# US 10,120,323 B2 · Image forming apparatus > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,120,323 B2 - Document ID: US10120323B2 - Status: Granted - Kind: B2 - Application number: 15/660,794 - Filed: 2017-07-26 - Published: 2018-02-01 - Granted: 2018-11-06 - Earliest claimed: 2016-07-29 - Assignees: Canon Kabushiki Kaisha - Applicants: Canon Kabushiki Kaisha - Inventors: Yusuke Shimizu; Kenichi Iida; Takao Kume; Keisuke Ishizumi; Toshihiko Takayama - Web page: https://patentgrep.com/patent/US10120323B2 ## CPC - G03G 15/80: {Details relating to power supplies, circuits boards, electrical connections} - G03G 15/1675: {with means for controlling the bias applied in the transfer nip} - G03G 15/5004: {Power supply control, e.g. power-saving mode, automatic power turn-off} - G03G 15/5008: {Driving control for rotary photosensitive medium, e.g. speed control, stop position control} - H04N 1/00254: {with an electrophotographic copying machine, i.e. a photocopier} - G03G 15/161: {with means for handling the intermediate support, e.g. heating, cleaning, coating with a transfer agent} - G03G 15/5054: {by measuring the characteristics of an intermediate image carrying member or the characteristics of an image on an intermediate image carrying member, e.g. intermediate transfer belt or drum, conveyor belt} - G03G 2215/0103: Plural electrographic recording members - G03G: ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION ## Abstract The present disclosure is directed to suppressing image defects due to variations in the values of currents flowing through respective photosensitive drums during image formation, and reducing the absolute value of a voltage applied when a primary transfer power supply unit applies a voltage of polarity opposite to that during image formation, to primary transfer members. There is provided an image forming apparatus including a transfer member configured to make contact with an inner peripheral surface of a transfer belt, a first power supply unit configured to apply a voltage to the transfer member, a resistance element connected between the first power supply unit and the transfer member, and a diode connected in parallel with the resistance element in a direction in which a current flowing in a first direction is blocked and a current flowing in a second direction is passed. ## Claims ### Claim 1 An image forming apparatus comprising: an image bearing member configured to bear a toner image; a transfer belt configured to rotate in contact with the image bearing member; a transfer member configured to make contact with an inner peripheral surface of the transfer belt, wherein the transfer member is provided to correspond to the image bearing member; a first power supply unit configured to apply a voltage to the transfer member, wherein if the first power supply unit applies a voltage of a second polarity opposite to a first polarity to the transfer member, a current flows in a first direction through a position in which the image bearing member makes contact with the transfer belt, and if the first power supply unit applies a voltage of the first polarity to the transfer member, a current flows in a second direction opposite to the first direction through the position in which the image bearing member makes contact with the transfer belt, the first polarity being a normal charging polarity of toner; a resistance element connected between the first power supply unit and the transfer member; and a diode connected in parallel with the resistance element in a direction in which the current flowing in the first direction is blocked and the current flowing in the second direction is passed. ### Claim 2 (depends on 1) The image forming apparatus according to claim 1, wherein the current flowing in the first direction flows via the resistance element. ### Claim 3 (depends on 1) The image forming apparatus according to claim 1, further comprising: a plurality of image bearing members; and a plurality of transfer members provided to correspond to the plurality of image bearing members, wherein the resistance element has a resistance value greater than variations in electrical resistance of the plurality of transfer members. ### Claim 4 (depends on 1) The image forming apparatus according to claim 1, wherein the transfer member is brush-like conductive fibers. ### Claim 5 (depends on 1) The image forming apparatus according to claim 1, wherein the transfer member is a metal roller, and wherein the metal roller is arranged downstream, in a moving direction of the transfer belt, of the position in which the image bearing member makes contact with the transfer belt. ### Claim 6 (depends on 1) The image forming apparatus according to claim 1, further comprising: a secondary transfer member configured to make contact with an outer peripheral surface of the transfer belt to form a secondary transfer portion; a contact member configured to make contact with the transfer belt downstream of the secondary transfer portion and upstream of the image bearing member in a moving direction of the transfer belt; and a second power supply unit configured to apply a voltage to the secondary transfer member and the contact member, wherein toner remaining on the transfer belt after a toner image is transferred from the transfer belt to a transfer material in the secondary transfer portion is charged while passing through a position in which the contact member and the transfer belt make contact, the contact member being subjected to application of a voltage of the second polarity from the second power supply unit, and moves from the transfer belt to the image bearing member in the position in which the image bearing member makes contact with the transfer belt. ### Claim 7 (depends on 6) The image forming apparatus according to claim 6, wherein the contact member is brush-like conductive fibers. ### Claim 8 (depends on 7) The image forming apparatus according to claim 7, wherein if the second power supply unit applies a voltage of the first polarity to the contact member, toner adhering to the contact member when the voltage of the second polarity is applied to the contact member moves from the contact member to the transfer belt, and wherein if the first power supply unit applies the voltage of the first polarity to the transfer member, the toner moved from the contact member to the transfer belt moves from the transfer belt to the image bearing member in the position in which the image bearing member makes contact with the transfer belt. ### Claim 9 (depends on 1) The image forming apparatus according to claim 1, wherein the transfer belt has ion conductivity. ### Claim 10 An image forming apparatus comprising: an image bearing member configured to bear a toner image; an intermediate transfer belt configured to rotate in contact with the image bearing member, wherein a toner image is primarily transferred from the image bearing member to the intermediate transfer belt in a primary transfer portion in which the image bearing member makes contact with the intermediate transfer belt; a primary transfer member configured to make contact with an inner peripheral surface of the intermediate transfer belt, wherein the primary transfer member is provided to correspond to the image bearing member; a secondary transfer member configured to make contact with an outer peripheral surface of the intermediate transfer belt to form a secondary transfer portion, and secondarily transfer the toner image from the intermediate transfer belt to a transfer material; a counter member opposed to the secondary transfer member via the intermediate transfer belt, wherein the counter member and the primary transfer member are electrically connected; a power supply unit configured to apply a voltage to the secondary transfer member, wherein if the power supply unit applies a voltage of a second polarity opposite to a first polarity to the secondary transfer member, a current flows through a primary transfer portion via the counter member and the primary transfer member in a first direction, and if the power supply unit applies a voltage of the first polarity to the secondary transfer member, a current flows through the primary transfer portion via the counter member and the primary transfer member in a second direction opposite to the first direction, the first polarity being a normal charging polarity of toner; a resistance element connected between the power supply unit and the primary transfer member; and a first diode connected in parallel with the resistance element in a direction in which the current flowing in the first direction is blocked and the current flowing in the second direction is passed. ### Claim 11 (depends on 10) The image forming apparatus according to claim 10, further comprising: a constant voltage element connected to the counter member and configured to be maintained at a predetermined voltage when a current flows therethrough; and a second diode configured to be capable of passing a current from its anode to cathode, wherein a cathode side of the constant voltage element is connected to the counter member and the primary transfer member, an anode side of the constant voltage element is connected to an anode side of the second diode, and a cathode side of the second diode is electrically grounded; and wherein if the power supply unit applies the voltage of the second polarity to the secondary transfer member, a current flows through the constant voltage element via the counter member. ### Claim 12 (depends on 10) The image forming apparatus according to claim 10, wherein the toner image is, by the current flowing in the first direction, primarily transferred from the image bearing member to the intermediate transfer belt in the primary transfer portion and secondarily transferred from the intermediate transfer belt to a transfer belt in a secondary transfer portion. ### Claim 13 (depends on 10) The image forming apparatus according to claim 10, wherein the current flowing in the first direction flows via the resistance element. ### Claim 14 (depends on 10) The image forming apparatus according to claim 10, further comprising: a plurality of image bearing members; and a plurality of primary transfer members provided to correspond to the plurality of image bearing members, wherein the resistance element has a resistance value greater than variations in electrical resistance of the plurality of primary transfer members. ### Claim 15 (depends on 10) The image forming apparatus according to claim 10, wherein the primary transfer member is brush-like conductive fibers. ### Claim 16 (depends on 10) The image forming apparatus according to claim 10, wherein the primary transfer member is a metal roller, and wherein the metal roller is arranged downstream of the primary transfer portion in a moving direction of the intermediate transfer belt. ### Claim 17 (depends on 10) The image forming apparatus according to claim 10, further comprising a contact member configured to make contact with the intermediate transfer belt downstream of the secondary transfer portion and upstream of the image bearing member in a moving direction of the intermediate transfer belt, wherein a voltage is applied to the contact member from the power supply unit, and wherein toner remaining on the intermediate transfer belt after the toner image is secondarily transferred from the intermediate transfer belt to the transfer material in the secondary transfer portion is charged while passing through a position in which the contact member and the intermediate transfer belt make contact, the contact member being subjected to application of a voltage of the second polarity from the power supply unit, and moves from the intermediate transfer belt to the image bearing member in the primary transfer portion. ### Claim 18 (depends on 17) The image forming apparatus according to claim 17, wherein the contact member is brush-like conductive fibers. ### Claim 19 (depends on 18) The image forming apparatus according to claim 18, wherein if the power supply unit applies the voltage of the first polarity to the contact member, toner adhering to the contact member when the voltage of the second polarity is applied to the contact member moves from the contact member to the intermediate transfer belt, and wherein if the power supply unit applies the voltage of the first polarity to the secondary transfer member, the toner moved from the contact member to the intermediate transfer belt moves from the intermediate transfer belt to the image bearing member in the primary transfer portion. ### Claim 20 (depends on 10) The image forming apparatus according to claim 10, wherein the intermediate transfer belt has ion conductivity. ### Claim 21 (depends on 1) The image forming apparatus according to claim 1, wherein in a state in which the first power supply unit applies a voltage of the second polarity to the transfer member, the toner image is transferred from the image bearing member to the transfer belt by the current flowing in the first direction through the position in which the image bearing member makes contact with the transfer belt.