JP2013061471A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress toner which passes through a cleaning blade according to the deterioration of durability of the cleaning blade, and thereby suppress image defects attributed to the pass-by toner.SOLUTION: An image forming apparatus comprises: toner pattern forming means for forming a toner pattern on an image carrier for detection; a blade for removing toner left on the image carrier; detection means which is provided in the downstream side of the blade in the rotation direction of the image carrier, and which detects information related to a toner amount on the image carrier having passed by the blade; and control means which allows the toner pattern forming means to consecutively form a first toner pattern and a second toner pattern whose toner amount per unit area is larger than the first toner pattern, and controls to determine cleaning conditions of the image carrier on the basis of the information related to the toner amount which has passed through the blade in the first and the second toner pattern detected by the detection means.

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, or a fax machine using an electrostatic recording system or an electrophotographic system, and more particularly to an image forming apparatus using a cleaning blade.

  In an image forming apparatus that transfers a toner image formed on an image carrier to a transfer material, there is residual toner that remains on the image carrier without being transferred to the transfer material and needs to be removed. As a cleaning device for removing the residual toner on the image carrier, the cleaning blade is widely used because it is simple and compact, is low in cost, and has an excellent toner removing capability.

  Furthermore, in recent years, the durability life of the image carrier has been extended, and accordingly, the life of the cleaning blade has been required to be further extended. I want to use it as long as possible without replacing the cleaning blade. However, since the cleaning blade deteriorates or sags due to long-term use, toner that passes through the cleaning blade is generated.

  In view of this, there has been a proposal to prevent the occurrence of cleaning failure by accurately detecting the missing or deteriorated tip of the cleaning blade. This is because toner density detection means is provided downstream of the cleaning blade in the rotation direction of the image carrier, a toner pattern for detection is formed and supplied to the cleaning blade, and the toner that has passed through the cleaning blade is removed. This is an invention in which detection is performed by a toner density detection means (Patent Document 1).

JP 08-179574

  However, if the deterioration state of the cleaning blade is predicted from one toner pattern, the accurate deterioration state may not be predicted. There are various amounts of toner per unit area on the image carrier to be removed by the cleaning blade (hereinafter referred to as toner amount). Here, there is generally a relationship between the amount of applied toner removed by the cleaning blade and the time when the cleaning failure (through) starts when the applied amount of toner is continuously removed by the cleaning blade. Further, the time when the toner slips from the cleaning blade starts varies depending on the deterioration state of the cleaning blade.

  That is, the deterioration state of the cleaning blade includes a deterioration state in which cleaning failure is likely to occur with respect to a high-concentration toner application amount with a large amount of toner per unit area, and a low-concentration toner application amount with a small toner amount per unit area. On the other hand, there is a deteriorated state in which a poor toner cleaning failure is likely to occur.

  Accordingly, an object of the present invention is to determine the cleaning condition according to the deterioration state of the cleaning blade, to suppress the toner from slipping out from the cleaning blade and to cause the cleaning failure, and to extend the durable life of the cleaning blade.

  In order to solve the above problems, an image forming apparatus according to the present invention has the following configuration. That is, a detection unit that is disposed downstream of the blade in the rotation direction of the image carrier and detects information on the amount of toner on the image carrier that has passed through the blade, and the toner pattern forming unit, The detection unit is configured to continuously form a toner pattern and a second toner pattern having a larger amount of toner per unit area than the first toner pattern, and pass through the blades in the first and second toner patterns. Control means for controlling to determine a cleaning condition of the image carrier based on information on the toner amount detected by the printer.

  According to the present invention, since the cleaning condition is determined according to the deterioration state due to the durability of the cleaning blade, it is possible to suppress the toner that passes through the cleaning blade and to prevent the occurrence of image defects due to the slipping toner. Thereby, the durable life of the cleaning blade can be extended.

1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to Embodiment 1. FIG. FIG. 3 is a cross-sectional view illustrating a layer configuration of a photosensitive drum and a charger according to the first exemplary embodiment. FIG. 3 is a diagram illustrating a toner sensor according to the first exemplary embodiment. FIG. 3 is a block diagram illustrating a control unit and a toner detection unit according to the first embodiment. FIG. 4 is a diagram illustrating a toner application amount and a slip-through start time according to the first exemplary embodiment. The figure for demonstrating the relationship between the deterioration state of a braid | blade, and a slip-through start time. FIG. 5 is a timing chart of a cleaning performance detection mode according to the first embodiment. FIG. 3 is a flowchart illustrating a cleaning performance detection mode according to the first embodiment. FIG. 4 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to a second embodiment.

  The present invention will be described below with reference to the drawings.

[Example 1]
FIG. 1 is a schematic view showing an image forming apparatus according to the present embodiment. As shown in FIG. 1, the image forming apparatus is an electrophotographic four-color full-color printer. However, the present invention is not limited to this, and a copying machine, a facsimile, or the like using an electrostatic recording method may be used. The configuration of this printer (hereinafter “image forming apparatus”) will be described below.

(Overall configuration of image forming apparatus)
The image forming apparatus shown in FIG. 1 has a drum-type electrophotographic photosensitive member (hereinafter “photosensitive drum”) 1 as an image carrier. The photosensitive drum 1 is supported to be rotatable in the arrow R1 direction. Around the photosensitive drum 1, a primary charger (charging unit) 2, an exposure device 3, a developing device 4, an intermediate transfer belt 5 as an intermediate transfer member, and a cleaning device are sequentially arranged along the rotational direction from the upstream side in the rotational direction. (Photoconductor cleaning means) 6 is disposed. A transfer conveyance belt 7 is disposed below the intermediate transfer belt 5, and a fixing device 8 is disposed downstream of the recording material P in the conveyance direction (arrow A direction).

  In this embodiment, a photosensitive drum 1 having a diameter of 60 mm is used. As shown in FIG. 2, the photosensitive drum 1 is formed by coating a photosensitive layer 1b made of a normal organic photoconductive layer (OPC) on the outer peripheral surface of a grounded drum base 1a made of a conductive material such as aluminum. A protective layer (OCL) 1c having excellent wear resistance is applied and formed thereon. Of these layers, the photoreceptor layer 1b is composed of four layers: an undercoat layer (CPL) 1b1, an injection blocking layer (UCL) 1b2, a charge generation layer (CGL) 1b3, and a charge transport layer (CTL) 1b4. The photosensitive layer 1b is usually an insulator, and has a feature that it becomes a conductor when irradiated with light of a specific wavelength. The charge generation layer 1b is made of a phthalocyanine compound having a thickness of 0.2 μm, and the charge transport layer 1c is made of polycarbonate in which a hydrazone compound having a thickness of about 25 μm is dispersed. The photosensitive drum 1 is rotationally driven in the direction of the arrow R1 at a predetermined process speed (circumferential speed) by a driving means (not shown).

  As shown in the figure, the primary charger 2 has a charging roller (contact charging member) 2 formed in a roller shape. The charging roller 2 is a member that is uniformly charged to a predetermined polarity and potential by applying a charging bias voltage. A charging bias is applied to the charging roller 2 by a charging bias application power source S1. An alternating voltage obtained by superimposing a DC voltage and an alternating voltage is applied as a charging bias from the charging bias application power source S1 to the metal core 2a of the charging roller 2. As a result, the surface of the photosensitive drum is uniformly charged to a predetermined polarity and potential.

  The charging roller 2 is rotatably held at both ends of the cored bar 2a by bearing members (not shown). The bearing member is urged toward the photosensitive drum 1 by a pressing spring (compression spring) 2e as an urging member, whereby the charging roller 2 is pressed against the surface of the photosensitive drum with a predetermined pressing force to be photosensitive. A charging portion (charging nip portion) is formed between the surface of the drum 1. The charging roller 2 is driven to rotate as the photosensitive drum 1 rotates.

  As the exposure device 3, a laser scanner that turns on / off laser light based on image information is used. The laser beam of the exposure device 3 is applied to the charged photosensitive drum surface via a reflection mirror. Thereby, the electric charge of the laser beam irradiation part is removed and an electrostatic latent image is formed.

  The developing device 4 employs a rotary development method, a so-called rotary development method. A rotating body 4A that is driven to rotate in the direction of arrow R4 by a motor (not shown) around the shaft 4a, and four developing devices mounted on the rotating body 4A, that is, black, yellow, magenta, and cyan developing devices 4Y. , 4M, 4C, 4K.

  For example, when a black developer image (toner image) is formed on the photosensitive drum, an electrostatic latent image formed on the photosensitive drum by the black developing device 4K in the developing area D close to the photosensitive drum 1 is used. The toner image is developed. Similarly, when a yellow toner image is formed, the rotating body 4A is rotated by 90 °, and the developing unit 4Y for yellow is disposed at the development position D to perform development. Magenta and cyan toner images are formed in the same manner. In the following description, when it is not necessary to distinguish colors, the developing devices 4Y, 4M, 4C, and 4K are collectively referred to as the developing device 4.

  The above-described intermediate transfer belt 5 is stretched over a drive roller 10, a primary transfer roller (primary transfer charger) 11, a driven roller 12, and a secondary transfer counter roller 13. The rotation of the drive roller 10 causes an arrow R5. Rotate in the direction. The intermediate transfer belt 5 is in contact with a belt cleaner 14 that is an intermediate transfer member cleaning device including a cleaning blade.

  The photoconductor cleaning device 6 is a blade cleaning system in which the edge of a cleaning blade 6a made of urethane rubber is brought into contact with the surface of the photosensitive drum 1 to scrape off the toner. In this embodiment, the cleaning blade 6 a is an elastic blade mainly composed of urethane, and is disposed in contact with the photosensitive drum 1 in a direction opposite to the moving direction of the surface of the photosensitive drum 1 (counter direction). The polyurethane rubber of the cleaning blade used in this example has a hardness of 75 ° (JIS-A) and a thickness of 2 mm, and is brought into contact with the photosensitive member so as to have a pressure of 40 mN / mm. Yes. The cleaning blade is fixed and brought into contact with the photosensitive drum so that the angle formed by the cleaning blade (cleaning blade setting angle) is 25 degrees with respect to the tangential direction.

  The transfer conveyance belt 7 is stretched around a conveyance drive roller 15, a secondary transfer roller 16, and a passive roller 17, and rotates in the direction of arrow R 7 as the conveyance drive roller 15 rotates. The fixing device 8 includes a fixing roller 18 incorporating a heater (not shown), and a pressure roller 20 in contact with the fixing roller 18 from below.

(Image forming operation in image forming apparatus)
The image forming operation of the image forming apparatus will be described below.

  In FIG. 1, a photosensitive drum 1 charged by a primary charger 2 is exposed by an exposure device 3 to form an electrostatic latent image on the photosensitive drum. The electrostatic latent image is developed by a developer containing a developer (toner) of a desired color, and the toner is attached to develop the electrostatic latent image into a toner image. Thereafter, the toner image on the photosensitive drum is primarily transferred onto the intermediate transfer belt by applying a primary transfer bias voltage to the primary transfer roller 11. The process speed of the image forming apparatus used in this embodiment and the rotational speed of the photosensitive drum were set to 200 mm / s.

  When four-color full-color image formation is performed, first, a black toner image is formed on the photosensitive drum by the black developing device 4K, and the black toner image is primarily transferred onto the intermediate transfer belt. Next, the rotating body 4A is rotated by 90 °, the yellow developing device 4Y is arranged at the developing position D, a yellow toner image is formed on the photosensitive drum, and the yellow toner image on the intermediate transfer belt is formed on the yellow toner image. The toner images are primarily transferred and superimposed.

  The above operation is sequentially performed in the magenta developing unit 4M and the cyan developing unit 4C to superimpose four color toner images on the intermediate transfer belt. Thereafter, by applying a secondary transfer bias to the secondary transfer roller 16, the four color toner images on the intermediate transfer belt are collectively collected on the recording material P carried and conveyed on the transfer conveyance belt 7. Secondary transfer.

  The recording material P onto which the toner image has been transferred is peeled off from the transfer conveyance belt 7 and is heated and pressed by the fixing roller 18 and the pressure roller 20 of the fixing device 8 to fix the toner image. As a result, a four-color full-color image is formed on the recording material. After the secondary transfer, toner (transfer residual toner) remaining on the intermediate transfer belt is removed by a belt cleaner 14 that cleans the intermediate transfer member.

  In the case of forming a single color image, the electrostatic latent image formed on the photosensitive drum is developed by a developing unit containing toner of a desired color to form a toner image. The toner image is primarily transferred onto the intermediate transfer belt and then immediately onto the recording material P. The recording material P onto which the toner image has been transferred is peeled off from the transfer conveyance belt 7 and heated and pressurized by the fixing device 8 to fix the toner image on the surface. On the other hand, the toner (transfer residual toner) remaining on the surface of the photosensitive drum after the primary transfer is removed by the cleaning device 6 and the cleaning blade 6a.

(Detection of toner passing through the cleaning blade)
FIG. 3 is a diagram illustrating a toner sensor that detects toner slipped from the cleaning blade 6a, and FIG. 4 is a block diagram illustrating a control unit and a toner detection unit of the image forming apparatus according to the present embodiment. As shown in FIG. 3, an optical toner sensor 21 serving as a toner detecting means for detecting toner is disposed downstream of the cleaning blade 6a on the photosensitive drum in the rotational direction of the photosensitive drum. The toner sensor 21 is disposed at a position where the toner that has passed through the cleaning blade on the photosensitive drum can be detected. In this embodiment, the toner sensor 21 is disposed downstream of the cleaning blade in the rotational direction of the photosensitive drum 1 and upstream of the charging roller. Has been. The toner sensor 21 may be a toner density detection sensor or a toner presence / absence detection sensor.

  In this embodiment, the cleaning blade 6a is disposed downstream of the primary charger 2 in the rotation direction of the photosensitive drum, but the toner sensor 21 is disposed downstream of the developing device in the rotation direction of the photosensitive drum. You may do it.

  Information about the slip-through toner detected by the toner sensor 21 is input to the CPU 100 which is a control unit. The CPU 100 determines a cleaning condition as will be described later based on the information regarding the slip-through toner output from the toner sensor. The CPU 100 also controls the toner pattern forming unit 101 which is a toner pattern forming unit that operates the primary charger 2, the exposure device 3, and the developing device 4 to form a toner pattern on the photosensitive drum, thereby forming a toner pattern. The timing and toner density of the toner pattern are determined.

(Cleaning performance of the cleaning blade)
FIG. 5 is a diagram illustrating the toner loading amount and the toner slipping start time of the cleaning blade. Various detection toner patterns with different amounts of applied toner are formed, supplied to the cleaning blade 6a, and then the toner slip-off start time when the toner begins to slip through the cleaning blade is set for each toner amount of toner pattern. The measurement results are shown.

In FIG. 5, the horizontal axis represents the weight of toner per unit area (hereinafter referred to as toner applied amount), and the vertical axis represents the time when cleaning failure (toner slipping) starts when cleaning is continued (passing start time ). When the cleaning blade continuously cleans a large amount of toner, the time when the toner slips from the blade starts depends on the amount of applied toner and the performance of the cleaning blade (such as the contact pressure of the cleaning blade).

  In the case where the toner with an untransferred toner applied amount of the image having the maximum toner amount per unit area B shown in the figure is continuously cleaned with a new blade (C), the toner is removed from the point when time b has elapsed. The slip-through starts. Similarly, when the toner of the amount of applied toner remaining after the transfer of the image having the maximum amount of toner per unit area A shown in the figure is continuously cleaned, toner slip-off starts from the point in time when time a elapses. In this embodiment, A is a toner amount per unit area of 0.050 mg / cm <2>, and B is 0.50 mg / cm <2>.

  In the blade cleaning method using a cleaning blade, the slip-through start time with respect to the toner loading amount tends to be a downwardly convex curve as shown in the figure. For the sake of explanation, the drawing is simplified, but the amount of applied toner to be cleaned by the blade at the time of image formation is small because it is transfer residual toner, and the slip-through start time becomes very long.

  The slip-through start time when the cleaning blade deteriorates due to durability will also be described. The dashed-dotted line (C) in FIG. 5 indicates the slip-through start time with respect to each applied toner amount when a new cleaning blade is used, and the alternate long and two short dashes line (D) indicates the toner loading when using a cleaning blade whose durability has deteriorated. The slip-through start time with respect to the quantity is shown. As can be seen from the drawing, the durability of the cleaning blade deteriorates, so that toner can slip through in a short time regardless of the amount of applied toner.

  The maximum applied toner amount A to be removed by the blade during image formation is a state in which transfer residual toner of an image (solid image) having the maximum applied toner amount is supplied to the entire longitudinal direction, which is the maximum image forming width. Further, the number of images (the number calculated from the time “a” in the figure) that continuously outputs an image with the maximum toner loading amount varies depending on the product life, specifications, and the like, and may be appropriately determined according to the product. Here, in the cleaning blade of this example, when the applied toner amount A was continuously supplied to a new cleaning blade, toner slipped out of the cleaning blade in 5000 seconds (through start time a ′). On the other hand, the slip-through start time a when the cleaning blade reached the end of its service life was shortened to 50 seconds. Further, when the applied toner amount B was continuously supplied to the cleaning blade, the slip-through start time b ′ during which the toner slips through the new cleaning blade (C) was 50 seconds. Further, the slip-through start time b of the cleaning blade (D) whose durability was deteriorated was 0.5 seconds.

  FIG. 6 is a diagram showing the toner loading amount and slip-through start time in the cleaning blade in a deteriorated state. Similar to FIG. 5, the toner applied amount B is 0.50 mg / cm 2 which is substantially the same as the maximum toner applied amount removed by the cleaning blade including during non-image formation.

  Here, as a case where the durability of the cleaning blade deteriorates, the cleaning performance deteriorates only when the applied toner amount is large (E), and the cleaning performance decreases only when the supplied toner amount is small (F). )

(E) Blade sag: When a cleaning blade made of a rubber material is used for a long time in a high temperature and high humidity environment, the rubber hardness decreases and the contact pressure decreases. As a result, the cleaning performance with a high toner loading is reduced, while the cleaning performance with a low toner loading may be good. (Solid line (E))

(F) Increase in friction coefficient of the blade and increase in torque of the photosensitive drum: The friction coefficient between the cleaning blade and the photosensitive drum is increased and slipperiness is decreased, so that the behavior of the cleaning blade becomes unstable. Although the cleaning performance at a low toner loading amount is lowered, after the high toner loading amount is supplied, the lubricity with the photosensitive drum is improved and the cleaning performance is improved. (Solid line (F))

  Here, in the deterioration detection of the cleaning performance by the toner pattern of one applied toner amount, it is impossible to detect the decrease in both the cleaning performances (E) and (F). For this reason, in the cases (E) and (F), the cleaning blade has reached the end of its life due to poor cleaning due to the occurrence of slipping toner. There is a limit to predicting various deterioration states of the cleaning blade with a toner pattern having a single applied toner amount. This will be described later.

(Cleaning performance detection mode to detect cleaning performance)
A cleaning performance detection mode for detecting the cleaning performance of the cleaning blade 6a in this embodiment will be described below.

  FIG. 8 is a flowchart showing the sequence control (cleaning performance detection mode) for detecting the cleaning performance of this embodiment.

  First, a toner pattern for detecting slip-through toner supplied to the cleaning blade 6a will be described. In the present embodiment, the first toner pattern having the toner amount A per unit area assuming the maximum transfer residual toner at the time of image formation and the maximum untransferred toner at the time of paper jam (JAM) are assumed. Two types of toner patterns of the second toner pattern having the toner amount B per unit area are successively formed by the toner pattern forming means. In both types of toner patterns, the amount of applied toner in the entire image area is uniform with respect to the main scanning direction (longitudinal direction), and in this embodiment, the maximum width of the image area is 330 mm.

  The deterioration state of the blade described above is estimated by detecting the start time of the slipping-through toner that passes through the blade in the two toner patterns. Here, when the information regarding the toner passing through detected by the toner sensor 21 exceeds a certain threshold value, it is determined that toner has passed. If the deterioration state of the blade is the above-described deterioration state (E), the second toner pattern slip-through toner start time is very short, and if the deterioration state is (F), the first toner pattern slip-through The toner start time is very short. Hereinafter, the cleaning performance detection mode will be described.

  In the post-rotation operation after the end of the image forming operation, the first and second toner patterns are successively formed on the photosensitive drum (S1). Further, it is executed at the time of a post-rotation operation after an image forming operation every predetermined number of sheets, that is, every 5000 sheets.

  At this time, the time for forming the first toner pattern was set to 100 seconds, which is twice the 50 seconds that is the slip-through start time a when the blade durability deteriorates. Further, the time for forming the second toner pattern is 10 seconds with a margin. However, the time for forming the toner pattern may be set to an appropriate value according to the acceptable slip-through start time of the product.

  Thereafter, whether (1) the first toner pattern and (2) the second toner pattern are cleaned is detected by the respective toner patterns to determine whether or not slip-through toner is generated within a predetermined period. (1) When the toner pattern of either of (2) is removed without passing through the toner pattern even when the toner pattern formation time has elapsed ((1): ○, (2): ○ ) (S2), since no deterioration of the blade is observed, after that, the operation returns to the normal operation and shifts to the standby (S3).

  On the other hand, when (1) the first toner pattern is cleaned well and (2) toner slip occurs in the second toner pattern ((1): ○, (2): ×) (S4), the blade It is thought that the sag of this has occurred. Therefore, the CPU changes the cleaning condition so that the idle rotation of the photosensitive drum, which is a paper jam recovery sequence, is made longer than the normal paper jam recovery sequence when there is a large amount of toner loaded on the blade. (S5). In the recovery sequence from a paper jam, in order to clean the residual toner remaining on the photosensitive drum that is generated when it is forcibly stopped due to a paper jam, the photosensitive drum is rotated one or more times for cleaning. In this embodiment, in the normal paper jam recovery sequence, the photosensitive drum 1 is idled twice, but in S5, it is idled 10 times to remove residual toner on the photosensitive drum. Instead of lengthening the idling rotation, the toner remaining on the intermediate transfer belt is reversely transferred to the photosensitive drum side in the primary transfer unit as a sequence at the time of paper jam recovery, and is collected by the cleaning device on the photosensitive drum side. The cleaning conditions may be changed.

  In addition, (2) the second toner pattern does not generate slip-through toner, and (1) the first toner pattern causes toner slip-through ((1): ×, (2): ○) (S6) In this case, it is considered that the friction coefficient of the cleaning blade and the torque of the photosensitive drum 1 are increased, which are degradation factors of the cleaning blade. Therefore, a toner band, which is a belt-like toner pattern, is formed and supplied to the cleaning blade, torque reduction is performed to restore the sliding property of the cleaning blade (S7), and then the first toner pattern is supplied again (S7). S8) It is confirmed whether slip-through toner is generated (S9). At this time, when the slip-through toner does not occur, the process proceeds to standby.

  Further, when the toner patterns of (1) and (2) are removed by the cleaning blade and toner passes through both toner patterns ((1): ×, (2): ×) (S10) The cleaning performance of the cleaning blade is approaching the life limit. Therefore, the life warning of the cleaning blade 6a is given (S11). By setting in this way, it becomes possible to detect the cleaning performance by the cleaning blade 6a before an image defect due to toner passing through, and the cleaning condition is determined according to the deterioration state of the cleaning blade 6a, or the cleaning is performed. The blade life can be warned.

  FIG. 7 is a timing chart of the cleaning performance detection mode for detecting the cleaning performance in this embodiment. In the detection toner pattern for detecting slip-through toner, the CPU 100 controls the amount of applied toner and the time for forming the toner pattern by changing the image exposure level and exposure time of the exposure means. Regarding the amount of applied toner, the charging bias voltage and the developing bias voltage may be adjusted.

  When the cleaning performance detection mode is started during the post-rotation operation after the completion of image formation, the charging bias voltage, exposure, and development bias voltage are switched from OFF to ON almost simultaneously to form the first toner pattern. After the formation of the first toner pattern, the charging bias voltage, exposure, and development bias voltage are once turned off. Thereafter, the charging bias voltage, exposure, and development bias voltage are switched from OFF to ON again to form a second toner pattern. At this time, the toner sensor is turned on to detect slip-through toner. Further, the transfer bias voltage is kept off. The first toner pattern and the second toner pattern having a larger amount of toner per unit area than the first toner pattern are continuously formed by the toner pattern forming means. Thereafter, toner that has passed through the cleaning blade in each toner pattern is detected by a toner sensor that is a toner detection unit, and the cleaning condition is determined as described above based on the information related to the detected toner amount.

  Note that the cleaning performance may be detected by forming not only the first and second toner patterns but also third and fourth toner patterns having different toner loading amounts.

  Further, although the photosensitive drum blade for cleaning the photosensitive drum has been described, the present invention may be applied to an intermediate transfer member cleaning blade for cleaning the intermediate transfer member, a cleaning blade for cleaning the photosensitive belt, and the like.

Further, the first and second toner patterns are not limited to the maximum amount of toner remaining after transfer during image formation and the maximum amount of toner applied remaining on the image carrier during jamming. What is necessary is just to set suitably, such as a toner applied amount, according to an image forming apparatus.
[Example 2]
In the first embodiment, an optical density detection sensor is used as a means for detecting toner that cannot be cleaned from the cleaning blade 6a. In this embodiment, the charging bias voltage applied by the power source 23 is detected. Detecting toner that has passed through. In other words, in this embodiment, the current-voltage characteristic applied to the charging roller, which is a conductive member disposed downstream in the rotation direction of the cleaning blade 6a, is detected by the current detector 22, which is a charging current detection means, thereby cleaning the cleaning blade. The presence or absence of toner on the photosensitive drum 6a downstream can be detected. With this configuration, even if the toner that has passed through the cleaning blade 6a has a variation in the longitudinal direction, the configuration is complicated and the cost is increased by detecting the entire region by arranging a plurality of sensors that detect the entire longitudinal region. Can be prevented.

  FIG. 9 shows an image forming apparatus according to this embodiment. The image forming apparatus is configured by using a primary charger using a contact-type charging roller system. The charging to the photosensitive drum by the charging roller method is performed by applying a high voltage to a minute gap region formed between the elastic roller 2 and the photosensitive drum. If toner remains on the photosensitive drum, high-resistance particles are sandwiched between the charging roller and the photosensitive member, so that the impedance changes and the voltage-current characteristic applied to the charging roller 2 changes.

  In this embodiment, charging is performed by applying a charging voltage obtained by superimposing an AC voltage on a DC voltage. If toner remains on the photosensitive drum, the current hardly flows and the amount of AC current decreases. In order to use this characteristic, the voltage-current characteristic to the charging roller 2 is first detected when the detection toner pattern for detecting the cleaning performance is not formed. Thereafter, first and second toner patterns are formed, and it is detected whether toner has passed through a change in voltage-current characteristics of the charging roller 2 after a predetermined time has elapsed. That is, since the voltage-current characteristic changes when the toner slips through, the amount of current flowing through the charging roller changes, but does not change unless the toner slips through. Here, the voltage applied to the charging roller is an AC voltage value (peak to peak) of 2 kV and a DC voltage value of 500 V. At this time, the AC effective current value is detected. In this embodiment, it was 1.5 mA when the slip-through toner was generated, but 1.6 mA when the slip-through was not generated. This is because the high resistance toner is sandwiched between the charging roller and the photosensitive member, and the apparent resistance value is increased. The resistance variation of the charging roller and the photosensitive member can be distinguished by performing a JAM return sequence to reduce the amount of slipping toner, and then forming a toner pattern and measuring the current in the slipping state.

  With this configuration, it is possible to detect the toner slipping state in the entire longitudinal direction without requiring a toner density detection sensor for slipping toner.

  In this embodiment, the cleaning blade that contacts the photosensitive member has been described. However, the present invention is not limited to this, and a cleaning blade that contacts the intermediate transfer belt or the photosensitive belt may be used.

1 Photosensitive drum (image carrier)
2 Primary charger 3 Exposure device 4 Development device 5 Intermediate transfer belt (intermediate transfer member)
6 Cleaning means 6a Cleaning blade 7 Transfer conveying belt 8 Fixing device 11 Primary transfer roller 16 Secondary transfer roller 21 Toner sensor (toner detection unit)
100 CPU (control unit)
101 Toner pattern forming unit (toner pattern forming means)

Claims (7)

In an image forming apparatus comprising: an image carrier that carries a toner image; a toner pattern forming unit that forms a detection toner pattern on the image carrier; and a blade that removes toner remaining on the image carrier.
A detecting unit that is disposed downstream of the blade in the rotation direction of the image carrier and detects information on the amount of toner on the image carrier that has passed through the blade;
The toner pattern forming means continuously forms a first toner pattern and a second toner pattern having a larger amount of toner per unit area than the first toner pattern, and the first and second toners An image forming apparatus comprising: a control unit that controls to determine a cleaning condition of the image carrier based on information on the toner amount detected by the detection unit by passing through the blade in a pattern.   The image forming apparatus according to claim 1, wherein the image carrier is an intermediate transfer member that transfers a toner image to a recording material.   The image forming apparatus according to claim 1, wherein the second toner pattern is substantially the same as an untransferred toner amount of an image having a maximum toner amount per unit area.   4. The image formation according to claim 1, wherein the first toner pattern is substantially the same as a residual toner amount of an image having a maximum toner amount per unit area. 5. apparatus.   The toner band is supplied to the blade when the information regarding the toner amount detected by the detecting unit in the first toner pattern exceeds a threshold as the cleaning condition. 2. The image forming apparatus according to item 1.   The image forming apparatus according to claim 1, wherein the detection unit is a charging current detection unit that detects a charging current applied to a charging unit that charges the image carrier. . As the cleaning condition, the idling of the image carrier when returning from a paper jam is longer than when the information regarding the toner amount detected by the detection unit in the second toner pattern does not exceed the threshold. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.

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