JP2021009207A - Image forming apparatus - Google Patents

Abstract

To provide an image forming apparatus that can determine or notify of information on the life of an image carrier having a rugged shape formed on its surface.SOLUTION: An image forming apparatus 100 having an image carrier 8, an optical sensor 7, and control means 302 that can execute processing for notifying information on the life of the image carrier is configured such that in at least part of the life period of the image carrier, irradiation light from the optical sensor causes diffraction on a surface of the image carrier, and part of diffraction light falls out of a light receiving range of the optical sensor or falls within the light receiving range of the optical sensor. The control means 302 executes the processing based on a result of detection performed by the optical sensor acquired by the optical sensor irradiating the surface of the image carrier with light.SELECTED DRAWING: Figure 8

Description

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

Conventionally, for example, as an image forming apparatus using an electrophotographic method, there is an intermediate transfer type image forming apparatus provided with an intermediate transfer body. In this image forming apparatus, the toner image formed on the photoconductor is first transferred to the intermediate transfer body at the primary transfer unit, and then the toner image on the intermediate transfer body is secondarily transferred to the recording material at the secondary transfer unit. .. As the intermediate transfer body, an intermediate transfer belt formed of an endless belt is widely used.

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

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. Granting is being done. For example, Patent Document 1 discloses that a lapping film is brought into contact with the surface of an intermediate transfer belt to form a groove on the surface of the intermediate transfer belt. The grooves are in a positional relationship substantially orthogonal to the longitudinal direction of the contact portion between the cleaning blade and the intermediate transfer belt, and the average distance between the grooves is 10 μm to 100 μm.

On the other hand, the intermediate transfer belt needs to be replaced at an appropriate timing before the desired performance cannot be obtained due to scratches on the surface or contamination by deposits due to use. In general, the degree to which scratches or the like occur 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 prints and the usage time. Patent Document 2 discloses a configuration in which an optical sensor is used to monitor the formation of a toner filming layer on an intermediate transfer belt and the surface roughness of the intermediate transfer belt to determine the replacement time of the intermediate transfer belt. There is.

JP-A-2015-125187 Japanese Patent No. 3143200

However, the method or configuration for determining the replacement time of the intermediate transfer belt having the uneven shape formed on the surface as shown in Patent Document 1 has not been sufficiently studied.

Therefore, an object of the present invention is to provide an image forming apparatus capable of determining or notifying information on the life of an image carrier having an uneven shape formed on the surface.

The above object is achieved by the image forming apparatus according to the present invention. In summary, the present invention conveys information about an image carrier that carries a toner image, an optical sensor that irradiates the surface of the image carrier with light to detect reflected light, and the life of the image carrier. In an image forming apparatus having a control means capable of carrying out the above-mentioned processing, diffraction occurs on the surface of the image carrier due to the irradiation light from the optical sensor during at least a part of the life period of the image carrier. A part of the diffracted light is configured to be out of the light receiving range of the optical sensor or within the light receiving range of the optical sensor, and the control means irradiates the surface of the image carrier with light by the optical sensor. The image forming apparatus is characterized in that the processing is executed based on the detection result of the optical sensor acquired in the above-mentioned.

According to the present invention, it is possible to provide an image forming apparatus capable of determining or notifying information on the life of an image carrier having an uneven shape formed on the surface.

It is a schematic sectional view of an image forming apparatus. It is a schematic block diagram which shows the control mode of the main part of an image forming apparatus. It is a schematic enlarged partial cross-sectional view and a schematic top view of an intermediate transfer belt. It is a schematic cross-sectional view of an optical sensor and the explanatory view of a reflection type diffraction grating. It is a graph which shows the relationship between the average groove spacing of an intermediate transfer belt, and a diffraction angle. It is a graph which shows the BRDF of the intermediate transfer belt. It is a graph which shows the relationship between the groove depth and the amount of reflected light of an optical sensor. It is a graph which shows the transition of the output of an optical sensor and the groove depth in a durability test. It is a flowchart of the control of Example 1. FIG. It is the schematic diagram of the cleaning mechanism and the flowchart of the control when the cleaning mechanism is provided. It is a schematic perspective view of the intermediate transfer belt of Example 2. 11 is a schematic enlarged partial cross-sectional view of regions X and Y in FIG. It is a graph which shows the output waveform of the optical sensor about the intermediate transfer belt of Example 2. It 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. 1. Overall Configuration and Operation of the Image Forming Device FIG. 1 is a schematic cross-sectional view of the image forming device 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 can form a full-color image using an electrophotographic method.

The 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. For elements having the same or corresponding functions or configurations at each station 10Y, 10M, 10C, and 10K, Y, M, C, and K at the end of the code indicating that they are elements for any color are omitted. There is a general explanation. 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.

The photosensitive drum 1, which is a rotatable drum-shaped (cylindrical) photoconductor (electrophotographic photosensitive member) as the first movable image carrier that supports the toner image, is a drive motor as a driving means (FIG. FIG. (Not shown), it is rotationally driven in the direction of arrow R1 (clockwise) in the figure. The surface of the rotating photosensitive drum 1 is charged to a predetermined potential having a predetermined polarity (negative electrode property in this embodiment) by a charging roller 2, which is a roller-shaped charging member as a charging means. During the charging process, a predetermined charging voltage (charging bias) is applied to the charging roller 2 by a charging power source (not shown). The surface of the charged photosensitive drum 1 is scanned and exposed by an exposure apparatus 3 as an exposure means according to image information, and an electrostatic latent image (electrostatic image) is formed on the photosensitive drum 1. In this embodiment, the exposure apparatus 3 is composed of a scanner unit that scans a laser beam with a multi-sided mirror, and irradiates a 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 the developing apparatus 4 as a developing means, and a toner image (toner image) is formed on the photosensitive drum 1. Will be done.

An intermediate transfer belt 8 which is an intermediate transfer body composed of an endless belt as a movable second image carrier is arranged so as to face the four photosensitive drums 1. The intermediate transfer belt 8 is stretched on a drive roller 9a, a tension roller 9b, and a secondary transfer opposed roller (secondary transfer inner roller) 9c as a plurality of support rollers (tension rollers). The intermediate transfer belt 8 is rotationally driven by a drive motor (not shown) as a drive means to transmit a driving force, and moves around in the arrow R2 direction (counterclockwise direction) in the drawing (counterclockwise direction). Rotate. The intermediate transfer belt 8 will be described in more detail later. On the inner peripheral surface side of the intermediate transfer belt 8, a primary transfer roller 5 which is a roller-shaped primary transfer member as a primary transfer means is arranged. 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 in which the photosensitive drum 1 and the intermediate transfer belt 8 come into contact with each other. The toner image formed on the photosensitive drum 1 as described above is first transferred to the intermediate transfer belt 8 which is moving around by the action of the primary transfer roller 5 in the primary transfer unit N1. At the time of primary transfer, the primary transfer power supply E1 is applied to the primary transfer roller 5 to supply a primary transfer voltage (primary transfer bias) opposite to the normal charge polarity (charge polarity during development) of the toner (positive polarity in this embodiment). ) Is applied. For example, at the time of forming a full-color image, the toner images of each color of Y, M, C, and K formed on each photosensitive drum 1 are sequentially transferred so as to be superimposed on the intermediate transfer belt 8 in each primary transfer unit N1. Toner.

On the outer peripheral surface side of the intermediate transfer belt 8, at a position facing the secondary transfer facing roller 9c, a secondary transfer roller (secondary transfer outer roller) 11 which is a roller-shaped secondary transfer member as a secondary transfer means. Is placed. The secondary transfer roller 11 is pressed toward the secondary transfer opposed roller 9c via the intermediate transfer belt 8 and is in contact with the intermediate transfer belt 8 and the secondary transfer roller 11 (secondary transfer nip). Form N2. The toner image formed on the intermediate transfer belt 8 as described above is sandwiched and conveyed between the intermediate transfer belt 8 and the secondary transfer roller 11 by the action of the secondary transfer roller 11 in the secondary transfer unit N2. Secondary transfer is performed on the recording material (transfer material, sheet) P such as the paper being used. At the time of secondary transfer, a secondary transfer voltage (secondary transfer bias) opposite to the normal charging polarity of the toner is applied to the secondary transfer roller 11 by the secondary transfer power supply E2. The recording material P is sent out from the recording material storage unit by a feeding roller or the like in a feeding and transporting device (not shown), and is conveyed by the feeding roller or the like. Then, the recording material P is conveyed to the secondary transfer unit N2 by the resist roller pair 13 at the same timing as the toner image on the intermediate transfer belt 8.

The recording material P to which the toner image is transferred is conveyed to the fixing device 14 as a fixing means. The fixing device 14 heats and pressurizes the recording material P by the endless fixing film 14a containing a heat source and the pressure roller 14b to fix (melt, fix) the toner image on the surface of the recording material P. 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.

Further, the toner remaining on the photosensitive drum 1 during the primary transfer (primary transfer residual toner) is removed from the photosensitive drum 1 and recovered by the drum cleaning device 6 as a photoconductor cleaning means. The drum cleaning device 6 scrapes the primary transfer residual toner from the surface of the rotating photosensitive drum 1 by a cleaning blade 61 as a cleaning member arranged in contact with the surface of the photosensitive drum 1, and inside the cleaning container 62. To house in. Further, on the outer peripheral surface side of the intermediate transfer belt 8, as an intermediate transfer body cleaning means, downstream of the secondary transfer portion N2 and upstream of the primary transfer portion N1 (uppermost stream primary transfer portion N1Y) in the belt transport 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 via the intermediate transfer belt 8. The toner (secondary transfer residual toner) and paper dust remaining on the intermediate transfer belt 8 during the secondary transfer are removed from the intermediate transfer belt 8 by the belt cleaning device 20 and recovered. The belt cleaning device 20 uses a cleaning blade 21 as a cleaning member arranged in contact with the surface of the intermediate transfer belt 8 to scrape the secondary transfer residual toner and the like from the surface of the intermediate transfer belt 8 that is moving around. , It 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 a waste toner box (not shown) by the recovered toner conveying means (not shown) and stored.

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

Further, the intermediate transfer belt 8 supported by the three tension rollers 9a, 9b, 9c, each primary transfer roller 5, the belt cleaning device 20, and the like are integrally unitized to form the belt unit 12. The belt unit 12 is removable from the device main body 110. The belt unit 12 is replaced with a new one when the intermediate transfer belt 8 has reached the end of its useful life.

Further, in this embodiment, the developing apparatus 4 uses a non-magnetic one-component developer as the developing agent. The developing apparatus 4 includes a developing roller 41 as a developing agent carrier, a developing container 42 for accommodating a developing agent, a developing blade 43 as a developing agent regulating means, and the like. In this embodiment, the charge polarity of the photosensitive drum 1 (negative electrode in this embodiment) is applied to the exposed portion (image portion) on the photosensitive drum 1 whose absolute potential value is lowered by being exposed after being uniformly charged. Toner charged with the same polarity as the property) adheres (inverted development). The toner in the developing container 42 is negatively charged by the developing blade 43 and applied onto the developing roller 41. At the time of development, the developing roller 41 carrying the toner is brought into contact with or brought close to the photosensitive drum 1, and a predetermined negative developing voltage (development bias) is applied to the developing roller 41 by a developing power source (not shown). To.

The toner used in this example 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. The average particle size is, for example, the weight average particle size, and can be measured by the Coulter method. For measurement, "Coulter Counter Multisizer 3" (manufactured by Beckman Coulter Co., Ltd.) and the attached dedicated software "Beckman Coulter Multisizer 3 Version 3.51" (Beckman Coulter Co., Ltd.) for setting measurement conditions and analyzing measurement data It can be done using (made by the company) and. The method for producing the toner particles is not limited to the emulsion polymerization aggregation method, and the toner particles can be produced by other methods such as a pulverization method, a suspension polymerization method, and a dissolution suspension method.

Further, in the present embodiment, the cleaning blade 21 of the belt cleaning device 20 is configured by adhering an elastic blade made of an elastic material to a support sheet metal as a support member. In this embodiment, a galvanized steel plate having a substantially rectangular plate shape was used as the support sheet metal. Further, in this embodiment, as the elastic blade, a urethane rubber blade having a substantially rectangular plate shape using urethane rubber (polyurethane) as an elastic material was used. The cleaning blade 21 is arranged so as to be in the counter direction with respect to the belt transport direction, and the edge portion of the free end portion thereof 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 (for example, two) of the optical sensors 7 may be arranged along a direction substantially orthogonal to the belt transport direction (hereinafter, also referred to as a “belt width direction”). Further, in this embodiment, the optical sensor 7 is arranged at a position facing the drive roller 9a as an opposing member via the intermediate transfer belt 8. Then, the optical sensor 7 detects the surface state 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 in more detail later.

2. 2. Control mode FIG. 2 is a schematic block diagram showing a control mode of a main part of the image forming apparatus 100 of this embodiment. The image forming apparatus 100 has a printer control unit 300. The printer control unit 300 includes a printer controller 301, an engine control unit 302, a non-volatile memory 303, an energization control unit 304, an image formation control unit 305, an exchange detection unit 306, and the like. Further, 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. Further, the printer controller 301 expands the received image data into information capable of forming an image by the image forming apparatus 100, and exchanges signals and serially communicates with the engine control unit 302. The engine control unit 302 exchanges signals with the printer controller 301, and controls each unit of the energization control unit 304, the image formation control unit 305, and the printer engine via serial communication. Here, the printer engine is a general term for a mechanism unit that forms an image on the recording material P and outputs the image in the above-mentioned process. When the engine control unit 302 is instructed to start the image formation operation, the engine control unit 302 controls each unit of the energization control unit 304, the image formation control unit 305, and the printer engine, and the recording material P at a predetermined process speed by the above-mentioned process. To perform image formation to form and output an image. The engine control unit 302 as a control means includes a CPU as an arithmetic control means, a ROM or RAM as a storage means, and the like.

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

Further, the belt unit 12 is provided with a non-volatile memory (memory tag) 307 for identification as an identification means. When the belt unit 12 is attached to the apparatus main body 110, the identification non-volatile memory 307 is communicably connected to the printer control unit 300. The replacement detection unit 306 confirms 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. Then, the replacement detection unit 306 can detect whether the belt unit 12 is new or the belt unit 12 has been replaced. The detection result (output signal) of the replacement detection unit 306 is input to the engine control unit 302.

Further, in this embodiment, the printer control unit 300 is connected to the operation unit (control panel) 308 provided in the device main body 110. The 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 person, and operation buttons for inputting information such as various settings to the printer control unit 300 by the operator. It is configured to have an input means of. The operation unit 308 may be composed of a touch panel or the like having the functions of a display means and an input means.

3. 3. Intermediate transfer body Next, the intermediate transfer belt 8 in this example 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 orthogonal to the belt transport direction (viewed along the belt transport direction). (B) is a schematic top view of the surface of the intermediate transfer belt 8 as viewed 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 (outer peripheral surface) of the intermediate transfer belt 8 and carries the toner transferred from the photosensitive drum 1.

In this embodiment, the base layer 81 is a layer having a thickness of about 70 μm in which carbon black is dispersed as an electric resistance adjusting agent in a polyethylene naphthalate resin. In this embodiment, polyethylene naphthalate resin is used as the material of the base layer 81, but the present invention is not limited to this. In the case of a thermoplastic resin, for example, materials such as polyimide, polyester, polycarbonate, polyarylate, acrylonitrile-butadiene-styrene copolymer (ABS), polyphenylene sulfide (PPS), polyvinylidene fluoride (PVdF), and a mixed resin thereof. May be used. As the electric 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 in which, for example, zinc oxide is dispersed as an electric resistance adjusting agent in an acrylic resin as a base material. The surface layer 82 is preferably a resin material (curable resin) among the curable materials from the viewpoint of strength such as abrasion resistance and crack resistance, and among the curable resins, the acrylic co-weight containing an unsaturated double bond. Acrylic resin obtained by curing the coalescence is preferable. As the electric 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 is likely to be rolled up and worn due to repeated use of the cleaning blade 21. The winding of the cleaning blade 21 means that the free end portion of the cleaning blade 21 that is in contact with the belt transport direction in the counter direction is rolled so as to be in contact with the belt transport direction.

Therefore, in this embodiment, the surface of the intermediate transfer belt 8 is subjected to fine unevenness processing, and the average groove spacing I in the belt width direction is 2 μm or more and 10 μm or less along the belt transport direction. Shape, groove portion) 83 are formed side by side. In this embodiment, the grooves 83 exist in substantially the entire circumferential direction (belt transport direction) of the intermediate transfer belt 8. Further, in this embodiment, the grooves 83 exist in substantially the entire width direction (belt width direction) of the intermediate transfer belt 8. In the belt width direction, the groove 83 covers substantially the entire area where the cleaning blade 21 and the intermediate transfer belt 8 abut (that is, a region equal to or larger than the width of the area where the cleaning blade 21 and the intermediate transfer belt 8 abut). It suffices if it is formed.

As the fine unevenness forming means, polishing, cutting, imprinting, and the like are generally known, and can be appropriately selected and used so that a desired average groove spacing I can be obtained. In this embodiment, from the viewpoint of processing cost and productivity, imprint processing utilizing the photocurability of acrylic resin, which is the base material of the surface layer of the intermediate transfer belt 8 to be subjected to fine uneven processing, is adopted.

In the imprinting process, a mold (not shown) having a fine uneven shape opposite to the uneven shape 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 a convex portion is formed substantially parallel to the rotation direction of the cylinder. Thereby, by transferring the fine uneven shape of the mold to the surface of the surface layer 82 of the intermediate transfer belt 8, a desired uneven shape 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 groove 83 on the surface of the intermediate transfer belt 8 is the width of the opening in a direction substantially orthogonal to the longitudinal axis direction of the groove 83, and is a groove with respect to the outermost surface 84 of the surface layer 82. Is defined as a range in which the thickness of the surface layer 82 is formed thin. In this embodiment, the groove width W is the width of the opening of the groove 83 in a direction substantially orthogonal to the belt transport 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, and more preferably less than half the average particle size of the toner. By making the groove width W smaller than the average particle size of the toner, it is possible to prevent the toner from entering the groove 83 and slipping through the cleaning blade 21. Further, the groove width W of the intermediate transfer belt 8 is preferably 0.5 μm or more from the viewpoint of suppressing the protrusion of the mold from falling. In the configuration of this example, the groove width W of the intermediate transfer belt 8 is preferably in the range of 0.5 μm or more and 6 μm or less, and more preferably in the range of 1 μm or more and 2 μm or less.

Further, the depth (groove depth) D of the groove 83 on the surface of the intermediate transfer belt 8 is from the opening of the groove 83 (the position of the outermost surface 84) to the bottom of the groove 83 in the thickness direction of the intermediate transfer belt 8. Is defined as the depth of. In this embodiment, the groove depth D is 0.45 μm at the initial stage of use (when new) of the intermediate transfer belt 8. 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 recesses may easily disappear due to scraping of the surface layer of the intermediate transfer belt 8, or cleaning defects may easily occur as 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 not to reach the base layer 81 but to exist only in the surface layer 82. 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 reducing durability due to being too thin and suppressing cracking of the surface layer due to being too thick. It is about 3 μm or less.

Further, the spacing (groove spacing) I of the grooves 83 on the surface of the intermediate transfer belt 8 is one end of the opening of the adjacent groove 83 in a direction substantially orthogonal to the longitudinal axis direction of the groove 83 (in the illustrated example). It is defined as the distance between the leftmost part). In this embodiment, the groove spacing I is the spacing between one end of the opening in a direction substantially orthogonal to the belt transport direction. In this embodiment, the average groove spacing I is 3.5 μm by forming the grooves 83 at an equal pitch of 3.5 μm (substantially the same groove spacing) over substantially the entire area in the belt width direction. The groove spacing I may be defined as the spacing between the right ends of the openings of the adjacent grooves 83 in the drawing, or may be defined as the spacing between the bottoms of the adjacent grooves 83. The average groove spacing 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 preferably in the range of 3 μm or more and 4 μm or less. Is more preferable. If the average groove spacing I is too small, it may be difficult to form a uniform uneven shape. Further, if the average groove spacing I is too large, it may be difficult to suppress the wear of the cleaning blade 21.

Here, in this embodiment, the groove 83 is formed substantially parallel to the belt transport direction as a direction along the belt transport direction (FIG. 3 (b)). Further, in the present embodiment, the groove 83 is formed in a substantially linear shape continuously over one circumference in the circumferential direction (rotational direction) of the intermediate transfer belt 8. However, the direction along the belt transport direction may extend along the direction intersecting with the belt width direction, and may have an angle with respect to the belt transport direction (FIG. 14). The angle formed by the longitudinal axis direction of the groove 83 with respect to the belt transport direction is preferably 45 degrees or less, more preferably 10 degrees or less. Typically, as in this embodiment, the belt transport direction and the longitudinal axis direction of the groove 83 are substantially parallel. For the groove 83 having an angle with respect to the belt transport direction, a mold having a convex portion formed diagonally with respect to the rotation direction of the cylinder may be used, or a convex portion substantially parallel to the rotation direction of the cylinder similar to this embodiment. It can be formed by using the mold in which the above is formed at an angle with respect to the belt transport direction.

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

Further, in this embodiment, as the optical sensor 7 for detecting the surface state of the intermediate transfer belt 8, the optical sensor 7 for detecting the test toner image for the density correction control and the color shift correction control is also used. That is, in this embodiment, the optical sensor 7 also has a function as a density sensor for density correction control and a color shift detection sensor for color shift correction control.

Generally, in an electrophotographic image forming apparatus, the image density and the image forming position between each image forming unit fluctuate depending on various conditions such as a change in the environment in which the image is used and a cumulative number of prints. If the fluctuation becomes excessive, it becomes impossible to obtain a high-quality image without color shift of the original correct color tone. Therefore, in the image forming apparatus 100 of the present embodiment, a test toner image (patch) is experimentally formed on the intermediate transfer belt 8 with toner of each color, and the density of the test toner image (toner loading amount) is formed on the intermediate transfer belt 8. ) Or the misalignment of the test toner image is detected by using the optical sensor 7. Then, based on the detection result, density correction control for giving feedback to the exposure amount, development bias, etc., or color shift correction control for changing the writing timing of the laser beam of the exposure device 3 for each color is performed. As a result, stable and high-quality images can be obtained.

FIG. 4A is a schematic cross-sectional view of the optical sensor 7. The optical sensor 7 includes a light emitting element 71 composed of an LED (light emitting diode) or the like, a specular reflection light receiving element 72 composed of a photodiode or the like, and a diffuse reflection light receiving element 73 composed of a photodiode or the like. .. Further, the optical sensor 7 has a holder 74, a protective cover (or a molded lens portion) 75 capable of transmitting light, 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. Light is received by the light receiving element 72 and the diffuse reflection light receiving element 73. The specular reflection light receiving element 72 and the diffuse reflection light receiving element 73 each output an electric signal according to the amount of received light. The detection result (output signal) of the optical sensor 7 is input to the engine control unit 302. Thereby, based on the ratio or difference of the reflectance of the test toner image T with respect to the surface characteristics of the intermediate transfer belt 8 or the reflectance of the intermediate transfer belt 8, the concentration 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 having a center wavelength of λ = 840 nm was used as the light emitting element 71. Then, 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 angle of incident θi = −20 °. Further, 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 at an angle of + 20 ° and the diffuse reflection light receiving element 73 is at an angle of 0 °. It is configured to receive the 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 a specular reflection component and a diffuse reflection (diffusion) component. The specular reflection light receiving element 72 receives the reflected light including 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-concentration test toner image T is formed on the intermediate transfer belt 8 and the surface of the intermediate transfer belt 8 is coated, the light is blocked by the toner, the specular reflected light is reduced, and the specular light receiving element 72 The output drops. On the other hand, since the yellow, magenta, and cyan toners have the characteristic of being diffusely reflected with respect to the 840 nm infrared light used in this example, when the amount of toner adhered to the intermediate transfer belt 8 increases, the yellow, magenta, and cyan toners become With respect to cyan, the output of the diffuse reflection light receiving element 73 increases. By using the difference obtained by subtracting the output of the diffuse reflection light receiving element 73 from the output of the specular reflection light receiving element 72, the reflected light amount of only the specular reflection component can be obtained. In this embodiment, by detecting both the amount of specularly reflected light (intensity) and the amount of diffusely reflected light (intensity) in this way, it is possible to accurately detect the density from high density to low density. There is. Further, the optical sensor 7 cannot distinguish the color of the toner on the intermediate transfer belt 8. Therefore, a test toner image T for detecting the gradation of the toner image of each single color is formed on the intermediate transfer belt 8.

5. Diffraction Phenomenon FIG. 4B is a schematic diagram for explaining a diffraction phenomenon by a reflective diffraction grating. Generally, the lattice spacing is d, the ray wavelength is λ, the incident angle of the ray with respect to the normal direction of the diffraction grating is θi, the reflection angle is θm, and the diffraction order is m (m = ± 0, ± 1, ± 2, ... The equation indicating the diffraction angle from the reflection type diffraction grating is expressed by the following (Equation 1) when the positive and negative integers of.
d [sin (θi) + sin (θm)] = mλ (Equation 1)

When m = 0 (that is, in the case of specular reflection), θi = −θm, and the specularly reflected light does not depend on the lattice spacing d and the ray wavelength λ.

In the case of other orders, the reflected light strengthens each other at an angle θm in which the optical path difference of each reflected light becomes an integral multiple of the wavelength, depending on the lattice spacing d and the ray wavelength λ. When (Equation 1) is expanded for the diffraction angle θm, it is expressed by the following (Equation 2).
sinθm = mλ / d-sinθi (Equation 2)

Then, if the incident angle with respect to the normal of the irradiation surface is defined as negative, the following tendency is shown.
・ The larger the incident angle θi, the larger the right side of (Equation 2) and the larger the diffraction angle θm. ・ The larger the ray wavelength λ, the larger the right side of (Equation 2) and the larger the diffraction angle θm. ・ Lattice spacing d The smaller the value, the larger the right side of (Equation 2) and the larger the diffraction angle θm.

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

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

In this embodiment, the range of the specularly reflected light received by the specularly reflected light receiving element 72 of the optical sensor 7 is the range of 20 ° ± 5 ° shown by the broken line in FIG. Focusing on this range, it can be seen that when the average groove spacing I is reduced to 50 μm, the -5th order diffracted light is out of the light receiving range. As the average groove spacing I becomes smaller, lower-order diffracted light is out of the light receiving range. Then, when the average groove spacing I in this embodiment is reduced to 3.5 μm (the leftmost points in FIG. 5), the reflected light (that is, the regular reflected light) other than the 0th-order reflected light (that is, the regular reflected light) is reduced. It can be seen that all the diffracted light) is out of the light receiving range. On the other hand, in this embodiment, the light receiving range of the diffusely reflected light by the diffusely reflected light receiving element 73 of the optical sensor 7 is the range of 0 ° ± 5 degrees shown by the alternate long and short dash line in FIG. Focusing on this range, it can be seen that, for example, at 3.5 μm (each leftmost point in FIG. 5), which is the average groove spacing I in this example, -1st order diffracted light is mixed.

Here, an image forming apparatus using an image carrier whose diffraction is generated by the irradiation light from the optical sensor 7 is defined as follows. That is, during at least a part of the life of the image carrier, diffraction occurs on the surface of the image carrier due to the irradiation light from the optical sensor 7, and a part of the diffracted light is in the light receiving range of the optical sensor 7 (specular reflection light receiving range). ), Or an image forming apparatus having a configuration that may enter the light receiving range (diffraction reflection light receiving range) of the optical sensor 7.

6. Scattering Characteristics of Diffracted Light FIG. 6 is a graph showing the angular distribution characteristics of scattered light obtained as follows (hereinafter, the acronym for the bidirectional reflectance distribution function is referred to as “BRDF”). In the BRDF (solid line) of FIG. 6, light of λ = 622 nm is incident on the surface of the intermediate transfer belt 8 in which the uneven shape having an average groove spacing I of 3.7 μm is formed in the same manner as in this embodiment. It was obtained by irradiating at °. The BRDF measurement was performed using a small simple scattering measuring device Mini-Diff V1 manufactured by Cybernet Co., Ltd. In FIG. 6, as a comparative example, the BRDF of a belt (hereinafter referred to as “coat belt”) that is simply coated with an acrylic resin before the surface is subjected to fine unevenness processing is also shown by a broken line.

As can be seen from FIG. 6, the BRDF of the coat belt has a diffuse reflection component broadly spread with respect to the peak of the specular light. On the other hand, in the BRDF of the intermediate transfer belt 8 that has been subjected to fine unevenness processing, diffraction occurs in which the amount of specular reflected light of the 0th order is reduced and the amount of reflected light is increased at a periodic angle. Further, the intensity of the diffracted light decreases as the order m increases. That is, with respect to the specularly reflected light, when the surface of the intermediate transfer belt 8 that has been subjected to fine unevenness processing with the same amount of irradiation light is irradiated with light, the smaller the average groove spacing I, the more low-order diffracted light 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 groove depth D and the amount of specularly reflected light and diffusely reflected light when the optical sensor 7 of this embodiment is used. In FIG. 7, the horizontal axis represents the groove depth D, and the vertical axis represents the output of the specular reflection light receiving element 72 (specular reflection light amount) and the output of the diffuse reflection light receiving element 73 (diffuse reflection light amount) of the optical sensor 7. Here, an intermediate transfer belt 8 (groove depth D = 0.15 μm, obtained by adjusting the photocuring conditions of the acrylic resin and the transfer pressure during imprinting) having uneven shapes having different groove depths D on the surface. (3 levels of 0.30 μm and 0.40 μm) and a coat 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 was irradiated with the same amount of irradiation light was compared.

As shown in FIG. 7, as the groove depth D decreased, the reflected light amount increased with respect to the specularly reflected light, and the reflected light amount decreased with respect to the diffusely reflected light. It is considered that this is because, as can be seen from the BRDF of FIG. 6, as the groove depth D becomes smaller, the diffracted light decreases and approaches the reflected light amount of the coat belt. This was also consistent with the behavior known in the laminar diffraction grating in which the diffraction efficiency changes depending on the groove depth and the duty ratio (groove width with respect to the groove period).

8. Relationship between Change in Output of Optical Sensor and Change in Groove Depth Due to Use of Intermediate Transfer Belt FIG. 8 shows the relationship between the number of prints and the amount of specularly reflected light and diffusely reflected light in the image forming apparatus 100 of this embodiment. It is a graph diagram. In FIG. 8, the horizontal axis represents the number of prints, and the vertical axis represents the output of the specular reflection light receiving element 72 (specular reflection light amount) and the output of the diffuse reflection light receiving element 73 (diffuse reflection light amount) of the optical sensor 7. Here, in an environment of a temperature of 23 ° C. and a relative humidity of 50%, four text patterns with a printing rate (image ratio) of 5% for each color are intermittently used using an Extra basis weight 80 g / m ² manufactured by OCE and A4 paper. A durability test was conducted to output with. The four-sheet intermittent is an output method in which a job of forming an image on four recording materials P and outputting the image is repeated at predetermined time intervals. Then, the surface of the intermediate transfer belt 8 is irradiated with light from the optical sensor 7 with the same irradiation light amount for each predetermined number of prints (about 5000 sheets), and the transition of the reflected light amount from the initial use of the intermediate transfer belt 8 and the transition of the reflected light amount from the initial use of the intermediate transfer belt 8 The transition of the average groove depth D from the initial use of the intermediate transfer belt 8 was measured. At each measurement timing, the amount of specularly reflected light and the amount of diffusely reflected light were measured as average values for one round of the intermediate transfer belt 8. 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 for the intermediate transfer belt 8 to decrease for a while from the initial use, but then to increase monotonically. On the other hand, focusing on the amount of diffusely reflected light, although it increased slightly from the initial use of the intermediate transfer belt 8, it tended to decrease monotonically thereafter. In addition, focusing on the average groove depth D, there was a tendency for the specular reflection to increase and the diffuse reflection to decrease in good agreement.

From the above results, the following can be seen. That is, at the initial stage of use of the intermediate transfer belt 8, the irradiation light of the optical sensor 7 is slightly absorbed by the filming due to the adhesion of the toner wax component and the discharge product to the intermediate transfer belt 8, and the amount of specular reflected light decreases. .. However, after that, as the groove depth D changes (decreases) due to the wear of the surface layer 82 of the intermediate transfer belt 8, the reflection from the smooth surface described in FIG. 5 approaches, and the intensity of the diffracted light decreases to be positive. It is probable that the amount of reflected light increased. Generally, in the case of the smooth intermediate transfer belt 8, when the surface of the intermediate transfer belt 8 is irradiated with light with the same irradiation light amount, the specular reflected light decreases with the use of the intermediate transfer belt 8. On the other hand, the increase in the specularly reflected light in this example is considered to indicate that the groove depth D on the surface of the intermediate transfer belt 8 is purely small. Therefore, the groove depth D can be estimated based on the change (rate of change, amount of change) of the specular reflected light amount from the initial value.

Here, the cleaning blade 21 has an appropriate degree of contact with the intermediate transfer belt 8 because a lubricating layer is formed on the contact portion (cleaning nip portion) with the intermediate transfer belt 8 with toner or an external additive thereof. The frictional force is maintained and appropriate cleaning performance can be exhibited. When the groove depth D on the surface of the intermediate transfer belt 8 is equal to or less than a predetermined value, the toner or the component of the external additive clogged in the groove 83 may break the lubricating layer of the cleaning nip portion. Further, when the lubricant layer is broken, 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 chipped. Therefore, if the groove depth D is equal to or less than a predetermined value, a cleaning defect may occur. In fact, in the above durability test, when the number of printed sheets finally reaches 350,000 (when the groove depth D in FIG. 8 is indicated by ▲), the cleaning performance becomes below the permissible limit and cleaning failure occurs. Occurred.

The average groove depth D of the intermediate transfer belt 8 used in the above durability test at the initial stage of use is 0.45 μm, and the average groove depth D at the time when a cleaning failure occurs is less than 0.2 μm. It was. Further, in the above durability test, the average value of the output (specular reflected light amount) of the specular reflection light receiving element 72 in one round of the intermediate transfer belt 8 is 1.6V at the initial stage of use of the intermediate transfer belt 8, resulting in poor cleaning. It was 2.6V at the time of occurrence.

9. Life detection of the intermediate transfer belt In this embodiment, in the configuration using the intermediate transfer belt 8 in which an uneven shape is formed on the surface and diffraction is generated by the irradiation light from the optical sensor 7, the groove depth due to the use of the intermediate transfer belt 8 is used. 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 D. Then, when it is determined that the intermediate transfer belt 8 has reached the end of its life, a process for notifying an operator such as a user or a service person of information regarding the life of the intermediate transfer belt 8 is executed.

Hereinafter, the method of detecting the life of the intermediate transfer belt 8 in this embodiment will be described in more detail. 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 light with a predetermined irradiation light amount is based on the rate of change from the initial use of the intermediate transfer belt 8. , The life of the intermediate transfer belt 8 is determined. FIG. 9 is a flowchart showing an outline of the procedure for detecting the life of the intermediate transfer belt 8 in this embodiment.

・ Step1
The engine control unit 302 detects when the image forming apparatus 100 is started for the first time, or when the replacement detection unit 306 detects that the belt unit 12 has been replaced and a new belt unit 12 has been attached, the intermediate transfer belt 8 Start the procedure for life detection.

・ Step2
The engine control unit 302 starts the operation of the density correction control and the color shift correction control, and determines the irradiation light amount (first irradiation light amount) L1 of the optical sensor 7 for the density correction control and the color shift correction control. In this embodiment, the irradiation light amount L1 for density correction control and color shift correction control has the largest 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. Select to. That is, in this embodiment, the irradiation light amount L1 for the density correction control and the color shift correction control is the dynamic range of the optical sensor 7 within a range in which the output of the optical sensor 7 is not saturated with the toner loading amount of the test toner image T. Select to be the widest.

・ Step3
The engine control unit 302 determines the irradiation light amount (second irradiation light amount) L2 of the optical sensor 7 for detecting the life of the intermediate transfer belt 8. That is, the optimum density correction control and the above-mentioned optimum density correction control and corresponding to the amount of change in the groove depth D due to wear of the surface layer 82 of the intermediate transfer belt 8 and the increase in the amount of specular reflection light due to the use of the intermediate transfer belt 8. The irradiation light amount L1 for color shift correction control changes. Therefore, in this embodiment, the irradiation light amount L1 for the density correction control and the color shift correction control is changed as the amount of the intermediate transfer belt 8 used increases. 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 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 of the irradiation light amount L1 for density correction control and color shift correction control determined for the new intermediate transfer belt 8 in Step 2 is used for detecting the life of the intermediate transfer belt 8. The amount of irradiation light is L2. The amount of irradiation light of the optical sensor 7 is the amount of light (radiant energy) irradiated within a fixed time per unit area of the surface of the intermediate transfer belt 8, and can be measured by a known light amount measuring device. However, the amount of irradiation light of the optical sensor 7 can be represented by the magnitude of the drive current (mA) of the light emitting element 71. For example, when the drive current and the irradiation light amount are in a substantially proportional relationship, the second irradiation light amount L2, which is half of the first irradiation light amount L1, is half the drive current for obtaining the first irradiation light amount L1. It is the amount of irradiation light obtained in.

・ Step4
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 with respect to the new intermediate transfer belt 8, and obtains the non-volatile memory 303. To memorize. In this embodiment, the length of the intermediate transfer belt 8 in the belt transport direction is 720 mm. Further, acquiring the average value of the outputs of the specular reflection light receiving element 72 of the optical sensor 7 for one round of the intermediate transfer belt 8 is hereinafter simply referred to as “measurement of the surface state”.

・ Step5
The engine control unit 302 proceeds to Step 6 at a predetermined timing when the number of prints from the previous measurement of the surface state reaches a predetermined threshold value of N. That is, in this embodiment, the engine control unit 302 has a function as a counting means that sequentially integrates and stores the number of prints each time an image is formed on one recording material P and output. Then, each time the engine control unit 302 forms an image on one recording material P and outputs the image, the cumulative number of prints from the previous measurement of the surface state and the preset ROM in the engine control unit 302 are set. Compare with the threshold N sheets stored in. In this example, the threshold value N = 5000 sheets. The number of prints may be set to a predetermined size (for example, A4 size). Further, the timing of measuring the surface state is not limited to the setting of the number of printed sheets. The timing for measuring the surface condition is set using an arbitrary index value that correlates with the amount of the intermediate transfer belt 8 used, such as the rotation time and the number of rotations of the intermediate transfer belt 8 and the rotation time and the number of rotations of other rotating members. can do.

・ Step6
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 non-volatile memory 303. As described above, in this embodiment, the surface state of the intermediate transfer belt 8 is measured with the same irradiation light amount L2 for each N printed sheets, and the measurement result is stored in the non-volatile memory 303. In this embodiment, the next surface condition is not measured immediately after the number of prints from the previous surface condition measurement has passed N, but the output of all the images of the job straddling N is completed. The next surface condition was measured during the printing end processing after the printing. Here, the job refers to a series of operations in which an image is formed and output on a single or a plurality of recording materials P, which is started by one start instruction. The print end process (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 the final image of the job is output. It means that. The surface state of the intermediate transfer belt 8 can be measured at any timing during non-image formation, which is a period other than image formation in which an image transferred to the recording material P and output is formed. .. The non-image formation includes the above-mentioned post-rotation operation (print end processing), the pre-multi-rotation operation, which is the period of the preparatory operation before image formation, the pre-rotation operation, and the recording material P during continuous image formation. For example, during paper-to-paper operation, which is a period corresponding to the recording material P.

・ Step7
The engine control unit 302 calculates the rate of change of the current measurement result V2_N of the intermediate transfer belt 8 with respect to the measurement result V2_ini of the surface state of the new intermediate transfer belt 8, that is, V2_N / V2_ini. Then, the engine control unit 302 compares the rate of change with the predetermined threshold value R, and determines whether or not the rate of change is greater than the threshold value R. The threshold value R is preset and stored in the ROM in 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 = 1.625 times is set based on the experimental result shown in FIG. That is, this threshold value R is the output of the optical sensor 7 when the groove depth D is less than 0.2 μm and cleaning failure may occur, and the groove depth D is 0.45 μm (new intermediate transfer belt 8). ) Corresponds to the ratio 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 or the like that can satisfy the cleaning performance.

・ Step8
When the engine control unit 302 determines in Step 7 that the predetermined threshold value R is exceeded, it determines that the intermediate transfer belt 8 has reached the end of its life, and performs a process for notifying information on the life of the intermediate transfer belt 8. Execute. In this embodiment, as the process, the display means of the operation unit 308 or the host computer 200 displays information indicating that the intermediate transfer belt 8 has reached the end of its life, or information prompting the replacement of the intermediate transfer belt 8. To execute.

10. Effect As described above, the image forming apparatus 100 of this embodiment has a control means (engine control unit) 302 capable of executing a process for notifying information regarding the life of the intermediate transfer belt 8. Further, in the image forming apparatus 100 of this embodiment, diffraction occurs on the surface of the intermediate transfer belt 8 due to the irradiation light from the optical sensor 7 during at least a part of the life period of the intermediate transfer belt 8, and a part of the diffracted light is generated. Is configured to be out of the light receiving range of the optical sensor 7 or within the light receiving range of the optical sensor 7. Then, in this embodiment, the control means 302 executes the above process based on the detection result of the optical sensor 7 acquired by irradiating the surface of the intermediate transfer belt 8 with light by the optical sensor 7. In particular, in this embodiment, the control means 302 is the first detection result of the optical sensor 7 obtained by irradiating the surface of the intermediate transfer belt 8 with light from the optical sensor 7 at a predetermined irradiation light amount at the first timing. , Change between the second detection result of the optical sensor 7 obtained by irradiating the intermediate transfer belt 8 with light from the optical sensor 7 at the second timing after the first timing with the predetermined irradiation light amount. The above process is executed based on the index related to. In this embodiment, the optical sensor 7 can receive the specularly reflected light from the surface of the intermediate transfer belt 8, and the control means 302 is based on the above index indicating the amount of increase in the specularly reflected light received by the optical sensor 7. And execute the above process. Further, in this embodiment, the control means 302 executes the above process when the index exceeds a predetermined threshold value. Further, in this embodiment, the index is the rate of change between the first detection result and the second detection result. Further, in this embodiment, the optical sensor 7 also serves as a means for detecting a test toner image formed on the image carrier. Then, in this embodiment, the predetermined irradiation light amount is different from the irradiation light amount 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 shift correction control. Further, in this embodiment, a plurality of grooves along the belt transport direction are formed on the surface of the intermediate transfer belt 8 side by side in the belt width direction. In this embodiment, the average value of the intervals between the adjacent grooves is 2 μm or more and 10 μm or less. Further, in the present embodiment, the distance between the adjacent grooves is substantially the same over substantially the entire area in the belt width direction.

As described above, in the present embodiment, 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 groove depth D accompanying the use of the intermediate transfer belt 8. As a result, according to the present embodiment, it is possible to accurately notify the information regarding the life of the intermediate transfer belt 8 having the uneven shape formed on the surface.

Here, for example, in the conventional life detection method as described in Patent Document 2, which is known as a conventional technique, it is premised that there is no diffused reflection component from the intermediate transfer belt at the initial stage of use of the intermediate transfer belt. .. Then, when the diffused reflection component increases more than the set value experimentally obtained in advance, it is determined that the intermediate transfer belt has reached the end of its life. Therefore, in such a conventional life detection method, it may not be possible to correctly determine the life of the intermediate transfer belt 8 with respect to the intermediate transfer belt 8 in which diffraction is generated by the irradiation light from the optical sensor as in the present embodiment. is there. On the other hand, according to this embodiment, it is possible to accurately determine or notify information on the life of the intermediate transfer belt 8 having the uneven shape formed on the surface.

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

The image forming apparatus 100 may have a cleaning mechanism as a cleaning means for the optical sensor 7. FIG. 10A is a schematic view showing an example of the cleaning mechanism 30 of the optical sensor 7. In the illustrated example, the cleaning mechanism 30 has a cleaning member 31 for cleaning the protective cover (or mold lens portion) 75, which is a light receiving portion (light receiving surface) of the optical sensor 7, and a cleaning portion 31 relative to the optical sensor 7. It has a moving member 32 to be moved. As the cleaning member 31, for example, a non-woven fabric, felt, sponge or the like can be used. Further, as the moving member 32, for example, a member that reciprocates in the belt width direction in conjunction with opening and closing of a door (not shown) of the device main body 110 for replacing the process cartridge P and the belt unit 12 is used. be able to. The moving member 32 may be driven at a predetermined timing by a driving force transmitted from a driving motor or the like as a 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, 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 may decrease. There is. Therefore, the detection result of the optical sensor 7 within a predetermined period after being cleaned 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 an experiment 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 a cleaning mechanism 30 for cleaning the optical sensor 7. In this case, the control means 302 can execute the above process based on the detection result of the optical sensor 7 within a predetermined period after the cleaning mechanism 30 has cleaned the optical sensor 7.

FIG. 10B is a flowchart showing an outline of the procedure for detecting the life of the intermediate transfer belt 8 in this case. The engine control unit 302 acquires the time when the cleaning mechanism 30 is operated and stores it in the non-volatile memory 303 (Step 11). The engine control unit 302 operates the cleaning mechanism 30 based on a detection signal from a door sensor (not shown) that detects that the door is closed (or opened), for example. Information about (date and time, time, etc.) can be obtained. When the engine control unit 302 determines that the rate of change of the detection result of the optical sensor 7 exceeds the threshold value as described with reference to FIG. 9 (Step 12), it is within a predetermined period from the previous operation of the cleaning mechanism 30. It is determined whether or not it is (Step 13). In the case of this example, the door is opened and closed to perform the cleaning operation of the cleaning mechanism 30 before the detection result of the optical sensor 7 regarding the new intermediate transfer belt 8 is acquired. Further, the above-mentioned predetermined period is an integrated value of index values that correlate with the elapsed time from the time when the previous cleaning mechanism 30 was operated, or the amount of the intermediate transfer belt 8 used such as the number of prints after the time. It can be set with. In this case, the engine control unit 302 has a function as a counting means for counting the elapsed time and the integrated value of the index value. Then, when the engine control unit 302 determines in Step 13 that the period is within the predetermined period, the engine control unit 302 proceeds to Step 8 in FIG. 9 and executes a process for notifying information on the life of the intermediate transfer belt 8. On the other hand, when the engine control unit 302 determines in Step 13 that the period is not within the predetermined period (that is, the predetermined period has passed), the engine control unit 302 proceeds to Step 5 in FIG. 9 and measures the surface state of the intermediate transfer belt 8 next time. Wait for. In this way, when the rate of change of the detection result of the optical sensor 7 exceeds the threshold value, the life is not immediately notified, but the rate of change 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 the present embodiment, the life of the intermediate transfer belt 8 is determined based on the detection result of the 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 with the use of the intermediate transfer belt 8 (typically, the amount of diffusely reflected light decreases). Therefore, the life of the intermediate transfer belt 8 may be determined by using only the detection result of the diffusely reflected light by the optical sensor 7 or 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 rate of change of the detection result of the diffusely reflected light becomes larger than a predetermined threshold value, a process for notifying information on the life of the intermediate transfer belt 8 can be executed. .. Further, when both the detection result of the specularly reflected light and the detection result of the diffusely reflected light are used, the life of the intermediate transfer belt 8 is reached when the rate of change of the detection result of either one or both becomes larger than a predetermined threshold value. It is possible to execute a process for notifying information about. In this case, the threshold value may be the same or different for the detection result of the specularly reflected light and the detection result of the diffusely reflected 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 above index indicating the amount of decrease in the diffusely reflected light received by the optical sensor 7. May be executed.

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

Further, in this embodiment, when the index of change in the detection result of the optical sensor 7 (rate of change in this embodiment) exceeds a predetermined threshold value, information is notified that the intermediate transfer belt 8 has reached the end of its life. However, the present invention is not limited to this. For example, the index of change (rate of change, amount of change) of the detection result of the optical sensor 7 can be stored in the non-volatile memory 303 at predetermined timings such as every N number of printed sheets. Then, the transition of the index of the change of the detection result of the optical sensor 7 is monitored, the remaining life of the intermediate transfer belt 8 is determined, and the remaining life of the intermediate transfer belt 8 is sequentially or by the operator. It may be notified according to the instruction. In this case, for example, the detection result of the optical sensor 7 regarding the new intermediate transfer belt 8 corresponds to the remaining life remaining 100%, and the detection result of the optical sensor 7 corresponding to the above threshold value corresponds to the remaining life remaining 0%. Can be. Further, for example, information for setting a plurality of threshold values for a change in the detection result of the optical sensor 7 to notify that the life of the intermediate transfer belt 8 is approaching, and information for notifying that the intermediate transfer belt 8 has reached the end of its life. , Etc. may be notified in sequence.

Further, in the present embodiment, the information regarding the life of the intermediate transfer belt 8 is notified by the display in the display means (display of a message notifying that the life has been reached, a message prompting replacement, etc.). The invention is not limited to this. For example, any method capable of notifying information on the life of the intermediate transfer belt 8, such as turning on or blinking a warning light or pronouncing a message by voice, can be used.

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

[Example 2]
Next, other examples of the present invention will 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 Example 1. Therefore, 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 designated 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 fine unevenness processing on the surface is overlapped in a part in the circumferential direction. Then, in this embodiment, the detection result of the optical sensor 7 relating to 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 more accurately.

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 shape formed on its surface by imprinting. In the imprinting process, the pressing force may be changed stepwise at the stage where the mold is started to be pressed against the surface of the intermediate transfer belt 8 and the stage where the mold is started to be separated from the surface of the intermediate transfer belt 8. This is to prevent the intermediate transfer belt 8 having a hardened surface from being broken by applying an extra load in the direction. Further, it is difficult to completely match the start point and the end point of the groove 83 in μm units in the belt width direction, and a part of the circumferential direction of the intermediate transfer belt 8 is a part of the start point side and a part of the end point side of the groove 83. There may be a part that overlaps with. Therefore, in the circumferential direction of the intermediate transfer belt 8, the non-overlapping region (non-overlapping portion) X in which the fine concavo-convex processing is not duplicated and the overlapping region (overlapping portion) Y in which the fine concavo-convex processing is overlapped. The average groove spacing I and groove depth D may differ from each other. In the overlapping region Y, only one of the average groove spacing I and the groove depth D may be different.

FIG. 12 is a schematic view of the vicinity of the surface layer of the intermediate transfer belt 8 when cut in a direction substantially orthogonal to the belt transport direction (viewed along the belt transport direction) in each of the non-overlapping region X and the overlapping region Y. It is an enlarged partial sectional view. A groove (groove shape, groove portion) 83 along the belt transport direction is formed in the non-overlapping region X and the overlapping region Y as in the first embodiment. In this example, the average groove spacing I is 3.5 μm in the non-region X and 1.8 μm in the overlapping region Y. The groove depth D (mean value) is 0.45 μm in the non-overlapping region X and 0.25 μm in the overlapping region Y at the initial stage 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 is almost the same between the non-overlapping region X and the overlapping region Y. Since the average groove spacing I and the groove depth D of the overlapping region Y are different from those of the non-overlapping region X, the diffraction angle and the intensity of the diffracted light due to the irradiation light from the optical sensor 7 are different from the non-overlapping region X. ..

FIG. 13 is a graph showing the output waveform of the optical sensor 7 when about one round of the intermediate transfer belt 8 of the present embodiment having the non-overlapping region X and the overlapping region Y is detected in the belt transport direction. In FIG. 13, the horizontal axis represents time, and the vertical axis represents the output of the specular reflection light receiving element 72 (specular reflection light amount) and the output of the diffuse reflection light receiving element 73 (diffuse reflection light amount) of the optical sensor 7. As can be seen from FIG. 13, in the overlapping region Y, the amount of specularly reflected light drops sharply, and the amount of diffusely reflected light rises sharply. That is, if the detection result relating to the overlapping region Y is included 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, it causes an error. On the other hand, since the detection results of the specular reflected light amount and the diffusely reflected light amount in the non-overlapping region X and the overlapping region Y are clearly different, it is easy to specify the detection results for each region 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 same position in the non-overlapping region X starting from the boundary from the overlapping region Y to the non-overlapping region X (in this embodiment, the non-overlapping region X). The detection result of the optical sensor 7 regarding (substantially the entire area) is acquired. Then, based on the detection result of the optical sensor 7 regarding the non-overlapping region X, the life of the intermediate transfer belt 8 is determined in the same manner as in the first embodiment. Specifically, in the present embodiment, the engine control unit 302 acquires the detection result of the optical sensor 7 for one round of the intermediate transfer belt 8 as shown in FIG. 13, and determines a predetermined region starting from the boundary. Only the detection result of is used for detecting the life of the intermediate transfer belt 8. Alternatively, only the detection result of the optical sensor 7 for a predetermined period excluding the period in which the overlapping region Y passes through the detection region of the optical sensor 7 may be acquired for the life detection of the intermediate transfer belt 8.

As described above, in the present embodiment, the intermediate transfer belt 8 has a first region X and a second region Y shorter than the first region X in the belt moving direction, and the first region X and the first region X. At least one of the average value of the groove spacing and the average value of the groove depth is different from the second region Y. In this case, the control means 302 can execute a process for notifying information on the life based on the detection result of the optical sensor 7 regarding the first region X. Typically, the average value of the groove spacing in the first region X is 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 area in the belt width direction.

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

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

In the above-described embodiment, 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 that of the above-described example can be obtained by forming a groove on the surface. Can be done. That is, the intermediate transfer material is not limited to the configuration consisting of a plurality of layers, and may be composed 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 embodiment. It suffices to have the shape of. Further, even in the configuration in which the intermediate transfer material is composed of a plurality of layers, the layer is not limited to two layers, and the layer corresponding to the base layer of the above-described embodiment is composed of a plurality of layers or corresponds to the base layer of the above-mentioned example. A single layer or a plurality of layers may be provided below the layer to be used.

Further, the intermediate transfer body is not limited to the belt-shaped one, and even if it is a drum-shaped one (intermediate transfer drum) formed by, for example, stretching a sheet on a frame body, the present invention can be used. It can be applied in the same way to obtain the same effect. Further, the image forming apparatus is not limited to the in-line type. For example, a plurality of developing devices are provided for one photoconductor, and the toner images sequentially formed on the photoconductor are sequentially primary-transferred to the intermediate transfer body and then superposed on the intermediate transfer body. An image forming apparatus of a type in which the combined toner image is secondarily transferred to a transfer material may be used. That is, the intermediate transfer body as the image carrier may be any one that transports the toner image primaryly transferred from another image carrier that supports the toner image for secondary transfer to the recording material.

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

1 Photosensitive drum 7 Optical sensor 8 Intermediate transfer belt 12 Belt unit 20 Belt cleaning device 21 Cleaning blade

Claims (17)

An image carrier that supports a toner image and
An optical sensor that irradiates the surface of the image carrier with light to detect reflected light,
A control means capable of executing a process for notifying information on the life of the image carrier, and
In the image forming apparatus having
During at least a part of the life period of the image carrier, the irradiation light from the optical sensor causes diffraction on the surface of the image carrier, and a part of the diffracted light is out of the light receiving range of the optical sensor or said. It is configured to be within the light receiving range of the optical sensor.
The control means is an image forming apparatus characterized in that the processing is executed based on the detection result of the optical sensor obtained by irradiating the surface of the image carrier with light by the optical sensor. The control means is based on the first detection result of the optical sensor obtained by irradiating the surface of the image carrier with light at a predetermined irradiation light amount from the optical sensor at the first timing, and the first timing. Based on the index regarding the change between the second detection result of the optical sensor obtained by irradiating the image carrier with light at the predetermined irradiation light amount from the optical sensor at the second timing later. The image forming apparatus according to claim 1, wherein the process is executed. The optical sensor can receive specularly reflected light from the surface of the image carrier, and the control means executes the process based on the index indicating an increase amount of specularly reflected light received by the optical sensor. The image forming apparatus according to claim 2, wherein the image forming apparatus is used. The optical sensor can receive diffusely reflected light from the surface of the image carrier, and the control means executes the process based on the index indicating the amount of decrease in diffusely reflected light received by the optical sensor. 2. The image forming apparatus according to claim 2. The image forming apparatus according to any one of claims 2 to 4, wherein the control means executes the process when the index exceeds a predetermined threshold value. The image forming apparatus according to any one of claims 2 to 5, wherein the index is a rate of change between the first detection result and the second detection result. The image forming apparatus according to any one of claims 1 to 6, wherein the optical sensor also serves as a means for detecting a test toner image formed on the image carrier. The optical sensor also serves as a 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 2 to 6, wherein the image forming apparatus is characterized. The image forming apparatus according to claim 7 or 8, wherein the test toner image is a test toner image for image density control or color shift correction control. It has a cleaning means for cleaning the optical sensor.
Claims 1 to 9 are characterized in that the control means executes the process based on the detection result of the optical sensor within a predetermined period after the cleaning means has cleaned the optical sensor. The image forming apparatus according to any one of the above. Claims 1 to 10 are characterized in that the image carrier is an intermediate transfer body that transports a toner image primaryly transferred from another image carrier that supports a toner image for secondary transfer to a recording material. The image forming apparatus according to any one of the above. The surface of the image carrier is characterized in that a plurality of grooves along the moving direction of the surface of the image carrier are formed side by side in the width direction of the image carrier intersecting the moving direction. The image forming apparatus according to any one of claims 1 to 11. The image forming apparatus according to claim 12, wherein the average value of the intervals between the adjacent grooves is 2 μm or more and 10 μm or less. The image forming apparatus according to claim 12, wherein the intervals between adjacent grooves are substantially the same. The image carrier has a first region and a second region shorter than the first region in the moving direction, and the groove adjacent to the first region and the second region. At least one of the average value of the intervals between the intervals and the average value of the depths of the grooves is different, and the control means executes the process based on the detection result of the optical sensor with respect to the first region. The image forming apparatus according to claim 12. The image forming apparatus according to claim 15, wherein the average value of the intervals between the adjacent grooves in the first region is 2 μm or more and 10 μm or less. The image forming apparatus according to claim 15 or 16, wherein the intervals between adjacent grooves in the first region are substantially the same.

Images