# US 5,132,738 A · Image forming apparatus with cleaning mechanism for charging electrode > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,132,738 A - Document ID: US5132738A - Status: Granted - Kind: A - Application number: 07/789,547 - Filed: 1991-11-08 - Granted: 1992-07-21 - Earliest claimed: 1987-12-28 - Assignees: Canon Kabushiki Kaisha - Inventors: Shunji Nakamura; Hiroki Kisu; Yohji Tomoyuki; Masanobu Saito; Junji Araya; Toshio Miyamoto - Web page: https://patentgrep.com/patent/US5132738A ## CPC - G03G 15/1675: {with means for controlling the bias applied in the transfer nip} - G03G 15/0225: {provided with means for cleaning the charging member} - G03G 2215/021: by contact, friction or induction - G03G: ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY ## Abstract An image forming apparatus includes a movable image bearing member, a charger for electrically charging the image bearing member, latent image forming device for forming a latent image with use of the charger, a developing device for developing the latent image formed by the latent image forming device with toner electrically charged to a polarity the same as a polarity to which the image bearing member is charged by the charger, image transfer member contactable to a back side of a transfer material to transfer a toner image provided by the developing device from the image bearing member to the transfer material, a voltage application device for applying a voltage to the transfer member, the voltage application device applying a voltage having a polarity the same as that of the toner to the transfer member during non-transferring operation, and a device for providing different potentials for a portion of the image bearing member to be opposed to the image transfer device during the non-transfer action by said image transfer member and for a portion of said image bearing member to be opposed to said image transfer member during transfer action by the image transfer member. ## Claims ### Claim 1 An image forming apparatus, comprising: a movable image bearing member; means for electrically charging said image bearing member to a first potential; latent image forming means for forming a latent image with use of said charging means; developing means for developing the latent image formed by said latent image forming means with toner electrically charged to a polarity the same as a polarity of the first potential; image transfer means contactable to a back side of a transfer material at a transfer position to transfer a toner image provided by said developing means from said image bearing member to the transfer material; voltage application means for applying a voltage to said image transfer means, said voltage application means applying a voltage having a polarity the same as that of the toner to said image transfer means during non-transfer action by said transfer means; and means for providing a second potential for that portion of said image bearing member which is to be presented to the transfer position during said voltage application by said voltage application means, wherein the second potential is different from the first potential and is remote from the first potential in a direction opposite from a polarity of the electric charge of the toner. ### Claim 2 (depends on 1) An apparatus according to claim 1, wherein an absolute value of the second potential is lower than that of the first potential. ### Claim 3 (depends on 2) An apparatus according to claim 2, wherein said different potential providing means includes means for removing charge from said portion of said image bearing member. ### Claim 4 (depends on 3) An apparatus according to claim 3, wherein said image bearing member includes a photosensitive member, and the potential providing means includes means for projecting light to said photosensitive member. ### Claim 5 (depends on 1) An apparatus according to claim 1, wherein said charging means functions as said different potential providing means, and wherein an absolute value of the second potential is lower than that of the first potential. ### Claim 6 (depends on 5) An apparatus according to claim 5, wherein said charging means does not electrically charge said portion of said imagebearing member. ### Claim 7 (depends on 1) An apparatus according to claim 1, wherein said voltage application means applies a voltage having a polarity opposite to a polarity of the toner to the transfer means during the transfer action. ### Claim 8 (depends on 1) An apparatus according to claim 1, wherein said image transfer means is in the form of a roller. ### Claim 9 (depends on 1, 8) An apparatus according to claim 1 or 8, wherein said transfer means is contactable to said image bearing member. ### Claim 10 (depends on 1) An apparatus according to claim 1, wherein said transfer means is press-contacted to said image bearing member with a pressure not more than 300 g/cm.sup.2. ### Claim 11 (depends on 1, 10) An apparatus according to claim 1 or 10, wherein said image transfer means has a hardness of not more than 30 degrees (JISA). ### Claim 12 (depends on 1) An apparatus according to claim 1, wherein said image bearing member includes a photosensitive member, and wherein said latent image forming means includes light application means for projecting onto the photosensitive member a light beam modulated in accordance with an image signal. ### Claim 13 (depends on 12) An apparatus according to claim 12, wherein said latent image forming means includes a laser scanning means for projecting a laser beam modulated in accordance with an image signal. ### Claim 14 (depends on 1) An apparatus according to claim 1, further comprising means for cleaning said image bearing member, disposed downstream of said image transfer means with respect to a rotational direction of movement of said image bearing member. ### Claim 15 (depends on 1) An apparatus according to claim 1, wherein said charging means is contactable to said image bearing member to electrically charge it. ### Claim 16 (depends on 15) An apparatus according to claim 15 wherein said charging means is in the form of a roller. ### Claim 17 (depends on 15) An apparatus according to claim 15, wherein said charging means is in the form of a blade. ### Claim 18 (depends on 15) An apparatus according to claim 15, wherein said charging means, when it is contacted to the portion of said image bearing member in which an electrostatic latent image is to be formed, is supplied with a superimposed voltage of an AC voltage and a DC voltage. ### Claim 19 (depends on 18) An apparatus according to claim 18, only an AC voltage is applied to said charging means when said portion of said image bearing member is contacted to said charging means. ### Claim 20 (depends on 1) An apparatus according to claim 1, said developing means, when said portion of said image bearing member is at said developing means, prevents toner deposition onto said image bearing member. ### Claim 21 (depends on 1, 7, 15) An apparatus according to claim 1, 7 or 15, wherein said voltage application means is capable of applying a voltage to said charging means. ### Claim 22 (depends on 1) An apparatus according to claim 1, wherein when said voltage application means applies the voltage, an electric field effective to transfer the toner from said transfer means to said image bearing member is formed. ### Claim 23 An image forming apparatus, comprising: a movable image bearing member; means for electrically charging said image bearing member to a first potential; latent image forming means for forming a latent image with use of said charging means; developing means for developing the latent image formed by said latent image forming means with toner electrically charged to a polarity the same as a polarity of the first potential; image transfer means contactable to a back side of a transfer material at a transfer position to transfer a toner image provided by said developing means from said image bearing member to the transfer material; voltage application means for applying a voltage to said image transfer means, said voltage application means applying a voltage having a polarity the same as that of the toner to said image transfer means during non-transfer action by said transfer means; and means for providing a second potential for that portion of said image bearing member which is to be presented to the transfer position during said voltage application by said voltage application means, wherein the second potential is different from the first potential, wherein said different second potential is lower than an absolute value of the first potential, wherein said different potential providing means provides a potential having an absolute value for said portion of said image bearing member, the absolute value being smaller than an absolute value of a voltage applied to said image transfer means by said voltage applying means during non-transfer action. ### Claim 24 An image forming apparatus, comprising: a movable image bearing member; charging means for electrically charging said image bearing member to a first potential; latent image forming means for forming a latent image on said image bearing member with use of said charging means; developing means for developing the latent image formed by said latent image forming means with toner; image transfer means contactable to a back side a transfer material at a transfer position to transfer a toner image provided by said developing means from said image bearing member to the transfer material; potential application means for applying to said image transfer means a second potential during non-transfer action of said image transfer means to form an electric field to transfer the toner from said transfer means to said image bearing member, and a third potential during transfer action of the image transfer means; and means for providing said image bearing member with such a potential that a difference between the second potential and a potential of that portion of said image bearing member which is to be presented to the transfer position during application of the second potential, is larger than a potential difference between the second potential and the first potential and the potential of that portion of the image bearing member is different from the first potential and is remote from the first potential in a direction opposite from a polarity of the electric charge of the toner. ### Claim 25 (depends on 24) An apparatus according to claim 24, wherein said first potential has a polarity opposite to a polarity of the second potential. ### Claim 26 (depends on 24) An apparatus according to claim 24, wherein an absolute value of the second potential is lower than that of the third potential. ### Claim 27 (depends on 24, 26) An apparatus according to claim 24 or 26, wherein the second potential applied to said image transfer means is substantially 0 V. ### Claim 28 (depends on 24) An apparatus according to claim 24, wherein said potential providing means increases the potential of said portion of said image bearing member beyond the first potential. ### Claim 29 (depends on 28) An apparatus according to claim 28, wherein said potential providing means provides said portion of said image bearing member with a potential having an absolute value lower than an absolute value of the second potential. ### Claim 30 (depends on 24) An apparatus according to claim 24, wherein an absolute value of the potential of that portion of said image bearing member is lower than that of the first potential. ### Claim 31 (depends on 30) An apparatus according to claim 30, wherein said charging means functions as said potential providing means and does not electrically charge said portion of said image bearing member. ### Claim 32 (depends on 30) An apparatus according to claim 30, wherein said potential providing means includes means for removing charge from said portion of said image bearing member. ### Claim 33 (depends on 32) An apparatus according to claim 32, wherein said image bearing member includes a photosensitive member, and the potential providing means includes means for projecting light to said photosensitive member. ### Claim 34 (depends on 24) An apparatus according to claim 24, wherein said potential application means applies a potential having a polarity opposite to a polarity of the toner to the transfer means during the transfer action. ### Claim 35 (depends on 24) An apparatus according to claim 24, wherein said image transfer means is in the form of a roller. ### Claim 36 (depends on 22, 35) An apparatus according to claim 22 or 35 wherein said transfer means is contactable to said image bearing member. ### Claim 37 (depends on 24) An apparatus according to claim 24, wherein said transfer means is press-contacted to said image bearing member with a pressure not more than 300 g/cm.sup.2. ### Claim 38 (depends on 24, 33) An apparatus according to claim 24 or 33, wherein said image transfer means has a hardness of not more than 30 degrees (JISA). ### Claim 39 (depends on 24) An apparatus according to claim 24, wherein said image bearing member includes a photosensitive member, and wherein said latent image forming means includes light application means for projecting onto the photosensitive member a light beam modulated in accordance with an image signal. ### Claim 40 (depends on 39) An apparatus according to claim 39, wherein said latent image forming means includes a laser scanning means for projecting a laser beam modulated in accordance with an image signal. ### Claim 41 (depends on 24) An apparatus according to claim 24, further comprising means for cleaning said image bearing member, disposed downstream of said image transfer means with respect to a rotational direction of movement of said image bearing member. ### Claim 42 (depends on 24) An apparatus according to claim 24, wherein said charging means is contactable to said image bearing member to electrically charge it. ### Claim 43 (depends on 42) An apparatus according to claim 42, wherein said charging means is in the form of a roller. ### Claim 44 (depends on 42) An apparatus according to claim 42, wherein said charging means is in the form of a blade. ### Claim 45 (depends on 42) An apparatus according to claim 42, wherein said charging means, when it is contacted to the portion of said image bearing member in which an electrostatic latent image is to be formed, is supplied with a superimposed voltage of an AC voltage and a DC voltage. ### Claim 46 (depends on 45) An apparatus according to claim 45, only an AC voltage is applied to said charging means when said portion of said image bearing member is contacted to said charging means. ### Claim 47 (depends on 46) An apparatus according to claim 46, said developing means, when said portion of said image bearing member is at said developing means, prevents toner deposition onto said image bearing member. ### Claim 48 (depends on 24, 42) An apparatus according to claim 24 or 42, wherein said potential application means is capable of applying a voltage to said charging means. ### Claim 49 An image forming apparatus, comprising: a movable image bearing member for bearing a latent image and a developed image from the latent image; a charging electrode contactable to said image bearing member at a charging position; potential application means for applying a voltage to said electrode, said potential application means applying to said electrode a first potential when an image area of said image bearing member is in said charging position, and a second potential when a non-image area of said image bearing member is in said charging position; and means for providing said image bearing member with such a potential that a potential difference between the second potential and a potential of that portion of said image bearing member which is to be presented to the charging position during application of the second potential, is larger than a potential difference between the second potential and a high potential of the latent image constituted by the high potential and a low potential, wherein by the first mentioned potential difference, an electric field effective to transfer toner from said charging electrode to said image bearing member is formed. ### Claim 50 An image forming apparatus, comprising: a movable image bearing member; charging means for electrically charging said image bearing member to a first potential; latent image forming means for forming a latent image on said image bearing member with use of said charging means; developing means for developing the latent image formed by said latent image forming means with toner; image transfer means contactable to a back side of a transfer material at a transfer position to transfer a toner image provided by said developing means from said image bearing member to the transfer material; potential application means for applying to said image transfer means a second potential during non-transfer action of said image transfer means to form an electric field to transfer the toner from said transfer means to said image bearing member, and a third potential during transfer action; means for providing a fourth potential for that portion of said image bearing member which is to be presented to the transfer position during the second potential application by said potential application means, wherein an absolute value of the fourth potential is lower than that of the first potential; wherein said transfer means is press-contacted to said image bearing member with a pressure not more than 300 g/cm.sup.2. ### Claim 51 An image forming apparatus, comprising: a movable image bearing member; charging means for electrically charging said image bearing member to a first potential; latent image forming means for forming a latent image on said image bearing member with use of said charging means; developing means for developing the latent image formed by said latent image forming means with toner; image transfer means contactable to a back side of a transfer material at a transfer position to transfer a toner image provided by said developing means from said image bearing member to the transfer material; potential application means for applying to said image transfer means a second potential during non-transfer action of said image transfer means to form an electric field to transfer the toner from said transfer means to said image bearing member, and a third potential during transfer action; means for providing a fourth potential for that portion of said image bearing member which is to be presented to the transfer position during the second potential application by said potential application means, wherein the fourth potential is different from the first potential; wherein said transfer means has a rubber hardness of not greater than 30 degrees (JISA). ### Claim 52 (depends on 51) An apparatus according to claim 51, wherein said transfer means is contactable to said image bearing member. ### Claim 53 An image forming apparatus, comprising: a movable image bearing member; image forming means for forming a toner image on said image bearing member; image transfer means contactable to a back side of an image transfer material at a transfer position to transfer the toner image from said image bearing member to the transfer material; electric field forming means for forming an electric field between said image bearing member and said transfer means, said electric field forming means forming a first electric field effective to transfer the toner from said transfer means to said image bearing member and a second electric field bearing a direction opposite to that of the first electric field, when the transfer material is not present at the transfer position. ### Claim 54 (depends on 53) An apparatus according to claim 53, wherein; said image transfer means is in the form of a roller. ### Claim 55 (depends on 53) An apparatus according to claim 53, further comprising means for cleaning said image bearing member, disposed downstream of said image transfer means with respect to a rotational direction of movement of said image bearing member. ### Claim 56 (depends on 53, 54) An apparatus according to claim 53 or 54, wherein said transfer means is contactable to said image bearing member. ### Claim 57 (depends on 56) An apparatus according to claim 56, wherein said transfer means is press-contacted to said image bearing member with a pressure not more than 300 g/cm.sup.2. ### Claim 58 (depends on 56) An apparatus according to claim 56, wherein said image transfer means has a hardness of not more than 30 degrees (JISA). ### Claim 59 (depends on 53) An apparatus according to claim 53, wherein said electric field forming means applies to said transfer means a potential having the same polarity as the toner, when the first electric field is formed. ### Claim 60 (depends on 53, 59) An apparatus according to claim 53 or 59, wherein said electric field forming means applies to said transfer means a potential having a polarity opposite from that of the toner, when the second electric field is formed. ### Claim 61 (depends on 53) An apparatus according to claim 53, wherein said electric field forming means applies a DC voltage between said image bearing member and said transfer means. ### Claim 62 An image forming apparatus, comprising: a movable image bearing member; means for electrically charging said image bearing member to a first potential; toner image forming means for forming a toner image on said image bearing member; image transfer means contactable to a back side of a transfer material at a transfer position to transfer the toner image from said image bearing member to the transfer material; potential application means for applying a second potential to said transfer means when the transfer material is not at the transfer position; potential providing means for providing a third potential for that portion of said image bearing member which is to be presented to the transfer position during the second potential application by said potential applying means, the third potential is different from the first potential and is remote from the first potential in a direction opposite from a polarity of the electric charge of the toner. ### Claim 63 (depends on 62) An apparatus according to claim 62, wherein said image forming means forms the image with aid of said charging means. ### Claim 64 (depends on 62) An apparatus according to claim 62, wherein during application of the second potential, an electric field is formed at the transfer position in a direction for transferring the toner from said transfer means to said image bearing member. ### Claim 65 (depends on 62, 64) An apparatus according to claim 62 or 64, wherein the second potential has a polarity which is the same as that of toner charge. ### Claim 66 (depends on 62, 63) An apparatus according to claim 62 or 63, wherein the first potential has a polarity which is the same as that of toner charge. ### Claim 67 (depends on 66) An apparatus according to claim 66, wherein the third potential has a polarity which is the same as that of the first potential and an absolute value of the second potential is higher than that of the first potential. ### Claim 68 (depends on 67) An apparatus according to claim 67, wherein said charging means also functions as said potential providing means. ### Claim 69 (depends on 68) An apparatus according to claim 68, wherein said charging means does not charge said portion of said image bearing member. ### Claim 70 (depends on 67) An apparatus according to claim 67, wherein said potential providing means also functions to remove electric charge from said portion of said image bearing member. ### Claim 71 (depends on 70) An apparatus according to claim 70, wherein said image bearing member includes a photosensitive member, and the different potential providing means includes means for projecting light to said photosensitive member. ### Claim 72 (depends on 67) An apparatus according to claim 67, wherein the second potential has the same polarity as that of the first potential and an absolute value of the second potential is higher than that of the first potential. ### Claim 73 (depends on 62, 63) An apparatus according to claim 62 or 63, wherein said charging means also functions as said potential providing means. ### Claim 74 (depends on 73) An apparatus according to claim 73, wherein said charging means does not charge said portion of said image bearing member. ### Claim 75 (depends on 62) An apparatus according to claim 62, wherein said transfer means is contactable to said image bearing member. ### Claim 76 (depends on 62, 75) An apparatus according to claim 62 or 75, wherein said image transfer means is in the form of a roller. ### Claim 77 (depends on 75) An apparatus according to claim 75, wherein said transfer means is press-contacted to said image bearing member with a pressure not more than 300 g/cm.sup.2. ### Claim 78 (depends on 75) An apparatus according to claim 75, wherein said image transfer means has a hardness of not more than 30 degrees. ### Claim 79 (depends on 78) An apparatus according to claim 78, wherein said charging means also functions as said potential providing means. ### Claim 80 An image forming apparatus, comprising: a movable image bearing member; means for electrically charging said image bearing member to a first potential; toner image forming means for forming a toner image on said image bearing member; image transfer means contactable to a back side of a transfer material at a transfer position to transfer the toner image from said image bearing member to the transfer material; potential application means for applying a second potential to said transfer means when the transfer material is not at the transfer position; potential providing means for providing a third potential for that portion of said image bearing member which is to be presented to the transfer position during the second potential application by said potential applying means, wherein a first electric field is formed during potential application by said potential applying means at the transfer position by the second and third potentials, the first electric field being effective to transfer the toner from said transfer means to said image bearing member, and wherein a second electric field is formed at the transfer position by the first and second potential, and wherein said first electric field is more effective to transfer the toner from said transfer means to said image bearing member than said second electric field. ### Claim 81 (depends on 80) An apparatus according to claim 80, wherein said image forming means forms the image with the aid of said charging means. ### Claim 82 (depends on 80, 81) An apparatus according to claims 80 or 81, wherein the first potential has a polarity which is the same as that of toner charge. ### Claim 83 (depends on 82) An apparatus according to claim 82, wherein the third potential has a polarity which is the same as that of the first potential and an absolute value of the third potential is lower than that of the first potential. ### Claim 84 (depends on 83) An apparatus according to claim 83, wherein said charging means also functions as said potential providing means. ### Claim 85 (depends on 82) An apparatus according to claim 82, wherein the second potential has the same polarity as that of the first potential and an absolute value of the second potential is higher than an absolute value of the first potential. ### Claim 86 (depends on 80) An apparatus according to claim 80, wherein the second potential has a polarity which is the same as that of toner charge. ### Claim 87 (depends on 80, 81) An apparatus according to claim 80 or 81, wherein said charging means also functions as said potential providing means. ### Claim 88 (depends on 87) An apparatus according to claim 87, wherein said charging means does not charge said portion of said image bearing member. ### Claim 89 (depends on 80) An apparatus according to claim 80, wherein said image transfer means is in the form of a roller. ### Claim 90 (depends on 80) An apparatus according to claim 80, wherein said transfer means is press-contacted to said image bearing member with a pressure not more than 300 g/cm.sup.2. ### Claim 91 (depends on 80) An apparatus according to claim 80, wherein said image transfer means has a hardness of not more than 30 degrees (JISA). ### Claim 92 (depends on 80, 89, 90, 91) An apparatus according to any one of claims 80, 89, 90 and 91, wherein said transfer means is contactable to said image bearing member.