JP2692988B2 - Fixing device - Google Patents

Description

The present invention relates to a fixing device used in electrophotographic devices, electrostatic recording devices, and the like, and more particularly, to a fixing device in which a temperature detecting element is arranged on a heating roll in a non-contact manner. Regarding

[Prior Art] A fixing device using a heat roller heated by a heater is widely used in an image forming apparatus such as a copying machine or a laser printer.

In such a fixing device, a temperature detection element such as a thermistor for maintaining the surface temperature of the heat roller at a predetermined temperature, a temperature fuse for shutting off the energization path to the heater when the temperature of the heat roller abnormally rises, or a thermoswitch. Is in contact with the surface of the heat roller.

As a result, contact flaws occur on the fixing roller, causing white lines and
Problems such as black streaks and improper fixing may occur.

Therefore, it is conceivable to bring the temperature detecting member into contact with the fixing roller outside the image area, which is the passage area of the recording material, but it is impossible to detect the temperature in the image area and the fixing device becomes large, Recently, a method has been considered in which the temperature detection member is brought into contact with the fixing roller in the image area in a noncontact manner.

However, especially in the case of a thermoswitch that prevents abnormal temperature rise, due to the limit of its responsiveness, unless the thermoswitch is brought closer to the fixing roller by about 1 mm or less, there is a risk of fire before the thermoswitch operates. Therefore, management of the proximity gap amount is an important technical point.

As shown in FIG. 3, conventionally, a structure is adopted in which a thermoswitch is attached to a pair of frames supporting the fixing roller so as to be close to the fixing roller. In some cases, the amount of jig is adjusted.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional example, there are many components such as the fixing roller, the heat insulating member, the bearing, the side plate, the top plate, and the thermoswitch even if the proximity gap amount is adjusted by a jig. This is an extremely difficult problem to secure due to variations and changes in the proximity gap amount due to stacking such as deformation and thermal expansion due to external force and eccentric movement of the fixing roller.

Further, in the configuration requiring jig adjustment, the assembly work becomes complicated and the cost becomes high.

[Means for Solving the Problems] In order to solve the above problems, the present invention is directed to a heating roller heated by a heating source, a temperature detecting element for detecting the temperature of the heating roller, and holding the temperature detecting element. A holding member having a contact portion, and a pressing member for pressing the holding member toward the heating roller, wherein the pressing member causes the contact portion of the holding member to contact the heating roller. In a fixing device in which a temperature detecting element is maintained in a non-contact state with the heating roller and heats and fixes an unfixed image on a recording material by heat from the heating roller, the temperature detecting element is in an image area of the heating roller. Is provided in
The abutting portion of the holding member abuts only on the outside of the image area of the heating roller.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

Note that members that perform the same function are denoted by the same reference numerals.

1 and 2 are a perspective view and a sectional view of an embodiment of the present invention.

In the figure, 1 is a fixing roller, which is a heat roller having a heater H inside, 2 is a pressure roller that rotates in pressure contact with the fixing roller 1, and 3 is a heater H that detects an abnormal temperature rise of the fixing roller. Switch that shuts off the energization path to 4
Is a holding member that holds the thermoswitch 3, 5 is a contact portion of the holding member with the fixing roller 1, 6 is a shaft, 7 is a cleaning member that removes offset toner and paper dust on the surface of the fixing roller of the holding member, and 8 is A heat insulating member that protects the bearing from heat of the fixing roller, 9 is a bearing, 10 is a side plate, 11 is a top plate, 12 is a pressing spring, 13 is an inlet guide, 14 is a bottom plate, A is an image area, B is a cleaning area, and X is a cleaning area. Is the proximity gap amount. As is apparent from FIG. 1, the thermoswitch 3 is provided in the image area A.

The contact portion 5 of the holding member 4 that holds the thermoswitch 3 is in contact with the fixing roller 1, especially outside the image area A, which is the passage area of the recording material of the maximum size of the fixing roller 1.

The holding member 4 has a rotation stopping shaft 6 so as not to rotate on the outer peripheral surface of the fixing roller 1. The shaft 6 is a pressing member.
A force is applied in the direction of approaching the fixing roller 1 by 12, so that a close gap between the thermoswitch 3 and the fixing roller 1 is formed.

Further, since the thermoswitch 3 is near the contact point between the holding member 4 and the fixing roller 1, the proximity gap amount is formed by the contact portion 5. Therefore, the gap amount X is hardly affected by the accuracy of the gap between the shaft 6 and the fixing roller 1. Further, if the holding member 4, the contact portion 5 and the shaft 6 are integrally formed, the accuracy can be more effectively improved.

Further, the cleaning member 7 has the abutting portion 5 at the fixing roller 1.
The area which is in contact with is cleaned and has a width of B in FIG.

Further, even if the fixing roller 1 eccentrically moves or thermally expands, the contact portion 4 maintains the proximity gap amount between the surface of the fixing roller 1 and the thermoswitch 3, so that the proximity gap amount does not change.

In this embodiment, the holding portion 41, which is a single component of the holding member 4 that actually holds the thermoswitch 3, is extended to the non-sheet passing area, and the holding portion 41 has the contact portion 5.

 Therefore, the accuracy of the gap amount is very high.

In this embodiment, in order to manage the proximity gap amount, it is sufficient to manage the dimensional accuracy of only the holding member 4, the deformation during use, and the thermal expansion, and in terms of checking the minimum number of parts, low man-hours and low cost are required. Become. Further, it is not necessary to assemble with a jig, and the number of assembling steps can be reduced.

In addition, even if eccentric movement or thermal expansion of the fixing roller occurs,
Since the proximity gap amount is not affected at all, the proximity gap amount can be maintained accurately.

FIG. 4 shows another embodiment of the present invention. 17 is a holding member 4
And a dedicated cleaning member for the contact member 5. C is a cleaning area by a cleaning member that cleans the image area.

When the fixing roller 1 is rotating, the dedicated cleaning member 17 cleans the portion where the holding member 4 and the contact member 5 are in contact with the fixing roller 1 in the non-image area. Since the non-image area is less dirty than the image area, it is sufficient to install the dedicated cleaning member 17 fixed to the fixing device, not by the cleaning member 7 that is regularly replaced.

Therefore, the cleaning member can be used for a very long period of time, and the cleaning member 7 as a fixing replacement part can be downsized and the cost reduction device can be downsized.

5 (a) and 5 (b) are sectional views and perspective views showing another embodiment of the present invention, in which 1 is a fixing roller, 3 is a thermoswitch, 4 is a holding member, and 15 is a constant temperature due to temperature change. Then, a metal plate (hereinafter referred to as a bimetal) that is deformed and turns off the thermoswitch, and 16 is a cap that supports the bimetal 15.

The general-purpose thermoswitch has a structure in which the bimetal 15 is supported by the cap 16. Therefore, the cap 16 is abutted and held by the holding member 4 that is in contact with the fixing roller 1.

As a result, it is possible to more accurately secure the proximity gap amount between the bimetal 15 and the fixing roller 1.

Although the present embodiment has described the thermoswitch as the temperature detecting member, the present invention can be applied to a thermal fuse, a thermistor, and the like.

EFFECTS OF THE INVENTION According to the present invention as described above, the gap amount between the temperature detecting member and the heat roller can be secured with a simple structure, and the number of assembling steps can be reduced and the effects of the roller eccentricity and the thermal expansion can be prevented. it can.

Also, even if the fixing device is disassembled, the gap amount does not change,
Maintenance is also easy.

[Brief description of the drawings]

1 is a perspective view of a fixing device embodying the present invention. FIG. 2 is a sectional view of FIG. 1 embodiment. FIG. 3 is a front view of a conventional example. FIG. 4 is a perspective view of another embodiment of the present invention. 5 (a) and (b) are cross-sectional views and perspective views of another embodiment of the present invention, in which 1 is a fixing roller, 2 is a pressure roller, 3 is a thermoswitch, 4 is a holding member, 5 is a contact portion, and 6 is an axis. 7 is the cleaning member A is the image area X is the proximity gap amount

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Masato Otsuka Inventor Masato Otsuka 3-30-2 Shimomaruko, Canon Inc. (72) Inventor Takahiro Kurida 3-30-2 Shimomaruko Ota-ku, Tokyo Canon Inc. Incorporated (72) Inventor Tadashi Yagi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Tsuyoshi Waratani 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. ( 72) Inventor Miro Tsuchiya 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hiroshi Yukimachi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Invention Person Hiroaki Miyake 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) Reference JP-A-55-79477 (JP, A) JP-A-56-165174 ( P, A) JitsuHiraku Akira 61-106961 (JP, U) JitsuHiraku Akira 63-45568 (JP, U)

Claims (2)

(57) [Claims] 1. A heating roller heated by a heating source, a temperature detecting element for detecting the temperature of the heating roller, a holding member for holding the temperature detecting element and having an abutting portion, and the holding member. A pressing member for pressing the heating roller side, the contact portion of the holding member contacts the heating roller by the pressing member, and the temperature detection element is in a non-contact state with the heating roller. In a fixing device that is maintained and heat-fixes an unfixed image on a recording material by heat from the heating roller, the temperature detection element is provided in an image area of the heating roller, and an abutting portion of the holding member is the heating portion. A fixing device characterized in that it comes into contact only with the outside of the image area of the roller. 2. The temperature detecting element is a thermoswitch or a temperature fuse for blocking the energization of the heating source when the temperature of the heating roller is abnormally elevated, or a thermistor for maintaining the temperature of the heating roller at a predetermined temperature. The fixing device according to claim 1, wherein