US 6,087,641 A · Fixing device with induction heating unit

Abstract

A fixing device is provided, which can maintain good fixing properties, irrespective of the kind of a material on which a developer image is to be fixed and a temperature condition of a pressure roller. In a rotary contact region between a heat supply medium and the pressure roller, pressure and heat are applied to the material, thereby fixing the developer image on the material. The heat supply medium includes a metallic body for induction heating, which is provided with a magnetic field to produce an eddy current. The heat supply medium contains a magnetic field generating unit. The magnetic field generating unit includes a core provided with a coil. The core is situated near the metallic body of the heat supply medium such that a distance between a position closest to the metallic body and an end portion of the core is less than a distance between magnetic force line guiding portions provided on the core. The coil is wound such that the coil is not closer to the metallic body than a region surrounded by the magnetic force line guiding portions in a direction of cross section of the core.

Claims16

Dependent claims

A fixing device comprising:

a first rotary contact member formed of an electrically conductive material and rotated in a predetermined direction;
a second rotary contact member put in contact with the first rotary contact member under a predetermined pressure, a rotary contact region for fixing a developer image on a material on which the developer image is to be formed, being formed between the first rotary contact member and the second rotary contact member;
an oscillator that generates pulses according to a kind of the material;
and
an induction heating unit that heats the first rotary contact member to fix the developer image on the material according to the number of pulses supplied from the oscillator.

2 more elements

A fixing device comprising:

a first rotary contact member formed of an electrically conductive material and rotated in a predetermined direction;
a second rotary contact member put in contact with the first rotary contact member under a predetermined pressure, a rotary contact region for fixing a developer image on a material on which the developer image is to be formed, being formed between the first rotary contact member and the second rotary contact member;
an oscillator for generating pulses according to a kind of the material;
and
an induction heating unit that heats the first rotary contact member to fix the developer image on the material according to the number of pulses supplied from the oscillator, wherein the induction heating unit includes a coil supplied with a current of a predetermined magnitude and a magnetic field generating unit having a core having two end portions for guiding magnetic force lines produced when the current has been supplied to the coil,
wherein both end portions of the core of the magnetic field generating unit are bent toward the rotary contact member located close to the core, thus constituting magnetic force line guiding portions, and
wherein a distance between bent portions of the magnetic force line guiding portions is greater than a distance between the rotary contact member and those portions of the end portions of the magnetic force line guiding portions, which are closest to the rotary contact member.

4 more elements

Dependencies are inferred from the claim text.

Fixing device with induction heating unit

Life of this patent

Fixing device with induction heating unit

Life of this patent

Abstract

Claims16