Patent Publication Number: US-7725058-B2

Title: Developing unit and image forming apparatus having the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims priority under 35 U.S.C. §119 (a) of Korean Patent Application Nos. 10-2007-0093892, filed on Sep. 14, 2007, and 10-2008-0025617, filed on Mar. 19, 2008, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present general inventive concept relates to an image forming apparatus utilizing an electrophotographic process, and more particularly, to a developing unit capable of evenly spreading pressure of a developer and preventing the developer from being scattered, and an image forming apparatus having the developing unit. 
   2. Description of the Related Art 
   Image forming apparatuses utilizing electrophotographic processes perform operations such as charging, exposing, developing, transferring and fixing in order to form images. Developing units within the image forming apparatus function to develop electrostatic latent images formed on photosensitive media using a developer. Developing units include developer housings containing developer, and developing rollers. The developer contained in the developer housings is attached to developing rollers, and a developing gap of a predetermined distance is formed between the developing rollers and photosensitive media. Electrostatic forces generated by a potential difference between the developing rollers and photosensitive media cause the developer attached to developing rollers to move to photosensitive media through the developing gap, so that visual images corresponding to the electrostatic latent images are formed. 
   There are two types of developing units, one of which is manufactured with developer pre-supplied to developer housings, and the other one of which does not have the developer pre-supplied. 
   In the case of a developing unit in which developer is not pre-supplied to developer housings, it is impossible to check whether the developing unit is of inferior quality after the developing unit has been manufactured, since there is no developer in the developing unit with which to perform a print test. 
   In the case of a developing unit in which developer is pre-supplied, it is possible to sort out defective products by performing a print test. However, problems may arise during distribution before the developing units reach customers. 
   Developer as powders have an adhesive quality, and thus if a developing unit is placed in an upright position for a long period of time or is transported a long distance, the developer particles may become coagulated on one side of the developing unit. Accordingly, the pressure of the developer particles may increase, and the torque required to transfer the developer particles may increase excessively due to the coagulated developer particles. Therefore, the load on a motor may become excessive, causing the motor to be unable to rotate, and making it impossible for printing to be performed. 
   A developing roller rotates while a developing unit is being operated, causing airflow to be generated in a developing gap between the developing roller and a photosensitive medium, and accordingly, some developer scatters outwards from the developing unit in the direction of the airflow rather than moving onto the photosensitive medium. Additionally, a portion of the airflow formed in the developing gap flows into a developer housing, so the air pressure inside the developer housing becomes greater than the air pressure outside the developer housing. Such a difference in air pressure may cause a greater amount of developer to be scattered, and an image forming apparatus and printing media may thus be contaminated due to the scattered developer. 
   In order to prevent the scattering of developer, it is necessary for the air pressure in the developer housing to be reduced. To achieve this, there is provided a conventional developer housing including a filter and an air vent hole formed therein. The filter only allows air to pass through while preventing the developer from passing through. However, fine developer particles having a diameter less than that of pores formed on the filter are able to flow out through the air vent hole. If a developing unit is attached to an image forming apparatus, there is a small possibility that fine developer particles flow out. However, since shocks or vibrations may be applied to the developing unit during distribution before the developing units reach customers, the outflow of fine developer particles may increase. 
   SUMMARY OF THE INVENTION 
   The present general inventive concept provides a developing unit which has an improved structure to evenly spread a pressure of developer stored in the developing unit and to prevent the developer from being scattered. 
   The present general inventive concept also provides an image forming apparatus having the developing unit in which it is possible to perform printing smoothly. 
   Additional aspects and utilities of the present general inventive concept 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 general inventive concept. 
   The foregoing and/or other aspects and utilities of the present general inventive concept may be achieved by providing a developing unit including: a developer housing to contain a developer; and a blocking member to divide the developer housing into a first section and a second section, which includes a developing member disposed therein to transfer the developer onto a photosensitive medium and stores the developer, the blocking member being detachably mounted in the developing unit. 
   When the blocking member is detached from the developing unit, the first section may be connected to the second section, so that a pressure of the developer inside the developer housing may be spread evenly. 
   The blocking member may be formed of a film. 
   The first section may extend lengthwise along the developing unit. There may be two or more first sections disposed at different positions. 
   A developer transfer device may be disposed in the second section. The developer transfer device may include an auger. 
   An air vent may be formed in the first section. 
   A filter member may be disposed in the first section to prevent the developer from flowing out via the air vent. 
   The developing unit may further include a developing member to develop the electrostatic latent image formed on the photosensitive medium using the developer, and a scatter preventing member to cause airflow to be generated in a direction opposite the direction of airflow formed between the photosensitive medium and the developing member. 
   The foregoing and/or other aspects and utilities of the present general inventive concept may also be achieved by providing a developing unit including a developer housing including a first section and a second section, and a blocking member removably disposed between the first section and second section, such that when the blocking member is removed from the developing unit, developer stored in one of the first section and the second section is free to move to the other one of the first section or second section to reduce the pressure of the developer within the one of the first section or the second section. 
   An air vent may be formed in one of the first section and the second section. A filter member may be disposed in one of the first section or second section to prevent the developer from flowing out via the air vent. 
   The foregoing and/or other aspects and utilities of the present general inventive concept may also be achieved by providing a developing unit including a developer housing to contain a developer; an air vent formed on the developer housing; a filter member to prevent the developer from flowing out via the air vent; and a blocking member to divide the developer housing and the air vent, the blocking member being detachably mounted in the developing unit. 
   The foregoing and/or other aspects and utilities of the present general inventive concept may also be achieved by providing an image forming apparatus including a photosensitive medium on which an electrostatic latent image is formed; a developing unit, as described above, to develop the electrostatic latent image using a developer; a transferring unit to transfer a developer image on the photosensitive medium developed by the developing unit onto a recording medium; and a fixing unit to fix the transferred developer image onto the recording medium. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and/or other aspects and utilities of the present general inventive concept 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 perspective view illustrating a developing unit according to an exemplary embodiment of the present general inventive concept; 
       FIG. 2  is a fragmentary perspective view illustrating the developing unit of  FIG. 1 ; 
       FIG. 3  is a cross-sectional view illustrating the developing unit of  FIG. 1 ; 
       FIG. 4  is a schematic view illustrating the state of developer contained in the developing unit of  FIG. 1  when the developing unit of  FIG. 1  is placed in an upright position; 
       FIG. 5  is a perspective view illustrating the developing unit of  FIG. 1  wherein there are no blocking members; and 
       FIG. 6  is a cross-sectional view illustrating an image forming apparatus having a developing unit according to an exemplary embodiment of the present general inventive concept. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Reference will now be made in detail to the embodiments of the present general inventive concept, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present general inventive concept by referring to the figures. 
     FIG. 1  is a perspective view illustrating a developing unit  100  according to an exemplary embodiment of the present general inventive concept,  FIG. 2  is a fragmentary perspective view illustrating the developing unit  100 , and  FIG. 3  is a cross-sectional view illustrating the developing unit  100 . 
   In this exemplary embodiment, the developing unit  100  includes a photosensitive medium  101 , a developing member  111 , a scatter preventing member  112 , a developer housing  120  and blocking members  130 . The developing unit  100  according to the above exemplary embodiment employs a tandem method for convenience of description, but this should not be considered limiting. 
   An electrostatic latent image may be formed on the photosensitive medium  101  by light emitted from a laser scanning unit (not illustrated). The developing unit  100  in the above exemplary embodiment includes the photosensitive medium  101  and employs the tandem method in which a plurality of developing units are arranged for each color to form color images, but the developing unit  100  is not limited to such a configuration. Accordingly, the present general inventive concept is equally applicable to a multi-method in which a plurality of developing units  100  form images on a single photosensitive medium. In this situation, the photosensitive medium is not disposed in each developing unit  100  and the number of photosensitive media is less than that of the developing units  100 . 
   The developing member  111  can coat the photosensitive medium  101 , on which the electrostatic latent image is formed, with the developer contained in the developer housing  120 . The developing member  111  may be formed as a roller, which is made of cylindrical rubber or metal, a belt or tubing. Additionally, if the developer exhibits magnetism, the developing unit  100  may include a kind of magnet. 
   Since the developing member  111  is not in contact with the photosensitive medium  101 , toner, as a form of developer, jumps from the developing member  111  to the photosensitive medium  101  so that developing can be performed. Alternatively, the present general inventive concept is equally applicable to a situation in which the developing member  111  is in contact with the photosensitive medium  101 . 
   The scatter preventing member  112  can cause airflow to be generated in a direction opposite to that of the airflow formed between the photosensitive medium  101  and the developing member  111 , and can prevent the developer from being scattered outwards from the developing unit  100 . The photosensitive medium  101  rotates in one direction, and the developing member  111  rotates in the opposite direction to the photosensitive medium  101 , so airflow may be generated in a developing gap between the photosensitive medium  101  and the developing member  111 . For example, if the photosensitive medium  101  rotates clockwise and the developing member  111  rotates counterclockwise, an upward airflow may be generated in the developing gap, as illustrated in  FIG. 3 . Accordingly, it may become impossible for a portion of the developer to move to the electrostatic latent image formed on the photosensitive medium  101 , and thus the developer may be scattered outwards from the developing unit  100  along the upward airflow in a direction indicated by an arrow  114  shown in  FIG. 3 . In this situation, if the scatter preventing member  112  rotates clockwise, another airflow may be generated in a direction opposite that of the upward airflow formed in the developing gap. Therefore, it is possible to prevent the developer from being scattered outwards from the developing unit  100 . 
   The developer housing  120  can be a space inside the developing unit  100  to store the developer. The developer housing  120  includes the developing member  111  and a developer transfer device  113 . A shutter  103  can control the supply of the developer to the developer housing  120  in a developer cartridge (not illustrated). The shutter  103  may be required only when the developer cartridge is separated from the developing unit  100 . The developer transfer device  113  can agitate the developer in the developer housing  120  and transfer the developer to the developing member  111  using the power transferred from a motor (not illustrated). In this exemplary embodiment, the developer transfer device  113  comprises an auger, but various types of developer transfer device  113  may be used. 
   The blocking member (or members)  130  can divide the developer housing  120  into a first section  121  and a second section  122 . The first section  121  may be empty space, and the second section  122  may include the developing member  111 . 
   If the developer has been previously supplied in the developer housing  120  when the developing unit  100  is initially manufactured, a print test can be performed when the developing unit  100  is completely manufactured. This test enables final verification of whether there are problems in the manufactured developing unit  100 , so it is possible to reduce the proportion of defective developing units  100 . 
   However, since the developer has an adhesive quality, developer particles may be coagulated during the circulation process. For example, if the developing unit  100  is placed in an upright position for a long period of time or is transported a long distance, the developer particles may lean to one side of the developer housing  120  and stick together. 
     FIG. 4  illustrates a state of developer  105  being coagulated in the developing unit  100  when the developing unit  100  is placed in an upright position. If the developer  105  is coagulated as illustrated in  FIG. 4 , the torque required to drive the developer transfer device  113  will most likely increase. Accordingly, the load on the motor, which supplies the driving force, may be excessive, causing power consumption to increase. More seriously, the motor may be unable to rotate, making it impossible for the developer transfer device  113  to transfer the developer contained in the developer housing  120 , so an image cannot be formed on a recording medium. 
   This is because the pressure of the developer inside the developer housing  120  reaches a high level. Specifically, the developer particles are coagulated at one side of the developer housing  120  rather than being evenly dispersed in the developer housing  120 , so the pressure of the developer increases. Additionally, when the developer particles are coagulated at one side of the developer housing  120 , there is no marginal space for the developer to move. Accordingly, a large resistance may be generated when the developer transfer device  113  is driven. 
   According to the exemplary embodiment, the blocking member  130  may be used to divide the developer housing  120  into the first section  121  and the second section  122 , and thus it is possible to solve the problems described above. The first section  121  may be disposed adjacent to the second section  122 , and may be empty. The blocking member  130  can separate the first section  121  and the second section  122 , and can be detached from developing unit  100  using a predetermined force. Here, the blocking members  130  can be formed of a film, or can desirably be formed of an elastic material. However, any member capable of separating the first section  121  and the second section  122  may be used as the blocking member  130 . 
   When the developing unit  100  is initially manufactured, only the second section  122  contains the developer and the first section  121  does not contain the developer, due to the blocking members  130 . A user may buy the developing unit  100 , attach the developing unit  100  to an image forming apparatus, and then remove the blocking members  130  in directions indicated by arrows illustrated in  FIG. 1  before using the developing unit  100 .  FIG. 5  illustrates the developing unit  100  in the case that there are no blocking members  130 . 
   If the blocking members  130  are removed, the first section  121  is connected to the second section  122 . Accordingly, a portion of the developer  105  coagulated at one side of the developing unit  100  can flow into the first section  121 , and thus the pressure of developer inside the developer housing  120  can be spread out more evenly. Additionally, this flow of the developer  105  creates some space in the second section  122  in which the coagulated developer  105  is contained, corresponding to the amount of developer flowing into the first section  121 . Therefore, the torque required to drive the developer transfer device  113  can be reduced. 
   The first section  121  of the developer housing  120  can desirably extend lengthwise along the developing unit  100 , as illustrated in  FIG. 1 . The coagulation of the developer usually arises when the developing unit  100  is placed in an upright position for a long period of time. Accordingly, if the developing unit  100  is laid down lengthwise in a horizontal position, there are no problems caused by coagulation of the developer. 
   The first section  121  of the developer housing  120  may be a single chamber traversing the developer housing  120 . In this situation, only one blocking member  130  is needed, as illustrated in the embodiment of  FIG. 2 . Accordingly, the user can remove only the one blocking member  130  before attaching the developing unit  100  to the image forming apparatus  100 , which increases convenience to the user. Alternatively, it is also possible for the first section  121  to have more than one chamber due to interference with other units or limitations of design. In this situation, two or more sections disposed at different positions may be used as the first section  121 . In this exemplary embodiment, there may be two first sections  121   a  and  121   b . One first section  121   a  may be disposed lengthwise along the developing unit  100 , and the other first section  121   b  may be disposed adjacent to the shutter  103 . If two or more first sections  121  are used, the number of blocking members  130  may also be two or more, corresponding to the number of first sections  121 . Thus, a plurality of blocking members  130  are required to be removed before the developing unit  100  is attached to the image forming apparatus. 
   An air vent  125  is formed on the developer housing  120 . Air is able to flow between the inside and outside of the developer housing  120  via the air vent  125 , so the air pressure inside the developer housing  120  may be reduced, and it is thus possible to prevent developer from being scattered. Accordingly, the scatter preventing member  112  and the air vent  125  described above in this exemplary embodiment can significantly reduce the scattering of the developer. 
   A filter member  126  can prevent the developer contained in the developer housing  120  from flowing out through the air vent  125 . Since air is able to pass through the filter member  126 , but developer is unable to pass through the filter member  126 , outflow of developer can be prevented and the air pressure inside the developer housing  120  can be reduced. Developer particles have different sizes. In other words, developer particles have a predetermined distribution in its size. Accordingly, fine developer particles having a diameter smaller than that of pores formed on the filter member  126  may flow out via the filter member  126 . If the developing unit  100  is attached to the image forming apparatus, there is a little possibility of such outflow of fine developer particles. However, shocks or vibrations may be applied to the developing unit  100  during distribution before the developing unit  100  reaches customers, so fine developer particles may flow out from the developing unit  100  through the filter member  126 . 
   According to this exemplary embodiment, the air vent  125  and the filter member  126  may be disposed in the first section  121 , which is separated by the blocking member  130  from the second section  122  in which the developer is stored. Accordingly, even when shocks or vibrations are applied to the developing unit  100  during distribution before the developing unit  100  reaches customers, the blocking member  130  can prevent fine developer particles from flowing out. As described above, the user may attach the developing unit  100  to the image forming apparatus, and then remove the blocking members  130  from the developing unit  100  before using the developing unit  100 . When the developing unit  100  is secured to the image forming apparatus, the outflow of fine developer particles becomes less important. If the blocking member  130  is removed, air is able to flow between the inside and outside of the developer housing  120  via the air vent  125 , and the air pressure inside the developer housing  120  may thus be reduced, so that it is possible to prevent the developer from being scattered. While the air vent  125  and filter member  126  are disposed in the first section  121  according to the exemplary embodiment, the air vent  125  and filter member  126  may be disposed in another extra space in the developer housing  120 . In this situation, another blocking member  130  may be mounted to separate the air vent  125  and the developer housing  120 . 
   Additionally, the developing unit  100  may further include a detecting device (not illustrated) to detect whether the blocking member  130  is removed from the developing unit  100 . If the user does not remove the blocking member  130  before using the developing unit  100 , the problems described above may occur. Accordingly, the detecting device (not illustrated) can detect whether the blocking member  130  is removed, and can cause the user to remove the blocking member  130  before using the developing unit  100 . For example, a detecting device may be a photo sensor to determine whether the blocking member  130  exists in the developing unit  100 . If the photo sensor determines that the blocking member  130  exists before the developing unit  100  is used, the photo sensor may notify the user that the blocking member  130  needs to be removed using a display window and an alarm sound. 
     FIG. 6  schematically illustrates an image forming apparatus  200  having the developing unit  100  according to an exemplary embodiment of the present general inventive concept. The image forming apparatus  200  includes a feeding unit  210 , a light scanning unit  220 , a developer cartridge  230 , a transferring unit  240 , a fixing unit  250  and the developing unit  100  configured as described above. 
   The feeding unit  210  can house a recording medium on which an image is to be formed, and feed the recording medium into the image forming apparatus  200 . The laser scanning unit  220  can form an electrostatic latent image on the photosensitive medium  101 . The developer cartridge  230  can store developer, and supply the developer to the developing unit  100 . The developing unit  100  can develop the photosensitive medium  101  on which the electrostatic latent image is formed, using the developer, and the transferring unit  240  can transfer the developer image developed by the developing unit  100  onto the recording medium. The fixing unit  250  can then fix the transferred developer image onto the recording medium, and the recording medium onto which the developer image is fixed may be subsequently discharged to the outside of the image forming apparatus  200 , completing the printing operation. 
   According to the exemplary embodiments described above, it is possible to evenly spread the pressure of the developer inside the developing unit, and thus the torque required to transfer the developer can be reduced. 
   Additionally, it is possible to perform printing smoothly even when developer particles become coagulated during the distribution of the developing unit. 
   Furthermore, it is possible to prevent the image forming apparatus from being contaminated due to the scattering of developer, and minimize the outflow of developer that occurs during distribution of the developing unit. 
   Although a few embodiments of the present general inventive concept have been illustrated and described, it will 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 general inventive concept, the scope of which is defined in the appended claims and their equivalents.