Image forming apparatus

Claim 2

An image forming apparatus comprising: an image bearing member for bearing an image; a recording material carrying member for carrying the recording material to a transfer position; transfer charging means for transferring the image from said image bearing member onto the recording material carried on the recording material carrying member at the transfer position; a power source for supplying a voltage to said transfer charging means during an image transfer operation; and control means for changing an output of said transfer charging means from a first level to a second level prior to arrival of an image area of said image bearing member at the transfer position and after arrival of a leading edge of the recording material carried on said recording material carrying member at the transfer position, wherein the second level is higher than a third level of the output of said transfer charging means which is a level when the image area is at the transfer position, and wherein said first level is lower than the third level.

Claim 3

An apparatus according to claim 1, wherein the first level is 0 volt.

Claim 4

An apparatus according to claim 1, wherein the output is changed from the second level to the third level after the change from the first level to the second level and prior to the arrival of the image area at the transfer position.

Claim 5

An apparatus according to claim 1, wherein the second level is changeable in accordance with the number of image transfer operations onto the recording material carried on the recording material carrying member.

Claim 6

An apparatus according to claim 4, wherein the second level is increased with an increase of the number of the transfer operations carried out.

Claim 7

An apparatus according to claim 4, wherein the third level is constant irrespective of the number of the transfer operations carried out.

Claim 8

An apparatus according to claim 1, wherein a time period from arrival of a leading edge of the recording material at the transfer position to the change from the first level to the second level is changeable in accordance with the number of repeated transfer operations onto the same recording material.

Claim 9

An apparatus according to claim 7, wherein the time period is decreased with increase of the number of the transfer operations carried out.

Claim 10

An apparatus according to claim 1, further comprising attraction means for electrostatically attracting the recording material prior to transfer operation.

Claim 11

An apparatus according to claim 1, wherein said apparatus is capable of forming a full color image on the recording material.

Claim 12

An apparatus according to claim 1, wherein said transfer charging means is contactable to back side of the recording material carrying member.

Claim 13

An apparatus according to claim 1, wherein said transfer charging means is constant-current-controlled, and the output of said transfer charging means is an output when constant current control is being effected.

Claim 14

An image forming apparatus comprising: an image bearing member for bearing an image; a recording material carrying member for carrying a recording material to a transfer position; transfer charging means for transferring the image from said image bearing member onto the recording material carried on the recording material carrying member at the transfer position; a power source for supplying a voltage to said transfer charging means during an image transfer operation; and control means for changing an output of said transfer charging means from a first level to a second level prior to arrival of an image area of said image bearing member at the transfer position, wherein the second level is higher than a third level of the output of said transfer charging means which is a level when the image area is at the transfer position, and wherein the first level is lower than the third level, and wherein the second level is changeable in accordance with the number of image transfer operations onto the recording material carried on the recording material carrying member.

Claim 15

An image forming apparatus comprising: an image bearing member for bearing an image; a recording material carrying member for carrying a recording material to a transfer position; transfer charging means for transferring the image from said image bearing member onto the recording material carried on the recording material carrying member at the transfer position; a power source for supplying a voltage to said transfer charging means during an image transfer operation; and control means for changing an output of said transfer charging means from a first level to a second level prior to arrival of an image area of said image bearing member at the transfer position, wherein the second level is higher than a third level of the output of said transfer charging means which is a level when the image area is at the transfer position, and wherein the first level is lower than the third level, and wherein the second level is changeable in accordance with the number of image transfer operations onto the recording material carried on the recording material carrying member.

Claim 16

An apparatus according to claim 13, wherein the first level is a zero voltage level.

Claim 17

An apparatus according claim 13, wherein said control means changes the output from the first level to the second level when the recording material is present at the transfer position.

Claim 18

An apparatus according to claim 13, wherein the output is changed from the second level to the third level after the change from the first level to the second level and prior to the arrival of the image area at the transfer position.

Claim 19

An apparatus according to claim 16, wherein when the recording material is at the transfer position, the output is changed from the first level to the second level.

Claim 20

An apparatus according to claim 15 or 17, wherein a time period from arrival of a leading edge of the recording material at the transfer position to the change from the first level to the second level is changeable in accordance with the number of repeated transfer operations onto the same recording material.

Claim 21

An apparatus according to claim 18, wherein the time period is decreased with increase of the number.

Claim 22

An apparatus according to claim 13, wherein the second level is increased with an increase of the number of the transfer operations carried out.

Claim 23

An apparatus according to claim 13, wherein the third level is constant irrespective of the number of the transfer operations carried out.

Claim 24

An apparatus according to claim 13, further comprising attraction means for electrostatically attracting the recording material prior to transfer operation.

Claim 25

An apparatus according to claim 13, wherein said apparatus is capable of forming a full color image on the recording material.

Claim 26

An apparatus according to claim 13, wherein said transfer charging means is contactable to a back side of the recording material carrying member.

Claim 27

An apparatus according to claim 13, wherein said transfer charging means is constant-current-controlled, and the output of said transfer charging means is an output when constant current control is being effected.

Claim 28

An image forming apparatus comprising: an image bearing member for bearing an image; a recording material carrying member for carrying a recording material to a transfer position; transfer charging means for transferring the image from said image bearing member onto the recording material carried on the recording material carrying member at the transfer position; a power source for supplying a voltage to said transfer charging means during an image transfer operation; and control means for changing an output of said transfer charging means from a first level to a second level prior to arrival of an image area of said image bearing member at the transfer position and after arrival of a leading edge of the recording material carried on said recording material carrying member at the transfer position, wherein the second level is higher than a third level of the output of said transfer charging means which is a level when the image area is at the transfer position, and wherein the first level is lower than the third level, and wherein a time period from arrival of a leading edge of the recording material at the transfer position to the change from the first level to the second level is changeable in accordance with the number of repeated transfer operations onto the same recording material.

Claim 29

An image forming apparatus comprising: an image bearing member for bearing an image; a recording material carrying member for carrying a recording material to a transfer position; transfer charging means for transferring the image from said image bearing member onto the recording material carried on the recording material carrying member at the transfer position; a power source for supplying a voltage to said transfer charging means during an image transfer operation; and control means for changing an output of said transfer charging means from a first level to a second level prior to arrival of an image area of said image bearing member at the transfer position and after arrival of a leading edge of the recording material carried on said recording material carrying member at the transfer position, wherein the second level is higher than a third level of the output of said transfer charging means which is a level when the image area is at the transfer position, and wherein the first level is lower than the third level, and wherein a time period from arrival of a leading edge of the recording material at the transfer position to the change from the first level to the second level is changeable in accordance with the number of repeated transfer operations onto the same recording material.

Claim 30

An apparatus according to claim 26, wherein the first level is a zero voltage level.

Claim 31

An apparatus according to claim 26, wherein said control means changes the output from the first level to the second level, when the recording material is present at the transfer position.

Claim 32

An apparatus according to claim 26, wherein the output is changed from the second level to the third level after the change from the first level to the second level and prior to the arrival of the image area at the transfer position.

Claim 33

An apparatus according to claim 26, wherein the time period is decreased with an increase of the number of the transfer operations carried out.

Claim 34

An apparatus according to claim 26, further comprising attraction means for electrostatically attracting the recording material prior to transfer operation.

Claim 35

An apparatus according to claim 26, wherein said apparatus is capable of forming a full color image on the recording material.

Claim 36

An apparatus according to claim 26, wherein said transfer charging means is contactable to a back side of the recording material carrying member.

Claim 37

An apparatus according to claim 26, wherein said transfer charging means is constant-current-controlled, and the output of said transfer charging means is the output during the constant current control being effected.

Claim 38

An apparatus according to claim 1, 13 or 26, wherein said recording material carrying member is in the form of a drum.