Image forming apparatus and control method
An image forming apparatus includes a fixing device and a control unit. The fixing device includes a heating resistor formed of a positive temperature coefficient material. The control unit energizes the heating resistor with a first energization amount if a temperature of the heating resistor is lower than a predetermined temperature, and energizes the heating resistor with a second energization amount that is higher than the first energization amount if the temperature of the heating resistor is higher than the predetermined temperature.
1. An image forming apparatus comprising:
a fixing device comprising a heating resistor formed of a positive temperature coefficient material; and
a control unit configured to energize the heating resistor with a first energization amount if a temperature of the heating resistor is lower than a predetermined temperature, and energize the heating resistor with a second energization amount that is higher than the first energization amount if the temperature of the heating resistor is higher than the predetermined temperature.
2. The apparatus according to claim 1 , wherein
the control unit does not execute an operation according to a state of the image forming apparatus while energizing the heating resistor with the first energization amount when the temperature of the heating resistor is lower than the predetermined temperature, and energizes the heating resistor with the second energization amount and executes an operation according to the state of the image forming apparatus when the temperature of the heating resistor is higher than the predetermined temperature.
3. The apparatus according to claim 1 , wherein
the control unit determines the predetermined temperature according to a state of the image forming apparatus.
4. The apparatus according to claim 1 , wherein
the predetermined temperature is predetermined according to a maximum value of power that is used by the heating resistor according to a state of the image forming apparatus and the characteristics of the heating resistor.
5. The apparatus according to claim 1 , wherein the first energization amount increases as the temperature of the heating resistor increases.
6. The apparatus according to claim 1 , wherein the heating resistor comprises a plurality of heating resistors arranged in a longitudinal direction.
7. The apparatus according to claim 6 , wherein the control unit is configured to begin energizing heating resistors at ends of the plurality of heating resistors and then towards a center of the plurality of heating resistors.
8. The apparatus according to claim 6 , wherein the control unit is configured to begin energizing a heating resistor at a center of the plurality of heating resistors and then heating resistors towards ends of the plurality of heating resistors.
9. The apparatus according to claim 6 , wherein the control unit is configured to begin energizing a heating resistor of the plurality of heating resistors that has a lowest temperature and then heating resistors having higher temperatures in increasing order of their temperatures.
10. The apparatus according to claim 6 , wherein the control unit is configured to energize each heating resistor equally.
11. A control method performed by a control unit of an image forming apparatus including a fixing device comprising a heating resistor formed of a positive temperature coefficient material, the method comprising:
energizing the heating resistor with a first energization amount if a temperature of the heating resistor is lower than a predetermined temperature, and energizing the heating resistor with a second energization amount that is higher than the first energization amount if the temperature of the heating resistor is higher than the predetermined temperature.
12. The method according to claim 11 , further comprising:
not executing an operation according to a state of the image forming apparatus while energizing the heating resistor with the first energization amount, and executing an operation according to the state of the image forming apparatus while energizing the heating resistor with the second energization amount when the temperature of the heating resistor is higher than the predetermined temperature.
13. The method according to claim 11 , further comprising:
determining the predetermined temperature according to a state of the image forming apparatus.
14. The method according to claim 11 , wherein
the predetermined temperature is predetermined according to a maximum value of power that is used by the heating resistor according to a state of the image forming apparatus and the characteristics of the heating resistor.
15. The method according to claim 11 , wherein the first energization amount increases as the temperature of the heating resistor increases.
16. The method according to claim 11 , wherein the heating resistor comprises a plurality of heating resistors arranged in a longitudinal direction.
17. The method according to claim 16 , further comprising:
energizing heating resistors at ends of the plurality of heating resistors and then towards a center of the plurality of heating resistors.
18. The method according to claim 16 , further comprising:
energizing a heating resistor at a center of the plurality of heating resistors and then heating resistors towards ends of the plurality of heating resistors.
19. The method according to claim 16 , further comprising:
energizing a heating resistor of the plurality of heating resistors that has a lowest temperature and then heating resistors having higher temperatures in increasing order of their temperatures.
20. The method according to claim 16 , further comprising:
energizing each heating resistor equally.