JPH0748046A - Image forming device - Google Patents

Abstract

PURPOSE:To provide an image forming device which can reduce the winding curl generated on a recording paper after fixation independently of the kind of the recording paper. CONSTITUTION:As for a pair of fixed transfer rollers 11f and 11g, a fixed transfer roller 11g is installed in a turnable manner on a lever L which can turn around the rotary shaft 11f1 of the fixed transfer roller 11f, and the position of the fixed transfer roller 11g swings on the periphery of the fixed transfer roller 11f by the turn of the lever L.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a laser beam printer, an LED printer and a copying machine.

[0002]

2. Description of the Related Art Conventionally, laser beam printers and LEDs
In an image forming apparatus such as a printer, a photosensitive drum carrying a latent image drawn by irradiating laser light or the like according to image information, a developing device for developing the latent image on the photosensitive drum, and a developed device An image recording means for transferring and recording an image on a recording material and a fixing device for fixing the transferred image on the recording material after recording are mainly used.

The recording material after the image transfer is guided to the fixing device by a guide member integrally held by the fixing frame. As shown in FIG. 11, the fixing device is equipped with a fixing roller 51 made of aluminum and a pressure roller 52 made of rubber which comes into pressure contact with the fixing roller 51. The fixing roller 51 includes a heater 53.
The temperature is kept at a predetermined temperature by a temperature sensor (not shown), and is rotatably held by a bearing (not shown) on the fixing frame, and the driving force is transmitted to rotate at a predetermined speed. The pressure roller 52 is arranged so as to face the fixing roller 51, and is pressed by a pressure spring (not shown) with a predetermined force to be driven to rotate. When the recording material P is nipped and conveyed by the fixing roller 51 and the pressure roller 52, heat and pressure are applied to melt the developer and fix the image.
The recording material P after the image fixing is conveyed by a pair of conveying rollers (hereinafter referred to as "fixing conveying roller pair") 54a and 54b provided on the downstream side of the fixing device, and further ejected outside the apparatus by a pair of discharge rollers (not shown). It is transported to and discharged.

[0004]

However, in the above-mentioned conventional example, as shown in FIG. 10, when the recording material P passes between the fixing roller 51 and the pressure roller 52 of the fixing device, It is known that the heating causes curling (hereinafter referred to as "curl") depending on the curvature of the fixing roller 51.

Therefore, as shown in FIG. 11, a pair of fixing / conveying rollers 54a, 54a,
A curl applied to the recording material P is suppressed by providing 54b and guiding the recording material P from the fixing roller 51 in the direction of peeling.

However, the amount of curling of the recording material P varies considerably depending on the type and thickness of the recording material P, and as described above, the recording material P is removed in the direction of peeling the recording material P from the fixing roller 51. There is a risk of curling in the direction opposite to the curvature of the fixing roller 51 when the sheet is guided. As a result, the stackability of the recording material after discharge may be deteriorated, and a sufficient load may not be obtained.

An object of the present invention is to solve the above-mentioned problems of the prior art and to provide an image forming apparatus capable of reducing the curling that occurs on a recording material after image fixing regardless of the type of the recording material. It is provided.

[0008]

A typical means for solving the above-mentioned problems of the prior art and applied to the embodiments described below is through an image carrier and a plurality of processes acting on the image carrier. Image forming means for forming an image, image recording means for recording the image formed on the image carrier on a recording material, and fixing means for fixing the recorded image of the recording material after image recording. And a fixing / conveying means for nipping and conveying the recording material after image fixing, and the fixing / conveying means is configured to be swingable so that the conveying direction of the recording material is variable from the fixing means. Is characterized by.

[0009]

According to the above means, the recording material which has passed through the fixing means changes the conveying direction of the recording material from the fixing means by swinging the position of the fixing conveying means according to the winding state. Be transported.

[0010]

【Example】

 [First Embodiment]

An image forming apparatus using the above means will be described below with reference to the drawings. In this embodiment, a laser beam printer will be used as the image forming apparatus. 1 is a cross-sectional view showing the structure of the fixing / conveying roller pair, FIGS. 2 and 3 are explanatory views showing the carrying operation of the fixing / conveying roller pair, and FIG. 4 is a cross-sectional view showing the schematic structure of the laser beam printer.
FIG. 3 is a cross-sectional explanatory view of a fixing device.

First, a schematic structure of a laser beam printer will be described with reference to FIGS. 4 and 5. Reference numeral 1 denotes a cassette in which cut sheets P mounted on the lower part of the apparatus are stacked and stored, and is detachably mounted on the apparatus main body. A feeding roller 2 picks up and feeds the uppermost sheet P. Denoted at 3 is a separation claw for separating the sheets P fed by the feeding roller 2 one by one. Reference numeral 4 is a sheet guide provided in the cassette 1, reference numerals 5 and 6 are conveyance guides on the apparatus main body side, and the sheet P fed by the feeding roller 2 is provided on the downstream timing roller pair 7a, 7b. To guide you.

The pair of timing rollers 7a and 7b are temporarily stopped, and the sheet P is conveyed to the image recording portion at a predetermined timing after the leading edge of the sheet is abutted to correct skew. A sheet detection sensor S is provided immediately in front of the timing roller pair 7a, 7b, and a detection signal of the sensor S controls rotation of the timing roller pair 7a, 7b and control of laser light emission timing. Done.

Reference numeral 8 denotes a photosensitive drum which is an image carrier,
A laser beam is emitted from the laser oscillator 9 according to the image information to form a latent image. Around the photosensitive drum 8, a process unit for forming an image on the drum surface by a plurality of processes is provided. For example, a charging roller that charges the photosensitive drum 8 and a developer (toner) on the latent image
And a cleaning device for removing residual toner after image transfer. The photosensitive drum 8 and the process unit are housed in a process cartridge C which is detachable from the main body of the apparatus.

Reference numeral 10 denotes a transfer roller which is arranged so as to face the photosensitive drum 8 and is in pressure contact with the drum surface. This transfer roller
A predetermined voltage is applied to the photosensitive drum 8 to transfer the toner image on the photosensitive drum 8.
The toner image is transferred to the sheet P when the sheet P passes through the space.

A fixing device 11 fixes the transferred image on the sheet P after the image transfer. Reference numerals 12a and 12b denote discharge guides for inverting the sheet P after the image fixing and guiding it to the discharge roller pair 13. Discharge roller pair
The sheet 13 is conveyed and is discharged and stacked face down (with the image surface facing downward) on a discharge portion 14 provided outside the apparatus.

The structure of the fixing device 11 will be described in detail with reference to FIG. The sheet P passing between the photosensitive drum 8 and the transfer roller 10 is guided to the fixing portion by an entrance guide 11b integrally attached to the fixing frame 11a of the fixing device 11. In the fixing section, a fixing roller 11c made of aluminum and a pressure roller 11d made of rubber are arranged in pressure contact with each other. A heater 11e is built in the fixing roller 11c and is heated to a predetermined temperature by a temperature sensor (not shown), and the driving force is transmitted to rotate the fixing roller 11c. The pressure roller 11d is pressed against the fixing roller 11c with a constant pressure by a pressure spring (not shown).
It is driven by the rotation of. A fixing separation claw 11h separates the sheet P wound around the fixing roller 11c and conveyed.

11f and 11g are a pair of fixing and conveying rollers,
The sheet P is provided in the vicinity of the fixing roller 11c and the pressure roller 11d and conveys the sheet P after image fixing to the downstream side. The fixing / conveying roller 11f is rotationally driven by transmitting a driving force, and the fixing / conveying roller 11g is brought into pressure contact with and rotationally driven. The fixing / conveying roller pair 11f,
11g, as shown in FIG. 1, the fixing conveying rollers 11g are rotatably attached to the pivotable lever L about an axis of rotation 11f ₁ of the fixing conveying roller 11f, the lever L
The position of the fixing / conveying roller 11g is configured to swing around the fixing / conveying roller 11f by rotating. The lever L is configured so as to project outward from the main body of the apparatus, and is configured so that the user can appropriately operate it as necessary. Alternatively, the lever L can be rotated by providing an operating means such as a solenoid (not shown).

Next, the sheet conveying operation by the fixing and conveying roller pair 11f and 11g will be described with reference to FIGS. First, when the sheet P largely curls in accordance with the curvature of the fixing roller 11c, as shown in FIG. 2, the lever L is lowered (rotated in the clockwise direction about the rotation shaft 11f ₁ ) to move from the fixing roller 11c. By guiding the sheet P in the peeling direction, the curl amount of the sheet P can be reduced.

When the sheet P curls in the direction opposite to the curvature of the fixing roller 11c, the lever L is raised (rotated counterclockwise about the rotation shaft 11f ₁ ) as shown in FIG. The curl of the sheet P can be reduced by guiding the sheet P so as not to be peeled off from the fixing roller 11c.

According to the above construction, by rotating the lever L in accordance with an arbitrary curl amount which varies depending on the material and thickness of the sheet P, the position of the fixing / conveying roller 11g is swung to reduce the curl. You can As a result, it is possible to prevent the sheet P from being caught or jammed (paper jam) due to the curl of the sheet P, and maintain stable transportability, and the sheet stackability in the discharge unit 14 is improved.

[Second Embodiment]

Next, another example of the image forming apparatus will be described with reference to FIG.
Will be described with reference to. Since the schematic configuration of the laser beam printer is the same as that of the first embodiment, the same members are designated by the same reference numerals and the description thereof is cited. The configuration of the fixing device will be mainly described below.

In the first embodiment, the fixing / conveying roller 11f on the pressure roller 11d side is swung about the fixing / conveying roller 11f on the same side as the fixing roller 11c. At this time, the fixing / conveying roller 11f may be a driving roller and the fixing / conveying roller 11g may be a driven roller. However, when the driving side and the driven side are opposite, the structure for swinging the driving side becomes complicated. Therefore, as shown in FIG. 6, the lever L is fixed to the fixing / conveying roller 11g.
The rotary shaft 11g ₁ is rotatably attached and the lever L is rotated so that the position of the fixing / conveying roller 11f is swung around the fixing / conveying roller 11g.

With the above structure, the curl reduction effect can be obtained as in the first embodiment with a simplified structure without swinging the driving roller.

[Third Embodiment]

Next, another example of the image forming apparatus will be described with reference to FIG.
~ It demonstrates with reference to FIG. Since the schematic configuration of the laser beam printer is the same as that of the first embodiment, the same members are designated by the same reference numerals and the description thereof is cited. The configuration of the fixing device will be mainly described below.

In this embodiment, a pair of fixing / conveying rollers 11f and 11g are supported so as to come into pressure contact with one end of an L-shaped lever L, and the lever L is rotated around a corner portion T of the lever L. Thus, the pair of fixing / conveying rollers 11f and 11g is configured to swing as a whole. By this, the amount of wrapping of the sheet P around the fixing roller 11c is changed. A lever guide G is provided on the rotary shaft 11f ₁ of the fixing / conveying roller 11f on the end side of the lever L so as to swing together with the fixing / conveying roller pair 11f, 11g. No matter where the 11g position is, the sheet P can be smoothly fixed to the conveyance roller pair.
It is configured to be able to lead to 11f and 11g.

The lever L is constructed so as to project outward from the main body of the apparatus, so that the user can operate it as needed. Alternatively, the lever L can be rotated by providing an operating means such as a solenoid (not shown).

Next, the sheet conveying operation by the fixing and conveying roller pair 11f and 11g will be described with reference to FIGS. First, when the sheet P largely curls according to the curvature of the fixing roller 11c, as shown in FIG. 8, the lever L is lowered (rotated clockwise around the corner T) to fix the sheet P to the fixing roller. The curl amount of the sheet P can be reduced by reducing the amount of wrapping around the sheet 11c and guiding the sheet P from the fixing roller 11c in the direction of peeling it off.

When the sheet P curls in the direction opposite to the curvature of the fixing roller 11c, the lever L is raised (rotated counterclockwise around the corner T) as shown in FIG. The curl of the sheet P can be reduced by increasing the winding amount of the sheet P around the fixing roller 11c and guiding the sheet P so as not to be peeled off from the fixing roller 11c.

In general, the sheet P that curls in the direction opposite to the curvature of the fixing roller 11c is thick and often has poor fixability. As in the present embodiment, the effect of improving the fixability is also obtained by increasing the winding amount of the sheet P around the fixing roller 11c in order to reduce the curl in the reverse direction.

Although the above embodiments have been described by using the laser beam printer as the image forming apparatus, the present invention is not limited to this, and other apparatuses such as a copying machine and an LED are used.
It may be a printer or the like.

[0034]

As described above, the present invention can reduce the winding amount by swinging the position of the fixing / conveying means according to an arbitrary winding amount which varies depending on the material and thickness of the recording material. it can. As a result, it is possible to prevent the recording material from being caught or jammed (paper jam) due to the curling of the recording material, to maintain stable transportability, and also to improve the stackability of the recording material at the discharge portion.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration of a fixing / conveying roller pair according to a first embodiment.

FIG. 2 is an explanatory diagram showing a sheet conveying operation of a pair of fixing and conveying rollers.

FIG. 3 is an explanatory diagram showing a sheet conveying operation of a fixing / conveying roller pair.

FIG. 4 is a cross-sectional view showing a schematic configuration of a laser beam printer.

FIG. 5 is a cross-sectional explanatory diagram of a fixing device.

FIG. 6 is a sectional view showing the structure of a fixing / conveying roller pair according to the second embodiment.

FIG. 7 is a cross-sectional view showing the configuration of a fixing / conveying roller pair according to the third embodiment.

FIG. 8 is an explanatory diagram showing a sheet conveying operation of a fixing / conveying roller pair.

FIG. 9 is an explanatory diagram showing a sheet transport operation of a pair of fixing transport rollers.

FIG. 10 is an explanatory diagram of a conventional fixing device.

FIG. 11 is an explanatory diagram of a conventional fixing device.

[Explanation of symbols]

 C ... Process cartridge G ... Lever guide L ... Lever P ... Sheet S ... Sheet detection sensor 1 ... Cassette 2 ... Feed roller 3 ... Separation claw 4 ... Sheet guide 5,6 ... Conveying guide 7a, 7b ... Timing roller pair 8 ... Photosensitive drum 9 ... Laser oscillator 10 ... Transfer roller 11 ... Fixing device 11a ... Fixing frame 11b ... Entrance guide 11c ... Fixing roller 11d ... Pressure roller 11e ... Heater 11f, 11g ... Fixing conveyance roller pair 11h ... Fixing separation claw 12a, 12b ... Ejection guide 13 ... Ejection roller pair 14 ... Ejection section

Claims (4)

[Claims] 1. An image carrier, image forming means for forming an image through a plurality of processes acting on the image carrier, and an image formed on the image carrier for recording on a recording material. Image recording means, fixing means for fixing the recorded image of the recording material after the image recording, fixing conveying means for sandwiching and conveying the recording material after the image fixing,
The image forming apparatus is characterized in that the fixing / conveying means is swingable so that the recording material can be conveyed in a different direction from the fixing means. 2. The image forming apparatus according to claim 1, wherein the fixing and conveying unit is a pair of conveying rollers, and the conveying roller on the driven side oscillates about a rotation axis of the conveying roller on the driving side. apparatus. 3. The image forming apparatus according to claim 2, wherein the driven-side transport roller is supported by a support member rotatable about a rotation axis of the drive-side transport roller. 4. The image forming apparatus according to claim 1, wherein the fixing / conveying unit swings by rotating a supporting member to change a winding amount of the recording material around the fixing unit.