JP2614327B2 - Image forming device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus, and in particular, holds a toner image on an image carrier on a transfer material carrier. The present invention relates to an image forming apparatus that electrostatically transfers the image onto a transfer material.

2. Description of the Related Art In a color electrophotographic copying machine, a transfer material carrying member, usually a supporting sheet such as a high-resistance film, is wound around a drum-shaped frame to form a transfer drum, and the transfer material is supplied and carried here. The end of the transfer material is mechanically fixed and held by a gripper provided on a part of the peripheral surface of the transfer drum. Then, in the process of rotating the transfer drum a plurality of times, a plurality of color toner images are electrostatically transferred from the image carrier to the surface of the transfer material by multiple transfer. For this purpose, a corona charging device is provided on the back surface of the carrier sheet, or a conductive roller is provided in contact with the transfer material held on the carrier sheet, and the transfer material has a polarity opposite to that of the toner image. Is applied. After that, in order to separate the transfer material from the supporting sheet, the corona discharger (static eliminator) was used.
The AC voltage and the DC voltage are applied by weight, and the AC current is applied to weaken the electrostatic attraction (Coulomb force) generated between the transfer material and the support sheet, and the separation claw is moved between the transfer material and the support sheet. In between, the transfer material is separated.

Further, in a transfer drum having a mechanical gripper, when the carrier sheet is formed in a drum shape, the gripper portion hinders the cleaning of the carrier sheet completely, and image formation is performed only in the gripper portion. There is a drawback that the area is narrowed and a so-called image lack occurs in that area.

Therefore, a corona charger is provided on the surface of the carrier sheet opposite to the transfer material holding surface, and a conductive roller is provided opposite the transfer material holding surface, and the transfer material is electrostatically moved with respect to the carrier sheet. Transfer material holding method (Japanese Patent Application Laid-Open
-32079) has been proposed. (Gripperless system).

In this case, it is conceivable to provide a means for correcting the deformation of the transfer material carrying sheet on the upstream side of the adsorption corona charger for adsorbing the transfer material to the transfer material sheet in order to enhance the adhesion between the transfer material and the transfer material carrying sheet. Can be It is also conceivable that a correcting means is similarly provided at the transfer position of the gripper system and the gripperless system.

[Problems to be Solved by the Invention] However, the correction means in the above conventional example is, for example, 15
Since the strain correcting means made of an elastic support member such as a 0 μm elastic sheet was used, the buffer-up force in the thrust direction (longitudinal direction) was different between the center and the end, and the end was weak. May cause poor transfer,
There was a drawback of causing poor suction.

[Object of the Invention] The present invention has been made in view of the above problems,
It is an object of the present invention to prevent transfer failure of a transfer material carried by a transfer material carrying means or poor transfer material adsorption to the transfer material carrying means.

Alternatively, an object of the present invention is to prevent deformation of the transfer material carrying means.

[Constitution of the Invention] In order to achieve the above object, the present invention relates to an image carrier for carrying a toner image, and the transfer material for transferring and bringing the transfer material into contact with the image carrier. A transfer material carrying means for carrying, a transfer means for transferring a toner image on the image carrier to a transfer material, and the transfer material carrying means at a transfer position where the image carrier and the transfer means face each other. A pressing member extending in the longitudinal direction of the transfer material holding means for pressing in the direction of the image carrier, supporting means for supporting the pressing member, and reinforcing means for reinforcing a longitudinal end of the pressing member; The present invention provides an image forming apparatus characterized by having the following.

The present invention also provides an image carrier for carrying a toner image, a transfer material carrier capable of carrying the transfer material for transporting and bringing the transfer material into contact with the image carrier, and Transfer means for transferring the toner image on the image carrier to the transfer material, suction means for adsorbing the transfer material to the transfer material support means, and transfer at a suction position where the image carrier and the suction means face each other. A pressing member extending in the longitudinal direction of the transfer material supporting means for pressing the material supporting means in the direction of the transfer material, a supporting means for supporting the pressing member, and reinforcing a longitudinal end of the pressing member; An image forming apparatus provided with reinforcing means is provided.

Examples Examples of the present invention will be specifically described below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a photosensitive drum as an image carrier, which is rotatably supported at the center of the drum and is driven to rotate in the direction of the arrow. Opposing the outer peripheral surface of the photosensitive drum 1,
A primary charger 2, an optical system 3, a developer supply device 4, and a secondary charger 5 are arranged in the rotation direction. The secondary charger 5 may not be provided. The primary charger 2 gives a uniform amount of charge to the photosensitive drum 1, and the optical system 3 applies a light image color-separated at a predetermined timing or a light beam L corresponding thereto to the photosensitive drum 1.
To form an electrostatic latent image. A laser beam exposure device or the like is used for the optical system 3. The developer supply device 4 is a movable type that moves in a tangential direction in opposition to the surface of the photosensitive drum 1, and includes a magenta developer, a cyan developer, a yellow developer, and a black developer. 4 developing units 4M, 4C, each storing color developer deletion separately
It has 4Y and 4BK. The developer supply device opposes the photosensitive drum 1 with a developing device selected in response to irradiation of a light image of a selected color by the optical system 3 or a light beam L corresponding thereto, and electrostatically flies toner. Thus, the toner image is developed on the surface of the photosensitive drum 1.

Further, the transfer drum 6 is located in the rotation direction of the photosensitive drum 1 and is in contact with or slightly apart from the surface of the photosensitive drum 1. The transfer drum 6 is formed by winding a supporting sheet 6a in a cylindrical shape between both end frames of a cylindrical shape. A transfer corona charger 7 is provided on the opposite side of the holding surface of the supporting sheet 6a opposite to the photosensitive drum 1. Are arranged. As this transfer drum, as in JP-A-56-57069, the cylindrical portions on both sides are connected by a band, and an insulating carrier sheet is formed on the frame formed by these structural frames. The front and rear ends are fixedly supported by the frame. The transfer drum 6 is rotatably driven in the direction of the arrow. An upstream side of the transfer position is a suction corona charger 19 on the opposite side of the holding surface, and a conductive roller opposing the holding surface. 20 are arranged respectively. Further, on the downstream side from the transfer position, corona dischargers 10 and 11 for static elimination are provided with the support sheet 6a interposed therebetween, and for separating the transfer material P (described later) from the support sheet 6a. Pressing corona 12, 13 is the supporting sheet 6a
, And a separating claw 14 is provided in the vicinity thereof. Further downstream, a brush roller 15 for cleaning the holding surface of the supporting sheet and, if necessary, a corona discharger or a brush type static eliminator 16 for removing an adhesive force (residual Coulomb force and van der Waals force) 16
Is provided.

Further, the transfer material P carrying the toner image separated by the separation claw 14 is supplied to the fixing roller 18 via the conveyor 17 to fix the image developed by the toner.

Further, on the upstream side of the transfer position, there are a corona charger 19 and a conductive roller 20 with the support sheet 6a interposed therebetween, and further immediately upstream thereof, the transfer material P is guided through registration rollers 21 and 21 by guides 22. Supply means for supplying a transfer material to be supplied to the holding surface of the support sheet 6a after being supplied to the holding sheet 6a.

In the drawing, reference numeral 27 denotes a static eliminator for removing electrostatic charges on the surface of the photosensitive drum 1, and reference numeral 28 denotes a cleaning blade for removing toner. If necessary, the transfer material P is provided near the separation claw 14.
In order to prevent the image from being disturbed by the peeling discharge that occurs when the sheet is separated from the support sheet 6a, it is preferable to install a corona discharger 29 and perform an AC corona discharge.

In such a configuration, the surface of the photosensitive drum 1 is
When the optical system 3 first irradiates a color image through a green filter, for example, in a state where the color image is uniformly charged, a latent image mainly composed of a magenta component in the color image is there. It is formed. In synchronization with the feeding of the latent image, the developer supply device 4 moves in the tangential direction with respect to the photosensitive drum 1 so that the developing device 4M containing the magenta developer faces the photosensitive drum 1. The toner electrostatically flies over the latent image to develop a magenta image on the photosensitive drum 1.

On the other hand, the transfer material P is introduced into the guide 22 by the action of the registration rollers 21 and 21 and further supplied to the position of the conductive roller 20 along the surface of the supporting sheet 6a. Here, the transfer material P
Is electrostatically attracted to and held on the supporting sheet 6a by the corona charger 19 and sent to a transfer position with the photosensitive drum 1. In this case, the timing of feeding the registration rollers 21 and 21 and
The timing of the latent image formation by the optical system 3 is synchronized, and the toner image on the image carrier and the transfer material on the transfer drum 6 coincide at the transfer position. At the transfer position, the corona charger 7 for transfer works to generate a transfer electric field, and the toner on the photosensitive drum 1 is held on the transfer material P by the charge of the opposite polarity to the toner applied to the carrier sheet.

After the toner remaining on the photosensitive drum 1 is neutralized by the neutralizer 27, it is removed by the blade 28, and the surface of the photosensitive drum 1 is cleaned. On the other hand, the transfer material P adsorbed on the supporting sheet 6a is transferred to the transfer drum 6 while carrying the toner development.
Moves as it rotates, and passes between the corona dischargers 10, 11, but at this time, the corona dischargers 10, 11 are not energized. Further, the pressing rollers 12, 13 are also separated from the supporting sheet 6a, and the brush roller 15 and the corona discharger or the brush type static eliminator 16 are also provided.
6a, the toner image on the transfer material P carried by the Coulomb force passes through the space between the corona charger 19 and the conductive roller 20 without being disturbed, and is again sent to the transfer position. The urging of the corona charger 19 and the contact of the conductive roller 20 with the transfer material P are completed before the leading end of the toner image of the transfer material P reaches the position of the corona charger 19 and the conductive roller 20. Therefore, when passing through the space, the charge for adsorption is not applied to the transfer material P. Further, the image formation with the magenta developer has been completed before the leading end of the toner image reaches the transfer position, and the optical system 3 has already irradiated the photosensitive drum 1 with a color image passed through a red filter. Since the developer supply device 4 shifts the developing device to make the developing device 4C face the photosensitive drum 1,
The toner flies electrostatically to the latent image to develop a cyan image on the photosensitive drum 1. Therefore, at the transfer position,
The toner development by the cyan developer is transferred on top of the toner development by the magenta developer.

In this manner, in the optical system, a green filter, a red filter, and a blue filter are sequentially applied to form a latent image obtained by performing color separation on the same image a plurality of times on the photosensitive drum 1, and a developer corresponding to the latent image, ie, magenta A color developer, a cyan developer and a yellow developer are supplied from the developer supply device 4 to the photosensitive drum 1 to realize color development as a whole. It is needless to say that the order of supplying the filter and the developer can be appropriately selected as needed.

Then, after the last toner image, in this embodiment, the image formed by the yellow developer, is transferred onto the transfer material P, when passing between the corona dischargers 10 and 11, these are energized to remove electricity. The pressing corona 12, 13 is the supporting sheet
The transfer material P is pressed against the support sheet 6a to increase the curvature at this portion, thereby helping the transfer material P to be separated from the support sheet 6a. Further, the separation claw 14 comes into contact with or approaches the carrier sheet 6a to separate the leading end of the transfer material P from the carrier sheet 6a and supply it to the fixing roller 18 via the conveyor 17, and the transfer material P performs toner development. Establish. At the time of separation, it is preferable to prevent the image from being disturbed due to the peeling discharge by the corona discharger 29.

In this manner, a color image can be copied. The optical system 3 does not use a filter, and the developer supply device 4 connects the developing device 4BK for the black developer to the photosensitive drum 1
, A normal black-and-white copy is realized.
In this case, since the transfer is performed only once, each component has a function corresponding to the case of the last development in color copying.

In addition, if necessary, a black image may be superimposed by white exposure and a black developer in the final stage of color development.

Incidentally, FIG. 2 shows a transfer carrying sheet straightening member disposed at the transfer position where the photosensitive drum 1 and the transfer corona charger 7 face each other and upstream of the transfer charger, that is, the carrying sheet 6a.
An example of the pressure distribution in the thrust direction (longitudinal direction) of the pressing member 7 ′ extending in the longitudinal direction of the transfer drum 6 in order to press in the direction of the photosensitive drum 1 is shown. The pressing member 7 ′ is an elastic sheet, has a thickness of 150 μm, a free length of 16 mm, and has a penetration amount of 5 mm. Pressure is generated by a so-called strainer of the elastic sheet. From this figure, it can be seen that the pressure at the end in the longitudinal direction is lower than the pressure at the center. The transfer is also shown threshold P ₀ to be performed stably. The pressure in the image area needs to be at least P ₀ above. On the other hand, if the pressure is too high, vibration occurs when the transfer drum frame connecting portion passes through the elastic sheet, and image blur occurs. FIG. 2 also shows the pressure threshold value P ₀ ′ at which image blur occurs.
Thus the pressure in the image area it is necessary that at P ₀ or P ₀ 'or less.

FIG. 3 shows the change over time in pressure. From this, it can be seen that the pressure decreases with time or the number of copies. (The solid line is at the center and the broken line is at the end.) Therefore, it is desirable that the pressure be substantially uniform at least initially in the image area.

FIG. 4 is a perspective view in which an auxiliary elastic sheet 30 is added as means for reinforcing the longitudinal end of the elastic sheet 7 '. Here, the elastic sheet 7 'is fixed by a back plate 8 made of a rigid plate as a support member. FIG. 5 shows the change over time in pressure when the end of the elastic sheet 7 'is reinforced as shown in FIG. (The solid line is the center and the broken line is the end.) From this figure, it can be seen that the pressing member is operating on the support sheet 6a stably in the image area.

Here, the pressing member of the transfer unit has been described, but the same applies to the pressing member at the suction position. That is, as shown in FIG. 1, the transfer sheet P is transferred at a suction position where the support sheet 6a and the corona discharger 19 serving as suction means for suctioning the transfer material P to the transfer drum 6 and the grounded conductive roller 20 face each other. A pressing member 19 'extending in the longitudinal direction of the transfer drum 6 is provided for pressing in the direction of the material P. This may have the same configuration as that shown in FIG.

FIG. 6 is a cross-sectional view in which the free length of the pressing member 7 'as the correcting member (the length of the portion where the pressing member 7' is not supported in the direction of arrow a is changed between the center and the end in the longitudinal direction. A hatched portion in the drawing is a back plate made of a rigid plate as a support means for supporting the elastic sheet 7 'as a pressing member, and as shown in Fig. 6, a sheet 7' as a means for reinforcing the end of the elastic sheet 7 '. In the longitudinal direction, the free length at the end is made shorter than the free length at the center, that is, the elastic sheet 7 'in the direction of the arrow is fixed to the back plate 8 longer at the end than at the center, so that the thrust direction is The pressure distribution is almost constant.

FIG. 7 is a perspective view in which the thickness of the elastic sheet 7 'as the pressing member is changed between the central portion and the longitudinal end portion of the pressing member. The pressure distribution in the thrust direction is made substantially constant by making the thickness of the end portion of the elastic sheet 7 'larger than the thickness of the center portion thereof as reinforcing means for the end portion in the longitudinal direction of the elastic sheet 7'.

Note that both of the pressing members for the support sheet 6a shown in FIGS. 6 and 7 can be used in both the transfer position and the suction position as described above.

In the above embodiment, the transfer material is electrostatically attracted to the transfer drum. However, the transfer material may be supported on the transfer drum by a gripper as in the related art. At this time, the pressing member can be used at the transfer position.

The transfer sheet 6a may be fixed to both sides of the transfer drum 6a, but if both sides are not fixed as in the present embodiment, the sheet 6a and the transfer material may be adhered during transfer. The nip is easy to remove and good. At this time, it is more effective to reinforce the end of the pressing member.

[Effects of the Invention] As described above, according to the present invention, the longitudinal end of the pressing member of the transfer material holding means is reinforced at the suction position or the transfer position, so that the pressure of the pressing member against the transfer material holding means in the longitudinal direction is enhanced. Could be made uniform. Further, since a stable pressure can be obtained even after long-time use of the apparatus, there is an effect that a high-quality image without defective suction or transfer omission can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an embodiment of the image forming apparatus of the present invention, FIG. 2 is an explanatory view for explaining a longitudinal pressure distribution of an elastic sheet, and FIG. 3 and FIG. FIG. 4, FIG. 6, and FIG. 7 are schematic diagrams showing examples of elastic sheets for pressing the transfer drum applicable to the image forming apparatus of the present invention. In the drawing, 1 ... Photoconductor drum 2 ... Primary charger 3 ... Scanner 4 ... Developer 6 ... Transfer drum 7 ... Transfer charger 7 '... Pressing member 19' ... Pressing member 10 ... Outside Static eliminator 11… Inner static eliminator 14… Separation claw 15, 16… Transfer drum cleaner

Claims (6)

(57) [Claims] An image carrier for carrying a toner image, a transfer material carrier capable of carrying the transfer material for transporting and bringing the transfer material into contact with the image carrier; Transfer means for transferring the toner image on the image carrier to a transfer material,
A pressing member that extends in a longitudinal direction of the transfer material holding unit to press the transfer material holding unit toward the image holding unit at a transfer position where the image holding unit and the transfer unit face each other;
An image forming apparatus comprising: support means for supporting the pressing member; and reinforcing means for reinforcing a longitudinal end of the pressing member. 2. An image carrier for carrying a toner image, a movable transfer material carrier for carrying the transfer material for transporting and bringing the transfer material into contact with the image carrier; Transfer means for transferring the toner image on the carrier to the transfer material, suction means for adsorbing the transfer material to the transfer material support means, and the transfer material at a suction position where the image carrier and the suction means face each other. A pressing member extending in the longitudinal direction of the transfer material holding means for pressing the holding means in the direction of the transfer material, a support means for supporting the pressing member, and a reinforcement for reinforcing a longitudinal end of the pressing member And an image forming apparatus. 3. The image forming apparatus according to claim 1, wherein the pressing member is an elastic sheet. 4. The image forming apparatus according to claim 1, wherein said reinforcing means includes an auxiliary elastic sheet provided at a longitudinal end of said pressing member. 5. The image forming apparatus according to claim 1, wherein said reinforcing means has a different free length of said pressing member at an end in said longitudinal direction with respect to a longitudinal direction of said pressing member. 6. The image forming apparatus according to claim 1, wherein said reinforcing means has a thickness of said pressing member at an end in said longitudinal direction different from a longitudinal direction of said pressing member.