional configuration, an expensive price of the image forming apparatus becomes an issue.  
         [0013]     Accordingly, in order to achieve price reduction with respect to image forming apparatuses, it is preferable to add an auxiliary power supply and control circuit or the like in such a manner as to conform to the user usage of the apparatus, user usage of the power supply, user needs, etc.  
         [0014]     In this manner, it is desirable to select a balance between higher performance and lower price according to user needs, by providing a unitized structure of an auxiliary power supply and control circuit or the like such that the unit is detachable from the image forming apparatus.  
         [0015]     [Patent Document 1] Japanese Patent Application Publication No. 58-54367  
         [0016]     [Patent Document 2] Japanese Patent Application Publication No. 63-150967  
         [0017]     [Patent Document 3] Japanese Patent Application Publication No. 2001-66926  
         [0018]     In the case of a unitized structure of an auxiliary power supply and control circuit or the like, the power required by the image forming apparatus is large, so that safety in particular is of prime importance. A conventional unit detachable from an image forming apparatus poses danger if the terminals for electrical connection with the image forming apparatus are touched by a finger or the like after the unit is detached from the image forming apparatus.  
         [0019]     Accordingly, there is a need for an auxiliary power supply unit that is safe, and also a need for an image forming apparatus configured such that the auxiliary power supply unit is detachable therefrom.  
       SUMMARY OF THE INVENTION  
       [0020]     It is a general object of the present invention to provide an auxiliary power supply unit and image forming apparatus that substantially obviate one or more problems caused by the limitations and disadvantages of the related art.  
         [0021]     To achieve these and other advantages in accordance with the purpose of the invention, the invention provides an auxiliary power supply unit, which is attachable to and detachable from an apparatus, and includes a charge unit configured to store electric charge, a terminal configured to establish electrical connection for discharge with the apparatus, and a discharge unit situated between the charge unit and the terminal to provide a discharge path that electrically connect the charge unit to the apparatus, the discharge path having an open/closed state thereof controlled during a period when an electric power is supplied from the apparatus, the discharge path being opened in response to a stoppage of supply of the electric power from the apparatus.  
         [0022]     According to another aspect of the present invention, an image forming apparatus includes an auxiliary power supply unit, which is attachable to and detachable from a main body of the apparatus, the auxiliary power supply unit including a charge unit configured to store electric charge, a terminal configured to establish electrical connection for discharge with the main body of the apparatus, and a discharge unit situated between the charge unit and the terminal to provide a discharge path that electrically connect the charge unit to the main body of the apparatus, the discharge path having an open/closed state thereof controlled during a period when an electric power is supplied from the main body of the apparatus, the discharge path being opened in response to a stoppage of supply of the electric power from the main body of the apparatus.  
         [0023]     According to at least one embodiment of the present invention, the auxiliary power supply unit is provided with the discharge unit that is controllably driven based on the electrical power supplied from the main body of the apparatus. Upon being detached from the main body of the apparatus, the discharge unit of the auxiliary power supply unit no longer receives the electric power, resulting in the discharge path being opened. In the auxiliary power supply unit, therefore, the discharge path is blocked so as to decouple, from the charge unit, the discharge terminal, which is provided for electrical connection with the main body of the apparatus. Physical contact with the terminal thus does not poser any danger.  
         [0024]     According to at least one embodiment of the present invention, it is possible to provide an auxiliary power supply unit that is safe and also to provide an image forming apparatus to which such auxiliary power supply unit is attachable. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0025]     Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings, in which:  
         [0026]      FIG. 1  is a cross-sectional side view showing a schematic configuration of a color image forming apparatus;  
         [0027]      FIG. 2  is a cross-sectional side view showing a schematic configuration of a fuser unit;  
         [0028]      FIG. 3  is an exterior perspective view showing a schematic configuration of a capacitor device;  
         [0029]      FIG. 4  is a block diagram showing a schematic configuration of electrical connections of individual parts of the color image forming apparatus in which the capacitor device is provided;  
         [0030]      FIG. 5  is a block diagram showing an example of the schematic configuration of electrical connections between the capacitor device and various units provided in the color image forming apparatus;  
         [0031]      FIG. 6  is a block diagram showing an example of the schematic configuration of electrical connections between the capacitor device and various units provided in the color image forming apparatus;  
         [0032]      FIG. 7  is a block diagram showing an example of the schematic configuration of electrical connections between the capacitor device and various units provided in the color image forming apparatus;  
         [0033]      FIG. 8  is an exterior perspective view showing the schematic configuration of a capacitor device; and  
         [0034]      FIG. 9  is a block diagram showing the schematic configuration of capacitor devices connected in series. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0035]     In the following, embodiments of the present invention will be described with reference to the accompanying drawings.  
       Embodiment 1  
       [0036]     A first embodiment of the present invention will be described with reference to  FIG. 1  through  FIG. 7 .  
         [0037]     An image forming apparatus according to this embodiment includes a plurality of photoconductors capable of carrying respective toner images corresponding to the color composition, and the toner images formed on these photoconductors are transferred one over another onto an intermediate transfer unit (e.g. an intermediate transfer belt), followed by further transferring the superimposed image onto a record medium such as a record sheet, thereby forming a multi-color image. Such color image forming apparatus may be a color copier, for example. It should be noted, however, that the image forming apparatus is not limited to a color copier, but may as well be a black-and-white copier, a color printer, a black-and-white printer, a facsimile device, a printing press, etc.  
         [0038]      FIG. 1  is a cross-sectional side view showing a schematic configuration of a color image forming apparatus. As shown in  FIG. 1 , a color image forming apparatus  1  includes an image forming unit  1 A provided at the center thereof, a sheet feeder unit  1 B provided beneath the image forming unit  1 A, and a document scan unit  1 C provided over the image forming unit  1 A.  
         [0039]     The document scan unit  1 C includes a scanner  1 C 2  having a document platform  1 C 1  on which a document is placed, and further includes an automatic document feeding unit  1 C 3  provided on the document platform  1 C 1 . The scanner  1 C 2  scans document images (image information) from the document placed on the document platform  1 C 1 . The automatic document feeding unit  1 C 3  supplies document sheets to the document platform  1 C 1 , and is further configured to flip over the document sheets supplied to the document platform  1 C 1 . This makes it possible to scan document images from both the front and back surfaces of the document sheets.  
         [0040]     The image forming unit  1 A includes an intermediate transfer belt  2  having a surface thereof extending in a horizontal direction, and further includes a plurality of photoconductors  3 Y,  3 M,  3 C, and  3 B, which are arranged along the extending surface of the intermediate transfer belt  2  and operable to carry respective toner images corresponding to the color separation colors and complementary colors (yellow, magenta, cyan, black).  
         [0041]     The photoconductors  3 Y,  3 M,  3 C, and  3 B are formed in a drum shape, and are configured to rotate in the same direction (counterclockwise in  FIG. 1 ). Around the photoconductors  3 Y,  3 M,  3 C, and  3 B are provided charging units  4 Y,  4 M,  4 C and  4 B, a writing unit  5 , developing units  6 Y,  6 M,  6 C, and  6 B, primary transfer units  7 Y,  7 M,  7 C, and  7 B, and cleaning units  8 Y,  8 M,  8 C, and  8 B, which perform image forming processes during the rotation of the photoconductors  3 Y,  3 M,  3 C, and  3 B.  
         [0042]     The charging units  4 Y,  4 M,  4 C and  4 B uniformly charge the surfaces of the photoconductors  3 Y,  3 M,  3 C, and  3 B, respectively. The writing unit  5  shines light beams on the photoconductors  3 Y,  3 M,  3 C, and  3 B to form electrostatic latent images in response to the image information obtained by the scanner  1 C 2  from a document placed on the document platform  1 C 1  or the image information supplied from a computer (not shown) connected to the color image forming apparatus  1 .  
         [0043]     The developing units  6 Y,  6 M,  6 C, and  6 B supply toner to the electrostatic latent images formed on the photoconductors  3 Y,  3 M,  3 C, and  3 B, respectively, thereby forming toner images on the surfaces thereof. The primary transfer units  7 Y,  7 M,  7 C, and  7 B transfer, to the intermediate transfer belt  2 , the toner images formed on the surfaces of the photoconductors  3 Y,  3 M,  3 C, and  3 B, respectively. In so doing, the toner images of the photoconductors  3 Y,  3 M,  3 C, and  3 B are superimposed one over another on the intermediate transfer belt  2 .  
         [0044]     The intermediate transfer belt  2  is hooked around a plurality of rollers  2 A,  2 B, and  2 C, and is configured to shift in the same direction at the positions where the photoconductors  3 Y,  3 M,  3 C, and  3 B are placed. The rollers  2 A and  2 B serve to provide the extending surface of the intermediate transfer belt  2 . The remaining roller  2 C is placed opposite a secondary transfer unit  9  across the intermediate transfer belt  2 . Further, a cleaning unit  10  is provided at the position to face the intermediate transfer belt  2  so as to clean the intermediate transfer belt  2 .  
         [0045]     The secondary transfer unit  9  includes charging drive rollers  9 A and  9 B, and further includes a transfer belt  9 C hooked around the charging drive rollers  9 A and  9 B to shift in the same direction as the intermediate transfer belt  2  at the secondary transfer position. The charging drive roller  9 A charges the transfer belt  9 C, thereby transferring, onto a sheet, a multi-color image superimposed on the intermediate transfer belt  2  or a monochrome image carried on the intermediate transfer belt  2  The sheet feeder unit  1 B includes a plurality of sheet feeder cassettes  1 B 1  for storing sheets, a plurality of conveyer rollers  1 B 2  placed along the conveyer path to which the sheets are supplied from the sheet feeder cassettes  1 B 1 , and a resist roller  1 B 3  situated upstream relative to the secondary transfer position (in terms of the sheet travel direction).  
         [0046]     Further, the sheet feeder unit  1 B includes a manual feed tray  1 B 4  provided as part of the side wall of the image forming unit  1 A operable to flip open, and further includes a forwarding roller  1 B 5 . With this provision, sheets placed on the manual feed tray  1 B 4  can be supplied to the secondary transfer position, separately from the conveyer path of the sheets supplied from the sheet feeder cassettes  1 B 1 . The sheet conveyer path extending from the manual feed tray  1 B 4  merges into the sheet conveyer path extending between the sheet feeder cassettes  1 B 1  and the resist roller  1 B 3 . Sheets coming from either conveyer path undergo resist timing setting by the resist roller  1 B 3 .  
         [0047]     A fuser unit  11  (the detail of which will later be described) for fixing a toner image on a sheet and an ejecting unit  12  for ejecting the sheet having the toner image fixed thereon are provided downstream relative to the secondary transfer unit (in terms of the sheet travel direction). Moreover, the color image forming apparatus  1  further includes a front door (not shown) for exposing the interior for the handling of jamming or the like, and a capacitor device  13  (the detail of which will later be described) for supplying an electric power to the fuser unit  11 . The capacitor device  13  is configured such as to be detachable from the color image forming apparatus  1 .  
         [0048]     The ejecting unit  12  includes a conveyer path switching claw  12 A for switching the sheet conveyer directions, a sheet ejection tray  12 B onto which sheets are ejected, and a reversing conveyer path  12 C for reversing the front side and back side of a sheet for use in duplex printing. The ejecting unit  12  uses the conveyer path switching claw  12 A to switch the sheet conveyer directions so as to convey the sheet passing through the fuser unit  11  either to the conveyer path leading to the sheet ejection tray  12 B or to the reversing conveyer path  12 C.  
         [0049]     In the color image forming apparatus  1  as described above, electrostatic latent images are formed on the photoconductors  3 Y,  3 M,  3 C, and  3 B that are uniformly charged, in response to the image information supplied from a document placed on the document platform  1 C 1  or in response to the image information supplied from a computer. The electrostatic latent images are then visualized by the developing units  6 Y,  6 M,  6 C, and  6 B, followed by transferring the toner images onto the intermediate transfer belt  2  through a primary transfer.  
         [0050]     The toner images transferred onto the intermediate transfer belt  2  through a primary transfer are transferred through a secondary transfer onto a sheet supplied from the sheet feeder unit  1 B. Such secondary transfer is done straight through in the case of a monochrome image, and is done by superimposing images through repeated primary transfers and by transferring the superimposed image onto the sheet in the case of a multi-color image. The sheet after the secondary transfer is treated by the fuser unit  11  to fuse the image onto the sheet. Thereafter, the sheet is supplied to the sheet ejection tray  12 B or to the resist roller  1 B 3  again after the reversal thereof.  
         [0051]      FIG. 2  is a cross-sectional side view showing a schematic configuration of the fuser unit  11 . As shown in  FIG. 2 , the fuser unit  11  includes a fusing roller  21  serving as a fusing member, a pressing roller  22  serving as a pressing member, and a pressing unit (not shown) for pressing the pressing roller  22  on the fusing roller  21  with a constant pressure. The fusing roller  21  and the pressing roller  22  are driven to rotate by a drive mechanism (not shown).  
         [0052]     The fuser unit  11  includes three heaters HT 1 , HT 2 , and HT 3 , and further includes two temperature sensors TH 1  and TH 2  such as thermistors. The heaters HT 1 , HT 2 , and HT 3  are situated inside the fusing roller  21 , for example, to heat the fusing roller  21  from inside, thereby providing heat to the fusing roller  21 . The temperature sensors TH 1  and TH 2  are placed in contact with the surface of the fusing roller  21 , thereby detecting the surface temperature (fusing temperature) of the fusing roller  21 . The temperature sensor TH 1  is positioned in a measurement area corresponding to the heater HT 1  and the heater HT 2 . The temperature sensor TH 2  is positioned in a measurement area corresponding to the heater HT 3 .  
         [0053]     The heaters HT 1  and HT 2  are main heaters for heating the fusing roller  21 , and are turned on when the temperature of the fusing roller  21  is below a target temperature. The heater HT 3  is turned on at the time of warming up of the fuser unit  11  such as when the main power of the color image forming apparatus  1  is turned on or when a startup operation is performed to make copying available after the “off” mode for energy conservation. The heater HT 3  is also turned on when the temperature of the fusing roller  21  is below the target temperature at the time of image formation. The heater HT 3  is an auxiliary heater for heating the fusing roller  21 .  
         [0054]     In the fuser unit  11  as described above, a sheet having a toner image thereon passes through a nip portion between the fusing roller  21  and the pressing roller  22 . At the time of the passing, the fusing roller  21  and the pressing roller  22  apply heat and a pressure. As a result, the toner image is fixed on (fused with) the sheet.  
         [0055]      FIG. 3  is an exterior perspective view showing a schematic configuration of the capacitor device  13 . As shown in  FIG. 3 , the capacitor device  13  includes a capacitor unit  31  and a capacitor control unit  32  for controlling parts of the capacitor unit  31 . Further provided are drawer connectors  33  for providing electrical couplings with the color image forming apparatus  1 . The capacitor unit  31  and the capacitor control unit  32  are coupled to each other via coupling connectors  34  and electrical wires  35 .  
         [0056]     The capacitor unit  31  includes a capacitor bank  36 , a discharge unit  37 , and a capacitor charging unit (not shown). The capacitor bank  36  is coupled to the discharge unit  37  and the capacitor charging unit via the coupling connectors  34  and the electrical wires  35 . The capacitor control unit  32  drives and controls the discharge unit  37 .  
         [0057]     The capacitor bank  36  includes a plurality of capacitor cells  38  connected in series and a balance circuit board  40  having a plurality of balance circuits  39  for uniformly charging the respective capacitor cells  38 . As the capacitor cells  38 , electric double-layer capacitors for storing electric power are used, for example.  
         [0058]     The capacitor charging unit includes charting units (not shown) for charging the plurality of capacitor cells  38  connected in series. The discharge unit  37  includes a discharge unit (not shown) serving as a supply unit for supplying the electric power charged (stored) in the capacitor cells  38  to the fuser unit  11 , i.e., to the heater HT 3 , and further includes relay connectors  41  or the like for connecting a plurality of capacitor units  31 . The capacitor control unit  32  also includes expansion connectors  42  for connecting a plurality of capacitor units  31 .  
         [0059]     According to this embodiment, the capacitor unit  31  is provided with the discharge unit  37  and the capacitor charging unit separate from each other. This is not a limiting example. For example, a charging/discharging unit may be provided. Alternatively, the capacitor unit  31  may be provided only with the discharge unit  37 . In such a case, a capacitor charting unit  59  is provided as a built-in component in the color image forming apparatus  1 .  
         [0060]     The capacitor device  13  as described above is provided as a unitized structure detachable from the color image forming apparatus  1 . The capacitor device  13  may be fixed to the color image forming apparatus  1  via screws or the like, and is electrically coupled to the color image forming apparatus  1  via the drawer connectors  33 . The drawer connectors  33  of the capacitor device  13  are connected to the drawer connectors (not shown) of the color image forming apparatus  1 , thereby providing electrical coupling between the capacitor control unit  32  and the color image forming apparatus  1 . The drawer connectors  33 , coupling connectors  34 , electrical wires  35 , and so on serve as an output means.  
         [0061]      FIG. 4  is a block diagram showing a schematic configuration of electrical connections of each part of the color image forming apparatus  1  in which the capacitor device  13  is provided.  
         [0062]     As shown in  FIG. 4 , the color image forming apparatus  1  includes a controller  51  for performing overall control, an operation unit  52  coupled to the controller  51 , and an engine control unit  53  serving as an image formation controlling unit. The engine control unit  53  is coupled to the capacitor control unit  32  of the capacitor device  13  via a serial interface (UART).  
         [0063]     The controller  51  includes a CPU (not shown), a ROM (not shown) for storing various programs executed by the CPU, and a RAM (not shown) serving as a work memory for use by the CPU, and implements the functions of a plurality of applications such as a scanner application, facsimile application, printer application, copy application, etc. The controller  51  attends to the overall control of the system. The operation unit  52  includes an operation panel, LCD, and the like (not shown). The operation unit  52  receives instructions from an operator, and displays settings and statuses to the operator. The engine control unit  53  includes a CPU, ROM, RAM, and the like (not shown), and mainly controls the image forming unit  1 A and the fuser unit  11 .  
         [0064]     The fuser unit  11  includes three heaters HT 1 , HT 2 , and HT 3 . The heaters HT 1  and HT 2  are implemented as AC heaters. The heater HT 3  is implemented as a DC heater.  
         [0065]     The heaters HT 1  and HT 2  are coupled to an AC power supply (commercial power supply)  54  via triacs (TRIAC 1  and TRIAC 2 )  56  and thermostats (THST 1  and THST 2 )  55  for the prevention of overheating. Electric power is supplied via this path.  
         [0066]     The heaters HT 1  and HT 2  are connected in series to the respective thermostats  55  for overheating prevention. The heaters HT 1  and HT 2  are controlled individually as to their on/off states by the triacs  56  based on the on/off signals TR 1  and TR 2 , respectively, supplied from the engine control unit  53 .  
         [0067]     An output signal Th 1  from the temperature sensor TH 1  is supplied to an A/D converter (not shown) of the engine control unit  53 . The CPU of the engine control unit  53  detects the temperature of the fusing roller  21  based on the input signal Th 1  from the temperature sensor TH 1 , and supplies the on/off signals TR 1  and TR 2  to the triacs  56 . With this provision, the temperature control of the fusing roller  21  is performed.  
         [0068]     The heater HT 3  is coupled to the capacitor device  13 , i.e., to the capacitor bank  36  comprised of the capacitor cells  38  connected in series. The heater HT 3  is controlled as to its on/off states by the discharge relay  57  and discharge FET  58  of the discharge unit  37 . Namely, the discharge unit  37  supplies a direct current electric power to the heater HT 3  from the capacitor cells  38  to make the heater HT 3  generate heat (“heater on”).  
         [0069]     The capacitor cells  38  are coupled to the AC power supply  54  via the capacitor charging unit  59 . The capacitor charging unit  59  of the capacitor device  13  receives an electric power from the AC power supply  54  to charge the plurality of capacitor cells  38 .  
         [0070]     The output signal Th 2  from the temperature sensor TH 2  is supplied to the A/D converter of the engine control unit  53 . The CPU of the engine control unit  53  detects the temperature of the fusing roller  21  based on the input signal Th 2  from the temperature sensor TH 2 , and supplies on/off signals T 1  and T 2  for provision to the discharge relay  57  and the discharge FET  58  to the capacitor control unit  32  via the serial interface. The capacitor control unit  32  supplies the on/off signals T 1  and T 2  to the discharge unit  37  for provision to the discharge relay  57  and the discharge FET  58 , respectively. With this provision, the temperature control of the fusing roller  21  is performed.  
         [0071]     The capacitor control unit  32  and the engine control unit  53  are coupled to each other via a photo-coupler. The photo-coupler is provided because of the large voltage of the capacitor bank  36 , and improves noise-related performance and voltage-related performance. When the voltage of the capacitor bank  36  needs to be monitored, for example, the engine control unit  53  makes the capacitor control unit  32  monitor the voltage by use of control commands. Since the engine control unit  53  does not directly monitor the voltage of the capacitor bank  36 , the noise-related performance and voltage-related performance are improved.  
         [0072]     The schematic configuration of the capacitor device  13  shown in  FIG. 4  is merely an example. As shown in schematic configurations illustrated in  FIG. 5  through  FIG. 7 , various units of the capacitor device  13  shown in  FIG. 4  may alternatively be provided on the side of the color image forming apparatus  1 . The schematic configurations of  FIG. 5  through  FIG. 7  illustrate only a relevant portion of the schematic configuration of  FIG. 4  necessary for the explanation purpose.  
         [0073]      FIG. 5  is a block diagram showing an example of the schematic configuration of electrical connections between the capacitor device  13  and various units provided in the color image forming apparatus  1 . The schematic configuration of  FIG. 5  illustrates a structure corresponding to the schematic configuration of  FIG. 4 .  
         [0074]     In the schematic configuration of  FIG. 5 , the color image forming apparatus  1  is provided with a DC power supply  61  and the like. The DC power supply  61  is coupled to the AC power supply  54 . The discharge unit  37  of the capacitor device  13  operates based on the power supplied from the DC power supply  61 . The capacitor bank  36  of the capacitor device  13  is coupled to the AC power supply  54  via the capacitor charging unit  59 . The capacitor charging unit  59  receives an electric power from the AC power supply  54  to charge the plurality of capacitor cells  38 .  
         [0075]     The discharge unit  37  is opened or closed under the drive control of the capacitor control unit  32  shown in  FIG. 4 . When the discharge unit  37  is closed, the electric power charged in the capacitor cells  38  is supplied to the heater HT 3 . When the discharge unit  37  is opened, the electric power charged in the capacitor cells  38  is not supplied to the heater HT 3 .  
         [0076]     When the capacitor device  13  is detached from the color image forming apparatus  1 , the discharge unit  37  is opened since the power supply from the DC power supply  61  is stopped. As a result, the discharge path of the capacitor device  13  is blocked. In the capacitor device  13 , thus, the terminals (points of connection) for discharge and electrical connection with the color image forming apparatus  1  are separated from the capacitor cells  38 . Physical contact with these terminals thus does not pose any danger.  
         [0077]      FIG. 6  is a block diagram showing an example of the schematic configuration of electrical connections between the capacitor device  13  and various units provided in the color image forming apparatus  1 . In the schematic configuration of  FIG. 6 , the capacitor charging unit  59 , which is provided in the capacitor device  13  in the schematic configuration of  FIG. 5 , is provided in the color image forming apparatus  1 .  
         [0078]     In the schematic configuration of  FIG. 6 , the color image forming apparatus  1  is provided with the capacitor charging unit  59 , the DC power supply  61 , and the like. The discharge unit  37  of the capacitor device  13  operates based on the power supplied from the DC power supply  61 . The capacitor bank  36  of the capacitor device  13  is coupled to the AC power supply  54  via the capacitor charging unit  59  of the color image forming apparatus  1 . The capacitor charging unit  59  receives an electric power from the AC power supply  54  to charge the plurality of capacitor cells  38 .  
         [0079]     The discharge unit  37  is opened or closed under the drive control of the capacitor control unit  32  shown in  FIG. 4 . When the discharge unit  37  is closed, the electric power charged in the capacitor cells  38  is supplied to the heater HT 3 . When the discharge unit  37  is opened, the electric power charged in the capacitor cells  38  is not supplied to the heater HT 3 .  
         [0080]     When the capacitor device  13  is detached from the color image forming apparatus  1 , the discharge unit  37  is opened since the power supply from the DC power supply  61  is stopped. As a result, the discharge path of the capacitor device  13  is blocked. In the capacitor device  13 , thus, the terminals (points of connection) for discharge and electrical connection with the color image forming apparatus  1  are separated from the capacitor cells  38 . Physical contact with these terminals thus does not pose any danger.  
         [0081]      FIG. 7  is a block diagram showing an example of the schematic configuration of electrical connections between the capacitor device  13  and various units provided in the color image forming apparatus  1 . In the schematic configuration of  FIG. 7 , the discharge unit  37  and the capacitor charging unit  59 , which are provided in the capacitor device  13  in the schematic configuration of  FIG. 5 , are provided in the color image forming apparatus  1 .  
         [0082]     In the schematic configuration of  FIG. 7 , the color image forming apparatus  1  is provided with the discharge unit  37 , the capacitor charging unit  59 , the DC power supply  61 , and the like. The DC power supply  61  is coupled to the AC power supply  54 . The discharge unit  37  operates based on the power supplied from the DC power supply  61 . The capacitor bank  36  of the capacitor device  13  is coupled to the AC power supply  54  via the capacitor charging unit  59  of the color image forming apparatus  1 . The capacitor charging unit  59  receives an electric power from the AC power supply  54  to charge the plurality of capacitor cells  38 .  
         [0083]     The discharge unit  37  is opened or closed under the drive control of the capacitor control unit  32  shown in  FIG. 4 . When the discharge unit  37  is closed, the electric power charged in the capacitor cells  38  is supplied to the heater HT 3 . When the discharge unit  37  is opened, the electric power charged in the capacitor cells  38  is not supplied to the heater HT 3 .  
         [0084]     When the capacitor device  13  is detached from the color image forming apparatus  1 , the terminals (points of connection) of the capacitor device  13  for discharge and electrical connection with the color image forming apparatus  1  are not separated from the capacitor cells  38 . As a result, the voltage of the capacitor bank  36  appears at these terminals, and physical contact with these terminals may result in an electrical shock.  
         [0085]     As described above, the schematic configurations shown in  FIG. 5  and  FIG. 6  are safer than the schematic configuration shown in  FIG. 7 . In this manner, the present embodiment provides an auxiliary power supply unit that is safe. In this auxiliary power supply unit, the discharge path is automatically blocked after the unit is detached from the color image forming apparatus  1 , so that physical contact with the terminals of the unit for electrical connection with the color image forming apparatus  1  does not pose any danger.  
         [0086]     Further, according to the present embodiment, the capacitor device  13  is implemented as an independent and separate module. With this configuration, it is easy to change the amount of power supply in the color image forming apparatus  1  by selectively attaching or detaching the capacitor device  13 . This makes it possible to adjust performance (e.g., CPM: the copy speed indicative of the number of copied sheets per minute) by adjusting the amount of electric power of the auxiliary power supply according to the user usage of apparatus, the user usage of power supply, user needs, etc.  
         [0087]     When the capacitor device  13  inclusive of the capacitor control unit  32  and the discharge unit  37  and the like is provided as an independent module, there is no need to provide the capacitor control unit  32 , the discharge unit  37 , and the like in the color image forming apparatus  1 . This achieves price reduction with respect to the color image forming apparatus  1 .  
       Embodiment 2  
       [0088]     A second embodiment of the present invention will be described with reference to  FIG. 8 .  
         [0089]     This embodiment basically has the same configuration as the first embodiment. In the following, a description will be given of portions where the present embodiment differs from the first embodiment. In this embodiment, the same portions as those described in the first embodiment are referred to by the same numerals, and a description thereof will be omitted.  
         [0090]      FIG. 8  is an exterior perspective view showing the schematic configuration of a capacitor device  13   a.  The capacitor device  13   a  of  FIG. 8  includes two capacitor banks  36 , and also includes two discharge units  37 . The two capacitor banks  36  are coupled to the two discharge units  37 , respectively. The two discharge units  37  are coupled to the capacitor control unit  32 . The exchange of signals between the discharge units  37  and the capacitor control unit  32  is the same as in the first embodiment.  
         [0091]     In the capacitor device  13   a,  the two capacitor banks  36  may be connected in series, for example. According to this embodiment as described above, the provision of the two capacitor banks  36  makes it easier to change the amount of electric power of the auxiliary power supply. With this provision, it is possible to adjust performance by adjusting the amount of electric power of the auxiliary power supply according to the user usage of apparatus, the user usage of power supply, user needs, etc.  
         [0092]     When the capacitor device  13  inclusive of the capacitor control unit  32  and the discharge unit  37  and the like is provided as an independent module, there is no need to provide the capacitor control unit  32 , the discharge unit  37 , and the like in the color image forming apparatus  1 . This achieves price reduction with respect to the color image forming apparatus  1 .  
         [0093]     In the present embodiment, the two capacitor banks  36  are connected in series. This is not a limiting example, and the two capacitor banks  36  may alternatively be connected in parallel. When the two capacitor banks  36  are connected in series, a higher voltage is necessary to charge the capacitor cells  38 .  
         [0094]     When the capacitor banks  36  are connected in parallel, also, the capacity of the power supply needs to be large in order to charge the capacitor cells  38 . Achieving this requires an expensive capacitor charging unit  59 . As in the present embodiment, thus, it is preferable to provide the capacitor charging unit  59  separately for each capacitor bank  36 .  
       Embodiment 3  
       [0095]     A third embodiment of the present invention will be described with reference to  FIG. 9 . This embodiment has a configuration in which capacitor devices each identical to the capacitor device  13  of the first embodiment are connected in series. In the following, a description will be given of portions where the present embodiment differs from the first embodiment. In this embodiment, the same portions as those described in the first embodiment are referred to by the same numerals, and a description thereof will be omitted.  
         [0096]      FIG. 9  is a block diagram showing the schematic configuration of capacitor devices  13  connected in series. The capacitor devices  13  shown in  FIG. 9  are configured such that a single capacitor charging unit  59  is used to charge a single capacitor bank  36 , and such that the two capacitor banks  36  are connected in series at the time of discharge, thereby providing twice as high voltage as the charging voltage. The two heaters HT 1  and HT 2  are connected in parallel to the two capacitor banks  36  that are connected in series. A separate discharge relay  57  and discharge FET  58  make it possible to perform separate, independent discharge operations.  
         [0097]     According to the third embodiment, the capacitor device  13  is provided as an independent module, which makes it possible to change the amount of power supply of the auxiliary power supply by selectively attaching or detaching such a module. This makes it possible to reduce the price of the apparatus and also to adjust the performance by adjusting the amount of electric power of the auxiliary power supply according to the user usage of apparatus, the user usage of power supply, user needs, etc.  
         [0098]     Further, the present invention is not limited to these embodiments, but various variations and modifications may be made without departing from the scope of the present invention.  
         [0099]     The present application is based on Japanese priority application No. 2004-225619 filed on Aug. 2, 2004 and Japanese priority application No. 2005-202153 filed on Jul. 11, 2005, with the Japanese Patent Office, the entire contents of which are hereby incorporated by reference.