JP7540216B2 - Lubricant application device, image forming apparatus and control method - Google Patents

Description

The present invention relates to a lubricant application device, an image forming device, and a control method.

In general, in image forming devices (printers, copiers, facsimiles, etc.) that use electrophotographic process technology, a laser beam based on image data is irradiated (exposed) onto a uniformly charged photoconductor (image carrier), forming an electrostatic latent image on the surface of the photoconductor. Toner is then supplied to the paper on which the electrostatic latent image has been formed, making the electrostatic latent image visible and forming a toner image. This toner image is then transferred to the paper directly or indirectly via an intermediate transfer body, and then heated and pressed by a fixing device to form an image on the paper.

In addition, the toner remaining on the surface of the photoreceptor after transfer (residual toner) is collected by a cleaning device. The cleaning device has a cleaning blade made of an elastic material that is placed in rubbing contact with the surface of the photoreceptor. The surface of the photoreceptor is cleaned by scraping off the residual toner with the cleaning blade.

At this time, because the photoconductor is rotated with the cleaning blade in contact with it, frictional forces are generated at the contact points between the photoconductor and the cleaning blade, causing the photoconductor and the cleaning blade to wear down and deteriorate. If the efficiency of removing the residual toner decreases, there is a risk of image quality deteriorating, such as the occurrence of image unevenness. Therefore, conventional image forming devices are equipped with a lubricant applicator that applies a lubricant to the surface of the photoconductor in order to reduce the frictional forces at the contact points.

When applying a lubricant to a photoreceptor, a lubricant application brush is generally fixed in sliding contact with the photoreceptor, and a solid lubricant (lubricant rod) is placed in a state where it is pressed against this lubricant application brush. The lubricant application brush then rotates to scrape off the solid lubricant, and the scraped off lubricant is applied to the photoreceptor. The applied lubricant is spread over the photoreceptor and formed into a film by a leveling member (e.g. a leveling blade) that is positioned downstream of the lubricant application brush in the direction of rotation of the photoreceptor, and is then applied to the photoreceptor.

Prior art documents related to lubricant application devices include, for example, Patent Documents 1 to 3. Patent Document 1 discloses controlling the temperature of solid lubricant. Patent Document 2 discloses changing the temperature of a lubricant application brush to control the amount of lubricant scraped off. These technologies make it possible to stably supply lubricant to the photoconductor.

Patent Document 3 also discloses controlling the temperature of a leveling member made of a rotating roller. This technology allows the lubricant supplied to the photoconductor to be applied evenly.

Japanese Unexamined Patent Publication No. 7-334055 JP 2010-230903 A JP 2012-234004 A

In order to extend the life of image forming devices (specifically, image forming units), it is necessary to improve the efficiency of lubricant application to the photoconductor (≒amount of lubricant applied/amount of lubricant supplied) and reduce the consumption of lubricant rods. Here, there are two factors that can reduce the efficiency of lubricant application: poor passage of the lubricant through the leveling blade, and poor coating of the lubricant by the leveling blade.

First, we will explain the failure of the lubricant to pass through the leveling blade. In other words, not all of the lubricant (powder) that is applied by the lubricant application brush and supplied to the leveling blade is ultimately applied to the photoreceptor; approximately half of the lubricant supplied is blocked by the leveling blade and falls into the unit (lubricant application device) and remains unused. One of the reasons that the lubricant is blocked by the leveling blade is that the contact force of the leveling blade against the photoreceptor is high, which creates a large blocking force against the lubricant.

Next, we will explain the failure of the smoothing blade to form a film on the lubricant. In other words, the lubricant (powder) that passes through the smoothing blade may pass through in powder form without being formed into a film. The lubricant that passes through in powder form is collected in the subsequent developing device or transferred to the intermediate transfer body, and remains unused.

The efficiency of lubricant application varies depending on the image formation conditions, particularly the ambient temperature during image formation. For example, in a low-temperature environment, the hardness of the smoothing blade increases, the contact nip width between the photoconductor and the smoothing blade decreases, and the surface pressure of the smoothing blade against the photoconductor increases. This causes the lubricant to pass through the smoothing blade poorly. Furthermore, in a low-temperature environment, the viscosity of the lubricant powder decreases, and the extensibility of the smoothing blade when it is pressed and spread over the photoconductor decreases. This causes the smoothing blade to poorly coat the lubricant. In a high-temperature environment, the opposite situation occurs to the low-temperature environment, so the efficiency of lubricant application decreases in a low-temperature environment and increases in a high-temperature environment.

When the efficiency of lubricant application decreases, the thickness of the lubricant film formed on the photoreceptor deviates from the desired value and becomes smaller, which makes it more likely that problems (poor transfer, poor cleaning) will occur. Therefore, in order to maintain the lubricant film thickness at the desired value, the number of rotations of the lubricant application brush is increased to increase the amount of lubricant applied (consumption) to the photoreceptor, thereby increasing the amount of lubricant supplied to the leveling blade. However, even if the amount of lubricant supplied to the leveling blade increases and the amount of lubricant passing through increases, the amount of lubricant that fails to pass through also increases, which is detrimental to the long life of the image forming device.

In addition, when the thickness of the lubricant film deviates from the desired value in a high-temperature environment, the cleaning performance improves, but the amount of external additives passing through the cleaning blade decreases, and the ability to polish foreign matter attached to the photoreceptor decreases. As a result, the amount of lubricant coated on the photoreceptor that can be removed by the external additive decreases, and an old lubricant layer accumulates on the photoreceptor. The old lubricant layer changes into a deteriorated lubricant layer due to exposure to ozone and nitrogen oxides generated by the charging device. The deteriorated lubricant layer is easily ionized by reacting with moisture in the air, which causes image defects such as image flow. Therefore, in order to suppress the increase in the thickness of the lubricant film in a high-temperature environment, the rotation speed of the lubricant application brush is reduced to reduce the amount of lubricant applied (consumption) to the photoreceptor. However, since the lubricant application brush also has the function of removing the deteriorated lubricant layer, it is disadvantageous in suppressing image flow.

The present invention aims to provide a lubricant application device, an image forming device, and a control method that can suppress fluctuations in the thickness of the lubricant film formed on the image carrier.

The lubricant application device according to the present invention comprises:
a coating member that comes into contact with the image carrier having a toner image density to be formed on the image carrier and coats the lubricant applied to the image carrier;
a displacement unit that displaces the coating member in an axial direction of the image carrier in response to an image forming condition;
Equipped with.

The image forming apparatus according to the present invention is equipped with the above-mentioned lubricant application device.

The control method according to the present invention comprises the steps of:
1. A control method for a lubricant application device having a coating member that contacts an image carrier and coats a lubricant applied to the image carrier, comprising:
acquiring image forming conditions including a density of a toner image formed on the image carrier ;
The coating member is displaced in the axial direction of the image carrier in accordance with the acquired image forming conditions.

According to the present invention, it is possible to suppress fluctuations in the thickness of the lubricant film formed on the image carrier.

1 is a diagram illustrating an overall configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a diagram showing a main part of a control system of the image forming apparatus according to the present embodiment. FIG. 2 is a diagram showing the peripheral configuration of a drum cleaning device according to the present embodiment. 11A and 11B are diagrams illustrating a configuration for swinging a leveling blade in the present embodiment. 5 is a flowchart showing an example of a control operation of the image forming apparatus according to the present embodiment.

The following describes in detail the embodiments of the present invention with reference to the drawings.

Figure 1 is a diagram showing the overall configuration of an image forming apparatus 1 according to this embodiment. Figure 2 is a diagram showing the main parts of the control system of the image forming apparatus 1 according to this embodiment.

As shown in Figures 1 and 2, image forming apparatus 1 is a color image forming apparatus of the intermediate transfer type that utilizes electrophotographic process technology. That is, image forming apparatus 1 forms an image by primarily transferring the toner images of each color, C (cyan), M (magenta), Y (yellow) and K (black), formed on a photoconductor to an intermediate transfer body, superimposing the four color toner images on the intermediate transfer body, and then secondary transferring the images to paper.

The image forming device 1 also uses a tandem system in which photoconductors corresponding to the four colors CMYK are arranged in series in the running direction of the intermediate transfer body, and each color toner image is transferred sequentially to the intermediate transfer body in a single step.

As shown in Figures 1 and 2, the image forming device 1 includes an image reading unit 10, an operation display unit 20, an image processing unit 30, an image forming unit 40, a paper conveying unit 50, a fixing unit 60, and a control unit 100.

The control unit 100 includes a CPU (Central Processing Unit) 101, a ROM (Read Only Memory) 102, and a RAM (Random Access Memory) 103. The CPU 101 reads a program corresponding to the processing contents from the ROM 102, loads it into the RAM 103 (volatile memory), and centrally controls the operation of each block of the image forming device 1 in cooperation with the loaded program. At this time, various data such as a LUT (Look Up Table) stored in the memory unit 72 is referenced.

The control unit 100 functions as part of the "displacement unit" of the present invention.

The control unit 100 transmits and receives various data to and from an external device (e.g., a personal computer) connected to a communication network such as a LAN (Local Area Network) or a WAN (Wide Area Network) via the communication unit 71. The control unit 100 receives, for example, image data transmitted from an external device, and forms an image on paper based on this image data (input image data). The communication unit 71 is composed of, for example, a communication control card such as a LAN card.

The image reading unit 10 is configured with an automatic document feeder 11, also known as an ADF (Auto Document Feeder), and a document image scanning device (scanner) 12, etc.

The automatic document feeder 11 transports the document D placed on the document tray using a transport mechanism and sends it to the document image scanning device 12. The automatic document feeder 11 can continuously read the images (including both sides) of multiple documents D placed on the document tray all at once.

The original image scanning device 12 optically scans the original D transported from the automatic document feeder 11 onto the contact glass or the original D placed on the contact glass, and forms an image of the reflected light from the original D on the light receiving surface of a CCD (Charge Coupled Device) sensor 12a to read the original image. The image reading unit 10 generates input image data based on the results of the reading by the original image scanning device 12. This input image data is subjected to a predetermined image processing in the image processing unit 30.

The operation display unit 20 is composed of, for example, a liquid crystal display (LCD) with a touch panel, and functions as a display unit 21 and an operation unit 22. The display unit 21 displays various operation screens and the operating status of each function according to a display control signal input from the control unit 100. The operation unit 22 has various operation keys such as a numeric keypad and a start key, accepts various input operations by the user, and outputs operation signals to the control unit 100.

The image processing unit 30 is equipped with circuits and the like that perform digital image processing on the input image data according to initial settings or user settings. For example, under the control of the control unit 100, the image processing unit 30 performs gradation correction based on gradation correction data (gradation correction table). In addition to gradation correction, the image processing unit 30 also performs various correction processes such as color correction and shading correction, as well as compression processing, on the input image data. The image forming unit 40 is controlled based on the image data that has been subjected to these processes.

The image forming section 40 includes image forming units 41Y, 41M, 41C, and 41K, and an intermediate transfer unit 42 for forming images using color toners of the Y, M, C, and K components based on input image data.

Image forming units 41Y, 41M, 41C, and 41K for the Y, M, C, and K components have the same configuration. For ease of illustration and explanation, common components are indicated with the same reference numerals, and when distinguishing between them, the reference numerals are followed by Y, M, C, or K. In FIG. 1, reference numerals are only assigned to the components of image forming unit 41Y for the Y component, and reference numerals are omitted for the components of the other image forming units 41M, 41C, and 41K.

The image forming unit 41 includes an exposure device 411, a developing device 412, a photosensitive drum 413 (corresponding to the "image carrier" of the present invention), a charging device 414, and a drum cleaning device 415.

The photoconductor drum 413 is a photoconductor having photoconductivity, which is constructed by sequentially laminating an undercoat layer (UCL), a charge generation layer (CGL), and a charge transport layer (CTL) on the peripheral surface of a conductive aluminum cylinder (aluminum tube). The photoconductor drum 413 is, for example, a negatively charged organic photoconductor (OPC).

The charging device 414 uniformly charges the surface of the photoconductive photoconductor drum 413 to a negative polarity. The charging device 414 is a strobocollector charger.

The exposure device 411 is composed of, for example, a semiconductor laser, and irradiates the photoconductor drum 413 with laser light corresponding to an image of each color component. Irradiation with the laser light generates positive charges in the charge generation layer of the photoconductor drum 413, and when the charges are transported to the surface of the charge transport layer, the surface charge (negative charge) of the photoconductor drum 413 is neutralized. As a result, an electrostatic latent image of each color component is formed on the surface of the photoconductor drum 413 due to the potential difference with the surroundings.

The developing device 412 contains a developer for each color component (for example, a two-component developer consisting of a small particle size toner and a carrier (magnetic material)) and visualizes the electrostatic latent image to form a toner image by adhering the toner for each color component to the surface of the photoconductor drum 413. The developing roller in the developing device 412 consists of a cylindrical developing sleeve 412A that is driven to rotate, and a cylindrical magnet roller that is inserted into the developing sleeve 412A and fixed to the housing of the developing device 412 so as not to rotate.

The magnet roller is made up of multiple magnets arranged along its circumference, and the carrier is carried and transported on the outer peripheral surface of the developing sleeve 412A by the magnetic force thereof, and stands up at a position (developing position) opposite the photosensitive drum 413 to form a magnetic brush. The toner electrostatically attracted to the carrier and transported moves to the photosensitive drum 413 side at the developing position due to the potential difference between the developing sleeve 412A and the photosensitive drum 413, and the electrostatic latent image formed on the peripheral surface is developed.

The drum cleaning device 415 has a drum cleaning blade that slides against the surface of the photosensitive drum 413. The specific configuration of the drum cleaning device 415 will be described later.

The intermediate transfer unit 42 includes an intermediate transfer belt 421, a primary transfer roller 422, a number of support rollers 423, a secondary transfer roller 424, and a belt cleaning device 426.

The intermediate transfer belt 421 is an endless belt that is stretched around a number of support rollers 423 in a loop shape. At least one of the support rollers 423 is a drive roller, and the others are driven rollers. For example, it is preferable that roller 423A, which is arranged downstream in the belt running direction from primary transfer roller 422 for K component, is the drive roller. This makes it easier to maintain a constant running speed of the belt in the primary transfer section. As drive roller 423A rotates, intermediate transfer belt 421 runs at a constant speed in the direction of arrow A.

The intermediate transfer belt 421 is a conductive and elastic belt having a high resistance layer on its surface. The intermediate transfer belt 421 is driven to rotate by a control signal from the control unit 100.

The primary transfer roller 422 is disposed on the inner peripheral side of the intermediate transfer belt 421, facing the photoconductor drum 413 of each color component. The primary transfer roller 422 is pressed against the photoconductor drum 413 with the intermediate transfer belt 421 sandwiched therebetween, forming a primary transfer nip for transferring the toner image from the photoconductor drum 413 to the intermediate transfer belt 421.

The secondary transfer roller 424 is disposed on the outer circumferential surface side of the intermediate transfer belt 421, facing the backup roller 423B, which is disposed downstream of the drive roller 423A in the belt running direction. The secondary transfer roller 424 is pressed against the backup roller 423B with the intermediate transfer belt 421 sandwiched therebetween, thereby forming a secondary transfer nip for transferring a toner image from the intermediate transfer belt 421 to the paper S.

When the intermediate transfer belt 421 passes through the primary transfer nip, the toner image on the photoconductor drum 413 is sequentially superimposed and primarily transferred onto the intermediate transfer belt 421. Specifically, a primary transfer bias is applied to the primary transfer roller 422, and a charge of the opposite polarity to the toner is applied to the back side of the intermediate transfer belt 421, i.e., the side that contacts the primary transfer roller 422, so that the toner image is electrostatically transferred to the intermediate transfer belt 421.

Then, when the paper S passes through the secondary transfer nip, the toner image on the intermediate transfer belt 421 is secondarily transferred to the paper S. Specifically, a secondary transfer bias is applied to the secondary transfer roller 424, and a charge of the opposite polarity to the toner is applied to the back side of the paper S, that is, the side that contacts the secondary transfer roller 424, so that the toner image is electrostatically transferred to the paper S. The paper S with the transferred toner image is transported toward the fixing unit 60.

The belt cleaning device 426 removes residual toner remaining on the surface of the intermediate transfer belt 421 after secondary transfer.

The fixing section 60 includes an upper fixing section 60A having a fixing surface side member arranged on the fixing surface of the paper S, i.e., the surface on which the toner image is formed, a lower fixing section 60B having a back surface side support member arranged on the back surface of the paper S, i.e., the surface opposite the fixing surface, and a heating source. The back surface side support member is pressed against the fixing surface side member to form a fixing nip that clamps and transports the paper S.

The fixing unit 60 fixes the toner image onto the paper S by applying heat and pressure to the paper S, which has been transported and to which the toner image has been secondarily transferred, in the fixing nip. The fixing unit 60 is disposed as a unit within the fixing device F.

The upper fixing section 60A has an endless fixing belt 61, which is a fixing surface side member, a heating roller 62, and a fixing roller 63. The fixing belt 61 is stretched between the heating roller 62 and the fixing roller 63.

The fixing belt 61 comes into contact with the paper S on which the toner image has been formed, and heats the paper S to a fixing temperature (for example, 160 to 200°C). Here, the fixing temperature is a temperature that can supply the amount of heat required to melt the toner on the paper S, and differs depending on the type and basis weight of the paper S on which the image is formed.

The fixing belt 61 uses, for example, a 70 μm thick PI (polyimide) base, the outer surface of the base is covered with a 200 μm thick heat-resistant silicone rubber elastic layer, and the surface is further coated with PFA (perfluoroalkoxy), a heat-resistant resin. The outer diameter of the fixing belt 61 is, for example, 120 mm.

The heating roller 62 has a built-in halogen heater as a heat source for heating the fixing belt 61 and thus the fixing roller 63. The outer diameter of the heating roller 62 is, for example, 70 mm.

The fixing roller 63 is made of a solid core metal, for example, made of a metal such as iron, covered with a 20 mm thick heat-resistant silicone rubber (hardness JIS-A10°) elastic layer on the surface, and further covered with a resin layer coated with PTFE, a low-friction, heat-resistant resin. The outer diameter of the fixing roller 63 is, for example, 70 mm.

The lower fixing section 60B has a pressure roller 64, which is a back side support member. The pressure roller 64 presses the fixing roller 63 with a predetermined fixing load (e.g., 2200 N) via the fixing belt 61. In this way, the pressure roller 64 forms a fixing nip between the fixing roller 63 and the fixing belt 61 to sandwich and transport the paper S.

When the paper S passes through the fixing nip (when paper is passing through), the pressure roller 64 is pressed against the silicone rubber (elastic layer) of the fixing roller 63 via the fixing belt 61 by a pressing means (not shown), whereas when the paper S does not pass through the fixing nip (when paper is not passing through), the pressure roller 64 is separated from the silicone rubber of the fixing roller 63. The control unit 100 controls the drive of the pressure roller 64 (for example, turning the rotation on/off, the number of rotations, etc.).

The pressure roller 64 is made of a cylindrical core metal made of aluminum or the like, the outer surface of which is covered with a 3 mm thick elastic layer of heat-resistant silicone rubber (hardness JIS-A10°), and is further covered with a resin layer of a PFA tube. The outer diameter of the pressure roller 64 is, for example, 70 mm. The temperature of the pressure roller 64 is controlled to, for example, 80 to 120°C.

The paper transport section 50 includes a paper feed section 51, a paper discharge section 52, and a transport path section 53. The three paper feed tray units 51a to 51c that make up the paper feed section 51 store paper S (standard paper, special paper) identified based on basis weight, size, etc., by pre-set type.

The sheets S stored in the paper feed tray units 51a to 51c are sent out one by one from the top and transported to the image forming unit 40 by a transport mechanism equipped with multiple transport rollers such as the registration roller 53a. At this time, the registration unit in which the registration roller 53a is arranged corrects the inclination of the fed sheet S and adjusts the transport timing. Then, in the image forming unit 40, the toner image on the intermediate transfer belt 421 is transferred to one side of the sheet S, and a fixing process is performed in the fixing unit 60. The sheet S with the toner image fixed in the fixing process is discharged outside the image forming device 1 by the paper discharge unit 52 equipped with the paper discharge roller 52a.

3 is a diagram showing the peripheral configuration of the drum cleaning device 415. As shown in FIG. 3, the drum cleaning device 415 includes a cleaning blade 415a, a recovery screw 415b provided substantially below the cleaning blade 415a, a coating roller 415c (lubricant coating brush) provided downstream of the cleaning blade 415a in the rotation direction (arrow direction) of the photosensitive drum 413, a lubricant bar 415d that supplies lubricant to the coating roller 415c, a pressing unit (not shown) that presses and holds the lubricant bar 415d against the coating roller 415c, and a leveling blade 415e provided downstream of the coating roller 415c in the rotation direction of the photosensitive drum 413. The drum cleaning device 415 functions as the "lubricant coating device" of the present invention together with the control unit 100.

The cleaning blade 415a is made of an elastic material such as polyurethane rubber processed into a flat plate, and its tip is set so that it rubs against the photosensitive drum 413 to scrape off and remove any untransferred toner and other adhering matter remaining on the surface of the photosensitive drum 413.

In addition, a temperature detection sensor (not shown) capable of detecting the temperature around the photosensitive drum 413 is provided near the photosensitive drum 413.

The recovery screw 415b rotates in one direction and transports the toner that has been scraped off by the cleaning blade 415a and fallen to a waste toner box (not shown).

The application roller 415c is a roll-shaped brush member that is positioned so that its tip can contact the photosensitive drum 413. The application roller 415c rotates with the photosensitive drum 413 in the forward direction under the control of the control unit 100.

The lubricant rod 415d is made by melting and shaping a powdered lubricant of metal soap, such as zinc stearate, and solidifying it. The lubricant rod 415d is placed in a position where it can come into contact with the tip of the application roller 415c, and is scraped off from the tip by the rotation of the application roller 415c. The scraped off lubricant is transported directly to the photoconductor drum 413 and supplied to the surface of the photoconductor drum 413.

The pressing portion includes, for example, a compression spring that biases the lubricant rod 415d toward the application roller 415c, and presses and holds the lubricant rod 415d against the application roller 415c.

This pressing section is equipped with a pressing force sensor (not shown) that can detect the force of the compression spring (the pressing force of the lubricant rod 415d). The pressing force sensor may be, for example, a sheet-like sensor or a load cell. The remaining amount of the lubricant rod 415d is detected based on the detection result of the pressing force sensor.

The method for detecting the remaining amount of lubricant rod 415d is not limited to the method using a pressure sensor. For example, the remaining amount of lubricant rod 415d may be detected by detecting the position of a remaining amount detection lever (not shown) at the base end of lubricant rod 415d, which gradually moves as lubricant rod 415d is consumed. Also, the control unit 100 may be configured to estimate the remaining amount of lubricant rod 415d depending on the number of sheets of paper P on which images have been formed.

The leveling blade 415e (also called a fixed blade, which functions as the "coating member" of the present invention) is, like the cleaning blade 415a, a viscoelastic material such as polyurethane rubber processed into a flat plate. The leveling blade 415e is installed so that it contacts the surface of the photosensitive drum 413 at an angle in the direction in which it drags the surface of the photosensitive drum 413, and its tip rubs against the photosensitive drum 413. The leveling blade 415e spreads the lubricant powder supplied to the surface of the photosensitive drum 413, and forms a film on the surface of the photosensitive drum 413 to coat it, that is, it forms a film (lubricant layer).

In addition, the lubricant layer formed from zinc stearate has high releasability (high contact angle with pure water) and a small coefficient of friction, which allows for good transferability and cleaning properties, and also reduces wear on the photoconductor drum 413, resulting in a longer lifespan.

In order to extend the life of the image forming apparatus 1 (specifically, the image forming unit 41), it is necessary to improve the efficiency of lubricant application to the photoconductor drum 413 (≒amount of lubricant applied/amount of lubricant supplied) and reduce consumption of the lubricant rod 415d. Here, there are two factors that can reduce the efficiency of lubricant application: poor passage of the lubricant over the smoothing blade 415e, and poor coating of the lubricant by the smoothing blade 415e.

First, the failure of the lubricant to pass through the leveling blade 415e will be described. That is, not all of the lubricant (powder) applied by the application roller 415c and supplied to the leveling blade 415e is ultimately applied onto the photosensitive drum 413; approximately half of the supplied lubricant is blocked by the leveling blade 415e and falls into the unit (drum cleaning device 415) and remains unused. One of the reasons for the lubricant being blocked by the leveling blade 415e is that the contact force of the leveling blade 415e against the photosensitive drum 413 is high, which creates a large blocking force against the lubricant.

Next, we will explain the failure of the smoothing blade 415e to form a film on the lubricant. That is, the lubricant (powder) that passes through the smoothing blade 415e may pass through in powder form without being formed into a film. The lubricant that passes through in powder form is subsequently collected by the developing device 412 or transferred to the intermediate transfer belt 421, and remains unused.

The efficiency of lubricant application varies depending on the image formation conditions, particularly the ambient temperature during image formation. For example, in a low-temperature environment, the hardness of the smoothing blade 415e increases, the contact nip width between the photosensitive drum 413 and the smoothing blade 415e decreases, and the surface pressure of the smoothing blade 415e against the photosensitive drum 413 increases. This causes poor passage of the lubricant through the smoothing blade 415e. Furthermore, in a low-temperature environment, the viscosity of the lubricant powder decreases, and the extensibility when the smoothing blade 415e spreads the lubricant on the photosensitive drum 413 decreases. This causes poor coating of the lubricant by the smoothing blade 415e. In a high-temperature environment, the opposite state occurs to the low-temperature environment, so the efficiency of lubricant application decreases in a low-temperature environment and increases in a high-temperature environment.

When the lubricant application efficiency decreases, the thickness of the lubricant film formed on the photoconductor drum 413 deviates from the desired value and becomes smaller, which makes it more likely that problems (poor transfer, poor cleaning) will occur. Therefore, in order to maintain the lubricant film thickness at the desired value, the rotation speed of the application roller 415c is increased to increase the amount of lubricant applied (consumption) to the photoconductor drum 413, thereby increasing the amount of lubricant supplied to the smoothing blade 415e. However, even if the amount of lubricant supplied to the smoothing blade 415e increases and the amount of lubricant passing through increases, the amount of lubricant that fails to pass through also increases, which is detrimental to the long life of the image forming apparatus 1.

In addition, when the thickness of the lubricant film deviates from the desired value in a high-temperature environment, the cleaning performance improves, but the amount of external additive passing through the cleaning blade 415a decreases, and the polishing ability of foreign matter attached to the photoconductor drum 413 decreases. As a result, the amount of lubricant coated on the photoconductor drum 413 that can be removed by the external additive decreases, and an old lubricant layer accumulates on the photoconductor drum 413. The old lubricant layer is transformed into a deteriorated lubricant layer by exposure to ozone and nitrogen oxides generated by the charging device 414. The deteriorated lubricant layer is easily ionized by reacting with moisture in the air, which causes image defects such as image flow. Therefore, in order to suppress the increase in the thickness of the lubricant film in a high-temperature environment, the rotation speed of the application roller 415c is reduced to reduce the amount of lubricant applied (consumption) to the photoconductor drum 413. However, since the application roller 415c also has the function of removing the deteriorated lubricant layer, it is disadvantageous in suppressing image flow.

In this embodiment, therefore, the control unit 100 displaces (specifically, oscillates) the smoothing blade 415e in the axial direction of the photosensitive drum 413 in accordance with the image formation conditions during image formation, from the viewpoint of suppressing fluctuations in the thickness of the lubricant film formed on the photosensitive drum 413.

Figure 4 is a view of Figure 3 from the right side, showing a configuration in which the smoothing blade 415e is oscillated in the axial direction of the photosensitive drum 413 (left-right direction in the figure). In Figure 4, the upward arrow indicates the rotation direction (travel direction) of the photosensitive drum 413, and the left-right arrow indicates the oscillating movement of the smoothing blade 415e. Figure 4 shows the state in which the smoothing blade 415e has moved to the far right side.

The smoothing blade 415e is held by a holding portion 415f so as to be movable in the axial direction (longitudinal direction, left-right direction in the figure) of the photosensitive drum 413, and is pressed to the left in the figure via the holding portion 415f by a push-back spring 415g.

The smoothing blade 415e is in contact with an oscillating cam 415h, whose thickness changes continuously in the vertical direction in the figure, on the opposite side of the push-back spring 415g in the axial direction of the photosensitive drum 413. The oscillating cam 415h rotates in conjunction with the rotation of the oscillating motor 415i, and is arranged so that the amount of displacement of the smoothing blade 415e varies according to the rotation. The maximum amount of displacement of the smoothing blade 415e in the axial direction of the photosensitive drum 413 is the amplitude of the oscillation of the smoothing blade 415e (2 mm in this embodiment).

The control unit 100 can arbitrarily change the oscillation frequency Hz, which corresponds to the number of oscillations of the smoothing blade 415e per unit time, by changing the number of rotations per unit time of the oscillation motor 415i. In this embodiment, the control unit 100 sets the oscillation frequency of the smoothing blade 415e to any value between 0 Hz (oscillation stopped) and a maximum of 10 Hz, and rotates the oscillation motor 415i so that the smoothing blade 415e oscillates at the set oscillation frequency. The oscillation cam 415h and the oscillation motor 415i function as part of the "displacement unit" of the present invention.

When the smoothing blade 415e, which is a viscoelastic body, is oscillated, stress vibration occurs in the smoothing blade 415e, generating internal heat. Specifically, when periodic stress fluctuations are applied to a viscoelastic body, a phase difference occurs in the distortion corresponding to the stress. This phase difference is the internal attenuation of the added energy, and is converted internally into thermal energy. The larger the viscous component, the greater the internal attenuation and the greater the amount of internal heat generated. Furthermore, the greater the oscillation frequency and oscillation amplitude, the greater the phase difference and the greater the amount of internal heat generated.

In low-temperature environments, the decrease in the efficiency of lubricant application can be prevented by generating internal heat in the leveling blade 415e. This is because the internal heat generation in the leveling blade 415e can simulate a condition close to that of a high-temperature environment, which means that poor passage of the lubricant through the leveling blade 415e and poor coating of the lubricant by the leveling blade 415e are suppressed, improving the efficiency of lubricant application (i.e., the film thickness of the lubricant can be maintained at a desired value).

Even in conditions other than low temperature environments where the lubricant film thickness would normally become small and cannot be maintained at the desired value, such as when forming a high coverage image or when the remaining amount of lubricant rod 415d is low at the end of use of the unit (drum cleaning device 415), the lubricant film thickness can be maintained at the desired value by oscillating the leveling blade 415e.

Even in high temperature environments or in conditions where the lubricant film thickness normally becomes too large to be maintained at the desired value, such as when forming a low coverage image or when the remaining amount of lubricant on the lubricant rod 415d has not yet decreased during the initial period of use of the unit (drum cleaning device 415), the oscillation frequency of the smoothing blade 415e is reduced or the oscillation of the smoothing blade 415e is stopped, thereby preventing excessive application of lubricant and maintaining the lubricant film thickness at the desired value.

Next, an example of the control operation (corresponding to the "control method" of the present invention) of the image forming device 1 will be described with reference to the flowchart in FIG. 5. Note that the process shown in FIG. 5 is executed before the image forming device 1 executes a print job (image formation process).

First, the control unit 100 acquires the image formation conditions during image formation (step S100). Here, the image formation conditions are the temperature around the photoconductor drum 413, the density of the toner image formed on the photoconductor drum 413 based on the input image data (e.g., average coverage), and the usage history of the drum cleaning device 415 (e.g., usage ratio to the set life).

The control unit 100 acquires the temperature around the photosensitive drum 413 based on the detection result of a temperature detection sensor provided near the photosensitive drum 413. The control unit 100 also acquires the usage history of the drum cleaning device 415 based on the detection result of a pressure sensor capable of detecting the pressure of the lubricant rod 415d, and therefore the remaining amount of the lubricant rod 415d.

Next, the control unit 100 determines whether the temperature around the photoconductor drum 413 is equal to or lower than T1 (e.g., 15°C) (step S120). If the determination result is that the temperature is equal to or lower than T1, i.e., a low-temperature environment (step S120, YES), the control unit 100 sets the oscillation frequency of the smoothing blade 415e to F6 (e.g., 10 Hz) (step S140). After that, the process proceeds to step S380.

On the other hand, if the temperature is not equal to or lower than T1 (step S120, NO), the control unit 100 determines whether the temperature around the photoconductor drum 413 is equal to or higher than T2 (e.g., 30°C) (step S160). If the result of the determination is that the temperature is equal to or higher than T2, i.e., a high temperature environment (step S160, YES), the control unit 100 sets the oscillation frequency of the smoothing blade 415e to F0 (e.g., 0 Hz: oscillation stopped) (step S180). The process then transitions to step S380.

On the other hand, if the temperature is not equal to or greater than T2, i.e., T1<temperature<T2 (step S160, NO), the control unit 100 determines whether the density of the toner image formed on the photoconductor drum 413 is equal to or less than C1 (e.g., 10%) (step S200). If the result of the determination is that the density is equal to or less than C1, i.e., that a low-coverage toner image is formed (step S200, YES), the control unit 100 sets the oscillation frequency of the smoothing blade 415e to F1 (e.g., 1 Hz) (step S220). The process then transitions to step S380.

On the other hand, if the density is not equal to or less than C1 (step S200, NO), the control unit 100 determines whether the density of the toner image formed on the photoconductor drum 413 is equal to or greater than C2 (e.g., 40%) (step S240). If the determination result indicates that the density is equal to or greater than C2, i.e., that a high-coverage toner image is being formed (step S240, YES), the control unit 100 sets the oscillation frequency of the smoothing blade 415e to F5 (e.g., 7 Hz) (step S260). The process then transitions to step S380.

On the other hand, if the concentration is not equal to or greater than C2, i.e., C1<concentration<C2 (step S240, NO), the control unit 100 determines whether the usage history of the drum cleaning device 415 is equal to or less than U1 (e.g., 25%) (step S280). If the result of the determination is that the usage history is equal to or less than U1, i.e., the drum cleaning device 415 is in the early stages of use (step S280, YES), the control unit 100 sets the oscillation frequency of the smoothing blade 415e to F2 (e.g., 2 Hz) (step S300). The process then transitions to step S380.

On the other hand, if the usage history is not equal to or less than U1 (step S280, NO), the control unit 100 determines whether the usage history is equal to or greater than U2 (e.g., 75%) (step S320). If the result of the determination is that the usage history is equal to or greater than U2, i.e., the drum cleaning device 415 is in the final stages of use (step S320, YES), the control unit 100 sets the oscillation frequency of the smoothing blade 415e to F4 (e.g., 5 Hz) (step S340). The process then transitions to step S380.

On the other hand, if the usage history is not equal to or greater than U2, i.e., U1 < usage history < U2 (step S320, NO), the control unit 100 sets the oscillation frequency of the smoothing blade 415e to F3 (e.g., 3 Hz) (step S360). After that, the process proceeds to step S380.

In step S380, the control unit 100 controls the rotation operation of the oscillation motor 415i so that the smoothing blade 415e oscillates at the set oscillation frequency while the image forming device 1 is executing a print job (image forming process). Upon completion of the process of step S380, the image forming device 1 ends the process in FIG. 5.

As explained with reference to the flowchart in FIG. 5, the temperature around the photoconductor drum 413, the density of the toner image formed on the photoconductor drum 413, and the usage history of the drum cleaning device 415 are used as image forming conditions in this order, and the oscillation frequency is set according to the image forming conditions used to oscillate (displace) the smoothing blade 415e. The reason for prioritizing the temperature around the photoconductor drum 413, the density of the toner image formed on the photoconductor drum 413, and the usage history of the drum cleaning device 415 in descending order of priority is related to the difference in the degree of influence on the film thickness of the lubricant film formed on the photoconductor drum 413. In other words, the temperature around the photoconductor drum 413 has the greatest influence on the film thickness of the lubricant, and the usage history of the drum cleaning device 415 has the least influence.

Here, we will explain the effect of the density of the toner image formed on the photoconductor drum 413 on the thickness of the lubricant film. When the density of the toner image is high, the amount of toner that reaches the cleaning blade 415a increases. External additives are detached from the toner held back by the cleaning blade 415a, but because the external additives have a small particle size, they pass through without being held back by the cleaning blade 415a. The external additives are inorganic fine particles that also function as an abrasive, so they polish (remove) the lubricant layer on the photoconductor drum 413 as the cleaning blade 415a passes by. As a result, when the density of the toner image is high, the thickness of the lubricant film that is formed on the photoconductor drum 413 is reduced compared to when the density of the toner image is not high.

The effect of the usage history of the drum cleaning device 415 on the thickness of the lubricant film will be described. The lubricant rod 415d is pressed against the application roller 415c by a pressure spring, and as the drum cleaning device 415 is used, the lubricant rod 415d is consumed and its volume decreases, the displacement of the pressure spring decreases, and the pressure force decreases. The amount of lubricant applied to the photosensitive drum 413 (amount consumed) is proportional to the pressure of the lubricant rod 415d, and the thickness of the lubricant film formed on the photosensitive drum 413 is somewhat proportional to the amount of application. In other words, as the usage history of the drum cleaning device 415 increases, the amount of lubricant applied decreases, and the film thickness of the lubricant film formed also decreases. Even if the lubricant rod 415d presses against the application roller 415c by its own weight, the weight of the lubricant rod 415d decreases as it is consumed, so the film thickness of the lubricant film formed on the photosensitive drum 413 decreases.

As described above in detail, in this embodiment, the lubricant application device (drum cleaning device 415, control unit 100) includes a coating member (leveling blade 415e) that contacts the image carrier (photosensitive drum 413) and coats the lubricant applied to the image carrier, and a displacement unit (control unit 100, oscillating cam 415h, and oscillating motor 415i) that displaces the coating member in the axial direction of the image carrier according to the image formation conditions (e.g., the temperature around the photosensitive drum 413). Specifically, the displacement unit changes the amount of displacement of the coating member so that the film thickness of the coated lubricant becomes the desired value according to the image formation conditions.

According to this embodiment configured as described above, for example, in a low-temperature environment, it is possible to simulate a condition close to a high-temperature environment by generating internal heat in the smoothing blade 415e, thereby suppressing poor passage of the lubricant through the smoothing blade 415e and poor coating of the lubricant by the smoothing blade 415e, and maintaining the lubricant film thickness at a desired value.

Even in conditions other than low temperature environments where the lubricant film thickness would normally become small and cannot be maintained at the desired value, such as when forming a high coverage image or when the remaining amount of lubricant rod 415d is low at the end of use of the unit (drum cleaning device 415), the lubricant film thickness can be maintained at the desired value by oscillating the leveling blade 415e.

In addition, even in high temperature environments or in conditions where the lubricant film thickness normally becomes too large to be maintained at the desired value, such as when forming a low coverage image or when the remaining amount of lubricant on the lubricant rod 415d has not yet decreased during the initial period of use of the unit (drum cleaning device 415), the oscillation frequency of the smoothing blade 415e is reduced or the oscillation of the smoothing blade 415e is stopped, thereby preventing excessive application of lubricant and maintaining the lubricant film thickness at the desired value.

As a result, even if the image formation conditions change, fluctuations in the thickness of the lubricant film formed on the photoconductor drum 413 can be suppressed in response to the change. This makes it possible to reduce wasteful consumption of the lubricant rod 415d in low-temperature environments where the efficiency of lubricant application is reduced, thereby achieving a longer life for the image forming apparatus 1 (specifically, the image forming unit 41). Furthermore, by appropriately setting the oscillation frequency in high-temperature environments where the efficiency of lubricant application is high, the thickness of the lubricant film formed on the photoconductor drum 413 does not become excessive, and the occurrence of image flow can be suppressed.

The above embodiments are merely examples of the implementation of the present invention, and the technical scope of the present invention should not be interpreted in a limiting manner. In other words, the present invention can be implemented in various forms without departing from its gist or main features.

REFERENCE SIGNS LIST 1 Image forming apparatus 10 Image reading section 20 Operation display section 21 Display section 22 Operation section 30 Image processing section 40 Image forming section 50 Paper conveying section 60 Fixing section 63 Fixing roller 71 Communication section 72 Storage section 100 Control section 101 CPU
102 ROM
103 RAM
413 Photoconductor drum 415 Drum cleaning device 415a Cleaning blade 415b Recovery screw 415c Application roller 415d Lubricant rod 415e Leveling blade 415f Holding portion 415g Push-back spring 415h Oscillating cam 415i Oscillating motor

Claims (9)

a coating member that contacts the image carrier and coats the lubricant applied to the image carrier;
a displacement unit that displaces the coating member in an axial direction of the image carrier in response to image forming conditions including a density of a toner image formed on the image carrier ;
A lubricant application device comprising: the displacement unit stops the displacement of the coated member in response to the image forming conditions.
The lubricant application device according to claim 1. the image forming conditions further include an ambient temperature of the image carrier;
The lubricant application device according to claim 1 or 2. the image forming conditions include a usage history of the lubricant application device;
The lubricant application device according to any one of claims 1 to 3 . the displacement unit uses, as the image forming conditions, the temperature around the image carrier, the density of the toner image formed on the image carrier, and the usage history of the lubricant application device, in that order, and displaces the coated member according to the image forming conditions to be used.
The lubricant application device according to any one of claims 1 to 4 . the displacement unit changes the displacement amount of the coated member in response to the image forming conditions.
The lubricant application device according to any one of claims 1 to 5 . The displacement unit displaces the coated member so that the film thickness of the lubricant film becomes a desired value.
The lubricant application device according to any one of claims 1 to 6 . An image forming apparatus comprising the lubricant application device according to any one of claims 1 to 7 . 1. A control method for a lubricant application device having a coating member that contacts an image carrier and coats a lubricant applied to the image carrier, comprising:
acquiring image forming conditions including a density of a toner image formed on the image carrier ;
displacing the coating member in an axial direction of the image carrier in accordance with the acquired image forming conditions;
Control methods.