JP2531249Y2 - Fixing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fixing device used for a recording device such as a laser printer, a facsimile, and an electrophotographic copying machine, and more specifically, to a roller-type fixing device.

(Prior Art) As a method for fixing a toner image formed on a sheet by electrophotography, the sheet is drawn between a fixing roller and a pressure roller which are pressed against each other and rotated to fix the toner image. Fusing devices are known. Silicone oil for preventing offset is applied to the outer peripheral surface of the fixing roller, and the toner transferred from the paper surface adheres. Therefore, in order to remove the toner, a part of the outer peripheral surface of the roller includes:
A cleaning blade made of an elastic body is brought into pressure contact with the cleaning blade.

For example, in a fixing device described in Japanese Utility Model Laid-Open No. 60-107968, the fixing roller is formed in a drum shape in advance in anticipation of expansion by a heat source. The cleaning blade that is pressed against the fixing roller has a side edge of a wavy portion that is pressed against the roller and is formed in an arc shape, and is designed to increase the pressing force at the center in the axial direction of the roller.
The cleaning blade, which is swingably supported by the side plate, is brought into pressure contact with the surface of the fixing roller by the spring force of a spring applied between both ends of the blade holding member and the side plate.

(Problem to be Solved by the Invention) The cleaning blade pressed against the fixing roller is treated as a consumable because it is rubbed and worn by the roller, and is replaced when a predetermined time elapses or a predetermined number of copies are reached. . Therefore, it is advantageous in terms of cost to make this blade a common part so that it can be used in various types of copying machines. However, designing and manufacturing a cleaning blade having a new shape simply because the cleaning function is not satisfied in some copying machines, for example, a high-speed copying machine, causes a problem of increasing the cost of parts.

The cleaning blade, which is a consumable, needs to be replaced periodically, but this blade is pressed against the peripheral surface of the fixing roller by a spring spanned between the blade holding member and the immovable member. Need to attach and detach this spring. Further, in the apparatus described in the above publication, the pressing force of the cleaning blade against the fixing roller is strong at both axial ends of the roller,
It tends to appear weak in the center. This uneven pressing force is caused by the fact that the toner scraped off from the peripheral surface of the fixing roller by the cleaning blade and the silicon oil as an anti-offset liquid accumulate particularly in the central portion in the longitudinal direction of the blade, and gradually grow due to the repetition of the copying operation and the time elapses. To solidify. The solidified toner or the like thermally contracts to make the pressure contact force between the blade and the roller nonuniform, thereby causing a phenomenon that it is impossible to remove the toner or the like flowing in later. When this phenomenon occurs, toner and the like are present on the peripheral surface of the fixing roller, and are retransferred (offset) to the sheet to be fixed and appear as "black stripes" on the copy, greatly impairing the copy quality. Therefore, if the spring is strengthened in order to enhance the cleaning effect, there is a problem that the work of attaching and detaching the spring becomes troublesome and the service cost increases.

Therefore, an object of the present invention is to provide a fixing device that can enhance the pressing force of the cleaning blade against the fixing roller at a low cost, maintain good cleaning performance for a long time, extend the service interval, and reduce the service cost. It is in.

(Means for Solving the Problems) The fixing device of the present invention inserts a sheet on which an unfixed toner image is formed between a fixing roller and a pressure roller which rotate while being pressed against each other, and the unfixed toner image is In a fixing device provided with a cleaning blade made of an elastic body that cleans the surface of the fixing roller while being pressed against a part of the outer peripheral surface of the fixing roller, pressurizes a holding member holding the cleaning blade. Means for providing a pressure contact force between the cleaning blade and the fixing roller at the central portion in the axial direction rather than at both end portions.

(Operation) The pressurizing means acts while the cleaning blade is in pressure contact with the fixing roller, and the pressing force between the blade and the fixing roller is made greater at the central portion than at both ends in the roller axis direction. The toner and oil blocked by the cleaning blade flow in the axial direction of the fixing roller.

Hereinafter, the present invention will be described in detail based on the illustrated embodiment.

First, in FIG. 1, reference numeral 1 denotes a fixing roller having a heating source (not shown) therein. A pressure roller 2 having an elastic surface is pressed against the fixing roller 1 and is driven to rotate in the directions indicated by arrows. A cleaning mechanism 3 is in contact with the outer peripheral surface of the fixing roller 1 such that the cleaning mechanism 3 can be separated from and connected to the cleaning mechanism. The cleaning mechanism 3 is held by a movable side plate 4 (only one is shown) that is rotatably supported by a support shaft 5 on a front plate and a rear plate (not shown) that rotatably support the rollers. I have. The cleaning mechanism 3 includes a cleaning unit 6 and a release agent applying mechanism 7. The cleaning mechanism 6 includes a pair of brackets 9 (only one is shown) rotatably fitted to the pins 8 fixedly mounted on the movable side plate 4, a holding member 10 fixed to these brackets 9, and a holding member The cleaning blade 12 is held by an elastic plate 11 and is made of an elastic material for bringing a leading edge 12a of the fixing blade 1 into and out of contact with the peripheral surface of the fixing roller 1. An urging spring 9a is stretched between the bracket 9 and the movable side plate 4 to urge the cleaning blade 12 clockwise.

The release agent applying mechanism 7 includes an oil application felt 13 for applying oil pumped from a tank (not shown) storing a release agent (not shown) such as silicon oil to the outer peripheral surface of the fixing roller 1. The blade 14 is configured to evenly distribute the applied oil and scrape off excess oil. The blade 14 is attached to a holder 16 via a spring plate 15.
Is held in. Cleaning mechanism 3 shown in FIG.
5 shows a state in which the cleaning blade 12, the oil-applied felt 13, and the blade 14 are brought into contact with the peripheral surface of the fixing roller 1 with a predetermined pressing force.

The copy paper P on which the unfixed toner image T is formed is sent to a nip portion between the rollers 1 and 2 by a conveying means (not shown), and the unfixed toner image is heated and melted and fixed. A portion Ta of the toner image transferred from the paper P adheres to the surface of the fixing roller 1, and the toner Ta is blocked by the edge of the cleaning blade 12 pressed against the roller surface, and the toner Ta is removed together with the silicon oil. It is deposited as a lump Tb.

By the way, the cleaning blade 12 is not pressed against the fixing roller only by the biasing spring 9a, but is also pressed and biased at the center in the longitudinal direction. The structure will be described with reference to FIG. 2 and FIG. In these figures, a pressing screw 17 as a pressing means is screwed into a substantially central portion of a stay 18 bridged between the brackets 9. The distal end portion 17a of the pressure screw 17 is positioned so as to be able to engage with the contact portion 10a formed at the center of the holding member 10. When the pressing screw 17 is screwed in, the central portion of the holding member 10 is bent, and the cleaning blade 12 held by the holding member 10 is pressed against the peripheral surface of the fixing roller 1.

FIG. 6 shows the distribution of the pressing force of the pressed cleaning blade 12 in the roller axis direction. As shown by the line A, the central part of the cleaning blade 12 pressed by the pressure screw 17 is
The pressing force is approximately 70 g, and the pressing force at both ends (the front and rear portions of the fixing device) is approximately 30 g. Such a distribution of the pressing force is appropriately determined according to the material of the cleaning blade 12, the material of the elastic layer forming the surface of the fixing roller 1, and the like. The press-contact force can be adjusted by adjusting the screw-in length of the pressure screw 17. Also, the pressing screw 17 has a length l (third
(See Fig. 6), if the optimum pressure distribution shown in Fig. 6 can be obtained when the screw is screwed in, if the effective length of this screw is set to the length l, it is sufficient to screw the screw under the neck. A predetermined pressing force can be reproduced without troublesome adjustment work.

As shown by line A in FIG.
When the pressing force of the fixing roller 1 is set, toner, oil and the like adhering to the peripheral surface of the roller are removed from the leading edge 12 of the blade.
The toner is scraped off by b and deposited as a toner lump as shown by the symbol Tb. The scraped toner and the like are deposited over the entire length of the cleaning blade 12. In this case, the lump of toner or the like blocked by the blade has a large pressure contact force at the central portion of the blade, and therefore cannot pass through the blade and go around the back surface. Therefore, the gradually growing lump Tb of the toner or the like is forced to go to both ends 12b and 12c of the blade, and moves toward both ends of the roller 1 as shown by reference numeral Tc in FIG. 1 will flow down from both ends. Therefore, there is no toner remaining on the peripheral surface of the fixing roller 1 after passing through the cleaning blade 12, and the surface of the roller used at the time of fixing the next toner image is maintained in a clean state.

Incidentally, the line B in FIG.
Like the cleaning blade in the apparatus described in No. 7968, the distribution of the pressing force when the center is not pressed is shown, and the center is weaker than both ends, such as 5 g at the center and about 10 g at both ends. Power. With such a distribution of the pressing force, a lump of the deposited toner or the like passes through the blade and wraps around the back surface and remains on the peripheral surface of the roller, and this toner is offset on the copy paper when the next toner image is fixed. This causes a phenomenon in which the black stripes are formed.

In the embodiment shown in FIG. 2 and FIG. 3, the pressing force is obtained by the screwing of the pressing screw. If the desired pressure distribution can be obtained simply by contacting the pressure contact, the adjustment operation by the pressure screw can be omitted.

This example will be described with reference to FIGS. 4 and 5. Stay 18
Is provided with a pressure means corresponding to a substantially central portion of the fixing roller 1 and the cleaning roller 12 in the longitudinal direction. The pressurizing means includes a pressurizing lever 21 rotatably supported on the stay 18 via a bracket 19 and a support shaft 20, and a spring 22 for urging the lever in one direction. The pressurizing lever 21 has a bent piece 21a formed at the tip end thereof, which locks one end of the spring 22 and abuts on the holding member 10.
An L-shaped space 21b for engaging the 10a is provided. Spring 22
Is locked to a stay 18. When the lever 21 is swung, the base end 21c of the pressure lever 21
Abuts against the lower surface 18a. FIG. 4 shows a state in which the cleaning blade 12 is separated from the peripheral surface of the fixing roller 1.
Are located at a distance from each other. Now, as shown in FIG. 5, the cleaning blade 12 is fixed to the fixing roller 1.
When it is swung to be pressed against the upper surface 10a of the holding member 10,
Enters the L-shaped space and swings the pressure lever 21. When the distal end of the cleaning blade 12 is pressed against the peripheral surface of the fixing roller 1, the base end 21b of the pressure lever 21 abuts against the lower surface 18a to restrict its swing. At this time,
The pressing lever 21 generates the same pressing force as when the holding member 10 is pressed using a pressing screw having a screwing depth 1 (see FIG. 3). In other words, the pressing lever 21 is formed with the bent piece 21a at a position where the pressure contact force distribution as shown in FIG. 6 can be obtained. The cleaning blade
Needless to say, when the roller 12 is moved toward and away from the fixing roller 1, the release agent applying mechanism 7 is simultaneously moved in conjunction with this. In the embodiment shown in FIG. 4, since the screwing adjustment of the pressure screw is not required, the maintenance work for blade replacement is simplified and the reproducibility of the predetermined pressure contact force distribution is good.

(Effects of the Invention) As described above, according to the present invention, a desired pressure contact force can be obtained only by providing a pressing means having a simple structure at the center of the holding member of the cleaning blade, and the blade is scraped off. The toner and oil can flow down to both ends in the roller axial direction, and good cleaning performance can be maintained for a long period of time. Further, since it is not necessary to increase the pressure of the spring for pressing the cleaning blade against the fixing roller, the work at the time of blade replacement becomes easy and the service cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a front sectional view of a fixing device showing one embodiment of the present invention,
FIG. 2 is a perspective view showing a main part of the above, FIG. 3 is a front view showing a cleaning blade and a fixing roller in a pressurized state, and FIG. 4 is a front view showing another embodiment of the present invention, showing only the main part. FIG. 5 is a diagram showing the operation of the above, and FIG. 6 is a diagram showing the distribution of the pressing force between the cleaning blade and the fixing roller obtained when the present invention is carried out. 1 ... fixing roller, 2 ... pressure roller, 3 ... cleaning mechanism, 6 ... cleaning section, 8 ... pin, 9 ... bracket, 10 ... holding member, 12 ... cleaning blade, 9a ...
... urging spring, T ... unfixed toner image, P ... paper, 21 ... pressure lever.

Claims (1)

(57) [Scope of request for utility model registration] An unfixed toner image is fixed by inserting a sheet on which an unfixed toner image is formed between a fixing roller and a pressure roller which rotate while being pressed against each other. In a fixing device including a cleaning blade made of an elastic body that cleans the surface of the roller while being pressed against a part thereof, a pressing member is provided on a holding member that holds the cleaning blade. A fixing device characterized in that the pressing force is larger in the central part than in both ends in the axial direction.