JP2019045650A - Mage formation device - Google Patents

Abstract

To suppress a lubrication property of toner between a photosensitive drum and a cleaning blade from falling due to deterioration of the toner in a configuration for recovering the remaining toner by abutting the cleaning blade on the photosensitive drum.SOLUTION: An image formation device comprises: a development device 4 that includes an image carrier 1, and a developer carrier 4a; a cleaning member 6a that contacts with the image carrier 1; an intermediate transfer body 7 that is rotatable for transferring a developer image transferred from the image carrier 1 to a recording material P; a contact member 11 that is configured contactable with the intermediate transfer body 7 at a contact part; a power source 12 that applies a voltage to the contact member 11; and a control unit 10 that executes a supply action for supplying the developer image transferred to the intermediate transfer body 7 from the image carrier 1, and passing through the contact part to the image carrier 1. The supply action is executed upon non-image formation. In the supply action, an amount of charging of the developer image on a downstream side of the contact part is different from that thereof in an upstream side thereof.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electrophotographic or electrostatic recording image forming apparatus.

  In an image forming apparatus using electrophotography technology, a developer image (toner image) is formed on an image carrier (photosensitive drum) by a developing device containing a developer (toner). An image is formed on the recording material by transferring the formed toner image to the recording material. Here, after the toner image on the photosensitive drum is transferred to the recording material, toner may remain on the photosensitive drum. Therefore, a cleaning member (cleaning blade) is provided to remove the toner remaining on the photosensitive drum.

  Here, if the coefficient of friction of the surface of the photosensitive drum increases, the cleaning by the cleaning blade may be insufficient. In addition, abnormal noise may occur due to rubbing between the cleaning blade and the photosensitive drum.

  Therefore, there is a configuration in which the toner is supplied to the portion where the cleaning blade and the photosensitive drum are in contact with each other (Japanese Patent Application Laid-Open No. 2001-147118). In this configuration, the image forming apparatus has four process cartridges, and supplies toner of good colorability to a cleaning blade provided on the process cartridge. Specifically, the image forming apparatus supplies toner having a good lubricity to a cleaning blade provided in another process cartridge from a process cartridge in which toner having a good lubricity is stored. There is. There is a configuration in which the image forming apparatus supplies toner from a process cartridge having a large amount of stored toner to a cleaning blade provided in the process cartridge having a small amount of stored toner (Japanese Patent Application Laid-Open No. 2000-112118).

Unexamined-Japanese-Patent No. 11-194690 JP, 2011-150304, A

  The toner is configured by adding an external additive which is inorganic fine particles such as a lubricant and a charge control agent to resin particles containing the charge control agent and the pigment. The external additive may be embedded in the resin particles due to the friction between the toner and other parts. This phenomenon is called so-called toner deterioration. When the toner is deteriorated, the amount of toner supplied to the portion where the cleaning blade and the photosensitive drum contact may be insufficient. In addition, even if toner is supplied to the portion where the cleaning blade and the photosensitive drum are in contact with each other, the friction between the cleaning blade and the photosensitive drum may not be sufficiently reduced.

  In order to solve the above-mentioned subject, one of the present inventions are as follows.

An image forming unit,
An image carrier that carries an electrostatic latent image;
A developing device for developing the electrostatic latent image, the developing device comprising a developer carrier for carrying a developer and forming a developer image on the image carrier;
A cleaning member in contact with the image carrier;
An image forming unit comprising
A rotatable intermediate transfer member for transferring the developer image transferred from the image carrier at a primary transfer portion to a recording material at a secondary transfer portion;
A contact member configured to be able to contact the intermediate transfer member at the contact portion, wherein the contact is disposed downstream of the secondary transfer portion and upstream of the primary transfer portion in the rotational direction of the intermediate transfer member. Members,
A power supply for applying a voltage to the contact member;
Control for performing a supply operation of supplying the developer image transferred from the image carrier to the intermediate transfer member and passed through the contact portion from the intermediate transfer member between the image carrier and the cleaning member A control unit that executes the supply operation when an image forming operation for transferring the developer image to the recording material is not performed;
Equipped with
The charge amount per unit mass of the developer image after passing through the contact portion in the supply operation is regarded as the downstream charge amount, and the charge amount per unit mass of the developer image before passing through the contact portion An image forming apparatus characterized in that the power supply applies a voltage to the contact member such that the downstream charge amount and the upstream charge amount are different.

  According to the present invention, even when degraded toner is used, developer (toner) can be supplied to the portion where the cleaning member (cleaning blade) and the image carrier (photosensitive drum) are in contact. It is possible to suppress the decrease in lubricity at the portion where the cleaning member (cleaning blade) and the image carrier (photosensitive drum) are in contact.

Schematic explanatory view of the image forming apparatus main body Illustration of lubricating layer Flow chart of the first feeding operation Schematic explanatory drawing of a lubricating layer based on Example 1 Explanatory drawing of cleaning examination based on Example 1 Schematic explanatory view of toner deterioration according to the first embodiment Explanatory drawing of cleaning examination based on Example 2 Explanatory drawing of the toner supply operation frequency based on Example 2 Illustration of toner supply operation via the intermediate transfer belt and the intermediate transfer brush

  Embodiments of the present invention will be illustrated below with reference to the drawings. However, the dimensions, materials and shapes of the component parts described in the embodiment, their relative positions and the like should be suitably changed according to the configuration of the apparatus to which the invention is applied and various conditions, etc. The scope of the present invention is not intended to be limited to the following embodiments.

  The image forming operation of the image forming apparatus S according to the first embodiment will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view of the image forming apparatus according to the first embodiment.

  The image forming apparatus S includes an apparatus main body 100 of the image forming apparatus S, and process cartridges Cy, Cm, Cc, and Ck as an image forming unit. That is, the image forming apparatus S has a plurality of process cartridges C. The process cartridge uses a toner as a developer to transfer a toner image as a developer image to an intermediate transfer belt described later. Then, the toner image transferred to the intermediate transfer belt is transferred to the recording material P.

  The process cartridge Cy forms a yellow toner image. The process cartridge Cm forms a toner image of magenta. The process cartridge Cc forms a cyan toner image. The process cartridge Ck forms a black toner image.

  The apparatus main body 100 is provided with a station on which a process cartridge is mounted and which forms a toner image on an intermediate transfer member described later. A station where the process cartridge Cy is mounted is referred to as a first station. A station where the process cartridge Cm is mounted is referred to as a second station. A station where the process cartridge Cc is mounted is referred to as a third station. A station where the process cartridge Ck is mounted is referred to as a fourth station.

  In the present embodiment, the process cartridges Cy to Ck have the same configuration except for the color of the stored toner. In principle, in the following description, the same parts in the process cartridges Cy to Ck will be collectively described by omitting the suffixes y to k.

  The configurations of the process cartridges do not have to be completely identical. For example, the size of the black process cartridge may be larger than the size of other process cartridges.

  Further, in the present embodiment, the process cartridge, which is an image forming unit, is attachable to and detachable from the apparatus main body 100 of the image forming apparatus, but is not limited thereto.

  Further, in the present embodiment, the process cartridge integrally includes a photosensitive drum, a developing device described later, and a cleaning device. However, the photosensitive drum, the developing device, and the cleaning device may be separately detachable from the apparatus main body 100. Further, all or part of the photosensitive drum, the developing device, and the cleaning device may be fixed to the apparatus main body 100. Further, the photosensitive cartridge including the photosensitive drum and the cleaning device, and the developing cartridge including the developing device may be configured to be removable from the apparatus main body 100.

(Process cartridge)
The process cartridge Cy will be described using the process cartridge Cy at the first station. In the following description, the suffix y is omitted. For example, the process cartridge Cy is referred to as a process cartridge C. Similarly, the members of the process cartridge C and the members on the side of the apparatus main body 100 corresponding thereto are omitted from the suffix y.

  As shown in FIG. 1, the process cartridge C includes a photosensitive drum 1 as an image carrier, a charging roller 2 as a charging member, a developing device 4, and a cleaning device 6. An electrostatic latent image is formed on the photosensitive drum 1. The photosensitive drum 1 carries an electrostatic latent image.

  The photosensitive drum 1 rotates in the direction of arrow R1 in FIG. The photosensitive drum 1 is uniformly charged to a predetermined potential by a charging roller 2 which is driven to rotate while being in contact with the photosensitive drum 1.

  On the other hand, the cleaning device 6 for collecting the residual toner on the surface of the photosensitive drum 1 includes a cleaning blade 6 a as a cleaning member in contact with the photosensitive drum 1. The cleaning blade 6a includes an elastic portion formed of urethane rubber. The cleaning blade 6a is fixed to the cleaning frame of the cleaning device 6 so that the elastic portion abuts the photosensitive drum 1y in the counter direction with respect to the rotational direction of the photosensitive drum 1y.

  The developing device 4 contains toner T as a developer. The toner of this embodiment is a negatively chargeable nonmagnetic one-component toner. The toner is composed of a base made of resin particles and the like, and an external additive made of inorganic fine particles such as silica.

  Further, the developing device 4y has a developing roller 4a as a rotatable developer carrier. The developing roller 4a carries toner. The developing roller 4 a supplies toner to the electrostatic latent image formed on the photosensitive drum 1 to visualize the electrostatic latent image and forms a toner image on the photosensitive drum 1. The developing device 4 has a developing blade 4b in contact with the developing roller 4a in order to apply an electric charge to the toner carried on the surface of the developing roller 4a. The developing blade 4 b is a layer thickness regulating member that regulates the thickness of the toner carried on the surface of the developing roller 4 a. A sealing sheet 4c is provided on the downstream side of the portion of the photosensitive drum 1 on which the toner image is formed in the rotational direction of the developing roller 4a.

  The developer of this embodiment is a non-magnetic one-component toner, but is not limited thereto. For example, as a developer, a magnetic one-component developer or a two-component developer in which a toner and a carrier are mixed can be used.

  Further, in this embodiment, an OPC (organic photosensitive member) drum having a negative charge characteristic of 30 mm in diameter is used as the photosensitive drum 1 (1y to 1k). At the time of image formation, the surface of the photosensitive drum 1 is rotated at 100 mm / sec in the direction of the arrow R1 in FIG. 1 by a drive source (not shown).

  The surface speed (circumferential speed) of the developing roller 4 a is 1.4 times (140%) the surface speed (circumferential speed) of the photosensitive drum 1. In the developing portion where the electrostatic latent image on the photosensitive drum 1 is developed by the developing roller 4a, the direction in which the surface of the developing roller 4a rotates and the direction in which the surface of the photosensitive drum 1 rotates are the same.

  Further, a storage device 6 b (memory) for storing information on the use history of the process cartridge C is provided in the cleaning device 6. A control unit (CPU) 10 provided in the apparatus main body 100 of the image forming apparatus writes information in the storage device 6 b and refers to the information stored in the storage device 6 b.

(Apparatus body 100 of the image forming apparatus)
The apparatus main body 100 of the image forming apparatus will be described.

  The apparatus main body 100 includes a scanner 3 as an exposure apparatus that exposes the photosensitive drums 1 of the process cartridges. The photosensitive drum 1 is exposed by the laser beam L emitted from the scanner 3. Then, an electrostatic latent image is formed on the surface of the photosensitive drum 1. Then, when the developing roller 4 a abuts on the photosensitive drum 1 at a desired timing, toner is supplied to the surface of the photosensitive drum 1. As a result, the electrostatic latent image on the surface of the photosensitive drum 1 is visualized, and a toner image as a developer image is formed on the surface of the photosensitive drum 1y. The development of the electrostatic latent image is also referred to as development of the electrostatic latent image and visualization of the electrostatic latent image. Note that as the exposure device, a configuration may be used in which the photosensitive drum 1 is exposed by a plurality of light emitting diodes (LEDs).

  The apparatus main body 100 includes an intermediate transfer belt 7 as an intermediate transfer member. Intermediate transfer belt 7 is rotatable in the direction of arrow R2 in FIG. The intermediate transfer belt 7 transfers the toner image transferred from the photosensitive drum 1 at the primary transfer portion to the recording material P at the secondary transfer portion.

  Inside the intermediate transfer belt 7, primary transfer rollers 5 (5y to 5k) as primary transfer members are disposed. The number of primary transfer rollers 5 is plural. One primary transfer roller 5 (5y to 5k) is provided for each photosensitive drum 1 (1y to 1k). The primary transfer roller 5 faces the photosensitive drum 1 via the intermediate transfer belt 7. That is, the primary transfer roller 5 and the photosensitive drum 1 are disposed such that the intermediate transfer belt 7 is sandwiched between the primary transfer roller 5 and the photosensitive drum 1. The toner image on the surface of the photosensitive drum 1 is transferred to the intermediate transfer belt 7 in a region sandwiched between the photosensitive drum 1 and the primary transfer roller 5. This area is called a primary transfer portion. In the present embodiment, since the number of photosensitive drums is plural, the number of primary transfer portions is also plural.

  A secondary transfer roller 18 as a secondary transfer member is disposed outside the intermediate transfer belt 7. Inside the intermediate transfer belt 7, a secondary transfer opposing roller 8 as a secondary transfer opposing member is disposed to face the secondary transfer roller 18. The secondary transfer roller 18 faces the secondary transfer facing roller 8 via the intermediate transfer belt 7. That is, the secondary transfer roller 18 and the secondary transfer opposing roller 8 are disposed such that the intermediate transfer belt 7 is sandwiched between the secondary transfer roller 18 and the secondary transfer opposing roller 8. The toner image on the surface of the intermediate transfer belt 7 is transferred to the recording material P in a region between the secondary transfer roller 18 and the secondary transfer opposing roller 8. This area is called a secondary transfer portion.

  The apparatus main body 100 includes an intermediate transfer brush 11 as a contact member capable of contacting the toner image on the surface of the intermediate transfer belt 7. The intermediate transfer brush 11 can contact the intermediate transfer belt 7. The intermediate transfer brush 11 contacts the toner on the surface of the intermediate transfer belt 7 to change the charge amount of the toner. The portion at which the intermediate transfer belt 7 contacts the intermediate transfer brush 11 is called a contact portion. The intermediate transfer brush 11 is disposed downstream of the secondary transfer portion and upstream of the primary transfer portion (the primary transfer portion positioned most upstream) in the rotational direction R2.

  The device body 100 includes a power supply 12. In the present embodiment, the power source 12 is connected to the primary transfer roller 5, the secondary transfer roller 18, the intermediate transfer brush 11, the developing roller 4 a, and the charging roller 2. The power supply 12 applies a voltage to the primary transfer roller 5, the secondary transfer roller 18, the intermediate transfer brush 11, the developing roller 4 a, and the charging roller 2. The power supply 12 may be connected to a member other than the above-described members to apply a voltage. Also, the power supply 12 connected to at least one member and the power supply 12 connected to the other members may be different. That is, the power source 12 may be plural.

  The device body 100 includes a control unit 10. The control unit 10 performs a toner supply operation not via the intermediate transfer belt 7 and the intermediate transfer brush 11 described later, and a toner supply operation via the intermediate transfer belt 7 and the intermediate transfer brush 11. In the present embodiment, the control unit 10 performs an image forming operation on a recording material to be described later. The control unit 10 controls the operation of each component such as a drive source for transferring power to the process cartridge, the above-described power supplies, and the exposure apparatus. Control part 10 may control members other than the above-mentioned member. Also, the control unit need not be one. The control unit that controls at least one member and the control unit that controls the other members may be different.

  The apparatus main body 100 includes a fixing device provided with a fixing roller 9 for fixing a toner image on the recording material P.

(Image formation operation to recording material)
The image forming operation on the recording material will be described.

  The surface of the photosensitive drum 1 is negatively charged by the charging roller 2 to which a negative voltage is applied. Then, the surface of the photosensitive drum 1 is exposed by the laser light by the scanner 3. In the present embodiment, the surface potential of the photosensitive drum 1 charged by the charging roller 2 is approximately −500 V (dark area potential). The surface potential of the portion exposed by the scanner 3 is approximately -100 V (bright portion potential).

  On the surface of the developing roller 4a, a toner (toner layer) which is charged to the negative polarity and whose thickness is regulated by the developing blade 4b is carried. Further, a DC voltage of approximately -300 V is applied to the developing roller 4a as a developing voltage (developing bias).

  As described above, the polarity of the charge amount of the toner on the surface of the developing roller 4a is negative. When the developing roller 4a comes in contact with the photosensitive drum 1, the toner on the surface of the developing roller 4a moves to a portion having a bright portion potential. Then, a toner image is formed on the surface of the photosensitive drum 1.

  A voltage of positive polarity is applied to the primary transfer roller 5 as a primary transfer voltage. In this embodiment, a DC voltage of +300 V is applied. Then, the toner image on the surface of the photosensitive drum 1 is primarily transferred from the photosensitive drum 1 to the surface of the intermediate transfer belt 7. The toner image transferred from the photosensitive drum 1 to the surface of the intermediate transfer belt 7 is conveyed from the primary transfer portion in the direction of the arrow R2.

  On the other hand, residual toner (primary residual toner) remaining on the surface of the photosensitive drum 1 without being transferred to the intermediate transfer belt 7 in the primary transfer portion is removed by the cleaning blade 6a. At this time, part of the primary residual toner remains at the contact portion between the photosensitive drum 1 and the cleaning blade 6a, and forms a lubricant layer described later. The remaining primary residual toner is collected in the residual toner storage unit provided in the cleaning device 6.

  The process cartridges Cm to Ck similarly form toner images. The toner images formed by the process cartridges Cy to Ck overlap each other and are transferred to the surface of the intermediate transfer belt 7.

  Before the toner image transferred to the intermediate transfer belt 7 reaches the secondary transfer portion, the recording material P is transported to the secondary transfer portion by a transport device (not shown). Then, a voltage of positive polarity is applied to the secondary transfer roller 18 as a secondary transfer voltage. Thus, the toner image transferred to the surface of the intermediate transfer belt 7 is transferred to the recording material P.

  That is, the intermediate transfer belt 7 receives the toner image formed on the photosensitive drum 1 and transfers the received toner image onto a recording material P such as paper. The toner image received by the intermediate transfer belt 7 is transferred to the recording material P at the secondary transfer portion.

  In this embodiment, although a voltage of positive polarity is applied to the secondary transfer roller 18, a voltage of negative polarity is applied to the secondary transfer opposing roller 8 provided inside the intermediate transfer belt 7. May be

  The recording material P on which the toner image has been transferred is heated by the fixing roller 9. Thereby, the toner image is fixed on the recording material P.

  In this embodiment, a primary transfer roller is used as a primary transfer member. However, the present invention is not limited to this. The secondary transfer roller or the secondary transfer opposite roller may be configured to apply a potential to the intermediate transfer belt so that the developer image can be primarily transferred to the intermediate transfer belt. In this case, the primary transfer roller can be omitted. Also in this case, the portion to which the toner image is transferred from the photosensitive drum 1 to the intermediate transfer belt 7 is a primary transfer portion.

(Cleaning of the intermediate transfer belt)
After the toner image is transferred from the intermediate transfer belt to the recording material P, toner may remain on the surface of the intermediate transfer belt 7 as residual toner (secondary residual toner). For the purpose of cleaning secondary residual toner on the surface of the intermediate transfer belt 7, a cleaning member is provided downstream of the rotational direction of the portion of the intermediate transfer member where the secondary transfer member abuts.

  In this embodiment, a brush-like member or a roller-like member is brought into contact with the intermediate transfer belt as a contact member to apply a voltage (bias is applied). Then, the secondary residual toner is eliminated, or the charge of the secondary residual toner is controlled to be a desired charge. Then, part of the secondary residual toner is temporarily stored in the contact member. The other secondary residual toner is electrically recovered to the photosensitive drum. Thereby, the residual toner on the intermediate transfer member is cleaned.

  As shown in FIG. 1, the intermediate transfer brush 11 is in contact with the downstream side of the secondary transfer portion in the rotational direction R2. After the charge of the secondary residual toner is controlled by the intermediate transfer brush 11, the intermediate transfer belt 7 is returned to the photosensitive drum 1 at the primary transfer portion. The returned secondary residual toner is supplied between the photosensitive drum 1 and the cleaning blade 6a and cleaned by the cleaning blade 6a.

  A method of cleaning the intermediate transfer belt 7 during image formation on the recording material P will be described. In the secondary transfer portion, the secondary residual toner remaining on the intermediate transfer belt without being transferred to the recording material P contains a large amount of positively charged toner. That is, the polarity of the charge amount per unit mass of the secondary residual toner is positive.

  On the other hand, a positive voltage is applied to the intermediate transfer brush 11. As a result, among the secondary residual toner, toner charged to the negative polarity is stored in the intermediate transfer brush 11 at the contact portion between the intermediate transfer brush 11 and the intermediate transfer belt 7. On the other hand, the toner charged to the positive polarity passes through the contact portion and goes to the primary transfer portion.

  During the image forming operation, a voltage of positive polarity is applied to the primary transfer roller 5 in order to form a toner image on the intermediate transfer belt 7. When the secondary residual toner having a positive charge reaches this portion, the secondary residual toner moves from the intermediate transfer belt 7 to the photosensitive drum 1. Then, the returned secondary residual toner is cleaned by the cleaning member 6a together with the primary residual toner.

  In addition, the voltage of each member mentioned above and the polarity of an electric charge are only an example. The polarity of the voltage applied to each member is appropriately set according to the polarity of the toner forming the toner image.

(Toner supply to cleaning blade)
The operation of supplying the toner to the cleaning blade 6a when the image forming operation is not performed will be described. In this embodiment, the operation of supplying the toner to the cleaning blade 6a is called the toner supply operation separately from the image forming operation.

  As described above, also in the image forming operation, toner is supplied between the cleaning blade 6 a and the photosensitive drum 1. In the present embodiment, the toner supply operation is performed during a period in which the image forming operation is not performed (during non-image forming), separately from the above-described image forming operation. Thereby, the frictional force between the cleaning blade 6 a and the photosensitive drum 1 can be further reduced.

  In this embodiment, the timing at which the toner supply operation is performed is determined by the movement distance a of the surface of the photosensitive drum 1 in the circumferential direction of the photosensitive drum 1. Here, specifically, the movement distance a of the surface of the photosensitive drum 1 is the distance by which a specific position on the outer peripheral surface of the photosensitive drum 1 has moved in the circumferential direction of the photosensitive drum 1. The moving distance of the surface of the photosensitive drum 1 is also called traveling distance. When the integrated value of the movement distance a reaches a predetermined threshold (supply operation threshold), the toner supply operation is performed. When the toner supply operation is performed, the integrated value of the moving distance a is reset or decreased, and the integration is started again.

  The toner supply operation at the time of non-image formation is performed within a predetermined period after the image formation operation is completed. After the image forming operation is completed, the photosensitive drum 1 is rotated by continuously driving the main motor for a predetermined period (post-rotation operation). The toner supply operation is performed in this period.

(Toner supply operation not via the intermediate transfer belt)
The toner supply operation without the intermediary transfer belt 7 and the intermediary transfer brush 11 will be described. In order to distinguish between the intermediate transfer belt 7 and the toner supply operation via the intermediate transfer brush 11 described later, the toner supply operation not via the intermediate transfer belt 7 and the intermediate transfer brush 11 is referred to as a second supply operation. The toner supply operation via the intermediate transfer belt 7 and the intermediate transfer brush 11, which will be described later, is referred to as a first supply operation.

  In the second supply operation, as in the image forming operation, a toner image is formed on the surface of the photosensitive drum 1. In the present embodiment, the toner image at this time is an image uniformly formed on the surface of the photosensitive drum 1, that is, a so-called solid image. Then, the toner image is supplied to the cleaning blade 6a of the process cartridge C on which the solid image is formed.

  In the second toner supply operation, it is necessary to prevent the toner image on the photosensitive drum 1 from being transferred to the surface of the intermediate transfer belt 7. Therefore, when performing the second toner supply operation, the primary transfer portion is separated from the photosensitive drum. As another method, a negative voltage may be applied to the primary transfer member in a state where the primary transfer portion and the photosensitive drum 1 are in contact with each other. That is, a voltage having a polarity opposite to that of the voltage applied to the primary transfer rollers (5y to 5k) at the time of image formation may be applied to the primary transfer roller. Thus, the toner image formed on the surface of the photosensitive drum 1 is supplied to the cleaning blade 6 a without being transferred to the intermediate transfer belt 7.

  Here, the method of supplying the toner from the developing device 4 (developing roller 4a) directly to the photosensitive drum 1 without the intermediary transfer belt 7 has been described.

  Another toner supply method is as follows. The toner (toner image) is supplied from the developing device 4 to the photosensitive drum 1 in the process cartridge positioned on the upstream side in the rotational direction R2 of the intermediate transfer belt 7. Then, the image is transferred to the intermediate transfer belt 7 at the primary transfer portion. Then, in the process cartridge positioned downstream, a voltage reverse to that in the image forming operation may be applied to the primary transfer portion to supply the toner to the photosensitive drum 1. That is, the toner image may be supplied to the photosensitive drum 1 on the upstream side of the secondary transfer portion.

(Toner supply operation and lubricity)
The lubricity of the toner will be described with reference to FIG. FIG. 2A is a schematic cross-sectional view of a portion where the photosensitive drum 1 and the cleaning blade 6a abut. FIG. 2B is an enlarged view of a contact surface (a broken line portion) of the cleaning blade 6a and the photosensitive drum 1 in FIG. 2A. In FIG. 2A, the cleaning blade 6a is in contact with the photosensitive drum 1 in the counter direction with respect to the rotational direction (arrow).

  When the toner on the photosensitive drum 1 is cleaned, the toner and the external additive are scraped off in the vicinity of the cleaning blade 6a and the contact surface formed by the photosensitive drum 1 and the cleaning blade 6a. As a result, the toner stagnates in the vicinity of the cleaning blade 6a. A part of the toner is collected as waste toner into the collection container of the cleaning device 6. Other toners stay at the interface between the cleaning blade 6 a and the photosensitive drum 1. The toner accumulated at the interface between the cleaning blade 6 a and the photosensitive drum 1 exhibits an effect (a lubricating effect) of improving the lubricity between the cleaning blade 6 a and the photosensitive drum 1. In addition, when the stagnation state in which the lubricating effect is exhibited is observed along the axial direction of the photosensitive drum 1, the stagnant toner is often in a wedge shape as shown in FIG. In the present embodiment, the toner staying like a wedge is referred to as a lubricating layer.

  In the toner, an external additive which is inorganic fine particles such as a lubricant and a charge control agent is added to resin particles containing the charge control agent and the pigment. The main components of the lubricating layer 203 are external additive components. When the lubricating layer 203 is formed, the lubricity between the photosensitive drum 1 and the cleaning blade 6a is improved. Further, the lubricating layer 203 prevents the toner from invading the contact surface of the photosensitive drum 1 and the cleaning blade 6a, and assists the cleaning performance.

  The lubricating layer is easily formed by primary residual toner in primary transfer in an image forming operation. However, when the amount of primary residual toner is small or when a factor for reducing the external additive occurs, the lubricating layer decreases. The lubricating layer may disappear.

  Therefore, when the amount of primary residual toner is small, the toner and external additive forming the lubricating layer are supplied by performing the above-described second toner supply operation to compensate for the decrease in the lubricating layer and maintain the formation of the lubricating layer. Do.

(Effect of toner deterioration)
In the toner, an external additive which is inorganic fine particles such as a lubricant and a charge control agent is added to resin particles containing the charge control agent and the pigment. The external additive may be embedded in the resin particles due to the rubbing between the developing blade 4 b and the toner. This phenomenon is called toner deterioration. When the toner is not deteriorated, the lubricity of the toner is maintained. However, when the toner is deteriorated, the lubricity of the toner is reduced. If the lubricity of the toner is lowered, even if toner is supplied between the cleaning blade 6 a and the photosensitive drum 1, the friction generated between the cleaning blade 6 a and the photosensitive drum 1 may not be sufficiently suppressed.

  By performing the image formation, the toner in the process cartridge is changed. In particular, the change due to the toner rubbing between the developing blade 4 b and the developing roller 4 a is large. Further, as the main changes in toner state (hereinafter referred to simply as toner changes), fine particles such as an external additive fall off the toner main body, and fine particles such as an external additive are buried in the toner main body Can be mentioned. As a change in physical properties when such a change occurs, the charge amount of the toner may change and become large. This causes an increase in the cohesion of toners.

  As described above, the rubbing between the developing blade 4 b and the developing roller 4 a is a major factor causing the change of toner. Therefore, the number of revolutions of the developing roller 4a (the cumulative number of revolutions after the start of use of the process cartridge C) is one of the indicators of the change of the toner. However, the change of toner also depends on the amount of toner in the developing container of the developing device. This is because the opportunity for the toner to be rubbed varies depending on the amount of toner in the developing container. That is, the change in toner is affected by the cumulative number of revolutions of the developing roller 4a and the amount of toner. FIG. 6 is a schematic view of the change of toner, the number of revolutions (cumulative number of revolutions) of the developing roller 4a, and the amount of toner. In FIG. 6, in the area 1, the number of revolutions of the developing roller 4a is small and the amount of toner is large. In Region 1, the change in toner is relatively minor. Conversely, in the region 4, the number of rotations of the developing roller 4a is large, and the amount of toner is also small. Therefore, the change in toner is very large. Region 2 and region 3 are in the same state as the change of the toner although the rotation number and the toner amount of the developing roller 4a are different. The toner change described above is generally referred to as toner deterioration.

  It has been found that when toner is directly supplied from the developing device 4 between the photosensitive drum 1 and the cleaning blade 6a, formation of the lubricating layer may become unstable due to toner deterioration. Specifically, the toner deterioration changes the charging performance of the toner, resulting in an increase in the charge amount of the toner and an increase in the aggregation property of the toner. The adhesion to the photosensitive drum 1 is increased by the increase of the toner cohesion and the increase of the charge amount of the toner. As a result, when cleaning, the toner easily intrudes into the inside of the lubricating layer. When the toner easily penetrates into the inside of the lubricating layer, the lubricating layer is broken. Then, it was found that streak-like images due to cleaning failure appear on the recording material P, or abnormal noise is generated due to the decrease in lubricity.

  It was also found that when the formation of the lubricating layer becomes unstable due to toner deterioration, the effect of maintaining the lubricating layer is hardly obtained even if the amount and frequency of the toner supply operation are increased.

  The amount of charge per unit mass of toner on the surface of the developing roller 4a when forming a toner image on the photosensitive drum 1 was measured using the toner in the present embodiment. The amount of charge per unit mass at the time of new product was -30 μC / g. On the other hand, when the use was repeated until the end of the usable amount of the process cartridge, the charge amount per unit mass of the toner was -60 μC / g.

(Toner supply operation via intermediate transfer belt and intermediate transfer brush)
Even when the toner is deteriorated, the lubricant layer can be stably formed by controlling the charge amount when supplying the cleaning blade 6a.

  In order to maintain the lubricating layer even when the toner is deteriorated, the first supply operation via the intermediate transfer belt 7 and the intermediate transfer brush 11 is performed. By bringing the intermediate transfer brush 11 to which a predetermined voltage is applied into contact with the toner image on the surface of the intermediate transfer belt 7, the charge amount of the toner is controlled. Then, the toner whose charge amount has been controlled is supplied to the contact portion between the photosensitive drum and the cleaning blade. Thus, the lubricating layer is formed, and the lubricating effect can be maintained. Further, it is possible to prevent streak images due to poor cleaning and abnormal noise due to a decrease in lubricity.

  Hereinafter, the first supply operation (corresponding to the supply operation) through the intermediate transfer belt 7 and the intermediate transfer brush 11, which is a characteristic part of the present invention, will be described.

  In the first supply operation described below, the toner image is transferred from the photosensitive drum 1 to the intermediate transfer belt 7, passes through the contact portion, and is supplied from the intermediate transfer belt 7 between the photosensitive drum 1 and the cleaning blade 6a. Ru.

  The first supply operation is performed by the control unit 10. The first supply operation is performed when an image forming operation for transferring a toner image to the recording material P or a correction operation of image forming conditions (for example, density correction, correction of the positional relationship between a scanner and a photosensitive drum, etc.) is not performed. Be done.

  As described above, the image forming apparatus performs the toner supply operation when the integrated value of the moving distance a of the photosensitive drum 1 reaches a predetermined threshold. At this time, either the first supply operation or the second supply operation is performed.

  In the present embodiment, the first supply operation is performed when the cumulative use amount of the developing device 4 is equal to or more than a predetermined amount. The cumulative use amount of the developing device 4 includes the cumulative number of rotations of the developing roller 4a, the driving time (cumulative driving time) of the developing device 4, the cumulative number of recording materials P printed using the developing device 4, and the like. In addition, the first supply operation may be performed when the cumulative number of revolutions of the photosensitive drum 1 is equal to or more than a predetermined amount.

  In the present embodiment, when the number of recording materials that can be printed using the developing device 4 is 30,000 in terms of A4 (210 × 297 mm), periodically when the cumulative number reaches 10000 or more. Instead of the second supply operation, the first supply operation is performed.

  However, the timing at which the first supply operation is started is not limited to this. The first supply operation may be started before the lubrication of the photosensitive drum 1 and the cleaning blade 6a becomes insufficient. For example, printing can be continued only with the second supply operation, and it can be confirmed in advance when the lubrication will be insufficient, and the timing for starting the first supply operation can be determined.

  The timing at which the first supply operation is performed can be selected as appropriate. For example, only the first supply operation may be performed when the cumulative use amount of the developing device exceeds a predetermined amount. Also, the first supply operation and the second supply operation may be alternately performed. The first supply operation and the second supply operation may be performed at a predetermined rate. Furthermore, the ratio at which the first supply operation and the second supply operation are performed may be increased or decreased according to the cumulative use amount of the developing device. That is, the execution frequency of the first supply operation when the cumulative use amount of the developing device is large may be higher than the execution frequency of the first supply operation when the cumulative use amount is small.

  An outline of the first supply operation will be described with reference to FIG. FIG. 9 is an explanatory view of the toner supply operation through the intermediate transfer belt and the intermediate transfer brush as viewed from the direction orthogonal to the axis 1 a of the photosensitive drum 1. FIG. 9 is drawn in a form in which related members are arranged on a plane.

  In FIG. 9, the toner image Tz formed on the photosensitive drum 1 (1s) is conveyed by the intermediate transfer belt 7 in the R2 direction, passes through the intermediate transfer brush 11, and the photosensitive drum 1 (1e) to be supplied and the cleaning member The state supplied to 6a is shown. As described later, the photosensitive drums 1s and 1e may be the same or different.

  First, a toner image Tz is formed on the surface of the photosensitive drum 1 (1s) by the developing device 4. Then, at the primary transfer portion, the toner image Tz formed on the photosensitive drum 1 is transferred to the intermediate transfer belt 7. The toner image transferred to the intermediate transfer belt 7 is conveyed in the direction of the arrow R2 in FIGS. 1 and 9 by the rotation of the intermediate transfer belt 7. The transported toner image Tz passes through the secondary transfer portion. The toner image Tz that has passed through the secondary transfer portion passes through the contact portion between the intermediate transfer brush 11 to which a voltage is applied from the power supply 12 and the intermediate transfer belt 7. The toner image Tz that has passed through the contact portion is supplied from the primary transfer portion to the photosensitive drum 1 (1e) of the process cartridge to which the toner image Tz is to be supplied. The toner image Tz supplied from the primary transfer portion is supplied to the contact portion between the photosensitive drum 1 (1e) and the cleaning blade 6a.

  When the toner (toner image) of the intermediate transfer belt 7 is rubbed by the intermediate transfer brush 11 to which a voltage is applied from the power supply 12, the charge amount of the toner can be changed. That is, in the first supply operation, the charge amount per unit mass of the toner image after passing through the contact portion is defined as the downstream charge amount, and the charge amount per unit mass of toner image before passing through the contact portion is upstream It is the side charge amount. At this time, the downstream charge amount and the upstream charge amount are different due to the contact between the toner image and the intermediate transfer brush 11.

  As described above, when the toner is deteriorated, the charge amount of the toner image may be increased. When the charge amount of the toner image is too high, it affects the formation of the lubricating layer. In this case, a voltage is applied from the power supply 12 to the intermediate transfer brush 11 so that the absolute value of the downstream charge amount is smaller than the absolute value of the upstream charge amount, and the charge amount of the toner image is controlled. .

  Further, the amount of charge of the toner may be reduced depending on the material of the toner and the degree of deterioration. If the charge amount of the toner image is too low, the toner is not sufficiently supplied from the intermediate transfer belt 7 to the photosensitive drum 1. In this case, a voltage is applied from the power supply 12 to the intermediate transfer brush 11 so that the absolute value of the downstream charge amount is larger than the absolute value of the upstream charge amount, and the charge amount of the toner image is controlled. .

  In the present embodiment, in the first supply operation, the polarity of the downstream charge amount and the polarity of the upstream charge amount are the same polarity and are negative. Further, a voltage is applied from the power source 12 to the intermediate transfer brush 11 so that the absolute value of the downstream charge amount is smaller than the absolute value of the upstream charge amount, and the charge amount of the toner image is controlled.

  In the first supply operation, the charge amount of the toner supplied from the intermediate transfer belt 7 to the photosensitive drum 1 is preferably close to the charge amount of the toner in a state where the degree of deterioration is small. That is, it is desirable that the charge amount be changed by the intermediate transfer brush 11 so that the charge amount on the downstream side is close to the charge amount of the toner in a state where the degree of deterioration is small.

  A desirable charge amount will be described as the downstream charge amount. The charge amount per unit mass of the toner carried on the developing roller 4a is referred to as a development charge amount. Then, it is assumed that the image forming operation is performed when the cumulative use amount of the developing device 4 is the first cumulative use amount smaller than the predetermined amount at which the first supply operation is performed. The development charge amount at this time is taken as a first charge amount. The toner carried by the developing roller 4a referred to here is the toner carried by the developing roller 4a on the downstream side of the developing blade 4b and the upstream side of the sealing sheet 4c in the rotational direction of the developing roller 4a. is there.

  In the present embodiment, in the first supply operation, the power supply 12 applies a voltage to the intermediate transfer brush 11 so that the difference between the first charge amount and the downstream charge amount is equal to the first charge amount and the upstream side. It was made smaller than the difference with the amount of charge.

  The target of the downstream charge amount is not necessarily limited to the above. For example, the developing charge amount when the cumulative use amount of the developing device 4 is a second cumulative use amount smaller than the first cumulative use amount is set as a second charge amount. At this time, the difference between the average of the first charge amount and the second charge amount and the downstream charge amount is smaller than the difference between the average of the first charge amount and the second charge amount and the upstream charge amount. You may

  Further, when the cumulative use amount of the developing device 4 is smaller than the predetermined amount at which the first supply operation is performed, the image forming operation is performed a plurality of times. Further, the development charge amount in each image forming operation is determined. Then, the average of the respective developer charge amounts is taken as the average charge amount. At this time, the difference between the average charge amount and the downstream charge amount may be smaller than the difference between the average charge amount and the upstream charge amount.

  In order to determine the first charge amount, the second charge amount, and the average charge amount, it is desirable that the developing device 4 be in a new state. Further, immediately after the start of use of the developing device 4, the charge amount of the toner carried on the developing roller 4a may not be stable. In this case, the image forming operation may be continued for a while (for example, 1000 sheets or about 3% of the usable amount), and each charge amount may be determined after fluctuation of the charge amount is reduced.

  In the present embodiment, when the number of printable recording materials (converted to A4) by the developing device 4 is 30,000, 1,000 to 3,000 (less than 10% of the usable amount) are in the initial state. Then, in the image forming operation performed in the initial state, the development charge amount was measured, and the above-described first charge amount, which is the target of the downstream charge amount, was determined. The second charge amount and the average charge amount can also be determined by the same method.

  The downstream charge amount changes in accordance with the voltage applied to the intermediate transfer brush 11 by the power supply 12. Therefore, a voltage is applied to the intermediate transfer brush 11 from the power supply 12 so that the downstream charge amount becomes a desired value. At this time, the relationship between the cumulative use amount of the developing device 4, the amount of charge on the upstream side, the amount of charge on the downstream side, and the voltage applied by the power supply 12 may be determined in advance to determine the magnitude of the voltage to be applied. Further, the apparatus main body 100 may be provided with means for measuring or estimating the upstream charge amount and the downstream charge amount, and the voltage applied by the power supply 12 may change with the measurement result or the estimation result.

  In the present embodiment, the magnitude of the voltage at which a desired charge amount is obtained is obtained in advance, and a predetermined voltage is applied to the intermediate transfer brush 11 from the power supply 12 during the first supply operation. As a result, the amount of charge on the downstream side was made to be a desired value through the usable amount of the process cartridge (in particular, the developing device).

  As shown in FIG. 9, in order to improve the lubricity between the photosensitive drum 1 and the cleaning blade 6a, the toner image extends over a wide range of the axial direction of the photosensitive drum 1 (the same as the longitudinal direction of the cleaning blade). Is desirable. The toner image of this embodiment is a toner image extending from one end of the photosensitive drum 1 toward the other end including the central portion of the photosensitive drum 1 in the axial direction of the photosensitive drum 1. However, it is not limited to this. The toner image does not have to be parallel to the axial direction of the photosensitive drum 1. In addition, it may be a toner image in which there is a slight gap in the middle part. There may be more than one along the rotational direction R2. Also, assuming that the first supply operation is performed a plurality of times, when the toner images of the first supply operation at that time are overlapped, the other end including the central portion of the photosensitive drum from the one end of the photosensitive drum 1 The toner image may be formed to extend toward the image.

(Flow of the first supply operation)
The outline of the operation of the configuration of the present embodiment described above will be described with reference to the flowchart of FIG.

(Start of first supply operation: 301)
The execution of the first feeding operation for forming the lubricating layer is requested and the operation is started.

(Toner image formation on the surface of the photosensitive drum: 302)
The toner is supplied (developed) from the developing device 4 to the photosensitive drum 1. In this embodiment, the same operation as the image forming operation described above is performed. That is, after the photosensitive drum 1 is charged by the charging roller 2, a latent image (bright portion potential) is formed on the surface of the photosensitive drum 1 by the scanner 3. Then, by bringing the developing roller 4 a into contact with that portion, a toner image is formed on the surface of the photosensitive drum 1. The voltages at the time of image formation on the recording material P and at the time of the first supply operation may be different.

(Transfer to Intermediate Transfer Belt: 303)
The toner image on the surface of the photosensitive drum 1 is primarily transferred to the intermediate transfer belt 7 at the primary transfer portion. Here, the same operation as the image forming operation is performed. The voltages at the time of image formation on the recording material P and at the time of the first supply operation may be different.

(Downstream station, passing secondary transfer section: 304)
The toner image primarily transferred to the intermediate transfer belt 7 is passed through another downstream station. That is, the toner image is prevented from moving from the intermediate transfer belt 7 to the photosensitive drum 1 at the primary transfer portion of the other station on the downstream side.

  For example, the photosensitive drum 1 and the primary transfer portion of the downstream station are separated by the separation mechanism. Alternatively, a voltage of the reverse polarity (in this case, positive polarity) to the toner image is applied to the downstream primary transfer roller 51. As a result, the supply of the toner image from the intermediate transfer belt 7 to the photosensitive drum 1 is suppressed at the downstream station.

  Next, the toner image is caused to pass through the secondary transfer portion. That is, movement of the toner image from the intermediate transfer belt 7 to the secondary transfer roller 18 at the secondary transfer portion is suppressed.

  For example, the secondary transfer roller 18 and the intermediate transfer belt 7 are separated by the separation mechanism. Alternatively, a voltage of the same polarity (in this case, negative polarity) as that of the toner image is applied to the secondary transfer roller 18. Thus, movement of the toner image from the intermediate transfer belt 7 to the secondary transfer roller 18 is suppressed. The power source 12 may be connected to the secondary transfer facing roller 8 to apply a voltage of the reverse polarity (in this case, positive polarity) to the toner image.

(Contact by Intermediate Transfer Brush: 305)
The intermediate transfer brush 11 to which a voltage is applied is brought into contact with the toner image which has passed through the secondary transfer portion to control the charge amount of the toner.

(Passing upstream station: 306)
There may be a station where another process cartridge is mounted at the upstream side in the rotational direction R2 with respect to the station where the process cartridge C where the toner image is supplied from the intermediate transfer belt 7 to the photosensitive drum 1 is mounted. In this case, the toner image needs to pass through the upstream station. That is, at the upstream station, the toner image is prevented from moving from the intermediate transfer belt 7 to the photosensitive drum 1.

  For example, when the toner image that has passed through the contact portion reaches the upstream station, the upstream primary transfer roller 5 is separated from the photosensitive drum 1. Then, the primary transfer portion and the photosensitive drum 1 are separated. Alternatively, a voltage (in this case, positive polarity) having a polarity opposite to that of the charge amount of the toner image is applied to the primary transfer roller 5 of the upstream station. Thereby, at the upstream station, it is possible to prevent the toner image from moving as much as possible.

(Transfer to the photosensitive drum: 307)
The toner image is transferred to the photosensitive drum 1 at the primary transfer portion of the station where the lubricating layer is formed. When the charge-controlled toner reaches the primary transfer portion of the station where the lubricating layer is formed, the toner can be re-transferred from the intermediate transfer belt 7 to the photosensitive drum 1. For example, a voltage of the same polarity (in this case, negative polarity) as that of the toner is applied to the primary transfer portion. Thus, toner can be supplied from the intermediate transfer belt.

(Supply to cleaning blade: 308)
The toner transferred from the intermediate transfer belt 7 is supplied between the photosensitive drum 1 and the cleaning blade 6 a by the rotation of the photosensitive drum 1. Thus, the lubricating layer is formed between the photosensitive drum 1 and the cleaning blade 6a.

  The above is the flow of the first supply operation. The station for supplying the toner image to the intermediate transfer belt 7 and the station for supplying the toner image from the intermediate transfer belt 7 may be different.

(Effect of the first supply operation)
The effect of the first supply operation in the present embodiment will be described based on the operation outline shown in FIG. Specifically, the configuration for performing the first supply operation and the configuration for performing only the second supply operation (comparative example) are compared.

(Toner used)
Printing is performed using a process cartridge, using a toner whose charge amount has risen, that is, a toner which has been extremely deteriorated. While the charge amount at the time of new product was -30 μC / g, the toner used was -60 μC / g, and the charge amount was about twice as high as that at the new product. This toner corresponds to the toner in area 4 shown in FIG.

(Condition of first supply operation)
The image forming conditions at the time of the first supply operation were the same as those at the time of image formation on the recording material P. That is, the dark area potential of the photosensitive drum 1 was -500 V, and the light area potential was -100 V. Then, a light portion potential was formed on the photosensitive drum 1, and −300 V was applied to the developing roller to form a toner image on the photosensitive drum 1. A voltage of +300 V was applied to the primary transfer roller 5 to transfer the toner image to the intermediate transfer belt 7.

  At the downstream station, the photosensitive drum 1 was separated from the intermediate transfer belt 7. As a result, the toner image is made to pass through the other downstream station while being held by the intermediate transfer belt 7. Here, as described above, a voltage of positive polarity may be applied to the primary transfer roller 5 at the downstream station.

  The secondary transfer roller 18 was separated from the intermediate transfer belt 7. As a result, the toner image is caused to pass through the secondary transfer portion while being held by the intermediate transfer belt 7. Here, as described above, a negative voltage may be applied to the secondary transfer roller 18, or a positive voltage may be applied to the secondary transfer counter roller 8.

  When the toner conveyed by the intermediate transfer belt 7 reaches the intermediate transfer brush 11, a voltage in which an AC voltage of ± 600 V is superimposed on a DC voltage of −200 V is applied to adjust the charge amount of the toner.

  When the toner image having passed through the contact portion came to the primary transfer portion to which toner was to be supplied, a DC voltage of -300 V was applied to the primary transfer portion. As a result, the toner is electrically moved to the photosensitive drum 1, and the toner is re-transferred to the photosensitive drum at the primary transfer portion.

(Condition of comparative example)
A comparative example was used to compare with the configuration of the present embodiment described above. The voltage settings of the comparative example were as follows.

  As in the example, when forming a toner image, the dark area potential of the photosensitive drum 1 was -500 V and the light area potential was -100 V. Then, a bright portion potential was formed in the longitudinal direction of the photosensitive drum 1, and a toner image was formed on the photosensitive drum 1 by applying -300 V to the developing roller 4a.

  Further, a voltage of -300 V was applied to the primary transfer roller 5 to control that the toner was not transferred to the intermediate transfer belt 7. Thus, the toner was supplied directly to the cleaning blade 6 a without passing through the intermediate transfer belt 7.

(Other conditions)
Further, the toner supply operation of the configuration of the present embodiment and the comparative example was performed every time printing of 200 sheets in A4 conversion. After starting the test, 2000 sheets were printed.

(result)
The occurrence of streaks due to cleaning failure and the occurrence of abnormal noise due to a decrease in lubrication performance were confirmed. Furthermore, the condition of the lubricating layer was observed.

  The observation results of the lubricating layer are shown in FIG. 4, and the charged charge amount of the supplied toner immediately before the lubricating layer and the confirmation results of streaks and abnormal noise are shown in FIG.

  FIG. 4 is a top view of the surface of the photosensitive drum 1. 403 is the surface of the photosensitive drum 1 of this embodiment. Reference numeral 404 denotes the surface of the photosensitive drum 1 of the comparative example.

  When the cleaning blade 6 a is removed, the formation of the lubricating layer 402 can be confirmed upstream of the cleaning blade 6 a in the rotational direction (arrow direction) of the photosensitive drum 1. The longitudinal width of the lubricating layer substantially matches the width of the cleaning blade 6a. The width of the lubricant layer is around 100 um.

  In the configuration of the present embodiment, a stable lubricating layer was formed over the entire longitudinal region. This was the same state as the lubricating layer formed when using the toner whose deterioration did not progress in the comparative example.

  In contrast, in the configuration of the comparative example, an unstable lubricating layer was formed. The short width was narrower than the lubricating layer in the configuration of the present example. There were also places where the lubricating layer was not formed.

  In FIG. 5, the symbol of ○ was used when no streaks or abnormal noise was generated, and the symbol x was generated. In the configuration of this embodiment, the charge amount after passing through the intermediate transfer brush 11 is controlled to -35 μC / g, which is close to that at the time of new product. The streaks and noise did not occur while printing 2000 sheets. In the comparative example, the charge amount of the toner image supplied to the photosensitive drum 1 was −60 μC / g. From about 500 sheets after printing was started, streaks and noise began to occur. Stripes and abnormal noise always occurred until printing of 2000 sheets was completed.

  As described above, it is possible to form a lubricating layer by using a toner in which the charge control portion (intermediate transfer brush as a contact member) of the intermediate transfer belt is passed and the charge amount of the toner is adjusted even for toner whose toner deterioration has progressed. Could suppress the generation of streaks and noise.

  In this embodiment, the voltage applied to the intermediate transfer brush 11 is a voltage in which AC is superimposed on DC. However, when performing charge control with the intermediate transfer brush 11, only an alternating voltage may be used, or only a direct voltage may be used. Furthermore, since the amount of charge changes depending on the degree of toner deterioration, it is also effective to change the voltage applied to the intermediate transfer brush and implement charge control at an appropriate voltage value. Further, although the description has been made using the brush 11 in the present embodiment, the same effect can be obtained even if it has a roller shape or a sheet shape.

  In the description of the configuration of the present embodiment, the description has been made on the assumption that the toner is supplied to the cartridge forming the lubricating layer using the toner in the same process cartridge. For example, using the toner in a specific process cartridge, charge control is performed by the intermediate transfer body brush 11, and the same effect can be obtained by supplying the toner to each process cartridge and forming a lubricating layer as appropriate. It becomes possible. Also, after supplying toner from a plurality of process cartridges and collectively performing charge control with the intermediate transfer body brush 11, it is also possible to obtain the same effect by forming lubricant layers by supplying each process cartridge. is there. In addition to the lubricating layer forming effect, for example, by suppressing the toner supply from a station with a small amount of toner, an effect can be obtained such that printing in full color can be made longer.

  As described above, by performing the first supply operation via the intermediate transfer belt 7, toner can be supplied to the contact portion between the photosensitive drum 1 and the cleaning blade 6a. Then, the lubricity at the contact portion between the photosensitive drum 1 and the cleaning blade 6a can be maintained. In addition, even when the deteriorated toner is used, the above-mentioned effect can be obtained.

  In the first embodiment, even when toner deterioration has significantly progressed, charge control is performed with the intermediate transfer member brush and supplied again to the photosensitive drum, whereby the lubricating layer formed between the cleaning blade and the photosensitive drum is stabilized. It could be formed. And, the generation of streaks and abnormal noise could be suppressed.

  The present embodiment is characterized in that the frequency at which the first supply operation is performed differs depending on the toner deterioration state.

  At the time of image formation, the degree of destruction of the lubricating layer by the primary transfer toner varies depending on the degree of progress of toner deterioration. Therefore, according to the toner deterioration degree, the frequency of the first supply operation of performing charge control with the intermediate transfer member brush is changed via the intermediate transfer belt. Thereby, maintenance of the cleaning property and suppression of abnormal noise can be achieved together with the formation of the lubricating layer.

  In the present embodiment, the control unit 10 can execute the first supply operation at a first frequency and a second frequency different from the first frequency. The frequency refers to the amount of rotation of the developing roller 4a, the amount of rotation of the photosensitive drum 1, and the number of recording materials subjected to the image forming operation (the size of a specific recording material (for example, A4)). (Number of sheets converted to

  The control unit 10 executes the first supply operation at the first frequency when the toner deterioration state is the first deterioration state. The control unit 10 executes the first supply operation at the second frequency when the toner deterioration state is the second deterioration state. The second deterioration state is a state in which the toner is more deteriorated than the first deterioration state. And, the second frequency is different from the first frequency. In the following description, the second frequency is higher than the first frequency.

  In addition, the frequency of the first supply operation may be determined based on the accumulated rotation amount of the developing roller 4a after the start of use of the process cartridge.

  In this case, the control unit 10 executes the first supply operation at the first frequency when the accumulated rotation amount of the developing roller 4a is the first accumulated rotation amount. The control unit 10 executes the first supply operation at the second frequency when the accumulated rotation amount of the developing roller 4a is the second accumulated rotation amount. The second accumulated rotation amount is larger than the first accumulated rotation amount. And, the second frequency is higher than the first frequency.

  The cumulative amount of rotation of the photosensitive drum 1 and the cumulative number of printed sheets of the recording material P (including those converted to a specific size) may be used instead of the cumulative amount of rotation of the developing roller 4a. Further, the influence of the remaining amount of toner remaining in the developing device may be taken into consideration. Furthermore, the driving time of the process cartridge can also be used.

  The relationship between the state of toner deterioration, the cumulative amount of rotation, the cumulative number of printed sheets, the drive time of the process cartridge, etc., and the execution frequency of the first supply operation is the memory attached to the storage device of the apparatus main body 100 or the memory attached to the process cartridge. It may be saved to the device. Also, the degree of deterioration of the toner may be measured directly.

  The degree of destruction of the lubricating layer for each degree of toner deterioration will be described. As toners having different degrees of toner deterioration, three types of toners of area 1, area 2 and area 4 in the description of FIG. 6 used in the first embodiment are used.

  As an experiment, the toner whose charge was controlled by the intermediate transfer member brush 7 with each toner was supplied to the contact portion between the photosensitive drum 1 and the cleaning blade and 6a to form a lubricating layer. At this time, the image forming operation was continuously performed without supplying the toner through the intermediate transfer belt 7.

  The size of the recording material was A4. Then, the presence or absence of breakage of the lubricating layer and the number of printed sheets when breakage occurred were counted. As a judgment of destruction, it was observed and judged whether a lubricating layer will be in the unstable state (404) shown in FIG. At the same time, I also checked the number of streaks and noise.

  The results are shown in FIG. In the case of using the toner in the region 1 in which the deterioration did not progress, the lubricating layer was not broken even if the printing operation was performed on about 10,000 sheets without performing the first supply operation.

  With the toner in region 2, when the image forming operation was performed without performing the first supply operation, the destruction of the lubricating layer gradually proceeded and reached an unstable state at about 2000 sheets.

  In the case of the toner in region 4, when the image forming operation was performed without the first supply operation, the destruction of the lubricating layer rapidly progressed, and about 500 sheets became unstable.

  Further, with regard to the toner of region 2 and the toner of region 4, generation of streaks and generation of abnormal noise were also confirmed before and after the lubricating layer became unstable.

  From the results shown in FIG. 7, it was found that it is desirable that the timing of the first supply operation required to form the lubricating layer differs depending on the progress of toner deterioration, and that it is desirable to carry out frequently as the toner deterioration progresses.

  Therefore, when the frequency of the first supply operation according to the toner deterioration was changed, the formation and maintenance of the lubricating layer were verified.

  From the results of FIG. 7, the frequency of the first supply operation for each area of toner deterioration was determined. This is shown in FIG.

  When toner in the area 1 range was used, the first supply operation was not performed. That is, the first supply operation via the intermediate transfer belt is not performed.

  When toner in the range 2 was used, the first supply operation was performed once every 1000 sheets.

  When toner in the range of Region 4 was used, the first supply operation was performed once for 200 sheets.

  At each frequency, 10000 sheets were printed. As a result, no streaks or abnormal noise was found when using any of the toners. Moreover, when the lubricating layer was confirmed, it was confirmed that the substantially stable lubricating layer was formed.

  As described in the present embodiment, in the first supply operation in which the toner subjected to charge control by the intermediate transfer brush is supplied again to the photosensitive drum, the lubricating layer is constantly changed by changing the implementation frequency according to the state of toner deterioration. Explained that it is possible to form and maintain As a result, problems such as streaks and noise can be generated.

  In addition, by performing the first supply operation optimum for each toner deterioration state as described above, it is possible to reduce the operation time and the unnecessary use of toner by supplying an appropriate amount at an appropriate timing.

  In the present embodiment, it has been described that the frequency of the first supply operation is changed according to the toner deterioration state. On the other hand, the control unit 10 may change the voltage applied from the power supply 12 to the intermediate transfer brush 11 according to the toner deterioration state.

  In this case, the power supply 12 can apply to the intermediate transfer brush 11 at least a first voltage and a second voltage different from the first voltage. The power source 12 applies a first voltage to the intermediate transfer brush 11 when the toner deterioration state is the first deterioration state. Then, the power supply 12 applies a second voltage to the intermediate transfer brush 11 when the toner deterioration state is the second deterioration state.

  Further, the power supply 12 applies a first voltage to the intermediate transfer brush 11 when the cumulative rotation amount of the developing roller 4a is the first cumulative rotation amount, and the cumulative rotation amount of toner is the second cumulative rotation amount. At some point, a second voltage may be applied. The second accumulated rotation amount is larger than the first accumulated rotation amount.

  Note that, instead of the cumulative rotation amount of the developing roller, the cumulative rotation amount of the photosensitive drum and the cumulative number of printed sheets of the recording material P (including those converted into a specific size) can be used.

  The magnitude, polarity, and type of the voltage to be applied can be appropriately determined according to the target charge amount.

  According to the method described in the present embodiment, it is possible to carry out the optimal first supply operation according to the toner deterioration.

S image forming apparatus 1 photosensitive drum 2 charging roller 3 scanner 4 developing device 4a developing roller 6 cleaning device 6a cleaning blade 7 intermediate transfer belt 5 primary transfer roller 8 secondary transfer opposing roller 10 control unit (CPU)
11 Intermediate Transfer Brush 12 Power Supply 18 Secondary Transfer Roller 100 Device Body

Claims (14)

An image forming unit,
An image carrier that carries an electrostatic latent image;
A developing device for developing the electrostatic latent image, the developing device comprising a developer carrier for carrying a developer and forming a developer image on the image carrier;
A cleaning member in contact with the image carrier;
An image forming unit comprising
A rotatable intermediate transfer member for transferring the developer image transferred from the image carrier at a primary transfer portion to a recording material at a secondary transfer portion;
A contact member configured to be able to contact the intermediate transfer member at the contact portion, wherein the contact is disposed downstream of the secondary transfer portion and upstream of the primary transfer portion in the rotational direction of the intermediate transfer member. Members,
A power supply for applying a voltage to the contact member;
Control for performing a supply operation of supplying the developer image transferred from the image carrier to the intermediate transfer member and passed through the contact portion from the intermediate transfer member between the image carrier and the cleaning member A control unit that executes the supply operation when an image forming operation for transferring the developer image to the recording material is not performed;
Equipped with
The charge amount per unit mass of the developer image after passing through the contact portion in the supply operation is regarded as the downstream charge amount, and the charge amount per unit mass of the developer image before passing through the contact portion An image forming apparatus characterized in that the power supply applies a voltage to the contact member such that the downstream charge amount and the upstream charge amount are different.   The image forming apparatus according to claim 1, wherein an absolute value of the downstream charge amount is smaller than an absolute value of the upstream charge amount.   The image forming apparatus according to claim 1, wherein the supply operation is performed when an accumulated usage amount of the developing device is equal to or more than a predetermined amount. The image formation performed when the charge amount per unit mass of the developer carried on the developer carrier is a development charge amount, and the cumulative use amount is a first cumulative use amount smaller than the predetermined amount Assuming that the development charge amount in the operation is a first charge amount,
The image forming apparatus according to claim 3, wherein a difference between the first development charge amount and the downstream charge amount is smaller than a difference between the first development charge amount and the upstream charge amount. The charge amount per unit mass of the developer carried on the developer carrier is a development charge amount, and the development charge amounts in a plurality of the image forming operations executed when the accumulated usage amount is smaller than the predetermined amount Assuming that the average charge amount is
The image forming apparatus according to claim 3, wherein a difference between the average charge amount and the downstream charge amount is smaller than a difference between the average charge amount and the upstream charge amount.   The image forming apparatus according to any one of claims 1 to 5, wherein the polarity of the downstream charge amount and the polarity of the upstream charge amount are the same.   The image forming method according to any one of claims 1 to 6, wherein the control unit can execute the supplying operation at a first frequency and at a second frequency different from the first frequency. apparatus.   The control unit executes the supply operation at the first frequency when the deterioration state of the developer is a first deterioration state, and when the deterioration state of the developer is a second deterioration state, The image forming apparatus according to claim 7, wherein the supply operation is performed at the second frequency.   The control unit executes the supply operation at the first frequency when the accumulated rotation amount of the developer carrier is a first accumulated rotation amount, and the accumulated rotation amount of the developer carrier is second The image forming apparatus according to claim 7, wherein the supply operation is performed at the second frequency when the cumulative amount of rotation is.   The image forming apparatus according to any one of claims 1 to 7, wherein the power supply is capable of applying a first voltage and a second voltage different from the first voltage to the contact member. .   The power source applies the first voltage to the contact member when the deteriorated state of the developer is a first deteriorated state, and the deteriorated state of the developer is a second deteriorated state. The image forming apparatus according to claim 10, wherein a second voltage is applied to the contact member.   The power source applies the first voltage to the contact member when the accumulated rotation amount of the developer carrier is a first accumulated rotation amount, and the accumulated rotation amount of the developer carrier is a second 12. The image forming apparatus according to claim 10, wherein the second voltage is applied to the contact member when the amount of accumulated rotation is an accumulated amount.   The image forming apparatus according to any one of claims 1 to 12, wherein the power supply applies a voltage in which an alternating voltage is superimposed on a direct current voltage to the contact member.   The image forming apparatus according to any one of claims 1 to 13, wherein the image forming unit includes a storage device that stores information related to a use history of the image forming unit.

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