JP4821782B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, and a composite machine including a brush cleaning device that removes toner remaining on a transfer belt after transfer using a brush.

  In this type of image forming apparatus, a brush cleaning device is provided in order to remove the toner remaining on the transfer belt after the toner image carried on the transfer belt is transferred to a sheet. In this brush cleaning device, as the toner is used, toner accumulates on the brush, and the cleaning performance deteriorates. Therefore, the conventional image forming apparatus has a recovery sequence in which the toner accumulated on the brush is once discharged onto the transfer belt and cleaned again.

  Since the amount of toner deposited on the brush varies depending on the usage situation (coverage, environment, usage frequency, etc.) of the user, it is desirable to execute the recovery sequence according to the state of toner deposition on the brush. However, in reality, since the toner accumulation state on the brush cannot be known, the recovery sequence is frequently executed.

  For this reason, the recovery sequence is executed in a state where the toner is not deposited so much on the brush, and the brush cleaning device and the transfer belt are operated wastefully. As a result, the waiting time until the start of the printing operation is increased, which is inconvenient for the user, the life of the brush cleaning device is shortened, and there is a problem that the replacement time is early.

  Further, since the life of the brush cleaning device is determined by the driving time of the device, there is a problem that the brush cleaning device is used even if it has already reached the end of its life or is replaced even if it is still usable.

Patent Document 1 describes an image forming apparatus that detects the contact / separation state of a cleaner with respect to a transfer belt by rotating the transfer belt with a toner patch formed on the transfer belt and detecting the presence or absence of the toner patch after a predetermined time. However, this is for confirming whether or not the cleaner is operating and for surely executing the image forming sequence, not for executing the recovery sequence.
JP 2006-337798 A

  This invention makes it a subject to perform the cleaning performance recovery sequence timely according to the state of the brush of a brush cleaning apparatus, and to reduce the operating frequency. Another object is to accurately determine the life of the brush cleaning device.

In order to solve the above problem, the first means is:
A transfer member to which a toner image is transferred;
A brush cleaning device that removes toner remaining on the transfer member by applying a cleaning current;
A toner sensor for detecting toner on the transfer member after passing through a brush cleaning device,
The inspection pattern is transferred onto the transfer member at a predetermined timing, and the current value of the cleaning current of the brush cleaning device is lowered than normal, and the transfer after the inspection pattern passes the brush cleaning device by the toner sensor. When the toner on the member is detected and the toner sensor detects a toner adhesion amount that exceeds a reference, the cleaning current is changed to discharge toner deposited on the brush of the brush cleaning device onto the transfer member, The cleaning current recovery control is performed to restore the cleaning current and remove the toner discharged on the transfer member.
The second means is
A transfer member to which a toner image is transferred;
A brush cleaning device that removes toner remaining on the transfer member by applying a cleaning current;
A toner sensor for detecting toner on the transfer member after passing through a brush cleaning device;
A secondary transfer member that transfers the toner image on the transfer member to an adjacent member;
The inspection pattern is transferred onto the transfer member at a predetermined timing, and a secondary transfer voltage is applied to the secondary transfer member to neutralize or reversely charge the toner charge amount of the inspection pattern, and the toner sensor performs the inspection. Toner deposited on the brush of the brush cleaning device by changing the cleaning current when the pattern detects toner on the transfer member after passing through the brush cleaning device and the toner sensor detects an amount of toner adhering above a reference. After the toner is discharged onto the transfer member, cleaning performance recovery control is performed to restore the cleaning current and remove the toner discharged onto the transfer member.

  In the first means, when the toner sensor detects a toner adhesion amount exceeding the reference, it means that the cleaning performance of the brush cleaning device is deteriorated. That is, it is possible to self-diagnose the state of the brush that the brush of the brush cleaning device has passed the toner without completely removing the toner on the transfer member due to toner accumulation. Therefore, by performing the cleaning performance recovery control at this time, the toner accumulated on the brush is discharged onto the transfer member, and the cleaning performance can be recovered.

According to a third aspect , in the first and second means, if the toner sensor detects a toner adhesion amount exceeding a reference even if the cleaning performance recovery control is executed once or more times, the brush The life of the cleaning device was determined.

  According to the invention of the first means, it is possible to self-diagnose the deterioration of the cleaning performance of the brush, and the cleaning performance recovery sequence can be executed in a timely manner according to the state of the brush. The operating frequency can be reduced. For this reason, the brush cleaning device and the transfer member are not driven wastefully, the waiting time until the start of the printing operation can be shortened, and the life of the brush cleaning device is improved.

Further , the cleaning performance can be accurately inspected by using the inspection pattern.

Furthermore, by setting the cleaning current of the brush cleaning device to a value different from the normal cleaning current, the cleaning load increases and the deterioration of the cleaning performance can be inspected more remarkably.

According to the invention of the second means , in addition to the effect of the invention of the first means, the toner charge amount of the test pattern is neutralized or reversely charged by the secondary transfer member, thereby increasing the cleaning load and the cleaning performance. It is possible to more significantly inspect the decrease in.

According to the third aspect of the invention, even if the cleaning performance recovery control is executed, if the toner sensor detects a toner adhesion amount equal to or higher than the reference, it can be seen that the cleaning performance is not recovered. It is possible to accurately determine the life, and it is possible to eliminate waste such as continued use even when the life has expired or replacement of a usable one.

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

  FIG. 1 schematically shows an image forming apparatus 1 according to the present invention. Four imaging units 2Y, 2M, 2C, and 2K that respectively form four color images of yellow, magenta, cyan, and black are arranged along the intermediate transfer belt 3.

  Each of the imaging units 2Y, 2M, 2C, and 2K includes a photosensitive member 4, a charger 5, an exposure unit 6, a developing unit 7, a primary transfer roller 8, and a cleaner 9 arranged in this order around the photosensitive member 4. ing.

  The intermediate transfer belt 3 is stretched around a driving roller 10 and a driven roller 11, and can move in the direction of the arrow by the rotation of the driving roller 11. Inside the intermediate transfer belt 3, the primary transfer rollers 8 of the imaging units 2Y, 2M, 2C, 2K are arranged. The primary transfer roller 8 faces the photoconductor 4 through the intermediate transfer belt 3 and can contact and separate. On the downstream side of the black imaging unit 2 </ b> K located on the most downstream side with respect to the moving direction of the intermediate transfer belt 3, a toner sensor 12 made up of an optical sensor is disposed to face the intermediate transfer belt 3. On the side of the driving roller 10 of the intermediate transfer belt 3, a secondary transfer roller 13 that faces the driving roller 10 via the intermediate transfer belt 3 is disposed so as to be able to contact and separate. A sheet S is supplied between them. On the side of the driven roller 11 of the intermediate transfer belt 3, a brush cleaning device 14 that faces the driven roller 11 through the intermediate transfer belt 3 is disposed.

  FIG. 2 schematically shows the brush cleaning device 14. In the casing 15 of the brush cleaning device 14, a pre-charging brush 16 that faces and contacts the intermediate transfer belt 3, and faces the intermediate transfer belt 3 downstream of the pre-charging brush 16 in the moving direction of the intermediate transfer belt 3. The cleaning brush 17 that contacts the cleaning brush 17, the collection roller 18 that contacts the cleaning brush 17, and the waste toner conveying screw 19 are accommodated.

  The pre-charging brush 16 is obtained by weaving conductive fibers having a length of 2 to 5 mm in a conductive base fabric, and extends in the axial direction of the driven roller 11 of the intermediate transfer belt 3. The width of the pre-charging brush 16 along the moving direction of the intermediate transfer belt 3 is 3 to 10 mm. The pre-charging brush 16 is grounded.

  As with the pre-charging brush 16, the cleaning brush 17 is made by weaving conductive fibers having a length of 2 to 5 mm on a conductive base fabric, and is wound around an axis to transfer the intermediate transfer belt. The three driven rollers 11 extend in the axial direction. The outer diameter of the cleaning brush 17 is 15 to 30 mm. The cleaning brush 17 is rotationally driven in the same direction as the driven roller 11 of the intermediate transfer belt 3, and moves in a direction opposite to the moving direction of the intermediate transfer belt 3 at the contact portion with the intermediate transfer belt 3.

The conductive fibers of the pre-charging brush 16 and the cleaning brush 17 are obtained by dispersing conductive particles such as carbon in a resin such as nylon, polyester, and acrylic. As the raw yarn of the conductive fiber, one having a diameter of 1 to 10 D (denier), a density of 50 to 450 kF / in ² , and a resistance of 1 × 10 ³ Ω or more can be used.

  The collection roller 18 is made of a conductive member, is driven to rotate in the direction opposite to the cleaning brush 17, and moves in the same direction as the cleaning brush 17 at the contact portion with the cleaning brush 17. A scraper 20 is disposed downstream of the collection roller 18 in the rotation direction. A cleaning voltage is applied to the collection roller 18 from the high-voltage power supply circuit 21, and a cleaning current flows from the collection roller 18 to the pre-charging brush 16 via the cleaning brush 17 and the intermediate transfer belt 3. The high-voltage power supply circuit 21 can switch the cleaning current for the collection roller 18 to the normal 20 μA, the cleaning performance inspection 5 μA, and the cleaning performance recovery ground by the control device 22.

  The waste toner conveying screw 19 discharges the waste toner stored in the casing 15 to the outside of the apparatus.

  A schematic operation of the image forming apparatus 1 having the above-described configuration will be described. In each of the imaging units 2Y, 2M, 2C, 2K, the surface of the photoconductor 4 is charged to a predetermined potential by the charger 5, and is exposed by the exposure hot water unit 6 to form an electrostatic latent image corresponding to the image signal. The electrostatic latent image is developed by the developing device 7 and becomes a toner image of each color. The toner images on the photoreceptors 4 of the imaging units 2Y, 2M, 2C, and 2K are transferred onto the intermediate transfer belt 3 by the primary transfer roller 8. The toner image on the intermediate transfer belt 3 is batch-transferred onto a sheet S supplied from a sheet feeding device (not shown) by the secondary transfer roller 13 in a region facing the secondary transfer roller 13 to become a full color image. The paper S on which the full color image is formed is discharged through a fixing device (not shown). On the other hand, the toner remaining on the intermediate transfer belt 3 after the secondary transfer is removed by the brush cleaning device 14.

  In the brush cleaning device 14, a cleaning current flows from the high-voltage power supply circuit 21 to the precharge brush 16 through the recovery roller 18, the cleaning brush 17, and the intermediate transfer belt 3. The residual toner (charge amount 0 to −10 μC / g) on the intermediate transfer belt 3 is charged to a charge amount of −10 to −40 μC / g when passing through the pre-charging brush 16. When the negatively charged residual toner passes through the cleaning brush 17, it is electrostatically attracted to the positive cleaning brush 17 by the electric field between the cleaning brush 17 and the intermediate transfer belt 3, and the intermediate transfer belt 3. Removed from. The toner adsorbed by the cleaning brush 17 is further electrostatically adsorbed by the collecting roller 18, then scraped off from the surface of the collecting roller 18 by the scraper 20, and freely falls to the lower part of the casing 15. The toner dropped on the casing 15 is discharged to a waste toner box or the like outside the apparatus by a waste toner conveying screw 19.

Before describing the cleaning performance inspection sequence, the relationship between the toner sensor 12 and the cleaning load will be described. FIG. 3 shows the relationship between the toner adhesion amount on the intermediate transfer belt 3 and the output of the toner sensor 12. From FIG. 3, when the toner adhesion amount is 0.5 g / m ² or less, the ratio of the change in the sensor output with respect to the change in the toner adhesion amount decreases, and the reading sensitivity of the toner sensor 12 deteriorates. It can be said that it is necessary to increase the cleaning load so that a certain toner adhesion amount is in the range of 0.5 to ² g / m ² .

FIG. 4 shows the amount of toner that has passed through the cleaning brush 17 when cleaning is performed by changing the secondary transfer voltage applied to the secondary transfer roller 13. When a secondary transfer voltage is applied to the secondary transfer roller 13, the toner on the intermediate transfer belt 3 is neutralized or reversely charged, and the cleaning load increases.
A (◇) in the figure is the case where a clean cleaning brush 17 is used, and since the cleaning performance is high, the toner adhesion amount after passing through the cleaning brush 17 is small.
B (□) in the figure is a case where the cleaning brush 17 in which toner is accumulated due to durability is used, and the cleaning current is lowered to 5 μA or lower than that during normal cleaning (20 μA), and the secondary transfer voltage is not applied. Since the toner adhesion amount exceeds 1 g / m ² by reducing the cleaning current, the toner sensor 12 can accurately detect the toner adhesion amount.
In the figure, C (Δ) shows the case where the cleaning brush 17 on which toner is accumulated due to durability is used and the cleaning current is set to 20 μA, which is the same as that in normal cleaning. but ² or less, the secondary transfer voltage is 1000V or higher because the toner adhering amount exceeds 1 g / ^{m 2,} can be detected accurately by the toner sensor 12.

  Therefore, in the cleaning performance inspection sequence, as a method for detecting the toner adhesion amount that has passed through the cleaning brush 17 with high sensitivity, the cleaning current of the brush cleaning device 14 is decreased from the normal time to perform cleaning spontaneously. A method of apparently increasing the cleaning load by degrading performance, and increasing the cleaning load by applying a secondary transfer voltage of about 1000 V to the secondary transfer roller 13 to neutralize or reversely charge the toner on the intermediate transfer belt 3. There is a way to do it.

<Cleaning performance inspection sequence>
Next, the cleaning performance inspection sequence will be described in detail.

  FIG. 5 shows a cleaning performance inspection sequence according to a method of increasing the cleaning load by reducing the cleaning current from the normal time. In step S11, an inspection pattern for inspecting the cleaning performance of the brush cleaning device 14 is formed on the photoreceptors 4 of the imaging units 2Y, 2M, 2C, and 2K at a predetermined timing, for example, every 100 image formation sheets. To do.

As shown in FIG. 6, the inspection pattern is formed by continuously forming Y and M toner belt-like patterns P _Y and P _M at positions that can be detected by the first toner sensor 12a on the intermediate transfer belt 3. The belt-like patterns P _C and P _K of C and K toners may be continuously formed at positions that can be detected by the second toner sensor 12b. In order to further increase the cleaning load, a solid band pattern (four-layer toner) in which Y, M, C, and K toners are overlaid on the intermediate transfer belt 3 may be used, or Y and M, C and K may be used. A solid belt-like pattern (two-layer toner) in which the toner is color-superposed on the intermediate transfer belt 3 may be used. The more toner layers in the detection pattern P, the greater the amount of toner that passes through the cleaning brush 17 per unit time, the cleaning load can be increased, and the toner adhesion amount can be easily detected. Note that since there is a toner adhesion amount detection pattern in image stabilization control as a pattern similar to the inspection pattern P, it can also be used as it.

  Returning to FIG. 5, after the inspection pattern is formed, the inspection pattern is primarily transferred onto the intermediate transfer belt 3 in step S <b> 12, and the primary transfer roller 8 is separated from the intermediate transfer roller 3 in step S <b> 13. In step 14, the current value of the cleaning current from the high-voltage power supply circuit 21 is set to a value (for example, 5 μA) lower than the current value for normal cleaning (for example, 20 μA). The reason why the current value is made lower than that in the normal cleaning is to notice the deterioration of the cleaning performance more remarkably, and as described above, to detect the toner adhesion amount within the range in which the toner sensor 12 has good reading sensitivity. It is.

  In this state, the inspection pattern on the intermediate transfer belt 3 is moved to the brush cleaning device 14 via the secondary transfer roller 13. In step S15, the inspection pattern on the intermediate transfer belt 3 is cleaned by the brush cleaning device 14.

  Here, as shown in FIG. 6B, a part of the toner of the inspection pattern is removed by the cleaning brush 17, but the rest passes through the cleaning brush 17. The amount of toner that passes through the cleaning brush 17 (the toner that remains after wiping) varies depending on the cleaning performance of the cleaning brush 17. If the cleaning performance of the cleaning brush 17 is not lowered, the toner adhesion amount after passing through the cleaning brush 17 is small. However, if the cleaning performance is degraded, the toner adhesion amount after passing through the cleaning brush 17 is increased.

  FIG. 7 shows a cleaning performance inspection sequence by a method of increasing the cleaning load by applying the secondary transfer voltage. In step S13-1, only the primary transfer roller 8 is separated, in step S13-2, the secondary transfer roller 13 is pressed and 1000V is applied, and in S14-1, the current value of the cleaning current is the current during normal cleaning. Except for the value (for example, 20 μA), it is the same as the cleaning performance inspection sequence in FIG.

<Cleaning performance judgment flow>
FIG. 8 shows a cleaning performance determination flow after the cleaning performance inspection sequence of FIG. 5 or FIG.

  After executing the above-described cleaning performance inspection sequence in step S21, the toner adhesion amount of the toner remaining on the intermediate transfer belt 3 is read by the toner sensor 12 in step S22. As the toner sensor 12, an optical sensor dedicated to this sequence may be used, but by using an IDC (Image Density Control) sensor for image stabilization control that is generally used in a full-color image forming apparatus, The present invention can be implemented without increasing costs.

In step S23, it is determined whether or not the toner adhesion amount is a predetermined value (for example, 1 g / m ² ) or less. If the toner adhesion amount is equal to or less than the predetermined value, it is determined that the toner adhesion amount is normal and the cleaning performance is good, the adhesion amount abnormality detection number N is reset to zero in step S24, and the next image formation is performed in step S25. to approve.

  If the toner adhesion amount is equal to or greater than a predetermined value, it is determined that the toner adhesion amount is abnormal and the cleaning performance is deteriorated, and the adhesion amount abnormality detection count N is incremented in step S26. Then, in step S27, when the adhesion amount abnormality detection number N is up to 3, the cleaning performance recovery sequence described later is executed in step S28, and the process returns to step S22 to check the toner adhesion amount on the intermediate transfer belt 3. If the adhesion amount abnormality detection count is 3 times or more in step S27, that is, if the toner adhesion amount exceeds a predetermined value even if the cleaning performance recovery sequence is executed three times, the cleaning performance of the brush must be recovered. In step S29, the life of the brush cleaning device 14 is determined.

The number of adhesion amount abnormality detections is not limited to three, and may be four or more. Also, the toner adhesion amount abnormality determination threshold value after execution of the cleaning performance recovery sequence is made smaller than the toner determination abnormality threshold value after execution of the cleaning performance inspection sequence (for example, 0.5 g / m ² ), so that strict checking is performed. Good.

<Cleaning performance recovery sequence>
FIG. 9 shows a flow of the cleaning performance recovery sequence of the brush cleaning device 14.

  First, in step S31, the motors of the intermediate transfer belt 3 and the cleaning brush 17 are turned on, and the intermediate transfer belt 3 and the cleaning brush 17 are driven to rotate. In step S32, the cleaning current applied to the collection roller 18 from the high-voltage power supply circuit 21 is dropped to the ground for a predetermined time or set to a reverse polarity current value. As a result, the toner deposited on the cleaning brush 17 is discharged onto the intermediate transfer belt 3. Next, in step S33, the cleaning current applied to the collection roller 18 from the high-voltage power supply circuit 21 is set to a normal current value (for example, 20 μA) for a predetermined time. As a result, the toner discharged onto the intermediate transfer belt 3 is removed from the intermediate transfer belt 3 by a normal cleaning operation and is collected in the casing 15 via the collection roller 18 without being deposited on the cleaning brush 17. Is done. Note that the toner deposited on the cleaning brush 17 can be more effectively removed by repeating the discharging of the accumulated toner in step S32 and the re-cleaning in step 33 several times. When the cleaning is finished, in step 34, the motors of the intermediate transfer belt 3 and the cleaning brush 17 are turned off.

FIG. 10 is a time chart showing how much the intermediate transfer belt driving time for one job can be shortened according to the present invention as compared with the prior art.
Conventionally, since the cleaning performance state could not be detected, the cleaning performance recovery sequence had to be executed for each job regardless of the cleaning performance state. That is, as shown in FIG. 10A, since the cleaning performance recovery sequence is always executed after the image formation for one job (for example, one page), the intermediate transfer belt motor takes about the same time as the original image formation. And the cleaning brush motor was driven. For this reason, the lifetime of the apparatus is considerably shortened during intermittent printing (for example, 1 page / 1 job) as compared with continuous printing (for example, 100 pages / 1 job).
In the present invention, since the amount of toner deposited on the brush is very small for printing about 100 sheets, as shown in FIG. 10B, it is not necessary to enter the cleaning performance recovery sequence for each job in the normal state. As shown in FIG. 10C, the cleaning performance inspection sequence is executed periodically (for example, every 100 sheets printed), and the cleaning performance recovery sequence is executed only when toner is left unwiped. It is possible to reduce the driving time.

  The above embodiment is a tandem image forming apparatus in which four imaging units 2Y, 2M, 2C, and 2K are arranged along the intermediate transfer belt 3. However, the present invention is not limited to this, and the intermediate transfer is not limited thereto. A four-cycle image forming apparatus that rotates the belt four times to sequentially cause the four imaging cartridges to face the intermediate transfer belt, or direct transfer that sequentially transfers from the photoreceptor to the paper while adsorbing and transporting the paper onto the transfer belt. The present invention can also be applied to a type image forming apparatus.

1 is a schematic diagram of an image forming apparatus according to the present invention. The enlarged view of the brush cleaning apparatus of FIG. The figure which shows the relationship between a toner adhesion amount and the output of a toner sensor. The figure which shows the relationship between a secondary transfer voltage and a toner adhesion amount. 5 is a flowchart showing an example of a cleaning performance inspection sequence. The top view (a) and bottom view (b) of the intermediate transfer belt on which the inspection pattern is formed. 9 is a flowchart showing another example of the cleaning performance inspection sequence. The flowchart which shows the cleaning performance determination flow. The flowchart of a cleaning performance recovery sequence. FIG. 3 is a comparison diagram of an image forming sequence according to the related art and the present invention.

Explanation of symbols

1 Image forming apparatus 3 Intermediate transfer belt (transfer member)
12 Toner sensor 13 Secondary transfer roller (second transfer member)
14 Brush Cleaning Device 17 Cleaning Brush 21 High Voltage Power Supply Circuit 22 Control Circuit

Claims (3)

A transfer member to which a toner image is transferred;
A brush cleaning device that removes toner remaining on the transfer member by applying a cleaning current;
A toner sensor for detecting toner on the transfer member after passing through a brush cleaning device,
The inspection pattern is transferred onto the transfer member at a predetermined timing, and the current value of the cleaning current of the brush cleaning device is lowered than normal, and the transfer after the inspection pattern passes the brush cleaning device by the toner sensor. When the toner on the member is detected and the toner sensor detects a toner adhesion amount that exceeds a reference, the cleaning current is changed to discharge toner deposited on the brush of the brush cleaning device onto the transfer member, An image forming apparatus, wherein cleaning performance recovery control is performed to return the cleaning current to an original state and remove toner discharged on the transfer member. A transfer member to which a toner image is transferred;
A brush cleaning device that removes toner remaining on the transfer member by applying a cleaning current;
A toner sensor for detecting toner on the transfer member after passing through a brush cleaning device ;
A secondary transfer member that transfers the toner image on the transfer member to an adjacent member ;
The inspection pattern is transferred onto the transfer member at a predetermined timing, and a secondary transfer voltage is applied to the secondary transfer member to neutralize or reversely charge the toner charge amount of the inspection pattern, and the inspection is performed by the toner sensor. Toner deposited on the brush of the brush cleaning device by changing the cleaning current when the pattern detects toner on the transfer member after passing through the brush cleaning device and the toner sensor detects an amount of toner adhering above a reference. After the toner is discharged onto the transfer member, cleaning performance recovery control is performed to restore the cleaning current and remove the toner discharged onto the transfer member. If the cleaning performance recovery control once or the toner sensor be performed more times of detecting the toner adhesion amount of more than the reference, according to claim 1, characterized in that to determine the life of the brush cleaning apparatus, or the image forming apparatus according to 2.

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