JPH0638028Y2 - Transfer material transport device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an image forming apparatus such as a copying machine and a printer, and more particularly, to a transfer material conveying device that conveys and supplies a transfer material to a facing portion between a photoconductor and a transfer charger. Regarding

2. Description of the Related Art In general image forming apparatuses such as copiers and printers that use the principle of xerography, the uniformly charged surface of a photosensitive drum is exposed with light corresponding to an original or image data to be printed. To form an electrostatic latent image, this electrostatic latent image is caused by a phenomenon of charged toner, and then transferred to a transfer material such as paper (hereinafter simply referred to as paper), and then peeled and fixed to obtain a desired image. There is.

The vicinity of the transfer portion of such an image forming apparatus is configured as shown in FIG. 8, for example, and a pair of sheet conveying rollers 10 and 10 that feed sheets one by one from a sheet tray or the like and abut against each other. The sheet is conveyed to the opposing portion of the photoconductor drum 16 and the transfer corotron 18 by a sheet conveying device 14 including a sheet guide plate 12 that guides the sheet.

The leading end of the paper guide plate 12 is the grounding member 20 of the transfer corotron 18.
It is fixed to the paper carrying-in side of the paper so as to be insulated or fixed. 22 is a static eliminator for peeling the paper.

The paper is transported by the paper transport device 14 using a photosensitive drum.
The paper is fed so as to overlap with the toner image on the photoconductor drum 16 in synchronization with the rotation of 16, and the corona discharge of the polarity opposite to that of the toner is performed from the back surface of the paper by the transfer corotron 18, so that the paper is At the same time as the toner comes into close contact with the photoconductor drum 16, the toner is electrostatically attracted to the paper and the transfer is performed. After the transfer, the sheet is discharged from the photoconductor drum 16 by being discharged between the pointed electrodes of the stripping static eliminator 22 and the sheet in accordance with the amount of electric charge of the sheet to be discharged.

Problems to be Solved by the Invention However, the tip portion of the sheet guide plate of the conventional sheet conveying device (the portion in the vicinity of the facing portion between the photosensitive drum and the transfer corotron)
Is a sheet metal or the like that is uniform in the direction perpendicular to the paper feed direction or has slits (cut grooves) formed. However, there is a problem in that toner easily scatters due to toner scattering from the upper layer of the toner image on the photoconductor drum or toner falling from the trailing edge of the paper, and the toner adhering to the paper guide plate adheres to the back surface of the paper. there were. The dirt on the back surface of the paper is particularly remarkable at the trailing edge of the paper.

In addition, since the contact area between the paper guide plate and the paper being conveyed is large, the paper guide plate is charged due to friction with the paper, and some toner is transferred to the paper before the paper comes into close contact with the photoconductor drum. There is also a problem that the image may be disturbed by being adsorbed or the like.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an image forming apparatus in which the occurrence of image distortion, the back surface of a sheet, and the like are less likely to occur.

Means for Solving the Problems In order to solve the above-mentioned problems, a plurality of substantially triangular pyramid-shaped members are provided at the tip of the transfer material guide plate that guides the transfer material between the photoconductor and the transfer charger in the transfer material transport direction. Provide a protrusion. These projections are formed so as to guide the transfer material at their ridges, and the radius of curvature at the top in the protruding direction is 0.2 m.
m or less, the opening angle of the two faces forming the ridge is 45 °
It is as below.

Effect According to the present invention, a plurality of substantially triangular pyramidal protrusions are provided at the tip of the transfer material guide plate, and the transfer material is guided to each ridge line portion of the triangular pyramid having a radius of curvature of 0.2 mm or less. , In the vicinity of the facing portion between the photosensitive drum and the transfer corotron,
The contact area between the paper and the guide member is small,
The guide member is less charged due to friction with the paper, and image disturbance due to the charge of the guide member can be prevented.

The protrusion of the guide member that comes into contact with the paper is formed such that the opening angle between the two surfaces forming the ridge line portion is 45 ° or less, so that the toner dropped from the developing device is unlikely to adhere to the protrusion. As a result, toner adhesion to the back surface of the paper is reduced.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of the vicinity of a transfer portion of an image forming apparatus using a sheet conveying device to which the present invention is applied. Reference numeral 30 denotes a photosensitive drum that rotates in the direction of arrow A. The surface of the photosensitive drum 30 is uniformly charged by a charging corotron (not shown), and then an original document or an image to be printed by an exposing unit (not shown). An electrostatic latent image is formed by exposure with light corresponding to the data. This electrostatic latent image is developed by the developing device 32 with toner.

On the other hand, the paper is sent out one by one from a paper tray or the like, and a pair of paper carrying rollers 34, 34 abutting against each other, a paper guiding plate 36 for guiding the paper, and the like are carried by the paper carrying device 38, and the photosensitive drum 30 and The sheet is sent to a portion facing the transfer corotron 40, and the sheet is brought into close contact with the photoconductor drum 30 by corona discharge by the transfer corotron 40, and at the same time, the toner is electrostatically adsorbed to the sheet and the transfer is performed. After the transfer, static electricity is removed by the peeling means 44 having the pointed electrode 42 to weaken the adsorption force of the paper to the photoconductor drum 30, and the paper is peeled from the photoconductor drum 30 due to the rigidity of the paper and discharged to the outside of the apparatus after fixing. It has become so.

A guide member 46 as shown in FIG. 2 (plan view) and FIG. 3 (side sectional view) is adhesively fixed to the leading end of the paper guide plate 36 of the paper transport device 38. The guide member 46 includes a fitting portion 48 for fitting the paper guide plate 36, and a plurality of substantially triangular pyramid-shaped projections 50. The protrusion 50 is formed as shown in FIG. 4, and the radius of curvature of the ridge line portion 52 (the portion that guides the paper) of the triangular pyramid (the radius of curvature of the apex in a cross section perpendicular to the protrusion direction of the protrusion 50). ) R ₁ is 0.2 mm, the opening angle θ ₁ from the top (ridge line) to the bottom in the same cross section
Is integrally formed with the main body so that the angle becomes 45 °. The guide member 46 is made of resin having insulation and flame retardancy (modified
PPO). As can be seen from FIG. 2, the protrusions 50 are formed obliquely with respect to the paper running direction (arrow B direction) so as not to deteriorate the discharge efficiency of the transfer corotron 40.

Returning to FIG. 1, the guide member 46 is provided such that its tip portion slightly enters the corona discharge region of the transfer corotron 40. Reference numeral 54 is a positioning member integrally attached to both sides of the paper guide plate 36, and the tip end portion thereof contacts the photoconductor drum 30 so that the positional relationship between the guide member 46 and the photoconductor drum 30 is constant. It is designed to be kept.

The fixing member 56 of the pointed electrode 42 of the peeling means 44 is formed as shown in FIGS. 5 to 7, and a plurality of peeling guards 58 are integrally formed on the upper portion thereof. The peeling guard 58 is the seventh
As shown in the figure, the upper ridge line portion 60 has a radius of curvature r ₂ of 0.2 mm and an opening angle θ ₂ downward from the ridge line portion of 45 ° similarly to the protrusion 50 of the guide member 46 described above. There is. The fixing member 56 and the peeling guard 58 are integrally resin-molded.

The peeling guard 58 is formed obliquely with respect to the paper running direction (the direction of arrow C), and one of the peeling guards (the rightmost one in FIGS. 5 and 6) is formed line-symmetrically with respect to the other peeling guards. Has been done. This is so that the paper after the peeling can run smoothly.

According to this embodiment, a resin-molded guide member 46 is attached to the leading end of the paper guide plate 36, and a plurality of substantially triangular pyramidal protrusions 50 are formed at the leading end of the guide member 46. Since the contact portion of is sharply formed with a radius of curvature of 0.2 mm, the contact area with the paper is small and frictional electrification by the paper is small, and the projection 50 has an opening angle of 45 ° from the top to the bottom. Therefore, the toner falling from the developing device or the like is less likely to adhere. As a result, the back surface of the paper is less likely to be contaminated by the falling toner and the image is less likely to be disturbed.

Table 1 shows the occurrence of stains on the back surface of the transfer material due to toner adhesion to the guide member 46, and Table 2 shows the occurrence of image disturbance due to frictional charging of the guide member 46. In these tables,
The ○ mark indicates that up to 15,000 transfer materials have not been soiled or disturbed, the △ mark indicates that up to 10,000 transfer materials have not been soiled or disturbed, and the X mark indicates up to 70,000 transferred materials or Indicates that no disturbance has occurred.

From these tables, it is clear that the state of occurrence of smearing on the back surface of the transfer material is relatively largely dependent on the opening angle, while the state of occurrence of image disturbance is relatively largely dependent on the radius of curvature of the ridge portion. In addition, in order to achieve both prevention of dirt on the back surface of the transfer material and image disturbance, the opening angle of the two surfaces forming the ridge is 45 degrees or less, and the radius of curvature of the top of the ridge is 0.2 m.
It must be less than m.

A plurality of peeling guards 58 are integrally formed on the fixing member 56 of the pointed electrode 42 of the peeling means 44.
Has a radius of curvature of 0.2 mm in the contact area with the paper,
Since the contact area with the paper is small, similar to the guide member 46 described above, frictional charging by the paper is small, and when the charge of the separation guard 58 and the toner image carried on the photosensitive drum 30 have the same polarity, The attraction force of the toner to the paper is weakened, and the toner transferred onto the paper is again transferred to the photosensitive drum 30.
There is little occurrence of transfer failure (retransfer) that is adsorbed on the top, and there is less chance of disturbing the image.

Further, a guide member 46 is provided so as to slightly project in the discharge area of the transfer corotron 40, and a peeling guard 58 is provided.
Is bridged above the peeling means 44, the portion not guiding the paper (the portion between the guide member 46 and the peeling guard 58) is short, and an image is formed particularly on a small-sized paper (postcard, business card, etc.). Even in such a case, the running of the paper is stable, which also makes it possible to obtain a good image.

The opening angles θ ₁ and θ ₂ of the protrusion 50 of the guide member 46 and the peeling guard 58 of the pointed electrode fixing member 56 are resin-molded integrally with the guide member 46 and the fixing member 56. Although it is set to 45 ° in this embodiment, it is more preferably set to about 30 °.

Effect of the Invention As described in detail above, the present invention provides a guide member having a plurality of substantially triangular pyramid-shaped projections at the tip of the transfer material guide member that guides the transfer material to the facing portion of the photosensitive drum and the transfer charger. This protrusion has a radius of curvature of 0.2 mm or less at the contact part with the paper and an opening angle of 45 ° or less downward from the contact part, so the contact area with the paper is small, friction charging is reduced, and development The toner falling from the container or the like is less likely to be attached, and the effect of reducing disturbances such as image distortion and soiling the back surface of the paper can be reduced.

[Brief description of drawings]

FIG. 1 is a configuration explanatory view showing an embodiment of the present invention, FIGS. 2 to 4 are views showing a shape of a guide member used in the embodiment of the present invention, and FIG. 2 is a plan view, FIG. 3 is a side sectional view, and FIG. 4 is a view showing the shape of the tip portion (projection). 5 to 7 are views showing the shape of the pointed electrode fixing member used in one embodiment of the present invention. FIG. 5 is a plan view, FIG. 6 is a front view, and FIG. 7 is a peeling guard. It is a figure which shows a shape. FIG. 8 is an explanatory diagram of a conventional technique. 30 ... photoconductor drum, 36 ... sheet guide plate, 40 ... transfer corotron, 44 ... peeling means, 46 ... guide member, 50 ... projection, 52 ... ridge, r ₁ ... ridge curvature, theta _{1 ...} opening angle.

Claims (1)

[Scope of utility model registration request] 1. A plurality of substantially triangular pyramid-shaped projections are provided at the tip of the transfer material guide plate for guiding the transfer material between the photoconductor and the transfer charger in the transfer material transport direction. Is formed so as to guide the transfer material along the ridge line portion, the radius of curvature of the apex portion in the protrusion protruding direction of the ridge line portion is 0.2 mm or less, and the opening angle of the two surfaces forming the ridge line portion is 45 ° or less. The transfer material conveying device characterized in that