JPH02285368A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent the occurrence of transfer detects by stopping an image carrier after the surface of the image carrier facing a developing part comes to a position where the carrier is confronted with a transfer means if jamming occurs. CONSTITUTION:When a toner image comes to a transfer position where a photosensitive body 1 and a transfer roller (transfer means) 5 come into press-contact with each other to form an image, a transfer material P arrives at the transfer position at the same timing as when the toner image arrives, and the toner image on the photosensitive body 1 transfers onto the transfer material P by the action of a bias voltage applied by a power source 9. If jamming occurs when the transfer means 5 transfers, the travel of the photosensitive body 1 is stopped after the surface of the photosensitive body 1 facing a developing unit 4 passes by the position of the transfer means 5. Consequently, transfer defects in printing after jamming is removed and the soil of the back of the transfer material P can be prevented to obtain an excellent image.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Object of the Invention (Field of Industrial Application) The present invention relates to an image forming apparatus using an electrostatic transfer process, such as an electrostatic copying machine and a printer thereof.

(Prior art and problems to be solved) A transferable toner image formed on the surface of a moving image carrier is transferred into a sheet mainly made of paper by a transfer roller or a contact type transfer means that comes into contact with the image carrier. An image forming apparatus that includes a step of transferring images onto a transfer material has already been proposed.

FIG. 5 is a schematic side view showing a typical configuration of such an image forming apparatus, and the illustrated apparatus is a cylindrical-formed image extending perpendicular to the plane of the paper and rotating in the direction of the arrow. A carrier (referred to as a photoreceptor) 1 is provided, and after the surface of the photoreceptor is uniformly charged by a wide charger 2, an optical image signal 3 such as an image-modulated laser beam is applied to this charged surface to static electricity. An electric latent image is formed, and then, when this latent image reaches a development site opposite to the developing device 4, toner is supplied by the developing device and the latent image is visualized to form a toner image.

On the downstream side of the developing device 4 (as viewed in the traveling direction of the photoreceptor 1),
A transfer roller 5 made of a conductive elastic material is placed in pressure contact with the photoreceptor 1 to form a transfer site, and when the toner image arrives at this position, the transfer material P is moved to the photoreceptor 1 at the same timing. The toner image is supplied to the transfer site, and a transfer bias is applied to the transfer roller 5 by the power source 5a, so that the toner image on the photoreceptor side is transferred to the transfer material.

After the transfer, the transfer material carrying the toner image is conveyed to a fixing site (not shown), and the toner image is fixed and fixed on the transfer material.
Residual toner that has not been transferred to the transfer material during transfer is cleaned at the cleaner 6, and after the residual charge is removed by the pre-exposure lamp 11, the photoreceptor 1 is ready to perform the image forming process again. It is assumed that the charger reaches the position of the charger 2.

A contact type transfer means such as a transfer roller that constitutes a transfer site is more difficult to use than a transfer means that uses a known charger.
Toner is less likely to fly away due to excessive charge being applied to the back of the transfer material, and since the transfer material is firmly held at the transfer site, there is less risk of transfer misalignment (,
Furthermore, in the case of reversal development, there is an advantage that a low bias voltage is required to be applied to the transfer roller.

However, in this type of image forming apparatus, it is difficult to completely prevent the supplied transfer material from jamming during transportation and rendering the work impossible. From the point where we start supplying
Since jams can occur in any part up to the fixing site, all parts of the apparatus are normally configured so that when a jam occurs, all parts of the apparatus detect this and stop the jam.

However, in a device using a transfer roller as described above, if all members are configured to stop at the same time, the following problems occur.

In other words, if each part of the apparatus stops due to a jam while the transfer process is in progress, the toner image in the area shown by the symbol J between the developing device 4 and the transfer site in the previous figure will remain as it is. Therefore, when you start work after a jam, some of the toner in that area will adhere to the transfer roller, which may cause stains on the back of the subsequent transfer material, or may affect the transfer ability of the transfer roller depending on the amount of adhered toner. There is a possibility that this may affect the image quality and cause transfer defects.

The present invention has been made to deal with such a situation, and even if a jam occurs in an image forming apparatus equipped with a photoreceptor and a transfer means that comes into contact with the photoreceptor, the transfer material will be removed when printing is restarted. It is an object of the present invention to provide an image forming apparatus that can prevent contamination and transfer defects from occurring, and can always stably obtain good images.

(2) Structure of the invention (technical means for solving the problem, its operation) In order to achieve the above object, the present invention comprises an image carrier, a charging means that moves relative to the image carrier, an optical image signal applying means, In an image forming apparatus equipped with a developing means and a transfer means that comes into contact with the image carrier, if a jam occurs during transfer by the transfer means, the surface of the image carrier facing the developing means may be The image carrier is characterized in that the traveling of the image carrier is stopped until it passes the position.

With this configuration, in the image forming apparatus as described above, it is possible to prevent transfer failures and stains on the back of the transfer material during printing after jam removal, and to obtain high-quality images.

(Description of Embodiments) FIG. 1 is a schematic side view of the configuration of a laser beam link showing an embodiment of the present invention, which is equipped with a cylindrical OPC photoreceptor 1 that rotates in the six directions indicated by the arrows shown in FIG. Parts corresponding to those in the illustrated apparatus are designated by the same reference numerals.

It is assumed that the surface of the photoreceptor 1 is uniformly charged to 1700 cm by the wide charger 2 by applying a high voltage from the power supply 10.

Next, an electrostatic latent image is formed on the charged surface by scanning with the image-modulated laser beam 3, and when this latent image arrives at a developing position facing the developing device 4 as the photoreceptor 1 rotates, the developing device Toner is supplied from No. 4 and adheres to the latent image (the portion irradiated with the laser beam), forming a toner image using a one-reversal developing force method.

At this time, a developing bias consisting of alternating current and direct current (approximately 1,500 cm at the time of image formation in the illustrated apparatus) is applied to the developing sleeve 4a in the developing device by the alternating current power supply 7 and the direct current power supply 8. shall be taken as a thing.

Further, when this toner image reaches the transfer site formed by pressure contact between the photoreceptor 1 and the transfer roller 5, by this time the transfer material P has arrived at this transfer site in synchronization with the toner image, The toner image on the photoreceptor 1 is transferred to the transfer material under the action of a bias voltage applied by a power source 9.

The transfer roller 5 was made of an elastic material whose resistivity was adjusted to be less than 10' ΩcltI, and a bias of approximately +500 μ was applied thereto to perform the transfer.

After completing the transfer and leaving the transfer site, the transfer material is conveyed to a fixing site (not shown), where the toner image is fixed and fixed to the transfer material, and then discharged from the apparatus.

On the other hand, residual toner remaining on the photoreceptor 1 without being transferred to the transfer material at the transfer site is cleaned at the position of the cleaner 6 as the photoreceptor rotates, and furthermore, the residual charge on the photoreceptor is erased by the pre-exposure means 11. The photoreceptor is ready for the next process.

FIG. 2 shows the printing sequence by the device described above.

In the figure, the part A indicates a sequence in which normal printing is executed, and the part B in the figure shows a sequence when a jam occurs.

To briefly describe the sequence of part A, the photoreceptor 1, developing sleeve 4a, and transfer roller 5 start rotating in response to a print start signal, and at the same time, the pre-exposure 11 is turned on.

Then, after a delay time until the rotation of the photoreceptor 1 stabilizes,
- The wide charger 2 is turned on, and the DC bias power supply 8 is set to the antifogging bias value.

If this bias value is too large, toner charged to the normal polarity will cause blurring, and if it is too small, toner charged to the opposite polarity will cause reverse fogging, so -500
V is about -700V.

When the pre-process is completed and the photosensitive surface is uniformly charged, a latent image is written on the charged surface by scanning with an image modulated laser beam, and the image is synchronized with the image position. An image output bias is applied by an AC bias power supply 7 and a DC bias power supply 8.

The bias voltage at this time is AC with a peak-to-peak voltage of 1so
v, DC was set to -500v.

At the transfer site, as the image progresses on the photoreceptor,
A bias voltage of +500V is applied to the transfer roller 5 by the transfer bias power supply 9 to perform printing.

After printing is completed, the AC power supply 7 is turned off, the DC power supply 8 is turned off for the fog removal bias, and then the transfer bias power supply 9 and the wide charger 2 are turned off in sequence, and the fog removal bias is also turned off.

After that, the rotation of the photoconductor 1 etc. is stopped and the pre-exposure 1 is
1 is also turned off and the entire process is completed.

Next, we will explain what to do when a jam occurs.

As mentioned above, when a jam occurs, for safety reasons, it is common practice to stop the operation of all the members that are in operation at that time, but in the present invention, the symbol J in FIG.
A jam stop process is provided to treat the area where toner exists, as shown in FIG. , a photoreceptor l, a transfer roller 5, and a developing sleeve 4a.
is rotated to turn off the optical image exposure 3 and the AC portion 7 of the developing bias, and switch the developing bias DC portion 8 to the fog removal bias.

The antifogging bias at this time may be -500 to -700V as in the normal case described above, but since an image is also written between the photoimage exposure section 3 and the development section, toner should not adhere to that section. Considering this, although there is a risk of reverse fog, it is better to lower this bias (approximately 0 to -500 V).

FIG. 3A shows the state at the start of the jam stop process when such control is executed, and FIG. 3B shows the state at the end of the same process.

In reality, in the case of a photoreceptor having a diameter of 30 mm, the circumferential length of the region J was approximately 27 mm, which was found to pose no safety problem.

It is preferable that the photoreceptor 1 is rotated during the jam stop process from the photoimage exposure area 3 to the transfer roller 5, if there is enough time.

As explained above, by providing the jam stopping process, toner on the surface of the photoreceptor is removed during jam removal.
It has become possible to eliminate contamination of the transfer roller, contamination of the transfer material caused by the contamination of the transfer roller, and defective transfer during the subsequent image forming process.

Although not shown in the apparatus of the embodiment, the transfer material leaving the transfer site is of course conveyed to the fixing device, and the fixing device includes a pair of rollers that press against each other, and The transfer material is inserted into the pressure nip of the transfer material, and heat and pressure are applied to the transfer material at this time to fix the toner image (as is well known in practice).

In the case of such a device, if the fixing device is driven separately from the image forming section including the photoconductor, the fixing device can be stopped as soon as a jam is detected, so there is no safety problem even if the photoconductor rotates for a while during the jam stopping process. It's very convenient.

Furthermore, if the drive system of the photoreceptor is made similar to that of other members, better control becomes possible.

FIG. 4 shows a timing chart in the above case, in which the pair of fixing rollers in the fixing device and the developing sleeve are also stopped.

By setting the operation timing of each member in this way, the fixing device stops after a jam occurs, so even if the photoconductor is rotating, no wrapping occurs at the fixing area.The developing device stops, so the photoconductor The adhesion of toner to
Combined with the application of the anti-fogging bias, the bias to the transfer roller can be reduced to -500V, for example, by switching the polarity of the power supply 9 at a time other than during the printing process.
By applying a reverse bias of Furthermore, since the toner on the photoreceptor is not transferred to the transfer material during this time, there is an advantage that when an operator clears a jam, he or she does not get his or her fingers dirty with unfixed toner.

Additionally, if a jam is detected before or after a toner image is formed on the photoreceptor, it goes without saying that there is no problem in immediately stopping the photoreceptor. Although the case where a transfer roller is used as the transfer means has been described in , it is easy to understand that the present invention can also be applied to other contact type transfer means such as a transfer belt.

(3) As described in detail, according to the present invention, when a jam occurs in an image forming apparatus having a transfer means such as a transfer roller that comes into contact with an image carrier, the surface of the image carrier facing the development area By waiting for the image carrier to reach a position facing the transfer means on the downstream side as viewed in the running direction, and then stopping the image carrier, the occurrence of stains on the back side of the transfer material, transfer defects, etc. can be prevented, This is effective in obtaining high-quality images.

[Brief explanation of drawings]

FIG. 1 is a schematic side view of main parts showing the configuration of an image forming apparatus suitable for applying the present invention, FIG. 2 is a timing chart showing an embodiment of the present invention, and FIGS. 3A and 3B are in accordance with the present invention. FIG. 4 is a timing chart showing another embodiment of the present invention, and FIG. 5 shows the behavior of toner in a known image forming apparatus. It is an explanatory diagram to explain. DESCRIPTION OF SYMBOLS 1... Photoreceptor, 2... Wide charger, 3... Optical image signal applying means, 4... Developing device, 4a... Developing sleeve, 5... Transfer roller. Engraving of the drawings (no changes to the content) Figure 1 Figure 3A Teitouri Neho Seisho () Ebisu) October 9, 1989

Claims (2)

[Claims] (1) In an image forming apparatus equipped with an image bearing member, a latent image forming means that moves relative to the image bearing member, a developing means, and a transfer means that comes into contact with the image bearing member, when the transfer means is performing transfer. An image forming apparatus characterized in that, when a jam occurs, the image bearing member stops traveling until the surface of the image bearing member facing the developing means passes the position of the transfer means. (2) The image forming apparatus according to claim 1, wherein the bias voltage applied to the developing means after a jam occurs is different from that during development.