Fixing device and image forming apparatuse using the same

• US 5,911,094 A
• Filed: 09/16/1997
• Issued: 06/08/1999
• Est. Priority Date: 09/17/1996
• Status: Expired due to Term

• Current Assignee: Minolta Corporation Limited (Konica Minolta Inc.)
• Original Assignee: Minolta Corporation Limited (Konica Minolta Inc.)
• Inventors: Tsujimoto, Takahiko
• Primary Examiner(s): Grimley, Arthur T.
• Assistant Examiner(s): TRAN, HOAN H
• Application Number:
  US08/931,160
• Time in Patent Office: 630 Days
• Field of Search: 399/38, 399/44, 399/67, 399/69, 399/130, 399/320, 399/328, 399/330, 219/200, 219/216, 219/469, 219/619, 219/634, 219/643, 219/644, 219/645, 219/650, 219/659, 219/667, 219/671
• US Class Current: 399/69
• CPC Class Codes: G03G 15/2039 with means for controlling the fixing temperature
• CPC Class Codes: G05D 23/1913 delivering a series of pulses
• CPC Class Codes: G05D 23/1917 using digital means
• CPC Class Codes: G05D 23/24 the sensing element having a resistance varying with temperature, e.g. a thermistor

Abstract

An induction heating type fixing device for causing a toner image formed on a sheet to be fixed on the sheet. This fixing device contains a fixing roller formed of a conductive member in a cylindrical shape, a core passed through the interior of the fixing roller and intended to form a closed magnetic circuit, an induction coil wound around the core, a power source for forwarding an alternating circuit to the induction coil, a switch for passing or breaking the alternating current supplied from the power source to the induction coil, an electric current amount detecting coil for detecting the amount of an electric current flowing from the power source to the induction coil, a thermistor for detecting the temperature of the fixing roller, and a CPU for controlling the switch so as to forward an alternating current to the induction coil until the amount of the electric current detected by the electric current amount detecting coil reaches a prescribed amount and, after the amount of the electric current detected by the electric current amount detecting coil has reached the prescribed amount, controlling the switch so as to repeat the passage and the breakage of the alternating current to the induction coil and enable the temperature of the fixing roller to be retained at a predetermined temperature fit for the fixation of the toner image.

Claims

1. An image forming apparatus, comprising:

a fixing roller formed of a conductive member;

a core passing the interior of said fixing roller;

an induction coil wound around said core;

a power source part which supplies a low frequency alternating current to said induction coil;

a switching circuit which passes or breaks the low frequency alternating current supplied from said power source part to said induction coil;

a detector which detects the amount of the low frequency alternating current supplied from said power source part to said induction coil;

a temperature sensor which detects the temperature of said fixing roller; and

a controller which controls said switching circuit so as to supply the low frequency alternating current to said induction coil until the amount of the low frequency alternating current detected by said detector reaches a prescribed amount and, after the amount of the low frequency alternating current detected by said detector has reached said prescribed amount, controls said switching circuit so as to pass or break the low frequency alternating current to said induction coil based on the temperature detected by said temperature sensor.

2. An image-forming apparatus according to claim 1,

wherein said detector detects an induced electromotive force generated by the low frequency alternating current flowing through a wire laid between said power source part and said induction coil.

3. An image-forming apparatus according to claim 1,

wherein said power source part guides an electric current supplied from a commercial power source to said induction coil as the low frequency alternating current.

4. An image-forming apparatus according to claim 1,

wherein said controller interrupts the supply of the low frequency alternating current to said induction coil when the amount of the low frequency alternating current detected by said detector lowers to said prescribed amount.

5. An image-forming apparatus according to claim 1, wherein the low frequency alternating current is in the range of 50 Hz to 60 Hz.

6. An image-forming apparatus according to claim 1,

wherein the low frequency alternating current coil decreases as the temperature of said induction coil increases.

7. An image-forming apparatus according to claim 1,

wherein said detector includes a rectifier for converting a detected alternating current signal into a direct current signal, and said direct current signal is provided to said controller.

8. An image-forming apparatus according to claim 1,

wherein said switching circuit is a solid state relay switch which prevents noise from said power source from entering said controller.

9. An image-forming apparatus, comprising:

a fixing roller formed of a conductive member;

a core passing the interior of said fixing roller;

an induction coil wound around said core;

a power source part which supplies a low frequency alternating current to said induction coil;

a detector which detects the amount of the low frequency alternating current supplied from said power source part to said induction coil; and

a controller which estimates the temperature of said fixing roller based on the amount of the low frequency alternating current detected by said detector and, based on the estimated temperature, predicts the time which elapses until a prescribed temperature is reached.

10. An image-forming apparatus according to claim 9,

wherein said detector detects an induced electromotive force generated by the low frequency alternating current flowing through a wire laid between said power source part and said induction coil.

11. An image-forming apparatus according to claim 9,

wherein said power source part guides an electric current supplied from a commercial power source to said induction coil as the low frequency alternating current.

12. An image-forming apparatus according to claim 9, which further comprises a display part which displays the time predicted by said controller.

13. An image-forming apparatus according to claim 9, wherein the low frequency alternating current is in the range of 50 Hz to 60 Hz.

14. An image-forming apparatus according to claim 9, wherein the low frequency alternating current decreases as the temperature of said induction coil increases.

15. An image-forming apparatus according to claim 9, wherein said detector includes a rectifier for converting a detected alternating current signal into a direct current signal, and said direct current signal is provided to said controller.

17. An image-forming apparatus according to claim 11,

wherein said detector detects an induced electromotive force generated by the low frequency alternating current flowing through a wire laid between said power source part and said induction coil.

16. An image-forming apparatus, comprising:

a fixing roller formed of a conductive member;

a core passing the interior or said fixing roller;

an induction coil wound around said core;

a power source part which supplies a low frequency alternating current to said induction coil;

a switching circuit which passes or breaks the low frequency alternating current supplied from said power source part to said induction coil;

a detector which detects the amount of the low frequency alternating current supplied from said power source part to said induction coil; and

a controller which controls said switching circuit so as to supply the low frequency alternating current to said induction coil until the amount of the low frequency alternating current detected by said detector reaches a prescribed amount and, after the amount of the low frequency alternating current detected by said detector has reached said prescribed amount, controls said switching circuit so as to pass or break the low frequency alternating current to said induction coil based on the amount of the low frequency alternating current detected by said detector.

18. An image-forming apparatus according to claim 16,

wherein said power source part guides an electric current supplied from a commercial power source to said induction coil as the low frequency alternating current.

19. An image-forming apparatus according to claim 16,

wherein said controller interrupts the supply of the low frequency alternating current to said induction coil when the amount of the electric current detected by said detector lowers to said prescribed level.

20. An image-forming apparatus according to claim 16, wherein the low frequency alternating current is in the range of 50 Hz to 60 Hz.

21. An image-forming apparatus according to claim 16, wherein the low frequency alternating current in said induction coil decreases as the temperature of said induction coil increases.

22. An image-forming apparatus according to claim 16, wherein said detector includes a rectifier for converting a detected alternating current signal into a direct current signal, and said direct current signal is provided to said controller.

23. An image-forming apparatus according to claim 16, wherein said switching circuit is a solid state relay switch which prevents noise from said power source from entering said controller.

24. An image-forming apparatus, comprising:

a fixing roller formed of a conductive member;

a core passing the interior of said fixing roller;

an induction coil wound around said core;

a power source part which supplies a low frequency alternating current to said induction coil;

a controller which effects such a control as to elevate the temperature of said fixing roller to a prescribed temperature and, at the same time, retain said prescribed temperature by supplying the low frequency alternating current from said power source part to said induction coil; and

a detector disposed on a wire for supplying the low frequency alternating current from said power source part to said induction coil and adapted to detect the fact that a current is flowing through said wire.

25. An image-forming apparatus according to claim 24,

wherein said detector detects an induced electromotive force generated by the low frequency alternating current flowing through the wire laid between said power source part and said induction coil.

26. An image-forming apparatus according to claim 24,

wherein said power source part guides the low frequency alternating current supplied from a commercial power source to said induction coil.

27. An image-forming apparatus according to claim 24,

wherein said controller interrupts the supply of the low frequency alternating current to said induction coil when the amount of the low frequency alternating current detected by said detector lowers to said prescribed level.

28. An image-forming apparatus according to claim 24,

wherein a switching circuit for passing or breaking the low frequency alternating current supplied from said power source part to said induction coil is additionally provided and said controller decides whether said induction coil and said switching circuit are functioning normally or not based on the outcome of the detection made by said detector and a signal from the controller used for controlling said switching circuit.

29. An image-forming apparatus according to claim 24, wherein the low frequency alternating current is in the range of 50 Hz to 60 Hz.

30. An image-forming apparatus according to claim 24, wherein the low frequency alternating current in said induction coil decreases as the temperature of said induction coil increases.

31. An image-forming apparatus according to claim 24,

wherein said detector includes a rectifier for converting a detected alternating current signal into a direct current signal, and said direct current signal is provided to said controller.

32. An image-forming apparatus, comprising:

a fixing roller formed of a conductive member;

a core passing the interior of said fixing roller;

an induction coil wound around said core;

a power source part which supplies a low frequency alternating current to said induction coil;

a first detector disposed on a wire which supplies the low frequency alternating current from said power source part to said induction coil and is adapted to detect the fact that an electric current is flowing through said wire;

a second detector which detects the open-close state of a door of said image-forming apparatus; and

a controller which effects such a control as to interrupt the supply of the low frequency alternating current to said induction coil when said door is opened while the flow of the the low frequency alternating current through said wire is present in accordance with the outcome of the detection of said first detector and said second detector, and which estimates the temperature of said fixing roller based on the amount of the low frequency alternating current detected by said first detector and, based on the estimated temperature, predicts the time which elapses until a prescribed temperature is reached.

33. A fixing device, comprising:

a fixing roller formed of a conductive member;

a core passing the interior of said fixing roller;

an induction coil wound around said core and supplied with a low frequency alternating current from a power source;

a switching circuit which passes or breaks the low frequency alternating current supplied to said induction coil;

a detector which detects the amount of the low frequency alternating current supplied to said induction coil,

a temperature sensor which detects the temperature of said fixing roller; and

a controller which controls said switching circuit so as to supply the low frequency alternating current to said induction coil until the amount of the low frequency alternating current detected by said detector reaches a prescribed amount and, after the amount of the low frequency alternating current detected by said detector has reached said prescribed amount, controls said switching circuit so as to pass or break the low frequency alternating current to said induction coil based on the temperature detected by said temperature sensor.

34. A fixing device, comprising:

a fixing roller formed of a conductive member;

a core passing the interior of said fixing roller;

an induction coil wound around said core and supplied with a low frequency alternating current from a power source;

a detector which detects the amount of the low frequency alternating current supplied to said induction coil; and

a controller which estimates the temperature of said fixing roller based on the amount of the low frequency alternating current detected by said detector and, based on the estimated temperature, predicting the time which elapses until the prescribed temperature is reached.

35. A fixing device, comprising

a fixing roller formed of a conductive member;

a core passing the interior of said fixing roller;

an induction coil wound around said core and supplied with a low frequency alternating current from a power source;

a switching circuit which passes or breaks the low frequency alternating current supplied to said induction coil;

a detector which detects the amount of the low frequency alternating current supplied to said induction coil; and

a controller which controls said switching circuit so as to supply the low frequency alternating current to said induction coil until the amount of the low frequency alternating current detected by said detector reaches a prescribed amount and, after the amount of the low frequency alternating current detected by said detector has reached said prescribed amount, controls said switching circuit so as to pass or break the low frequency alternating current to said induction coil based on the amount of the low frequency alternating current detected by said detector.

36. A fixing device, comprising:

a fixing roller formed of a conductive member;

a core passing the interior of said fixing roller;

an induction coil wound around said core and supplied with a low frequency alternating current from a power source;

a controller which effects such a control as to elevate the temperature of said fixing roller to a prescribed temperature and retain said prescribed temperature by supplying the low frequency alternating current to said induction coil; and

a detector disposed on a wire for supplying the low frequency alternating current from said power source part to said induction coil and adapted to detect the fact that a current is flowing through said wire.

37. An fixing device, comprising:

a fixing roller formed of a conductive member;

a core passing the interior of said fixing roller;

an induction coil wound around said core and supplied with a low frequency alternating current from a power source;

a first detector disposed on a wire supplying the low frequency alternating current to said induction coil and adapted to detect the fact that an electric current is flowing through said wire;

a second detector which detects the open-close state of a door of a housing accommodating said fixing device; and

a controller which effects such a control as to interrupt the supply of the low frequency alternating current to said induction coil when said door is opened while the flow of the low frequency alternating current through said wire is present in accordance with the outcome of the detection of said first detector and said second detector, and which estimates the temperature of said fixing roller based on the amount of the low frequency alternating current detected by said first detector and, based on the estimated temperature, predicts the time which elapses until a prescribed temperature is reached.

38. A fixing apparatus comprising:

an induction heating device using a low frequency alternating current from a power source;

a switching circuit which passes or breaks the low frequency alternating current supplied to said induction heating device;

a detector which detects the amount of the low frequency alternating current supplied to said induction heating device; and

a controller which controls said switching circuit so as to supply the low frequency alternating current to said induction heating device until the amount of the low frequency alternating current detected by said detector reaches a prescribed amount and, after the amount of the low frequency alternating current detected by said detector has reached said prescribed amount, controls said switching circuit so as to pass or break the low frequency alternating current to said induction heating device based on the amount of the low frequency alternating current detected by said detector.