Heating element, fixing device, and image forming apparatus

Abstract

To achieve miniaturization, improve printing productivity, and suppress flicker. [Solution] The heating element comprises a substrate 54a, a heating element 54b1a located at one end of the substrate 54a in the short direction Ds, a heating element 54b1b located at the other end of the substrate 54a in the short direction Ds and connected in parallel with the heating element 54b1a, and a heating element 54b3 located between the heating elements 54b1a and 54b1b in the short direction Ds. The combined electrical resistance value R1 of the heating elements 54b1a and 54b1b is smaller than the electrical resistance value R2 of the heating element 54b3. The heating element 54b3 has a heating element 54b3a that is shorter than the length of the heating elements 54b1a and 54b1b in the longitudinal direction Dl of the substrate 54a, and heating elements 54b3b and 54b3c that have a smaller electrical resistance value than the heating element 54b3a. The heating elements are connected in series in the order of heating element 54b3b, heating element 54b3a, and heating element 54b3c.

Claims

[Claim 1] circuit board and A first heating element is disposed at one end of the substrate in the short direction, A second heating element is positioned at the other end of the substrate in the shorter direction and connected in parallel with the first heating element, A third heating element is disposed between the first heating element and the second heating element in the shorter direction, Equipped with, The combined electrical resistance R1 of the first heating element and the second heating element is less than the electrical resistance R2 of the third heating element. The third heating element has a first portion shorter than the lengths of the first and second heating elements in the longitudinal direction of the substrate, and a second portion and a third portion having a lower electrical resistance than the first portion, and the second portion, the first portion, and the third portion are connected in series in that order. A heating element characterized by the following features. [Claim 2] The third heating element is longer than the first heating element in the longitudinal direction. The heating element according to feature 1. [Claim 3] A fixing device for fixing a toner image on a recording material, A heating element according to claim 1 or claim 2, A switching means for switching between supplying power to the first heating element and the second heating element, or supplying power to the third heating element, A control means for controlling the switching means, Equipped with, The control means controls the switching means such that the frequency of use of the third heating element increases as the amount of heat stored in the fixing device increases. A fixing device characterized by the following features. [Claim 4] The control means changes the ratio of the time for supplying power to the first and second heating elements to the time for supplying power to the third heating element according to the amount of heat stored. The fixing device according to feature 3. [Claim 5] The control means changes the sum of the preceding term and the succeeding term of the ratio according to the amount of heat stored. The fixing device according to feature 4. [Claim 6] The film heated by the aforementioned heating element, A pressure roller that forms a nip portion together with the aforementioned film, Equipped with, The heating element is positioned in the internal space of the film, and the film is held between the heating element and the pressure roller. The toner image on the recording material is heated at the nip portion via the film. The fixing device according to feature 3. [Claim 7] Image forming means for forming a toner image on a recording material, A fixing apparatus according to claim 3 for fixing a toner image formed by the image forming means, Equipped with, An image forming apparatus characterized by the following:

Images