JP2002040861A - Image fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image fixing device, which prevents harmful effects which are caused by flowing-in of toner to a member supporting a cleaning roll, and an image forming device provided with this image fixing device. SOLUTION: In the image fixing device where a recording material to which an unfixed toner image has been transferred is made to pass between a fixing roll and a pressure roll 15, and the toner image is fixed on the recording material by heat and pressure, and a cleaning roll 21 is brought into contact with the pressure roll 15 in order to sweep out the toner stuck to the roll surface, the cleaning roll 21 has an effective area length in the lengthwise direction longer than the cleaning roll 15, and a large-diameter part 21a having an outside diameter of 130 to 200% of the cleaning effective area is provided in a cleaning non-effective area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image fixing device for permanently fixing a toner image by applying heat and pressure to a recording material onto which the toner image has been transferred, and an image forming apparatus such as a copying machine or a laser beam printer equipped with the same. The present invention relates to a forming apparatus.

[0002]

2. Description of the Related Art At present, image forming apparatuses such as copiers and laser beam printers to which an electrophotographic method is applied are widely known. These image forming apparatuses fix a recording material on which a toner image is transferred by a transfer unit. The toner image is conveyed to an apparatus, where heat and pressure are applied to permanently fix the transferred toner image.

A fixing device used in such an image forming apparatus generally has a built-in heater 50 and forms a releasable resin layer such as PFA on a core metal such as aluminum as shown in FIG. An elastic layer such as silicone rubber or silicone sponge having heat resistance and low hardness is provided on a cored bar made of aluminum or the like, and a coating layer made of a highly releasable resin such as PFA is provided on the surface thereof. It is composed of a roller pair with the formed pressure roller 52.

Then, when the recording material P passes between the fixing roller 51 and the pressure roller 52, heat and pressure are applied to fix the toner.

When a large number of recording materials containing 10% or more of calcium carbonate CaCO ₃ (hereinafter referred to as “charcoal”) as a filler are passed through a large number of pages, the recording materials contained in the conveyed recording materials are contained. The coal char and the fluororesin layer, which is the surface layer of the fixing roller, are frictionally charged, so that the char is positively charged and the fluorocarbon resin is negatively charged.

In addition, since a negative fixing bias is applied to the core of the fixing roller for the purpose of preventing offset, the surface of the fixing roller has a negative potential.

An electrostatic force acts between the positively charged charcoal, the negatively charged fluororesin, and the surface of the fixing roller which has a negative surface potential due to the fixing bias for preventing offset. Charcoal interposed on the surface of the recording material electrostatically adheres to the surface of the fixing roller. Further, even when a fluororesin having excellent releasability is used on the surface of the fixing roller, the release of releasability is caused by the adhesion of char, and the coal is more likely to adhere.

When charcoal adheres to the surface of the fixing roller,
Two types of offset phenomena occur: (1) the fixing bias is offset by the positive charge, which is the charge of coal, causing an electrostatic offset, and (2) the releasability is reduced, causing an offset. Resulting in. Then, the offset toner is transferred from the surface of the fixing roller to the surface of the pressure roller at the conveyance interval between the recording materials, and is accumulated on the surface of the pressure roller.

Through such a process, the toner adhering / volume to the pressure roller 52 becomes dirty on the back surface of the recording material, returns to the fixing roller 51 again, and becomes dirty as the surface of the recording material. Therefore, as a countermeasure, the cleaning roller 53 is supported on the pressure roller 52 by a bearing 54 and is brought into contact with the pressure roller 52 to collect the toner and charcoal adhered to the surface of the pressure roller. Prevents coal char from adhering and keeps the pressure roller surface clean at all times.

The reason why the toner and charcoal adhered to the pressure roller 52 are collected by the cleaning roller is that the releasability of the cleaning roller 53 is inferior to that of the release layer on the surface of the pressure roller. Therefore, a metal material such as aluminum or iron is used for the cleaning roller 53.

[0011]

However, the above-described conventional pressure roller cleaning system of the image forming apparatus has the following problems.

The contact between the cleaning roller 53 and the pressure roller 52 includes
The center distance between the metal cores is kept constant, and the abutting position is fixed by determining the abutting position, or a spring pressing method in which a spring is used to contact the pressing roller 52 is considered.
53 is provided to collect toner and charcoal,
As compared with the outer diameter of the cleaning roller 53 in the initial stage, the outer diameter increases due to the adhesion of toner and charcoal as it is used.

That is, as the number of formed images increases, the amount of toner adhered to the cleaning roller 53 increases, and as the outer diameter increases, the amount of biting into the pressure roller 52 increases. During printing, the pressure roller 52
As the toner adhering to the cleaning roller 53 is softened by the heat transfer from the cleaning roller 53, as the amount of bite into the pressure roller 52 increases, the toner is melted from the effective cleaning area formed between the pressure roller 52 and the cleaning roller 53. As a result, the collected toner flows out of the effective cleaning area on the cleaning roller. When the image forming operation is further continued in this state, the toner that has run out of the effective cleaning area accumulates on a shaft of the cleaning roller 53 provided to support the cleaning roller 53 and a bearing that receives the toner.

FIG. 10 schematically shows a model diagram of this situation.
The toner that has accumulated on the shaft and bearings of the cleaning roller 53 in this way is fixed by the fixing roller 51 during printing.
Since it is in a molten state by the heat from the pressure roller 52, no problem occurs.

However, during non-printing standby (standby state), the amount of heat generated by the fixing roller 51 is small, and the temperature of the pressure roller 52 is also reduced. The temperature of the pressure roller 52 is reduced so as to follow the room temperature because there is no heat generation.

As described above, when the heat transmitted to the cleaning roller 53 is reduced, the toner in a molten state is also cured. Then, the toner accumulated on the shaft and the bearing of the cleaning roller 53 hardens from the molten state during printing, and enters into the gap between the shaft of the cleaning roller 53 and the bearing, and the state of the shaft of the cleaning roller 53 and the bearing. Will be cured in the state of covering.

In this state, when the next print signal is received, in preparation for performing the image forming operation, the fixing device is turned on by the heater.
50 is turned on to raise the temperature of the fixing roller 51 to a fixing-possible temperature. At the same time, the rotation operation is performed, and the temperature of the pressure roller 52 is also increased.

The rotation of the cleaning roller 53 driven by the pressure roller 52 is hindered by the toner hardened and accumulated in the bearing portion. Then, the pressurizing roller 52 that rotates the cleaning roller 53 is not smoothly rotated.

On the other hand, when the thermistor in contact with the fixing roller 51 detects the fixing temperature, an image forming operation is performed, and the recording material to which the unfixed toner has been transferred is conveyed. However, the bad effect of the toner hardened and accumulated on the cleaning roller shaft and the bearing hinders the rotation of the cleaning roller 53, thereby hindering the rotation of the pressure roller 52, and is conveyed to the fixing nip N. The recording material that has come into contact with the recording material at the fixing nip (so-called jam).

The above-mentioned problem occurs earlier in the fixed distance between shafts method than in the spring pressure method. However, the problem still occurs in the spring pressure method. .

In the case of a recording material such as paper containing charcoal as a filler, offset toner adheres to the pressure roller 52 to cause stain on the image. The cleaning roller 53 is required because the toner adhering to the surface of the pressure roller is collected.On the other hand, even though the recording material does not contain charcoal as a filler, offset toner is generated, roller
Since the toner does not adhere to or accumulate on the image 52 and no stain is generated on the image, the necessity of the cleaning roller 53 is reduced. However, the cleaning roller is
If the roller 53 is in contact, the offset toner transferred to the pressure roller 52 will be collected, and the above-described problem will occur.

As described above, in the conventional pressure roller cleaning method of the image fixing device, there is a problem that even a user who uses a recording material that does not require a cleaning roller is caused by the presence of the cleaning roller. It has been desired to solve the above problems.

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide an image fixing apparatus and an image forming apparatus provided with the same, which prevent problems caused by toner flowing into a member supporting a cleaning roller. Is provided.

[0024]

A typical configuration according to the present invention for achieving the above object is to pass a recording material on which an unfixed toner image has been transferred between a pair of fixing rotators, and to heat, In an image fixing apparatus, the toner image is fixed on a recording material by pressing, and a cleaning rotator is brought into contact with at least one fixing rotator in order to clean toner adhered to the surface of the fixing rotator. The cleaning rotator has a longer effective area length in the longitudinal direction than the fixing rotator, and has a large-diameter portion having an outer diameter of 130 to 200% of the outer diameter of the cleaning effective area in the cleaning non-effective area. It is characterized by the following.

In the above configuration, the toner collected on the cleaning rotator is prevented from flowing in the axial direction of the cleaning rotator by the large-diameter portion, so that the toner flows to a support member such as a bearing of the cleaning rotator. Nothing. Therefore, the cleaning rotator always rotates smoothly, and the fixing rotator also rotates smoothly, so that the occurrence of clogging of the recording material in the fixing unit is prevented.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an image fixing apparatus according to an embodiment of the present invention and an image forming apparatus having the same will be specifically described.

[First Embodiment] FIGS. 1 to 4 show a first embodiment of the present invention. FIG. 1 is a schematic sectional view of a pressure roller and a cleaning roller. FIG. FIG. 3 is a schematic explanatory diagram of the image fixing device, and FIG. 4 is an explanatory diagram showing the relationship between the longitudinal direction dimensions of a pressure roller and a cleaning roller.

{Image Forming Apparatus} First, the overall configuration of the image forming apparatus will be described. In FIG. 2, reference numeral 1 denotes an apparatus main body of a laser beam printer, and a lower portion of the apparatus main body is provided with a mounting portion for a feeding cassette 2 for loading and storing recording materials P. It is detachably attached to the main body 1. Reference numeral 3 denotes a feed roller which feeds the recording material P loaded on the feed cassette 2 from the uppermost side, and the feed roller 1
Feed one by one. A guide member 5 guides the recording material P fed by the feed roller 3. Reference numeral 6 denotes a registration roller pair. The tip of the recording material P is applied to the nip portion of the stopped registration roller pair 6 to correct skew, and then rotated at a predetermined timing to form the recording material P into an image forming unit. Transport to

Reference numeral 7 denotes a process cartridge which is detachably mounted on the apparatus main body 1. Inside the process cartridge 7, a developing device 7c having a photosensitive drum 7a and a primary charging roller 7b, a toner container 7c1 and a developing roller 7c2 around the photosensitive drum 7a, a cleaning device 7d
Is equipped. 8 is a laser beam L according to image information
Is a scanner unit that scans the photosensitive drum 7a.
To form a latent image. A transfer roller 9 is in contact with the photosensitive drum 7a, and transfers a toner image from the photosensitive drum 7a when the recording material P passes between the transfer roller 9 and the photosensitive drum 7a.

A transport guide 10 transports the recording material P after image transfer to the image fixing device B. The fixing device B fixes an image (toner image) transferred to the recording material P, and its configuration will be described later in detail.

Reference numeral 11 denotes a discharge roller pair, which discharges the recording material P after fixing the image to the outside of the apparatus with the image side down. Reference numeral 12 denotes a discharge unit, which is formed on the upper surface of the apparatus main body 1 and stacks and holds the recording material P discharged outside the apparatus after the image is fixed.

In the laser beam printer constructed as described above, when image formation is instructed by a host computer (not shown), first, the feed roller 3 and the separation roller pair 4
Is rotated and fed one by one from the uppermost recording material P in the feeding cassette 2, guided by the guide member 5 and guided to the registration roller pair 6. Then, the registration roller pair 6
Transports the recording material P between the photosensitive drum 7a and the transfer roller 9 in synchronization with the image formed on the photosensitive drum 7a, and transfers the recording material P between the photosensitive drum 7a and the transfer roller 9 The toner image is transferred when passing through.

Further, the recording material P after the image transfer is carried by a conveyance guide.
The toner image is conveyed to the fixing device B by being guided by 10, and heat and pressure are applied to fix the toner image. The recording material P on which the image has been fixed is discharged to the discharge unit 12 by the discharge roller pair 11 and stacked.

<Fixing Device> Next, the configuration of the fixing device B will be described with reference to FIG. In FIG. 3, reference numeral 1 denotes a fixing roller 13 serving as a fixing rotating body. A release layer 13b made of a fluororesin such as PFA or PTFE is provided on a core bar 13a made of, for example, aluminum or iron. A heater 14 is provided to heat the fixing roller 13 from the inside.

On the other hand, a pressure roller 15 as a fixing rotating body
Is pressed against the fixing roller 13 by a pressure unit (not shown),
A fixing nip (contact portion) N is formed. Pressure roller 15
Is an elastic layer 15b made of heat-resistant silicon sponge rubber or the like on a core metal 15a of, for example, aluminum or iron.
Further, a release layer 15c made of a resin having good releasability made of a fluororesin such as PFA and PTFE is formed.

The release layer 13b of the fixing roller 13 prevents the "offset phenomenon" in which the unfixed toner image is transferred to the fixing roller 13 and stains the subsequent image. In addition, by applying a negative DC voltage from the DC power supply 16 as a fixing bias to the core metal 13a of the fixing roller 13, a negative charge is generated on the surface of the fixing roller, and the occurrence of the offset phenomenon is positively prevented. ing.

The release layer 15c of the pressure roller 15 is provided with an offset toner transferred from the recording material to the pressure roller 15 via the fixing roller 13 and a toner adhered to the back surface of the recording material. It is to prevent that.

The pressure diode element 17 is connected between the core 15a of the pressure roller 15 and the apparatus body ground such that the pressure roller core is the cathode and the body ground is the anode. By preventing the gold potential from becoming negative, a potential difference is created between the surface of the fixing roller 13 and the core metal 15a of the pressure roller, and the electric field prevents an offset phenomenon from the recording material to the fixing roller 13.

The unfixed toner T is fixed on the recording material by being heated and pressed in the fixing nip N.

Reference numeral 18 denotes an entrance guide, which conveys a recording material on which an unfixed toner image is formed to a fixing nip N, and fixes the recording material as a permanent image on the recording material.

A thermistor 19 is a temperature sensor for detecting the surface temperature of the fixing roller 13. The thermistor 19 is in contact with the surface of the fixing roller at a predetermined contact pressure, and a heater for keeping the temperature of the fixing roller surface constant. The energization to 14 is turned on / off (the electric circuit for turning on / off the energization is not shown).

Reference numeral 20 denotes a fixing / separating claw 20 for preventing the recording material from winding around the fixing roller. PFA and P are excellent in releasability in order to prevent toner and the like from adhering to the surface.
A coating such as TFE is provided.

In an image forming apparatus provided with an image fixing device having such a configuration, when a print signal is input from a computer or the like, preparation for image formation is started.

In response to the input of the print signal, the temperature detected by the thermistor is detected, and if the temperature required for image fixing has been reached, image formation is started and the temperature required for image fixing is reached. If not, energize the heater 14 and fix the fixing roller 13 until the temperature required for image fixing is reached.
To start image formation. When the recording material P to which the toner has been transferred is conveyed, heat and pressure are applied to the recording material P to permanently fix the toner image to the recording material.

A cleaning roller 21 as a cleaning rotator is in contact with the pressure roller 15, and
The toner and the like adhered to the pressure roller 15 are cleaned.

Further, from the viewpoint of energy saving,
When the image forming apparatus is not used for a certain period of time or more, it is possible to set such that power supply to the heater is turned off to save energy. For this reason, if the image forming apparatus is frequently used, the heater 14 is in a standby state in which power is supplied to the heater 14, and the image forming operation starts immediately upon receiving a print signal. Since the power supply to the power supply 14 is OFF, the temperature of the surface of the fixing roller decreases, so that the fixing roller 13 is heated before image formation is started.

As a preferred example of the image fixing device, the present embodiment is configured as follows. That is, in the present embodiment, the image forming apparatus is capable of printing 25 sheets of A4 size recording material per minute by passing in the horizontal direction.

The fixing roller 13 has a diameter of 40 mm and a thickness of 1 mm.
Aluminum as the core metal 13a and the thickness as the release layer 13b
It covers a 50 μm PFA tube. As a fixing bias, a DC-700 is applied to the core metal 13a of the fixing roller 13.
V is applied by a DC power supply 16 so that the surface potential of the fixing roller is maintained at about −650 V.
A potential difference for preventing offset is provided between the five. During image fixing, the temperature detected by the thermistor 19 is 18
Turn on power to heater 14 so that it falls within the range of 0 ± 5 ° C
-OFF control is being performed. During the standby operation, the operation of turning on the power to the heater when the detected temperature reaches 160 ° C. and turning it off when the temperature reaches 170 ° C. is repeated so that the thermistor detected temperature falls within the range of 160 to 170 ° C.

The pressure roller 15 is an iron core 15a having a diameter of 14 mm.
An elastic layer 15b made of silicon sponge rubber having a thickness of 8 mm is formed on the elastic layer.
And a pressure roller having a hardness of about 56 degrees (load of 1 kg with an Asker C hardness meter) and a pressure roller of about 20 degrees.
By pressing against the fixing roller with a pressing force of 0 N (Newton), a fixing nip N having a width of about 5 mm is obtained.
A configuration in which a pressure diode element 17 having a withstand voltage of 2 KV is connected between the pressure core metal and the main body ground with the pressure core metal side as a cathode and the main body ground side as an anode to maintain the pressure roller surface at a positive potential. And

Unfixed toner image 7 formed on recording material P
Is guided to a fixing nip N formed by the fixing roller 13 and the pressure roller 15 along the fixing entrance guide 18.

The fixing / separating claw 20 is made of a polyimide resin having excellent heat resistance as a base material, and the surface layer is formed of a PF having excellent release properties.
A resin is coated.

As a cleaning member for cleaning toner, charcoal and the like adhering to the surface of the pressure roller 15,
A φ12 aluminum cleaning roller 21 is supported by a bearing 22 as a support member, and is brought into contact with the pressure roller 15. The cleaning roller 21 is brought into contact with the pressure roller 15 by a spring spring 23 which presses the cleaning roller 21 against the pressure roller 15 with a pressing force of about 30 N (Newton). Configuration.

{Relationship Between Pressure Roller and Cleaning Roller} Next, the positional relationship and shape of the pressure roller 15 and the cleaning roller 21 in the longitudinal direction (direction orthogonal to the recording material conveyance direction), and can be used in the image forming apparatus. Recording material of the largest width,
The relationship with the image forming area will be described.

In the fixing device of this embodiment, as shown in FIG. 4, the cleaning roller 21 and the pressure roller 15 are provided at both ends of a cleaning area A1 (effective cleaning area) where the cleaning roller 21 and the pressure roller 15 are in contact. Is provided with a non-cleaning area A2 (cleaning non-effective area) which does not touch.

By setting such a longitudinal positional relationship between the image forming area, the pressure roller 15 and the cleaning roller 21, the toner is first collected on the cleaning roller 21 because the image is formed. When the amount of toner collected in that area increases, the collected toner overflows the cleaning area A1 where image formation is not performed. If the image formation is further continued in this state, the toner will protrude from the cleaning area A1 to the non-cleaning area A2. In this state, there is no hindrance to the rotation of the cleaning roller 21. But,
When the toner is further used in this state, as described above, the toner that has overflowed into the non-cleaning area A2 flows into and accumulates on the shaft of the cleaning roller 21 and the bearing that supports it.

As described above, by providing the non-cleaning area A2 on the cleaning roller, the toner protruding from the cleaning area A1 can be removed from the cleaning roller 21.
It is possible to greatly increase the time required to flow into the shaft and the bearing 22 thereof. However, if the image forming operation is performed to a certain degree or more, it flows into the shaft of the cleaning roller 21 and the bearing 22 thereof, and there is a concern that the above-described problem may occur.

Therefore, in this embodiment, as shown in FIG. 1, a large-diameter portion 2 larger than the outer diameter of the cleaning area A1 of the cleaning roller 21 is attached to the end of the cleaning roller 21.
The formation of 1a prevents the toner that has overflowed into the non-cleaning area A2 on the cleaning roller from flowing into the shaft of the cleaning roller 21 and its bearing 22.

In this embodiment, the outer diameter of the cleaning roller 21 is 12 mm, and the outermost end (excluding the bearing) of the cleaning roller 21 is a large diameter portion having a width of 2 mm and an outer diameter of 17 mm.
21a was provided. In this embodiment, the cleaning roller 21 having an outer diameter of 12 mm has an outer diameter of 17 mm, that is, a radius of 17 mm.
Although the provision of the 2.5 mm wall prevents the toner from flowing into the bearing 22, the effect of preventing the flow of the toner is increased by making the wall larger than this. However, if so, the pressure roller 15 and its bearing, the cleaning roller 21
The configuration and arrangement of parts such as the bearing 22 and the like are difficult. Therefore, the outer diameter of the large-diameter portion 21a serving as a wall for preventing toner from flowing into the outer diameter of the cleaning roller 21 is suitably about 130 to 200%.

By providing a wall for preventing the inflow of toner at the end of the cleaning roller in this manner, it is possible to prevent the toner that has overflowed into the non-cleaning area A2 from flowing into the cleaning roller shaft and its bearing 22. The rotation of the cleaning roller 21 and the pressure roller 15 is always kept smooth. For this reason, it is possible to prevent the recording material P from being clogged due to the non-smooth conveyance of the recording material P in the fixing nip N.

[Second Embodiment] Next, a second embodiment of the image fixing device will be described.
An embodiment will be described with reference to FIG. In the image fixing device used in this embodiment, the description of the same parts as those in the first embodiment described above is omitted, and a U-shaped bearing for receiving the shaft of the cleaning roller, which is a feature of the present embodiment, is provided. The effect will be described.

In the present embodiment, as shown in FIG. 5, the cleaning roller 21 is supported by a bearing 22 as a U-shaped support member, and the pressing roller 15 of the U-shaped tip portion is supported. The tip portion 22a on the upstream side in the rotation direction of the cleaning roller 21 is formed at an acute angle with respect to the contact position between the cleaning roller 21 and the contact position.

In the case of a U-shaped bearing, the toner accumulated on the shaft of the cleaning roller 21 and its bearing 22 is determined based on the contact position between the pressure roller 15 and the cleaning roller 21 among the two end portions 22a and 22b. In this case, a small amount of toner accumulates at the front end portion 22b on the upstream side in the rotation direction of the cleaning roller 21, but more toner accumulates on the front end portion 22a on the downstream side of the rotation. This is because the toner that has melted during printing is rotated around the axis by the rotation of the shaft of the cleaning roller 21, and at that time, the toner from the upstream side of rotation rotates to the bearing of the downstream side bearing. By hitting the front end portion 22a, a place to go is lost, and a large amount is accumulated on the downstream side of rotation.

Therefore, in this embodiment, as shown in FIG. 5, a U-shaped bearing for receiving the shaft of the cleaning roller 21 is provided.
The tip 22a on the downstream side of the rotation of 22 (the side that comes into contact with the bearing first when the shaft of the cleaning roller is rotating) has an acute angle,
The edge is used to scrape off the toner that tends to accumulate.

The effect of scraping off the toner by forming one end portion 22a of the U-shaped bearing 22 into an edge is divided into two. That is, one is a scraping effect by being sent to the edge portion in a state where the toner at the time of printing is melted, and the other is a standby state, a sleep state, when any of the non-printing state continues for a long time, Although the melted toner hardens, the toner accumulated in the edged bearing 22 accumulates thinner than the toner accumulated in other parts.
Therefore, with the transition from the standby state to the printing operation, the thinly hardened toner has an effect of being scraped off by being cracked and peeled off by a shock at the time of operation.

As described above, the tip end 22a on the downstream side of the rotation of the U-shaped bearing 22 that receives the shaft of the cleaning roller 21 is sharply edged, so that the toner flowing from the cleaning roller 21 into the bearing 22 accumulates. Is gone,
The rotation of the cleaning roller 21 and the pressure roller 15 is always smoothly performed, and the same effect as that of the first embodiment can be obtained.

[Third Embodiment] Next, a third embodiment of the image fixing apparatus will be described.
An embodiment will be described with reference to FIG. In this embodiment, the description of the same parts as those in the first embodiment described above is omitted, and a sliding bearing which is free to rotate between a shaft of a cleaning roller and a bearing for receiving the same is a feature of this embodiment. (Hereinafter referred to as “bush”) will be described.

As shown in FIG. 10 described above, the toner collected on the shaft of the cleaning roller 53 and its bearing 54 is removed from the shaft by the bearing 54.
Are cured together, and the toner and the cleaning roller 53 are hardened depending on the nature of the resin which is the main component of the toner.
The shaft and the bearing 54 are united together and hardened. Then, the stopping force of the solidified toner is larger than the rotating force received by the cleaning roller 53 from the pressing roller, and the pressing roller cannot rotate smoothly due to the effect of the stopping force. And the recording material is clogged.

Therefore, in this embodiment, as shown in FIG. 6, a bush 24 is inserted between the shaft of the cleaning roller 21 and the bearing 22 for receiving the same, so that the cleaning roller 21 is rotatable with each other, and the toner accumulated in the bearing is hardened. Even if it hardens, the cleaning roller 21 and the bearing 22 are prevented from hardening together.

As described above, by inserting the bush 24, even if the toner flowing into the bearing 22 is hardened and solidified, the cleaning roller 21 and the bush 24 or the bush 24 and the bearing 22 are joined together. It hardens and does not hinder the rotation of the cleaning roller 21.

As described above, by inserting the bush 24 between the shaft of the cleaning roller 21 and the bearing 22 for receiving the same,
The toner flowing into the bearing portion does not harden the shaft of the cleaning roller 21 and the bearing 22 integrally, and the rotation of the cleaning roller 21 and the pressure roller 15 is always smoothly performed. For this reason, it is possible to obtain the same effect as in the above-described embodiment.

[Fourth Embodiment] Next, the fourth embodiment of the image fixing apparatus will be described.
An embodiment will be described with reference to FIG. Also in this embodiment, the description of the same parts as those in the first embodiment described above is omitted, and the shape of the bearing for receiving the shaft of the cleaning roller and the effect thereof, which are features of the present embodiment, will be described.

In the present embodiment, as shown in FIG. 7, the length of the cleaning roller 21 is the length of the image area of the recording material and the length of the cleaning area requiring cleaning, and the cleaning roller 21 does not come into contact. The bearing 25 serving as a support member is configured to be in contact with both end regions in the longitudinal direction of the pressure roller 15. And the bearing 25
Is configured such that the side in contact with the pressure roller 15 is an arc-shaped surface.

Further, the radius of the cleaning roller 21 is D 2, the radius of the arc shape of the bearing 25 is D 1, and the deformation of the pressure roller 15 caused when the cleaning roller 21 is brought into contact with the pressure roller 15 is D. By satisfying the relationship of D2> D1 ≧ (D2−D), the arc-shaped surface of the bearing 25 is brought into contact with the pressure roller 15.

In this manner, the amount of toner collected by the cleaning roller 21 increases, and even if the toner protrudes from the nip N 'formed by the pressure roller 15, the toner is pressed against the bearing 25 having an arc-shaped surface by the pressure. The toner flows into the nip N ″ formed by the roller 15, so that toner does not accumulate between the shaft of the cleaning roller 21 and the bearing 25 thereof.

As described above, the pressure roller surface side of the bearing 25 that receives the shaft of the cleaning roller 21 is formed in an arc shape, and the arc-shaped surface comes into contact with the pressure roller 15 so that the cleaning roller 21 flows into the bearing portion. The generated toner does not accumulate in the gap between the shaft of the cleaning roller 21 and the bearing 25, and the same effect as in the above-described embodiment can be obtained.

[Fifth Embodiment] Next, a fifth embodiment of the image fixing apparatus will be described.
An embodiment will be described with reference to FIG. In this embodiment, the description of the same parts as those of the first embodiment will be omitted, and the shape and effects of the cleaning roller, which are features of the present embodiment, will be described.

When the amount of toner collected from the pressure roller 15 in the cleaning area A1 increases, the force applied to the toner at the nip N 'formed by the pressure roller 15 increases, and the toner is pushed out and protrudes. It is at the longitudinal end of the cleaning roller 21 that the toner can protrude from the nip N '.

On the other hand, the longitudinal shape of the cleaning roller 21 has a shape conforming to the longitudinal shape of the pressure roller 15 in order to further improve the adhesion to the pressure roller 15 and improve the toner collecting property. I have. Usually, the shape of the pressure roller 15 in the longitudinal direction is an inverted crown shape whose outer diameter is larger at the end than at the center, as shown in FIG. 8, for the purpose of preventing wrinkling of the recording material.

Therefore, the cleaning roller 21 may have a crown shape in which the diameter at the center is larger than the end in the longitudinal direction in order to match the shape of the pressure roller 15. Therefore, when the amount of the collected toner on the cleaning roller increases and the toner overflows, the toner is pushed out from the center of the cleaning roller to the end, and finally overflows from the end of the cleaning roller to the bearing 22.

Therefore, in the present embodiment, as shown in FIG. 8, the longitudinal shape of the cleaning roller 21 is determined based on the boundary between the cleaning area A1 which is an image forming area and the non-cleaning area A2 outside the cleaning area A1. It was configured as follows.

That is, the cleaning area A1 is formed into a curved shape in which the outer diameter Dc at the center is larger than the outer diameter Dp at the boundary line position, thereby enhancing the adhesion to the pressure roller 15. In the non-cleaning area A2, the outer diameter De of the longitudinal end is determined.
Is formed into a curved shape larger than the outer diameter Dp at the boundary line position to prevent the toner collected from the cleaning roller 21 from protruding, so that the toner flows into and accumulates on the shaft of the cleaning roller 21 and the bearing 22 receiving the same. Is preventing that.

As described above, the longitudinal shape of the cleaning roller 21 is such that the cleaning area A1 has a shape that further enhances the cleaning property, and the non-cleaning area A2 has a shape that prevents the toner from protruding from the cleaning roller 21. The toner does not flow from the bearing 21 to the bearing 22, so that the cleaning roller 21 and the pressure roller 15 always rotate smoothly, thereby preventing the recording material from being jammed due to the recording material not being transported smoothly in the fixing nip portion. It is possible to do.

[Other Embodiments] Each of the above-described embodiments is
Although the effects have been described alone, the cleaning roller 21 can be configured by combining the configurations of the respective embodiments.
The effect of preventing the adverse effects caused by the collected toner flowing into the shaft of the cleaning roller 21 and its bearing and being hardened and accumulated may be enhanced.

In the above-described embodiment, a printer is described as an example of an image forming apparatus having an image fixing device. However, it is obvious that the present invention can be applied to a copying machine, a facsimile machine, and the like.

[0085]

The present invention is constructed as described above.
The toner collected on the cleaning rotator is prevented from flowing in the axial direction of the cleaning rotator by the large-diameter portion, and therefore does not flow to a support member such as a bearing of the cleaning rotator. Therefore, the cleaning rotator always rotates smoothly, and the fixing rotator also rotates smoothly, so that the occurrence of clogging of the recording material in the fixing unit can be prevented.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view illustrating a pressure roller and a cleaning roller according to a first embodiment.

FIG. 2 is an overall schematic diagram of the image forming apparatus.

FIG. 3 is a schematic explanatory view of an image fixing device.

FIG. 4 is an explanatory diagram showing a relationship between longitudinal dimensions of a pressure roller and a cleaning roller.

FIG. 5 is an explanatory diagram of a bearing of a cleaning roller according to a second embodiment.

FIG. 6 is an explanatory diagram of a cleaning roller support structure according to a third embodiment.

FIG. 7 is an explanatory diagram of a cleaning roller support configuration according to a fourth embodiment.

FIG. 8 is a schematic sectional view illustrating a pressure roller and a cleaning roller according to a fifth embodiment.

FIG. 9 is an explanatory diagram of a configuration of an image fixing device according to a conventional technique.

FIG. 10 is a diagram illustrating a state in which cleaning toner flows into a bearing unit.

[Explanation of symbols]

 A: Laser beam printer A1: Cleaning area A2: Non-cleaning area B: Image fixing device L: Laser beam N: Fixing nip P: Recording material T: Unfixed toner 1 ... Main body 2 ... Feeding cassette 3 ... Feeding roller Reference Signs List 4 separation roller pair 5 guide member 6 registration roller pair 7 process cartridge 7a photosensitive drum 7b primary charging roller 7c developing unit 7c1 toner container 7c2 developing roller 7d cleaning device 8 scanner unit 9 Transfer roller 10 ... Conveying guide 11 ... Discharge roller pair 12 ... Discharge tray section 13 ... Fixing roller 13a ... Core metal 13b ... Release layer 14 ... Heater 15 ... Pressurizing roller 15a ... Core metal 15b ... Elastic layer 15c ... Release layer 16… DC power supply 17… Pressure diode element 18… Inlet guide 19… Thermistor 20… Fixing separation claw 21… Cleaning Over La 21a ... large diameter portion 22 ... bearing 22a, 22b ... tip 23 ... spring spring 24 ... bush 25 ... bearing

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tomio Noguchi 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Hiroshi Yummachi 3-30-2 Shimomaruko, Ota-ku, Tokyo Non-corporation F term (reference) 2H033 AA08 AA23 BA49 BA55 BA56 BB33 BB36 3J103 AA02 AA74 CA62 CA78 FA21 GA02 GA64

Claims (7)

[Claims] 1. A recording material onto which an unfixed toner image has been transferred passes between a pair of fixing rotators, and the toner image is fixed on the recording material by heating and pressing, and the surface of the fixing rotator is fixed on the recording material. In an image fixing apparatus in which a cleaning rotator is brought into contact with at least one of the fixing rotators to clean the attached toner, the cleaning rotator has a longer effective area length in the longitudinal direction than the fixing rotator. An image fixing device characterized by having a large-diameter portion having an outer diameter of 130 to 200% of the outer diameter of the cleaning effective area in the cleaning non-effective area. 2. The image fixing device according to claim 1, wherein the large diameter portion is formed at both ends in a longitudinal direction of the cleaning rotator. 3. A recording material on which an unfixed toner image has been transferred is passed between a pair of fixing rotators, and the toner image is fixed on the recording material by heating and pressing, and the surface of the fixing rotator is fixed. An image fixing device in which a cleaning rotator is brought into contact with at least one fixing rotator to clean the adhered toner, wherein the cleaning rotator is supported by a U-shaped support member, and the U-shaped The image fixing device according to claim 1, wherein the tip of the cleaning rotator on the upstream side in the rotation direction is formed at an acute angle with respect to the contact position between the fixing rotator and the cleaning rotator. 4. A recording material on which an unfixed toner image has been transferred is passed between a pair of fixing rotators, and the toner image is fixed on the recording material by heating and pressing, and the surface of the fixing rotator is fixed. In an image fixing apparatus in which a cleaning rotator is brought into contact with at least one fixing rotator in order to clean the adhered toner, the cleaning rotator is supported by a supporting member, and a shaft of the cleaning rotator and a supporting member are provided. An image fixing device, wherein sliding bearings rotatable with each other are provided therebetween. 5. A recording material on which an unfixed toner image has been transferred passes between a pair of fixing rotators, and the toner image is fixed to the recording material by heating and pressing, and the surface of the fixing rotator is fixed. In an image fixing device in which a cleaning rotator is brought into contact with at least one fixing rotator in order to clean the adhered toner, the cleaning rotator is supported by a support member, and a support member for supporting the cleaning rotator is provided. The outer peripheral surface is an arc, the radius is D1, and the radius of the cleaning rotating body is D.
2. When the amount of deformation of the fixing rotator caused by the contact of the cleaning rotator with the fixing rotator is D, the relationship of D2>D1> (D2-D) is satisfied. Image fixing device. 6. A recording material on which an unfixed toner image has been transferred passes between a pair of fixing rotators, and the toner image is fixed to the recording material by heating and pressing, and the surface of the fixing rotator is fixed. In an image fixing device in which a cleaning rotator is brought into contact with at least one fixing rotator in order to clean the adhered toner, the cleaning rotator has a longer longitudinal direction than the fixing rotator, and In the longitudinal direction of the cleaning effective area where the cleaning rotator and the fixing rotator contact each other, the outer diameter at the end of the effective area is made smaller than the outer diameter at the central part of the effective area. An image fixing device, wherein an outer diameter of an end portion in a longitudinal direction of a rotating body is made smaller. 7. An image forming apparatus for forming an image by transferring a toner image formed on an image carrier to a recording material, wherein the image forming means forms toner on the image carrier and transfers the toner image to the recording material. An image forming apparatus, comprising: a fixing device according to claim 1 for fixing the toner image to a recording material.