Abstract:
An image forming apparatus including: a main body; a cover rotatably connected to the main body; a power-supply unit to generate a first power-supply voltage and a second power-supply voltage; an image forming engine to receive the first power-supply voltage from the power-supply unit; a control unit to receive the second power-supply voltage from the power-supply unit, and to stop an operation of the image forming engine, when the second power-supply voltage is cutoff. The image forming apparatus further includes a power-supply cutoff unit that delays a cutoff time of the first power-supply voltage, as compared to a cutoff time of the second power-supply voltage, according to an opening of the cover. The cutoff unit includes a first switch to cutoff first power-supply voltage to the image forming engine, and a second switch to cutoff the second power-supply voltage to control unit.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application claims the benefit of Korean Application No. 2007-16017, filed on Feb. 15, 2007, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   Aspects of the present invention relate to an image forming apparatus, and more particularly, to an image forming apparatus to reduce accidents caused when a cover of the apparatus is opened. 
   2. Description of the Related Art 
   Generally, an image forming apparatus, for example, electrophotographic-type image forming apparatus, uses an electrophotographic printing scheme. The apparatus projects a laser beam onto a photoconductive drum, to form an electrostatic latent image, and converts the electrostatic latent image into a visible image, using a developer mounted to a developing apparatus. The visible image is transferred onto paper, and then fixed to the paper with heat and pressure. There are a variety of electrophotographic image forming apparatuses, for example, a laser beam printer (LBP), a duplicating machine, a facsimile, a multi-functional device, etc. 
   The image forming apparatus includes a power-supply unit to convert an AC power into a DC power, according to voltages of individual loads of an image forming engine. The image forming engine basically requires a low-voltage, power-supply voltage of about 24V, and a high-voltage, power-supply voltage of about 100 Kv. The power-supply unit provides a power-supply voltage of 5V to a control unit that controls the image forming operations. 
   If an after-sale (A/S) repairman or a user opens a cover rotatably connected to the front or lateral side of a main body of the apparatus, to inspect or maintain the image forming apparatus, the repairman or user may be in danger from a high voltage inside of the main body. For this purpose, the image forming apparatus includes a first switch and a second switch. If the cover is open, the first switch blocks the power-supply voltage of 5V from being applied from the power-supply unit to the control unit, and the second switch blocks the power-supply voltage of 24V from being applied from the power-supply unit to the image forming engine. 
   The first and second switches are simultaneously switched off, when the cover of the image forming apparatus is open, so that the power-supply voltages, applied to the control unit and the image forming engine, are blocked. As a result, the repairman or user can be protected from an electric shock. 
   However, while the cover is open, if the first and second switches are simultaneously switched off, and the power-supply voltages applied to the control unit and the image forming engine are simultaneously turned off, the image forming engine suddenly stops operation. This can result in the image forming apparatus being unstably powered off. For example, in the case of a developing process, if a high voltage for controlling a toner is not applied to the developing process of the image forming apparatus, the developing process stops operation. In this case, a developing roller of the developer does not immediately stop operation, but instead, continuously rotates by inertia, for a relatively long period of time. A carrier for carrying the toner and the toner are not controlled by the high voltage, so that the carrier and toner may leak out. The leaked carrier and toner pollutes inner parts of the image forming apparatus, such that the printing performance and the image quality may be seriously degraded. In addition, the fine structure of the surface of the photoconductive drum can be damaged, resulting in degraded printing performance, and a reduced lifetime of the apparatus. In addition, if the image forming apparatus suddenly stops operation, gears may be engage with each other, complicating the disassembly thereof. If the image forming apparatus suddenly stops operation, when paper is inserted under the roller, the paper may become jammed. 
   A representative image forming apparatus capable of solving the above-mentioned problems has been disclosed in Japanese Patent Laid-open No. 2006-030702, which is hereby incorporated by reference. The image forming apparatus disclosed in Japanese Patent Laid-open No. 2006-030702 includes a relay circuit as a delay circuit. The relay circuit allows a power-supply voltage, applied to an image forming engine, to be continuously applied to the image forming engine during a predetermined period of time, even though the cover is open. Therefore, the image forming apparatus allows the image forming engine to normally stop operation, and prevents the power-supply voltage from being applied to the image forming engine. 
   However, the above-mentioned conventional art disclosed in Japanese Patent Laid-open No. 2006-030702 requires the additional relay circuit, resulting in increased production costs circuit complexity. 
   SUMMARY OF THE INVENTION 
   Aspects of the invention to provide an image forming apparatus to delay a cutoff time of a power-supply voltage, applied to an image forming engine, when a cover is opened, without using a delay circuit, such as a relay circuit. This configuration results in lower production costs and simplified circuitry. 
   Aspects of the present invention relate to an image forming apparatus including: a main body; a cover rotatably connected to the main body; a power-supply unit to generate a first power-supply voltage and a second power-supply voltage; an image forming engine to receive the first power-supply voltage from the power-supply unit; a control unit to receive the second power-supply voltage from the power-supply unit, and to stop operation of the image forming engine when the second power-supply voltage is cutoff; and a power-supply cutoff unit to delay a cutoff time of the first power-supply voltage, as compared to a cutoff time of the second power-supply voltage, when the cover is opened. 
   In accordance with another aspect of the present invention, there is provided an image forming apparatus including: a main body; a cover rotatably connected to the main body; an image forming engine; a control unit to power off the image forming engine, if a power-supply voltage is cutoff; a power-supply unit to power on the image forming engine and the control unit; a first switching unit to power off the control unit, if the cover is partially opened; and a second switching unit to power off the image forming engine, if the cover is fully opened. 
   Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings, of which: 
       FIG. 1  is a conceptual diagram illustrating an image forming apparatus according to an exemplary embodiment of the present invention; 
       FIG. 2  is a block diagram illustrating an image forming apparatus, according to the exemplary embodiment of the present invention; 
       FIG. 3  shows the appearance of the image forming apparatus with a closed cover, according to aspects of the present invention; 
       FIG. 4  shows the appearance of the image forming apparatus with a partially-opened cover, according to aspects of the present invention; and 
       FIG. 5  shows the appearance of the image forming apparatus with a fully-opened cover, according to aspects of the present invention. 
   

   DETAILED DESCRIPTION OF THE EMBODIMENTS 
   Reference will now be made in detail to the exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. The exemplary embodiments are described below to explain the present invention, by referring to the figures. 
     FIG. 1  is a conceptual diagram illustrating an image forming apparatus  100 , according to an exemplary embodiment of the present invention. Referring to  FIG. 1 , the image forming apparatus  100  includes an electric charger  2 , a laser scanning unit (LSU)  3  acting as an exposure unit, a developer  4 , a copy unit  7 , and fusers  9  and  10 . The surface of the photoconductive drum  1  is charged with electricity by the electric charger  2 , and then the LSU  3  forms an electrostatic latent image on the photoconductive drum  1 . The developer  4  develops the electrostatic latent image with toner, to form a visible image  8 . The visible image  8  is transferred to a recording medium by the copy unit  7 . The visible image  8  is fixed to the recording medium, by the fusers  9  and  10 , and is then carried out to the outside. 
   The image forming apparatus  100  can include a provider  6 , and a regulation blade  5 . A high voltage is applied to the photoconductive drum  1 , the electric charger  2 , the developer  4 , and the copy unit  7 , by a high voltage power supply (HVPS)  42 , as shown in  FIG. 2 . The HVPS  42  generates the high voltage from a power-supply voltage (e.g., 24V) produced by a switching mode power supply (SMPS), and transmits the high voltage to the photoconductive drum  1 , the electric charger  2 , the developer  4 , and the copy unit  7 . 
     FIG. 2  is a block diagram illustrating the image forming apparatus  100 . Referring to  FIG. 2 , the image forming apparatus  100  includes a power-supply unit  10 , a power-supply cutoff unit  20 , a control unit  30 , and an image forming engine  40 . The power-supply unit  10  is connected to an AC power source, converts the AC power into different power-supply voltages (e.g., 24V and 5V), and transmits the power-supply voltages of 24V and 5V to the control unit  30  and the image forming engine  40 , respectively. 
   The image forming engine  40  includes a plurality of power-consumption loads, for example, a motor  41 , the LSU  3 , the HVPS  42 , the photoconductive drum  1 , an electric charger  2 , the developer  4 , the copy unit  7 , etc. The motor  41 , the LSU  3 , and the HVPS  42  receive the power-supply voltage of 24V, from the power-supply unit  10 . The photoconductive drum  1 , the charger  2 , the developer  4 , and the copy unit  7  receive the high voltage generated by the HVPS  42 . The motor  41  may be any one of a driving motor of the photoconductive drum, a toner alternating motor, and a fuser roller driving motor. 
   The control unit  30  receives the power-supply voltage of 5V from the power-supply unit  10 . The control unit  30  can be powered by a different power-supply voltage (not shown). The control unit  30  includes a user interface  32  and a controller  31 . The controller  31  is connected to the user interface  32 , to allow a user to enter desired printing commands to form the image, and informs the user of the image forming information. The controller  31  can be connected to an external host computer (not shown), over a network, so that it receives image data from the host computer. Upon receiving the image data, the controller  31  analyzes the printing commands and the image data, and converts the analyzed data into a suitable format for use by the image forming engine  40 . 
   The controller  31  controls the image forming engine  40  on the basis of the converted printing data, thereby controlling the image forming operation. Particularly, the controller  31  is connected to one side of a second switching unit  21 , included in the power-supply cutoff unit  20 , which is switched off when the cover is being opened. The controller  31  determines whether a cover (not shown) of the image forming apparatus  100  is open or closed, according to the ON or OFF status of the second switching unit  21 . If the cover is being opened, the controller  31  performs control operations, to halt operations of the image forming engine  40 . 
   The power-supply cutoff unit  20  includes a first switching unit  22  and the second switching unit  21 . The first switching unit  22  is connected to a power-supply line extending between the power-supply unit  10  and the image forming engine  40 . The first switching unit  22  blocks the power-supply voltage of 24V from being applied to the image forming engine  40 . The second switching unit  21  is connected to a power-supply line extending between the power-supply unit  10  and the control unit  30 . The second switching unit  21  blocks the power-supply voltage of 5V from being applied to the control unit  30 . 
   Referring to  FIGS. 3 to 5 , the image forming apparatus  100  includes a main body  50  and a cover  60  rotatably connected to the main body  50 . The first switching unit  22  and the second switching unit  21  are designed to be switched on or off when brought into contact with the cover  60 . In more detail, the first switching unit  22  and the second switching unit  21  are switched off when the cover  60  is open. When the cover  60  is being opened, the second switching unit  21  is switched off before the first switching unit  22  is switched off. 
   The first switching unit  22  is mounted to the main body  50 , adjacent to a hinged end  63  of the cover  60 . The second switching unit  21  is mounted to the main body  50 , adjacent to a free end  65  of the cover  60 . Therefore, if the cover  60  is partially open, only the second switching unit  21  is switched off. If the cover  60  is fully open, or open an amount that is greater than the partial amount that switches off the switching unit  21 , the first and second switching units  22  and  21  are both switched off. 
   A first projection  62  and a second projection  61  extend from the cover  60 . The first projection  62  contacts the first switching unit  22 , when the cover  60  is closed, and disposed adjacent to the hinged end  63  of the cover  60 . The second projection  61  contacts the second switching unit  21 , when the cover  60  is closed, and is disposed adjacent to the free end  65  of the cover  60 . Therefore, the first switching unit  22  is switched on or off by the first projection  62 , and the second switching unit  21  is switched on or off by the second projection  61 . In other words, if a contact point of the first switching unit  22  is physically brought into contact with the first projection  62 , the first switching unit  22  is switched on. If the first projection  62  is released from the contact point, the first switching unit  22  is switched off. If the contact point of the second switching unit  21  is physically brought into contact with the second projection  61 , the second switching unit  21  is switched on. If the second projection  62  is released from the contact point, the second switching unit  21  is switched off. 
   Therefore, the first and second switching units  22  and  21  are both switched off when the cover  60  is completely opened. While the cover  60  is being opened, the second switching unit  21  is switched off first. After a lapse of a predetermined time, the second switching unit  21  is switched off. As a result, the image forming apparatus  100  does not require a delay circuit, such as a relay circuit, used in the conventional art, and sequentially switches off the first and second switching units  22  and  21 . In this way, production costs are reduced and the circuit is simplified. 
   In the operation of the first and second switching units  22  and  21 , if the cover  60  is closed, as shown in  FIG. 3 , the first and second switching units  22  and  21  are both switched on. The power-supply unit  10  transmits the power-supply voltage of 5V to the control unit  30 , via the second switching unit  21 . At the same time, the power-supply voltage of 24V is generated by the power-supply unit  10 , and is applied to the image forming engine  40 , via the first switching unit  22 . 
   As shown in  FIG. 4 , if an A/S repairman or a user partially opens the cover  60 , the second switching unit  21  is switched off, while the first switching unit  22  remains on. Therefore, the second switching unit  21  blocks the power-supply voltage of 5V from being applied to the control unit  30 . In this case, the controller  31  of the control unit  30  detects the above-mentioned situation, determines that the cover  60  is open, and controls the image forming engine  40  to perform a shut down operation, to avoid a sudden stoppage of the image forming engine  40 . 
   As shown in  FIG. 5 , if the cover  60  is fully opened, the first switching unit  22  and the second switching unit  21  are both switched off, and the power-supply voltage of 24V is not applied to the image forming engine  40 . Therefore, the image forming apparatus  100  prevents the occurrence of electric shocks, due to contact with the voltages of the inner components of the apparatus  100 . 
   In other words, if the cover  60  is completely open, the image forming apparatus  100  is rendered interoperable, without using an additional delay circuit, and the first switching unit  22  and the second switching unit  21  are sequentially switched off. As a result, after the image forming engine  40  stably stops operation, the power-supply voltage of 24V, applied to the image forming engine  40 , is cutoff. Therefore, the image forming apparatus  100  prevents the toner and the carrier from being leaked, due to an improper shutdown of image forming engine  40 . The image forming apparatus  100  prevents a reduction of image quality, and reduces the degree of pollution inside of the main body  50 . The image forming apparatus  100  does not stop operation with a printing medium inserted under the roller, so that the printing medium will not become jammed. 
   In brief, if the cover  60  of the main body  50  is opened during the image forming operation, the first and second switching units  22  and  21  are sequentially switched off, according to an interaction with the cover  60 . As soon as the cover  50  is partially opened, the second switching unit  21  is switched off, so that the power-supply voltage of 5V is not applied to the control unit  30 . The controller  31  detects the partial opening of the cover  60 , and outputs a command to the image forming engine  40 , to trigger a shutdown operation of the image forming engine  40 . If the cover  60  is fully open, the first switching unit  22  is switched off, and the power-supply voltage of 24V is cutoff from the image forming engine  40 . A delay between the switch off of second switching unit  21 , and the switch off of the first switching unit  22 , the image forming engine  40  stably stops operation, so that the image forming apparatus prevents the image forming engine  40  from being suddenly halted. The image forming engine  40  can stably stop operation by performing a shutdown operation. The shutdown operation prepares the image forming engine  40  for shutdown, and thereby prevents toner loss and/or damage to the image forming engine  40 . 
   The method for preventing the power-supply voltage from being applied to the image forming engine  40 , after the cover  60  is opened, will hereinafter be described in detail. If the cover  60  is partially opened, the contact between the second switching unit  21  and the second projection  61 , mounted to the upper part of the cover  60 , is broken, thereby switching off second switching unit  21 . If the second switching unit  21  is switched off, the power-supply voltage of 5V is not applied to the control unit  30 . 
   If the power-supply voltage of 5V is not applied to the control unit  30 , the controller  31  detects that the cover  60  is partially opened, and generates a control command to stop the image forming engine  40 . In this case, the first switching unit  22  continuously maintains the ON status, because the contact point is pressed by the first projection  62 . 
   If the cover  60  is fully opened, or opened an amount that is greater than the partial amount that switches off the switching unit  21 , the contact between the first switching unit  22  and the first projection  62  is broken, so that the first switching unit  22  is switched off. If the first switching unit  22  is switched off, the power-supply voltage of 24V is not applied to the load. 
   A predetermined time of about 200 msec elapses before the cover  60  is fully opened. The image forming engine  40  continues to be powered during the 200 msec. During this time, the image forming engine  40  can initiate the shutdown operation, such that it is properly shutdown. As a result, the image forming apparatus prevents the image forming engine  40  from being suddenly powered off, without using an additional delay circuit, such as a relay circuit. Therefore, the problems, caused by the abnormal power-supply cutoff of the image forming engine  40 , can be prevented. 
   As is apparent from the above description, an image forming apparatus, according to aspects of the present invention, includes a first switch to power off an image forming engine, and a second switch to power off a control unit. The first and second switches are sequentially switched off, by the opening of a cover. The first and second switches are arranged to allow the power-supply voltage, applied to the image forming engine, to be cutoff after the power-supply voltage is cutoff from the control unit. If the power-supply voltage applied to the control unit is cutoff, the image forming engine stops operation, so that the image forming apparatus can delay a cutoff time of the power-supply voltage applied to the image forming engine, when the cover is opened, without using a delay circuit such as the relay circuit, so that the production costs are reduced and the circuit is simplified. 
   Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.