# US 2025/0085653 A1 · Fixing device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2025/0085653 A1 - Document ID: US20250085653A1 - Status: Published application - Kind: A1 - Application number: 18/464,889 - Filed: 2023-09-11 - Published: 2025-03-13 - Earliest claimed: 2023-09-11 - Assignees: Toshiba Tec Kabushiki Kaisha - Applicants: Toshiba Tec Kabushiki Kaisha - Inventors: Hiroshi OTA - Web page: https://patentgrep.com/patent/US20250085653A1 ## CPC - G03G 15/2064: {combined with pressure} - G03G 15/2039: {with means for controlling the fixing temperature} - G03G 15/205: {specially for the mode of operation, e.g. standby, warming-up, error (G03G15/2046 takes precedence)} - G03G 2215/2035: the fixing nip having a stationary belt support member opposing a pressure member - G03G: ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY ## Abstract According to one embodiment, a fixing device includes a fuser including a fixing member with a surface to contact a printable medium and a heat source for heating the fixing member. A temperature sensor is provided having a sensing part that contacts the surface of the fixing member. A heater control circuit is configured to estimate a temperature of the surface of the fixing member based on a temperature measured by the sensing part of the temperature sensor. A memory is provided for storing estimated temperature values obtained over a prior time period by the heater control circuit. A controller is configured to determine whether there is an abnormality in the fixing device based on a difference between a maximum value and a minimum value of the estimated temperature values stored in the memory. ## Claims ### Claim 1 A fixing device, comprising: a fuser including a fixing member with a surface to contact a printable medium and a heat source for heating the fixing member; a temperature sensor with a sensing part that contacts the surface of the fixing member; a heater control circuit configured to estimate a temperature of the surface of the fixing member based on a temperature measured by the sensing part of the temperature sensor; a memory for storing estimated temperature values obtained over a prior time period by the heater control circuit; and a controller configured to determine whether there is an abnormality in the fixing device based on a difference between a maximum value and a minimum value of the estimated temperature values stored in the memory. ### Claim 2 (depends on 1) The fixing device according to claim 1, wherein the controller identifies whether there is an abnormality in the temperature sensor based on the difference between the maximum value and the minimum value of the estimated temperature values stored in the memory. ### Claim 3 (depends on 1) The fixing device according to claim 1, wherein the controller identifies whether there is a variation in input power input to the heat source based on the difference between the maximum value and the minimum value of the estimated temperature values stored in the memory. ### Claim 4 (depends on 1) The fixing device according to claim 1, wherein the controller identifies a temperature increase value for the fixing member relative to the temperature sensed by the temperature sensor based on the difference between the maximum value and the minimum value of the estimated temperature values stored in the memory. ### Claim 5 (depends on 1) The fixing device according to claim 1, wherein the controller selects estimated temperature values stored over a time period of predetermined length from the memory. ### Claim 6 (depends on 1) The fixing device according to claim 1, wherein the controller is further configured to output an abnormality determination result to an external device. ### Claim 7 (depends on 1) The fixing device according to claim 1, wherein the heater control circuit estimates the temperature of the surface using a RC thermal circuit. ### Claim 8 (depends on 1) The fixing device according to claim 1, wherein the heater control circuit using a weighted-average-estimation method to estimate the temperature of the surface. ### Claim 9 A fixing device, comprising: a fuser including a fixing member with a surface to contact a printable medium and a heat source for heating the fixing member; a first temperature sensor with a first sensing part that contacts a first region of the surface of the fixing member; a second temperature sensor with a second sensing part that contacts a second region of the surface of the fixing member; a heater control circuit configured to estimate a temperature of the surface of the fixing member based on a temperature measured by the first or second temperature sensors; a memory for storing estimated temperature values obtained over a prior time period by the heater control circuit; and a controller configured to determine whether there is an abnormality in the fixing device based on a difference between a maximum value and a minimum value of the estimated temperature values stored in the memory. ### Claim 10 (depends on 9) The fixing device according to claim 9, wherein the heat control circuit generates a first estimation value obtained by estimating the temperature of the first region and a second estimation value obtained by estimating the temperature of the second region, and the controller identifies whether there is an abnormality in the fixing device based on a difference between a maximum value and a minimum value of a plurality of first estimation values stored in the memory or difference between a maximum value and a minimum value of a plurality of second estimation values stored in the memory. ### Claim 11 (depends on 10) The fixing device according to claim 10, wherein the controller identifies whether there is an abnormality in the first temperature sensor based on the difference between the maximum value and the minimum value of the plurality of first estimation values stored in the memory and whether there is an abnormality in the second temperature sensor based on the difference between the maximum value and the minimum value of the plurality of second estimation values stored in the memory. ### Claim 12 (depends on 11) The fixing device according to claim 11, wherein the heat source includes a first heating component that heats the first region and a second heating component that heats the second region, and the controller identifies whether there is a variation in input power input to the first heating component based on the difference between the maximum value and the minimum value of the plurality of first estimation values stored in the memory and identifies whether there is a variation in input power input to the second heating component based on the difference between the maximum value and the minimum value of the plurality of second estimation values stored in the memory. ### Claim 13 (depends on 11) The fixing device according to claim 11, wherein the controller determines a temperature rise value for the first region relative to the temperature sensed by the first temperature sensor based on the difference between the maximum value and the minimum value of the plurality of first estimation values stored in the memory and determines a temperature rise value for the second region relative to the temperature sensed by the second temperature sensor based on the difference between the maximum value and the minimum value of the plurality of second estimation values stored in the memory. ### Claim 14 (depends on 9) The fixing device according to claim 9, wherein the controller is configured to output an abnormality determination result to an external device. ### Claim 15 (depends on 9) The fixing device according to claim 9, wherein the heat source is halogen lamp. ### Claim 16 (depends on 9) The fixing device according to claim 9, wherein the heat source is a plurality of resistance heating elements. ### Claim 17 An image forming apparatus, comprising: an image forming unit configured to form a toner image on a printable medium; a fuser configured to receive the printable medium from the image forming unit and fix the toner image to the printable medium, the fuser including: a fixing member with a surface to contact the printable medium and a heat source for heating the fixing member, a first temperature sensor with a first sensing part that contacts a first region of the surface of the fixing member, a second temperature sensor with a second sensing part that contacts a second region of the surface of the fixing member, a heater control circuit configured to estimate a temperature of the surface of the fixing member based on a temperature measured by the first or second temperature sensors, and a memory for storing estimated temperature values obtained over a prior time period by the heater control circuit; and a controller configured to determine whether there is an abnormality based on a difference between a maximum value and a minimum value in the estimated temperature values stored in the memory. ### Claim 18 (depends on 17) The image forming apparatus according to claim 17, wherein the heat control circuit generates a first estimation value obtained by estimating the temperature of the first region and a second estimation value obtained by estimating the temperature of the second region, and the controller identifies whether there is an abnormality based on a difference between a maximum value and a minimum value of a plurality of first estimation values stored in the memory or difference between a maximum value and a minimum value of a plurality of second estimation values stored in the memory. ### Claim 19 (depends on 18) The image forming apparatus according to claim 18, wherein the controller identifies whether there is an abnormality in the first temperature sensor based on the difference between the maximum value and the minimum value of the plurality of first estimation values stored in the memory and whether there is an abnormality in the second temperature sensor based on the difference between the maximum value and the minimum value of the plurality of second estimation values stored in the memory. ### Claim 20 (depends on 19) The image forming apparatus according to claim 19, wherein the heat source includes a first heating component that heats the first region and a second heating component that heats the second region, and the controller identifies whether there is a variation in input power input to the first heating component based on the difference between the maximum value and the minimum value of the plurality of first estimation values stored in the memory and identifies whether there is a variation in input power input to the second heating component based on the difference between the maximum value and the minimum value of the plurality of second estimation values stored in the memory.