# US 7,412,195 B2 · Image forming apparatus having means to prevent image quality degradation > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,412,195 B2 - Document ID: US7412195B2 - Status: Granted - Kind: B2 - Application number: 11/272,480 - Filed: 2005-11-14 - Published: 2006-07-06 - Granted: 2008-08-12 - Earliest claimed: 2004-11-13 - Assignees: Samsung Electronics Co., Ltd. - Inventors: Moon-bae Park; Myung-ho Kyung - Web page: https://patentgrep.com/patent/US7412195B2 ## CPC - G03G 15/0233: {Structure, details of the charging member, e.g. chemical composition, surface properties} - G03G: ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY ## Abstract An image forming apparatus includes a transfer belt onto which a toner image formed on an outer surface of a photosensitive medium is transferred. The transfer belt moves along a predetermined closed path while being supported by a plurality of rollers. A protection unit protects the transfer belt by being attached to at least one of an inner surface and an outer surface of a non-transferring region of the transfer belt. A control unit controls the transfer belt so that an overlapping part where the protection unit is attached to the transfer belt, and a seam part where two ends of the transfer belt are connected stops at a predetermined location after printing. The image forming apparatus substantially prevents partial loss of an image by preventing wrinkles in the transfer belt. ## Claims ### Claim 1 An image forming apparatus, comprising: a transfer belt onto which a toner image formed on an outer surface of a photosensitive medium is transferred, the transfer belt traveling along a predetermined closed path while being supported by a plurality of rollers; a protection unit that protects the transfer belt by being attached to at least one of an inner surface and an outer surface of a non-transferring region of the transfer belt; and a control unit that controls the transfer belt so that an overlapping part where the protection unit is attached to the transfer belt and a seam part where two ends of the transfer belt are connected stop at a predetermined location after printing. ### Claim 2 (depends on 1) The image forming apparatus of claim 1, wherein the control unit controls the transfer belt so that the overlapping part and the seam part stop between the plurality of rollers. ### Claim 3 (depends on 2) The image forming apparatus of claim 2, wherein a sensor unit senses a stopping location of the transfer belt to stop at the predetermined location. ### Claim 4 (depends on 3) The image forming apparatus of claim 3, wherein the protection unit is installed parallel to a direction of the transfer belt near both edges of the transfer belt. ### Claim 5 (depends on 4) The image forming apparatus of claim 4, wherein the protection unit is attached to the transfer belt with a bonding tension force of less than 500 gf/mm. ### Claim 6 (depends on 1) The image forming apparatus of claim 1, wherein the plurality of rollers include an intermediate transfer roller that transfers a toner image onto the transfer belt; a supporting roller that supports the transfer belt; and a nip roller that maintains a predetermined nip between the photosensitive medium and the transfer belt. ### Claim 7 (depends on 6) The image forming apparatus of claim 6, wherein a guide unit is installed at the inner surface of the transfer belt facing the photosensitive medium to maintain the predetermined nip between the photosensitive medium and the transfer belt. ### Claim 8 (depends on 7) The image forming apparatus of claim 7, wherein the guide unit is mounted close to the predetermined nip. ### Claim 9 (depends on 8) The image forming apparatus of claim 8, wherein the guide unit has electrical conductivity. ### Claim 10 (depends on 9) The image forming apparatus of claim 9, wherein the guide unit has an electrical resistance of 0.1-3 MΩ and a hardness of 26-38°. ### Claim 11 (depends on 10) The image forming apparatus of claim 10, wherein the guide unit is mounted between the intermediate transfer roller and the nip roller. ### Claim 12 (depends on 6) The image forming apparatus of claim 6, wherein the transfer belt is made of polyimide. ### Claim 13 (depends on 12) The image forming apparatus of claim 12, wherein the transfer belt has a thickness of approximately 75 μm. ### Claim 14 (depends on 1) The image forming apparatus of claim 1, wherein a bias preventing guide unit that extends in the direction of motion of the transfer belt and is mounted on the protection unit attached to an inner surface of the transfer belt; and a guide pulley unit that has a guide groove that regulates the movement of the bias preventing guide unit in a width direction, and is mounted on an outer surface of at least one of the plurality of rollers. ### Claim 15 (depends on 14) The image forming apparatus of claim 14, wherein the bias preventing guide unit and the guide pulley unit are mounted at one side of the transfer belt. ### Claim 16 (depends on 15) The image forming apparatus of claim 15, wherein the transfer belt is regulated by the guide pulley unit to substantially prevent deviation from an outer surface of the guide pulley unit. ### Claim 17 (depends on 16) The image forming apparatus of claim 16, wherein the bias preventing guide unit has a thickness greater than 0.8 mm and less than 1.2 mm. ### Claim 18 (depends on 14) The image forming apparatus of claim 14, wherein the control unit controls the transfer belt so that the overlapping part and the seam part are located at a span between the plurality of rollers. ### Claim 19 (depends on 14) The image forming apparatus of claim 14, wherein an intermediate transfer roller transfers a toner image onto the transfer belt; a supporting roller supports the transfer belt; and a nip roller maintains a predetermined nip between the photosensitive medium and the transfer belt. ### Claim 20 (depends on 19) The image forming apparatus of claim 19, wherein a guide unit is installed at the inner surface of the transfer belt facing the photosensitive medium to maintain the predetermined nip between the photosensitive medium and the transfer belt. ### Claim 21 An image forming apparatus, comprising: a transfer belt onto which a toner image formed on an outer surface of a photosensitive medium is transferred, the transfer belt traveling along a predetermined closed path while being supported by a plurality of rollers; two rollers of the plurality of rollers disposed at an inner surface of the transfer belt so that a nip between the photosensitive medium and the transfer belt is maintained; and a guide unit disposed at the inner surface of the transfer belt facing the photosensitive medium to prevent vibration of the nip during a transfer operation, wherein a transferring bias voltage is applied to one of the two rollers to transfer the toner image from the photosensitive medium onto the transfer belt, and the guide unit is an electrical conductor that blocks an electric field between the photosensitive medium and the one roller to which the transferring bias voltage is applied, thereby facilitating the image transfer. ### Claim 22 (depends on 21) The image forming apparatus of claim 21, wherein the guide unit is mounted close to the nip. ### Claim 23 (depends on 21) The image forming apparatus of claim 21, wherein the guide unit is mounted between the two rollers.