JP2558674B2 - Multiple copying machine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a multiple image forming apparatus that transfers a plurality of images formed on a latent image bearing member by superimposing them on the same transfer paper.

A conventional full-color copying machine or full-color printer in which a color-separated light image is exposed on a photoconductor, the latent image formed is developed with a toner of a complementary color of each color-separated light, and the images are superposed and transferred onto the same transfer paper. Alternatively, in a multiple image forming apparatus such as a multicolor copying machine that separately exposes images of different colors, develops them with different colors, and transfers them by superimposing them on the same transfer paper, the position of each image to be transferred is adjusted. It is one of the biggest technical problems. If the position of each color image on the transfer paper shifts, so-called color shift occurs,
Especially in the case of thin lines, it is very difficult to see.

Conventionally, in this type of image forming apparatus, as a means for accurately aligning images of a plurality of colors transferred onto a transfer paper, the transfer paper is wound around a transfer drum provided in contact with the photosensitive drum at the transfer position. The transfer drum is rotated at the same linear speed in synchronism with the photoconductor drum by engaging gears provided on the shafts of the transfer drum and the photoconductor drum. It is well known that the image forming apparatus is separated from the transfer drum and fixed to form a multiple image. However, in the multiple image forming apparatus using the transfer drum, the peripheral length of the transfer drum is required to be equal to or longer than the length of the transfer paper, and the diameter is usually the same as that of the photoconductor drum, and the occupied space becomes large and the device becomes large. There is a drawback to Further, the copying speed is the same for all transfer paper sizes, and the copying speed for small size paper cannot be improved. or,
If the transfer paper is small and has a large thickness, such as a business card or a postcard, or if the paper has a strong rigidity, it may not fit well on the transfer drum and the position may shift.

A full-color copying machine that transfers images via a transfer belt has also been proposed. However, when a transfer belt cleaning or static eliminator is required, or when the transfer belt is biased, misalignment of superimposed images occurs. However, there is a drawback that the image quality is significantly impaired.

In view of the above-mentioned drawbacks of the conventional multiple copying apparatus, the present inventor firstly found that the latent image carrier on the drum, the transfer charger and the separation charger provided along the latent image carrier in the order of their circumferential movement. And a transfer material transporter capable of reciprocating linear movement in a transfer portion between these two chargers and the latent image carrier, and the transfer material transporter transfers the latent image carrier in a transfer step. The toner image formed on the latent image carrier, which is moved in the same direction at the same speed as the linear velocity in the section and is formed on the latent image carrier, is transferred to the transfer material carried by the transfer material carrier
We proposed a multiplex copying apparatus in which a plurality of toner images are multiple-transferred onto a transfer material that is reciprocally transported by returning the transfer material transporter from the transfer end position to the transfer start position until the transfer of a predetermined number of times is completed.

With this configuration, it is possible to realize a desktop full-color copying machine that is compact and can perform multiple copying on thick paper such as postcards.

In this copying machine, similarly to the conventional copying machine, the transfer portion is provided with the transfer charger and the separation charger in the order of the circumferential direction along the latent image carrier. In a conventional general copying machine, the toner image on the latent image carrier is sequentially transferred as the paper moves by the transfer charger in which a direct current is applied to the corona wire, and the transferred portion is sequentially transferred after the transfer. An alternating voltage is applied to the corona wire to separate it from the latent image carrier and convey it to the fixing section.

On the other hand, in the multiplex copying apparatus proposed by the present invention,
Since the front end of the transfer material is gripped by the transfer material transfer body and is drawn in the tangential direction of the latent image carrier to be transferred, the separation performance after transfer is good. However, in the returning step, the surface of the transfer material carrying the unfixed toner image moves in a direction opposite to the moving direction of the peripheral surface of the latent image carrier, so that the unfixed toner image touches the latent image carrier and is disturbed. In order to prevent this, it is required to improve the separation performance so that the transfer material can be reliably separated from the latent image carrier and returned.

In view of the above situation, the present invention can improve the transfer efficiency in the transfer step and the separation performance in the return step in the multiple copying apparatus having the above-mentioned configuration proposed by the present inventor. An object is to provide a multiple copying apparatus.

In order to achieve the above object, the present invention provides a latent image carrier, a corona discharger provided at a transfer portion of the latent image carrier, and a corona discharger between the corona discharger and the latent image carrier. And a transfer material conveyer capable of reciprocating linear movement in the transfer part, and the transfer material conveyer moves the transfer material synchronously in the same direction at the same speed as the linear velocity in the transfer portion of the latent image carrier. A transfer step in which a toner image formed on the latent image carrier is transferred to a transfer material carried by a transfer material carrier, and the transfer material carrier transfers the transfer material from a transfer end position to a transfer start position. In the multiplex copying apparatus in which a plurality of toner images are multiple-transferred onto the transfer material which is reciprocally transferred, the DC voltage is applied to the corona discharger in the transfer step. However, in the above returning process, it is possible to selectively apply the AC voltage. The is characterized in that provided.

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

FIG. 1 is a diagram showing an overall schematic configuration of an embodiment in which the present invention is applied to a full-color copying machine.

In the figure, 1 is a document table which reciprocates left and right, 2 is a document illumination lamp, 3 is a fiber lens array as an exposure system, and 4 is a photosensitive drum. Photoconductor drum 4
Around the circumference of, there are provided a charging charger 5, an exposure position by the exposure mathematical system 3, and four color developing units of yellow, magenta, cyan, and black in the order of the rotation direction shown by an arrow,
Development device 6 capable of developing color switching in a rotation system in the direction of the arrow (revolver system), transfer charger 7 as a corona discharger
Further, there is provided a cleaning device 10 including a separation charger 8, a pre-cleaning charge removal charger 9, and a cleaning blade 10a. A color separation filter 11 for blue, green, three primary colors of red, and yellow is provided so as to be switchable in the optical path from the fiber lens array to the exposure position of the photosensitive drum 4. With the color separation filter 11 and the developing device 6, the blue filter is brought to the operating position where the yellow developing unit is in contact with the photoconductor when it is inserted in the optical path, and the magenta developing unit is inserted when the green filter is inserted. The cyan developing unit is switched when the red filter is inserted, and the black developing unit is switched to the operating position when the yellow filter is inserted.

In order to improve transferability, the pre-transfer exposure device 25, or
The provision of the pre-transfer transfer material charge eliminating device 27 is effective in transferring the toner images in multiple layers.

An AC corona charger is usually used as the pre-transfer static eliminator. In this example, it is provided on the toner image bearing side of the transfer material, but the effect can be obtained even if it is provided on the back surface of the transfer material, and the effect can be obtained by providing a static eliminator on both sides.

The transfer paper 15 is fed from the paper feeding cassette 12 to the transfer portion between the transfer charger 7, the separation charger 8 and the photosensitive drum 4 through the pick-up roller 13 and the registration roller 14.

A gripper that grips the front end of the transfer paper so as to be capable of reciprocating linear movement in the tangential direction of the photosensitive drum 4 from the transfer section to the discharge side.
A transfer paper transport member 17 having 16 is provided. The transfer paper conveying member 17 is formed as, for example, a sliding member guided by a guide member extending in the tangential direction of the photosensitive drum at the transfer position, and the rack fixed to the member 17 is coaxial with the photosensitive drum 4. Is provided on the photoconductor drum 4 at least during transfer.
When it is transferred, it moves in the transfer paper discharge direction at the same linear velocity as the photoconductor by meshing with a gear that rotates integrally with the. This moving stroke is approximately equal to the length of the transfer paper. Reference numeral 17 'in FIG. 1 indicates the most advanced position of the transfer sheet conveying member 17. The guide member from the registration roller is retracted downward so that the registration paper is not blocked by the registration roller 14 when the transfer paper retreats.

Regarding the full-color image formation process, when performing mono-color image formation, the guide belt from the registration rollers is held up and the transfer paper conveyance member 17 is retracted, and the conveyance belt is directed toward the fixing unit. High-speed copying is possible by holding the image and operating the image forming process.

The fixing device 22 is located above the moving path of the transfer paper carrying member 17 so as not to interfere with the reciprocal movement of the transfer paper carrying member 17. The transfer paper 15 that has been transferred a predetermined number of times is conveyed to the fixing device 22, so that the transfer paper 15 and the fixing device 22 are located slightly downstream of the transfer portion.
A transfer paper conveyance belt 23 is provided between the upstream side of the transfer paper so as to be swingable about the transfer portion side. The transfer paper transport belt 23 has a suction casing 24 inside, and when the transfer paper after the completion of transfer enters the fixing step, the transfer paper front end is moved to the suction part of the transfer paper transport belt 23 and is shown in the figure. The gripper release mechanism releases the gripper 16 of the transfer paper conveying member 17, adsorbs the front end of the transfer paper 15 to the conveying belt 23, advances the transfer paper conveying member 17 to the position 17 ', and moves the front end of the conveying belt 23. The conveying direction is raised so as to face the fixing device 22, and the transfer belt 23 conveys the transfer paper toward the fixing device.

Further, the gripper releasing mechanism is provided slightly on the fixing unit side so as not to interfere with the swinging of the conveying belt from the end of the conveying belt on the fixing unit side, and the gripper is opened to swing the conveying belt toward the fixing unit. , It is desirous to forcibly release the transfer material from the gripper.

The configuration described so far is no different from the configuration of the multiple copying machine previously proposed by the present inventor.

In the apparatus of this embodiment, as shown in FIG. 2, the separation charger 8 is switchably connected to the DC high voltage power source T1 and the AC high voltage power source S1 via the high voltage relays RT1 and RS1. A DC high voltage power supply T2 and an AC high voltage power supply S2 are switchably connected to 7 via high voltage relays RT2, RS2.

Sensors 30, 31, 32 and 33 for detecting the transfer start, transfer end, return start and return end of the transfer paper transport member 17 that grips the front end of the transfer paper 15 with the gripper 16 are in the moving path of the transfer paper transport member 17. The detection signals of the respective sensors are provided along the line and are input to and processed by the drive circuit 34, and the outputs thereof are supplied from the high voltage relay power supply 35 to the four high voltage relays RT1, RS1, RT2.
And a switch circuit 36 for turning on / off the circuits up to RS2. As a result, the DC voltage and the AC voltage can be selectively applied to the corona wires of the transfer charger 7 and the separation charger 8, respectively, or neither voltage can be applied.

The above DC high-voltage power supplies T1 and T2 can normally generate a DC voltage of ± 4.0 to ± 10.0 KV, and the polarity thereof is such that the electrostatic latent image formed on the photoconductor 4 is developed by the developing device 6. The polarity opposite to the polarity of the toner at that time is selected. Further, the AC high voltage power supplies S1 and S2 can usually generate an AC voltage of 3 to 8 KV. Further, a DC voltage can be superimposed and applied to the AC high-voltage power supplies S1 and S2 as needed.

 The operation of this device will be described below.

When the transfer material conveying member 17 carrying the front end of the transfer paper 15 by the gripper 16 moves to the left in the drawing from the transfer start position to perform the transfer process, the transfer start signal of the transfer start sensor 30 is input to the drive circuit 34. The output drives the switch circuit 36 to turn on the high voltage relay RT2, and the high voltage DC power supply T
By 2, a high DC voltage is applied to the corona wire of the transfer charger 7. At this time, in order to enhance the transfer efficiency of the toner image on the photosensitive drum 4, no voltage is applied to the corona wire of the separation charger 8 or a high voltage relay is used.
It is convenient to turn on RT1 and apply a DC voltage of the same polarity as the DC voltage applied to the transfer charger from the DC high voltage power supply T1. In this case, the multiple transfer property can be improved by setting the absolute value of the DC voltage applied to the separation charge 8 to be larger than the absolute value of the DC voltage applied to the transfer charge 7. When the transfer material conveying member 17 reaches the transfer end position, the transfer end signal from the transfer end sensor 31 causes the high voltage relay RT1 to pass through the drive circuit 34 and the switch circuit 36.
(And RT2 if it's turned on) turns off,
The DC voltage application to the transfer charger 7 (and the separation charger 8) is cut off.

Next, in the return process, the high voltage relay RS1 is turned on by the return start signal of the return start sensor 32 and the high voltage AC power supply 3
High-voltage alternating current is applied to the separation charger 8 from 1 to transfer paper 1
5 is electrostatically separated from the photoconductor drum 4, and the unfixed toner image on the transfer paper is prevented from coming into contact with the photoconductor 4 and disturbed. In this case, no voltage is applied to the transfer charger 7, or the high voltage relay RS2 is turned on and a high voltage AC voltage is applied to the transfer charger 7 from the high voltage AC power source S2 in order to further enhance the separating action of the transfer paper.

FIG. 3 shows the transfer start, the transfer end, the return start and the return end when the transfer charger applies a DC voltage of the same polarity to the separation charger in the transfer process and the AC voltage is applied to both the chargers in the return process. The timing chart showing the transmission of each signal and the on / off timing of the high voltage relays RT1, RT2, RS1 and RS2 is shown.

As described above, according to the present invention, in the multiplex copying apparatus that performs multiple transfer by moving the transfer material back and forth at the transfer portion, the transfer efficiency is improved in the transfer step, and the toner material on the transfer material in the return step is increased. It is possible to effectively prevent the occurrence of turbulence due to contact with the latent image carrier.

[Brief description of drawings]

FIG. 1 is a side sectional view showing a schematic structure of a multiplex copying apparatus in which the present invention is used, FIG. 2 is a circuit diagram showing an embodiment of a control circuit of the present invention, and FIG. 3 is an example of its timing chart. is there. 4 ... Photosensitive drum (latent image bearing member), 6 ... Developing device, 7 ... Transfer charge, 8 ... Separation charge, 30 ... Transfer start sensor, 31 ... Transfer end sensor, 32 ... Return start Sensor, 33 …… Return end sensor, 36 …… Switch circuit, RT1, RT2, RS1, RS2 …… High voltage relay, T1, T2 …… DC high voltage power supply, S1, S2 …… AC high voltage power supply

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location G03G 21/14 G03G 21/00 372

Claims (5)

(57) [Claims] 1. A reciprocating linear movement is possible between a latent image carrier, a corona discharger provided in a transfer part of the latent image carrier, and a transfer part between the corona discharger and the latent image carrier. A transfer material carrier, and the transfer material carrier is formed on the latent image carrier by moving the transfer material synchronously in the same direction at the same speed as the linear velocity in the transfer portion of the latent image carrier. A transfer process in which the toner image is transferred to the transfer material carried by the transfer material carrier and is returned to the transfer material from the transfer end position to the transfer start position by a predetermined number of times. In a multiplex copying apparatus in which a plurality of toner images are repeatedly transferred onto a transfer material which is repeatedly conveyed until the transfer is completed, a DC voltage is applied to the corona discharger in the transfer step and an AC voltage is applied in the return step. Multiple duplication characterized by being provided in a selectively applicable means Copy device. 2. A corona discharger is a transfer charger and a separation charger which are provided along the latent image carrier in the order of its circumferential direction, and a direct current is applied to at least the transfer charger in the transfer step by the applying means. A voltage is applied, and an AC voltage is applied to at least the separation charger in the returning step.
The multiplex copying apparatus as described in the item. 3. The multiple copying apparatus according to claim 2, wherein a DC voltage is applied to the separation charge in the transfer step. 4. The multiple copying apparatus according to claim 3, wherein the DC voltage applied to the separation charger is higher than the DC voltage applied to the transfer charger. 5. The multiple copying apparatus according to claim 2, wherein an AC voltage is also applied to the transfer charger in the returning step.