JPH08137371A - Image forming device - Google Patents

Abstract

PURPOSE: To provide an image forming device capable of preventing a deterioration in printing quality caused by the sticking of a waterdrop to a paper sheet after fixing and a carrying fault caused by toner stuck to a carrying path, in an image forming device provided with plural ventilation grooves in the carrying path on the rear stage of a fixing unit for ventilation. CONSTITUTION: The image forming device for developing an electrostatic latent image formed on an image forming body 50 with the toner, transferring the toner image to a recording medium 2, to heat/fix the toner image by a fixing part 57 and carrying the recording medium 2, to eject it by a pair of ejecting rollers 7 and 8 at least one of which is driven by rolling contact is constituted to provide the carrying path 4 carrying the recording medium 2, a ventilation path 10 joining the carrying path 4 on the rear stage of the fixing part 57, a blower means 11 blowing air into the ventilation path 10 and a guiding part 12 provided in the carrying path 4 on the rear stage of the fixing part 57, guiding the recording medium 2 and letting the air from the ventilation path 10 pass through.

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 an electrophotographic printing apparatus, and more particularly to an image forming apparatus which blows air by providing a plurality of ventilation grooves in a conveyance path downstream of a fixing device.

With the recent development of office automation, electrophotographic printing apparatuses such as laser printers are widely used in output terminals of computers, facsimile machines, copying machines and the like.

The image process of an electrophotographic printing apparatus includes an electrostatic latent image process of irradiating a charged photosensitive drum with light to form an electrostatic latent image, a developing process of developing the electrostatic latent image with a toner, and a developed toner. A transfer process of transferring an image to a recording sheet and a fixing process of fixing a toner image transferred to a recording sheet (hereinafter referred to as a sheet) are included.

As a fixing method, a pressure fixing method, a flash fixing method, a heat fixing method and the like are known, and a toner fixing mechanism is different depending on which fixing method is adopted. OA devices such as printers and copiers require power saving, downsizing, and a shorter warm-up time, but none of the fixing methods described above can meet all the requirements. However, the heat fixing method, which requires a warm-up time, is widely used because the size and weight of the apparatus can be reduced and the apparatus configuration is simple.

The present invention relates to a conveying path and a discharging mechanism for a sheet after fixing in an apparatus using such a heat fixing method. The paper that has passed through the fixing device is heated to evaporate the water contained therein to form dew on the conveying path and the discharge roller, and the water droplets adhere to the paper, causing wrinkles on the paper and degrading print quality. In particular, during double-sided printing, transfer defects easily occur due to wrinkles and wetting.

Therefore, there is a demand for a method capable of preventing these obstacles.

[0007]

2. Description of the Related Art FIG. 6 illustrates an internal side view of an electrophotographic printing apparatus having a double-sided printing function to which the present invention is applied. In the figure, 1 is a cassette accommodating and accommodating printing paper (hereinafter referred to as paper) 2a, 1a is a manual feed guide, 3 is a feeding roller, 4a to 4c are conveying paths, 5 is a printer section, 6 is a reversing section, 7a, Reference numeral 8a indicates a discharge roller, and 9 indicates a stacker.

The printer section 5 includes a charger 51, an optical unit 52, which is arranged around a photosensitive drum 50a which is an image forming body.
The developing device 53, the transfer roller 54, the static eliminator 55, the cleaner 56, and the fixing device 57a.

The fixing device 57a is composed of a heating roller and a pressure roller which rotate in pressure contact with each other, and the heating roller contains a heat source of, for example, a halogen lamp. With such a configuration, when the charging brush of the charging device 51 is rotated by applying a negative charge, the surface of the photosensitive drum 50a is negatively charged, and the laser light (or LED) obtained by optically modulating the print information from the optical unit 52 is used. And the like) are irradiated to the photosensitive drum 50a, and the electric charge is reduced only at the irradiated portion to form an electrostatic latent image. The electrostatic latent image on the photosensitive drum 50a is developed with toner by the developing device 53.

On the other hand, the sheet 2a delivered from the cassette 1 by the rotation of the delivery roller 3 or the sheet 2a inserted from the manual feed guide 1a is transported in the direction of the arrow in the transport path 4a. Then, the toner image on the photosensitive drum 50a is attracted and transferred to the paper 2a by the electric charge given to the back surface of the paper 2a by the transfer roller 54. Paper 2a with the toner image transferred
Is heated / pressurized and fixed by the fixing device 57a.

The conveyance path 4b at the rear stage of the fixing device 57a is formed into a flat guide or a rib-shaped guide having a rectangular cross section (hereinafter referred to as a rectangular rib), and the paper 2a is fixed by the fixing device 57a and sent out. Then, the sheet is discharged to the stacker 9 by the pair of discharge rollers 7a and 8a at the end of the transport path 4b.

It is difficult to transfer the entire toner image on the photosensitive drum 50a onto the sheet 2a, and the toner remains on the photosensitive drum 50a. The residual toner is cleaned by the cleaner 56 to prepare for the next printing operation.

If printing is also performed on the back side of the paper 2a, a double-sided printing instruction is given to an operation panel (not shown),
The control unit of the apparatus is switched to the double-sided printing mode, and stops when the trailing edge of the sheet 2a with one-sided printing passes through the gate G of the reversing unit 6, and then the gate G, as shown by the two-dot chain line in the figure.
, The sheet 2a is conveyed in the opposite direction on the conveying path 4b, bypasses the conveying path 4c and enters the conveying path 4a again, and the back surface of the sheet 2a becomes the printing surface and printing is performed in the same manner as above. Transport path
The sheet 4b is ejected to the stacker 9 by the ejection rollers 7a and 8a.

[0014]

According to the above-mentioned conventional method, the water vapor generated from the sheet 2a after the heat fixing is carried out by the conveying path 4b.
As shown in FIG. 7, the flat part of the surface of the paper, the tip of the rectangular rib, and the discharge rollers 7a and 8a are condensed, and accumulated by the repeated printing to form water droplets.
Distortion and print quality deterioration.
In particular, during double-sided printing, there is a problem that a transfer failure occurs due to the wetting of the paper 2a.

Further, the temperature of the conveying path 4b rises due to the heat from the fixing device 57a and the sheet 2a, and the toner on the sheet after fixing is fixed on the surface of the conveying path 4b, the tip of the rectangular rib, or the discharging roller 7a. , 8a adheres and hardens, which causes friction and catching in the paper feed, which causes jams, skews, and other conveyance obstacles, and wrinkles and corner breaks. There is a problem.

As a known example related to this, Japanese Patent Laid-Open No. 58-58
JP-A-106562 and JP-A-58-154867 have been proposed. However, JP-A-58-1
According to the method of Japanese Patent No. 06562, a fine rotation pattern is formed on the peripheral surface of a rotary drive that conveys the transfer paper, and fine particles are attached to the projections to reduce the contact area with the transfer paper and transfer the transfer paper. The purpose is to prevent the offset phenomenon on paper, and cannot be a method for solving the above problems.

In the method disclosed in Japanese Patent Laid-Open No. 58-154867, an axial fan for generating an air flow from below is provided in the vicinity of the paper outlet, and the purpose is to prevent condensation of water vapor and water wet of the paper. However, it does not mention that water vapor generated from the paper adheres to the paper transport path, and is blown by a fan from the bottom of the paper. Since water droplets are generated between the upper part of the sheet and the conveying path, it cannot be a method for solving the above problems.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus capable of preventing deterioration of print quality due to adhesion of water droplets on a sheet after fixing and trouble of conveyance due to toner adhering to a conveying path or the like.

[0019]

FIG. 1 shows the principle of the present invention (Claim 1). In the figure, 2 is a recording medium, 50 is an image forming body, 57 is a fixing device, 4 is a conveying path for conveying the recording medium 2, 10 is a ventilation path which joins the conveying path 4 at the latter stage of the fixing unit 57,
Reference numeral 11 denotes an air blowing unit that blows air to the ventilation passage 10, 12 denotes a guide portion that is provided on the conveyance passage 4 in the subsequent stage of the fixing unit 57 and that guides the conveyance of the recording medium 2 and that allows the ventilation air from the ventilation passage 10 to pass.
Reference numeral 8 is a pair of discharge rollers which are in rolling contact with each other and at least one of which is driven.

Accordingly, the electrostatic latent image formed on the image forming body 50 is toner-developed, the toner image is transferred to the recording medium 2 and heat-fixed by the fixing section 57, and the recording medium 2 is conveyed through the conveying path 4. It is configured to be discharged by the discharge rollers 7 and 8.

Next, the means of claims 2 to 5 will be described. According to a second aspect, in the first aspect, the guide portion 12 is
A plurality of ribs are formed on the wall surface of the transport path 4 in parallel with the transport direction of the recording medium 2 and having a rounded tip at the tip of a cross section perpendicular to the transport direction.

According to a third aspect of the present invention, in the first or the second aspect, the plurality of discharge rollers 7 and 8 have a plurality of gear-shaped cross sections on the outer periphery of the discharge roller 7 on the fixing surface side of the transfer toner of the recording medium 2. The first groove of was formed.

According to a fourth aspect of the present invention, in the third aspect of the present invention, the discharge roller 7 having at least the first groove among the discharge rollers 7 and 8 has at least one ring-shaped second groove at substantially equal intervals on the outer circumference. Formed.

According to a fifth aspect of the present invention, in the first, second, third, or fourth aspect, at least the discharge roller 7 of the pair of discharge rollers 7, 8 on the fixing surface side of the transfer toner of the recording medium 2 is fixed. Roundness was formed at the corners at both ends of the sheet, or at the corners at both ends of the discharge roller 7 having the second groove and the corners of the second groove.

[0025]

In FIG. 1, the blown air from the blower means 11 is a ventilation passage.
It is sent to the conveyance path 4 which merges in the latter stage of the fixing section 57 via 10
The air blows through the guide portion 12 provided in the transport path 4 to cool the transport path 4 and also cool the heat of the recording medium 2 that has been heat-fixed and sent out by the fixing portion 57 to cool the transport path 4. The temperature rise and the amount of water vapor generated from the recording medium 2 are suppressed, and the generated water vapor is discharged to the outside by blowing air, so that it is possible to prevent dew condensation on the wall surface of the conveyance path 4 due to the water vapor, and also the conveyance path 4 By suppressing the temperature rise of 1, the toner fixed on the recording medium 2 is prevented from adhering to the guide portion 12.

Therefore, it is possible to prevent water droplets from adhering to the recording medium 2 and prevent distortion due to wetting of the recording medium 2 and to prevent wrinkles, especially double-sided printing. It is possible to prevent the print quality from deteriorating due to poor transfer due to the wetting of the recording medium 2 at that time. In addition, it is possible to prevent a jam or the like that is caused by a friction or a catch of the recording medium 2 with respect to the toner attached to the conveying path 4.

Next, the operation of claims 2 to 5 will be described. In the second aspect, since the plurality of rib-shaped tips of the guide portion 12 are rounded, the contact portion with the recording medium 2 is small, the water droplets and the toner are less attached to the transport path 4, and the transport path 4 is attached. The adhered water droplets can be reduced from adhering to the recording medium 2, and the toner adhering to the transport path 4 moves to a position where it does not come into contact with the recording medium 2 due to the roundness of the tip of the guide portion 12, so that it accumulates and solidifies. This can be prevented, and the effect of preventing the conveyance failure of the recording medium 2 can be improved.

According to a third aspect of the present invention, a plurality of gear-like grooves are provided on the outer circumference of the discharge roller 7 and the tip of the gear-shaped tooth shape is rounded, so that the contact portion with the recording medium 2 is small and the discharge roller 7 is small. It is possible to reduce the adherence of water droplets between the recording medium 8 and the recording medium 2 to the recording medium 2, and to reduce the adhesion of the toner fixed on the recording medium 2 to the discharge roller 7 and to the discharge roller 7. Since the toner moves to a position where it does not come into contact with the recording medium 2 due to the roundness of the tip of the tooth profile, it is prevented from accumulating and solidifying, and the effect of preventing the conveyance obstacle of the recording medium 2 can be further improved.

According to the present invention, the ring-shaped second groove is formed on the outer circumference of the discharge roller 7 having at least the first groove in the pair of discharge rollers 7 and 8. The air blown to the guide portion 12 via 10 passes through the second groove and smoothly flows to the outside. Therefore, the water vapor generated from the recording medium 2 after fixing is sent out to the outside, and the effect of cooling the transport path 4 and the recording medium 2 is also improved.

According to a fifth aspect of the present invention, at least the discharge rollers 7 and 8 on the fixing surface side of the transfer toner of the recording medium 2 are fixed.
Discharge roller 7 with corners at both ends or second grooves formed
By forming roundness at the corners on both ends of the second groove and the corners of the second groove, at least the toner attached to the discharge roller 7 is
Since the corners move to a position where they do not contact the recording medium 2, the recording medium 2 is prevented from accumulating and solidifying.
It is possible to further improve the effect of preventing transport failure.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to the electrophotographic printing apparatus described in the conventional example will be described below with reference to FIGS. The same reference numerals denote the same objects throughout the drawings.

FIG. 2 is an internal side view showing an embodiment of the present invention,
3 and 4 are explanatory views of the embodiment. Paper 2a of Figure 2,
Fan 11a, guide 12a, photosensitive drum 50a, and fixing device 57
Reference character a corresponds to the recording medium 2, the blowing unit 11, the guide unit 12, the image forming body 50, and the fixing unit 57 in FIG. 1, respectively.

As shown in FIG. 2, the conveyance path of the printer section 5a
Between the 4B and the housing cover C, the ventilation path 10a is provided along the conveyance path 4c.
Is provided, and a ventilation port is provided in the housing cover C at the start end of the ventilation path 10a.
100 is opened, and the fan 11a is arranged inside thereof.

At the end of the ventilation passage 10a, the conveyance passage 4c and the conveyance passage 4B are provided.
It is formed so as to join the conveyance path 4B in the vicinity of the branch point. As shown in FIG. 3, a plurality of rib-shaped guides 12a are formed in parallel with the conveyance direction on the upper side of the conveyance path 4B, and each guide 12a has a rounded shape R1 at the tip cross section.

Further, discharge rollers 7A and 8A, one of which is driven and the other of which is in rolling contact, are provided at the end of the conveying path 4B, and as shown in FIGS. 4 (a) and 4 (b), the discharge roller 7A has an outer periphery. A plurality of grooves 70 are formed so that the cross section has a gear shape. A rounded R2 is formed at the tip of the gear-shaped tooth profile (a convex portion between the adjacent groove 70), and further rounded R3 is formed at the corners of both ends of the discharge rollers 7A and 8A.

With such a configuration, when the apparatus is powered on, the heat source of the fixing device 57a is energized and the fan 11a is driven to blow air to the ventilation passage 10a, and the ventilation is carried out in the conveyance passage 4B. It flows through the guide 12a toward the discharge rollers 7A, 8A.

When the fixing device 57a reaches a predetermined printable temperature, printing is started, and the paper 2a on which the toner image is transferred is thermally fixed by the fixing device 57a and sent out, and the guide 12 of the conveying path 4B.
sent to a. After fixing, the water vapor generated from the paper 2a
The air is sent from the fan 11a passing through the guide 12a toward the discharge rollers 7A, 8A and discharged to the outside of the apparatus.

At this time, the conveyance path 4B and the sheet 2a are blown by the air.
Since the heat of the paper is cooled, the generation of water vapor from the paper 2a which is heated by the fixing unit 57a and comes out is suppressed, and the adhesion of water droplets is reduced. Moreover, the water droplets attached to the guide 12a
Due to the roundness R1 at the tip of the sheet 12a, the contact area between the guide 12a and the sheet 2a is small, so that the adhesion to the sheet 2a is reduced.

Further, as shown in FIG. 4 (a), the water droplets attached to the discharge rollers 7A and 8A are accumulated on the bottom of the tooth profile of the discharge roller 7A, so that the water droplets are not attached between the discharge rollers 7A and 8A. Therefore, since water drops do not adhere to the paper 2a, it is possible to prevent the paper 2a from getting wet with water drops and being distorted so that wrinkles do not occur and it is possible to prevent jams and other transport obstacles. Further, during double-sided printing, the problem that transfer failure occurs on backside printing on the paper 2a wetted by frontside printing is eliminated.

Further, the roundness of the tip of the guide 12a of the conveying path 4A
R1, rounding of the tip of tooth shape of discharge roller 7A R2 and discharge roller
Due to the roundness R3 at both ends of 7A and 8A, the toner fixed on the paper 2a is less likely to adhere to the guide 12a and the discharge rollers 7A and 8A. Especially, when the printing surface of the paper 2a is on the guide 12a side during double-sided printing due to the roundness R1 of the tip of the guide 12a,
The toner fixed on 2a is prevented from adhering to the guide 12a.

Even if the toner adheres to the roundnesses R1 to R3, the toners sequentially adhering to the roundnesses R1 to R3 due to the low temperature.
Since it shifts to a position where it does not contact the paper 2a of R3, it does not accumulate and harden.

Therefore, the toner on the fixed sheet 2a is less likely to adhere to the guide 12a and the discharge rollers 7A, 8A of the conveying path 4B due to heat, and the toner 9 does not solidify, so that the sheet 2a is conveyed. Occasionally, friction can be generated, and it is possible to prevent jamming, skewing, and other transport obstacles, and wrinkles and corner breaks.

FIG. 5 shows a different embodiment. FIG. 5 shows that a ring-shaped groove is formed on the outer circumference of the discharge roller 7A described in the above embodiment to improve the flow of air as the discharge roller 7A ₁ . That is, as shown in FIG. 5, a plurality of ring-shaped grooves 71 are formed on the outer circumference. Further, the corners on the outer circumference of each groove 71 are formed with a roundness R4 similar to the roundness R3 at both ends.

With such a structure, the air blown from the fan 11a to the ventilation passage 10a passes through the guide 12a of the conveyance passage 4B toward the discharge rollers 7A ₁ and 8A, and passes through the groove 71 of the discharge roller 7A _1. It is sent out through the device.

Therefore, the air blown from the ventilation passage 11a to the guide 12a can pass through the groove 71 of the discharge roller 7A ₁ with less resistance, and the conveying passage 4B and the paper 2a can be cooled more effectively.

Further, the toner adhered to the discharge rollers 7A _{1 and} 8A moves to the position where it does not touch the paper 2a due to the roundness R3 and R4, so that it does not accumulate or solidify, and therefore the paper 2a
Since there is no friction or catching when discharging,
It is possible to further prevent the transport failure.

In the different embodiment described above, the case where the discharge roller 7A of the embodiment described in FIG. 4 is provided with the ring-shaped groove 71 to form the discharge roller 7A ₁ has been described, but the same applies to the discharge roller 8A. Of course, the groove may be formed.

[0048]

As described above, according to the present invention,
According to the first aspect, the temperature rise in the transport path and the amount of steam generated from the recording medium are suppressed, and the generated steam is discharged to the outside by blowing air, so that it is possible to prevent dew condensation due to steam on the wall surface of the transport path. Further, the toner fixed on the recording medium is prevented from adhering to the guide by suppressing the temperature rise of the conveying path.

Therefore, it is possible to prevent water droplets from adhering to the recording medium, to prevent distortion caused by wetting of the recording medium, and to prevent wrinkles from occurring. It is possible to prevent the print quality from deteriorating due to poor transfer due to wetting. In addition, it is possible to prevent a conveyance trouble such as a jam caused by friction or catch of the recording medium on the toner attached to the conveyance path.

According to the second aspect of the present invention, it is possible to reduce the adhesion of water droplets and toner to the conveying path and the adhesion of water droplets on the conveying path to the recording medium. Further, the toner adhered to the conveying path is guided. Since the toner is moved to a position where it does not come into contact with the recording medium due to the rounded tip of the portion, it is possible to prevent the toner from accumulating and solidifying, and it is possible to improve the effect of preventing the conveyance obstacle of the recording medium.

In the third aspect, it is possible to reduce the water droplets between the pair of discharge rollers from adhering to the recording medium, and reduce the toner fixed on the recording medium to the discharge rollers. The toner adhering to the discharge roller is prevented from moving to a position where it does not come into contact with the recording medium due to the roundness of the tip of the tooth profile and solidifying, so that the effect of preventing the recording medium conveyance failure can be further improved.

According to the present invention, the air blown from the air blower through the ventilation passage to the guide portion passes through the second groove and smoothly flows to the outside, and the cooling of the conveying passage and the recording medium is promoted.
According to the fifth aspect, the toner attached to the discharge roller is prevented from moving to a position where it does not come into contact with the recording medium due to the roundness of the corners and solidifying, and the effect of preventing the conveyance failure of the recording medium can be further improved. . There is an effect.

[Brief description of drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is an internal side view showing an embodiment of the present invention.

FIG. 3 is an explanatory diagram of the embodiment (No. 1)

FIG. 4 is an explanatory diagram of the embodiment (No. 2)

FIG. 5 is a configuration diagram showing a different embodiment of the present invention.

FIG. 6 is an internal side view of an electrophotographic printing apparatus to which the present invention is applied.

FIG. 7 is an explanatory diagram of a conventional example.

[Explanation of symbols]

2 is a recording medium, 2a is paper, 4,4a
4c and 4B are conveying paths, 7,8,7a, 8a, 7A, 8A and 7A ₁ are discharge rollers, 10 and 10a are ventilation paths, 11 is ventilation means,
11a is a fan, 12 is a guide section, 12a is a guide, 50 is an image forming body, 50a is a photosensitive drum, 57 is a fixing section, 57a is a fixing device, 7a
0,71 is groove, R1-R4 are rounded

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tsutomu Honma 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor, Mitsuru Akku, 1015, Kamedotachu, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited

Claims (5)

[Claims] 1. An electrostatic latent image formed on an image forming body is toner-developed, a toner image is transferred to a recording medium and heat-fixed by a fixing unit, the recording medium is conveyed, and at least one of them is rotatively contacted. An image forming apparatus for ejecting by a pair of driven ejecting rollers, a conveying path for conveying a recording medium, an air passage that joins with the conveying path at a stage subsequent to the fixing unit, and an air blowing unit for blowing air to the air passage. An image forming apparatus, comprising: a guide unit that is provided in a conveying path in a latter stage of the fixing unit and that guides the conveyance of the recording medium and that allows the air blown from the ventilation passage to pass therethrough. 2. The guide part is formed on a wall surface of the transport path in a plurality of rib shapes that are parallel to the transport direction of the recording medium and have a rounded shape at a tip of a cross section perpendicular to the transport direction. The image forming apparatus according to claim 1, wherein: 3. A plurality of first grooves having a gear-shaped cross section are formed on the outer periphery of the discharge roller on the fixing surface side of the transfer toner of the recording medium in the pair of discharge rollers, and the tip of the gear-shaped tooth profile is formed. A rounded shape, claim 1 or claim 2 characterized in that
Image forming device. 4. The discharge roller having at least the first groove of the pair of discharge rollers has at least one ring-shaped second groove formed on the outer periphery at substantially equal intervals. The image forming apparatus according to item 3. 5. A corner of both ends of the discharge roller at least on the fixing surface side of the transfer toner of the recording medium of the pair of discharge rollers, or a corner of both ends of the discharge roller in which the second groove is formed, and The image forming apparatus according to claim 1, claim 2, claim 3, or claim 4, wherein the corners of the groove 2 are rounded.