JP2003186263A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a photoreceptor drum side from being broken by immediately detecting a transfer belt having a pinhole and to carry on image forming operation without replacing the transfer belt having the pinhole. <P>SOLUTION: A controller 40 when judging that the transfer belt 20 has the pinhole on the basis of detection information inputted from a power pack 52 and also specifying the position of the pinhole on the basis of a detection signal of an HP mark inputted from an HP sensor and when judging that the pinhole is smaller than a specified size, controls the moving speed of the transfer belt 20 and the application timing of a transfer bias so that a transfer material is not carried at the position of the pinhole of the transfer belt 20. Consequently, side of a photoreceptor 25 is prevented from being broken and the image forming operation can be carried on without replacing the transfer belt 20. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer or a facsimile which forms an image by utilizing an electrophotographic system or an electrostatic recording system.

[0002]

2. Description of the Related Art A plurality of (for example, four) photoconductor drums are provided, and a plurality of image forming portions for forming toner images of different colors are provided on the respective photoconductor drums. A transfer material (transfer paper) such as paper is conveyed to each of these image forming sections by a belt, and toner images of different colors (generally yellow, magenta, cyan, and black) are sequentially superimposed and transferred, and the transfer material surface An image forming apparatus that forms a color image is known, and is applied to a color copying machine, a color printer, a color facsimile, and the like.

An image forming apparatus using such a plurality of photosensitive drums and a single transfer belt forms a single photosensitive member by forming a toner image of each color on each photosensitive drum for each printing color. It has an advantage that the image output time per sheet is short as compared with an image forming apparatus that forms a color image by rotating the drum a plurality of times to form toner images of different colors.

In the case of an image forming apparatus having a plurality of image forming sections as described above, a transfer material such as paper is electrostatically adsorbed on the transfer belt, and the transfer belt is rotated to drive the transfer material. The sheet is conveyed to the transfer section between the photosensitive drum and the transfer member. Therefore, the transfer belt needs to be an insulator in order to attract the transfer material to the transfer belt. Further, the attracting force of the transfer material is proportional to the amount of electric charge applied to the transfer belt, and in general, in order to make the structure compact, the application of electric charge for adsorbing the paper requires a value of 1 in the most upstream side image forming unit.
It is performed at the same time as the transfer of colors.

Therefore, the lower limit value of the transfer bias applied in the transfer of the first color is determined by the amount of charge required to attract the transfer material to the transfer belt. Further, in this configuration, since the transfer belt is an insulator, electric charges remain on the transfer belt. Therefore, the transfer bias of the second color should be larger than that of the first color, and the transfer bias of the third color should be larger than that of the second color. That is, a transfer bias of a considerably high value (hereinafter referred to as a high transfer bias) is applied to the fourth color.

By the way, although the application of the high transfer bias is not a problem in a normal state as described above, for example, when dust or air bubbles are mixed in the transfer belt in the manufacturing process,
When dust attached to the transfer belt is caught between the rollers that stretch the transfer belt, a cleaning member (cleaning blade) that cleans the transfer belt surface rubs the transfer belt surface and the transfer belt surface deteriorates. In such a case, the application of the high transfer bias causes dielectric breakdown of the transfer belt, resulting in a defect that a pinhole is formed in the transfer belt.

Further, even when a part of the transfer belt surface is erroneously damaged during maintenance or jam treatment, the high transfer bias is applied to cause dielectric breakdown of the transfer belt, and thus the transfer belt. There will be a problem with pinholes.

Further, when a high transfer bias is applied to the transfer belt in which the pinhole is generated, electric charges are concentrated there,
This causes a problem that a part of the surface of the photosensitive drum that abuts at the transfer portion is damaged. When an image is output from the photoconductor drum whose surface is partially damaged, the damaged part appears as white spots or black spots on the output image, so the photoconductor drum must be replaced. Normal image output cannot be performed.

Therefore, in order to solve such a problem, the apparatus is stopped when a pinhole of the transfer belt is detected, as disclosed in Japanese Patent Laid-Open No. 9-311523. An image forming apparatus has been proposed.

[0010]

However, in the image forming apparatus in which the apparatus is stopped when the pinhole of the transfer belt is detected as described above, the apparatus is stopped when the pinhole of the transfer belt is detected. The image forming operation is stopped midway. Therefore, there is a drawback that the image forming operation cannot be restarted unless the transfer belt having the pinhole is removed and replaced with a new transfer belt.

Further, even in an image forming apparatus in which a toner image formed on a single or a plurality of photosensitive drums is once transferred onto an intermediate transfer belt serving as an intermediate transfer member and then transferred onto a transfer material such as paper. When holes were generated in the intermediate transfer belt, the image forming operation could not be restarted without replacing the intermediate transfer belt with a new one as described above.

Therefore, the present invention is directed to an image forming apparatus using a transfer belt (transfer material carrying member) or an intermediate transfer belt (intermediate transfer member) when a damage such as a pinhole occurs on the transfer belt or the intermediate transfer belt. Immediately detect the damage on the photosensitive drum side, and even if the transfer belt or the intermediate transfer belt is damaged such as pinholes, the image forming operation can be continued without replacing them. An object is to provide an image forming apparatus.

[0013]

In order to achieve the above object, the invention according to claim 1 is an image carrier on which a toner image is formed, and a transfer member contacting the image carrier at a transfer section,
A transfer bias applying unit that applies a transfer bias to the transfer member, and the transfer member are installed so as to pass through the transfer unit between the image carrier and the transfer member. The transfer material is carried on the surface and conveyed to the transfer unit. A transfer material carrier in the form of an endless belt that is rotatable, and a transfer bias is applied from the transfer bias applying means to the transfer member, and the transfer material is carried on the transfer material carrier and conveyed to the transfer unit. In the image forming apparatus for transferring the toner image onto the transfer material, the detecting means for detecting the damage and pinhole of the transfer material carrier, and the damage of the transfer material carrier and the position of the pinhole are detected. Based on the position detection means for performing the detection, and the detection information input from the detection means, it is determined that the transfer material carrier has been damaged or a pinhole has occurred, and the position detection means Based on the position detection information to be force,
If the damage or pinholes on the transfer material carrier are specified and it is judged that the damage or pinholes that have occurred are smaller than a predetermined size, the transfer material carrier is transferred to the damage or pinhole position. It is characterized by having at least a control means for controlling the rotational speed of the transfer material carrier and the application timing of the transfer bias so as not to carry the material.

Further, when it is determined that the damage or the pinhole that has occurred is larger than a predetermined size, the control means controls to stop the operation of the entire image forming apparatus.

Further, when the control means determines that a plurality of the damages or the pinholes have occurred, each of the damages or the pinholes is detected based on the position detection information of each of the damages or the pinholes input from the position detecting means. Calculate the length in the rotation direction of the transfer material carrier between the damages or between the pinholes,
It is characterized in that the size of the transfer material that can be carried on the transfer material carrier is determined according to the calculated length value.

Further, the control means is configured such that the length of the transfer material of the smallest size usable in the image forming apparatus in the rotating direction of the transfer material carrier is such that the transfer material is between the breakages or the pinholes. If it is determined that the transfer material is not longer than the maximum length on which the transfer material can be carried without carrying the transfer material in the rotating direction of the carrier, control is performed to stop the operation of the entire image forming apparatus. Is characterized by.

Further, the detecting means has a differentiating circuit for detecting a current change amount or a voltage change amount per unit time when a predetermined bias is applied to the transfer member from the transfer bias applying means during non-image formation. However, the control means is
It is characterized in that the damage of the transfer material carrier or the occurrence of a pinhole is detected based on a signal input from the differentiating circuit.

The position detecting means has a reference mark formed on the transfer material carrier to indicate a reference position of the transfer material carrier, and a reference mark detecting means for detecting the reference mark, The control means specifies the position where the transfer material carrier is damaged or the pinhole is generated, based on the detection signal of the reference mark input from the reference mark detection means.

Further, a plurality of image carriers on which toner images of different colors are formed are provided, and the image carrier is located on the most downstream side of the rotational direction of the transfer material carrier among the plurality of image carriers. At the transfer portion of the image carrier, the detection unit detects breakage of the transfer material carrier and pinholes.

Further, in the invention described in claim 8, the image carrier on which the toner image is formed is brought into contact with the image carrier at the primary transfer portion, and the toner image formed on the image carrier is formed. A rotatable endless belt-shaped intermediate transfer member to be transferred, a primary transfer member that contacts the intermediate transfer member at the primary transfer portion, and a primary transfer bias that applies a primary transfer bias to the primary transfer member. The toner image transferred onto the intermediate transfer member and the transfer bias applying unit and the intermediate transfer member at the secondary transfer unit is transferred to the secondary transfer unit by applying the secondary transfer bias. In an image forming apparatus including a secondary transfer member that performs secondary transfer at the secondary transfer unit, a detection unit for detecting damage and pinholes in the intermediate transfer member, and damage and damage in the intermediate transfer member. Position detecting means for detecting the position of the pinhole, Based on the detection information input from the detection means, it is determined that the intermediate transfer body is damaged or a pinhole is generated, and the intermediate transfer body is detected based on the position detection information input from the position detection means. Or the position of the pinhole is identified, and when it is determined that the generated damage or the pinhole is smaller than a predetermined size, the toner image is not primarily transferred to the position of the damage or the pinhole of the intermediate transfer member. Thus, at least the control means for controlling the rotation speed of the intermediate transfer member and the application timing of the transfer bias is characterized.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will now be described in detail based on the illustrated embodiments.

<First Embodiment> FIG. 1 is a schematic configuration diagram showing an image forming apparatus according to a first embodiment of the present invention (a full color image forming apparatus such as a full color printer in the present embodiment).

The image forming apparatus 11 is provided with a plurality of image forming portions 24a, 24b, 24c and 24d for forming toner images for each print color by an electrophotographic process. That is, printing color (yellow, magenta, cyan, black)
The photosensitive drums 25 as the four image carriers corresponding to the above are arranged in a line in the vertical direction, and around each photosensitive drum 25, charging for performing image formation by a known electrophotographic process is performed. A device 26, an exposure device 27, a developing device 28, a transfer roller 29, a cleaning device 30, and a static eliminator 31 are provided.

Each image forming section 24a, 24b, 24c, 2
As the 4d exposure device 27, for example, an optical writing device including a laser light source, an optical deflector (rotating polygon mirror, etc.), an imaging optical system, etc. (not shown) can be used, and an image signal corresponding to each printing color can be used. Each of the photosensitive drums 25 charged with the modulated laser light is exposed to form an electrostatic latent image. Further, each developing device 2 of each image forming unit 24a, 24b, 24c, 24d
8 has toners of colors corresponding to respective print colors (yellow, magenta, cyan, black), and develops electrostatic latent images on the photoconductor drums 25 with toners of respective colors to form toner images. Form.

An endless transfer belt 20 as a transfer material carrier is interposed at a transfer portion between each photosensitive drum 25 and each transfer roller 29. The transfer belt 20 is driven by a driving roller 18 and a driven member. The roller 19 and a plurality of rollers are installed and rotated by the drive roller 18 in the direction of the arrow in the figure. By the rotation of the transfer belt 20, the transfer material 12 such as paper fed from the paper feeding unit 13 is electrostatically adsorbed on the surface and is sequentially conveyed to the transfer unit between each photoconductor drum 25 and each transfer roller 29. Is configured to.

Further, in the figure, reference numeral 21 is a charge removing charger (charge removing charger) of the transfer belt 20, and 22 is a transfer belt 20.
Is a separation charger (separation charger) for separating the transfer material 12 from 23, a fixing device 23, and a belt cleaning device 32 having a cleaning belt 33 for cleaning the surface of the transfer belt 20. The transfer belt 2
In addition to this, various cleaning devices such as a blade type and a brush roller type are available as the zero cleaning device.

Next, a full-color image forming operation by the above-described image forming apparatus of this embodiment will be described.

A start signal for starting image formation is input to the image forming apparatus 11, and the transfer material (paper) 12 of a predetermined size at the top stored in the paper feeding unit 13 or the transfer material placed on the manual feed table 14 is transferred. When one of the materials (paper) is separated and fed to the paper passage 15 by the pickup roller 16 and the separation roller 17, the image forming units 24a and 24 are formed.
The image forming operation is started at b, 24c, and 24d.

That is, each photoconductor drum 25 is charged by each charger 26 and each photoconductor drum 25 by each exposure device 27.
And the electrophotographic process of development with toner of each color by each developing device 28, a toner image of each print color (yellow, magenta, cyan, and black) is formed on each photoconductor drum 25.

The image forming portions 24a, 24b, 24 are formed on the transfer material 12 which is electrostatically adsorbed on the transfer belt 20 and conveyed at the timing of forming the toner image.
The toner images are sequentially transferred by the transfer rollers 29 to which the transfer bias having the polarity opposite to that of the toner is applied at the transfer portions c and 24d. At this time, the toner images of yellow, magenta, cyan, and black are sequentially superposed on the transfer material 12, and a full-color toner image is transferred.

The transfer material 12 to which the full-color toner image has been transferred is separated from the transfer belt 20 by the separation charger 22 and conveyed to the fixing device 23, where the full-color toner image is heated in the fixing nip portion of the fixing device 23. After being pressed and fixed on the transfer material 12, the paper is discharged to an external paper discharge unit 35 or a paper discharge tray 36, and a series of image forming operations is completed.

Further, the image forming units 24a, 24b, 24
After each of the above-mentioned transfer in c and 24d, each photosensitive drum 25
The transfer residual toner remaining on the upper surface of each cleaning device 30
The residual toner remaining on the transfer belt 20 is removed by the cleaning belt 33 of the belt cleaning device 32. Further, the surface of each photoconductor drum 25 is neutralized by the static eliminator 31, and the surface of the transfer belt 20 is neutralized by the static eliminator 21 to prepare for the next image formation.

Further, in the image forming apparatus 11 according to the first embodiment of the present invention, even when the transfer belt 20 is damaged or pinholes are generated, the damage or pinhole positions are detected to detect the damage or pinholes. The transfer material 12 can be sucked and conveyed onto the transfer belt 20 while avoiding the positions of the holes.

Hereinafter, the transfer belt 2 according to the present embodiment will be described.
Detection of damage and pinhole at 0, and transfer material 1 on the transfer belt 20 while avoiding this damage and pinhole position.
The control for sucking and transporting 2 will be described.

In this embodiment, as shown in FIGS. 2 and 3, the transfer portion A is attached to the photosensitive drum (fourth photosensitive drum) 25 located on the most downstream side with respect to the moving direction of the transfer belt 20.
In the power pack (transfer bias application power source) 52 of the transfer roller 29 which comes into contact with the transfer belt 20 via the transfer belt 20, a differentiating circuit 52e (see FIG. 4) as a detecting means for detecting damage or pinholes in the transfer belt 20. ) Is provided.

As shown in FIG. 3, during transfer, a voltage is applied to the transfer roller 29 by the power pack 52 for constant voltage control. Here, the constant voltage control is to control the applied voltage to a set constant voltage, which will be described with reference to FIG. FIG. 4 is a diagram showing the internal configuration of the power pack shown in FIG. 3. In this power pack 52, a voltage setting signal from a control device (CPU) 40 for controlling the entire device shown in FIG. 3 is provided. Is entered. This voltage setting signal is often a PWM signal as in this embodiment, and the setting voltage is represented by the ratio of the pulse widths.

For example, the set voltage is 10 kV for a 100% low signal and 5 kV for a 50% low signal.
You can set the voltage such as. The voltage control circuit 52a in the power pack 52 generates a high voltage according to the PWM signal, and the voltage detection circuit 52b monitors and feeds back a high voltage for constant voltage control. Incidentally, 52c is a voltage generating circuit.

When the transfer belt 20 has a pinhole, a larger amount of current flows from the transfer roller 29 to the photosensitive drum 25 than usual. This current is monitored by the current detection circuit 52d. The current detection circuit 52d converts the detected current value (a in FIG. 5A) into a voltage and outputs the voltage to the differentiation circuit 52e. The differentiating circuit 52e differentiates the current value to obtain the amount of change in the current per unit time, and inputs a signal (b in FIG. 5B) corresponding thereto to the control device 40. In the control device 40, a filter is applied to the input signal to set a preset threshold value (c in FIG. 5B).
Only the signal that exceeds (d in FIG. 5 (c)) is extracted.
That is, it indicates that there is a pinhole in the portion where the signal is High in FIG. 5C (d in FIG. 5C).

On the other hand, on a part of the transfer belt 20, as shown in FIG. 6, a home position mark (hereinafter referred to as an HP mark) 63 which is a reference position of the transfer belt 20 is formed by white tape or printing. The home position sensor (not shown) detects the HP mark 63, which is used as a reference for the control timing of the image forming apparatus. In the control device 40, the counter is operating with the timing at which the HP mark 63 is detected as 0,
When the P sensor detects the HP mark 63, it is reset to 0. In this embodiment, the HP sensor 63 is used for the HP mark 63.
By detecting the, the control device 40 can specify the pinhole occurrence position based on the detection signal of the HP mark 63 input from the HP sensor.

Next, the process of actually detecting the pinhole of the transfer belt 20 and controlling the apparatus based on the result will be described in detail.

In the present embodiment, an independent sequence is provided for pinhole detection, and the pinhole detection sequence is executed every time the cumulative number of rotations of the transfer belt 20 reaches 1000, but it is executed. It is desirable that the interval be optimized depending on the configuration of the apparatus, the material of the transfer belt 20, and the like.

When the pinhole detection sequence is executed, the photosensitive drum 2 is subjected to the same operation as the above-mentioned normal image forming operation.
5, the transfer belt 20 is driven to rotate, the photosensitive drum 25
However, at this time, development is not performed and a toner image is not formed on the photosensitive drum 25. Then, as the transfer belt 20 rotates, the HP mark 63 is detected by an HP sensor (not shown), and the counter of the control device 40 operates.

Then, based on the signal detected by the HP sensor (not shown), a bias is applied from the position of the HP mark 63 to the transfer roller 29 from the power pack 52. When a pinhole is detected based on the signal output from the differentiating circuit 52e, the value of the counter is acquired as the position information of the pinhole, and the memory 4
Stored in 1. The above bias is applied to the transfer belt 2
It will take place over two laps of zero.

Then, the position information of the pinhole on the first round is compared with the position information of the pinhole on the second round, and only when the pinhole is detected at substantially the same position, the pinhole is determined and the position is determined. Information is stored in another area of memory 41. If no pinhole is detected,
The sequence ends and no changes are made to the control of the device.

When a pinhole is detected, the position of the transfer material carried on the transfer belt 20 and the application timing of the transfer bias are changed based on the position information stored in the memory 41. The details will be described below.

FIG. 6 shows the pinholes (three pinholes P1, P2, P3 in the figure) detected on the transfer belt 20 as described above. In this case, as shown in the figure, three pinholes P1,
P2 and P3 are present and the distance between all detected pinholes is calculated. Here, P1-P2, P2-P
Three values of 3, P3-P1 are obtained.

The longest distance between the pinholes is Pmax. Pmax is the maximum length of the transfer material which can be carried on the transfer belt 20 without carrying the transfer material on the pinhole.

The transfer belt 2 after the pinhole is detected
Until the 0 is replaced, the transfer material having a length of Pmax or more cannot be selected, and the message "B-Because a failure has occurred in the transfer belt," is displayed on the display panel (not shown) of this image forming apparatus.
Paper longer than 4 sizes cannot be used. It displays that there is a usage restriction such as ". Moreover, you may notify by lighting of LED etc.

Also, the transfer material carried on the transfer belt 20 is controlled so as to be carried while avoiding the pinholes after the pinholes are detected and before the transfer belt 20 is replaced. That is, the control device 40 calculates the carrying position on the transfer belt 20 for each paper size that can be passed, is stored in a predetermined address of the memory 41, and is transferred thereafter until the transfer belt 20 is newly replaced. It is used as a material carrying position. At this time, the image forming speed of the image forming apparatus may decrease due to the change of the transfer material carrying position. In this case, a message such as "The copy speed has decreased due to a failure of the transfer belt" is displayed. Is preferably a display panel (not shown).

If the minimum length of the transfer material that can be passed through the image forming apparatus is Lmin and Lmin> Pmax, pinholes cannot be avoided, and the image forming apparatus is stopped. The display panel (not shown) indicates that the transfer belt 20 needs to be replaced.

As described above, in the present embodiment, when it is detected that one pinhole is generated on the transfer belt 20, the transfer belt 2 is avoided by avoiding the pinhole.
When the transfer material is carried on the surface of 0, and it is detected that a plurality of pinholes are generated, the size of the transfer material that can be used is displayed according to the length between the pinholes, and the transfer material having the predetermined size is displayed. By making it possible to carry the transfer belt 20,
Since a high transfer bias is not applied to the upper pinhole portion, it is possible to prevent damage from occurring on the photosensitive drum 25 side, and it is also possible to replace the transfer belt 20 with the pinhole without changing the image. The forming operation can be continued.

Further, when it is detected that a plurality of pinholes are generated and the transfer material of the smallest size that can pass the paper is longer than the length between the pinholes and the pinholes cannot be avoided, the image forming apparatus is operated. By stopping, it is possible to prevent damage on the photosensitive drum 25 side from occurring.

<Embodiment 2> This embodiment will also be described using the image forming apparatus of Embodiment 1 shown in FIGS. 1 to 4. The configuration of the image forming apparatus and the image forming operation are the same as those in the first embodiment, and the description thereof will be omitted in the present embodiment.

As described above, the breakage of the transfer belt 20 and the pinholes cause damage to the photosensitive drum 25. Especially, when the transfer belt 20 is damaged for some reason and a large breakage occurs, The transfer belt 20 is completely broken on the basis of the breakage. This not only damages the photosensitive drum 25,
The torn transfer belt may remain in the device, which may impair the operation of the device itself.

Therefore, in the present embodiment, when the size of the tear or pinhole generated in the transfer belt 20 in the traveling direction of the transfer belt is detected for some reason, and the tear or pinhole exceeds a predetermined value, Does not change the transfer material carrying position, but controls to stop the apparatus.

In FIG. 7A, a part of the transfer belt 20 is damaged for some reason and a hole having a size large enough to trigger the belt breakage is formed in the first embodiment. The signal (signal a) which converted into the voltage the electric current value detected by the electric current detection circuit 52d in the power pack 52 at the time of performing a pinhole detection sequence is shown.

Also in the present embodiment, as in the first embodiment, the current value is differentiated in the differentiating circuit 52e, the amount of change in the current per unit time is obtained, and a signal corresponding to this is obtained (FIG. 7 (b)). Signals b1 and b2) are input to the control device 40. In the control device 40, a filter is applied to the input signal, and only signals (signals d1 and d2 in FIG. 7C) exceeding a preset threshold value (c in FIG. 7B) are extracted. However, unlike the first embodiment, the filter is also applied to the negative signal.

That is, in FIG. 7C, two High signals (signals d1 and d2) are obtained for one defective portion, but the first High signal (signal d1) is obtained.
The part indicated by is the starting point where excessive current started to flow due to breakage or pinhole, and indicates that there is a breakage or pinhole. Also, the second Hig
The h signal (signal d2) is transmitted from the transfer roller 29 to the transfer belt 2
It shows the timing at which the current suddenly returned to the normal value after passing through the 0 break or the pinhole. That is, the first Hi
gh signal (signal d1) and the second High signal (signal d
The difference (dPx) from 2) represents the length of the pinhole Px.

Next, a detailed description will be given of a process of actually detecting a pinhole and controlling the apparatus based on the result.

In the present embodiment, an independent sequence is provided for detecting pinholes, and the detection sequence is executed every time the cumulative number of rotations of the transfer belt 20 reaches 1000, but the execution intervals are different. It is desirable to be optimized depending on the configuration of the apparatus, the material of the transfer belt 20, and the like. In addition, when a work that may damage the transfer belt 20 is performed, for example, when the transfer belt unit including the transfer belt 20 is attached or detached, the above-described pinhole detection sequence is performed, and then a normal startup operation is performed.

When the pinhole detection sequence is executed, the photosensitive drum 25 and the transfer belt 20 are rotationally driven and the photosensitive drum 25 is charged as in the normal image forming operation. No toner image is formed on the photosensitive drum 25.

As the transfer belt 20 rotates, H
The P mark 63 is detected by an HP sensor (not shown), and the counter of the control device 40 operates. Then, based on the detected signal, a predetermined bias is applied from the power pack 52 to the transfer roller 29 from the position of the HP mark 63.

At this time, when a pinhole is detected by the power pack 52, the position information of the pinhole is:
The value of the counter is acquired and stored in the memory 41. In the case of the present embodiment, two pieces of counter information are acquired for one break or pinhole Px. Pinhole start Pxin and pinhole end Pxou
t. The above bias is applied to the transfer belt 20.
It is held over a week.

Then, the position information of the pinhole on the first round is compared with the position information of the pinhole on the second round, and only when the pinhole is detected at almost the same position, the pinhole is determined and the position is determined. Information is stored in another area of memory 41. If no pinhole is detected,
The sequence ends and no changes are made to the control of the device.

When a pinhole is detected, the above dPx is calculated from Pxin and Pxout of each pinhole (Px), and dPx is about 5 mm on the transfer belt 20.
In the case corresponding to the above, the apparatus is stopped and the transfer belt 2
A message prompting the replacement of 0 is displayed on the display panel (not shown), and the transfer belt 20 is locked so that the image forming operation cannot be performed until the transfer belt 20 is replaced.

When a pinhole is detected and the above-mentioned dPx corresponds to about 5 mm or less on the transfer belt 20, the position of the transfer material carried on the transfer belt 20 and the bias of the transfer material are determined from the position information stored in the memory 41. The application timing is changed. The details are shown below.

FIG. 8 shows the pinholes (three pinholes P1, P2, P3 in the figure) detected on the transfer belt 20 as described above. In this case, as shown in the figure, three pinholes P1,
P2 and P3 are present and the distance between all detected pinholes is calculated. Here, P1out-P2in
(Between P1 and P2), P2out-P3in (P2-P3
3) and P3out-P1in (between P3 and P1).

Of the distances between the pinholes, the longest distance is Pmax. Pmax is the maximum length of the transfer material which can be carried on the transfer belt 20 without carrying the transfer material on the pinhole.

Transfer belt 2 after the pinhole is detected
Until the 0 is replaced, the transfer material having a length of Pmax or more cannot be selected, and the message "B-Because a failure has occurred in the transfer belt," is displayed on the display panel (not shown) of this image forming apparatus.
Paper longer than 4 sizes cannot be used. It displays that there is a usage restriction such as ". Moreover, you may notify by lighting of LED etc.

Further, the transfer material carried on the transfer belt 20 is controlled so as to avoid the pinholes and be carried during the period from the detection of the pinholes to the replacement of the transfer belt 20. That is, the control device 40 calculates the carrying position on the transfer belt 20 for each paper size that can be passed, is stored in a predetermined address of the memory 41, and is transferred thereafter until the transfer belt 20 is newly replaced. It is used as a material carrying position. At this time, the image forming speed of the image forming apparatus may decrease due to the change of the transfer material carrying position. In this case, a message such as "The copy speed has decreased due to a failure of the transfer belt" is displayed. Is preferably a display panel (not shown).

When the minimum length of the transfer material that can be passed through the image forming apparatus is Lmin, and when Lmin> Pmax, pinholes cannot be avoided, so the image forming apparatus is stopped. A message that the transfer belt 20 needs to be replaced is displayed on a display panel (not shown).

As described above, in this embodiment, in addition to the effect obtained in the first embodiment, when it is determined that the damage or the pinhole generated on the transfer belt 20 is larger than the predetermined value, the image forming apparatus is stopped. By doing so, it is possible to prevent damage to the photosensitive drum 25 side from occurring.

<Third Embodiment> In the first and second embodiments,
A transfer material (paper or the like) carried on a transfer belt as a transfer material carrier is conveyed to a transfer section of each image forming section, and toners of different colors are sequentially superposed to form an image forming apparatus for forming a full-color image. Although the invention has been applied to the example, in the present embodiment, the invention is applied to an image forming apparatus provided with an intermediate transfer belt as an intermediate transfer member.

FIG. 9 is a schematic block diagram showing an image forming apparatus according to the present embodiment (a full color image forming apparatus such as a full color printer having an intermediate transfer belt in the present embodiment). The first embodiment shown in FIGS.
Members having the same functions as those of the image forming apparatus of 1 are given the same reference numerals, and overlapping description will be omitted.

The image forming apparatus includes an image forming portion Pa for forming a yellow toner image, an image forming portion Pb for forming a magenta toner image, and an image forming portion Pc for forming a cyan toner image. , Four image forming portions (image forming units) of an image forming portion Pd that forms a black toner image, and these four image forming portions Pa and P are provided.
b, Pc, and Pd are arranged in a line with a constant interval.

Around the photosensitive drum 25, a charging roller 26, an exposure device 27, a developing device 28, a transfer roller 29, for forming an image by a known electrophotographic process,
A cleaning device (not shown) is provided.

An endless intermediate transfer belt 50 as an intermediate transfer member is interposed in a transfer portion (primary transfer portion) between each photosensitive drum 25 and each transfer roller 29. Reference numeral 50 is installed on a plurality of rollers and is rotated in the direction of the arrow in the figure. The intermediate transfer belt 50 is made of a dielectric resin sheet such as a polyethylene terephthalate (PET) resin sheet, a polyvinylidene fluoride resin sheet, a polyurethane resin sheet, or a polyimide resin sheet, and both ends thereof are superposed and joined to each other. , Endless or seamless (seamless) belts are used.

The intermediate transfer belt 50 is in contact with the secondary transfer roller 61 at the secondary transfer portion. The secondary transfer roller 61 is installed so that it can come into contact with and separate from the intermediate transfer belt 50.

Next, the full-color image forming operation by the above-described image forming apparatus of the present embodiment will be described.

A start signal for starting image formation is input,
When the uppermost transfer material (paper) 12 of a predetermined size stored in the paper feeding unit 13 is separated and fed to the paper passage, the image forming operation is performed in each of the image forming units Pa, Pb, Pc, and Pd. Be started.

That is, each photoconductor drum 25 is charged by each charging roller 26, each photoconductor drum 25 is exposed by each exposure device 27, and each developing device 28 develops each color toner by each electrophotographic process. Toner images of respective print colors (yellow, magenta, cyan, and black) are formed on the photoconductor drum 25, respectively.

First, the yellow toner image formed on the photosensitive drum 25 of the image forming portion Pa is transferred to the primary transfer bias (toner and toner) at the primary transfer portion between the photosensitive drum 25 and the transfer roller 29. The intermediate transfer belt 5 moving (rotating) by the transfer roller 29 to which the reverse polarity is applied.
0 is primary-transferred. In the present embodiment, the primary transfer bias applied to the transfer roller 29 is controlled to a constant current, and each transfer roller 29 has +10.0.
A primary transfer bias of μA is applied.

The intermediate transfer belt 50 on which the yellow toner image has been transferred is moved (rotated) to the image forming portion Pb side.
Also in the image forming portion Pb, the magenta toner image formed on the photoconductor drum 25 in the same manner as described above is
The yellow toner image on the intermediate transfer belt 50 is superposed and transferred.

In the same manner, the cyan and black toner images formed by the image forming portions Pc and Pd are superimposed on the intermediate transfer belt 50 and transferred onto the yellow and magenta toner images, respectively. In order to form a full-color toner image on the intermediate transfer belt 50 by sequentially superposing.

Then, the full-color toner image on the intermediate transfer belt 50 is fed from the paper feed portion 13 at the timing when the front end of the full-color toner image is moved to the secondary transfer portion formed between the intermediate transfer belt 50 and the secondary transfer roller 61. The transfer material (paper) 12 is conveyed to this secondary transfer portion. At this time, a secondary transfer bias (having a polarity opposite to that of the toner) is applied to the secondary transfer roller 61 that is in contact with the intermediate transfer belt 50, so that the transfer material (paper) 1
A full-color toner image is secondarily transferred onto the sheet 2 at once.

The transfer material 12 on which the full-color toner image has been transferred is conveyed to the fixing device 23, and the full-color toner image is heated and pressed at the fixing nip portion of the fixing device 23 to be fixed on the transfer material 12. Then, the paper is discharged to the external paper discharge tray 36, and a series of image forming operations is completed.

Further, the image forming portions Pa, Pb, Pc, Pd
The transfer residual toner remaining on each photoconductor drum 25 after each of the above-mentioned primary transfer in FIG.
The residual toner remaining on the intermediate transfer belt 50 is removed by the belt cleaning device 62.

In the image forming apparatus according to the third embodiment of the present invention, even when the intermediate transfer belt 50 is damaged or pinholes are generated, the damage or pinhole position is detected to detect the damage or pinholes. A toner image can be formed on the intermediate transfer belt 50 so as to avoid the positions of the holes.

That is, also in the present embodiment, as in the first embodiment shown in FIGS. 1 to 4, a transfer bias (primary transfer bias) is applied to the transfer roller 29 of the image forming portion Pd on the most downstream side. Based on the signal output from the applied power pack, the control device can detect the occurrence of damage or pinholes on the intermediate transfer belt 50. Further, the detected breakage of the intermediate transfer belt 50 and the position of the pinhole can be detected based on the position detection of the HP mark formed on the intermediate transfer belt 50 by the HP sensor as in the first embodiment. These detection operations are as described in detail in the first or second embodiment, and the description thereof will be omitted in the present embodiment.

As described above, also in this embodiment, when it is detected that one pinhole is formed on the intermediate transfer belt 50, the toner image is formed on the intermediate transfer belt 50 by avoiding the pinhole. After the transfer (primary transfer), the image forming operation can be continued without replacing the intermediate transfer belt 50 in which the pinhole is generated.
When it is detected that multiple pinholes occur, the toner image is transferred according to the length between the pinholes (primary transfer).
If it is determined that the toner image cannot be transferred (primary transfer), the primary transfer bias is not applied to the pinhole portion on the intermediate transfer belt 50, so that the photosensitive drum 25 side is damaged. It can be prevented from occurring.

Further, in the present embodiment, when it is determined that the damage or pinhole generated on the intermediate transfer belt 50 is larger than a predetermined value, the image forming apparatus is stopped in the same manner as in the second embodiment. It is possible to prevent damage from occurring on the photosensitive drum 25 side.

Further, in the present embodiment, the structure in which the damage or the pinhole of the intermediate transfer belt 50 is detected in the primary transfer portion where the above-mentioned transfer roller 29 is located, the secondary transfer roller 61 described above is used. The same effect can be obtained even in the configuration in which the damage or the pinhole of the intermediate transfer belt 50 is detected in the secondary transfer portion located.

[0093]

As described above, according to the first aspect of the invention, it is determined whether the transfer material carrier is damaged or pinholes are generated based on the detection information input from the detection means. When the position of the damage or pinhole of the transfer material carrier is specified based on the position detection information input from the position detection means, and it is determined that the generated damage or pinhole is smaller than a predetermined size, By controlling at least the rotational speed of the transfer material carrier and the application timing of the transfer bias so that the transfer material carrier is not damaged or the transfer material is not carried at the pinhole position, the damaged part or the pin of the transfer material carrier is controlled. Since it is possible to prevent transfer bias from being applied to the hole portion, it is possible to prevent damage to the image carrier side, and to prevent damage or pinholes. The image forming operation can be continued without replacing the the transfer material carrying member.

According to the invention described in claim 8, it is judged based on the detection information inputted from the detecting means that the intermediate transfer member is damaged or a pinhole is generated, and the position detecting means inputs the information. If the damage or pinhole that occurred is determined to be smaller than the specified size by specifying the position of the damage or pinhole on the intermediate transfer member based on the position detection information, the damage or pinhole on the intermediate transfer member is detected. The primary transfer bias is applied to the damaged portion or the pinhole portion of the intermediate transfer body by controlling at least the rotation speed of the intermediate transfer body and the application timing of the primary transfer bias so that the toner image is not transferred to the position It is possible to prevent the occurrence of damage on the image carrier side, and to prevent damage or pinholes in the intermediate transfer member. It can be continued image forming operation without replacement.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing the vicinity of a transfer portion of the image forming apparatus according to the first embodiment of the present invention.

FIG. 3 is an enlarged schematic view showing the vicinity of a transfer portion on the most downstream side of FIG.

FIG. 4 is a diagram showing a configuration of a power pack that applies a transfer bias to the transfer roller of the image forming apparatus according to the first embodiment of the present invention.

5 (a), (b), and (c) are diagrams showing signal waveforms generated in a power pack at the time of detecting a pinhole according to the first embodiment of the present invention.

FIG. 6 is a diagram showing positions of pinholes formed on the transfer belt of the image forming apparatus according to the first embodiment of the present invention.

7 (a), (b) and (c) are diagrams showing signal waveforms generated in a power pack at the time of detecting a pinhole according to the second embodiment of the present invention.

FIG. 8 is a diagram showing positions of pinholes formed on the transfer belt of the image forming apparatus according to the second embodiment of the present invention.

FIG. 9 is a schematic configuration diagram showing an image forming apparatus according to a third embodiment of the present invention.

[Explanation of symbols]

11 Image forming apparatus 12 Transfer material 13 Paper feeder 20 Transfer belt (transfer material carrier) 23 Fixer 24a, 24b, 24c, 24d Image forming unit 25 Photosensitive drum (image bearing member) 26 Charger 27 Exposure equipment 28 Developer 29 Transfer roller (transfer member) 40 Control device (control means) 41 memory 50 Intermediate transfer belt (intermediate transfer member) 61 Secondary transfer roller 52 Power Pack 52a voltage control circuit 52b Voltage detection circuit 52c voltage generation circuit 52d current detection circuit 52e Differentiation circuit (detection means)

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03G 21/00 500 G03G 21/00 500 F term (reference) 2H027 DA21 DA23 DA32 DA39 DB09 DC10 DE04 DE07 DE09 EC06 EC08 EC10 EC18 EC20 ED06 ED17 ED24 EE01 EE07 EE08 EF06 EK01 EK03 HA02 HA04 HA12 ZA07 2H030 AB02 AD05 AD08 AD17 BB02 BB16 BB42 BB56 2H200 FA11 FA12 GA02 GA10 GA12 JA23 J02 HBJAB JAB HB HAB HAB HAB HAB HAB HAB HAB HAB HAB HAB HAB HAB HAB JB49 JB50 JC03 JC09 JC18 JC19 JC20 NA02 NA08 NA18 PA10 PA19 PA22 PA26 PA28 PB05 PB08 PB11 PB12 PB15 PB26 PB38

Claims (14)

[Claims] 1. An image carrier on which a toner image is formed, a transfer member contacting the image carrier at a transfer portion, a transfer bias applying unit for applying a transfer bias to the transfer member, and the image carrier. The transfer bias is provided between the transfer members so as to pass through the transfer portion, and the rotatable transfer material carrier, which is a rotatable endless belt, holds the transfer material on its surface and conveys it to the transfer portion. In the image forming apparatus, which applies a transfer bias to the transfer member from an application unit to transfer the toner image onto the transfer material carried on the transfer material carrier and conveyed to the transfer unit, Detecting means for detecting the damage and pinhole of the carrier, position detecting means for detecting the damage of the transfer material carrier and the position of the pinhole, based on the detection information input from the detecting means ,Previous The transfer material carrier is determined to be damaged or pinholes are generated, and the damage or pinhole position of the transfer material carrier is specified based on the position detection information input from the position detection means. When it is determined that the generated damage or pinhole is smaller than a predetermined size, the transfer material carrier is rotated at least so as not to carry the transfer material at the position of the damage or pinhole of the transfer material carrier. An image forming apparatus comprising: a control unit that controls a speed and an application timing of the transfer bias. 2. The control means controls to stop the operation of the entire image forming apparatus when it is determined that the damage or the pinhole is larger than a predetermined size. The image forming apparatus according to item 1. 3. The control means, when judging that the generated damage or a plurality of pinholes have occurred, the control means determines each of the damages or the pinholes based on position detection information of each of the damages or pinholes input from the position detection means. The length in the rotation direction of the transfer material carrier is calculated between the breakages or between the pinholes, and the size of the transfer material that can be carried on the transfer material carrier is determined according to the calculated length value. The image forming apparatus according to claim 1, wherein the image forming apparatus determines. 4. The transfer means is configured such that the length of the transfer material carrier of the smallest size usable in an image forming apparatus in the rotation direction of the transfer material carrier is between the damages or between the pinholes. When it is determined that the transfer material is larger than the maximum length on which the transfer material can be carried without carrying the transfer material in the rotating direction of the carrier, control is performed to stop the operation of the entire image forming apparatus. The image forming apparatus according to claim 3, wherein: 5. The detection means has a differentiation circuit for detecting a current change amount or a voltage change amount per unit time when a predetermined bias is applied to the transfer member from the transfer bias applying means during non-image formation. The image forming apparatus according to claim 1, wherein the control unit detects damage to the transfer material carrier or occurrence of a pinhole based on a signal input from the differentiating circuit. 6. The position detection means includes a reference mark formed on the transfer material carrier to indicate a reference position of the transfer material carrier, and a reference mark detection means for detecting the reference mark. The control unit identifies a position where the transfer material carrier is damaged or a pinhole is generated, based on a detection signal of the reference mark input from the reference mark detection unit. Image forming device. 7. A plurality of image carriers on which toner images of different colors are respectively formed are provided, and the image carrier is located on the most downstream side of the rotational direction of the transfer material carrier among the plurality of image carriers. The image forming apparatus according to claim 1, wherein the detection unit detects breakage of the transfer material carrier and pinholes at the transfer unit of the image carrier. 8. A rotatable endless belt, which is in contact with an image carrier on which a toner image is formed, at the primary transfer portion, and onto which the toner image formed on the image carrier is transferred. -Shaped intermediate transfer member, a primary transfer member that comes into contact with the intermediate transfer member at the primary transfer portion, a primary transfer bias applying unit that applies a primary transfer bias to the primary transfer member, and the intermediate transfer member. The toner image transferred onto the intermediate transfer body is brought into contact with the body at the secondary transfer portion, and the toner image transferred to the intermediate transfer body by applying the secondary transfer bias.
An image forming apparatus comprising: a secondary transfer member that performs secondary transfer at the secondary transfer unit onto a transfer material conveyed to a next transfer unit; detection for detecting breakage and pinholes of the intermediate transfer member. Means, position detection means for detecting the damage of the intermediate transfer member and the position of the pinhole, and that damage or a pinhole has occurred in the intermediate transfer member based on the detection information input from the detection means. And determine the position of the damage or pinhole on the intermediate transfer member based on the position detection information input from the position detection means, and determine that the generated damage or pinhole is smaller than a predetermined size. In this case, at least the rotational speed of the intermediate transfer member and the transfer bias application voltage are applied so that the toner image is not primarily transferred to the position of the pinhole or the damage of the intermediate transfer member. A control means for controlling the timing, the image forming apparatus characterized by. 9. The control unit controls to stop the operation of the entire image forming apparatus when it is determined that the damage or the pinhole is larger than a predetermined size. The image forming apparatus according to item 1. 10. When the control means determines that a plurality of the damages or the pinholes have occurred, the control means determines the damages or the pinholes based on the position detection information of the damages or the pinholes. The length in the rotation direction of the intermediate transfer member between the breakages or between the pinholes is calculated, and the size of the transfer material that can be conveyed to the secondary transfer unit is determined according to the calculated length value. The image forming apparatus according to claim 8, wherein. 11. The control unit is configured such that a length of a transfer material having a minimum size usable in an image forming apparatus in a conveyance direction is a maximum in a rotation direction of the intermediate transfer body between the breakages or the pinholes. The image forming apparatus according to claim 10, wherein when it is determined that the length is larger than the length, the operation of the entire image forming apparatus is controlled to be stopped. 12. The detecting means detects an amount of current change or voltage change per unit time when a predetermined bias is applied from the primary transfer bias applying means to the primary transfer member during non-image formation. 9. The image forming apparatus according to claim 8, further comprising a differentiating circuit, wherein the control unit detects damage to the intermediate transfer member or occurrence of a pinhole based on a signal input from the differentiating circuit. apparatus. 13. The position detecting means includes a reference mark formed on the intermediate transfer body to indicate a reference position of the intermediate transfer body, and a reference mark detecting means for detecting the reference mark. 9. The image forming apparatus according to claim 8, wherein the unit specifies a position where the intermediate transfer member is damaged or a pinhole is generated, based on a detection signal of the reference mark input from the reference mark detecting unit. apparatus. 14. A plurality of image bearing members on which toner images of different colors are respectively formed are provided, and the image bearing member is located on the most downstream side with respect to the rotation direction of the intermediate transfer member of the plurality of image bearing members. 9. The image forming apparatus according to claim 8, wherein the primary transfer portion of the image carrier detects the damage of the intermediate transfer member and the pinhole by the detection unit.