# US 6,111,594 A · Method of and apparatus for controlling transfer voltage based on specific resistance of paper in laser beam printer > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 6,111,594 A - Document ID: US6111594A - Status: Granted - Kind: A - Application number: 09/333,967 - Filed: 1999-06-16 - Granted: 2000-08-29 - Earliest claimed: 1999-01-11 - Assignees: Samsung Electronics Co., Ltd. - Inventors: Su-Jong Jeong - Web page: https://patentgrep.com/patent/US6111594A ## CPC - G03G 15/5029: {by measuring the copy material characteristics, e.g. weight, thickness} - G03G 15/1675: {with means for controlling the bias applied in the transfer nip} - G03G 2215/00763: of sheet resistivity - G03G: ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY ## Abstract A method of and apparatus for controlling a transfer voltage based on a paper specific resistance in a laser beam printer is provided. In the transfer voltage controlling method, the resistance of the feed rollers is detected as a first resistance before a paper sheet passes between the feed rollers. The resistance of the paper sheet and the feed rollers is detected as a second resistance when the paper sheet passes between the feed rollers. The specific resistance of the paper sheet is obtained as a third resistance by determining the difference between the first resistance and the second resistance. The resistance between a transfer roller and a photosensitive drum is detected as a fourth resistance before the paper sheet passes through the transfer roller. A composite resistance is detected as a fifth resistance by adding the third resistance to the fourth resistance, and the paper sheet is printed by applying a transfer voltage to the transfer roller based on the fifth resistance. ## Claims ### Claim 1 A method of controlling a transfer voltage in a laser beam printer, comprising the steps of: detecting a resistance of feed rollers as a first resistance before a paper sheet passes between the feed rollers; detecting a resistance of the paper sheet and the feed rollers as a second resistance when the paper sheet passes between the feed rollers; obtaining a specific resistance of the paper sheet as a third resistance by determining the difference between the first resistance and the second resistance; detecting a resistance between a transfer roller and a photosensitive drum as a fourth resistance before the paper sheet passes between the transfer roller and the photosensitive drum; obtaining a composite resistance as a fifth resistance by adding the third resistance to the fourth resistance; and printing on the paper sheet by applying a transfer voltage to the transfer roller based on the fifth resistance. ### Claim 2 (depends on 1) The method of claim 1, wherein the feed rollers comprises a conductive rubber material. ### Claim 3 (depends on 2) The method of claim 2, further comprised of the first resistance being detected by applying a feed roller voltage to the feed rollers, measuring a current flowing through the feed rollers, and determining the resistance of the feed rollers based upon the current flowing through the feed rollers. ### Claim 4 (depends on 3) The method of claim 3, further comprised of the second resistance being detected by applying the feed roller voltage to the feed rollers when a leading edge of the paper sheet is introduced between the feed rollers, measuring a current flowing in the feed rollers as the paper sheet passes between the feed rollers, and determining the resistance of the feed rollers and the paper sheet passing between the feed rollers based upon the current flowing in the feed rollers as the paper sheet passes between the feed rollers. ### Claim 5 (depends on 4) The method of claim 4, further comprised of the fourth resistance being detected by applying a predetermined transfer voltage to the transfer roller, measuring a current between the transfer roller and the photosensitive drum, and determining the resistance between the transfer roller and the photosensitive drum based upon the current between the transfer roller and the photosensitive drum. ### Claim 6 (depends on 5) The method of claim 5, wherein the transfer voltage based on the fifth resistance corresponds to the composite resistance. ### Claim 7 (depends on 6) The method of claim 6, wherein the feed roller voltage is a high voltage corresponding to a first pulse amplitude modulation signal and the transfer voltage is a high voltage corresponding to a second pulse amplitude modulation signal. ### Claim 8 (depends on 1) The method of claim 1, further comprised of the first resistance being detected by applying a feed roller voltage to the feed rollers, measuring a current flowing through the feed rollers, and determining the resistance of the feed rollers based upon the current flowing through the feed rollers. ### Claim 9 (depends on 8) The method of claim 8, further comprised of the second resistance being detected by applying the feed roller voltage to the feed rollers when a leading edge of the paper sheet is introduced between the feed rollers, measuring a current flowing in the feed rollers as the paper sheet passes between the feed rollers, and determining the resistance of the feed rollers and the paper sheet passing between the feed rollers based upon the current flowing in the feed rollers as the paper sheet passes between the feed rollers. ### Claim 10 (depends on 9) The method of claim 9, further comprised of the fourth resistance being detected by applying a predetermined transfer voltage to the transfer roller, measuring a current between the transfer roller and the photosensitive drum, and determining the resistance between the transfer roller and the photosensitive drum based upon the current between the transfer roller and the photosensitive drum. ### Claim 11 (depends on 10) The method of claim 10, wherein the transfer voltage based on the fifth resistance corresponds to the composite resistance. ### Claim 12 (depends on 11) The method of claim 11, wherein the feed roller voltage is a high voltage corresponding to a first pulse amplitude modulation signal and the transfer voltage is a high voltage corresponding to a second pulse amplitude modulation signal. ### Claim 13 (depends on 1) The method of claim 1, wherein the transfer voltage based on the fifth resistance corresponds to the composite resistance. ### Claim 14 A method of controlling a transfer voltage in a laser beam printer, comprising the steps of: detecting a resistance of feed rollers as a first resistance before a printing medium passes between the feed rollers; detecting a resistance of the printing medium and the feed rollers as a second resistance when the printing medium passes between the feed rollers; obtaining a specific resistance of the printing medium as a third resistance by determining the difference between the first resistance and a second resistance; detecting a resistance between a transfer roller and a photosensitive drum as a fourth resistance before the printing medium passes between the transfer roller and the photosensitive drum; obtaining a composite resistance as a fifth resistance by adding the third resistance to the fourth resistance; and printing on the printing medium by applying a transfer voltage to the transfer roller based on the fifth resistance. ### Claim 15 (depends on 14) The method of claim 14, wherein the feed rollers comprise a conductive rubber material. ### Claim 16 (depends on 14) The method of claim 14, further comprised of the first resistance being detected by applying a feed roller voltage to the feed rollers, measuring a current flowing through the feed rollers, and determining the resistance of the feed rollers based upon the current flowing through the feed rollers. ### Claim 17 (depends on 16) The method of claim 16, further comprised of the second resistance being detected by applying the feed roller voltage to the feed rollers when a leading edge of the printing medium is introduced between the feed rollers, measuring a current flowing in the feed rollers as the printing medium passes between the feed rollers, and determining the resistance of the feed rollers and the printing medium passing between the feed rollers based upon the current flowing in the feed rollers as the printing medium passes between the feed rollers. ### Claim 18 (depends on 17) The method of claim 17, further comprised of the fourth resistance being detected by applying a predetermined transfer voltage to the transfer roller, measuring a current between the transfer roller and the photosensitive drum, and determining the resistance between the transfer roller and the photosensitive drum based upon the current between the transfer roller and the photosensitive drum. ### Claim 19 (depends on 18) The method of claim 18, wherein the transfer voltage based on the fifth resistance corresponds to the composite resistance. ### Claim 20 (depends on 19) The method of claim 19, wherein the feed roller voltage is a high voltage corresponding to a first pulse amplitude modulation signal and the transfer voltage is a high voltage corresponding to a second pulse amplitude modulation signal. ### Claim 21 (depends on 20) The method of claim 20, wherein the feed rollers comprise a conductive rubber material. ### Claim 22 (depends on 18) The method of claim 18, wherein the feed rollers comprise a conductive rubber material. ### Claim 23 (depends on 14) The method of claim 14, wherein the transfer voltage based on the fifth resistance corresponds to the composite resistance. ### Claim 24 An apparatus for controlling a transfer voltage in a laser beam printer, comprising: a controller controlling the recording of an image on a printing medium, the controller generating a first control signal to control a feed roller voltage to be applied to feed rollers of the laser beam printer and generating a second control signal to control a transfer voltage to be applied to a transfer roller of the laser beam printer, the controller determining a specific resistance of the printing medium as a difference between a first detected resistance of the feed rollers without being in contact with the printing medium and a second detected resistance of the feed rollers and the printing medium in contact with the feed rollers, the controller determining a composite resistance by adding said specific resistance of the printing medium to a third detected resistance, the third detected resistance being a resistance between the transfer roller and a photosensitive drum of the laser beam printer without being in contact with the printing medium, and the controller generating a said second control signal to apply a transfer voltage to the transfer roller for printing on the printing medium based upon said composite resistance; and a high voltage supply circuit coupled to said controller, said high voltage supply circuit generating said feed roller voltage to be applied to the feed rollers corresponding to a said first control signal from said controller, generating said transfer voltage to be applied to the transfer roller corresponding to a said second control signal from said controller, and detecting said first detected resistance, said second detected resistance and said third detected resistance and providing said first detected resistance, said second detected resistance and said third detected resistance to said controller. ### Claim 25 (depends on 24) The apparatus of claim 24, wherein said printing medium comprises a paper sheet. ### Claim 26 (depends on 24) The apparatus of claim 24, further comprising a sensor coupled to said controller to sense the introduction of a leading edge of the printing medium between the feed rollers. ### Claim 27 (depends on 26) The apparatus of claim 26, wherein said printing medium comprises a paper sheet. ### Claim 28 (depends on 24) The apparatus of claim 24, further comprising a memory coupled to said controller, said memory for storing a program to control provision of the transfer voltage and for storing respective values of said first detected resistance, said second detected resistance, said third detected resistance, said specific resistance of the printing medium and said composite resistance. ### Claim 29 (depends on 28) The apparatus of claim 28, wherein said printing medium comprises a paper sheet. ### Claim 30 (depends on 24) The apparatus of claim 24, wherein said high voltage supply circuit comprises: a first transformer including a first primary winding for receiving a voltage from a power supply and a first secondary winding for generating a higher voltage than a voltage on the first primary winding; a first diode coupled to the first primary winding and to a ground for clipping a voltage induced from the first primary winding to the first secondary winding; a first transistor having a base for receiving a said first control signal from said controller, a collector coupled to the first primary winding and an emitter connected to the ground, for selectively controlling the voltage on the first primary winding to be induced to the first secondary winding based on a said first control signal; a second diode having an anode coupled to the first secondary winding for rectifying a voltage induced to the first secondary winding; a first smoothing capacitor for smoothing a rectified voltage and being connected to the second diode and to the first secondary winding for supplying the feed roller voltage to the feed rollers; a first resistor coupled between the first secondary winding and the ground for detecting a current flowing through the feed rollers, wherein a voltage used for detecting the specific resistance of the printing medium is output based on the current flowing through the first resistor; a second transformer including a second primary winding for receiving a voltage from the power supply and a second secondary winding for generating a higher voltage than a voltage on the second primary winding; a third diode coupled to the second primary winding and to the ground for clipping a voltage induced from the second primary winding to the second secondary winding; a second transistor having a base for receiving a said second control signal from the controller, a collector coupled to the second primary winding and a emitter connected to the ground for selectively controlling the voltage of the second primary winding to be induced in the second secondary winding based on a said second control signal; a fourth diode having an anode coupled to the second secondary winding for rectifying a voltage induced to the second secondary winding; a second capacitor for smoothing a rectified voltage and for supplying the transfer voltage to the transfer roller, the second capacitor being connected to the fourth diode and to the second secondary winding; and a second resistor coupled between the second secondary winding and the ground for detecting a current flowing through the transfer roller, wherein a voltage indicating said third detected resistance between the transfer roller and the photosensitive drum is output based on the current flowing through said second resistor. ### Claim 31 (depends on 30) The apparatus of claim 30, wherein said printing medium comprises a paper sheet. ### Claim 32 (depends on 30) The apparatus of claim 30, further comprising a memory coupled to said controller, said memory for storing a program to control provision of the transfer voltage and for storing respective values of said first detected resistance, said second detected resistance, said third detected resistance, said specific resistance of the printing medium and said composite resistance. ### Claim 33 (depends on 32) The apparatus of claim 32, further comprising a sensor coupled to said controller to sense the introduction of a leading edge of the printing medium between the feed rollers. ### Claim 34 (depends on 33) The apparatus of claim 33, wherein said printing medium comprises a paper sheet. ### Claim 35 An apparatus for controlling a transfer voltage in a laser beam printer, comprising: means for detecting a resistance of feed rollers as a first resistance before a paper sheet passes between the feed rollers; means for detecting a resistance of the paper sheet and the feed rollers as a second resistance when the paper sheet passes between the feed rollers; means for obtaining a specific resistance of the paper sheet as a third resistance by determining the difference between the first resistance and the second resistance; means for detecting a resistance between a transfer roller and a photosensitive drum as a fourth resistance before the paper sheet passes between the transfer roller and the photosensitive drum; means for obtaining a composite resistance as a fifth resistance by adding the third resistance to the fourth resistance; and means for applying a transfer voltage to the transfer roller based on the fifth resistance for printing on the paper sheet. ### Claim 36 (depends on 35) The apparatus of claim 35, wherein the feed rollers comprise a conductive rubber material.