JP2023168931A - Developing device and image forming apparatus - Google Patents

Abstract

To firmly join a driving member to an image carrier, and prevent printing failure due to attachment of an adhesive to a gear part.SOLUTION: A developing device 10 comprises: a photoreceptor drum 11 that carries an electrostatic latent image and is rotatable centered on a rotation axis (Ax); a developing roller 13 that develops the electrostatic latent image; and a driving member 80 that is joined to the photoreceptor drum 11 by an adhesive. The driving member 80 has a fitting part 82 fitted to the photoreceptor drum 11, and a gear part 81. The fitting part 82 has a recess 85 extending in a circumferential direction centered on the rotation axis Ax, and the adhesive is attached to the recess 85. The recess 85 is provided at a position separated from the gear part 81.SELECTED DRAWING: Figure 9

Description

The present disclosure relates to a developing device that develops an electrostatic latent image, and an image forming apparatus equipped with the developing device.

In an image forming apparatus using an electronic process, the surface of an image bearing member such as a photoreceptor drum is uniformly charged, an electrostatic latent image is formed by exposure, and this electrostatic latent image is developed with a developer. , transfer to a medium.

The image carrier has a cylindrical shape, and a drive member for rotating the image carrier is provided at an axial end of the image carrier. The drive member includes a gear portion and a fitting portion that fits inside the image carrier. The fitting portion is joined to the image carrier using an adhesive (for example, see Patent Document 1).

Japanese Patent Application Laid-Open No. 9-187820 (see Figures 1 to 3)

However, with the above configuration, the adhesive for bonding the fitting portion to the image carrier may adhere to the gear portion, resulting in printing defects.

The present disclosure has been made in order to solve the above problems, and aims to firmly bond a driving member to an image carrier and suppress the occurrence of printing defects due to adhesive adhesion. .

The developing device of the present disclosure includes an image carrier that carries an electrostatic latent image and is rotatable about a rotation axis, a developer carrier that develops the electrostatic latent image, and an adhesive attached to an end of the image carrier. and a driving member joined by. The drive member includes a fitting portion that fits into the image carrier and a gear portion. The fitting portion has a recess extending in a circumferential direction centered on the rotation axis, and the adhesive adheres to the recess. The recessed portion is provided at a position away from the gear portion.

According to the present disclosure, since the adhesive is accommodated in the recess provided at a position away from the gear part in the fitting part, adhesion of the adhesive to the gear part is suppressed, thereby causing printing defects. can be suppressed.

1 is a diagram showing the configuration of an image forming apparatus according to an embodiment. FIG. 1 is a diagram showing the configuration of a developing device according to an embodiment. 1 is a block diagram showing a control system of an image forming apparatus according to an embodiment. FIG. FIG. 3 is a diagram showing a cross-sectional structure of a developing roller according to an embodiment. FIGS. 3A and 3B are schematic diagrams illustrating a method for measuring the resistance of a developing roller. FIGS. It is a figure showing the cross-sectional structure of the supply roller of an embodiment. FIGS. 3A and 3B are diagrams illustrating a cross-sectional structure of a photoreceptor drum according to an embodiment. FIGS. FIG. 2 is a perspective view showing a support structure for a photoreceptor drum and a developing roller according to an embodiment. FIG. 2 is a cross-sectional view (A) of a photoreceptor drum according to an embodiment, and a cross-sectional view (B) showing an enlarged portion of a driving member. It is a perspective view showing a drive member of an embodiment. FIGS. 8A and 7B are diagrams illustrating a joint portion between a photosensitive drum and a driving member in an embodiment and a comparative example; FIGS. FIGS. 2A and 2B are schematic diagrams illustrating a method for measuring the feed force between a photoreceptor drum and a developing roller. FIGS. FIG. 3 is a schematic diagram showing a method of measuring the force for removing the driving member from the photoreceptor drum.

<Configuration of image forming apparatus>
FIG. 1 is a diagram showing an image forming apparatus 1 according to an embodiment. The image forming apparatus 1 forms an image using an electrophotographic process, and is a printer here. The image forming apparatus 1 includes a medium supply section 50, a developing device 10, a fixing device 60, a medium discharge section 65, and a housing 1A that accommodates these.

The media supply unit 50 includes a media tray 51 that stores media P such as printing paper, a paper feed roller 52 that feeds the media P in the media tray 51 one by one to a conveyance path, and a developer that develops the medium P that has been sent out to the conveyance path. It has a conveyance roller 53 that conveys the medium P to the apparatus 10, and a medium guide 54 that guides the medium P that is conveyed.

The developing device 10 is disposed at a position to receive the medium P from the medium supply section 50, and has a photosensitive drum 11 as an image carrier. An LED head 21 serving as an exposure device is arranged so as to face the photoreceptor drum 11 . The LED head 21 includes an LED array in which LEDs (light emitting diodes) as light emitting elements are arranged and a lens array, and irradiates the surface of the photoreceptor drum 11 with light to form an electrostatic latent image. The LED head 21 is suspended and supported by a top cover 1B that covers the upper part of the housing 1A.

<Configuration of developing device>
FIG. 2 is a diagram showing the configuration of the developing device 10. As shown in FIG. The developing device 10 includes the above-described photosensitive drum 11 and a developing roller 13 as a developer carrier. The developing device 10 further includes a charging roller 12 as a charging member, a supply roller 14 as a supply member, a developing blade 15 as a layer regulating member, a cleaning member 16, and a housing 17 that houses these. . A toner cartridge 18 serving as a developer storage body is attached to the housing 17 .

Note that the developing device 10 does not need to include all of the above-mentioned components, and only needs to include at least the photosensitive drum 11 as an image carrier and the developing roller 13 as a developer carrier. In addition, a charging roller 12 as a charging member, a supply roller 14 as a supply member, and a developing blade 15 as a layer regulating member may be provided. Furthermore, a cleaning member 16, a housing 17, and a toner cartridge 18 as a developer storage body may be included.

The photosensitive drum 11 is a cylindrical member in which a charge generation layer and a charge transport layer are laminated on the surface of a conductive support, and rotates clockwise in the figure. The photosensitive drum 11 carries an electrostatic latent image on its surface. Details of the configuration of the photosensitive drum 11 will be described later.

The charging roller 12 is arranged so as to be in contact with the photoreceptor drum 11 and rotates following the photoreceptor drum 11 . A charging voltage is applied to the charging roller 12 from a charging roller power source 36 (FIG. 3), and the surface of the photoreceptor drum 11 is uniformly charged.

The developing roller 13 is arranged so as to be in contact with the surface of the photoreceptor drum 11, and rotates in a direction opposite to that of the photoreceptor drum 11 (a direction in which the direction of movement of the surface at the contact portion is the forward direction). The developing roller 13 is applied with a developing voltage from a developing roller power source 37 (FIG. 3), and develops the electrostatic latent image on the surface of the photoreceptor drum 11 with toner (developer).

The supply roller 14 is arranged so as to be in contact with the surface of the developing roller 13, and rotates in the same direction as the developing roller 13 (in the direction in which the direction of movement of the surface at the contact portion is opposite). The supply roller 14 is applied with a supply voltage from a supply roller power source 38 (FIG. 3), and supplies toner to the developing roller 13.

The developing blade 15 is a blade arranged so as to be in contact with the surface of the developing roller 13. A blade voltage is applied to the developing blade 15 from a developing blade power supply 39 (FIG. 3), and regulates the toner layer on the surface of the developing roller 13 to a constant thickness.

The toner cartridge 18 is a container that stores toner (indicated by the symbol T) as a developer. The toner T is, for example, a black toner, but is not limited thereto. The toner cartridge 18 is removably attached to the upper part of the housing 17 and supplies toner T to the developing roller 13 and the supply roller 14.

A toner storage section that stores toner T supplied from the toner cartridge 18 is formed in the housing 17 above the developing roller 13 and the supply roller 14 . Crank-shaped stirring bars 19a, 19b, and 19c are arranged in the toner storage section. The stirring bars 19a, 19b, and 19c rotate in the directions indicated by arrows, respectively, to stir and convey the toner T.

The cleaning member 16 is a blade or a roller disposed so as to be in contact with the surface of the photoreceptor drum 11, and scrapes off toner remaining on the surface of the photoreceptor drum 11. The waste toner scraped off by the cleaning member 16 is conveyed to a waste toner collection section by a conveyance screw (not shown).

Note that the developing device 10 is also referred to as an image carrier unit or an image forming unit. Further, a portion of the developing device 10 that includes at least the developing roller 13 and the supply roller 14 (a portion that contributes to the development of the electrostatic latent image) is also referred to as a developing section.

As shown in FIG. 1, a transfer roller 20 as a transfer member is arranged so as to be in contact with the surface of the photoreceptor drum 11. As shown in FIG. A transfer voltage is applied to the transfer roller 20 from a transfer roller power source 40 (FIG. 3). This transfer voltage causes the toner image on the surface of the photoreceptor drum 11 to be transferred to the medium P passing between the photoreceptor drum 11 and the transfer roller 20 .

The image forming apparatus 1 forms a monochromatic image using the developing device 10, but is not limited to this example. A plurality of developing devices for yellow, magenta, cyan, black, etc. may be arranged in the transport direction of the medium P to form a color image.

The fixing device 60 is arranged downstream of the developing device 10 in the conveyance direction of the medium P. The fixing device 60 includes a fixing roller 61 and a pressure roller 62. The fixing roller 61 has a built-in heater such as a halogen lamp. The pressure roller 62 is pressed against the fixing roller 61 to form a fixing nip. The fixing roller 61 and the pressure roller 62 apply heat and pressure to the medium P passing through the fixing nip to fix the toner image on the medium P.

The medium discharge section 65 is arranged downstream of the fixing device 60 in the conveyance direction of the medium P. The medium discharge section 65 includes a discharge roller 66 that discharges the medium P that has passed through the fixing device 60 from the discharge port, and a medium guide 67 that guides the medium P from the fixing device 60 to the discharge port. A stacker 68 on which the discharged medium P is placed is formed on the top cover 1B.

In FIG. 1, the axial direction of the photoreceptor drum 11 is assumed to be the X direction. The X direction is the axial direction of each roller in the image forming apparatus 1, and is also the width direction of the medium P being transported. The moving direction of the medium P when the medium P passes through the developing device 10 is assumed to be the Y direction. The direction perpendicular to the X direction and the Y direction is defined as the Z direction. Here, the Z direction is the vertical direction.

<Control system of image forming apparatus>
FIG. 3 is a block diagram showing a control system of the image forming apparatus 1. As shown in FIG. The image forming apparatus 1 includes a print control section 30, an I/F (interface) control section 31, a reception memory 32, an image data editing memory 33, a head control section 41, a fixing control section 42, and a fixing drive control section. 43, a transport control section 44, and a drive control section 45. These control units and memory constitute a control device.

The print control unit 30 includes a microprocessor, a ROM (Read Only Memory), a RAM (Random Access Memory), an input/output port, a timer, and the like. The print control unit 30 receives print data and control commands from the host device via the I/F control unit 31, and executes the print operation of the image forming apparatus 1.

An operation signal from the operation unit 34 and a detection signal from the sensor group 35 are input to the print control unit 30 . The operation unit 34 includes an operation unit such as a switch that accepts a user's operation, and a display unit such as an LED that displays the status of the image forming apparatus 1. The sensor group 35 includes, for example, a medium sensor that detects the position of the medium P on the conveyance path, a temperature/humidity sensor that detects ambient temperature and humidity, a remaining toner amount sensor that detects the amount of toner remaining in the developing device 10, and the like.

The reception memory 32 temporarily stores print data input from a host device via the I/F control unit 31. The image data editing memory 33 receives the print data stored in the reception memory 32 and records image data, that is, image data, formed by editing the print data.

The print control unit 30 also controls the charging voltage applied to the charging roller 12 from the charging roller power supply 36, the developing voltage applied to the developing roller 13 from the developing roller power supply 37, and the supply roller voltage applied from the supply roller power supply 38. 14, the blade voltage applied to the developing blade 15 from the developing blade power source 39, and the transfer voltage applied to the transfer roller 20 from the transfer roller power source 40.

The head control unit 41 controls each LED of the LED head 21 to emit light based on the image data recorded in the image data editing memory 33.

The fixing control unit 42 has a temperature adjustment circuit, and supplies current to a heater in the fixing roller 61 based on an output signal from a temperature sensor such as a thermistor provided in the fixing device 60. The fixing drive control section 43 controls the rotation of the fixing motor 63 that rotationally drives the fixing roller 61. Note that the discharge roller 66 is rotated by rotation transmission from the fixing motor 63.

The conveyance control unit 44 controls the rotation of the conveyance motor 46 that drives the paper feed roller 52 and the conveyance roller 53. The rotation of the transport motor 46 is transmitted to the paper feed roller 52 and the transport roller 53 via an electromagnetic clutch (not shown) or the like.

The drive control unit 45 controls the rotation of a drive motor (drum motor) 47 that rotationally drives the photoreceptor drum 11 . Note that the rotation of the photosensitive drum 11 is also transmitted to the developing roller 13 and the supply roller 14 via a gear train (not shown). Furthermore, the charging roller 12 rotates following the photosensitive drum 11.

<Configuration of each component of the developing device>
Next, the configuration of each component of the developing device 10 will be described in detail.

<Developing roller>
First, the developing roller 13 will be explained. FIG. 4 is a diagram showing a cross-sectional structure of the developing roller 13. The developing roller 13 includes a conductive core (shaft) 13a, an elastic layer 13b formed on the surface of the core 13a, and a surface layer 13c covering the surface of the elastic layer 13b. The core metal 13a may be made of any material having good conductivity, for example, iron, aluminum, stainless steel, or the like.

As the material of the elastic layer 13b, general rubber materials such as silicone rubber and urethane can be used. When polyurethane is used as the elastic layer 13b, it is preferably polyurethane containing polyether polyol as a main component. Ether polyurethane is a so-called cast-type polyurethane obtained by reacting a polyol mainly composed of polyether polyol and polyisocyanate. This is to reduce the compression set. On the other hand, when ester polyurethane is used, its hydrolysis properties are poor and it cannot be used stably over a long period of time.

When polyurethane is used as the elastic layer 13b, examples of the isocyanate to be reacted with the polyol include simple trifunctional isocyanates such as triphenylmethane triisocyanate, tris (isocyanate phenyl) thiophosphate, and bicycloheptane triisocyanate, and hexamethylene diisocyanate. A mixture of nerate-modified polyisocyanate, polymeric MDI, etc. can be used.

Moreover, it is good also as a mixture of these trifunctional or more functional polyisocyanates and a general bifunctional isocyanate compound. Examples of difunctional isocyanate compounds include 2,4-tolylene diisocyanate (TDI), 4,4-diphenylmethane diisocyanate (MDI), paraphenylene diisocyanate (PPDI), 1,5-naphthalene diisocyanate (NDI), 3,3- Examples include dimethyldiphenyl-4,4-diisocyanate (TODI) and modified products and polymers of prepolymers having these isocyanates at both ends.

The elastic layer 13b is formed by adding carbon black to the above-described rubber base material and heating and curing the mixture while maintaining the carbon dispersion state. As a result, carbon black, which exhibits a specific resistance of about 0.1 to 10 [Ωcm], is dispersed in an elastomer (10 ¹² to 10 ¹⁶ [Ωcm]), which can be called an insulator, and has a resistivity of 10 ⁴ to 10 ⁸ [Ω .cm] can be formed to be stable.

The surface layer 13c is formed, for example, by impregnating the surface layer portion of the elastic layer 13b with a surface treatment liquid. The surface treatment liquid is one in which at least an isocyanate component is dissolved in an organic solvent. Examples of the organic solvent include methyl acetate, butyl acetate, pentyl acetate, and the like. When using such an organic solvent, for example, as an isocyanate component contained in the surface treatment liquid, isocyanate compounds such as 2,4-tolylene diisocyanate (TDI) and 4,4-diphenylmethane diisocyanate (MDI), and large amounts of these are used. body, modified body, etc. can be used.

The surface treatment liquid may contain a polyether polymer. The polyether polymer is preferably soluble in an organic solvent, and preferably has active hydrogen and is capable of chemically bonding with the isocyanate compound by reacting with it. Suitable polyether polymers having active hydrogen include polymers having hydroxyl groups or allyl groups, such as polyols and glycols used in terminal isocyanate prepolymers.

Further, the surface treatment liquid may contain a polymer selected from acrylic fluorine-based polymers and acrylic silicone-based polymers. The acrylic fluorine-based polymer and the acrylic silicone-based polymer are soluble in a predetermined solvent and can be chemically bonded by reacting with an isocyanate compound. The acrylic fluoropolymer is, for example, a solvent-soluble fluoropolymer having a hydroxyl group, an alkyl group, or a carboxyl group, and includes, for example, a block copolymer of an acrylic acid ester and a fluorinated alkyl acrylate, and derivatives thereof. Further, the acrylic silicone polymer is a solvent-soluble silicone polymer, and includes, for example, a block copolymer of an acrylic acid ester and an acrylic acid siloxane ester, and derivatives thereof.

Further, carbon black such as acetylene black may be further added to the surface treatment liquid as a conductivity imparting material.

Regarding the polyether polymer, acrylic fluorine polymer, and acrylic silicone polymer in the surface treatment liquid, the total amount of the polyether polymer, acrylic fluorine polymer, and acrylic silicone polymer is 10 to 70 [mass%] based on the isocyanate component. It is preferable to do so. If it is less than 10 [mass%], the effect of retaining carbon black etc. in the surface treatment liquid will be reduced. On the other hand, if it exceeds 70 [mass%], there is a problem that the electrical resistance value increases or the isocyanate component becomes relatively small, making it impossible to form an effective surface treatment layer.

By applying the elastic layer 13b by dipping it in the above-mentioned surface treatment liquid and drying and hardening it, the surface layer portion of the elastic layer 13b is impregnated with the surface treatment liquid to form the surface layer 13c.

The resistance value of the developing roller 13 is measured by the method shown in FIGS. 5(A) and 5(B). As the measuring device 25, a high resistance meter (model number: 4339B) manufactured by Hewlett-Packard was used. As shown in FIG. 5(A), the developing roller 13 was brought into contact with a stainless steel metal roller 26 having a diameter of 30 [mm] with a load of W=300 [g] applied to both ends in the axial direction.

A potential difference of -100 [V] was applied to the core metal 13a of the developing roller 13 with respect to the shaft portion 27 of the metal roller 26, and the metal roller 26 was rotated at a speed of 50 [rpm]. Then, the resistance was measured at 100 points per revolution of the developing roller 13, and the average value was taken as the resistance value of the developing roller 13. The resistance value of the developing roller 13 is preferably 1×10 ⁴ to 1×10 ⁷ [Ω], and the developing roller 13 having a resistance value of 1×10 ⁵ [Ω] was used here.

The rubber hardness (Asker C hardness) of the developing roller 13 is preferably 55 to 85 degrees. If the Asker C hardness of the developing roller 13 is lower than 55 [degrees], dents may be formed in the contact area between the developing roller 13 and the photosensitive drum 11 or the developing blade 15 when the developing device 10 is stopped for a long period of time. This may cause horizontal streaks to appear in the image. When the Asker C hardness of the developing roller 13 is higher than 85 [degrees], the mechanical load applied to the developing roller 13 increases, and toner adhesion (referred to as filming) is likely to occur on the surface of the developing roller 13.

<Developing blade>
The developing blade 15 shown in FIG. 2 is a plate-shaped member made of stainless steel, and has a thickness of, for example, 0.08 [mm]. The developing blade 15 is bent at its contact portion with the developing roller 13, and the radius of curvature of the bent portion is approximately 0.18 [mm]. The pressure (linear pressure) between the developing blade 15 and the developing roller 13 is about 40 [gf/cm].

In view of the setting conditions of the developing blade 15, the surface roughness, resistance value, etc. of the developing roller 13 are set in order to set the toner layer thickness and toner charge amount on the developing roller 13 to desired amounts. The surface roughness of the developing roller 13 is preferably such that the ten-point average roughness Rz (JIS B0601-1994) in the circumferential direction is 2 to 10 [μm].

<Supply roller>
Next, the supply roller 14 will be explained. FIG. 6 is a sectional view showing the supply roller 14. As shown in FIG. The supply roller 14 has a conductive core (shaft) 14a and a sponge-like foamed elastic layer 14b formed on the surface of the core 14a. The core metal 14a may be made of any material having good conductivity, for example, iron, aluminum, stainless steel, or the like.

The rubber composition forming the foamed elastic layer 14b contains rubber, a foaming agent, and a conductivity imparting agent, and further contains additives as necessary. The rubber is preferably silicone rubber or silicone-modified rubber, which has excellent heat resistance and charging characteristics. The foaming agent may be any foaming agent used for foamed rubber. Examples of inorganic blowing agents include sodium bicarbonate and ammonium carbonate. Examples of the organic blowing agent include organic azo compounds such as diazoamino derivatives, azonitrile derivatives, and azodicarboxylic acid derivatives. An inorganic foaming agent is used when forming continuous cells in the foamed elastic layer 14b, and an organic foaming agent is used when forming closed cells. Examples of additives include fillers, colorants, mold release agents, and the like.

<Cleaning member>
The cleaning member 16 includes a plate-shaped elastic body and a conductive plate-shaped holder for holding the elastic body.

The material for the plate-like elastic body is not particularly limited, but an elastic body composition may be used to prevent the surface of the photoreceptor drum 11 from being damaged when it comes into sliding contact with the surface of the photoreceptor drum 11 to scrape off residual toner. It is preferable to use Examples include compositions in which additives are blended with polyurethane, silicone resins, fluororesins, fluororubbers, and the like. In particular, polyurethane compositions that are excellent in mechanical strength and elastic pressability are preferred.

The above polyurethane composition can be obtained using a polyisocyanate, a polyol, a curing agent, and a catalyst.

Examples of the polyisocyanate include, but are not limited to, 4,4'-diphenylmethane diisocyanate (MDI), 2,4-tolylene diisocyanate (2,4-TDI), and 2,6-tolylene diisocyanate (2,4-tolylene diisocyanate). , 6-TDI), 3,3'-tolylene-4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 2,4-tolylene diisocyanate uretidinedione (2,4- TDI dimer), 1,5-naphthylene diisocyanate, metaphenylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate (water-added MDI), carbodiimide-modified MDI, orthotoluidine diisocyanate, xylene diisocyanate , diisocyanates such as para-phenylene diisocyanate and lysine diisocyanate methyl ester, triisocyanates such as triphenylmethane-4,4',4''-triisocyanate, and polymeric MDI.These may be used alone or in combination of two or more. MDI is particularly preferred from the viewpoint of wear resistance.

In addition, the polyol used together with the above polyisocyanate is not particularly limited, but includes, for example, polyester polyols such as polyethylene adipate (PEA), polybutylene adipate (PBA), and polyhexylene adipate, polycaprolactone, and polyoxylene adipate. Polyether polyols such as tetramethylene glycol and polyoxypropylene glycol can be used. These may be used alone or in combination of two or more. In particular, PBA is preferred because it has excellent wear resistance.

The curing agent used with the polyisocyanate and polyol is not particularly limited, but includes 1,4-butanediol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, hexanediol, 1,4-cyclohexanediol, Polyols having a molecular weight of 300 or less, such as 1,4-cyclohexanedimethanol, xylene glycol, triethylene glycol, trimethylolpropane, glycerin, pentaerythritol, sorbitol, and 1,2,6-hexanetriol, can be used. These may be used alone or in combination of two or more.

The linear pressure of the cleaning member 16 against the photosensitive drum 11 is preferably 15 [gf/cm] or more and 30 [gf/cm] or less, and here it is set to 20 [gf/cm]. Further, the cleaning angle was set to be 10 [°] or more and 15 [°] or less.

<Photoreceptor drum>
Next, the photosensitive drum 11 will be explained. FIG. 7(A) is a diagram showing a cross-sectional structure of the photoreceptor drum 11. The photosensitive drum 11 is a cylindrical member, and a driving member 80 is attached to one end in the X direction, and a flange member 70 is attached to the other end.

The photosensitive drum 11 has a raw tube 111 that is a conductive support. As shown in an enlarged view in FIG. 7(B), an undercoat layer 112 and a photosensitive layer 113 are laminated in this order on the surface of the raw tube 111. The photosensitive layer 113 is composed of a laminate of a charge generation layer 114 and a charge transport layer 115.

As the undercoat layer 112, for example, a material in which particles of metal oxide or the like are dispersed in a binder resin is used. The undercoat layer 112 may be composed of a single layer or a plurality of layers.

Examples of metal oxide particles used in the undercoat layer 112 include metal oxide particles containing one type of metal element such as titanium oxide, aluminum oxide, silicon oxide, zirconium oxide, zinc oxide, and iron oxide, calcium titanate, Examples include metal oxide particles containing multiple metal elements such as strontium titanate and barium titanate. One type of these may be used alone, or two or more types may be used in any ratio and combination.

Among these metal oxide particles, titanium oxide and aluminum oxide are preferred, and titanium oxide is particularly preferred. The surface of the titanium oxide particles may be treated with an inorganic substance such as tin oxide, aluminum oxide, antimony oxide, zirconium oxide, or silicon oxide, or an organic substance such as stearic acid, polyol, or silicone.

Any one type of these treatments may be used, or two or more types may be applied. As the crystal type of the titanium oxide particles, for example, any of rutile, anatase, brookite, and amorphous can be used. Note that the titanium oxide particles may have only one type of crystal type, or may contain two or more types of crystal types in any ratio and combination.

The particle size of the metal oxide particles is arbitrary as long as it does not significantly impair the effects of the present disclosure, but from the viewpoint of the properties of the binder resin of the undercoat layer 112 and the stability of the solution, it is preferable that the average primary particle size is 10 [nm]. ] or more and 100 [nm] or less, preferably 50 [nm] or less. This average primary particle size can be measured using, for example, a transmission electron microscope (TEM).

The undercoat layer 112 is preferably formed, for example, by dispersing metal oxide particles in a solution in which a binder resin is dissolved, and applying this solution onto the base tube 111. Examples of the binder resin used for the undercoat layer 112 include epoxy resin, polyethylene resin, polypropylene resin, acrylic resin, methacrylic resin, polyamide resin, vinyl chloride resin, vinyl acetate resin, phenol resin, polycarbonate resin, polyurethane resin, Polyimide resin, vinylidene chloride resin, polyvinyl acetal resin, vinyl chloride-vinyl acetate copolymer, polyvinyl alcohol resin, polyurethane resin, polyacrylic acid resin, polyacrylamide resin, polyvinylpyrrolidone resin, polyvinylpyridine resin, water-soluble polyester resin, nitro Cellulose ester resins such as cellulose, cellulose ether resins, casein, gelatin, polyglutamic acid, starch, starch acetate, amino starch, organic zirconium compounds such as zirconium chelate compounds, zirconium alkoxide compounds, organic titanyl compounds such as titanyl chelate compounds, titanyl alkoxide compounds, etc. compounds, silane coupling agents, and the like. One type of these may be used alone, or two or more types may be used in any ratio and combination. Further, it may be used in a cured form together with a curing agent. In particular, alcohol-soluble copolyamides, modified polyamides, and the like are preferred because they exhibit good dispersibility and coating properties.

The structure of the photosensitive layer 113 may be any structure applicable to known electrophotographic photoreceptors. Specific examples include a single-layer photoreceptor having a single-layer photosensitive layer (i.e., a single-layer photosensitive layer) in which a photoconductive material is dissolved or dispersed in a binder resin, and a charge generating material containing a charge-generating substance. Examples include a laminated photoreceptor having a photosensitive layer (that is, a laminated photosensitive layer) formed of a plurality of layers formed by laminating a generation layer and a charge transport layer containing a charge transporting substance. In general, it is known that photoconductive materials exhibit equivalent performance whether they are of a single-layer type or a laminated type.

The photosensitive layer 113 of the photosensitive drum 11 according to the present embodiment may be in any known form, but should be made in consideration of the mechanical properties, electrical properties, manufacturing stability, etc. of the electrophotographic photosensitive member. , a laminated type electrophotographic photoreceptor is preferred. In particular, a sequentially laminated photoreceptor in which a charge generation layer 114 and a charge transport layer 115 are laminated in this order on a raw tube 111 is more preferable.

When forming the charge transport layer 115 of a laminated photoconductor (functionally separated photoconductor) and the photosensitive layer of a single-layer photoconductor, a binder is used to disperse the compound in order to ensure film strength. used. The charge transport layer of the functionally separated photoreceptor can be obtained by dissolving or dispersing a charge transport substance and various binder resins in a solvent, applying a coating solution, and drying the coating solution. Further, a single-layer type photoreceptor can be obtained by coating and drying a coating liquid obtained by dissolving or dispersing a charge generating substance, a charge transporting substance, and various binder resins in a solvent.

Examples of the binder resin used for the charge generation layer 114 of the functionally separated photoreceptor include polyvinyl butyral resin, polyvinyl formal resin, partially acetalized polyvinyl butyral resin in which a portion of butyral is modified with formal, acetal, etc. Polyvinyl acetal resin, polyarylate resin, polycarbonate resin, polyester resin, modified ether polyester resin, phenoxy resin, polyvinyl chloride resin, polyvinylidene chloride resin, polyvinyl acetate resin, polystyrene resin, acrylic resin, methacrylic resin, poly Acrylamide resin, polyamide resin, polyvinylpyridine resin, cellulose resin, polyurethane resin, epoxy resin, silicone resin, polyvinyl alcohol resin, polyvinylpyrrolidone resin, casein, vinyl chloride-vinyl acetate copolymer, hydroxy-modified vinyl chloride-vinyl acetate copolymer Polymers, carboxyl-modified vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinyl acetate copolymers such as vinyl chloride-vinyl acetate-maleic anhydride copolymers, styrene-butadiene copolymers, vinylidene chloride-acrylonitrile copolymers Select from among polymers, insulating resins such as styrene-alkyd resins, silicone-alkyd resins, and phenol-formaldehyde resins, and organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, and polyvinylperylene. However, it is not limited to these polymers. Further, these binder resins may be used alone or in combination of two or more in any ratio.

Examples of the binder resin used in the charge transport layer 115 include polyvinyl acetal resin, polyarylate resin, polycarbonate resin, polyester resin, modified ether polyester resin, phenoxy resin, polyvinyl chloride resin, and polyvinylidene chloride resin. , polyvinyl acetate resin, polystyrene resin, acrylic resin, methacrylic resin, polyacrylamide resin, polyamide resin, polyvinylpyridine resin, cellulose resin, polyurethane resin, epoxy resin, silicone resin, polyvinyl alcohol resin, polyvinylpyrrolidone resin, casein, chloride These include vinyl-vinyl acetate copolymers, styrene-butadiene copolymers, vinylidene chloride-acrylonitrile copolymers, styrene-alkyd resins, silicone-alkyd resins, phenol-formaldehyde resins, and organic photoconductive resins. Vinyl chloride-vinyl acetate copolymers include, for example, vinyl chloride-vinyl acetate copolymers, hydroxy-modified vinyl chloride-vinyl acetate copolymers, carboxyl-modified vinyl chloride-vinyl acetate copolymers, and vinyl chloride-vinyl acetate copolymers. Maleic anhydride copolymer, etc. Examples of organic photoconductive resins include poly-N-vinylcarbazole, polyvinylanthracene, and polyvinylperylene.

The charge transport layer 115 contains, for example, at least one kind of charge transport substance. The type of charge transport substance is not particularly limited, and examples thereof include aromatic amine derivatives, stilbene derivatives, butadiene derivatives, hydrazone derivatives, carbazole derivatives, aniline derivatives, and enamine derivatives. Further, the charge transport substance may be, for example, a compound in which one or more of the aromatic amine derivatives described above are combined. Further, the charge transport substance may be, for example, a polymer (electron-donating material) having a group made of the above-mentioned aromatic amine derivative or the like as a main chain or a side chain. Among these, the charge transport substance is preferably an aromatic amine derivative, a stilbene derivative, a hydrazone derivative, an enamine derivative, or a compound in which one or more of them are combined. More preferably, the compound is a compound bound to a derivative.

Each layer constituting the photoreceptor drum 11 is formed by repeating the coating and drying process for each layer using a known coating method on the raw tube 111 with a coating liquid containing the material constituting each layer. Examples of the solvent (dispersion medium) used to dissolve the binder resin and prepare the coating solution include saturated aliphatic solvents such as pentane, hexane, octane, and nonane, and aromatic solvents such as toluene, xylene, and anisole. , halogenated aromatic solvents such as chlorobenzene, dichlorobenzene, and chloronaphthalene; amide solvents such as dimethylformamide and N-methyl-2-pyrrolidone; alcoholic solvents such as methanol, ethanol, isopropanol, n-butanol, and benzyl alcohol. , glycerin, aliphatic polyhydric alcohols such as polyethylene glycol, linear, branched and cyclic ketone solvents such as acetone, cyclohexanone, methyl ethyl ketone, 4-methoxy-4-methyl-2-pentanone, methyl formate, ethyl acetate, acetic acid. Ester solvents such as n-butyl, halogenated hydrocarbon solvents such as methylene chloride, chloroform, and 1,2-dichloroethane, diethyl ether, dimethoxyethane, tetrahydrofuran (also referred to as THF), 1,4-dioxane, and methyl cellosolve. , linear and cyclic ether solvents such as ethylcellosolve, aprotic polar solvents such as acetonitrile, dimethylsulfoxide, sulfolane, hexamethylphosphoric triamide, n-butylamine, isopropanolamine, diethylamine, triethanolamine, ethylenediamine, triethanolamine, etc. Examples include nitrogen-containing compounds such as ethylenediamine and triethylamine, mineral oils such as ligroin, and water, and those that do not dissolve the above-mentioned undercoat layer are preferably used. Note that these may be used alone or in combination of two or more in any ratio.

The coating liquid for forming a charge transport layer of a single-layer type photoreceptor and a laminated type photoreceptor has a solid content concentration of 5 [wt%] or more, preferably 10 [wt%] or more, and 40 [wt%] It is preferably 35 [wt%] or less. Further, the viscosity of the coating liquid is 10 [mPa·s] or more, preferably 50 [mPa·s] or more, and 500 [mPa·s] or less, preferably 400 [mPa·s] or less.

In the case of the charge generation layer of a laminated photoreceptor, the solid content concentration is 0.1 [wt%] or more, preferably 1 [wt%] or more, and 15 [wt%] or less, preferably 10 [wt%] or more. [% by weight] or less. Further, the viscosity of the coating liquid is 0.01 m [Pa・s] or more, preferably 0.1 [mPa・s] or more, and 20 [mPa・s] or less, preferably 10 [mPa・s] or less. be.

Examples of methods for applying the coating liquid include dip coating method, spray coating method, spinner coating method, bead coating method, wire bar coating method, blade coating method, roller coating method, air knife coating method, curtain coating method, etc. However, it is also possible to use other known coating methods. Note that these methods may be used alone or in any combination of two or more. The coating solution is dried to the touch at room temperature (25 [℃]), then heated and dried in a temperature range of 30 [℃] to 200 [℃] for a period of 1 minute to 2 hours with no wind or blowing air. It is preferable to let Further, the heating temperature may be constant or may be changed during drying.

The thickness of the photosensitive layer of the single-layer type photoreceptor is generally 5 [μm] or more, preferably 10 [μm] or more, and generally 100 [μm] or less, preferably 50 [μm] or less. Further, the thickness of the charge transport layer of the sequentially laminated photoreceptor is generally 5 [μm] or more and 50 [μm] or less, but from the viewpoint of long life and image stability, it is 10 [μm] or more, It is preferably 45 [μm] or less, and from the viewpoint of high resolution, it is preferably 10 [μm] or more and 30 [μm] or less.

<Support structure of photoreceptor drum and developing roller>
FIG. 8 is a schematic diagram showing a support structure for the photosensitive drum 11 and the developing roller 13. As shown in FIG. The housing 17 (FIG. 2) of the developing device 10 has side frames 22 and 23 on both sides of the photosensitive drum 11 and the developing roller 13 in the X direction. The photosensitive drum 11 and the developing roller 13 are supported by side frames 22 and 23. Note that the supply roller 14, the developing blade 15 (FIG. 2), and the like are also supported by the side frames 22 and 23, but are omitted in FIG. 8.

A drive member 80 is attached to the end of the photosensitive drum 11 in the +X direction (side frame 22 side), and a flange member 70 is attached to the end in the -X direction (side frame 23 side). An X-direction shaft 110 is attached to the flange member 70 and the drive member 80, and extends through the photoreceptor drum 11 in the axial direction.

Both ends 11e of the shaft 110 fit into holes 22a and 23a formed in the side frames 22 and 23. Flange member 70 and drive member 80 are rotatably engaged with shaft 110. The drive member 80 has a gear portion 81 (FIG. 9(A)), and receives rotation transmission from the drive motor 47 (FIG. 3).

In the developing roller 13, shaft end portions 13e at both ends in the X direction of a core metal 13a (FIG. 4) are supported by bearings disposed in holes 22b, 23b of the side frames 22, 23. Thereby, the developing roller 13 is rotatably supported by the side frames 22 and 23.

A roller gear 13g that meshes with a gear portion 81 (FIG. 9(A)) of a driving member 80 is fixed to a shaft end portion 13e of the developing roller 13 in the +X direction. When the photosensitive drum 11 rotates, the developing roller 13 also rotates due to the engagement between the driving member 80 and the roller gear 13g.

The surface of the photosensitive drum 11 and the surface of the developing roller 13 are in contact with each other. The distance L1 between the centers of the photosensitive drum 11 and the developing roller 13 is determined by the distance between the centers of the holes 22a, 22b (23a, 23b) of the side frame 22 (23). This center-to-center distance L1 determines the contact pressure between the photosensitive drum 11 and the developing roller 13 and the feed force described below.

<Drive member>
FIG. 9(A) is a cross-sectional view showing the photosensitive drum 11, the flange member 70, and the drive member 80. As described above, the driving member 80 is attached to the end of the blank tube 111 of the photosensitive drum 11 in the +X direction, and the flange member 70 is attached to the end of the blank tube 111 in the −X direction. As the raw pipe 111, for example, an aluminum cylindrical pipe having an inner diameter of 22.51 [mm], a length of 246 [mm], and a thickness of 0.71 [mm] is used.

The flange member 70 has an annular portion 71 and a cylindrical portion 72. The annular portion 71 and the cylindrical portion 72 are coaxial, and their centers coincide with the rotation axis Ax. The cylindrical portion 72 fits inside the blank tube 111 of the photoreceptor drum 11 . The annular portion 71 has an outer diameter larger than that of the raw pipe 111 and comes into contact with the end surface of the raw pipe 111 in the X direction.

A shaft hole 73 is formed in the radial center of the flange member 70, through which the shaft 110 (FIG. 8) is inserted. The shaft hole 73 passes through the annular portion 71 and the cylindrical portion 72 in the X direction. The flange member 70 is integrally formed of resin. The resin forming the flange member 70 is preferably a heat-resistant resin, such as ABS (acrylonitrile butadiene styrene) resin.

The drive member 80 has an annular gear portion 81 and a cylindrical fitting portion 82 . The gear portion 81 and the fitting portion 82 are coaxial, and their respective centers coincide with the rotation axis Ax. The fitting portion 82 fits inside the blank tube 111 of the photoreceptor drum 11 . The gear portion 81 has an outer diameter (that is, a tip circle diameter) larger than the base tube 111, and comes into contact with the end surface of the base tube 111 in the X direction.

The gear portion 81 of the drive member 80 meshes with a drive gear (not shown) connected to the drive motor 47 (FIG. 3), and receives a drive force for rotating the photoreceptor drum 11. A shaft hole 83 is formed in the radial center of the gear portion 81, into which the shaft 110 (FIG. 8) is inserted. The drive member 80 is integrally formed of resin. The resin forming the drive member 80 is desirably a heat-resistant resin, such as ABS resin.

FIG. 9(B) is an enlarged view of a part of the drive member 80. As shown in FIG. FIG. 10 is a perspective view showing the drive member 80. As shown in FIGS. 9(B) and 10, the outer circumferential surface 84 of the fitting portion 82 is a cylindrical surface centered on the rotation axis Ax. The outer circumferential surface 84 of the fitting portion 82 abuts on the inner circumferential surface of the raw tube 111 (FIG. 9(A)) of the photoreceptor drum 11.

Furthermore, a recess 85 is formed in the outer circumferential surface 84 of the fitting portion 82 in the circumferential direction around the rotation axis Ax. The recess 85 is a space that accommodates an adhesive for bonding the driving member 80 to the photoreceptor drum 11. In other words, the recess 85 is an adhesive reservoir. That is, the adhesive adheres to the recess 85.

The recess 85 has a width W in the X direction and a depth D in the radial direction. The width W of the recess 85 is preferably 1.5 to 2.0 [mm], as described later. The depth D of the recess 85 is desirably less than 1.0 [mm].

Further, the recessed portion 85 is formed at a position separated from the gear portion 81 by a distance L in the X direction. The distance L is desirably 3.0 [mm] or more. The recess 85 is formed so as to go around the fitting part 82 in the circumferential direction.

The recess 85 is, for example, a U-shaped groove having a rectangular cross-sectional shape. However, the recess 85 may be a groove of other shape (for example, a V-shaped groove, a U-shaped groove, etc.), or the gear part 81 side (+X side) is higher and the opposite side (-X side) is higher. It may be a low stepped portion.

A convex portion 86 is formed on the −X side of the fitting portion 82 (ie, on the inside in the axial direction of the photoreceptor drum 11) with respect to the concave portion 85. As shown in FIG. 10, a plurality of convex portions 86 are formed at equal intervals in the circumferential direction. A depression 87 is formed between adjacent protrusions 86 .

The top surface (the outermost surface in the radial direction) of the convex portion 86 is located on the same cylindrical surface as the outer circumferential surface 84 . The outer circumferential surface 84 of the fitting portion 82 and the top surface of the convex portion 86 abut against the inner circumferential surface of the blank tube 111 of the photoreceptor drum 11 .

The bottom surface of the depression 87 between the protrusions 86 is located on the same cylindrical surface as the bottom surface of the recess 85 . The recess 87 is provided to facilitate air escape from between the fitting portion 82 and the blank tube 111 when the driving member 80 is attached to the photosensitive drum 11 . Note that the convex portion 86 may be formed in an annular shape so as to go around the fitting portion 82 in the circumferential direction without providing the recess 87.

Further on the −X side of the convex portion 86, an inclined surface 88 is formed. The inclined surface 88 is inclined so that it approaches the rotation axis Ax as it advances in the −X direction. The inclined surface 88 is provided to facilitate fitting the fitting portion 82 inside the blank tube 111 when the driving member 80 is attached to the photoreceptor drum 11 .

A cavity 89 is provided on the inner peripheral side of the fitting portion 82 and communicates with the shaft hole 83 (FIG. 9(A)) of the gear portion 81. The hollow portion 89 is provided in order to reduce the amount of material used to form the fitting portion 82 and reduce the weight. Note that the cavity 89 does not necessarily need to be provided.

The gear portion 81 has a plurality of teeth 81a in the circumferential direction. Note that although the gear portion 81 shown in FIG. 10 is a helical gear, it is not limited to this.

The driving member 80 is bonded to the inside of the raw tube 111 of the photoreceptor drum 11 with an adhesive. As the adhesive, for example, a cyanoacrylate adhesive is desirable. A cyanoacrylate adhesive is an adhesive whose main component is a 2-cyanoacrylate monomer. Examples include Aron Alpha (registered trademark) manufactured by Toagosei Co., Ltd. and Loctite (registered trademark) manufactured by Henkel Japan Co., Ltd. Furthermore, an epoxy adhesive may be used instead of the cyanoacrylate adhesive.

When attaching the driving member 80 to the blank tube 111 of the photosensitive drum 11, first, the above adhesive (for example, 140 [mg]) is applied to the inner peripheral surface of the +X direction end of the blank tube 111. In this state, the fitting part 82 of the drive member 80 is inserted inside the blank pipe 111. Thereby, the inner circumferential surface of the blank pipe 111 and the fitting portion 82 are joined with the adhesive.

That is, some of the adhesive initially applied to the inner peripheral surface of the raw pipe 111 exists between the inner peripheral surface of the raw pipe 111 and the outer peripheral surface 84 and the top surface of the convex portion 86. do. The remaining adhesive is accommodated in the recess 85.

<Basic operations of image forming apparatus>
Next, the printing operation of the image forming apparatus 1 will be explained with reference to FIGS. 1 and 3. When the print control unit 30 receives a print command and print data from the host device via the I/F control unit 31, it starts a printing operation.

The print control unit 30 temporarily records the print data received from the host device in the reception memory 32 , edits the recorded print data to generate image data, and records it in the image data editing memory 33 .

Further, the fixing drive control section 43 drives the fixing motor 63, and the fixing roller 61 and pressure roller 62 start rotating. Further, the fixing control unit 42 energizes the heater in the fixing roller 61, and the fixing roller 61 is heated to a predetermined fixing temperature.

Further, the conveyance control unit 44 drives the conveyance motor 46, and the paper feed roller 52 sends out the medium P in the medium tray 51 to the conveyance path as shown by arrow a1. Further, the conveyance roller 53 rotates and conveys the medium P to the developing device 10 as shown by arrow a2.

Furthermore, a charging voltage, a developing voltage, a supply voltage, and a blade voltage are applied to the charging roller 12, developing roller 13, supply roller 14, and developing blade 15 from each power source 36 to 39, respectively.

Further, the drive control unit 45 drives the drive motor 47, and the photosensitive drum 11 rotates. As the photosensitive drum 11 rotates, the charging roller 12, developing roller 13, and supply roller 14 also rotate. The charging roller 12 uniformly charges the surface of the photoreceptor drum 11.

Further, the head control unit 41 drives the LED head 21 to irradiate the surface of the photoreceptor drum 11 with light. As a result, an electrostatic latent image is formed on the surface of the photoreceptor drum 11.

The electrostatic latent image formed on the surface of the photoreceptor drum 11 is developed with toner adhering to the developing roller 13, and a toner image is formed on the surface of the photoreceptor drum 11. Furthermore, a transfer voltage is applied to the transfer roller 20 from the transfer roller power source 40.

This transfer voltage causes the toner image on the surface of the photoreceptor drum 11 to be transferred to the medium P passing between the photoreceptor drum 11 and the transfer roller 20 . The toner that has not been transferred to the medium P is scraped off by the cleaning member 16.

In the fixing device 60, heat and pressure are applied to the medium P passing through the fixing nip between the fixing roller 61 and the pressure roller 62, and the toner image is fixed on the medium P. The medium P on which the toner image is fixed is sent to the medium discharge section 65 as shown by arrow a3.

In the medium discharge section 65, a discharge roller 66 discharges the medium P from the discharge port as shown by arrow a4. The ejected medium P is stacked on the stacker 68. This completes the formation of the image on the medium P.

<Operation of developing device>
The operation of the developing device 10 in the above printing operation is as follows. The photosensitive drum 11, charging roller 12, developing roller 13, and supply roller 14 of the developing device 10 rotate in the directions indicated by arrows in FIG. 2, respectively.

In the image forming apparatus 1, an A4 size medium P is conveyed vertically, and the printing speed is 40 [ppm] (page per minute). The outer diameter of the developing roller 13 is 16.0 [mm] and the peripheral speed is 0.3 [m/s], and the outer diameter of the supply roller 14 is 15.5 [mm] and the peripheral speed is 0. .2 [m/s]. The outer diameter of the photosensitive drum 11 is 30.0 [mm], and the peripheral speed is 0.22 [m/s].

The supply roller 14 rotates while carrying toner on the outer peripheral surface of the foamed elastic layer 14b and in the cells. A DC voltage of -330 [V] is applied to the supply roller 14 from a supply roller power supply 38, and a DC voltage of -200 [V] is applied to the development roller 13 from a development roller power supply 37. Due to the potential difference between the developing roller 13 and the supply roller 14, the negatively charged toner is supplied to the developing roller 13.

A DC voltage of -330 [V] is applied to the developing blade 15 from the developing blade power source 39. The developing blade 15 causes the toner on the surface of the developing roller 13 to become a thin layer.

A DC voltage of -1000 [V] is applied to the charging roller 12 from the charging roller power supply 36. By this charging roller 12, the surface of the photosensitive drum 11 is uniformly charged to about -450 [V].

The uniformly charged surface of the photosensitive drum 11 is exposed to light by the LED head 21 to form an electrostatic latent image. The electrostatic latent image formed on the surface of the photosensitive drum 11 is developed with toner carried by the developing roller 13, and becomes a toner image.

When printing a solid image with a printing image density of 100%, the surface potential of the photoreceptor drum 11 changes from -450 [V] before exposure to -50 [V] by exposure of all LEDs of the LED head 21. ] attenuates to a degree.

The toner on the developing roller 13 that has not been supplied to the photoreceptor drum 11 is scraped off by the supply roller 14 at a portion facing the supply roller 14 .

The toner image on the surface of the photosensitive drum 11 is transferred onto the medium P by a transfer roller 20 (FIG. 1) to which a predetermined transfer voltage is applied.

On the other hand, the toner remaining on the surface of the photoreceptor drum 11 without being transferred to the medium P and the external additive released from the toner base particles and attached to the surface of the photoreceptor drum 11 are scraped off by the cleaning member 16.

After toner and external additives are scraped off the surface of the photoreceptor drum 11 by the cleaning member 16, the surface of the photoreceptor drum 11 is irradiated with a static eliminating light by a static eliminating light unit (not shown) to eliminate static electricity. The surface of the photoreceptor drum 11 from which electricity has been removed is charged again by the charging roller 12 .

<Operation of Embodiment 1>
Next, the operation of the first embodiment will be explained. FIG. 11A is a diagram showing a joint portion between the photosensitive drum 11 and the driving member 80 of the first embodiment. FIG. 11B is a diagram showing a joint portion between the photosensitive drum 11 and the driving member 180 in a comparative example.

The drive member 180 of the comparative example shown in FIG. 11(B) has a recess 85 at a position adjacent to the gear part 81 in the fitting part 82. That is, the distance between the recessed portion 85 and the gear portion 81 in the X direction is 0 [mm]. The drive member 180 of the comparative example is formed similarly to the drive member 80 of the first embodiment shown in FIG. 11(A) except for the position of the recess 85.

Generally, if the bonding between the photoreceptor drum 11 and the drive member 80 is insufficient, there is a possibility that the photoreceptor drum 11 and the drive member 80 will be misaligned in the X direction during continuous printing. Such positional deviation is referred to as gear deviation.

When gear misalignment occurs, the position of the outer circumferential surface of the photoreceptor drum 11 changes in the radial direction, and as a result, the pressure between the photoreceptor drum 11 and the transfer roller 20 decreases locally during the transfer of the toner image. , printing defects such as white spots may occur.

For example, when the drive member 80 is made of ABS resin, the coefficient of thermal expansion is 5.87×10 ⁻⁵ /K, and when the base tube 111 of the photoreceptor drum 11 is made of aluminum, the thermal expansion coefficient is 5.87×10 −5 /K. The rate is 2.30×10 ⁻⁵ /K. Therefore, when the image forming apparatus 1 is used in a low temperature environment of, for example, 10° C. or lower, the drive member 80 exhibits a larger deformation than the raw tube 111 of the photoreceptor drum 11, and as a result, the above-mentioned gear misalignment is likely to occur. .

The reason why the bonding between the photosensitive drum 11 and the driving member 80 is insufficient is that when the driving member 80 is bonded to the photosensitive drum 11, the adhesive leaks from between the raw tube 111 and the fitting part 82 in the -X direction. (that is, the inside of the raw pipe 111).

In order to hold the adhesive between the blank pipe 111 and the fitting part 82, it is effective to provide the fitting part 82 with a recess 85 for holding the adhesive.

However, if the recess 85 is adjacent to the gear part 81 as in the comparative example shown in FIG. There is a possibility that it may adhere to the tooth 81a of No. 81. If the adhesive A adheres to the teeth 81a of the gear portion 81, the meshing with the drive gear during rotation will be insufficient, and the runout of the outer peripheral surface of the photoreceptor drum 11 (i.e., radial positional fluctuation) will increase, resulting in printing defects. This will cause this to occur.

In contrast, in the first embodiment, as shown in FIG. 11(A), the recessed portion 85 is spaced apart from the gear portion 81 in the X direction. Therefore, even if the adhesive A leaks from the recess 85, it is prevented from adhering to the teeth 81a of the gear portion 81. As a result, a sufficient amount of adhesive for joining the blank tube 111 and the fitting portion 82 can be held in the recess 85, and printing defects due to adhesion of the adhesive to the gear portion 81 can be prevented. be able to.

<Relationship between feed force and gear misalignment>
Next, the relationship between the feed force exerted by the photoreceptor drum 11 and the developing roller 13 and gear misalignment will be explained. Since the photosensitive drum 11 and the developing roller 13 rotate while in contact with each other, a force called a feed force (conveying force) acts on the contact portion. The feed force is a frictional force due to the difference in peripheral speed between the photoreceptor drum 11 and the developing roller 13, and is also referred to as a pull-out force.

First, a method for measuring feed force will be explained. FIG. 12(A) is a schematic diagram showing a method of measuring the feed force by the photoreceptor drum 11 and the developing roller 13. FIG. 12(B) is a schematic diagram showing a measuring jig 90 used for measuring the feed force.

As shown in FIG. 12A, a film 92 is inserted between the photoreceptor drum 11 and the developing roller 13, the photoreceptor drum 11 and the developing roller 13 are rotated, and the force with which the film 92 is pulled is measured by a force gauge 91. Measure the feed force by measuring at .

The longitudinal direction of the film 92 is the tangential direction of the surface of the photoreceptor drum 11 at the contact portion (indicated by the symbol N) between the photoreceptor drum 11 and the developing roller 13 . The width direction of the film 92 is the X direction.

As shown in FIG. 12(B), a support plate 93 is fixed to the upper end of the film 92 (the end on the side away from the contact portion N). One end of a hook 95 is attached to the support plate 93, and the other end of the hook 95 is attached to the force gauge 91.

The film 92 is made of, for example, PET (polyethylene terephthalate). The length of the film 92 is 95 [mm], the width is 5 [mm], and the thickness is 1 [mm]. The width direction of the film 92 is the X direction.

The support plate 93 is, for example, an acrylic plate, and is fixed to one end of the film 92 in the longitudinal direction. The length of the support plate 93 is 20 [mm], and the width is 12 [mm]. The support plate 93 is formed with a hole 94 into which one end of a hook 95 is hooked.

As shown in FIG. 12A, with the film 92 inserted between the photoreceptor drum 11 and the developing roller 13, the photoreceptor drum 11 and the developing roller 13 are rotated, respectively. The rotational speed (peripheral speed) of the photosensitive drum 11 is 234.0 [mm/sec], which corresponds to a printing speed of 49 [ppm]. Further, the circumferential speed of the developing roller 13 is 1.26 times the circumferential speed of the photoreceptor drum 11.

Note that the circumferential speed ratio (here, 1.26) between the photoreceptor drum 11 and the developing roller 13 is determined by the outer diameter ratio of the photoreceptor drum 11 and the developing roller 13, and the ratio between the gear portion 81 of the driving member 80 and the roller gear 13g. Determined by the tooth number ratio.

With the photosensitive drum 11 and the developing roller 13 rotated as described above, the value [N] of the force gauge 91 is read. The force gauge 91 is a digital force gauge here, and the measured value is output to the personal computer.

The feed force is measured at a total of three locations: the center of the developing roller 13 in the X direction and on both sides of the center in the X direction. At each location, the output value of the force gauge 91 is recorded with a sampling interval of 10 [m seconds], and the average value for 5 [seconds] is calculated. As a result, the feed force [N] at each location is obtained. The maximum value of the feed force at the three locations is defined as the feed force [N].

Here, the driving member 80 was bonded to the photosensitive drum 11 without using an adhesive. Further, the photoreceptor drum 11 and the developing roller 13 are attached to the side frames 22 and 23 (FIG. 8) of the housing 17 (FIG. 2), and the distance L1 between the centers of the photoreceptor drum 11 and the developing roller 13 (FIG. 8) The feed force was measured by changing the force in 10 ways. The test environment was a low-temperature, low-humidity environment (temperature of 10 [° C.], relative humidity of 20 [%]) in which the drive member 80 is likely to undergo thermal contraction and gear misalignment.

After measuring the feed force in this manner, the developing device 10 including the photosensitive drum 11 and the developing roller 13 described above was incorporated into the image forming apparatus 1 (FIG. 1), and a continuous printing test of several hundred sheets was conducted. In the continuous printing test, A4 size plain paper was used as the medium P, and a test pattern with a print image density (duty ratio) of 0.3% was printed on several hundred sheets of the medium P.

In the continuous printing test, the printing speed was 40 [ppm], and the peripheral speeds of the photosensitive drum 11, the developing roller 13, and the supply roller 14 were set as described above regarding the operation of the developing device 10. Furthermore, the voltages applied to the developing roller 13, supply roller 14, developing blade 15, and transfer roller 20 were also set as described above regarding the operation of the developing device 10.

After the continuous printing test, the developing device 10 was removed from the image forming apparatus 1, the photosensitive drum 11 was removed from the developing device 10, and the presence or absence of gear misalignment was visually determined.

Table 1 below shows the relationship between the feed force measured by the method shown in FIGS. 9(A) and 9(B) and the presence or absence of gear misalignment after the continuous printing test.

From the results in Table 1, if the feed force is 1.6 [N] or less, gear misalignment can be prevented even if the drive member 80 is bonded to the photoreceptor drum 11 without using adhesive. I understand that. Therefore, even if the drive member 80 is bonded to the photoreceptor drum 11 using an adhesive as described below, gear misalignment will not occur as long as the feed force is at least 1.6 [N] or less. It can be said that.

<Relationship between the width of the recess and the removal force>
Next, the relationship between the width W of the recess 85 of the drive member 80 and the force for removing the drive member 80 from the photoreceptor drum 11 was investigated.

FIG. 13 is a diagram showing a method for measuring extraction force. First, the fitting portion 82 of the drive member 80 is bonded to the inside of the blank tube 111 of the photosensitive drum 11 using an adhesive. The flange member 70 is not attached to the other end of the photoreceptor drum 11, so that it is an open end.

Further, the lower end portion of the shaft 101 facing in the vertical direction is fixed to a fixing base 103 placed on the weighing scale 102 . A stepped portion is formed at the upper end of the shaft 101. Furthermore, the photosensitive drum 11 is attached so as to cover the shaft 101 with its open end facing down, and the upper end of the shaft 101 is fitted into the shaft hole 83 of the drive member 80 .

In this state, the operator grasps the outer periphery of the photoreceptor drum 11 with both hands and urges the photoreceptor drum 11 downward as shown by arrow F in the figure. Since the stepped portion is formed at the upper end of the shaft 101, the driving member 80 does not move relative to the shaft 101. Therefore, the force F applied by the operator to the photoreceptor drum 11 becomes a force that causes the photoreceptor drum 11 to pull out downward from the drive member 80 (that is, a removal force).

When the force F applied by the operator to the photoreceptor drum 11 exceeds the adhesive force between the photoreceptor drum 11 and the fitting part 82 of the driving member 80, the photoreceptor drum 11 comes off from the fitting part 82 and moves downward. do. At this time, the removal force [kgf] is read from the display on the display section 104 of the weight scale 102.

Here, the width W of the recessed portion 85 of the driving member 80 is set in five ways: 0 [mm], 1.0 [mm], 1.5 [mm], 2.0 [mm], and 2.5 [mm]. The removal force [kgf] was measured for each.

After measuring this removal force, the surface of the fitting part 82 of the drive member 80 is visually observed to see if the adhesive is present over the entire circumference of the recess 85, in other words, there is no adhesive missing in the recess 85. I checked to see if there were any parts.

When no defective part of the adhesive was observed over the entire circumference of the recess 85, the judgment result was evaluated as good (◯). In addition, even if a slight adhesive loss portion was observed, if it was at a level that did not affect gear misalignment, the judgment result was given as acceptable (△). In addition, when a defective part of the adhesive was clearly observed, the judgment result was determined to be poor (x).

<Continuous printing test>
Further, the driving member 80 in which the width W of the recessed portion 85 was changed as described above was incorporated into the image forming apparatus 1 (FIG. 1), and a continuous printing test (long-term continuous test) was conducted. A4 size plain paper was used as the medium P, and a test pattern with a print image density (duty ratio) of 0.3% was printed on 30,000 sheets (30K sheets).

In the continuous printing test, the printing speed was 40 [ppm], and the peripheral speeds of the photosensitive drum 11, the developing roller 13, and the supply roller 14 were set as described above regarding the operation of the developing device 10. Furthermore, the voltages applied to the developing roller 13, supply roller 14, developing blade 15, and transfer roller 20 were also set as described above regarding the operation of the developing device 10.

In the continuous printing test, during the printing of 30,000 sheets, the photosensitive drum 11 was removed from the image forming apparatus 1 every few hundred sheets, and the presence or absence of gear misalignment was determined.

If no gear shift was observed after 30,000 sheets of continuous printing was completed, the determination result was evaluated as good (◯). In addition, if gear misalignment is not observed after continuous printing of several hundred sheets has been completed, but if gear misalignment is observed after continuous printing of 30,000 sheets has been completed, the judgment result is accepted (△). did. Further, if gear shift was observed after continuous printing of several hundred sheets was completed, the determination result was determined to be poor (x).

In addition to determining the presence or absence of gear misalignment, the gear portion 81 of the drive member 80 was visually observed, and the presence or absence of adhesive adhesion to the gear portion 81 was observed. If adhesive adhesion to the gear part 81 is not observed, the judgment result is marked as good (○), and if adhesive adhesion to the gear part 81 is observed, the judgment result is marked as poor (x). ).

When the width W [mm] of the recessed portion 85 is changed in five ways, the measured value of the removal force [kgf], the presence or absence of gear shift, the presence or absence of adhesive adhesion to the gear portion 81, and the recessed portion The judgment results regarding the entire circumference application of the adhesive in No. 85 are shown in Table 2 below.

As shown in Table 2, when the width W of the recess 85 was 0, the removal force was small and gear misalignment was observed after several hundred sheets were continuously printed. This is because the recess 85 is not formed in the fitting part 82 of the drive member 80, so the amount of adhesive retained between the raw pipe 111 and the fitting part 82 is small, and the adhesive between the raw pipe 111 and the fitting part 82 is This is due to insufficient bonding.

Further, when the width W of the recess 85 was 1.0 [mm], the removal force was large, but gear misalignment was observed after 30,000 sheets were continuously printed. This is because, although the removal force was improved by providing the recess 85 in the fitting portion 82 of the drive member 80, a strong joint was not obtained as in the case where the width W of the recess 85 was further widened. It is.

When the width W of the recess 85 was 2.5 mm, the removal force was even greater, and no gear shift was observed even after 30,000 sheets were continuously printed. However, the adhesive was not applied to the entire circumference of the recess 85, and a portion of adhesive missing that did not affect gear misalignment was observed. This is because the width W of the recess 85 is wide, so that there are some areas where the adhesive does not spread. Incidentally, if the amount of adhesive is increased, it can be distributed all around the recess 85, but this will lead to an increase in cost, and the increased volume of the adhesive after solidification may cause cracks due to thermal contraction or thermal expansion. Therefore, it is desirable not to increase the amount of adhesive too much.

On the other hand, when the width W of the recess 85 was 1.5 to 2.0 [mm], the removal force was sufficiently large, and no gear shift was observed even after 30,000 sheets were continuously printed. Further, no loss of the adhesive was observed over the entire circumference of the recess 85. This is because the recess 85 has a sufficient width W, so a sufficient amount of adhesive is retained for joining the raw tube 111 and the fitting part 82, and the width W of the recess 85 is not too wide, so the adhesive This is because the amount of water is distributed all around the recessed portion 85.

From the above results, in order to firmly attach the driving member 80 to the blank tube 111 of the photoreceptor drum 11 and to apply the adhesive evenly around the entire circumference of the recess 85, the width W of the recess 85 should be 1.5 to 1.5. The most desirable value is 2.0 [mm].

<Effects of the embodiment>
As described above, the developing device 10 of this embodiment includes the photosensitive drum 11 that carries an electrostatic latent image, the developing roller 13 that develops the electrostatic latent image, and the photosensitive drum 11 that is bonded to the photosensitive drum 11 with an adhesive. A drive member 80 is provided. The drive member 80 includes a fitting portion 82 that fits into the photoreceptor drum 11 and a gear portion 81 . The fitting portion 82 has a recess 85 extending in the circumferential direction, and an adhesive adheres to the recess 85 . The recessed portion 85 is provided at a position away from the gear portion 81. Therefore, occurrence of gear misalignment can be suppressed, and printing defects due to adhesion of adhesive to the gear portion 81 can be suppressed.

Moreover, since the fitting part 82 has the protrusion 86 on the opposite side of the gear part 81 with respect to the recess 85, the protrusion 86 can prevent the adhesive from flowing into the inside of the raw pipe 111.

Further, the fitting part 82 has an outer circumferential surface 84 which is a cylindrical surface on the gear part 81 side with respect to the recess 85, and this outer circumferential surface 84 and the convex part 86 abut against the inner circumferential surface of the raw pipe 111. , it is possible to secure a wide contact surface between the fitting part 82 and the raw tube 111 of the photoreceptor drum 11, and to increase the bonding strength between the raw tube 111 and the fitting part 82.

In addition, since the width W of the recess 85 is 1.5 [mm] or more and 2.0 [mm] or less, sufficient removal force can be obtained, and the adhesive can be applied evenly over the entire circumference of the recess 85. can be granted to

Furthermore, since the distance L in the X direction from the recess 85 to the gear part 81 is 3.0 [mm] or more, even if the adhesive leaks from the recess 85, the adhesive can be effectively prevented from leaking to the gear part 81. can do.

Further, since the recess 85 is provided so as to go around the fitting part 82 once in the circumferential direction, the adhesive can be held in the recess 85 over the entire circumference of the fitting part 82, and the adhesive can be held in the recess 85 over the entire circumference of the fitting part 82. The bonding strength with the fitting portion 82 can be increased.

Further, since the fitting part 82 has an inclined surface 88 on the outer periphery on the opposite side to the gear part 81, when the driving member 80 is attached to the photoreceptor drum 11, the fitting part 82 is fitted to the blank tube 111. It becomes easier to do so.

Further, since the fitting portion 82 and the gear portion 81 are integrally formed of resin, the driving member 80 having sufficient strength can be realized at low cost.

In addition, in a low-temperature, low-humidity environment with a temperature of 10 [°C] and a relative humidity of 20 [%], the feed force generated by the photoreceptor drum 11 and the developing roller 13 is 1.6 [N] or less, so the larger the feed force, the more It is possible to more effectively prevent gear misalignment, which tends to occur easily.

Note that in this embodiment, various evaluations were performed at a temperature of 10 [° C.] and a relative humidity of 20 [%], but the temperature and humidity are not limited to these examples. In addition, although the amount of adhesive for joining the driving member 80 to the raw pipe 111 was set to 140 [mg], if the driving member 80 can be joined to the raw pipe 111, the amount of adhesive is limited to this example. Not done.

Although the preferred embodiments have been specifically described above, the present disclosure is not limited to the embodiments described above, and various improvements and modifications can be made.

The present disclosure can be used in image forming apparatuses that form images on media, such as printers, copying machines, facsimile machines, and MFPs (Multi Function Peripherals).

Hereinafter, various aspects of the present disclosure will be collectively described as supplementary notes.
(Additional note 1)
an image carrier that carries an electrostatic latent image and is rotatable around a rotation axis;
a developer carrier that develops the electrostatic latent image;
a driving member bonded to an end of the image carrier with an adhesive;
The driving member has a fitting part that fits into the image carrier, and a gear part,
The fitting portion has a recess extending in a circumferential direction centered on the rotation axis, and the adhesive adheres to the recess,
The developing device is characterized in that the recessed portion is provided at a position apart from the gear portion.
(Additional note 2)
The developing device according to appendix 1, wherein the fitting portion has a convex portion on a side opposite to the gear portion with respect to the recess.
(Additional note 3)
The fitting portion has an outer circumferential surface that is a cylindrical surface on the gear portion side with respect to the recessed portion,
The developing device according to appendix 2, wherein the outer circumferential surface and the convex portion are in contact with an inner circumferential surface of the image carrier.
(Additional note 4)
The developing device according to any one of Supplementary Notes 1 to 3, wherein the width of the recess in the direction of the rotating shaft is 1.5 [mm] or more and 2.0 [mm] or less.
(Appendix 5)
The developing device according to any one of Supplementary Notes 1 to 4, wherein a distance from the recessed portion to the gear portion in the direction of the rotation axis is 3.0 [mm] or more.
(Appendix 6)
The developing device according to any one of Supplementary Notes 1 to 5, wherein the recess extends around the fitting portion once in the circumferential direction.
(Appendix 7)
The developing device according to any one of Supplementary Notes 1 to 6, wherein the fitting portion has an inclined surface on an outer periphery opposite to the gear portion.
(Appendix 8)
The developing device according to any one of appendices 1 to 7, wherein the fitting portion and the gear portion are integrally formed of resin.
(Appendix 9)
Any one of Supplementary Notes 1 to 8, characterized in that, in an environment with a temperature of 10° C. and a relative humidity of 20%, the feed force by the image carrier and the developer carrier is 1.6 [N] or less. Developing device described in Section 1.
(Appendix 10)
The developing device according to any one of Supplementary Notes 1 to 9;
a transfer unit that transfers the developer image developed by the developing device to a medium;
An image forming apparatus comprising: a fixing device that fixes the developer image transferred to the medium to the medium.

1 Image forming apparatus, 10 Developing device (image bearing unit, image forming unit), 11 Photosensitive drum (image bearing body), 12 Charging roller (charging member), 13 Developing roller (developer bearing member), 14 Supply roller (supply member), 15 developing blade (layer regulating member), 16 cleaning member, 18 toner cartridge (developer container), 20 transfer roller (transfer member), 21 LED head (exposure device), 22, 23 side frame, 50 medium supply section, 60 fixing device, 65 medium discharge section, 70 flange member, 71 annular section, 72 cylindrical section, 73 shaft hole, 80 drive member, 81 gear section, 82 fitting section, 83 shaft hole, 84 outer peripheral surface , 85 recess, 86 protrusion, 87 depression, 88 slope, 89 cavity, 90 measurement jig, 110 shaft, 111 base tube (conductive support), 112 undercoat layer, 113 photosensitive layer, 114 charge generation layer , 115 charge transport layer.

Claims (10)

an image carrier that carries an electrostatic latent image and is rotatable around a rotation axis;
a developer carrier that develops the electrostatic latent image;
a driving member bonded to an end of the image carrier with an adhesive;
The driving member has a fitting part that fits into the image carrier, and a gear part,
The fitting portion has a recess extending in a circumferential direction centered on the rotation axis, and the adhesive adheres to the recess,
The developing device is characterized in that the recessed portion is provided at a position apart from the gear portion. The developing device according to claim 1, wherein the fitting portion has a convex portion on a side opposite to the gear portion with respect to the recess. The fitting portion has an outer circumferential surface that is a cylindrical surface on the gear portion side with respect to the recessed portion,
The developing device according to claim 2, wherein the outer circumferential surface and the convex portion are in contact with an inner circumferential surface of the image carrier. The developing device according to claim 1, wherein the width of the recess in the direction of the rotation axis is 1.5 [mm] or more and 2.0 [mm] or less. The developing device according to claim 1, wherein a distance from the recessed portion to the gear portion in the direction of the rotation axis is 3.0 [mm] or more. The developing device according to claim 1, wherein the recess extends around the fitting portion once in a circumferential direction. The developing device according to claim 1, wherein the fitting portion has an inclined surface on an outer periphery opposite to the gear portion. The developing device according to claim 1, wherein the fitting portion and the gear portion are integrally formed of resin. The developing device according to claim 1, wherein in an environment with a temperature of 10° C. and a relative humidity of 20%, a feed force between the image carrier and the developer carrier is 1.6 [N] or less. A developing device according to any one of claims 1 to 9,
a transfer unit that transfers the developer image developed by the developing device to a medium;
An image forming apparatus comprising: a fixing device that fixes the developer image transferred to the medium to the medium.

Images