JP7337565B2 - image forming device - Google Patents

Description

The present invention relates to an image forming apparatus such as a laser printer, copier, facsimile machine, etc. using an electrophotographic method or an electrostatic recording method.

2. Description of the Related Art Conventionally, as an image forming apparatus using, for example, an electrophotographic method, there is an intermediate transfer type image forming apparatus provided with an intermediate transfer member. In this image forming apparatus, a toner image formed on a photoreceptor is primarily transferred onto an intermediate transfer member at a primary transfer portion, and then the toner image on the intermediate transfer member is secondarily transferred onto a recording material at a secondary transfer portion. . As the intermediate transfer member, an intermediate transfer belt formed of an endless belt is widely used.

In an intermediate transfer type image forming apparatus, toner (secondary transfer residual toner) remains on the intermediate transfer belt after the secondary transfer process. Therefore, a cleaning process is required to remove secondary transfer residual toner on the intermediate transfer belt before transferring the next image to the intermediate transfer belt. A blade cleaning method is widely used for this cleaning process. In the blade cleaning method, the moving intermediate transfer belt is cleaned by a cleaning blade as a cleaning member provided downstream of the secondary transfer portion with respect to the movement direction of the surface of the intermediate transfer belt (hereinafter also referred to as "belt conveying direction"). Secondary transfer residual toner is physically scraped off from above and recovered. As the cleaning blade, an elastic body such as urethane rubber is generally used. The cleaning blade is often arranged so as to be in the counter direction with respect to the belt conveying direction, and the edge portion of the free end portion is pressed against the surface of the intermediate transfer belt. Arranging the cleaning blade in the counter direction with respect to the belt conveying direction means arranging the cleaning blade so that the free end portion thereof is positioned upstream in the belt conveying direction rather than the fixed end portion thereof.

Here, for example, in order to reduce the frictional force between the cleaning blade and the intermediate transfer belt, suppress the wear of the cleaning blade, and improve the durability of the cleaning blade, the surface of the intermediate transfer belt is shaped. is being given. For example, Patent Document 1 discloses that a wrapping film is brought into contact with the surface of an intermediate transfer belt to form grooves on the surface of the intermediate transfer belt. The grooves are positioned substantially orthogonal to the longitudinal direction of the contact portion between the cleaning blade and the intermediate transfer belt, and the average interval between the grooves is 10 μm to 100 μm.

On the other hand, it is necessary to replace the intermediate transfer belt at an appropriate time before the desired performance cannot be obtained due to scratches on the surface or contamination due to adhered matter due to use. In general, the degree of rubbing scratches on the surface of the intermediate transfer belt varies greatly depending on the usage environment and usage conditions of the image forming apparatus, and does not necessarily match the number of printed sheets or usage time. Japanese Patent Application Laid-Open No. 2002-200001 discloses a configuration that determines when to replace the intermediate transfer belt by monitoring the formation of a toner filming layer on the intermediate transfer belt and the surface roughness of the intermediate transfer belt using an optical sensor. there is

JP 2015-125187 A Japanese Patent No. 3143200

However, a method or configuration for determining when to replace an intermediate transfer belt having an uneven surface as disclosed in Patent Document 1 has not been sufficiently studied.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an image forming apparatus capable of judging or reporting information regarding the life of an image carrier having an uneven surface.

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention comprises an image carrier for carrying a toner image, an optical sensor for irradiating the surface of the image carrier with light and detecting the reflected light, and a device for informing information about the life of the image carrier. In an image forming apparatus having a control means capable of executing the process of (1), diffraction occurs on the surface of the image carrier due to the irradiation light from the optical sensor during at least part of the lifetime of the image carrier, A part of the diffracted light is deviated from the light-receiving range of the optical sensor or enters the light-receiving range of the optical sensor. a first detection result of the optical sensor obtained by irradiating the surface of the image carrier with light; and a second detection result of the optical sensor obtained by irradiating the carrier with light. An image characterized in that specularly reflected light from a surface of a carrier can be received, and the control means executes the processing based on the index indicating an increase amount of the specularly reflected light received by the optical sensor. forming device.
According to another aspect of the present invention, an image carrier that carries a toner image, an optical sensor that irradiates light onto the surface of the image carrier and detects reflected light, and information about the life of the image carrier is reported. In the image forming apparatus having a control means capable of executing processing for the above, diffraction occurs on the surface of the image carrier due to the irradiation light from the optical sensor during at least part of the lifetime of the image carrier. , a part of the diffracted light goes out of the light receiving range of the optical sensor or enters into the light receiving range of the optical sensor, and the control means controls, at a first timing, a predetermined amount of irradiation light from the optical sensor. a first detection result of the optical sensor acquired by irradiating the surface of the image carrier with light, and the predetermined irradiation light amount from the optical sensor at a second timing after the first timing. a second detection result of the optical sensor obtained by irradiating the image carrier with light; An image forming method, wherein diffusely reflected light from the surface of an image carrier can be received, and the control means executes the processing based on the index indicating the amount of decrease in the diffusely reflected light received by the optical sensor. An apparatus is provided.

According to the present invention, it is possible to provide an image forming apparatus capable of judging or reporting information regarding the life of an image carrier having an uneven surface formed thereon.

1 is a schematic cross-sectional view of an image forming apparatus; FIG. FIG. 2 is a schematic block diagram showing a control mode of main parts of the image forming apparatus; 2A and 2B are a schematic enlarged partial cross-sectional view and a schematic top view of an intermediate transfer belt; FIG. 1A and 1B are a schematic cross-sectional view of an optical sensor and an explanatory diagram of a reflective diffraction grating; FIG. FIG. 10 is a graph showing the relationship between the average groove interval of an intermediate transfer belt and the diffraction angle; FIG. 5 is a graph showing BRDF of an intermediate transfer belt; It is a graph chart showing the relationship between the groove depth and the reflected light amount of the optical sensor. It is a graph chart showing transition of the output of the optical sensor and the groove depth in the endurance test. FIG. 4 is a flow chart of control in Example 1; FIG. 4 is a schematic diagram of a cleaning mechanism and a flow chart of control when the cleaning mechanism is provided. 8 is a schematic perspective view of an intermediate transfer belt of Example 2. FIG. FIG. 12 is a schematic enlarged partial cross-sectional view of regions X and Y in FIG. 11; FIG. 10 is a graph showing an output waveform of an optical sensor relating to the intermediate transfer belt of Example 2; FIG. 5 is a schematic top view of another example of an intermediate transfer belt;

Hereinafter, the image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

[Example 1]
1. Overall Configuration and Operation of Image Forming Apparatus FIG. 1 is a schematic cross-sectional view of an image forming apparatus 100 of this embodiment. The image forming apparatus 100 of this embodiment is a tandem-type laser beam printer that employs an intermediate transfer method and is capable of forming a full-color image using an electrophotographic method.

Image forming apparatus 100 has four stations 10Y, 10M, 10C, and 10K that form yellow (Y), magenta (M), cyan (C), and black (K) images, respectively, as a plurality of image forming units. have. Elements having the same or corresponding functions or configurations in the stations 10Y, 10M, 10C, and 10K are denoted by omitting Y, M, C, and K at the end of the symbols indicating that they are elements for one of the colors. A general description may be given. In this embodiment, the station 10 includes a photosensitive drum 1, a charging roller 2, an exposure device 3, a developing device 4, a primary transfer roller 5, a drum cleaning device 6, and the like, which will be described later.

A photosensitive drum 1, which is a rotatable drum-shaped (cylindrical) photosensitive member (electrophotographic photosensitive member) as a movable first image bearing member for carrying a toner image, is driven by a driving motor (Fig. (not shown) rotates in the direction of arrow R1 (clockwise direction) in the figure. The surface of the rotating photosensitive drum 1 is charged to a predetermined potential with a predetermined polarity (negative polarity in this embodiment) by a charging roller 2 which is a roller-shaped charging member as charging means. During the charging process, a predetermined charging voltage (charging bias) is applied to the charging roller 2 by a charging power supply (not shown). The charged surface of the photosensitive drum 1 is scanned and exposed according to image information by an exposure device 3 as an exposure means, and an electrostatic latent image (electrostatic image) is formed on the photosensitive drum 1 . In this embodiment, the exposure device 3 is composed of a scanner unit that scans laser light with a polygonal mirror, and irradiates the photosensitive drum 1 with a scanning beam modulated based on an image signal corresponding to each image forming unit 10. . The electrostatic latent image formed on the photosensitive drum 1 is developed (visualized) by supplying toner as a developer by a developing device 4 as developing means, and a toner image (toner image) is formed on the photosensitive drum 1 . be done.

An intermediate transfer belt 8, which is an endless belt and is an intermediate transfer member, is arranged so as to face the four photosensitive drums 1 as a movable second image bearing member. The intermediate transfer belt 8 is stretched around a driving roller 9a as a plurality of support rollers (stretching rollers), a tension roller 9b, and a secondary transfer counter roller (secondary transfer inner roller) 9c. A driving motor (not shown) as a driving means rotates a driving roller 9a, and a driving force is transmitted to the intermediate transfer belt 8, so that the intermediate transfer belt 8 circulates in the direction of an arrow R2 (counterclockwise direction) in the drawing ( Rotate. The intermediate transfer belt 8 will be described later in more detail. A primary transfer roller 5 which is a roller-shaped primary transfer member as a primary transfer means is arranged on the inner peripheral surface side of the intermediate transfer belt 8 . The primary transfer roller 5 is pressed toward the photosensitive drum 1 via the intermediate transfer belt 8 to form a primary transfer portion (primary transfer nip) N1 where the photosensitive drum 1 and the intermediate transfer belt 8 are in contact. The toner image formed on the photosensitive drum 1 as described above is primarily transferred onto the rotating intermediate transfer belt 8 by the action of the primary transfer roller 5 at the primary transfer portion N1. During the primary transfer, a primary transfer voltage (primary transfer bias) is applied to the primary transfer roller 5 by the primary transfer power source E1, the polarity of which is opposite to the normal charging polarity of the toner (the charging polarity during development) (positive polarity in this embodiment). ) is applied. For example, when forming a full-color image, the toner images of the colors Y, M, C, and K formed on the respective photosensitive drums 1 are successively transferred onto the intermediate transfer belt 8 at the respective primary transfer portions N1 so as to be superimposed. be.

A secondary transfer roller (secondary transfer outer roller) 11, which is a roller-shaped secondary transfer member as a secondary transfer means, is provided on the outer peripheral surface side of the intermediate transfer belt 8 so as to face the secondary transfer facing roller 9c. are placed. The secondary transfer roller 11 is pressed toward the secondary transfer counter roller 9c via the intermediate transfer belt 8, and the secondary transfer portion (secondary transfer nip) where the intermediate transfer belt 8 and the secondary transfer roller 11 are in contact with each other. form N2. The toner image formed on the intermediate transfer belt 8 as described above is nipped and conveyed between the intermediate transfer belt 8 and the secondary transfer roller 11 by the action of the secondary transfer roller 11 at the secondary transfer portion N2. is secondarily transferred onto a recording material (transfer material, sheet) P such as a sheet of paper. During secondary transfer, a secondary transfer voltage (secondary transfer bias) having a polarity opposite to the normal charge polarity of the toner is applied to the secondary transfer roller 11 by the secondary transfer power source E2. In a feeding/conveying device (not shown), the recording material P is sent out from the inside of the recording material storage section by a feeding roller or the like, and is conveyed by a conveying roller or the like. Then, the recording material P is conveyed to the secondary transfer portion N2 in timing with the toner image on the intermediate transfer belt 8 by the pair of registration rollers 13 .

The recording material P onto which the toner image has been transferred is conveyed to a fixing device 14 as fixing means. The fixing device 14 heats and presses the recording material P with an endless fixing film 14a containing a heat source and a pressure roller 14b, thereby fixing (melting and fixing) the toner image on the surface of the recording material P. FIG. The recording material P on which the toner image is fixed is discharged (output) to the outside of the apparatus main body 110 of the image forming apparatus 100 .

Toner remaining on the photosensitive drum 1 during the primary transfer (primary transfer residual toner) is removed and collected from the photosensitive drum 1 by a drum cleaning device 6 as photoreceptor cleaning means. The drum cleaning device 6 scrapes off primary transfer residual toner from the surface of the rotating photosensitive drum 1 with a cleaning blade 61 as a cleaning member arranged in contact with the surface of the photosensitive drum 1 . housed in Further, on the outer peripheral surface side of the intermediate transfer belt 8, an intermediate transfer member cleaning means is provided downstream of the secondary transfer portion N2 and upstream of the primary transfer portion N1 (most upstream primary transfer portion N1Y) in the belt conveying direction. belt cleaning device 20 is arranged. In this embodiment, the belt cleaning device 20 is arranged at a position facing the tension roller 9b with the intermediate transfer belt 8 interposed therebetween. Toner remaining on the intermediate transfer belt 8 during secondary transfer (secondary transfer residual toner) and paper dust are removed from the intermediate transfer belt 8 by a belt cleaning device 20 and collected. The belt cleaning device 20 scrapes off secondary transfer residual toner and the like from the surface of the intermediate transfer belt 8 that is rotating by using a cleaning blade 21 as a cleaning member arranged in contact with the surface of the intermediate transfer belt 8 . , is housed in the cleaning container 22 . The toner collected by the drum cleaning device 6 and the belt cleaning device 20 is sent to and stored in a waste toner box (not shown) by a collected toner conveying means (not shown).

In this embodiment, at each station 10, the photosensitive drum 1, the charging roller 2 acting thereon as a process means, the developing device 4 and the drum cleaning device 6 are integrated into a cartridge to form a process cartridge P. are doing. The process cartridge P is detachable from the apparatus main body 110 . The process cartridge P is replaced with a new one when the toner in the developing device 4 runs out or when the photosensitive drum 1 reaches the end of its life.

The intermediate transfer belt 8 supported by the three tension rollers 9a, 9b, and 9c, the primary transfer rollers 5, the belt cleaning device 20, and the like are integrated to form a belt unit 12. FIG. The belt unit 12 is detachable from the apparatus main body 110 . The belt unit 12 is replaced with a new one when the intermediate transfer belt 8 reaches the end of its life.

Further, in this embodiment, the developing device 4 uses a non-magnetic one-component developer as the developer. The developing device 4 includes a developing roller 41 as a developer carrying member, a developing container 42 containing the developer, a developing blade 43 as developer regulating means, and the like. In this embodiment, the charging polarity of the photosensitive drum 1 (in this embodiment, negative (Reversal development). The toner in the developing container 42 is negatively charged by the developing blade 43 and applied onto the developing roller 41 . During development, the developing roller 41 carrying toner is brought into contact with or close to the photosensitive drum 1, and a predetermined negative developing voltage (developing bias) is applied to the developing roller 41 by a developing power source (not shown). be.

Further, the toner used in this embodiment is composed of toner particles having an average particle size of 6.4 μm produced by an emulsion polymerization aggregation method, and silica fine particles having an average particle size of 20 nm are externally added. The average particle size is, for example, weight average particle size, and can be measured by the Coulter method. Measurement was performed using "Coulter Counter Multisizer 3" (manufactured by Beckman Coulter, Inc.) and dedicated software "Beckman Coulter Multisizer 3 Version 3.51" (Beckman Coulter stock) for setting measurement conditions and analyzing measurement data. (manufactured by the company). The method for producing toner particles is not limited to the emulsion polymerization aggregation method, and toner particles can be produced by other methods such as a pulverization method, a suspension polymerization method, and a dissolution suspension method.

Further, in this embodiment, the cleaning blade 21 of the belt cleaning device 20 is configured by attaching an elastic blade made of an elastic material to a support sheet metal as a support member. In this example, a substantially rectangular plate-shaped galvanized steel plate was used as the support plate. Further, in this embodiment, as the elastic blade, a substantially rectangular plate-shaped urethane rubber blade using urethane rubber (polyurethane) as an elastic material is used. The cleaning blade 21 is arranged in a counter direction with respect to the belt conveying direction, and the edge portion of the free end of the cleaning blade 21 is in contact with the surface of the intermediate transfer belt 8 .

Further, the image forming apparatus 100 of this embodiment has an optical sensor 7 as a detection means for detecting toner on the intermediate transfer belt 8 . A plurality of (for example, two) optical sensors 7 may be arranged along a direction substantially perpendicular to the belt conveying direction (hereinafter also referred to as "belt width direction"). Further, in this embodiment, the optical sensor 7 is arranged at a position facing the drive roller 9a as a facing member with the intermediate transfer belt 8 interposed therebetween. The optical sensor 7 detects the surface condition of the intermediate transfer belt 8 or the test toner image formed on the intermediate transfer belt 8 . The optical sensor 7 will be described later in more detail.

2. Control Mode FIG. 2 is a schematic block diagram showing a control mode of the main part of the image forming apparatus 100 of this embodiment. The image forming apparatus 100 has a printer control section 300 . The printer control unit 300 includes a printer controller 301, an engine control unit 302, a nonvolatile memory 303, an energization control unit 304, an image formation control unit 305, a replacement detection unit 306, and the like. A host computer 200 such as a personal computer outside the image forming apparatus 100 is communicably connected to the printer control unit 300 . The printer controller 301 communicates with the host computer 200 and receives image data. The printer controller 301 develops the received image data into information that can be image-formed by the image forming apparatus 100 , and performs signal exchange and serial communication with the engine control unit 302 . The engine control unit 302 exchanges signals with the printer controller 301, and controls the energization control unit 304, image formation control unit 305, and printer engine units via serial communication. Here, the printer engine is a general term for a mechanical unit that forms an image on the recording material P in the process described above and outputs the image. When the engine control unit 302 is instructed to start the image forming operation, it controls the energization control unit 304, the image formation control unit 305, and the printer engine units, and prints the recording material P at a predetermined process speed according to the above-described process. to form and output an image. An engine control unit 302 as a control means includes a CPU as an arithmetic control means and a ROM and a RAM as storage means.

A test toner image for density correction control, a test toner image for color misregistration correction control, and detection results of the surface state of the intermediate transfer belt 8 using the optical sensor 7, which will be described later in detail, are stored as storage means. is stored in the non-volatile memory 303 of . Based on the information stored in the non-volatile memory 303, the engine control unit 302 performs the density correction control (gradation correction control, image density control), color shift correction control (position shift correction control), intermediate transfer belt 8 Each control of life detection is performed.

The belt unit 12 is also provided with an identification nonvolatile memory (memory tag) 307 as identification means. When the belt unit 12 is attached to the apparatus main body 110 , the identification non-volatile memory 307 is communicatively connected to the printer control section 300 . The replacement detection unit 306 checks the identification information stored in the identification non-volatile memory 307 when the belt unit 12 is attached to or detached from the apparatus main body 110 . The replacement detection unit 306 can detect whether the belt unit 12 is new or whether the belt unit 12 has been replaced. A detection result (output signal) of the replacement detection unit 306 is input to the engine control unit 302 .

In this embodiment, the printer control section 300 is connected to an operation section (control panel) 308 provided in the apparatus main body 110 . An operation unit 308 includes display means such as a liquid crystal panel for displaying information to an operator such as a user or a service staff, and operation buttons for the operator to input information such as various settings to the printer control unit 300 . input means. Note that the operation unit 308 may be configured by a touch panel or the like having the functions of display means and input means.

3. Intermediate Transfer Body Next, the intermediate transfer belt 8 in this embodiment will be described. FIG. 3A is a schematic enlarged partial cross-sectional view of the vicinity of the surface layer of the intermediate transfer belt 8 when cut in a direction substantially perpendicular to the belt conveying direction (seen along the belt conveying direction). (b) is a schematic top view of the surface of the intermediate transfer belt 8 as seen from above.

The intermediate transfer belt 8 is an endless belt member (or film-like member) composed of two layers, a base layer 81 and a surface layer 82 . The base layer 81 is the thickest layer among the layers constituting the intermediate transfer belt 8 . The surface layer 82 constitutes the surface (peripheral surface) of the intermediate transfer belt 8 and carries toner transferred from the photosensitive drum 1 .

In this embodiment, the base layer 81 is a layer having a thickness of about 70 μm and made by dispersing carbon black as an electric resistance adjusting agent in polyethylene naphthalate resin. In this embodiment, polyethylene naphthalate resin is used as the material of the base layer 81, but the material is not limited to this. Thermoplastic resins, for example, polyimide, polyester, polycarbonate, polyarylate, acrylonitrile-butadiene-styrene copolymer (ABS), polyphenylene sulfide (PPS), polyvinylidene fluoride (PVdF) and other materials and mixed resins thereof may be used. As the electrical resistance adjusting agent (conductive agent), an ionic conductive agent may be used in addition to the electronic conductive agent.

Further, in this embodiment, the surface layer 82 is a layer having a thickness of about 3 μm, which is obtained by dispersing, for example, zinc oxide as an electric resistance adjusting agent in an acrylic resin as a base material. From the viewpoint of strength such as wear resistance and crack resistance, the material of the surface layer 82 is preferably a resin material (hardening resin) among hardening materials. An acrylic resin obtained by curing the combination is preferred. As the electrical resistance adjusting agent (conductive agent), an ionic conductive agent may be used in addition to the electronic conductive agent.

In general, urethane rubber and acrylic resin have a large frictional resistance due to sliding, and the cleaning blade 21 tends to curl up and wear due to repeated use of the cleaning blade 21 . The curling of the cleaning blade 21 means that the free end portion of the cleaning blade 21 contacting in the counter direction with respect to the belt conveying direction is curled so as to contact along the belt conveying direction.

Therefore, in the present embodiment, the surface of the intermediate transfer belt 8 is subjected to fine unevenness processing, and the grooves (grooves) along the belt conveying direction have an average groove interval I in the belt width direction of 2 μm or more and 10 μm or less. A plurality of grooves) 83 are formed side by side. In this embodiment, the grooves 83 are present in substantially the entire circumferential direction (belt conveying direction) of the intermediate transfer belt 8 . Further, in this embodiment, the grooves 83 are present in substantially the entire width direction (belt width direction) of the intermediate transfer belt 8 . In the belt width direction, the grooves 83 are formed in substantially the entire area where the cleaning blade 21 and the intermediate transfer belt 8 contact each other (that is, an area equal to or larger than the width of the area where the cleaning blade 21 and the intermediate transfer belt 8 contact each other). It is sufficient if it is formed.

Polishing, cutting, imprinting, and the like are generally known as means for forming fine unevenness, and can be appropriately selected and used so as to obtain the desired average groove interval I. In the present embodiment, from the viewpoint of processing cost and productivity, imprinting processing that utilizes the photo-curing property of the acrylic resin, which is the base material of the surface layer of the intermediate transfer belt 8 subjected to fine uneven processing, is adopted.

In the imprinting process, a mold (not shown) provided with a fine concave-convex shape opposite to the concave-convex shape desired to be formed on the surface of the intermediate transfer belt 8 is pressed against the surface of the surface layer 82 of the intermediate transfer belt 8 . In this embodiment, the mold has a substantially cylindrical shape, and the protrusions are formed substantially parallel to the direction of rotation of the cylinder. Accordingly, by transferring the fine irregularities of the mold to the surface of the surface layer 82 of the intermediate transfer belt 8 , a desired irregularity can be formed on the surface of the intermediate transfer belt 8 . The surface shape of the intermediate transfer belt 8 can be measured with, for example, a laser microscope VK-X250 manufactured by Keyence Corporation.

Here, the width (groove width) W of the grooves 83 on the surface of the intermediate transfer belt 8 is the width of the openings in the direction substantially perpendicular to the longitudinal axis direction of the grooves 83 . is defined as a range in which the thickness of the surface layer 82 is thin. In this embodiment, the groove width W is the width of the opening of the groove 83 in the direction substantially perpendicular to the belt conveying direction. In this embodiment, the groove width W is 1.2 μm. The groove width W is preferably less than the average particle size of the toner, more preferably less than half the average particle size of the toner. By making the groove width W smaller than the average particle diameter of the toner, it is possible to suppress the toner from entering the groove 83 and slipping through the cleaning blade 21 . Further, from the viewpoint of suppressing tilting of the convex portion of the mold, the groove width W of the intermediate transfer belt 8 is preferably 0.5 μm or more. In the configuration of this embodiment, the groove width W of the intermediate transfer belt 8 is preferably in the range of about 0.5 μm to 6 μm, more preferably in the range of 1 μm to 2 μm.

Further, the depth (groove depth) D of the grooves 83 on the surface of the intermediate transfer belt 8 is from the opening of the grooves 83 (the position of the outermost surface 84) to the bottom of the grooves 83 in the thickness direction of the intermediate transfer belt 8. defined as the depth of In this embodiment, the groove depth D is 0.45 μm when the intermediate transfer belt 8 is initially used (when new). The groove depth D is preferably 0.2 μm or more and less than the thickness of the surface layer 82 at the initial stage of use of the intermediate transfer belt 8 . If the groove depth D is too small, the recessed portions are likely to disappear due to scraping of the surface layer of the intermediate transfer belt 8 or the like, or cleaning failures are likely to occur as will be described later. Further, by setting the groove depth D to be less than the thickness of the surface layer 82 , the groove 83 is formed so as to exist only in the surface layer 82 without reaching the base layer 81 . Here, the thickness of the surface layer of the intermediate transfer belt 8 is about 1 μm or more and 5 μm or less, typically 1 μm or more, from the viewpoint of suppressing deterioration of durability due to too thin thickness and cracking of the surface layer due to too thick thickness. , about 3 μm or less.

Further, the interval (groove interval) I between the grooves 83 on the surface of the intermediate transfer belt 8 is one end (in the illustrated example, left edge). In this embodiment, the groove interval I is the interval between one end of the opening in the direction substantially orthogonal to the belt conveying direction. In this embodiment, the grooves 83 are formed at an equal pitch of 3.5 μm (substantially the same groove interval) over substantially the entire belt width direction, so that the average groove interval I is 3.5 μm. The groove interval I may be defined as the interval between the right end portions of the openings of the adjacent grooves 83 in the drawing, or may be defined as the interval between the bottom portions of the adjacent grooves 83 . The average groove interval I can be appropriately selected from the viewpoint of suppressing wear of the cleaning blade 21, but is preferably in the range of 2 μm or more and 10 μm or less, and is in the range of 3 μm or more and 4 μm or less. is more preferred. If the average groove interval I is too small, it may become difficult to form a uniform concave-convex shape. Also, if the average groove interval I is too large, it may become difficult to suppress wear of the cleaning blade 21 .

Here, in this embodiment, the grooves 83 are formed substantially parallel to the belt conveying direction as the direction along the belt conveying direction (FIG. 3B). Further, in this embodiment, the grooves 83 are formed continuously and substantially linearly over one round in the circumferential direction (rotational direction) of the intermediate transfer belt 8 . However, the direction along the belt conveying direction may extend along the direction intersecting the belt width direction, and may have an angle with respect to the belt conveying direction (FIG. 14). The angle formed by the longitudinal axis of the groove 83 with respect to the belt conveying direction is preferably 45 degrees or less, more preferably 10 degrees or less. Typically, as in this embodiment, the belt conveying direction and the longitudinal axis direction of the grooves 83 are substantially parallel. For the grooves 83 having an angle with respect to the belt conveying direction, a mold having projections oblique to the rotation direction of the cylinder may be used, or projections may be formed substantially parallel to the rotation direction of the cylinder as in the present embodiment. can be formed by using a mold in which is formed obliquely with respect to the belt conveying direction.

4. Optical Sensor Next, the optical sensor 7 in this embodiment will be described. In this embodiment, the optical sensor 7 has the function of detecting the surface condition of the intermediate transfer belt 8 . Then, in this embodiment, the engine control unit 302 executes processing for notifying information regarding the life of the intermediate transfer belt 8 based on the detection result. As the optical sensor, it is possible to use, as a light source, a light-emitting diode that emits light in the visible light region to the near-infrared region, that is, light with a wavelength of 400 to 1000 nm.

In this embodiment, the optical sensor 7 for detecting the surface state of the intermediate transfer belt 8 also serves as the optical sensor 7 for detecting test toner images for density correction control and color misregistration correction control. In other words, in this embodiment, the optical sensor 7 also functions as a density sensor for density correction control and as a color shift detection sensor for color shift correction control.

Generally, in an electrophotographic image forming apparatus, image density and image forming positions between image forming units fluctuate depending on various conditions such as changes in the environment in which they are used and the cumulative number of printed sheets. If the variation becomes excessive, it becomes impossible to obtain a high-quality image without color deviation of the original correct color tone. Therefore, in the image forming apparatus 100 of this embodiment, a test toner image (patch) is formed on the intermediate transfer belt 8 on a trial basis using toner of each color. ), or the misalignment of the test toner image is detected using the optical sensor 7 . Then, based on the detection result, density correction control is performed by feeding back the amount of exposure, developing bias, etc., or color misregistration correction control is performed by changing the writing timing of the laser light of the exposure device 3 for each color. As a result, high-quality images can be stably obtained.

FIG. 4A is a schematic cross-sectional view of the optical sensor 7. FIG. The optical sensor 7 includes a light-emitting element 71 such as an LED (light-emitting diode), a specular reflection light-receiving element 72 such as a photodiode, and a diffuse reflection light-receiving element 73 such as a photodiode. . The optical sensor 7 also has a holder 74, a protective cover (or a mold lens section) 75 that allows light to pass through, and the like. The optical sensor 7 irradiates the surface of the intermediate transfer belt 8 or the test toner image T on the intermediate transfer belt 8 with light from the light emitting element 71 and specularly reflects the reflected light from the surface of the intermediate transfer belt 8 or the test toner image T. The light is received by the light receiving element 72 and the irregular reflection light receiving element 73 . The specular reflection light receiving element 72 and the irregular reflection light receiving element 73 each output an electrical signal corresponding to the amount of received light. A detection result (output signal) of the optical sensor 7 is input to the engine control section 302 . As a result, the density of the test toner image T or the presence or absence of the test toner image T ( position) can be measured.

In this embodiment, a near-infrared LED with a center wavelength λ of 840 nm is used as the light emitting element 71 . When the normal direction of the intermediate transfer belt 8 is 0°, the light emitting element 71 irradiates the surface of the intermediate transfer belt 8 with light from an incident angle θi=−20°. In this embodiment, when the normal direction of the intermediate transfer belt 8 is 0° as described above, the specular reflection light receiving element 72 is +20°, and the irregular reflection light receiving element 73 is 0°. It is configured to receive reflected light from the test toner image T.

Here, the reflected light from the intermediate transfer belt 8 or the test toner image T contains both specular reflection components and irregular reflection (diffuse) components. The specular reflection light-receiving element 72 receives the reflected light containing both the specular reflection component and the diffuse reflection component, and the diffuse reflection light-receiving element 73 receives only the diffuse reflection component. When a high-density test toner image T is formed on the intermediate transfer belt 8 and the surface of the intermediate transfer belt 8 is covered, light is blocked by the toner, specularly reflected light is reduced, and specularly reflected light receiving element 72 is turned on. Output is reduced. On the other hand, since the yellow, magenta, and cyan toners diffusely reflect the infrared light of 840 nm used in this embodiment, when the toner adhesion amount on the intermediate transfer belt 8 increases, yellow, magenta, As for cyan, the output of the diffuse reflection light receiving element 73 increases. By using the difference obtained by subtracting the output of the irregular reflection light receiving element 73 from the output of the specular reflection light receiving element 72, the reflected light amount of only the regular reflection component can be obtained. In this embodiment, by detecting both the light amount (intensity) of the specularly reflected light and the light amount (intensity) of the diffusely reflected light, it is possible to accurately detect the density from high density to low density. there is Also, the optical sensor 7 cannot distinguish the color of the toner on the intermediate transfer belt 8 . Therefore, a test toner image T is formed on the intermediate transfer belt 8 for detecting the gradation of each monochromatic toner image.

5. Diffraction Phenomenon FIG. 4B is a schematic diagram for explaining the diffraction phenomenon caused by a reflective diffraction grating. In general, d is the grating interval, λ is the wavelength of the light beam, θi is the incident angle of the light beam with respect to the normal direction of the diffraction grating, θm is the reflection angle, and m is the diffraction order (m = ±0, ±1, ±2, · (positive and negative integers of .
d[sin(θi)+sin(θm)]=mλ (equation 1)

When m=0 (ie, specular reflection), θi=−θm, and the specular reflection does not depend on the lattice spacing d and the light wavelength λ.

In the case of other orders, the reflected lights reinforce each other at an angle θm at which the optical path difference of each reflected light becomes an integral multiple of the wavelength, depending on the lattice spacing d and the light wavelength λ. When (Equation 1) is expanded for the diffraction angle θm, it is represented by the following (Equation 2).
sin θm=mλ/d−sin θi (Equation 2)

When the angle of incidence with respect to the normal to the irradiated surface is defined as negative, the following tendencies are exhibited.
・As the incident angle θi increases, the right side of (Equation 2) increases and the diffraction angle θm increases. ・As the light wavelength λ increases, the right side of (Equation 2) increases and the diffraction angle θm increases. is smaller, the right side of (Equation 2) is larger and the diffraction angle θm is larger.

In the intermediate transfer belt 8 of this embodiment, the average groove interval I of the grooves 83 formed on the surface corresponds to the lattice interval d, and the light from the light emitting element 71 of the optical sensor 7 is diffracted.

FIG. 5 is a graph showing diffraction angles of m=-5th to +2nd order diffracted light from the light emitted from the optical sensor 7 of the present embodiment when the average groove interval I of the intermediate transfer belt 8 is swung. is. As can be seen from (Equation 2), the diffraction angle is inversely proportional to the grating spacing d (here, the average groove spacing I). Therefore, as shown in FIG. 5, the smaller the average groove interval I, the wider the diffraction angle range.

In this embodiment, the specularly reflected light receiving range of the specularly reflected light receiving element 72 of the optical sensor 7 is the range of 20°±5° indicated by the dashed line in FIG. Focusing on this range, it can be seen that when the average groove interval I is reduced to 50 μm, the −5th order diffracted light falls outside the light receiving range. If the average groove interval I is further reduced, diffracted light of lower order will be out of the light receiving range. Then, when the average groove interval I in this embodiment is reduced to 3.5 μm (the leftmost points in FIG. 5), reflected light other than the 0th order reflected light (that is, specular light) (that is, diffracted light) are all out of the light receiving range. On the other hand, in this embodiment, the light receiving range of diffusely reflected light by the diffusely reflected light receiving element 73 of the optical sensor 7 is the range of 0°±5° indicated by the one-dot chain line in FIG. Focusing on this range, for example, at the average groove interval I of 3.5 μm (the leftmost points in FIG. 5) in this embodiment, it can be seen that −1st-order diffracted light is mixed.

Here, an image forming apparatus using an image carrier that causes diffraction by irradiation light from the optical sensor 7 is defined as follows. That is, during at least part of the life of the image carrier, diffraction occurs on the surface of the image carrier due to irradiation light from the optical sensor 7, and part of the diffracted light is reflected in the light receiving range of the optical sensor 7 (regular reflection light receiving range). ) or may enter the light receiving range of the optical sensor 7 (diffused reflection light receiving range).

6. Scattering Characteristics of Diffracted Light FIG. 6 is a graph showing angular distribution characteristics of scattered light (hereinafter referred to as “BRDF”, which is an acronym for bidirectional reflectance distribution function) obtained as follows. BRDF (solid line) in FIG. 6 shows that light of λ=622 nm is applied at an incident angle of −20 to the surface of the intermediate transfer belt 8 having an uneven shape with an average groove interval I of 3.7 μm as in the present embodiment. °. The measurement of BRDF was performed using a small simple scattering detector Mini-Diff V1 manufactured by Cybernet Corporation. In FIG. 6, as a comparative example, the BRDF of a belt (hereinafter referred to as a "coated belt") that was only coated with an acrylic resin before being subjected to fine unevenness processing on the surface is also indicated by a dashed line.

As can be seen from FIG. 6, in the BRDF of the coated belt, the diffuse reflection component spreads broadly with respect to the peak of the specular reflection light. On the other hand, in the BRDF of the intermediate transfer belt 8 that has undergone fine unevenness processing, the amount of specularly reflected light of the 0th order decreases, and diffraction occurs in which the amount of reflected light increases at periodic angles. Also, the intensity of the diffracted light decreases as the order m increases. That is, with respect to specularly reflected light, when the surface of the intermediate transfer belt 8 that has undergone fine unevenness processing is irradiated with the same amount of light, the smaller the average groove interval I, the lower the order of diffracted light that can be detected. Therefore, the amount of reflected light is reduced.

7. Relationship Between Groove Depth and Reflected Light FIG. 7 is a graph showing the relationship between the groove depth D and the amount of regular reflection light and the amount of diffuse reflection light when the optical sensor 7 of the present embodiment is used. In FIG. 7, the horizontal axis indicates the groove depth D, and the vertical axis indicates the output (specular reflection light amount) of the specular reflection light receiving element 72 and the output (diffuse reflection light amount) of the diffuse reflection light receiving element 73 of the optical sensor 7 . Here, the intermediate transfer belt 8 having uneven shapes with different groove depths D on the surface obtained by adjusting the photo-curing conditions of the acrylic resin and the transfer pressure during imprint processing (groove depth D=0.15 μm, Three levels of 0.30 μm and 0.40 μm) and a coated belt (groove depth D=0 μm) were prepared. Then, using the optical sensor 7 of this embodiment, the amount of reflected light when the surface of each belt is irradiated with the same amount of light is compared.

As shown in FIG. 7, as the groove depth D became smaller, the amount of specularly reflected light increased and the amount of irregularly reflected light decreased. As can be seen from the BRDF in FIG. 6, this is considered to be because the amount of diffracted light decreases as the groove depth D decreases, approaching the amount of reflected light from the coated belt. This also coincided with the behavior of the diffraction efficiency that changes with the groove depth and the duty ratio (groove width with respect to the groove period), which is known for laminar diffraction gratings.

8. Relationship Between Change in Output of Optical Sensor and Change in Groove Depth Accompanied by Use of Intermediate Transfer Belt FIG. It is a graph diagram. In FIG. 8, the horizontal axis indicates the number of prints, and the vertical axis indicates the output (specular reflection light amount) of the specular reflection light receiving element 72 of the optical sensor 7 and the output (diffuse reflection light amount) of the diffuse reflection light receiving element 73 . Here, under an environment of temperature 23° C. and relative humidity 50%, using A4 paper with Extra basis weight of 80 g/m ² manufactured by OCE, four text patterns with a print ratio (image ratio) of each color of 5% were intermittently printed. A durability test was performed to output at Note that intermittent four-sheet printing refers to an output method in which a job of forming and outputting images on four recording materials P is repeated at predetermined time intervals. Then, every predetermined number of prints (approximately 5000 sheets), light is emitted from the optical sensor 7 to the surface of the intermediate transfer belt 8 with the same irradiation light amount. The transition of the average groove depth D from the beginning of use of the intermediate transfer belt 8 was measured. At each measurement timing, the amount of regular reflection light and the amount of irregular reflection light were each measured as an average value for one rotation of the intermediate transfer belt 8 . Further, the groove depth D is an average value measured using a laser microscope VK-X250 manufactured by Keyence Corporation.

Focusing on the amount of specularly reflected light, there was a tendency that although the amount decreased for a while from the beginning of use of the intermediate transfer belt 8, it monotonously increased after that. On the other hand, focusing on the amount of irregularly reflected light, although the amount slightly increases from the beginning of use of the intermediate transfer belt 8, it tends to monotonously decrease thereafter. Focusing on the average groove depth D, a tendency to decrease was observed in good agreement with the increase in specular reflection and the decrease in diffuse reflection.

The above results show the following. In other words, in the initial period of use of the intermediate transfer belt 8, the light emitted from the optical sensor 7 is slightly absorbed by filming due to adhesion of toner wax components and discharge products to the intermediate transfer belt 8, and the amount of specularly reflected light decreases. . However, after that, as the groove depth D changes (decreases) due to abrasion of the surface layer 82 of the intermediate transfer belt 8, the reflection approaches the smooth surface described in FIG. It is considered that the amount of reflected light increased. In general, in the case of a smooth intermediate transfer belt 8, when the surface of the intermediate transfer belt 8 is irradiated with the same amount of light, specularly reflected light decreases as the intermediate transfer belt 8 is used. On the other hand, the increase in specularly reflected light in the present embodiment is thought to simply indicate that the groove depth D on the surface of the intermediate transfer belt 8 has become smaller. Therefore, the groove depth D can be estimated based on the change (rate of change, amount of change) from the initial value of the amount of specularly reflected light.

Here, the cleaning blade 21 has a lubricating layer formed of toner and its external additive at the contact portion (cleaning nip portion) with the intermediate transfer belt 8 , so that the cleaning blade 21 maintains proper contact with the intermediate transfer belt 8 . Frictional force is maintained and appropriate cleaning performance can be exhibited. If the groove depth D on the surface of the intermediate transfer belt 8 is less than or equal to a predetermined value, the toner or external additive components clogging the grooves 83 may destroy the lubricating layer of the cleaning nip portion. In addition, since the lubricant layer is destroyed, the frictional force between the cleaning blade 21 and the intermediate transfer belt 8 increases, and the tip of the cleaning blade 21 may be damaged. Therefore, if the groove depth D becomes equal to or less than a predetermined value, there is a possibility that cleaning failure will occur. In fact, in the endurance test, when the number of printed sheets finally reached 350,000 (at the time when the groove depth D in FIG. 8 is indicated by ▴), the cleaning performance fell below the permissible limit, and cleaning failure occurred. Occurred.

The average groove depth D of the intermediate transfer belt 8 used in the durability test at the initial stage of use was 0.45 μm, and the average groove depth D at the time when cleaning failure occurred was less than 0.2 μm. Ta. In the endurance test, the average value of the output (amount of specular reflection light) of the specular reflection light receiving element 72 in one revolution of the intermediate transfer belt 8 was 1.6 V at the beginning of use of the intermediate transfer belt 8, indicating that the cleaning failure occurred. It was 2.6V when it occurred.

9. Intermediate Transfer Belt Life Detection In the present embodiment, in a configuration using an intermediate transfer belt 8 whose surface has an uneven shape and diffraction occurs due to irradiation light from an optical sensor 7, the groove depth accompanying use of the intermediate transfer belt 8 is measured. The life of the intermediate transfer belt 8 is determined based on the change in the detection result of the optical sensor 7 due to the change in the depth D. FIG. Then, when it is determined that the intermediate transfer belt 8 has reached the end of its life, it executes processing for informing an operator such as a user or a service person of information regarding the life of the intermediate transfer belt 8 .

A method for detecting the life of the intermediate transfer belt 8 in this embodiment will be described in more detail below. In this embodiment, the output of the specular reflection light receiving element 72 of the optical sensor 7 when the surface of the intermediate transfer belt 8 is irradiated with a predetermined amount of light is based on the rate of change from the beginning of use of the intermediate transfer belt 8. , the life of the intermediate transfer belt 8 is determined. FIG. 9 is a flow chart showing an outline of the procedure for life detection of the intermediate transfer belt 8 in this embodiment.

・Step 1
Engine control unit 302 detects intermediate transfer belt 8 when image forming apparatus 100 is started for the first time, or when replacement detection unit 306 detects that belt unit 12 has been replaced and a new belt unit 12 has been installed. start the end of life detection procedure.

・Step2
The engine control unit 302 starts operations of density correction control and color shift correction control, and determines the irradiation light amount (first irradiation light amount) L1 of the optical sensor 7 for density correction control and color shift correction control. In this embodiment, the irradiation light amount L1 for the density correction control and the color misregistration correction control is set so that the difference between the reflectance of the surface of the intermediate transfer belt 8 and the reflectance of the test toner image T having the maximum density is maximized. to select. That is, in this embodiment, the irradiation light amount L1 for the density correction control and the color misregistration correction control is set within a range in which the output of the optical sensor 7 is not saturated with respect to the amount of applied toner of the test toner image T, and the dynamic range of the optical sensor 7 is to be the widest possible.

・Step3
The engine control unit 302 determines the irradiation light amount (second irradiation light amount) L2 of the optical sensor 7 for life detection of the intermediate transfer belt 8 . In other words, the optimum density correction control and The irradiation light amount L1 for color misregistration correction control changes. Therefore, in this embodiment, as the amount of use of the intermediate transfer belt 8 increases, the irradiation light amount L1 for density correction control and color shift correction control is changed. On the other hand, the irradiation light amount L2 of the optical sensor 7 for detecting the life of the intermediate transfer belt 8 is kept constant at a predetermined irradiation light amount regardless of the increase in the usage amount of the intermediate transfer belt 8 . Specifically, in this embodiment, half the light intensity L1 for density correction control and color misregistration correction control determined for the new intermediate transfer belt 8 in Step 2 is used for life detection of the intermediate transfer belt 8. is the irradiation light amount L2. The amount of light irradiated by the optical sensor 7 is the amount of light (radiant energy) irradiated per unit area of the surface of the intermediate transfer belt 8 within a certain period of time, and can be measured by a known light amount measuring device. However, the amount of light emitted from the optical sensor 7 can be represented by the drive current (mA) of the light emitting element 71 . For example, when the driving current and the irradiation light amount are in a substantially proportional relationship, the second irradiation light amount L2, which is half the first irradiation light amount L1, is half the driving current for obtaining the first irradiation light amount L1. is the amount of irradiation light obtained by

・Step 4
The engine control unit 302 acquires the average value V2_ini of the output of the specular reflection light receiving element 72 at the irradiation light amount L2 of the optical sensor 7 for one round of the intermediate transfer belt 8 for the new intermediate transfer belt 8, be memorized. In this embodiment, the length of the intermediate transfer belt 8 in the belt conveying direction is 720 mm. Further, acquiring the average value of the outputs of the specular reflection light receiving elements 72 of the optical sensor 7 for one rotation of the intermediate transfer belt 8 is hereinafter simply referred to as "measurement of the surface state".

・Step 5
The engine control unit 302 advances to Step 6 when the number of printed sheets after the previous measurement of the surface state reaches a predetermined threshold value N as a predetermined timing. That is, in this embodiment, the engine control unit 302 has a function as a counting unit that sequentially accumulates and stores the number of printed sheets each time an image is formed on one sheet of recording material P and output. Each time an image is formed on one sheet of recording material P and output, the engine control unit 302 stores the cumulative number of prints from the previous measurement of the surface condition and the preset ROM in the engine control unit 302 . is compared with the threshold value N stored in . In this embodiment, the threshold value N=5000 sheets. Note that the number of prints may be set as the number of sheets converted to a predetermined size (for example, A4 size). Also, the timing for measuring the surface condition is not limited to the number of prints. The timing for measuring the surface condition is set using an arbitrary index value that correlates with the amount of use of the intermediate transfer belt 8, such as the rotation time and number of rotations of the intermediate transfer belt 8, and the rotation time and number of rotations of other rotating members. can do.

・Step 6
The engine control unit 302 acquires the average value V2_N of the output of the specular reflection light receiving element 72 at the irradiation light amount L2 of the optical sensor 7 for one round of the intermediate transfer belt 8 and stores it in the nonvolatile memory 303 . As described above, in this embodiment, the surface condition of the intermediate transfer belt 8 is measured with the same irradiation light amount L2 every N number of prints, and the measurement result is stored in the nonvolatile memory 303 . In the present embodiment, the next surface condition measurement is not performed immediately after the number of printed sheets from the previous surface condition measurement has passed N, but the output of all images of the job over N sheets is completed. After printing, the following surface condition is measured during the printing end processing. Here, a job refers to a series of operations for forming and outputting an image on one or more recording materials P, which is started by one start instruction. Further, the print end processing (post-rotation operation) is a state in which the photosensitive drum 1 and the intermediate transfer belt 8 are rotated for a predetermined organizing operation (preparation operation) after outputting the last image of the job. That's what I mean. The measurement of the surface condition of the intermediate transfer belt 8 can be performed at any timing during non-image formation, which is a period other than the image formation period for forming an image to be transferred onto the recording material P and output. . The non-image forming time includes, in addition to the post-rotation operation (printing end processing), the pre-multi-rotation operation and pre-rotation operation, which are preparatory operations before image formation, and the recording material P during continuous image formation. The period corresponding to the recording material P is during paper-to-paper operation.

・Step7
The engine control unit 302 calculates the change rate of the current measurement result V2_N of the surface condition of the intermediate transfer belt 8 with respect to the measurement result V2_ini of the surface condition of the new intermediate transfer belt 8, that is, V2_N/V2_ini. The engine control unit 302 then compares the rate of change with a predetermined threshold value R and determines whether the rate of change is greater than the threshold value R or not. The threshold value R is set in advance and stored in the ROM within the engine control unit 302 . In this embodiment, only the output of the specular reflection light receiving element 72 of the optical sensor 7 is referred to, and the threshold value R is set to 1.625 times based on the experimental results shown in FIG. That is, the threshold value R is the output of the optical sensor 7 when the groove depth D is less than 0.2 μm and there is a possibility that cleaning failure may occur when the groove depth D is 0.45 μm (new intermediate transfer belt 8). ) to the output of the optical sensor 7 . However, the threshold value R is not limited to the value of this embodiment, and can be appropriately set according to the groove depth D that satisfies the cleaning performance.

・Step8
If the engine control unit 302 determines in step 7 that the predetermined threshold value R is exceeded, the engine control unit 302 determines that the intermediate transfer belt 8 has reached the end of its service life, and performs processing for notifying information regarding the service life of the intermediate transfer belt 8. Execute. In this embodiment, as the processing, processing for displaying information informing that the intermediate transfer belt 8 has reached the end of its life or information prompting replacement of the intermediate transfer belt 8 on the display means of the operation unit 308 or the host computer 200. to run.

10. Effect As described above, the image forming apparatus 100 of the present embodiment has a control unit (engine control unit) 302 capable of executing processing for notifying information regarding the life of the intermediate transfer belt 8 . Further, in the image forming apparatus 100 of the present embodiment, at least part of the lifetime of the intermediate transfer belt 8, diffraction occurs on the surface of the intermediate transfer belt 8 due to irradiation light from the optical sensor 7, and part of the diffracted light is outside the light receiving range of the optical sensor 7 or within the light receiving range of the optical sensor 7 . In this embodiment, the control unit 302 executes the above processing based on the detection result of the optical sensor 7 obtained by irradiating the surface of the intermediate transfer belt 8 with light. In particular, in this embodiment, the control unit 302 irradiates the surface of the intermediate transfer belt 8 with light of a predetermined irradiation light amount from the optical sensor 7 at the first timing, and obtains the first detection result of the optical sensor 7 . , a second detection result of the optical sensor 7 obtained by irradiating the intermediate transfer belt 8 with light of the predetermined irradiation light amount from the optical sensor 7 at a second timing after the first timing, and The above processing is executed based on the index related to. In this embodiment, the optical sensor 7 is capable of receiving specularly reflected light from the surface of the intermediate transfer belt 8, and the control means 302 controls the amount of specularly reflected light received by the optical sensor 7 based on the index indicating the amount of increase in specularly reflected light received by the optical sensor 7. to execute the above process. Further, in this embodiment, the control means 302 executes the above process when the above index exceeds a predetermined threshold. Also, in this embodiment, the index is the rate of change between the first detection result and the second detection result. In this embodiment, the optical sensor 7 also serves as means for detecting the test toner image formed on the image carrier. Further, in this embodiment, the predetermined amount of irradiation light is different from the amount of irradiation light when the optical sensor 7 detects the test toner image. Here, the test toner image may be a test toner image for image density control or color misregistration correction control. Further, in this embodiment, a plurality of grooves along the belt conveying direction are formed on the surface of the intermediate transfer belt 8 so as to be aligned in the belt width direction. In this embodiment, the average value of the intervals between adjacent grooves is 2 μm or more and 10 μm or less. Further, in this embodiment, the intervals between the adjacent grooves are substantially the same over substantially the entire belt width direction.

As described above, in this embodiment, the service life of the intermediate transfer belt 8 is determined based on the change in the detection result of the optical sensor 7 due to the change in the groove depth D that accompanies the use of the intermediate transfer belt 8 . As a result, according to this embodiment, it is possible to accurately notify the user of the information regarding the life of the intermediate transfer belt 8 having an uneven surface.

Here, for example, in the conventional life detection method, which is known as a conventional technique and is described in Patent Document 2, it is assumed that there is no diffuse reflection component from the intermediate transfer belt at the beginning of use of the intermediate transfer belt. . When the diffused reflection component increases beyond a set value obtained experimentally in advance, it is determined that the intermediate transfer belt has reached the end of its service life. Therefore, in such a conventional life detection method, it may not be possible to accurately determine the life of the intermediate transfer belt 8 for which diffraction occurs due to the irradiation light from the optical sensor as in the present embodiment. be. On the other hand, according to the present embodiment, it is possible to accurately determine or report information regarding the life of the intermediate transfer belt 8 having the uneven surface formed thereon.

11. Modification Next, a modification of this embodiment will be described.

The image forming apparatus 100 may have a cleaning mechanism as cleaning means for the optical sensor 7 . FIG. 10A is a schematic diagram showing an example of the cleaning mechanism 30 for the optical sensor 7. FIG. In the illustrated example, the cleaning mechanism 30 includes a cleaning member 31 that cleans a protective cover (or a mold lens portion) 75 that is a light receiving portion (light receiving surface) of the optical sensor 7 , and a cleaning portion 31 that faces the optical sensor 7 . and a moving member 32 for moving. As the cleaning member 31, for example, nonwoven fabric, felt, sponge, or the like can be used. As the moving member 32, for example, a member that reciprocates in the belt width direction in conjunction with the opening and closing of a door (not shown) of the apparatus main body 110 for exchanging the process cartridge P and the belt unit 12 is used. be able to. It should be noted that the moving member 32 may be driven at a predetermined timing by a driving force transmitted from a driving motor or the like as driving means. In the illustrated example, the cleaning mechanism 30 cleans the protective cover 75 of the optical sensor 7 in conjunction with the opening and closing of the door. When the image forming apparatus 100 has the cleaning mechanism 30, the life of the intermediate transfer belt 8 can be determined based on the detection result of the optical sensor 7 in a predetermined period after the cleaning mechanism 30 operates. That is, if toner or the like adheres to the protective cover 75 of the optical sensor 7, there is a possibility that the detection accuracy of the change in the detection result of the optical sensor 7 due to the change in the groove depth D due to the use of the intermediate transfer belt 8 will be lowered. There is Therefore, the detection result of the optical sensor 7 within a predetermined period after cleaning by the cleaning mechanism 30 can be used as a true value to determine the life of the intermediate transfer belt 8 . The predetermined period can be determined in advance by experiments or the like as a period until the detection result of the optical sensor 7 is affected by adhesion of toner to the protective cover 75 or the like. As described above, the image forming apparatus 100 may have the cleaning mechanism 30 that cleans the optical sensor 7 . In this case, the control unit 302 can perform the above processing based on the detection result of the optical sensor 7 within a predetermined period after the optical sensor 7 has been cleaned by the cleaning mechanism 30 .

FIG. 10B is a flow chart showing an outline of the procedure for detecting the life of the intermediate transfer belt 8 in this case. The engine control unit 302 obtains information about the timing when the cleaning mechanism 30 was operated, and stores it in the nonvolatile memory 303 (Step 11). The engine control unit 302 determines the timing when the cleaning mechanism 30 is operated based on a detection signal from a door sensor (not shown) that detects, for example, that the door is closed (or opened). Information about (date, time, etc.) can be obtained. When the engine control unit 302 determines that the change rate of the detection result of the optical sensor 7 exceeds the threshold as described with reference to FIG. (Step 13). In this example, the door is opened and closed and the cleaning operation of the cleaning mechanism 30 is performed before obtaining the detection result of the optical sensor 7 regarding the new intermediate transfer belt 8 . The predetermined period is the elapsed time from the previous operation of the cleaning mechanism 30, or an integrated index value correlated with the amount of use of the intermediate transfer belt 8, such as the number of prints after that period. etc. can be set. In this case, the engine control unit 302 functions as counting means for counting the elapsed time and the integrated value of the index value. If the engine control unit 302 determines in step 13 that the period is within the predetermined period, the process proceeds to step 8 in FIG. On the other hand, if the engine control unit 302 determines in step 13 that it is not within the predetermined period (that is, the predetermined period has passed), it proceeds to step 5 in FIG. 9 to measure the surface state of the intermediate transfer belt 8 next time. wait for In this way, when the change rate of the detection result of the optical sensor 7 exceeds the threshold value, the life is not notified immediately, but the change rate exceeds the threshold value within a predetermined period after the cleaning mechanism 30 operates. In this case, the life of the intermediate transfer belt 8 can be notified.

Further, in this embodiment, the life of the intermediate transfer belt 8 is determined based on the detection result of specularly reflected light by the optical sensor 7, but the present invention is not limited to this. As can be seen from FIG. 8, the detection result of the diffusely reflected light by the optical sensor 7 also changes (typically, the amount of diffusely reflected light decreases) as the intermediate transfer belt 8 is used. Therefore, the service life of the intermediate transfer belt 8 may be determined using only the detection result of the diffusely reflected light by the optical sensor 7, or using both the detection result of the specularly reflected light and the detection result of the diffusely reflected light. When only the detection result of the diffusely reflected light is used, when the change rate of the detection result of the diffusely reflected light becomes larger than a predetermined threshold value, a process for notifying information about the life of the intermediate transfer belt 8 can be executed. . Further, when using both the detection result of the specular reflection light and the detection result of the diffuse reflection light, when the rate of change of one or both of the detection results exceeds a predetermined threshold value, the service life of the intermediate transfer belt 8 is reached. It is possible to execute processing for notifying information about. In this case, the threshold may be the same or different for the detection result of specular reflection light and the detection result of diffuse reflection light. In this way, the optical sensor 7 can receive the diffusely reflected light from the surface of the intermediate transfer belt 8, and the control means 302 performs the above processing based on the index indicating the amount of decrease in the diffusely reflected light received by the optical sensor 7. may be configured to execute

Further, in this embodiment, as an index of change in the detection result of the optical sensor 7, the rate of change with respect to a reference value (in this embodiment, the detection result when the intermediate transfer belt 8 is new) is used. Any metric can be used, such as the difference (ie, the amount of change) between .

In this embodiment, information indicating that the intermediate transfer belt 8 has reached the end of its life is notified when the index of change in the detection result of the optical sensor 7 (in this embodiment, the rate of change) exceeds a predetermined threshold value. However, the present invention is not limited to this. For example, an index (rate of change, amount of change) of the change in the detection result of the optical sensor 7 can be stored in the nonvolatile memory 303 at predetermined timings such as every N number of prints. Then, the transition of the indicator of the change in the detection result of the optical sensor 7 is monitored, the remaining life span of the intermediate transfer belt 8 is obtained, and the remaining life span of the intermediate transfer belt 8 is determined sequentially or by the operator. You may make it alert|report according to an instruction|indication. In this case, for example, the detection result of the optical sensor 7 for the new intermediate transfer belt 8 corresponds to 100% remaining life, and the detection result of the optical sensor 7 corresponding to the above threshold corresponds to 0% remaining life. can be Further, for example, a plurality of thresholds are set for changes in the detection result of the optical sensor 7, information indicating that the life of the intermediate transfer belt 8 is approaching, and information indicating that the intermediate transfer belt 8 has reached the end of its life. , etc. may be sequentially notified.

Further, in the present embodiment, information regarding the life of the intermediate transfer belt 8 is reported by means of display on the display means (display of a message notifying that the belt has reached the end of its life, a message prompting replacement, etc.). The invention is not limited to this. For example, it is possible to use any method capable of informing information about the life of the intermediate transfer belt 8, such as turning on or blinking a warning light, or producing a voice message.

In this embodiment, the surface condition of the intermediate transfer belt 8 is detected over one rotation of the intermediate transfer belt 8, but the present invention is not limited to this, and the intermediate transfer belt 8 is detected with sufficient accuracy. If the surface state can be detected, it may be detected in a section shorter than one round.

[Example 2]
Another embodiment of the present invention will now be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the image forming apparatus of the first embodiment. Accordingly, in the image forming apparatus of the present embodiment, elements having the same or corresponding functions or configurations as those of the image forming apparatus of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and detailed description thereof will be omitted. .

In this embodiment, the intermediate transfer belt 8 has a portion in which the surface fine unevenness processing is overlapped in a part of the circumferential direction. In this embodiment, the detection result of the optical sensor 7 for that portion is excluded from the calculation of the change in the detection result of the optical sensor 7 in the life detection of the intermediate transfer belt 8 . This makes it possible to determine the life of the intermediate transfer belt 8 with higher accuracy.

FIG. 11 is a schematic perspective view of the intermediate transfer belt 8 of this embodiment. The intermediate transfer belt 8 of this embodiment has an uneven surface formed by imprint processing. In the imprinting process, the pressure may be changed stepwise at the stage of starting to press the mold against the surface of the intermediate transfer belt 8 and at the stage of starting to separate the mold from the surface of the intermediate transfer belt 8 . This is to prevent the intermediary transfer belt 8 whose surface is hardened from being subjected to a load in an unnecessary direction and being broken. In addition, it is difficult to completely match the start point and the end point of the groove 83 in units of μm in the belt width direction. There may be some overlapping parts. Therefore, in the circumferential direction of the intermediate transfer belt 8, a non-overlapping region (non-overlapping portion) X in which the fine unevenness processing is not performed in an overlapping manner, and an overlapping region (overlapping portion) Y in which the fine unevenness processing is performed in an overlapping manner. , the average groove interval I and groove depth D may differ. In the overlapping region Y, only one of the average groove interval I and groove depth D may be different.

FIG. 12 is a schematic diagram of the vicinity of the surface layer of the intermediate transfer belt 8 when cut in a direction substantially perpendicular to the belt conveying direction (seen along the belt conveying direction) in each of the non-overlapping region X and the overlapping region Y. It is an enlarged partial cross-sectional view. In the non-overlapping region X and the overlapping region Y, grooves (groove shape, groove portion) 83 are formed along the belt conveying direction, as in the first embodiment. In this embodiment, the average groove interval I is 3.5 μm in the non-region X and 1.8 μm in the overlapping region Y. FIG. Further, the groove depth D (average value) is 0.45 μm in the non-overlapping region X and 0.25 μm in the overlapping region Y at the beginning of use of the intermediate transfer belt 8 . Since the same mold is used for both the non-overlapping region X and the overlapping region Y, and only the transfer pressure is different, the groove width W between the non-overlapping region X and the overlapping region Y is almost the same. Since the overlapping region Y differs from the non-overlapping region X in the average groove interval I and the groove depth D, the diffraction angle and the intensity of the diffracted light from the light emitted from the optical sensor 7 are different from those in the non-overlapping region X. .

FIG. 13 is a graph showing the output waveform of the optical sensor 7 when detecting about one rotation of the intermediate transfer belt 8 having the non-overlapping area X and the overlapping area Y in the belt conveying direction. In FIG. 13, the horizontal axis indicates time, and the vertical axis indicates the output (specular reflection light amount) of the specular reflection light receiving element 72 and the output (diffuse reflection light amount) of the diffuse reflection light receiving element 73 of the optical sensor 7 . As can be seen from FIG. 13, in the overlap region Y, the light amount of specularly reflected light drops sharply, and the light amount of irregularly reflected light rises sharply. In other words, including the detection result of the overlapping area Y in the calculation of the change in the detection result of the optical sensor 7 for detecting the life of the intermediate transfer belt 8 causes an error. On the other hand, since the detection results of the amount of specular reflection light and the amount of diffuse reflection light are clearly different in the non-overlapping area X and the overlapping area Y, it is easy to specify the detection result for each area from the output waveform of the optical sensor 7 .

Therefore, in this embodiment, in order to detect the life of the intermediate transfer belt 8, the boundary from the overlapping area Y to the non-overlapping area X is used as a starting point, and the same position in the non-overlapping area X (in this embodiment, the position of the non-overlapping area X is obtains the detection result of the optical sensor 7 regarding the entire area). Based on the detection result of the optical sensor 7 regarding the non-overlapping area X, the life of the intermediate transfer belt 8 is determined in the same manner as in the first embodiment. Specifically, in this embodiment, the engine control unit 302 acquires the detection result of the optical sensor 7 for one rotation of the intermediate transfer belt 8 as shown in FIG. is used for detecting the life of the intermediate transfer belt 8 only. Alternatively, only the detection result of the optical sensor 7 during a predetermined period excluding the period during which the overlapping area Y passes through the detection area of the optical sensor 7 may be obtained for detecting the life of the intermediate transfer belt 8 .

Thus, in this embodiment, the intermediate transfer belt 8 has the first region X and the second region Y shorter than the first region X in the belt movement direction. At least one of the average value of the groove interval and the average value of the groove depth differs from the second region Y. In this case, the control means 302 can perform processing for notifying information regarding the life based on the detection result of the optical sensor 7 regarding the first region X. FIG. Note that the average value of the groove spacing in the first region X is typically 2 μm or more and 10 μm or less. Further, typically, the groove spacing in the first region X is substantially the same over substantially the entire belt width direction.

As described above, according to the present embodiment, even when there is an overlapping portion of the fine unevenness processing on the surface of the intermediate transfer belt 8, the life of the intermediate transfer belt 8 can be determined with high accuracy.

[others]
Although the present invention has been described with reference to specific examples, the present invention is not limited to the above-described examples.

In the above-described embodiments, the intermediate transfer body has a multi-layer structure, but even if the intermediate transfer body has a single-layer structure, the same effect as in the above-described embodiments can be obtained by forming grooves on the surface. can be done. That is, the intermediate transfer member is not limited to a structure consisting of a plurality of layers, but may be a structure consisting of a single layer, in which case the surface of the single layer is the same as the surface of the surface layer in the above-described embodiments. It is sufficient if it has a shape of Further, even when the intermediate transfer member is composed of a plurality of layers, the number of layers is not limited to two. A single layer or a plurality of layers may be provided under the layer to be formed.

Further, the intermediate transfer member is not limited to a belt-like member, and may be a drum-shaped member (intermediate transfer drum) formed by stretching a sheet on a frame, for example, in accordance with the present invention. It can be similarly applied to achieve similar effects. Also, the image forming apparatus is not limited to the in-line type. For example, a plurality of developing devices are provided for one photoreceptor, and the toner images sequentially formed on the photoreceptor are primarily transferred onto an intermediate transfer body, and then superimposed on the intermediate transfer body. The image forming apparatus may employ a method of secondary transfer of the combined toner image onto a transfer material. In other words, the intermediate transfer member as the image carrier may be one that conveys the toner image, which is primarily transferred from another image carrier that carries the toner image, so as to secondarily transfer the toner image onto the recording material.

Further, the present invention is not limited to application to notification of the life of an intermediate transfer member as an image carrier. For example, it can be applied to a photoreceptor (photoreceptor drum, photoreceptor belt, etc.) having an uneven surface, and similar effects can be obtained. In the image forming apparatus, at least part of the lifetime of the image carrier, diffraction occurs on the surface of the image carrier due to irradiation light from the optical sensor, and part of the diffracted light is out of the light receiving range of the optical sensor, or The present invention can be applied as long as it is configured to fall within the light receiving range of the optical sensor.

REFERENCE SIGNS LIST 1 photosensitive drum 7 optical sensor 8 intermediate transfer belt 12 belt unit 20 belt cleaning device 21 cleaning blade

Claims (15)

an image carrier that carries a toner image;
an optical sensor that irradiates the surface of the image carrier with light and detects reflected light;
a control means capable of executing processing for informing information about the life of the image carrier;
In an image forming apparatus having
During at least part of the lifetime of the image carrier, the irradiation light from the optical sensor diffracts on the surface of the image carrier, and part of the diffracted light goes out of the light receiving range of the optical sensor, or It is configured to be within the light receiving range of the optical sensor,
The control means obtains a first detection result of the optical sensor obtained by irradiating the surface of the image carrier with a predetermined irradiation light amount from the optical sensor at a first timing, and a second detection result of the optical sensor obtained by irradiating the image carrier with the predetermined irradiation light amount from the optical sensor at a second timing afterward; configured to perform the processing;
The optical sensor is capable of receiving specularly reflected light from the surface of the image carrier, and the control means executes the processing based on the index indicating the amount of increase in specularly reflected light received by the optical sensor. An image forming apparatus characterized by : an image carrier that carries a toner image;
an optical sensor that irradiates the surface of the image carrier with light and detects reflected light;
a control means capable of executing processing for informing information about the life of the image carrier;
In an image forming apparatus having
During at least part of the lifetime of the image carrier, the irradiation light from the optical sensor diffracts on the surface of the image carrier, and part of the diffracted light goes out of the light receiving range of the optical sensor, or It is configured to be within the light receiving range of the optical sensor,
The control means obtains a first detection result of the optical sensor obtained by irradiating the surface of the image carrier with a predetermined irradiation light amount from the optical sensor at a first timing, and a second detection result of the optical sensor obtained by irradiating the image carrier with the predetermined irradiation light amount from the optical sensor at a second timing afterward; configured to perform the processing;
The optical sensor is capable of receiving diffusely reflected light from the surface of the image carrier, and the control means executes the processing based on the index indicating the amount of decrease in the diffusely reflected light received by the optical sensor. An image forming apparatus characterized by: 3. The image forming apparatus according to claim 1 , wherein the controller executes the processing when the index exceeds a predetermined threshold. 4. The image forming apparatus according to claim 1 , wherein the index is a rate of change between the first detection result and the second detection result. 5. The image forming apparatus according to claim 1, wherein said optical sensor also serves as means for detecting a test toner image formed on said image carrier. The optical sensor also serves as means for detecting a test toner image formed on the image carrier, and the predetermined irradiation light amount is different from the irradiation light amount when the optical sensor detects the test toner image. The image forming apparatus according to any one of claims 1 to 4 , characterized by: 7. The image forming apparatus according to claim 5 , wherein the test toner image is a test toner image for image density control or color misregistration correction control. It has cleaning means for cleaning the optical sensor,
8. The control means executes the processing based on the detection result of the optical sensor within a predetermined period after the optical sensor has been cleaned by the cleaning means. The image forming apparatus according to any one of . 8. The image carrier is an intermediate transfer member for conveying a toner image, which is primarily transferred from another image carrier carrying a toner image, to a recording material for secondary transfer. The image forming apparatus according to any one of . A plurality of grooves are formed on the surface of the image carrier along the direction of movement of the surface of the image carrier and arranged side by side in the width direction of the image carrier intersecting the direction of movement. The image forming apparatus according to any one of claims 1 to 9 . 11. The image forming apparatus according to claim 10 , wherein the average value of the intervals between adjacent grooves is 2 [mu]m or more and 10 [mu]m or less. 12. The image forming apparatus according to claim 10 , wherein intervals between adjacent grooves are substantially the same. The image carrier has a first region and a second region shorter than the first region with respect to the moving direction, and the first region and the second region are adjacent to each other with the grooves At least one of an average value of the interval between grooves and an average value of the depth of the groove is different, and the control means executes the processing based on the detection result of the optical sensor regarding the first region. 11. The image forming apparatus according to claim 10 . 14. The image forming apparatus according to claim 13 , wherein an average value of intervals between adjacent grooves in the first region is 2 [mu]m or more and 10 [mu]m or less. 15. The image forming apparatus according to claim 13 , wherein intervals between adjacent grooves in the first region are substantially the same.

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