JPH0676152B2 - Recording paper transport device for electrophotographic device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording sheet conveying device for an electrophotographic apparatus, and in particular, it is possible to use ordinary recording sheets for electrophotography and thick recording sheets such as postcards. The present invention relates to a recording sheet conveying device in an electrophotographic apparatus.

[Conventional technology]

Electrophotographic printers are widely used as devices for recording image information created by word processors and computers. A laser beam printer is generally used as the electrophotographic printer.

FIG. 3 shows an example of a laser beam printer, which is a housing 1
A photoconductive photosensitive drum 2 which is rotated at a constant speed is provided inside, and a charger 3, a laser beam exposure device 4, a developing device 5, and a transfer device are arranged in this order facing the outer peripheral surface of the photosensitive drum 2. 6, a cleaning device 7 is provided.

The outer peripheral surface of the photosensitive drum 2 is uniformly charged by the charger 3 and then exposed by the laser beam exposure device 4 according to the image information to be recorded to form an electrostatic latent image. The developing device 5 develops the electrostatic latent image into a toner image.

8a and 8b are paper cassettes, a part of which is exposed to the outside of the housing 1, and accommodate the recording papers 9a and 9b. The extraction rollers 10a, 10b extract one of the recording sheets 9a, 9b (here, the case of the recording sheet 9a will be described as an example) stored in the paper cassettes 8a, 8b to the registration rollers 11a, 11b. send. The registration rollers 11a and 11b receive and stop the leading edge of the fed recording paper 9a, adjust the feeding timing so that the leading edge aligns with the toner image formed on the photosensitive drum 2, and adjust the friction. Transport by force. Curved inversion guide 12a,
The reference numeral 12b is arranged on the downstream side of the registration rollers 11a, 11b, and forms a paper feed path for bending and reversing the recording paper 9a sent from the registration rollers 11a, 11b while curving it. Reversing rollers 13a and 13b are also provided in the curved sheet feeding path.

The recording paper 9a, which is conveyed so as to be aligned with the toner image formed on the outer peripheral surface of the photosensitive drum 2, is superposed on the photosensitive drum 2 at the transfer portion and is transferred by the transfer device 6 from the rear surface thereof. The toner image is transferred by the action of static electricity. The toner remaining on the outer peripheral surface of the photosensitive drum 2 without being transferred is cleaned by the cleaning device 7.

The fixing device including the heat roller 14a and the back-up roller 14b heats and fixes (fixes) the toner image by heating the recording paper 9a on which the toner image is transferred by the transfer device 6. The paper discharge rollers 15a and 15b discharge the recording paper 9a on which the toner image is fixed onto a paper discharge tray 16 attached to the side surface of the housing 1.

In such an electrophotographic laser beam printer, when image information is recorded on various papers such as JIS A3 size, B4 size, A4 size and postcards, as shown in FIG. Are conveyed to the registration rollers 11a while being centered on the basis of the center position of the registration rollers 11a in the axial direction.

However, in the conventional recording paper transporting device, when a thick paper such as a postcard is used in addition to the general electrophotographic paper, the transport speed changes depending on the paper thickness, and the transfer deviation occurs, When the trailing edge of the curved recording paper leaves the registration rollers 11a, 11b and becomes free, it bounces and violently collides with the inversion guide 12a on the outside of the curve,
There is a problem that this vibration is transmitted to the transfer position to cause transfer disorder.

FIGS. 5 and 6 show changes in the recording paper conveyance speed with respect to changes in the paper thickness. As shown in FIG. 5, recording paper
When 9a is curved and conveyed so as to wind around the registration roller 11a having the peripheral speed Vr, the relationship between the paper thickness t and the recording paper conveyance speed Vp changes as shown in FIG. become. This is because the driving radius R by the registration roller 11a on the inner side of the curve changes depending on the paper thickness t.

7 to 9 show the positional relationship between the registration rollers 11a and 11b and the reversal guide 12a and the relationship between the transfer disturbance of the toner image on the recording sheet 9a. As shown in FIG. 7, the curved outer reversing guide 12a is arranged with a step δ so that its tip is located lower than the tangent line of the registration rollers 11a and 11b. This is to prevent the leading edge of the recording sheet 9a from hitting the leading edge of the reversing guide 12a and causing a paper jam. However, with such a step δ, when a thick recording paper 9a such as a postcard is used, as shown in FIG.
The trailing edge of the recording paper 9a that is curvedly conveyed along 12a, 12b is between the registration rollers 11a, 11b and the reversing rollers 13a, 13b.
When they are separated from each other, they try to recover straightly, and they spring with their elasticity and collide strongly with the reversing guide 12a and vibrate. This vibration propagates through the recording paper 9a and vibrates the portion at the transfer position to generate transfer disorder. FIG. 9 shows a recording sheet 9a on which a grid pattern is recorded, where A is the recording sheet.
Transfer disturbance due to vibration when the trailing end of 9a leaves the registration rollers 11a and 11b, and B indicates transfer disturbance due to vibration when the trailing end of the recording paper 9a leaves between the reversing rollers 13a and 13b.

As a conventional technique relating to the electrophotographic apparatus as described above, for example, the technique described in Japanese Patent Publication No. 59-5489 is known.

[Problems to be Solved by the Invention]

As described above, while the recording sheet for transferring the toner image formed on the primary recording medium is curved, it is sandwiched between the two rollers to convey the recording sheet by its frictional force, and the curving reversal guide portion is curved. In the recording paper conveying device of the electrophotographic apparatus which supplies the toner image to the toner image transfer portion through the recording paper, when recording papers having different paper thicknesses are used, there is a drawback that transfer deviation or transfer disorder occurs.

Accordingly, the present invention provides an electrophotographic apparatus of this type, which provides a recording sheet conveying apparatus having a simple structure in which transfer deviation or transfer disturbance does not occur even when recording sheets having different paper thicknesses are used.

[Means for Solving the Problems]

According to the present invention, a recording sheet for transferring a toner image formed on a primary recording medium is curved and held between two rollers to convey the recording sheet by the frictional force, and after the two rollers, In a recording sheet conveying device of an electrophotographic apparatus, which bends a recording sheet fed from two rollers by a curved inversion guide and bends the recording sheet to supply it to a toner image transfer section, a roller inside the curved sheet is , An elastic drive roller, the cardboard sheet passing zone of which is a small diameter portion, and an inclined portion is provided between the small diameter portion and another portion.
It is a rigid driven roller, and is characterized by being formed with an annular groove into which the tip of the reversing guide is inserted.

[Action]

According to the present invention, when a thin ordinary recording sheet for an electrophotographic apparatus is used, the recording sheet is conveyed by the large diameter portion on the inner side of the curve, and when a thick postcard is used, the postcard is Since the small-diameter portion is used for conveyance, the drive radii for these two types of recording paper become equal, so that even if the paper thickness changes, the conveyance speed does not change, and transfer deviations due to speed changes occur. Can be prevented.

Further, according to the present invention, since the reversing guide located on the outer side of the curve and the roller with the tip of the reversing guide facing each other form a continuous conveyance path (guide surface) without a step, the trailing end of the recording sheet is two. Even if the rollers are separated from each other, they cannot be repelled, so that the vibration due to the strong collision with the paper does not occur and the occurrence of the transfer disturbance can be prevented.

〔Example〕

Hereinafter, a first embodiment in which the present invention is applied to a registration roller will be described.
This will be described with reference to the drawings and FIG.

The drive-side registration roller 11c located inside the curved recording paper is an elastic roller having an elastic material layer 11e on the surface of a cored bar 11d, and a drive gear 17 is fixed to the cored bar 11d.
Further, a small-diameter portion 11e 'is formed at a central position in the axial direction of the registration roller 11c (a band through which the postcard is passed) over a range slightly (Δl) wider than the width of the postcard. The small diameter portion 11
The outer diameter φDp of e ′ and the large diameter portion 11e ″ on both outer sides of the small diameter portion 11e ′
The outer diameter φDh is related to the drive radius of a thick postcard that is wrapped around the small diameter portion 11e ′ and the thin normal electrophotographic recording paper that is fed around the large diameter portion 11e ″. Set so that the drive radii are the same. Thin ordinary electrophotographic recording paper is sandwiched between both the small diameter portion 11e 'and the large diameter portion 11e ", so there is no streak due to the stepped portion. As described above, the small diameter portion 11e ′ and the large diameter portion 11e ″ may be connected by an inclined portion.

The registration roller 11f on the driven side located outside the curved recording sheet is a rigid metal roller, and the registration roller 1
Two annular grooves 11f ', 11f "are formed in a portion of the 1c opposed to the small diameter portion 11e' to allow the two claws 12a 'protruding from the tip of the inversion guide 12a on the outside of the curve to enter therein. The position where the claw 12a ′ enters the annular groove 11f ′ (11f ″) is
It is selected immediately after the nip of the two registration rollers 11c and 11f that holds the recording sheet 9a.

According to the recording paper transporting device configured as described above, even if the recording paper (normal electrophotographic recording paper and postcard) is curved and driven by the registration rollers 11c and 11f, The transport speed does not change.

Further, since the claw portion 12a ′ of the reversing guide 12a enters the annular grooves 11f ′, 11f ″ of the registration roller 11f at the position immediately after nipping to form a guide surface continuous with the registration roller 11f,
There is no possibility that the leading edge of the recording sheet 9a hits the leading edge of the reversing guide 12a to cause a paper jam. Further, even if the trailing edge of the recording paper 9a leaves the space between the two registration rollers 11c and 11f, it comes into immediate contact with the reversing guide 12a, so that the recording paper 9a does not vibrate strongly and vibrate.

In the above embodiment, the driving side registration roller 11c is arranged inside the curved recording paper 9a, and the driven side registration roller 11f is arranged outside. However, the present invention arranges these two registration rollers. It can be performed even if the positions are reversed. In this case, the small diameter portion is formed on the driven side registration roller, and the annular groove is formed on the driving side registration roller.

Further, the present invention can be similarly applied to the reversing roller.

〔The invention's effect〕

According to the present invention, when a thin ordinary recording sheet for an electrophotographic apparatus is used, the recording sheet is conveyed by a large diameter portion on the inner side of the curve, and when a thick postcard is used, the recording sheet has a small diameter. Since these two types of recording paper are conveyed, the driving radii become equal even if they are conveyed while curving these two types of recording paper. Therefore, even if the paper thickness changes, the conveyance speed does not change and the speed changes. It is possible to prevent the occurrence of transfer deviation due to.

Further, according to the present invention, since the reversing guide located on the outer side of the curve and the roller with the tip of the reversing guide facing each other form a continuous transport path (guide surface) without a step, the curving recording paper has two trailing ends. Even if you leave the rollers, you can't flip,
Therefore, it is possible to prevent the occurrence of transfer disturbance without generating vibration due to a strong collision with the paper.

The present invention can be easily implemented because it is necessary to slightly change the shape and the positional relationship of a part of the conventionally used roller and reversing guide.

[Brief description of drawings]

1 and 2 show an embodiment of the present invention.
FIG. 2 is a partially vertical front view of the registration roller, and FIG. 2 is a vertical side view showing the relationship between the registration roller and the reversing guide.
3 to 9 show a conventional laser beam printer. FIG. 3 is a vertical sectional side view of the whole, FIG. 4 is a positional relationship diagram between a registration roller and a recording sheet, and FIG. FIG. 6 is a vertical sectional side view showing the relationship of the guides, FIG. 6 is a recording sheet conveyance speed characteristic diagram, FIG. 7 is a vertical sectional side view showing the positional relationship between the registration rollers and the recording sheet, and FIG. 8 is a longitudinal section of the curved recording sheet conveyance path. A side view and FIG. 9 are plan views of a recording sheet on which a grid pattern is recorded. 9a, 9b …… Recording paper, 11c …… Drive side registration roller,
11e ... Elastic material layer, 11e '... Small diameter part, 11e ″ …… Large diameter part, 11f …… Registration roller on driven side, 11f ′, 11f ″ ……
Annular groove, 12a …… Inversion guide, 12a ′ …… Claw.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-53-127727 (JP, A) Actually opened 63-130452 (JP, U) Actually opened 61-145749 (JP, U) Actually opened 61- 168042 (JP, U) Actual opening 63-162758 (JP, U) Actual opening 60-6732 (JP, U)

Claims (1)

[Claims] 1. A recording sheet for transferring a toner image formed on a primary recording medium is held between two rollers while being curved, and the recording sheet is conveyed by the frictional force of the two rollers. 2 by means of a curved reversing guide placed later
In a recording paper conveying device of an electrophotographic apparatus, which bends the recording paper sent out from two rollers while curving it and supplies it to the toner image transfer portion, the roller inside the curved recording paper is an elastic drive roller, and the thick paper The paper passing zone is formed to have a small diameter portion, and an inclined portion is provided between the small diameter portion and another portion. The roller on the curved outer side of the recording paper is a rigid driven roller, and A recording sheet conveying device for an electrophotographic apparatus, wherein an annular groove into which a tip is inserted is provided.