# US 2018/0024496 A1 · Image forming apparatus and method of controlling transfer power thereof > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2018/0024496 A1 - Document ID: US20180024496A1 - Status: Published application - Kind: A1 - Application number: 15/442,046 - Filed: 2017-02-24 - Published: 2018-01-25 - Earliest claimed: 2016-07-20 - Assignees: S-Printing Solution Co., Ltd. - Applicants: S-Printing Solution Co., Ltd. - Inventors: Sun-woo LEE; Jeong-ho CHOE - Web page: https://patentgrep.com/patent/US20180024496A1 ## CPC - G03G 21/203: {Humidity} - 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 15/1645: {Arrangements for controlling the amount of charge} - G03G 15/167: {at least one of the recording member or the transfer member being rotatable during the transfer} - G03G: ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY ## Abstract A method of controlling transfer power of an image forming apparatus includes: determining a sensing feedback voltage by applying a set sensing current and measuring a first output voltage during a time period before an image is transferred to a transfer medium; measuring humidity and comparing the measured humidity with a set value; setting a target voltage based on the determined sensing feedback voltage when the measured humidity is equal to or higher than the set value; and adjusting the transfer current to apply the target voltage during a time period in which the image is transferred to the transfer medium. ## Claims ### Claim 1 An image forming apparatus comprising: a humidity sensor to measure humidity; a transfer unit configured to transfer an image on a photoreceptor to a transfer medium by a first output voltage; a power supply to apply a transfer current with a corresponding voltage to the transfer unit; and a controller to control the transfer power supplied by the power supply to the transfer unit, wherein the controller determines a sensing feedback voltage by applying a set sensing current to the transfer unit and measuring the first output voltage of the transfer unit during a time period before the image is transferred to the transfer medium, sets a target voltage based on the determined sensing feedback voltage when the humidity measured by the humidity sensor is higher than a set value, and controls the power supply to adjust the transfer current to cause the corresponding voltage to reach the target voltage to the transfer unit during a time period in which the image is transferred to the transfer medium. ### Claim 2 (depends on 1) The image forming apparatus of claim 1, wherein, when the transfer current is adjusted to apply the target voltage to the transfer unit during the time period in which the image is transferred to the transfer medium, the controller increases the transfer current, which is applied by the power supply to the transfer unit, until the first output voltage reaches the target voltage and controls the transfer current, which is applied by the power supply to the transfer unit, to maintain the target voltage when the first output voltage reaches the target voltage. ### Claim 3 (depends on 1) The image forming apparatus of claim 1, wherein, when the humidity measured by the humidity sensor is lower than the set value or when the determined sensing feedback voltage is equal to higher than a set voltage, the controller sets a target current based on the determined sensing feedback voltage and controls the power supply to apply the transfer current corresponding to the target current to the transfer unit during the time period in which the image is transferred to the transfer medium. ### Claim 4 (depends on 3) The image forming apparatus of claim 3, wherein the controller: sets an effective transfer voltage based on the humidity measured by the humidity sensor; when a second output voltage of the transfer unit, which is measured by applying the transfer current to a terminal of the transfer medium, is lower than or equal to the effective transfer voltage after the transfer medium is inserted into the transfer unit during the time period in which the image is transferred to the transfer medium, increases the transfer current, which is applied by the power supply to the transfer unit, until the second output voltage reaches the effective transfer voltage; and controls the transfer current, which is applied by the power supply to the transfer unit, to maintain the effective transfer voltage when the second output voltage reaches the effective transfer voltage. ### Claim 5 (depends on 3) The image forming apparatus of claim 3, wherein the controller: sets an effective transfer voltage based on the humidity measured by the humidity sensor; when a second output voltage of the transfer unit, which is measured by applying the transfer current to a terminal of the transfer medium, is lower than or equal to the effective transfer voltage after the transfer medium is inserted into the transfer unit during the time period in which the image is transferred to the transfer medium, sets the target voltage based on the second output voltage; and controls the power supply to adjust the transfer current in order to apply the target voltage to the transfer unit during the time period in which the image is transferred to the transfer medium. ### Claim 6 (depends on 1) The image forming apparatus of claim 1, wherein the controller differently sets the target voltage according to types of the transfer medium. ### Claim 7 (depends on 1) The image forming apparatus of claim 1, wherein the time period before the image is transferred to the transfer medium is a time period before the transfer medium is inserted into the transfer unit. ### Claim 8 (depends on 1) The image forming apparatus of claim 1, wherein the controller determines that a lifetime of a transfer member reaches a lifetime limit when a third output voltage of the transfer unit, which is measured by applying the transfer current to a terminal of the transfer medium, is equal to or higher than a set threshold value after the transfer medium is inserted into the transfer unit during the time period in which the image is transferred to the transfer medium. ### Claim 9 A method of controlling transfer power of an image forming apparatus including a transfer unit to transfer an image on a photoreceptor to a transfer medium, the method comprising: measuring, by a humidify sensor, a humidity; and by a controller: determining a sensing feedback voltage by applying a set sensing current to the transfer unit and measuring a first output voltage of the transfer unit during a time period before an image is transferred to a transfer medium; comparing the measured humidity with a preset value; setting a target voltage based on the determined sensing feedback voltage when the measured humidity is equal to or higher than the set value; and adjusting a transfer current applied to the transfer unit to apply the target voltage during a time period in which the image is transferred to the transfer medium. ### Claim 10 (depends on 9) The method of claim 9, wherein the adjusting of the transfer current to apply the target voltage during the time period in which the image is transferred to the transfer medium comprises: increasing the transfer current until the first output voltage reaches the target voltage; and controlling the transfer current to maintain the target voltage when the first output voltage reaches the target voltage. ### Claim 11 (depends on 9) The method of claim 9, further comprising: setting a target current based on the determined sensing feedback voltage when the measured humidity is lower than the set value or when the determined sensing feedback voltage is equal to or higher than a set voltage; and applying the transfer current corresponding to the target current during the time period in which the image is transferred to the transfer medium. ### Claim 12 (depends on 11) The method of claim 11, further comprising: setting an effective transfer voltage based on the measured humidity; when a second output voltage, which is measured by applying the transfer current to a terminal of the transfer medium, is lower than or equal to the effective transfer voltage after the transfer medium is inserted into the transfer unit during the time period in which the image is transferred to the transfer medium, increasing the transfer current until the second output voltage reaches the effective transfer voltage; and controlling the transfer current to maintain the effective transfer voltage when the second output voltage reaches the effective transfer voltage. ### Claim 13 (depends on 11) The method of claim 11, further comprising: setting an effective transfer voltage based on the measured humidity; when a second output voltage, which is measured by applying the transfer current to a terminal of the transfer medium, is lower than or equal to the effective transfer voltage after the transfer medium is inserted into the transfer unit during the time period in which the image is transferred to the transfer medium, setting a target voltage based on the second output voltage; and adjusting the transfer current to apply the target voltage during the time period in which the image is transferred to the transfer medium. ### Claim 14 (depends on 9) The method of claim 9, wherein the setting of the target voltage based on the determined sensing feedback voltage when the measured humidity is equal to or higher than the set value includes differently setting the target voltage according to types of the transfer medium. ### Claim 15 (depends on 9) The method of claim 9, wherein the time period before the image is transferred to the transfer medium is a time period before the transfer medium is inserted into the transfer unit. ### Claim 16 (depends on 9) The method of claim 9, further comprising: determining that a lifetime of the transfer member reaches a lifetime limit when a third output voltage, which is measured by applying the transfer current to a terminal of the transfer medium, is equal to or higher than a set threshold value after the transfer medium is inserted into the transfer unit during the time period in which the image is transferred to the transfer medium. ### Claim 17 (depends on 9) A non-transitory computer-readable recording medium having embodied thereon a computer program which, when executed by a computer, performs the method of claim 9.