JP2009015179A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely detect a discharge product adhering to the surface of an image carrier so as to precisely perform cleaning processing for removing the discharge product, thereby suppressing image noise such as image deletion and also restraining the life of an electrostatic latent image carrier or the like from getting shorter due to excessive cleaning and abradant (toner or the like) used for cleaning from being wastefully and excessively consumed. <P>SOLUTION: The image forming apparatus 10 includes: a torque measuring part 91 for measuring driving torque of an image carrier 1; a torque rise detection part 92 for detecting that partial torque rise is present when the partial torque rise is found in the driving torque measured by the torque measuring part 91; a grinding cleaning means (cleaning device 6 or the like) for the surface of the image carrier; and a cleaning control part 93 for controlling the grinding cleaning means to grind and clean the surface of the image carrier on a condition that the torque rise detection part 92 detects that the partial torque rise is present. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a combination machine combining two or more of these, capable of forming an image by electrophotography.

  In an electrophotographic image forming apparatus, the surface of an electrostatic latent image carrier represented by a rotationally driven photosensitive member is usually charged by a charging device, and an image to be formed from the image exposure device in the charging area is determined. The latent image is exposed to form an electrostatic latent image, and the electrostatic latent image is developed by a developing device to form a toner image.

  Various types of charging devices for charging an electrostatic latent image carrier (hereinafter, sometimes simply referred to as “image carrier”) are known. Examples include those that charge the image carrier (typically a corona charging device) and those that perform injection charging but also charge the image carrier with discharge (for example, those charged by a charging roller).

  In any case, when a charging device with a discharge phenomenon is used for charging the image bearing member, ozone is generated by the discharge, which reacts with nitrogen in the air to generate nitrogen oxide (NOx), and this NOx becomes air. It reacts with moisture in the inside (especially when it reacts with moisture in a high-humidity environment) to form nitrate, and the nitrate tends to adhere to the surface of the image carrier as a discharge product.

  When nitrate is attached to the surface of the image carrier, the attached portion easily adsorbs moisture in the air. Adsorption of water reduces the surface resistance of the image carrier, and the image is blurred when forming an electrostatic latent image. Such image noise such as so-called image flow occurs.

  For this reason, a technique has been proposed in which when a discharge product such as nitrate adheres to the image carrier, it is removed by cleaning.

  For example, Japanese Patent Laid-Open No. 2000-47545 discloses a cleaning device that cleans and removes transfer residual toner remaining after a toner image formed on a photoconductor is transferred to a recording medium or the like, and contacts the surface of the photoconductor. In an image forming apparatus provided with a cleaning device using a cleaning blade, when discharge products adhere to the surface of the photoreceptor, resistance to mutual sliding between the cleaning blade and the surface of the photoreceptor increases at that portion, and the photoreceptor driving torque is increased. By using this increase, the adhesion of the discharge product is detected by detecting the fluctuation of the photoconductor drive torque from the normal one. When the discharge product adhesion is detected, the toner is transferred from the developing device to the photoconductor. It is described that a charged polarity abrasive is supplied under bias control, and the discharge product is scraped off with a cleaning blade using this abrasive. .

Japanese Patent Application Laid-Open No. 2006-234894 discloses that in an image forming apparatus provided with a cleaning device that uses a cleaning blade as a cleaning device for a photoconductor, a change in driving torque of the photoconductor is detected to generate discharge on the photoconductor. It is described that when adhesion of an object is detected and adhesion of a discharge product is detected, a belt-like toner image is formed on the photoreceptor, and the discharge product is scraped off with a cleaning blade using this toner as an abrasive.
JP 2000-47545 A JP 2006-234894 A

  However, the driving torque value of the image carrier greatly changes due to changes in the temperature and humidity around the image forming apparatus, the surface roughness of the image carrier, and the adhesion state of fluorine particles that may be applied to the cleaning blade. More recently, sliding aids such as fluorine particles and silica particles may have been added to the image carrier for the purpose of extending the life of the image carrier such as a photoconductor. Since the additive particles do not sufficiently spread on the surface of the image carrier, the image carrier driving torque value may increase.

  Such fluctuations in the image carrier driving torque due to the temperature and humidity around the image forming apparatus and the surface condition of the entire circumference of the image carrier are particularly caused by the discharge products partially adhering to the image carrier. Since it is larger than the partial torque increase caused by adhering to the part of the body facing the charging device, it is difficult to detect the adhesion of the discharge product that causes image flow or the like only with the torque value.

  For this reason, when the adhesion of the discharge product on the image carrier is detected only from the driving torque value of the image carrier as in the prior art, the discharge product cannot be detected and image noise is generated or excessive to prevent this. The image carrier and the cleaning device are quickly consumed by proper cleaning control, or the abrasive (toner etc.) is excessively used for the abrasive cleaning of the discharge product. As a whole, the life of the image forming apparatus is shortened.

  Therefore, the present invention charges the surface of a rotating electrostatic latent image carrier with a charging device that accompanies discharge, and performs image exposure according to an image to be formed from the image exposure device on the charged area, thereby developing the electrostatic latent image. Forming an image, developing the electrostatic latent image with a developing device to form a toner image, and transferring the toner image to a transfer target; after the transfer, the electrostatic latent image carrying surface is brought into contact with the surface; An image forming apparatus that can be cleaned with a cleaning member that rubs, and reliably detects discharge products adhering to the surface of the image carrier as the electrostatic latent image carrier is charged by the charging device. An electrostatic latent image carrier caused by excessive discharge product removal cleaning while being able to accurately perform object cleaning and removal processing, thereby suppressing image noise such as image flow and forming a good image. Used for shortening life and cleaning It is possible to suppress the wasteful excessive consumption abrasive, and to provide an image forming apparatus capable of much longer life.

In order to solve the above problems, the present invention provides the following image forming apparatus.
The surface of the electrostatic latent image carrier to be rotated is charged by a charging device that accompanies discharge, and an image exposure according to an image to be formed from the image exposure device is applied to the charging area to form an electrostatic latent image. A cleaning member that develops the electrostatic latent image with a developing device to form a toner image, transfers the toner image to a transfer target, and rubs the electrostatic latent image carrying surface after the transfer in contact with the surface An image forming apparatus that can be cleaned with
Torque measuring means for measuring the waveform of the driving torque of the electrostatic latent image carrier;
A torque increase detecting means for detecting the presence of the partial torque increase when there is a partial torque increase in the driving torque waveform measured by the torque measuring means;
Polishing cleaning means for the surface of the electrostatic latent image carrier;
An image forming apparatus comprising: a cleaning control unit that causes the polishing cleaning unit to polish and clean the surface of the electrostatic latent image carrier on condition that the torque increase detection unit detects the presence of the partial torque increase. is there.

  In the image forming apparatus according to the present invention, the cleaning member is disposed in contact with the electrostatic latent image carrier so as to rub the surface. Therefore, the driving torque when rotating the electrostatic latent image carrier is affected by the resistance of the cleaning member, and when the discharge product accompanying charging by the charging device is attached to the electrostatic latent image carrier, The drive torque locally increases at the discharge product adhering portion.

  In the image forming apparatus according to the present invention, the waveform of the driving torque of the electrostatic latent image carrier is measured by the torque measuring means, and the torque increase detecting means is partially applied to the waveform of the driving torque measured by the torque measuring means. If there is a torque increase, the presence of the partial torque increase is detected. Thereby, adhesion of the discharge product is reliably detected.

  Then, on the condition that the torque rise detecting means detects the presence of the partial torque rise, the electrostatic latent image carrier polishing cleaning means polishes and cleans the surface of the electrostatic latent image carrier under the instruction of the cleaning control means. Then, the discharge product is removed by cleaning. The cleaning removal of the discharge product is performed under the condition that the torque increase detection means detects the presence of the partial torque increase, and is therefore performed accurately without waste.

  Thus, image noise such as image flow can be suppressed and a good image can be formed, and the electrostatic latent image carrier caused by excessive discharge product removal cleaning can be shortened and wasteful particles used for cleaning can be used. Consumption can be suppressed, and the life of the image forming apparatus can be extended accordingly.

A typical example of the electrostatic latent image carrier is a photoreceptor.
The electrostatic latent image bearing member can be cleaned by relative rubbing with the electrostatic latent image bearing member by the cleaning member after the toner image formed thereon is transferred to the transfer target. The cleaning device may also serve as all or part of the polishing cleaning means.

  Examples of the cleaning member include a cleaning blade that is in a fixed position and rubs the surface of the electrostatic latent image carrier, and includes a cleaning roller, a cleaning brush, and a cleaning blade that rubs the surface of the image carrier. A sleeve or the like may be used.

  The toner image formed on the electrostatic latent image bearing member can be transferred to the transfer target. However, the transfer may be performed directly on the recording medium, and after the primary transfer to the intermediate transfer member, the recording is performed. Secondary transfer onto the medium may be performed, and it can be said that both the recording medium and the intermediate transfer member are transferred.

  A typical example of the charging device with discharge is a corona charging device, but a roller charging device, a brush charging device, a sheet charging device, or the like may also be used.

  The torque increase detection means includes the presence of the partial torque increase when the number of inflection points in the driving torque waveform of the electrostatic latent image carrier measured by the torque measurement means is equal to or greater than a predetermined number. Can be exemplified. In this case, it is desirable to detect the presence of a partial torque increase when the number of inflection points in the waveform obtained by removing noise from the drive torque waveform of the electrostatic latent image carrier is equal to or greater than a predetermined number.

  Further, the basic value of the electrostatic latent image carrier that can be regarded as normal and the integrated value of the measured torque data forming the waveform of the driving torque of the electrostatic latent image carrier measured by the torque measuring means. It can also be exemplified that the presence of the partial torque increase is detected when the difference from the integrated value of the basic torque data forming the waveform of the drive torque is not less than a predetermined value.

Attachment of the discharge product to the electrostatic latent image carrier is likely to occur when the installation environment of the image forming apparatus is high humidity or when it is left for a long time after the last image forming apparatus.
Therefore, in the image forming apparatus according to the present invention, at least one of the humidity in the environment where the image forming apparatus is installed is equal to or higher than a predetermined humidity and that a predetermined time has elapsed since the last image formation is satisfied. On the condition that the torque measuring means measures the waveform of the driving torque of the electrostatic latent image carrier, the torque rise detecting means detects the presence of the partial torque rise, and the torque rise When the detection means detects the presence of the partial torque increase, the cleaning control means may cause the polishing cleaning means to polish and clean the surface of the electrostatic latent image carrier.

  According to the present invention, the surface of the electrostatic latent image carrier that is driven to rotate is charged by a charging device that accompanies discharge, and the charged region is subjected to image exposure in accordance with an image to be formed from the image exposure device, thereby electrostatic latent Forming an image, developing the electrostatic latent image with a developing device to form a toner image, and transferring the toner image to a transfer target; after the transfer, the electrostatic latent image carrying surface is brought into contact with the surface; An image forming apparatus that can be cleaned with a cleaning member that rubs, and reliably detects discharge products adhering to the surface of the image carrier as the electrostatic latent image carrier is charged by the charging device. An electrostatic latent image carrier caused by excessive discharge product removal cleaning while being able to accurately perform object cleaning and removal processing, thereby suppressing image noise such as image flow and forming a good image. Used for shortening life and cleaning It is possible to suppress the wasteful excessive consumption abrasive, it is possible to provide an image forming apparatus capable of much longer life.

Hereinafter, an example of an image forming apparatus according to the present invention will be described with reference to the drawings.
FIG. 1 shows an example of an image forming apparatus according to the present invention.
An image forming apparatus 10 in FIG. 1 includes a photoreceptor 1 as an electrostatic latent image carrier, and a charging device 2, an image exposure device 3, a developing device 4, a transfer device 5, and a cleaning device 6 around the photoreceptor 1. Are arranged in this order.

  In addition to this, the image forming apparatus 10 transfers a recording medium supply unit (not shown) and a recording medium S supplied from the recording medium supply unit at predetermined timing to the transfer member (transfer in this example) of the photosensitive member 1 and the transfer device 5. A timing roller pair 7 to be supplied to the roller 51) and a fixing device 8 disposed on the downstream side of the transfer roller 51 in the recording medium conveyance direction are also included.

  FIG. 2 is a block diagram illustrating an outline of a control circuit of the image forming apparatus 10. Reference numeral 9 in the control circuit is a control unit for controlling the operation of each unit of the image forming apparatus. Each unit of the image forming apparatus operates under the instruction of the control unit 9.

The control unit 9 includes
A torque measuring unit 91 that functions as a torque measuring unit that measures the waveform of the photoconductor driving torque; based on the waveform of the driving torque measured by the torque measuring unit 91, if the measured driving torque has a partial torque increase, A partial torque increase detection unit 92 functioning as a means for detecting the presence of a static torque increase, and a photoconductor polishing cleaning unit including the cleaning device 6 on condition that the torque increase detection unit 92 detects a partial torque increase Also included is a cleaning control section 93 that functions as a cleaning control means for performing polishing cleaning of the surface of the photoreceptor.

  The torque measurement unit 91, the partial torque increase detection unit 92, the polishing cleaning unit and the cleaning control unit 93 will be described in detail later.

  The photoreceptor 1 can be driven to rotate clockwise in FIG. 1 by a photoreceptor drive motor 11. The motor 11 is rotated by the motor drive circuit 12 at a predetermined timing under the instruction of the control unit 9. In this example, the photosensitive member 1 is a negatively chargeable drum type organic photosensitive member, and has an outer diameter of 30 mm and a width of 280 mm in the rotation axis direction.

  The photoreceptor 1 does not need to be negatively charged, and may be positively charged depending on the charging polarity of the toner used in the developing device 4. An amorphous silicon type photoreceptor can also be used.

  In this example, the charging device 2 includes a corona discharge electrode 21 extending in the rotation axis direction (photosensitive member width direction) of the photosensitive member 1 and a grid-shaped control electrode 22 between the electrode 21 and the photosensitive member 1 in this example. And a shield plate 23 having a U-shaped cross-section covering the electrode 21 from three sides not facing the photoreceptor 1. Each of these is held by a holder (not shown) at both ends.

  A flexible urethane resin seal member (not shown) is provided at each of the upstream end and the downstream end in the direction of movement of the photoconductor surface of the shield plate 23 with respect to the photoconductor surface. Lightly touching the body 1 surface.

  The shield plate 23 is provided with an air suction port and an exhaust port (not shown), and the exhaust port is connected to an exhaust route (not shown). The charging device 2 is provided with an ozone removal filter and an exhaust fan provided in the exhaust route. Ozone generated inside can be removed.

  The charging device 2 is driven to rotate when the voltage for charging the photoconductor is applied to each of the discharge electrode 21 and the control electrode 22 from a power source (not shown) under the instruction of the control unit 9. The surface can be uniformly charged to a predetermined potential.

Note that the cross-sectional shape of the shield plate is not limited to a U-shape.
The ozone removal mechanism may not be provided.
In the above example, the charging device 2 is a corona charging device that employs a discharge electrode such as a wire electrode or a sawtooth electrode. However, a charging roller, a charging brush, or the like may be employed as a charging member.

  The image exposure apparatus 3 can perform image exposure on the photosensitive member 1 using a laser beam modulated by an image signal supplied from a personal computer (not shown), an image reading apparatus, or the like.

  In this example, the developing device 4 is a so-called one-component developing device that can reversely develop the electrostatic latent image on the photosensitive member 1 by the developing roller 41 using negatively charged toner. At least at the time of developing an electrostatic latent image, the developing roller 41 is rotationally driven by a developing roller drive motor (not shown) under the instruction of the control unit 9, and a developing bias is applied from a power supply (not shown).

  In this example, the transfer device 5 includes a transfer roller 51 that faces the photoreceptor 1 and forms a transfer region. The transfer roller 51 is an elastic roller having at least a surface layer portion made of an elastic material, and is a conductive roller. When transferring the toner image on the photosensitive member to the recording medium S, a transfer voltage is applied to the transfer roller 51 from a transfer power supply (not shown). The transfer device 5 may include a contact / separation mechanism of the transfer roller 51 with respect to the photoreceptor 1.

  The cleaning device 6 includes a cleaning blade 61 that scrapes off toner remaining on the photosensitive member 1 by rubbing the surface as the surface of the photosensitive member 1 moves, and a storage unit 62 that stores the scraped toner and the like. Including.

  The cleaning blade 61 is not limited to this, but in this example, the Asker C hardness is 76 degrees, the thickness is 2 mm, the width (width in the direction of the photosensitive member rotation axis) is 235 mm, and the free length is 10 mm. The surface of the photoconductor 1 is held in contact with the contact pressure of 7N.

The cleaning blade 61 may be supported by a support shaft so as to be swingable, and may be brought into contact with the surface of the photoreceptor 1 by applying a spring force. The cleaning member is not limited to the cleaning blade, and may be a cleaning roller, a cleaning brush, or the like as long as it relatively rubs the surface of the photoreceptor 1.
The cleaning member may be separated from the photoconductor 1 in a packing state before shipment, when the image forming apparatus is turned off, in a so-called sleep mode in preparation for the next image formation in the image forming apparatus.

  The fixing device 8 includes, but is not limited to, a fixing heating roller 81 incorporating a heat source such as a halogen lamp heater and a pressure roller 82 facing the fixing heating roller 81 in this example.

According to this image forming apparatus 10, an image can be formed as follows.
Under the instruction of the control unit 9, the photosensitive member 1 is rotated clockwise in FIG. 1 by the photosensitive member driving motor 11, the surface thereof is uniformly charged to a predetermined potential by the charging device 2, and image exposure is performed in the charged region. The electrostatic latent image is formed by performing image exposure according to the image to be formed from the apparatus 3, and this is developed by the developing roller 41 of the developing apparatus 4 to form a visible toner image.

  On the other hand, the recording medium S (recording paper, overhead projecting recording medium, etc.) is pulled out from a recording medium supply unit (not shown), conveyed to the timing roller pair 7 and waited there. At the timing when the toner image formed on the photoreceptor 1 arrives at the transfer area, the timing roller pair 7 feeds the waiting recording medium to the transfer area, and the transfer device 5 transfers the toner image to the recording medium S. Transcript. Subsequently, the recording medium S is passed through the fixing device 8 to fix the toner image and discharged to a tray (not shown). Residual toner remaining on the photosensitive member 1 is removed and cleaned by the cleaning device 6 to prepare for the next image formation.

  According to the image forming apparatus 10, an image can be formed in this way, but ozone is generated by discharge when the surface of the photoreceptor 1 is charged by the charging device 2, and this reacts with nitrogen in the air to generate nitrogen oxides (NOx). ) And NOx reacts with moisture in the air (especially when it reacts with moisture in a high humidity environment) to form nitrate, which is likely to adhere to the photoreceptor surface as a discharge product. .

  When nitrate adheres to the surface of the photoconductor, the adhering portion easily adsorbs moisture in the air, and adsorbing water reduces the surface resistance of the photoconductor portion, and the image looks blurry when forming an electrostatic latent image. Image noise such as so-called image flow occurs.

  Therefore, in the image forming apparatus 10, the torque measurement unit 91 and the partial torque increase detection unit 92 are provided to detect the adhesion of the discharge product on the photoreceptor 1, and when the adhesion of the discharge product is detected, the cleaning control unit Under the instruction of 93, the photosensitive member 1 is polished and cleaned by polishing cleaning means including the cleaning device 6.

Hereinafter, the torque measurement and the like will be described.
<Measurement of photoreceptor driving torque>
The torque measuring unit 91 picks up a motor load current representing the photosensitive member driving torque from the driving circuit 12 of the photosensitive member driving motor 11 and measures the waveform of the driving torque. This is based on the fact that the load current of the photosensitive member driving motor changes substantially linearly in proportion to the photosensitive member driving torque.

  Here, the torque measurement unit 91 performs torque measurement during non-image formation. Here, “at the time of non-image formation” means that an image based on image data from an image forming apparatus user (specifically, for example, from a computer or the like) is in either a developed state or a transfer remaining state. It indicates a state where no toner is present, that is, a state where the toner is not adhered to the photoreceptor 1 or the toner is uniformly adhered or adhered in a predetermined pattern.

  Thus, if there is a partial torque increase in the waveform of the drive torque measured by the torque measuring unit 91, the photoconductor 1 is polished and cooled, but a torque increase detection for detecting the presence of the partial torque increase. A specific example will be described below.

<Example of partial torque rise detection>
A partial torque increase is detected by an increase in the number of inflection points relative to the number of inflection points in the drive torque waveform that can be regarded as normal per circumference of the photoreceptor 1.

FIG. 3 shows an example of the photosensitive member driving torque waveform measured by the torque measuring unit 91. In the example of FIG. 3, there are two partial torque increases (two locations indicated by p and q in the figure) between the circumference of the photoreceptor.
Since the torque waveform measured by the torque measurement unit 91 may include some errors, when processing torque data in the torque increase detection unit 92, an average waveform obtained by averaging torque waveforms for a plurality of photoconductor rounds is used. It is desirable to use it to detect the presence or absence of a partial torque increase, here it is.
Further, since the drive torque measurement value may contain noise, it is desirable to remove it. Here, the number of times of torque measurement is 10,000 times at approximately equal time intervals per one rotation of the photosensitive member, and the torque rise detection unit 92 averages the measured values for every 100 measured values, thereby removing noise as 100 data.

Even after noise removal, the torque waveform does not become completely constant, and in most cases, the torque waveform has the same increase / decrease as the photosensitive member rotation period. Here, a case where a partial torque increase is detected will be described by taking as an example a case where the torque waveform after noise draws a sine curve.
4A, 4B, and 4C show examples of torque waveforms having a partial torque increase. The part shaded by the vertical line is the partial torque increase part. In either case, the starting point and the ending point of the partial torque increasing portion are convex downward, and the apex portion of the partial torque increasing portion is convex upward. As a result, as shown in FIG. 4A or FIG. 4B, when the start point or end point of the partial torque rise is in the lower half of the sine curve, there is no partial torque rise (the inflection point is shown in the figure). The inflection point is increased by 2 points (a1, a2) compared to the middle a).

In addition, as shown in FIG. 4C, when the start point or end point of the partial torque rise does not exist in the lower half of the sine curve, the change point is different from the case where there is no partial torque rise (the inflection point is b in the figure). The number of music points increases by 4 (b1, b2, b3, b4).
As described above, a partial torque increase can be detected from an increase in the inflection point.

  As described above, the case where the torque waveform is a sine curve has been explained as an example. Even when there are a plurality of inflection points, the number of inflection points in the torque waveform immediately before the power supply 0FF or immediately before entering the sleep mode is controlled as a basic inflection point number, in which there is no partial torque increase, the photoreceptor is new, etc. By storing in the unit 9 and detecting an increase in the number of inflection points with respect to the stored number of inflection points, it is possible to detect a partial torque increase in the same manner as described for the sine curve.

<Other examples of partial torque rise detection>
A partial torque increase is detected by comparison with a basic waveform of an initial torque such that the photoconductor or the like is new.
While measuring the photoconductor drive torque under various conditions, the torque waveform when no discharge product is attached to the photoconductor is determined to be almost constant according to the variation and combination of parts, and the waveform changes almost. I found that there was no.

Therefore, as a basic torque waveform to be compared with the waveform of the photoconductor driving torque measured for detecting a partial torque increase at the time of non-image formation immediately after turning on the power of the image forming apparatus or immediately after returning from the sleep mode, The torque waveform at the time of non-image formation immediately before turning off the power and immediately before entering the sleep mode is obtained and stored in the control unit 9.
Since the torque waveform includes some errors, it is desirable that the torque data be compared with an average waveform obtained by averaging the torque waveforms for a plurality of photoreceptors.

  However, the torque average value, the amplitude of the torque waveform, noise, etc. are the environment around the image forming apparatus (temperature and / or humidity), the coefficient of dynamic friction due to changes in the surface roughness of the photoconductor, the cleaning blade that contacts the photoconductor, etc. It changes due to deformation of elastic members such as seals for preventing toner leakage, etc., which may be provided in the cleaning member, developing roller, and developing device, and wear of various sliding parts.

Accordingly, the maximum value Rmax1 and the minimum value Rmin1 of the basic torque waveform are determined by determining the coefficients A and B so that the following formulas are established with respect to the maximum value Smax and the minimum value Smin of the measured torque waveform to be compared. Data Rnl is corrected to Rn2.
ΔR1 = Rmax1-Rmin1
ΔS = Smax−Smin
ΔS = A × ΔR1 (Adjusted with the correction coefficient A so that ΔR1 matches ΔS)
Smax = Rmax1 × A + B (the correction coefficient B aligns the height positions of Smax and Rmax1)
Rn2 = Rn1 × A + B

A comparison between the basic torque waveform and the measured torque waveform will be described with reference to FIG. A broken basic torque waveform is indicated by a broken line in FIG.
When there is no partial torque increase, the difference between the corrected basic torque waveform and the measured torque waveform is almost zero over the entire circumference of the photoconductor, so that Σ | Sn−Rn2 | ≈0 (Sn is measured torque waveform data) and Become.

When there is a partial torque increase, as illustrated in FIG. 5A, FIG. 5B, and FIG. 5C, when the measured torque waveform is overlapped with the basic torque waveform, a difference occurs. Therefore, Σ | Sn−Rn2 |> 0, and a partial torque increase can be detected.
Considering that the measurement data includes some noise, the partial torque increase may be determined to be partial torque increase when Σ | Sn−Rn2 | ≧ X.

X is an arbitrary value, and is a threshold value for discriminating noise and partial torque increase. A common value can be used as long as the apparatus has the same form, and it may be obtained in advance by experiments or the like, or can be determined empirically.

<Timing to detect partial torque rise>
A decrease in the surface resistance of the photoreceptor 1 that causes image flow is likely to occur in a high humidity environment. In a low humidity environment, NOx changes to nitrate and moisture adsorption to nitrate hardly occur, and the surface resistance hardly changes, so that image flow hardly occurs.

  Accordingly, the humidity sensor 100 is provided in the image forming apparatus 10 and humidity information detected by the sensor is input to the control unit 9 to detect a partial torque increase only when the relative humidity is 60% or more, for example. Thus, it is possible to prevent parts from being consumed by driving the photosensitive member accompanying torque detection.

The discharge product may adhere to the photosensitive member by gradually releasing N0x or the like adhering to the charging device while the charging device is stopped, so the humidity between the end of image formation and the start of re-image formation is Affects image flow.
Therefore, the humidity from the last image formation to the re-image formation is detected at least once and stored in the control unit 9, and either humidity is determined by looking at both this and the humidity information from the sensor 100 immediately before the start of image formation, for example. Alternatively, a partial torque increase may be detected when the humidity is likely to cause image flow to be equal to or higher than a predetermined humidity (for example, 60% RH).
For example, when the relative humidity immediately after the end of image formation is 85% RH and the relative humidity 5 hours after the end of image formation is 50% RH, a partial torque increase may be detected.

  Also, the adhesion of nitrate to the photoreceptor and the adsorption of moisture to the nitrate does not occur immediately but proceeds over several hours. In addition, in the case of a mechanism that removes ozone from the charging device, even if the ozone concentration immediately after image formation is low, ozone or discharge products adsorbed in the charging device are released by leaving it for several hours. Nitrate may be deposited on the photoreceptor.

  Therefore, for example, the partial torque increase may be detected only when the image is not formed for a predetermined time (for example, 3 hours) after the final image formation.

<Example of polishing cleaning control of discharge product>
In this way, when the partial torque increase detection unit 92 in the control unit 9 detects that there is a partial torque increase in the driving torque of the photosensitive member 1, the cleaning control unit 93, for example, prior to the next image formation, the photosensitive member. 1 is rotated, and toner is supplied onto the photosensitive member 1 as an abrasive by the charging device 2, the image exposure device 3, and the developing device 4.

For example, the toner supply may be performed only partially on the surface of the photoreceptor 1. For example, the toner is supplied by forming a belt-like toner image having a length in the moving direction of the photoreceptor surface of 50 mm and extending over the entire development width by the developing device 4. it can. Then, the toner for polishing cleaning is supplied in this way and the photoreceptor 1 is rotated, for example, for 1 minute, so that the surface of the photoreceptor 1 is polished by the polishing toner and the cleaning member 61 of the cleaning device 6 to nitrate or the like. The discharge product is polished and removed.
Here, it can be said that the cleaning device 6, the image exposure device 3, the developing device 4, etc. constitute polishing cleaning means for polishing and cleaning the surface of the photoreceptor 1.

The polishing toner image pattern on the photosensitive member 1 is not necessarily limited to the above-described belt-like one.
Other patterns such as dots and stripes may be used, development may be performed a plurality of times, and the driving time of the photoreceptor 1 is also arbitrary. A developer may be interposed on the photoreceptor 1 so long as a good polishing cleaning effect can be obtained.

  In addition, after the cleaning control is completed, the partial torque increase detection process is performed again. If there is no partial torque increase, the polishing cleaning process is terminated. If the partial torque increase is detected again, the cleaning control is repeated. May be.

  The partial torque increase may occur without being caused by the discharge product. Therefore, the cleaning control may be stopped when the partial torque increase does not decrease even when the cleaning control is performed, or when the number of cleaning repetitions exceeds a predetermined value. And it is desirable to rewrite the reference data for detecting the partial torque rise.

  When the transfer device 5 has a mechanism for contacting and separating the photosensitive member 1, it is desirable that the transfer device 5 be separated from the photosensitive member 1 during polishing cleaning of the photosensitive member 1.

FIG. 6 shows an outline of the operation of the control unit 9 related to the photoconductor polishing cleaning process.
As shown in FIG. 6, when the image forming apparatus is turned on or returned from the sleep mode (step S1), the photosensitive member driving torque waveform is measured (step S2), and a partial torque increase is detected. When the process is performed (step S3), and as a result, a partial torque increase is recognized (step S4), the photosensitive member polishing cleaning process is executed and the cleaning count is incremented by one (steps S5 and S6). The body drive torque is measured and the partial torque increase is detected (steps S7 and S8). As a result, when the partial torque increase is recognized (step S9), the photoconductor polishing cleaning process is executed again (step S5). . However, when the number of cleanings reaches the predetermined number N, warning means (not shown) is warned (steps S10 and S11).

In the above-described polishing of the discharge product, toner is supplied to the photoreceptor 1 as an abrasive. However, an abrasive supply device may be provided to supply the abrasive to the photoreceptor at the timing of polishing cleaning. Good.
For example, an abrasive material supply device is provided between the transfer device 5 and the cleaning device 6, and an abrasive material such as silica particles is supplied (for example, applied) to the photoconductor 1 from there for a predetermined time (for example, 1 minute). ) It may be driven to rotate for cleaning control.

  In the polishing cleaning of the discharge product, if polishing cleaning is possible, the photosensitive member surface is driven by the rotation of the photosensitive member and the cleaning member 61 of the cleaning device 6 without using abrasive particles such as toner and other abrasives. The discharge product may be removed by polishing and cleaning the surface of the photoreceptor only by rubbing. For example, after detecting the partial torque increase, the photosensitive member 1 is rotationally driven for 3 minutes.

  The polishing cleaning of the photosensitive member 1 may be more efficiently performed by intensively performing polishing cleaning on the portion of the photosensitive member 1 that causes a partial increase in torr.

  The image forming apparatus 10 described above is a monochrome image forming apparatus, but the present invention can also be applied to a color image forming apparatus.

  In the present invention, the surface of the electrostatic latent image carrier to be rotationally driven is charged by a charging device, and image exposure according to an image to be formed from the image exposure device is performed on the charging area to form an electrostatic latent image. An image forming apparatus capable of developing a toner image by developing the electrostatic latent image with a developing device, and capable of accurately performing a cleaning removal process on discharge products adhering to the surface of the image carrier Can be used to provide.

1 is a diagram illustrating an example of an image forming apparatus according to the present invention. FIG. 2 is a block diagram illustrating an outline of a control circuit of the image forming apparatus in FIG. 1. It is a figure which shows an example of the measurement waveform of a photoreceptor drive torque. Each of FIGS. 4A, 4B, and 4C is a diagram illustrating a detection example of a partial torque increase in the photosensitive member driving torque waveform. FIG. 5A, FIG. 5B, and FIG. 5C are diagrams showing other examples of partial torque increase detection in the photoreceptor driving torque waveform. 6 is a flowchart illustrating an example of a photoreceptor polishing cleaning process performed by a control unit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 1 Photoconductor 11 Photoconductor drive motor 12 Motor drive circuit 2 Charging device 21 Discharge electrode 22 Control electrode 23 Shield plate 3 Image exposure device 4 Developing device 41 Developing roller 5 Transfer device 51 Transfer roller 6 Cleaning device 61 Cleaning blade 62 Scraping toner storage unit 7 Timing roller pair 8 Fixing device 81 Fixing heating roller 82 Pressure roller 9 Control unit 91 Torque measurement unit 92 Partial torque increase detection unit 93 Cleaning control unit 100 Humidity sensors a, a1, a2, b , B1 to b4 Inflection points in the photoconductor driving torque waveform

Claims (4)

The surface of the electrostatic latent image carrier to be rotated is charged by a charging device that accompanies discharge, and an image exposure according to an image to be formed from the image exposure device is applied to the charging area to form an electrostatic latent image. A cleaning member that develops the electrostatic latent image with a developing device to form a toner image, transfers the toner image to a transfer target, and rubs the electrostatic latent image carrying surface after the transfer in contact with the surface An image forming apparatus that can be cleaned with
Torque measuring means for measuring the waveform of the driving torque of the electrostatic latent image carrier;
A torque increase detecting means for detecting the presence of the partial torque increase when there is a partial torque increase in the driving torque waveform measured by the torque measuring means;
Polishing cleaning means for the surface of the electrostatic latent image carrier;
And a cleaning control means for causing the polishing cleaning means to polish and clean the surface of the electrostatic latent image carrier on condition that the torque increase detection means detects the presence of the partial torque increase. Image forming apparatus.   The torque increase detection means detects the presence of the partial torque increase when the number of inflection points in the drive torque waveform of the electrostatic latent image carrier measured by the torque measurement means is equal to or greater than a predetermined number. The image forming apparatus according to claim 1 for detection.   The torque increase detection means is an integrated value of measured torque data that forms a waveform of the driving torque of the electrostatic latent image carrier measured by the torque measurement means and the electrostatic latent that can be regarded as normal obtained in advance. The image forming apparatus according to claim 1, wherein the presence of the partial torque increase is detected when a difference from an integrated value of basic torque data forming a waveform of a basic driving torque of the image carrier is equal to or greater than a predetermined value.   The torque measurement is performed on condition that at least one of the humidity of the image forming apparatus installation environment is equal to or higher than a predetermined humidity and that a predetermined time has elapsed since the last image formation is satisfied. Means measures the waveform of the driving torque of the latent electrostatic image bearing member, the torque increase detecting means performs the detection process of the presence of the partial torque increase, and the torque increase detection means detects the presence of the partial torque increase. 4. The image forming apparatus according to claim 1, wherein the cleaning control means causes the polishing cleaning means to polish and clean the surface of the electrostatic latent image carrier.