JPH083689B2 - Fixing device for image forming apparatus - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device provided in an image forming apparatus such as an electrostatographic copying machine or a facsimile, and more specifically, to a peripheral surface of a fixing rotating body. The present invention relates to improvement of a technique for peeling off adhered paper.

[Conventional technology]

As a fixing device of the image forming apparatus, for example, Japanese Patent Laid-Open No.
As seen in -204072 publication and also shown in FIG.
An upper heat-fixing rotator 41 and a lower pressure-fixing rotator 42 are arranged, and the upper fixing rotator 41 is provided.
A sheet peeling claw 43 for peeling the fixed sheet adhered to the peripheral surface of the rotating body 41 from the peripheral surface of the rotating body 41, a tangent line R ₁ passing through a contact point Q ₁ of the sheet separating edge h of the rotating body peripheral surface S ₁ to the peripheral surface S _1. The paper peeling edge h is provided by a spring 44 so as to be swingable around an axis P ₁ closer to the rotating body than the peripheral surface S _{1 of the} rotating body.
There is one that is provided so as to urge and abut.

According to the fixing device having the above configuration, when the sheet after fixing adheres to the peripheral surface S ₁ of the fixing rotator 41 on the upper side, the sheet is picked up by the sheet peeling claw 43 so that the rotator Since it is peeled off from the peripheral surface S _1, so-called paper jam around the peripheral surface S ₁ of the rotating body is effectively prevented.

Alternatively, a sheet of paper may enter between the sheet peeling claw 43 and the peripheral surface S ₁ of the rotating body, or the tip of the sheet adhered to the peripheral surface S _{1 of the} rotating body may be strongly pressed against the sheet peeling edge h of the sheet peeling claw 43. When hitting or applying an excessive load to the tip side of the paper peeling claw 43, the paper peeling claw 43 is around the axis P _{1 on the} rotating body side with respect to the tangent R ₁ passing through the contact point Q _1. Since it is swingable, the paper peeling edge h of the paper peeling claw 43 swings freely from the peripheral surface S _{1 of the} rotating body by the action of the load, and as shown in FIG. When the point Q ₂ of urging force of the spring 44 with respect to the claw 43 exceeds the dead point line V, the sheet peeling claw 43 rotates and separates from the rotating body circumferential surface S ₁ , thereby peeling the sheet. A situation in which the edge h bites into the peripheral surface S _{1 of the} rotating body is prevented.

[Problems to be solved by the invention]

However, by the time the biasing point Q _{2 of the} spring 44 exceeds the dead point line V,
Since the urging force of the sheet 44 is gradually increased, smooth swinging of the sheet peeling claw 43 cannot be expected.
The paper is strongly stuck between 43 and the peripheral surface S _{1 of the} rotating body,
Alternatively, while the paper peeling claw 43 is separated from the peripheral surface S _{1 of the} rotator, the paper forcibly discharged by the upper and lower fixing rotators 41, 42 is accordion-shaped near the tip of the paper peeling claw. It had the drawback of jamming.

Moreover, when the biasing point Q _{2 of the} spring 44 exceeds the dead point line V, the paper peeling claw 43 completely loses the paper peeling function, and the paper peeling after that can be completed. Therefore, it is necessary to provide a mechanism for detecting such a state, and to return the sheet peeling claw 43 to the initial state based on the information from the mechanism, which requires time to restart the operation and cost. There was also a drawback that led to ups.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a fixing device in which the above drawbacks are alleviated at once in spite of an extremely simple improvement.

[Means for solving problems]

The fixing device of the image forming apparatus according to the present invention for achieving the above object is provided with a paper peeling claw for peeling the paper adhered to the peripheral surface of the fixing rotary body from the peripheral surface of the rotary body. The edge is provided so as to be swingable around an axis line on the rotor side with respect to a tangent line passing through the contact point with the peripheral surface of the rotor, and the guide end portion near the horizontal line passing through the swing axis and on the downstream side in the paper discharge direction is A guide groove located slightly below the guide end near the swing axis is formed in the paper peeling claw, while a weight for biasing the paper peeling edge against the peripheral surface of the rotating body is provided along the guide groove. It is characterized in that it is reciprocally movable.

[Action]

According to the above characteristic configuration, when an excessive load is applied to the tip end side of the sheet peeling claw, the sheet peeling claw is swingable around the axis on the side of the rotating body with respect to the tangent line passing through the contact point. As before, the paper peeling edge of the paper peeling claw swings freely from the peripheral surface of the rotating body by the action of the load.

A weight is used to urge the paper peeling edge of the paper peeling pawl toward the peripheral surface of the rotating body, and the weight is positioned near the horizontal line, so that the paper peeling pawl rotates. The biasing force of the weight applied to the paper peeling claw hardly fluctuates when swinging away from the body surface without permission, or the biasing force is applied when the weight is arranged above the horizontal line. Moreover, when the paper peeling claw swings slightly in the separating direction, the weight moves to the swing axis side along the guide groove, so that the biasing force of the weight applied to the paper peeling claw is increased. Is extremely reduced.

Then, the paper is strongly pressed against the tip side of the paper peeling claw, or the paper enters between the paper peeling claw and the peripheral surface of the rotating body, so that an excessive load is applied to the tip side of the paper peeling claw. In this case, a predetermined urging force that urges and abuts the paper peeling edge against the peripheral surface of the rotating body is exerted in the initial stage of the swing, but after that, the paper peeling claw easily swings away from the peripheral surface of the rotating body. Therefore, the paper is not overloaded, so that the paper is not jammed in a so-called accordion shape and is not strongly pressed between the paper peeling claw and the peripheral surface of the rotating body. The occurrence of the jam itself is suppressed by shifting to the downstream side in the paper discharge direction with the swing of the paper.

Then, when the load on the paper peeling claw is released, such as when the paper passes through the paper peeling claw portion, the paper peeling claw returns to the initial paper peeling posture and swings. In the range up to near the winter season, since the weight is located near the swing axis, the urging force of the weight exerted on the paper peeling claw before reaching the end of the swing is small, and The weight is moved to the guide end portion on the downstream side in the paper discharge direction by the subsequent swinging movement of the paper peeling claw, and a predetermined biasing force is applied to the paper peeling edge of the paper peeling claw. Since the application of the force is delayed a little after the return swing of the paper peeling claw to the initial paper peeling posture, the paper peeling edge of the paper peeling claw softly abuts the peripheral surface of the rotating body, and then the paper peeling is performed. Predetermined biasing force on the edge Now it is given, by Thus,
The peripheral surface of the rotating body is effectively prevented from being scratched by the paper peeling edge of the paper peeling claw.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 2 shows an electrostatographic copying machine as an example of an image forming apparatus,
The photoconductor 3 is mounted horizontally on the main body 2 of the document holder 1, and the charging device 4, the developing device 5, the transfer device 6, the paper separating device 7, and the cleaning device 8 are provided around the photoconductor 3. , Are arranged in that order in the rotation direction of the photoconductor 3, and
In the upper space of the apparatus main body 2, an optical system movable exposure apparatus 9
Is provided, and the manual feed section 10 or cassette case 11
A sheet feeding and conveying device 12 that conveys the sheet a from the sheet feeding device, a sheet discharging and conveying device 14 that conveys the separated sheet to the fixing device 13, and sheet discharging rollers 16 and 17 that discharge the fixed sheet to the tray 15. It is made up of pairs.

The fixing device 13 and the paper discharge rollers 16 and 17 are unitized and can be inserted into and removed from the apparatus main body 2 and have the following configuration.

That is, as shown in FIG. 1, the fixing case 21 is pivotally connected to a lower fixing case 19 mounted on a unit receiver 18 on the main body side of the apparatus via a support shaft 20 of a discharge roller 17 on the lower side. In addition, a rotary body for heat fixing on the upper side (for example, a heater 23 is built in a roller body 22 made of metal such as aluminum whose peripheral surface is coated with a fluorine-based resin b) 24 and the upper side The paper discharge roller 16 is pivotally attached to the upper fixing case 21, and a pressure-fixing rotating body on the lower side (for example, a thick elastic cylindrical body 25 such as silicon rubber is a roller made of metal such as aluminum). While being mounted on the main body 26) 27 is pivotally attached to the lower fixing case 19, a pair of upper and lower paper discharge guides are provided between the pair of fixing rotary members 24 and 27 and the paper discharge rollers 16 and 17. 28 and 29 are provided, and the sheet after the fixing is the peripheral surface S of the heat fixing rotator 24 on the upper side. When attached, and provided with a sheet peeling device 30 for peeling the sheet from the rotating body peripheral surface S to the lower fixing case 19.

Next, a specific structure of the paper stripping device 30 will be described. As shown in FIG. 3, this paper is provided with an upper paper discharge guide 28 having an upstream side portion in the sheet feeding direction curved upward.
The openings 31 are formed at predetermined intervals in the longitudinal direction (axial directions of the rotating bodies 24, 27), and the brackets 32 are erected on both sides of the openings 31, while the edge e on the lower swing end side is formed. A sheet peeling claw 33 for peeling the sheet adhered to the circumferential surface S of the fixing rotator 24 is attached to the bracket 32, and the sheet peeling claw 33 swings. Axis P
Is set to a position closer to the rotor 24 than a tangent line R passing through the contact point Q of the sheet peeling edge e of the sheet peeling claw 33 with respect to the rotating body peripheral surface S, and a horizontal line passing through the swing axis P. A guide groove having a long hole is formed in the paper peeling claw portion in the vicinity of T and immediately downstream of the swing axis P in the paper discharge direction.
34 is formed.

More specifically, the guide groove 34 has a long hole configuration.
The extension line U of the long hole axis of the above passes through the swing axis P, and
The guide end c on the downstream side in the paper discharge direction is formed so as to be located slightly below the guide end d near the swing axis P, and in the embodiment, the horizontal line T and the extension line U are formed. The angle is about 5 degrees.

A reciprocally movable weight W is provided along the guide groove 34 having the above-described structure so that the sheet peeling edge e of the sheet peeling claw 33 is urged and brought into contact with the peripheral surface S of the rotating body.

The lower edge f of the sheet peeling claw 33 is slightly curved upward, and a stopper g with which the leading edge of the sheet abuts is provided on the upper side of the curved edge f and in the vicinity of the sheet peeling edge e. Has been formed.

Furthermore, when the paper peeling claw 33 swings largely in the direction of separating from the peripheral surface S of the rotating body, and the paper peeling edge e of the paper peeling claw 33 comes out of the upper paper discharge guide 28, it is further increased. A stopper 35 for preventing the paper peeling claw 33 from swinging is provided in the apparatus main body 2.

According to the above configuration, the weight W is guided by its own weight to the guide end portion c of the guide groove 34 on the downstream side in the sheet discharge direction.
Since the weight W applies a large biasing force to the sheet peeling edge e of the sheet peeling claw 33 when the sheet W is fixed to the peripheral surface S of the rotating body, The paper is peeled off from the peripheral surface S of the rotating body so as to be picked up by the paper peeling edge e, and the paper is moved up and down along the curved edge f on the lower side of the paper peeling claw 33. It is discharged between 29.

Then, when the front end of the paper after fixing is strongly pressed against the paper peeling edge e of the paper peeling claw 33, the paper peeling claw 33 is moved around the swing axis P by receiving the load of the pressing. The paper swings so as to be separated from the peripheral surface S of the rotating body, and the paper is discharged together with the paper peeling claw 33 toward the pair of paper discharge rollers 16 and 17.

On the other hand, as shown in FIG. 4, when a part of the width of the paper a after fixing enters between the paper peeling claw 33 and the peripheral surface S of the rotating body, the remaining portion of the paper a is fixed. Is peeled from the peripheral surface S of the rotating body by the other paper peeling claw 33, so that the part of the paper a is pulled in the paper discharge direction,
This pulling load is applied to the paper peeling claw 33. Alternatively, when the tip of a part of the paper comes into contact with the stopper g, the pressing load and the pulling load due to the contact are applied to the paper peeling claw 33.

Thus, as shown in FIGS. 5 and 6, the paper a
The paper peeling claw 33 is rocked around the rocking axis P based on the above load until the tip of the paper passing the paper peeling edge e of the paper peeling claw 33.

Along with the swing of the sheet peeling claw 33, the sheet peeling claw 33 concerned
The urging force of the weight W given to the above changes as follows.

That is, until the paper peeling claw 33 swings 5 degrees, the weight W remains at the guide end portion c of the guide groove 34 on the downstream side in the paper discharge direction. Almost never.

When the swing angle of the paper peeling claw 33 exceeds 5 degrees, the weight W starts to move along the guide groove 34 toward the guide end portion d side near the swing axis P, and the urging force is accelerated. Decrease to.

Therefore, after the swing angle of the sheet peeling claw 33 exceeds 5 degrees, the sheet peeling claw 33 swings easily with a light load, so that the sheet a is accordion jammed near the sheet peeling edge e. It is also possible to prevent the paper peeling claw 33 and the peripheral surface S of the rotating body from being strongly intruded.

On the other hand, the posture of the sheet a is changed so as to follow the lower sheet ejection guide 29, or the rear end of the sheet a passes the sheet peeling edge e of the swinging sheet peeling claw 33. When the load on the paper peeling pawl 33 is released, the paper peeling pawl 33 swings back to return to the initial posture, but the weight W is the guide end portion c on the downstream side in the paper discharge direction. Until the shift to the side, the weight W
There is almost no change in urging force.

Then, the weight W starts to move to the guide end portion c side on the downstream side in the paper discharge direction at the initial stage of the swing of the paper peeling claw 33 over the remaining 5 degrees, so that the urging force of the weight W increases at an accelerated rate. At the same time, the biasing force becomes maximum (initial state) when the weight W is positioned at the guide end portion c on the downstream side in the paper discharge direction, and the paper peeling claw is reached before the biasing force becomes maximum. The sheet peeling edge e of 33 contacts the peripheral surface S of the rotating body.

Then, after the sheet peeling edge portion e is softly contacted with the peripheral surface S of the rotating body, the biasing force of the weight W is applied to the sheet peeling edge e, so that the peripheral surface S of the rotating body is changed. The paper peeling edge e is effectively prevented from being scratched.

7 and 8 show another embodiment of the paper peeling claw 33.
In FIG. 7, the guide groove 34 is formed immediately below the swing axis P, and in FIG. 8, the guide groove 34 is formed immediately above the swing axis P. The thing
The guide groove 34 of the paper peeling claw 33 shown in FIG. 1 is moved in a substantially parallel manner.

In the embodiment, the heat fixing rotator 24 is illustrated as the rotator to which the paper peeling claw 33 is attached. However, the rotator 27 for pressure fixing may be the attachment target, or the upper and lower fixing rotators may be attached. The rotating bodies 24 and 27 may be attached.

Further, in the embodiment, an electrostatic photocopier was shown as the image forming apparatus, but other than that, a facsimile, a printer or the like can be targeted.

〔The invention's effect〕

As described above, according to the present invention, when an excessive load is applied to the tip side of the sheet peeling claw by the sheet attached to the peripheral surface of the rotating body, the sheet peeling claw sways from the peripheral surface of the rotating body and freely shakes. By moving, it is possible to prevent the paper peeling edge from biting into the peripheral surface of the rotating body as in the conventional case.

Then, when the paper peeling claw slightly swings, the weight of the paper peeling claw becomes extremely small, so that the paper peeling claw swings lightly. Prevents paper jams and accordion jams between the peripheral surface.

Moreover, when the above-mentioned load is eliminated, the paper peeling edge of the paper peeling claw softly and automatically abuts against the peripheral surface of the rotating body. It is possible to prevent scratches on the surface, eliminate the need for the conventional paper peeling claw to return to the initial posture, and, as a whole, can easily eliminate the drawbacks of the prior art by a simple improvement.

[Brief description of drawings]

FIG. 1 is a sectional view of a fixing device, FIG. 2 is a schematic vertical sectional side view of an electrostatographic copying machine as an example of an image forming apparatus, FIG. 3 is a side view of a sheet peeling device, and FIGS. Explanatory views showing the rocking state of the paper peeling claws with time, FIG. 7 and FIG. 8 are side views of the paper peeling claw of another embodiment, respectively. 9 and 10 are explanatory views of a conventional example. 24,27 …… Rotating body (heat fixing roller, pressure roller), 3
3 ... Paper peeling claw, 34 ... Guide groove, a ... Paper, c ...
... Guide end on the downstream side in the paper discharge direction, d ... Guide end near the swing axis, e ... Paper peeling edge, P ... Swing axis,
Q: contact point, R: tangent line, S: peripheral surface of rotating body, T:
Horizontal line, U ... Extension line, W ... Weight.

Claims (2)

[Claims] 1. A paper peeling claw for peeling a sheet adhered to the peripheral surface of a fixing rotator from the peripheral surface of the rotator, and a tangent line passing through a contact point of the paper peeling edge of the sheet peeling edge with respect to the peripheral surface of the rotator. It is provided so as to be swingable around the axis on the side of the rotating body, and the guide end near the horizontal line passing through the swing axis and on the downstream side in the sheet discharge direction is slightly lower than the guide end near the swing axis. A guide groove located on the paper peeling claw is formed on the paper peeling claw, and a weight for biasing the paper peeling edge against the peripheral surface of the rotating body is provided reciprocally along the guide groove. Fixing device for image forming apparatus. 2. The guide groove is a long hole, and an extension line of the long axis of the long hole passes near the swing axis line of the paper peeling claw. A fixing device for an image forming apparatus described in the item.