Apparatus for and method of fixing toner image to recording medium

Claim 1

An apparatus for fixing a tone image to a sheet, comprising: a fixing roller; a pressing roller normally urged toward said fixing roller for pressing a sheet with an unfixed toner image carried on a surface thereof against said fixing roller to fix the unfixed toner image to said sheet when said sheet passes in one direction through a rolling contact region between said fixing roller and said pressing roller; a heating roller disposed on one side of said fixing roller opposite to said pressing roller; a first heating source disposed in said heating roller for heating said heating roller; an endless heat transfer belt trained around said heating roller and said fixing roller for transferring heat from said first heating source to heat the unfixed toner image on said sheet when said sheet passes through said rolling contact region; and a second heating source disposed in said pressing roller for heating said pressing roller, characterized by comprising; a control device for energizing said first heating source and said second heating source when the apparatus is in a standby mode, and energizing said first heating source when the apparatus is in a sheet feed mode, and energizing said second heating source when the apparatus is in the sheet feed mode only if said sheet is of a size larger than a predetermined size.

Claim 2

The apparatus according to any of the preceding claims wherein said control device includes a first detecting device for detecting a surface temperature of said heating roller, second detecting device for detecting a surface temperature of said fixing roller, and third detecting device for detecting a surface temperature of said pressing roller; said control device further includes a controller for controlling said first heating source based on the surface temperature detected by said first detecting device and controlling said second heating source based on the surface temperature detected by said third detecting device when the apparatus is in said standby mode, and controlling said first heating source based on the surface temperature detected by said second detecting device when the apparatus is in said sheet feed mode, and/or further preferably comprising: a decision device for deciding whether the apparatus is in said standby mode or said sheet feed mode, said decision device including a determining device for determining that the apparatus is in said sheet feed mode when a sheet feed command is supplied, and that the apparatus is in said standby mode when a sheet feed command is not supplied.

Claim 3

An apparatus for fixing a tone image to a sheet, comprising: a fixing roller; a pressing roller normally urged toward said fixing roller for pressing a sheet with an unfixed toner image carried on a surface thereof against said fixing roller to fix the unfixed toner image to said sheet when said sheet passes in one direction through a rolling contact region between said fixing roller and said pressing roller; a heating roller disposed on one side of said fixing roller opposite to said pressing roller; a first heating source disposed in said heating roller for heating said heating roller; an endless heat transfer belt trained around said heating roller and said fixing roller for transferring heat from said first heating source to heat the unfixed toner image on said sheet when said sheet passes through said rolling contact region; and a second heating source disposed in said pressing roller for heating said pressing roller; and a decision device for determining the size of said sheet, characterized by comprising: a control device for energizing said first heating source and said second heating source when the apparatus is in a standby mode, and energizing said first heating source when the apparatus is in a sheet feed mode, energizing said second heating source when the apparatus is in the sheet feed mode if said sheet is of a size larger than a predetermined size as determined by said decision device, and de-energizing said second heating source when the apparatus is in the sheet feed mode if said sheet is of a size smaller than said predetermined size as determined by said decision device.

Claim 4

The apparatus according to any of the preceding claims wherein said control device includes a first detecting device for detecting a surface temperature of said heating roller, a second detecting device for detecting a surface temperature of said fixing roller, and a third detecting device for detecting a surface temperature of said pressing roller; and said control device further includes a controller for controlling said first heating source based on the surface temperature detected by said first detecting device and controlling said second heating source based on the surface temperature detected by said third detecting device when the apparatus is in said standby mode, and controlling said first heating source based on the surface temperature detected by said second detecting device when the apparatus is in said sheet feed mode, and/or further preferably comprising: a decision device for deciding whether the apparatus is in said standby mode or said sheet feed mode, said decision device including a determining device for determining that the apparatus is in said sheet feed mode when a sheet feed command is supplied, and that the apparatus is in said standby mode when a sheet feed command is not supplied.

Claim 5

An apparatus for fixing a tone image to a sheet, comprising: a fixing roller; a pressing roller held in rolling contact with said fixing roller under a predetermined pressure for pressing a sheet with an unfixed toner image carried on a surface thereof against said fixing roller to fix the unfixed toner image to said sheet when said sheet passes in one direction through a rolling contact region between said fixing roller and said pressing roller; a heating roller disposed on one side of said fixing roller opposite to said pressing roller; a first heating source disposed in said heating roller for heating said heating roller; an endless heat transfer belt trained around said heating roller and said fixing roller for transferring heat from said first heating source to heat the unfixed toner image on said sheet when said sheet passes through said rolling contact region; and a second heating source disposed in said pressing roller for heating said pressing roller, characterized in that said first heating source includes a first heater for heating said heating roller when the sheet is of a size larger than a predetermined size and a second heater for heating said heating roller when the sheet is of a size smaller than said predetermined size.

Claim 6

The apparatus according to any of the preceding claims wherein said first heater and said second heater include halogen lamps, respectively, and/or wherein preferably said second heating source includes a halogen lamp, and/or further preferably comprising: a control device for energizing said first heater and said second heating source when the apparatus is in a standby mode, and energizing said first heating source when the apparatus is in a sheet feed mode such that said first heater is energized if said sheet is of the size larger than said predetermined size, and said second header is energized if said sheet is of the size smaller than said predetermined size, and/or wherein preferably said control device includes a heater driver for energizing only said first heater if said sheet is of the size larger than said predetermined size and energizing only said second heater if said sheet is of the size smaller than said predetermined size, and/or further preferably comprising: a decision device for determining the size of said sheet, said control device including a heater driver for energizing said first heater when the apparatus is in said sheet feed mode if said sheet is of the size larger than said predetermined size as determined by said decision device, and energizing said second heater when the apparatus is in said sheet feed mode if said sheet is of the size smaller than said predetermined size as determined by said decision device.

Claim 7

A method of fixing a tone image to a sheet with an apparatus having a fixing roller, a pressing roller normally urged toward said fixing roller for pressing a sheet with an unfixed toner image carried on a surface thereof against said fixing roller to fix the unfixed toner image to said sheet when said sheet passes in one direction through a rolling contact region between said fixing roller and said pressing roller, a heating roller disposed on one side of said fixing roller opposite to said pressing roller, a first heating source disposed in said heating roller for heating said heating roller, said first heating source including a first heater for heating said heating roller when the sheet is of a size larger than a predetermined size and a second heater for heating said heating roller when the sheet is of a size smaller than said predetermined size, an endless heat transfer belt trained around said heating roller and said fixing roller for transferring heat from said first heating source to heat the unfixed toner image on said sheet when said sheet passes through said rolling contact region, and second heating source disposed in said pressing roller for heating said pressing roller, characterized in that said method comprises steps of: deciding whether said apparatus is in a sheet feed mode or not; determining the size of said sheet if said apparatus is in the sheet feed mode; energizing said first heater of the first heating source if the size of said sheet is larger than a predetermined size; and energizing said second heater of the first heating source if the size of said sheet is smaller than said predetermined size.

Claim 8

The method according to any of the preceding claims further comprising: a step of energizing said second heating source when said first heater of the first heating source is energized. and/or further preferably comprising: a step of de-energizing said second heating source when said second heater of the first heating source is energized.

Claim 9

An apparatus for fixing a tone image to a sheet, comprising: a fixing roller; a pressing roller held in rolling contact with said fixing roller under a predetermined pressure for pressing a sheet with an unfixed toner image carried on a surface thereof against said fixing roller to fix the unfixed toner image to said sheet when said sheet passes in one direction through a rolling contact region between said fixing roller and said pressing roller; a heating roller disposed on one side of said fixing roller opposite to said pressing roller; a heating source disposed in said heating roller for heating said heating roller; and an endless heat transfer belt trained around said heating roller and said fixing roller for transferring heat from said heating source to heat the unfixed toner image on said sheet when said sheet passes through said rolling contact region, characterized by comprising: a control device for carrying out a standby mode control process to keep a surface temperature of said beating roller in a predetermined temperature range when the apparatus is in a standby mode, and carrying out a sheet feed mode control process to keep a surface temperature of said fixing roller in a predetermined temperature range when the apparatus is in a sheet feed mode.

Claim 10

The apparatus according to any Of the preceding claims wherein said control device includes a first detecting device for detecting the surface temperature of said heating roller and a second detecting device for detecting the surface temperature of said fixing roller, said control device including a controller for controlling said heating source based on the surface temperature detected by said first detecting device in said standby mode control process, and controlling said heating source based on the surface temperature detected by said second detecting device in said sheet feed mode control process, and/or further preferably comprising: a second heating source disposed in said heating roller; and a third detecting device for detecting a surface temperature of said pressing rollers, and/or wherein preferably said control device includes a controller for controlling said second heating source based on the surface temperature detected by said third detecting device in said standby mode control process.

Claim 11

An apparatus for fixing a tone image to a sheet, comprising: a fixing roller; a pressing roller held in rolling contact with said fixing roller under a predetermined pressure for pressing a sheet with an unfixed toner image carried on a surface thereof against said fixing roller to fix the unfixed toner image to said sheet when said sheet passes in one direction through a rolling contact region between said fixing roller and said pressing roller; a heating roller disposed on one side of said fixing roller opposite to said pressing roller; a heating source disposed in said heating roller for heating said heating roller; an endless heat transfer belt trained around said heating roller and said fixing roller for transferring heat from said heating source to heat the unfixed toner image on said sheet when said sheet passes through said rolling contact region; and a decision device for deciding whether the apparatus is in a standby mode or a sheet feed mode, characterized by comprising: a control device for carrying out a standby mode control process to keep a surface temperature of said heating roller in a predetermined temperature range when the apparatus is in said standby mode as decided by said decision device, and carrying out a sheet feed mode control process to keep a surface temperature of said fixing roller in a predetermined temperature range when the apparatus is in said sheet feed mode as decided by said decision device.

Claim 12

The apparatus according to any of the preceding claims wherein said decision device includes a determining device for determining that the apparatus is in said sheet feed mode when a sheet teed command is supplied, and that the apparatus is in said standby mode when a sheet feed command is not supplied, and/or wherein preferably said control device includes a first detecting device for detecting the surface temperature of said heating roller and a second detecting device for detecting the surface temperature of said fixing roller, said control device including a controller for controlling said heating source based on the surface temperature detected by said first detecting device in said standby mode control process, and controlling said heating source based on the surface temperature detected by said second detecting device in said sheet feed mode control process, and/or further preferably comprising: a second heating source disposed in said heating roller; and a third detecting device for detecting a surface temperature of said pressing roller, and/or wherein preferably said control device includes a controller for controlling said second heating source based on the surface temperature detected by said third detecting device in said standby mode control process.

Claim 13

An apparatus for fixing a tone image to a sheet, comprising: a fixing roller; a pressing roller; a heating roller; a first heating source; an endless heat transfer belt; a second heating source disposed in said pressing roller for heating said pressing roller; and a control device for energizing said first heating source and said second heating source.