JPH07109530B2 - Fixing device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for fixing an unfixed image formed on a sheet material between a pair of rollers, and more particularly to guiding a sheet material between the pair of rollers. The present invention relates to a device including a guide member.

(Prior Art and Problems) Conventionally, as a fixing device used in an image forming apparatus such as a copying machine, a fixing type of a fixing roller and a pressure roller which is pressed and rotated below the fixing roller, and further fixing There is known a heat pressure type in which a heater is arranged in a roller. In the fixing device as described above, the sheet material carrying the unfixed image is passed through the nip portion formed between the fixing roller and the pressure roller to fix the image on the sheet material. Therefore, in order to prevent the offset phenomenon of the developer at the time of fixing, a roller having a surface layer of Teflon (registered trademark) or the like is usually used for the fixing roller, and an elastic layer of silicone rubber or the like is used for the pressure roller. Many use rollers having. However,
As described above, when the surface of the pressure roller is an elastic body, if the front end of the sheet material toward the nip portion comes into contact with the pressure roller before reaching the nip portion, the front end of the sheet material slides on the surface. A situation in which the image does not reach the nip portion and is stagnated at an intermediate position, or a situation in which an image being carried is disturbed by an impact at the time of contact or the like occurs. In particular, when the sheet material is curled downward at the front end toward the nip, the above-mentioned problems are prominent, and the front end of the sheet material is bent or wrinkled, and the impact at the time of contact reaches the rear end of the sheet material. If it spreads, problems such as image distortion will be significant.

Therefore, in order to reliably guide the conventional sheet material to the nip part,
A plate-shaped guide member for guiding the bottom portion of the sheet material is provided, and the inclination and position of the guide member are appropriately set to cope with the downward curled sheet material. For example, there is a device shown in FIGS. 6 (A) and 6 (B). The apparatus of FIG. 6 (A) uses a guide member so that the sheet material can be pushed up as it approaches the nip portion to cope with the downward curl.
30 is tilted and fixed to the support member 30A. In the apparatus shown in FIG. 6B, the height position is further taken into consideration, and the guide member 30 is arranged at a position higher than the height position of the nip portion.

However, it is difficult for the above device to judge the setting conditions of the guide member 30, and if the judgment of the angle of inclination and the height position is incorrect,
As shown in FIG. 3A, the downward curl cannot be dealt with, and the sheet material stays in contact with the pressure roller 2 and remains stagnant. Further, if the guide member 30 is set in consideration of only the downward curl, there arises a problem that the sheet material having the upward curl cannot be dealt with, as shown in FIG. 6 (B). Thus, it has been difficult to solve the problem of curling of the front end of the sheet material.

(Means for Solving Problems) The present invention provides a fixing device capable of coping with the curl of the front end portion of the sheet material, which cannot be solved by the conventional fixing device as described above, regardless of the direction thereof. That is also the purpose.

To achieve the above object, the present invention provides a fixing roller, a pressure roller that presses against the fixing roller to form a nip portion, a guide member that guides the movement of the recording material at the entrance side of the nip portion, A fixing device that has a guide member and an auxiliary guide plate that is provided between the nip portion and guides the recording material to the nip portion, and nips and conveys the recording material bearing an unfixed image in the nip portion to perform fixing. The auxiliary guide plate is rotatable around an axis parallel to the rotation axis of the pressure roller as a fulcrum, and the tip end of the auxiliary guide plate on the rotation side contacts the pressure roller. Composed.

(Embodiment) An embodiment of the present invention will be described below with reference to the attached FIGS. 1 to 5.

In FIG. 1, reference numeral 1 is a fixing roller
A pressure roller 2 is pressed against the roller from below with a predetermined pressure, and a nip portion N is formed between the rollers 1 and 2.

A guide plate 3 as a guide member is arranged at a predetermined distance from the nip portion N in order to guide the sheet material P carrying the unfixed image to the nip portion N. In order to guide the bottom surface of the sheet material P and feed it to the nip portion N, the guide plate 3 is inclined so as to sequentially push up the sheet material P toward the nip portion N, and is fixedly mounted on the support member 3A. Has been done. Further, the end portion of the guide plate 3 near the nip portion N is positioned so that the sheet material P having no curl is fed to the height of the nip portion N or to a height slightly closer to the fixing roller 1 than the nip portion. It is set.

Further, an auxiliary plate 4 as an auxiliary guide plate is arranged from a position below the guide plate 3 toward the nip portion N. The auxiliary plate 4 contacts the pressure roller 2 with a sheet material whose front end has a downward curl in the space from the end of the guide plate 3 near the nip N to the nip N. It is arranged so that the front end is reliably fed to the nip portion N. The auxiliary plate 4 is disposed so as to be close to or in contact with the pressure roller 2 and extend in the longitudinal direction of the pressure roller 2. The end portion on the side of the nip portion N should be as close to the nip portion N as possible. It is preferably made of a thin plate member. As a member used for the auxiliary plate 4, a certain smoothness is required on the surface since the end portion of the sheet material P is slid on the surface and guided to the nip portion N, but the type of the member does not matter. A thin plate metal or a flexible resin film can be used. For example, a thin stainless plate having a smooth surface can be used, or a sheet of Teflon or the like may be attached to further improve the smoothness of the surface. Further, instead of the sheet material, a material such as Teflon coating may be applied.

The auxiliary plate 4 is of a type in which its longitudinal end is fixed to a frame (not shown) as shown in FIG. 1 after it is sufficiently positioned, and the auxiliary roller 4 has an axis line of the pressure roller 2 as shown in FIG. A fulcrum 41 that coincides with the parallel axes can be provided to make it a rotatable type. In the case of this rotating type, the rotating side front end portion of the auxiliary plate 4 is brought into contact with the pressure roller 2 by its own weight or by providing a known pressing means. Alternatively, a flexible member such as a film may be elastically brought into contact with the pressure roller with a predetermined pressure. Further, the auxiliary member itself is not particularly limited in shape as long as it has the function as described above as well as the plate shape or the sheet shape as shown in the drawing.

When the sheet material P having the front end portion curled downward is conveyed toward the nip portion N by the apparatus of the above-described configuration, the front end of the sheet material P passes through the guide plate 3 and reaches the nip portion N. In the space, the auxiliary plate 4 is conveyed in such a direction as to come in contact with the pressure roller 2, but the auxiliary plate 4 does not come into direct contact with the pressure roller 2, and the sliding nip portion N is surely moved along the surface of the auxiliary plate 4. The sheet material P is guided and does not stay at the intermediate position.

Further, since the auxiliary plate 4 is arranged with an appropriate inclination, the impact when the front end of the curled sheet material P comes into contact with the auxiliary plate 4 is small, so that unfixed on the sheet material P is disturbed or the front edge of the sheet material P There is no chance that the part will break.

When the front end portion of the sheet material P is straight or has an upward curl, the sheet material P is fed along the guide plate 3 and smoothly fed to the nip portion N.

Next, another embodiment of the present invention will be described with reference to FIG. In the present embodiment, as shown in the figure, the auxiliary plate 4 of the above-mentioned embodiment is used as a guide sheet made of an elastic material like a film.
It is constituted by two layers of 42 and a holding material 43 which holds the guide sheet 42. The guide sheet 42 forms a free end 42 'in which the end near the nip portion N is pushed out from the holding material 43,
The free end 42 'is arranged so that the front end of the sheet material abuts.

By configuring the auxiliary plate as described above, foreign materials such as scattered developer and paper dust adhere to the guide sheet 42,
Even if the adhering foreign matter is caught by the front end of the sheet material, the free end 42 'elastically copes with it, thereby preventing the end portion from being broken or wrinkled.

It should be noted that if the planar shape of the tip of the free end 42 'is a chevron, a rectangle, a trapezoid, etc. shown in FIGS. 4 (A), (B) and (C), it is more effective for adhering foreign matter. is there.

Further, in another embodiment of the device shown in FIG. 5, the holding member 43 shown in FIG. 3 can be rotated by the rotating shaft 41 similarly to the device shown in FIG. By providing the portion 43 'so as to abut against the pressure roller 2 outside the sheet material passage area, excessive contact pressure is imposed on the sheet material passage area on the peripheral surface of the pressure roller 2. It is possible to guide the front end of the sheet material while preventing the above.

According to the device of the present invention having the above-mentioned structure, the auxiliary member for guiding the front end portion of the downward curl downward is arranged in the space from the guide member to the nip portion, and the auxiliary guide plate is rotatable. By bringing the tip of the rotating side into contact with the pressure roller, it is possible to deal with the curled sheet material at the front end, which was conventionally difficult, and it is possible to reliably feed the sheet material to the nip portion. Become. As a result, the sheet material stagnates at the intermediate position, the sheet material comes into contact with the pressure roller, and the sheet material is broken,
The situation that image distortion occurs is also eliminated.

[Brief description of drawings]

FIG. 1 is a diagram showing an apparatus according to an embodiment of the present invention, and FIG.
The figure which shows the example which changes the setting form of the auxiliary board of the figure device, the 3rd
FIG. 4 is a diagram showing another embodiment of the device, FIGS. 4 (A), (B) and (C) are diagrams showing an example of the shape of the free end of the device of FIG.
FIG. 6 is a plan view of a device of still another embodiment, and FIGS. 6A and 6B are views showing an example of a conventional device. 1 ... Fixing roller 2 ... Pressure roller N ... Nip part 3 ... Guide member (guide plate) 4 ... Guide auxiliary member (auxiliary plate)

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yoshimitsu Yamaguchi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Makoto Tanaka 3-30-2 Shimomaruko, Ota-ku, Tokyo Kya Non-Incorporated (72) Inventor Isao Ikemoto 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (56) Reference JP-A-60-159866 (JP, A) JP-A-56-70581 ( JP, A) JP 58-187970 (JP, A) JP 62-146863 (JP, A) JP 54-94338 (JP, A) JP 57-42069 (JP, A) JP 57-62063 (JP, A) JP 62-293272 (JP, A) Actual 59-144670 (JP, U) Actual 60-39064 (JP, U) Actual 64-77660 (JP , U) Actually open 63-39254 (JP, U) Actually open 63-68667 (JP, U) Actual opening 63-178862 (JP, U) Actual opening Sho 63-180873 (JP, U) Actual opening Sho 62-49171 (JP, U) Actual opening Sho 56-150959 (JP, U) Actual opening Sho 57 -197057 (JP, U) Actual opening Sho 58-69859 (JP, U) Actual opening Sho 59-25551 (JP, U) Actual opening Sho 58-5056 (JP, U) Actual opening Sho 58-157348 (JP, U) ) JP 62-52300 (JP, B2)

Claims (2)

[Claims] 1. A fixing roller, a pressure roller that is in pressure contact with the fixing roller to form a nip portion, a guide member that guides the movement of a recording material at the entrance side of the nip portion, the guide member and the nip portion. In the fixing device which has an auxiliary guide plate for guiding the recording material to the nip portion provided between the recording medium and the recording material carrying the unfixed image in the nip portion, and fixing the recording material, the auxiliary guide plate is A fixing device, which is rotatable about an axis parallel to a rotation axis of the pressure roller as a fulcrum, and a tip end of a rotation side of an auxiliary guide plate contacts the pressure roller. 2. The fixing device according to claim 1, wherein the auxiliary guide plate is a flexible elastic sheet.