JPH0748124B2 - Fixing device for image forming apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Object of the Invention (Industrial field of application) The present invention relates to a fixing device suitable for use in an image forming apparatus utilizing an electrostatic recording process such as an electrostatic copying machine and a printer. Is.

(Problems to be Solved by Prior Art) As well known in image forming apparatuses such as electrostatic copying machines, electrostatic attraction is a problem in forming a toner image on a sheet-like transfer material such as paper. It is necessary to fix and fix the toner image on the surface of the transfer material formed with such a weak force.

As fixing means for this purpose, some means have been proposed in the past, but there are a fixing roller whose surface is maintained at a predetermined temperature, and a pressure roller which is formed by an elastic member on the surface and is brought into pressure contact with the fixing roller. A fixing device that allows a transfer material carrying an unfixed toner image to pass through the pressure contact nip portion of the roller pair made of and applies heat and pressure to the transfer material to fuse and fix the toner to the transfer material. It is in practical use.

In such a fixing device, a part of the toner adheres to the fixing roller during fixing, and this adheres to a transfer material supplied to the fixing device thereafter, which may cause deterioration of image quality. A cleaning web impregnated with an appropriate release agent, a rod-shaped felt, or the like is continuously brought into contact with the fixing roller to remove the toner attached to the roller, and the release agent is attached to fix the toner. It is usually designed to prevent toner from adhering to the fixing roller during operation.

Further, during fixing, since the toner softens and becomes viscous, the transfer material tends to adhere to the fixing roller even after fixing.Therefore, use a sharp tip of a separation claw made of an appropriate material such as a synthetic resin material. It is widely known that the transfer material is positively separated from the fixing roller by contacting the fixing roller at the position after fixing.

Since such a separating claw is hard, the surface of the fixing roller is easily damaged, and the toner adhered to the roller is adhered and solidified at the tip of the separating claw to reduce the peeling function of the transfer material. I wasn't killed.

Therefore, in order to avoid such a defect, there has been proposed one in which the separation claw is brought into contact with and separated from the fixing roller, and the contact is limited to the time when the transfer material is present. May damage the tip of the nail and the fixing roller due to the impact when it comes into contact with the roller. Furthermore, if sufficient release agent is not present on the surface of the fixing roller, insufficient lubrication may cause the nail to move. It may cause damage to the tip or roller surface.

The present invention has been made to cope with such a situation, and in the fixing device as described above, the tip of the separation claw that comes into contact with and separates from the fixing roller, the surface of the fixing roller is damaged, and the tip of the claw is dirty. It is an object of the present invention to provide a fixing device which can be prevented as much as possible and can always obtain a stable fixing function.

(2) Configuration of the Invention (Technical Means for Solving the Problem and Its Action) In order to achieve the above object, the present invention provides a fixing device including a heat fixing roller and a pressure roller in pressure contact therewith. The separation claw is brought into contact with and separated from the fixing roller according to the presence / absence of the transfer material in the portion, and the contacting / separating operation and the supply of the release agent to the fixing roller are configured to be linked with each other. It is characterized in that the speed of contact is slowed.

With this configuration, the separation claws always come into contact with the fixing roller in a state where a sufficient amount of the release agent is present, and the claws do not come into shock contact with the fixing roller. The damage can be prevented and the tip of the separation claw can be prevented from getting dirty.

(Description of Embodiments) FIG. 1 is a side cross-sectional view of a main part of an embodiment showing a fixing device portion according to the present invention in an image forming apparatus such as an electrostatic copying machine. In addition, a fixing roller 1 provided with an appropriate heat source 3 such as a heater and a pressure roller 2 arranged substantially parallel to the fixing roller 1 are provided. The fixing roller 1 has a releasing property for toner on the surface of the core metal 1a. A good fluororesin layer 1b is formed, the temperature detecting means 5 detects the temperature of the roller, and the control means (not shown) controls the heat source 3 to maintain the surface temperature at a predetermined level.

The pressure roller 2 is composed of a core metal 2b and an elastic layer 2a formed on the surface of the core metal 2b and made of a heat resistant elastic material such as silicon rubber. Both end bearing portions (not shown) of the pressure roller 2 are fixed by springs 14. The elastic layer 2a of the pressure roller is pressed against the fixing roller because it is supported by the support member 13 which is biased in the roller direction, and the nip portion n having a proper length in the left-right direction in the drawing is provided.
Is formed.

In the image forming unit (not shown), the transfer material P carrying the toner image advances to the left with the toner image on the upper side in the drawing to reach the fixing device, passes through the nip portion n, and heat and pressure are applied. After receiving the toner, the toner is fixed and fixed on the transfer material, and then discharged through the conveyance path 17 by the discharge roller pair 15 to the outside.

A cleaning mechanism 4 is arranged near the fixing roller 1.

The cleaning mechanism comprises a winding roller 4a and a supply roller 4b arranged in parallel with the fixing roller 1, and is composed of a non-woven fabric formed of, for example, an aromatic polyamide fiber between them, such as silicone oil. A cleaning web W impregnated with a release agent is suspended.

The elastic pressing roller 4c is provided at a position between the rollers 4a and 4b.
This roller is pressed against the fixing roller 1 through the web W to bring the web W into contact with the fixing roller 1, and the winding roller is driven by an appropriate drive source (not shown). 4a is rotated, and the surface of the fixing roller is rubbed while sequentially winding up the web W to supply the release agent thereto and remove the adhered toner.

An arm 6 is attached to one of the projecting ends of the winding roller 4a via a one-way clutch 6a, so that when the arm 6 rotates clockwise in the drawing, this rotation is transmitted to the shaft 4a. When the web W is wound up and rotated in the counterclockwise direction, the shaft 4a is prevented from rotating, and the arm 6 is pressed by a spring 7 against a cam 8 arranged at a fixed position in the fixing device. is doing.

A separating claw 10 is pivotally attached to a shaft 10a arranged at a proper position in the device, and a separating claw control member 9 is pivotally attached to the shaft 10a. A turning habit is given in the counterclockwise direction by 12, and one end 9b thereof is provided.
Is in contact with the cam 8.

One end of the separating claw 10 is engaged with the other end of the spring 11 whose one end is locked to the control member 9, whereby the tip of the separating claw is attached to the fixing roller 1. Direction, and thus the other end of the control member 9
9a is in contact with the separating claw 10.

As shown in the figure, the cam 8 has the same diameter r ₁ from the point P1 to the point P2, and gradually has the diameter r ₁ to r ₂ from the point P2 to the point P3.

The operation of the fixing device having the above configuration will be described below.

FIG. 1 shows a state in which the fixing device is in a standby state before starting the operation.

At this position, the cam 8 has a small diameter point P2.
A portion in the vicinity is in contact with the end portion 9b of the separation claw control member 9, and a portion in the vicinity of the point P3 having a large diameter is in contact with the arm 6.

At this time, the member 9 is in an extreme position where it rotates clockwise, and the end 9a of the member 9 contacts the separation claw 10 to maintain it at a position separated from the fixing roller 1.

At the image forming portion (not shown), the transfer material carrying the toner image advances toward the fixing device along the conveying path 16,
When a suitable detecting means 18 such as a micro switch detects the presence of the transfer material, the cam 8 is rotated counterclockwise in the drawing by a driving source (not shown).

When the cam rotates, the member 9 starts rotating in the counterclockwise direction in the drawing, and the end 9a of the member 9 separates from the separating claw.
It is also assumed that 10 also rotates counterclockwise so that its tip approaches the fixing roller 1, and the transfer material comes into contact with the fixing roller before reaching the nip portion n of both rollers.

FIG. 2 shows the state of each part at this time.

From the position shown in FIG. 1 to the position shown in FIG.
As can be seen from the figure, since the cam 8 only reaches from the large diameter portion to the small diameter portion, the spring 7 slightly rotates counterclockwise in the figure, but at this time the crack 6a does not operate, so cleaning is performed. Mechanism 4 has no effect.

When the cam 8 is rotated from the state shown in FIG. 2 to the state shown in FIG. 3, the member 9 is further rotated counterclockwise in the figure, and the separation claw 10 is kept in contact with the fixing roller. Then, the transfer material passing through the nip portion n exerts a separating action.

After the transfer material leaves the nip portion n, the cam 8 further rotates to reach the position shown in FIG.

As a result, the member 9 is rapidly displaced from the large-diameter portion of the cam to the small-diameter portion thereof, so that it is rotated clockwise by the action of the spring 12, and its end portion 9a engages with the separating claw 10 to move it. By rotating it in the clockwise direction, the tip end thereof is quickly separated from the fixing roller, and the position is maintained while coming into contact with the radius r ₁ portion of the cam 8 thereafter.

On the other hand, since the arm 6 is in the area where the diameter of the cam 8 is gradually increased, the arm 6 is rotated along with the rotation of the cam.
Will rotate clockwise in the figure.

When the arm 6 rotates as described above, the winding shaft 4a rotates clockwise in the drawing via the one-way clutch 6a to wind up the web W, and the surface of the fixing roller is cleaned by the web via the roller 4c. At the same time, a release agent such as silicone oil is applied to this.

When the cam 8 further rotates and reaches the position shown in FIG. 1 again, the drive source for driving the cam stops and maintains the position until the next transfer material is detected by the detecting means 18.

The above operation is briefly described from the side of the fixing roller, the separating claw, and the cleaning web. By the end of the immediately preceding fixing step, a sufficient releasing agent is present on the surface of the fixing roller. Under the condition, the arrival of the transfer material is detected, and first, the separation claw slowly comes into contact with the fixing roller.

After that, the separation claw maintains its operating position and performs the separation operation while fixing is performed.

When the transfer material passes, the separating claw is rapidly separated from the fixing roller, and thereafter maintains its retracted position.

During this time, the cleaning web rubs against the surface of the fixing roller, and the release agent is supplied to the surface of the fixing roller for the next step.

Since the separating claw does not impactly contact the fixing roller due to the structure and operation as described above, the separating claw abuts the place where the release agent is insufficient, and the separating claw is caused by poor lubrication. It prevents damage to the tip and the fixing roller, and the separation claw contacts the fixing roller only when necessary, and there is sufficient release agent at the time of contact, so toner accumulates at the tip of the claw and the image quality deteriorates. Can be prevented.

FIGS. 5 to 8 show another embodiment of the present invention, in which the fixing device itself has basically the same structure as that of the above-mentioned embodiment, and the corresponding parts are the same. They are indicated by the reference numerals, and the description thereof will be omitted unless particularly necessary.

As can be seen from FIG. 5, in this apparatus, one end of the lever 20 is pivotally attached to the shaft 20a provided at a fixed position in the apparatus above the fixing roller 1 in the drawing, and the lever has heat resistance. A cleaning member 21 in which a felt is impregnated with a release agent such as silicon oil is attached to a position facing the fixing roller.

The other end of the lever 20 reaches the cam 8 and the pressing spring 22
Is pressed against the cam.

As can be understood from the position of the cam, FIG. 5 is in the rest state as in the case of FIG. 1 described above.
The cleaning member 21 is located away from the fixing roller 1.

When the transfer material carrying the toner image is detected by the detecting means 18, the cam 8 is rotated counterclockwise as indicated by an arrow in FIG. Along with this, the separating claw control member 9 and the separating claw are brought into contact with and separated from the fixing roller to perform a separating action. The action of the separating claw is the same as in the case of the above-mentioned embodiment, so that it is omitted, and only the operation of the cleaning member will be described below.

When the cam 8 rotates counterclockwise from the position shown in FIG. 5 to the position shown in FIG. 6, the lever 20 is rotated counterclockwise by the action of the spring 22 while being in contact with the cam 8. The cleaning member 21 that moves and is attached thereto is pressed against the fixing roller 1.

At this time, the separating claw 10 slowly contacts the fixing roller by the action of the cam, and the lever 20 rubs the fixing roller for a predetermined time while contacting the position of the radius r ₁ of the cam to clean the surface thereof. A release agent will be added.

Such a state continues until the cam 8 further rotates and reaches the position shown in FIG.

FIG. 7 shows that the lever 20 takes the final position of the same diameter portion of the cam 8 and the separation claw control member 9 is at the maximum diameter portion.

When the cam 8 rotates from the position shown in FIG. 7 to the position shown in FIG.
Since the control member 9 rapidly moves from the large-diameter portion to the small-diameter portion of the cam, the separation claw 10 also quickly retreats from the fixing roller 1 along with this, while the lever 20 also changes the diameter of the cam. Then, the cleaning member 21 is rotated clockwise to separate the cleaning member 21 from the fixing roller.

After that, the control member 9 comes into contact with the small diameter portion of the cam, so that the separating claw maintains the retracted position in the figure, and the lever 20 gradually moves away from the roller, and the whole reaches the position in FIG. Sometimes the cam stops and takes the rest position shown in the figure.

It will be immediately understood that this device can perform similar functions to those described above.

(3) Effects of the Invention As described above, the fixing device according to the present invention is a fixing device including a fixing roller and a pressure roller that comes into pressure contact with the fixing roller. Since it is linked to the release agent supply to prevent it, separation claws due to insufficient lubrication due to lack of release agent,
Prevents damage to the fixing roller, and effectively prevents the toner on the edge of the separation claw and the contamination of the transfer material due to the contact with the separation claw only when the separation claw comes into contact with the fixing roller. By slowing down the displacement speed in the abutting direction, it is possible to prevent damage to the separation claw end and the fixing roller due to impact, and it is possible to perform the fixing and separation work in a good state when passing through the fixing device. It greatly contributes to obtaining good quality images.

[Brief description of drawings]

1 to 4 are side views of a main part of a fixing device showing an embodiment of the present invention and a diagram showing its operation, and FIGS. 5 to 8 show fixing means showing another embodiment of the present invention. FIG. 3 is a side view of a main part and a diagram showing its operation. 1 ... Fixing roller, 2 ... Pressure roller, 4 ... Cleaning mechanism, 6 ... Arm, 8 ... Cam, 9 ... Separation pawl control member, 10 ... Separation pawl, 18 ... Transfer material detection means , 20 ……
Lever, 21 ... Cleaning member, W ... Cleaning web.

Claims (2)

[Claims] 1. A fixing roller, the surface of which is maintained at a predetermined temperature, and a pressure roller, which is brought into pressure contact with the fixing roller, and a transfer material carrying a toner image is allowed to pass through a pressure contact nip portion between the both, and the fixing is performed. In a fixing device provided with cleaning means for holding a release agent near the roller and transfer material separating means, the transfer material separating means has a first position separated from the fixing roller and a second position abutting on the first position. The fixing device is configured to be reciprocally movable between the fixing device and the fixing device, and the displacement speed in the direction of contact with the fixing roller is smaller than the displacement speed in the direction of separating. 2. The fixing device according to claim 1, wherein the cleaning unit is configured to perform cleaning only when the transfer material separating unit is in the second position.