Developing device, image forming apparatus, supply roller, and method for manufacturing supply roller

Abstract

To reduce the occurrence of an image defect even when the quantity of airflow of a supply roller is increased.SOLUTION: When a developing device is mounted in an image forming apparatus, and in a posture where both ends in a longitudinal direction of a supply roller 43 is supported on a frame of the image forming apparatus, a developing opening 46c is installed above the rotation shaft of the supply roller 43, a stirring shaft 45a is installed above the developing opening 46c, and the absolute value of the quantity of airflow in a central part in the longitudinal direction is larger than the absolute value of the quantity of airflow at a position of one-tenth from an end in the supply roller 43.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a developing device, an image forming apparatus, a supply roller, and a method for manufacturing a supply roller, and more particularly to a developing device, a process cartridge, and an image forming apparatus used in, for example, an image forming apparatus such as a copying machine, a printer, or a facsimile machine that uses an electrophotographic system or an electrostatic recording system. [Background technology]

[0002] Conventionally, electrophotographic image forming apparatuses are equipped with a developing device that supplies a developer to an electrostatic latent image formed on an electrophotographic photosensitive member (image carrier) to form a developer image. This type of development method uses, for example, a single-component developer consisting only of toner. In this development method, the developing device is primarily composed of two spaces: a toner storage chamber that stores toner and a development chamber where the development process takes place. The toner is supplied to the development chamber through a development opening located at the boundary between the toner storage chamber and the development chamber by the rotation of an agitator in the toner storage chamber. The development chamber is composed of a developing roller, a supply roller, and a development blade. The developing roller is a developer carrier that transports toner to the photosensitive drum and develops the toner image on the photosensitive drum. The supply roller is a developer supplying member with a sponge structure that is arranged around the developing roller and supplies toner to the developing roller and removes it from the developing roller. The development blade is a regulating member arranged around the developing roller that regulates the toner layer formed by the toner supplied from the supply roller to the developing roller. The supply roller achieves the above-mentioned effect by contacting and penetrating a desired, specified amount of the supply roller with the surface of the developing roller using a fixed shaft method or the like. The toner transported to the developing chamber is supplied onto the developing roller by the supply roller and regulated by the developing blade. After passing through the contact area between the developing roller and the developing blade, the toner is transported to the developing area, which is the area adjacent to the photosensitive drum, where the electrostatic latent image is visualized as a toner image.

[0003] When toner is transported from the toner storage chamber to the developing chamber, if the development opening is located vertically below the agitator and the center of the supply roller is located even further below the development opening, the rotation of the agitator may repeatedly push the toner into the developing chamber. In this case, the toner may easily clog the developing chamber, potentially reducing toner movement. Meanwhile, the rotation of the agitator increases the powder pressure of the toner at the center compared to the edges. Therefore, from the perspective of toner circulation, this phenomenon is particularly evident in the image center, i.e., the center of the photosensitive drum in the axial direction. When toner movement in the developing chamber decreases, the supply roller is unable to properly supply and discharge toner. Specifically, because toner movement is reduced at the center compared to the longitudinal edges, the supply roller is unable to adequately retain toner in its sponge layer and is therefore unable to supply toner to the developing roller. This can result in image defects known as toner tracking failure, i.e., insufficient density due to a lack of toner supplied from the supply roller, occurring at the center of the image at certain rotational intervals of the supply roller or developing roller.

[0004] One solution to this problem is to increase the supply roller's airflow rate, improving toner circulation within the developing chamber and enhancing the function of the supply roller. Airflow rate is a parameter expressed in liters per minute (L / min) when a predetermined volume of air at a predetermined pressure is passed through the supply roller. The supply roller has a foamed sponge structure, as shown in Figure 9, and the cell diameter and interconnectivity are controlled by the polymer viscosity, carbon dioxide gas amount, and foaming conditions. Interconnectivity refers to the degree to which the cells are interconnected. Adjusting the cell diameter and interconnectivity allows for control of the supply roller's airflow rate. Furthermore, a manufacturing method has been disclosed in which the density of the elastic layer (sponge portion) is higher in the center of the supply roller than at both ends in the longitudinal direction of the supply roller to improve the supply roller's ability to scrape residual toner after development (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2014-170028 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, increasing the supply roller's ventilation rate can lead to image defects, such as horizontal bands appearing at intervals along the supply roller's circumference (hereinafter referred to as the "supply roller set") when forming images after a long period of inactivity. Increasing the ventilation rate strengthens the foaming of the sponge structure, i.e., suppresses the cross-linking structure, making the supply roller softer and more susceptible to deformation. As a result, fluctuations in peripheral speed due to permanent deformation occur at the contact point with the developing roller, particularly at the longitudinal ends, resulting in poor image quality. Furthermore, the following phenomenon also occurs at the ends. Figure 10 shows how both ends of the developing roller 1041 and the supply roller 1043 are supported and fixed to the frame 1001 of the image forming apparatus. Because both ends of the supply roller 1043 (indicated by the dashed line β) are fixed to the frame 1001, they cannot bend like the center portion and remain pressed against the developing roller. If this condition persists, components of the ion conductive agent will seep out of the supply roller, hindering the supply of toner from the supply roller to the developing roller. As a result, the image quality is poor and the original density cannot be obtained. In this case, too, this phenomenon occurs with the rotation cycle of the supply roller and the developing roller.

[0007] The present invention has been made under these circumstances, and an object thereof is to reduce the occurrence of image defects even when the ventilation amount of the supply roller is increased. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, the present invention has the following configuration.

[0009] (1) A developing device comprising: a developer carrier that carries developer and develops an electrostatic latent image with the developer to form a developer image; a supply roller that contacts the developer carrier and supplies developer to the developer carrier; a storage chamber that holds the developer; a developing chamber having the developer carrier and the supply roller; a developing opening that separates the developing chamber from the storage chamber; an agitator shaft provided in the storage chamber; and an agitator that rotates around the agitator shaft in the storage chamber and agitates the developer; the developing device is mounted on an image forming device, and in a position where both ends of the supply roller in the longitudinal direction are supported by the frame of the image forming device, the developing opening is located above the rotation axis of the supply roller, the agitator shaft is located above the developing opening, and the absolute value of the airflow volume at the center of the longitudinal direction of the supply roller is greater than the absolute value of the airflow volume at a position one-tenth of the way from the end.

[0010] (2) An image forming apparatus for forming an image on a recording material, comprising an image carrier for carrying an electrostatic latent image, and a developing device according to (1) for developing the electrostatic latent image.

[0011] (3) A supply roller that contacts a developer carrier and supplies developer to the developer carrier, characterized in that when the supply roller is mounted on an image forming device and both longitudinal ends are supported by the frame of the image forming device, the absolute value of the air permeability at the center in the longitudinal direction is greater than the absolute value of the air permeability at a position one-tenth of the way from the end. [Effects of the Invention]

[0012] According to the present invention, even when the ventilation amount of the supply roller is increased, the occurrence of image defects can be reduced. [Brief explanation of the drawings]

[0013] [Figure 1] Schematic cross-sectional view of an image forming apparatus according to an embodiment of the present invention. [Figure 2] Schematic cross-sectional view of a process cartridge according to an embodiment of the present invention. [Figure 3]Schematic cross-sectional view of a developing device according to an embodiment of the present invention. [Figure 4] 1 is a schematic cross-sectional view of a supply roller according to an embodiment of the present invention, and shows a method for measuring the amount of air permeation through the supply roller. [Figure 5] FIG. 10 is a diagram showing the relationship between the amount of airflow through the supply roller and the amount of toner contained in the black toner trailing the supply roller in the embodiment; and FIG. 11 is a diagram showing the relationship between the amount of airflow through the supply roller and the amount of deformation after being left in a harsh environment. [Figure 6] FIG. 1 shows a method 1 for changing the ventilation amount in the longitudinal direction in the embodiment. [Figure 7] FIG. 2 shows a method 2 (crushing process) for changing the ventilation amount in the longitudinal direction in the embodiment. [Figure 8] FIG. 10 is a diagram showing the relationship between the amount of ventilation and the ratio of the density at the trailing end to the density at the leading end (density ratio) in the embodiment; and FIG. 11 is a diagram showing the relationship between the amount of ventilation and the deformation amount of the supply roller. [Figure 9] FIG. 10 is a diagram showing a sponge structure of a supply roller in a conventional example. [Figure 10] 10A and 10B are diagrams showing the support structure at both ends of the supply roller; DETAILED DESCRIPTION OF THE INVENTION

[0014] A developing device, a process cartridge, and an image forming apparatus according to the present invention will be described in detail with reference to the drawings. Hereinafter, a detailed description of an embodiment of the present invention will be given by way of example with reference to the drawings. However, the dimensions, materials, shapes, and relative positions of the components described in the embodiments may be changed as appropriate depending on the configuration and various conditions of the apparatus to which the invention is applied. In other words, the scope of the present invention is not limited to the following embodiments. [Example]

[0015] (Overall configuration and operation of the image forming apparatus) FIG. 1 is a schematic cross-sectional view of an image forming apparatus according to an embodiment. The image forming apparatus 100 is a laser beam printer that forms images using an electrophotographic system. The image forming apparatus 100 employs a cartridge system, with a process cartridge 120 being detachably attached to an apparatus main body 110. An external host device such as a personal computer or image reading device is connected to the image forming apparatus 100. The image forming apparatus 100 receives image information from the host device, and forms and outputs (prints) an image on a recording material (recording medium, transfer material) according to the received image information. A sheet material such as paper is preferably used as the recording material.

[0016] The image forming apparatus 100 has a photosensitive drum 1, which is a drum-type (cylindrical) electrophotographic photosensitive member (photoconductor) serving as an image carrier. Around the photosensitive drum 1, the following members are arranged in order along the rotation direction (X1) of the photosensitive drum 1. First, a charging roller 2, which is a roller-shaped charging member serving as charging means, is arranged. Next, an exposure device (laser scanner unit) 3, which serves as exposure means, is arranged. Next, a developing device 4, which serves as developing means, is arranged. Next, a transfer roller 5, which is a roller-shaped transfer member serving as transfer means, is arranged. Next, a cleaning device 6, which serves as cleaning means, is arranged.

[0017] When a print start signal is input to the image forming apparatus 100 and image formation begins, a driving force is transmitted to the photosensitive drum 1 from a drive motor (not shown) serving as a driving means provided in the apparatus main body 110. This causes the photosensitive drum 1 to rotate in the direction indicated by arrow X1 in FIG. 1 at a predetermined peripheral speed (e.g., 300 mm / s) (process speed). In this embodiment, the photosensitive drum 1 has an aluminum drum base and an OPC photosensitive layer provided on the drum base. The charging roller 2 is disposed in contact with the photosensitive drum 1 and rotates in response to the rotation of the photosensitive drum 1. The surface (outer periphery) of the rotating photosensitive drum 1 is substantially uniformly charged to a predetermined potential of a predetermined polarity (negative in this embodiment) by the charging roller 2. At this time, a predetermined charging voltage is applied to the charging roller 2 from a charging power source (high-voltage power source) (not shown) provided in the apparatus main body 110.

[0018] The charged surface of the photosensitive drum 1 is exposed to laser light L corresponding to image information from an exposure device 3. The exposure device 3 outputs, from a laser output unit 3a, laser light (exposure beam) L modulated in accordance with a time-series electric digital image signal of image information input to a video controller 19 from a personal computer 20 or the like. The laser light L output from the exposure device 3 enters a process cartridge 120 and is irradiated onto the surface of the photosensitive drum 1. The substantially uniformly charged surface of the photosensitive drum 1 is scanned and exposed by the laser light L, thereby forming an electrostatic latent image (electrostatic image) corresponding to the image information on the surface of the photosensitive drum 1. The electrostatic latent image formed on the surface of the photosensitive drum 1 is developed by a developing device 4 with toner T (see FIG. 3) as a developer. Details of the developing device 4 will be described later.

[0019] Meanwhile, a pickup roller 8 serving as a conveying means is driven at a predetermined controlled timing to separate and feed recording materials P, such as recording paper, stacked and stored in a tray 7 serving as a recording material storage unit, one by one. As a result, the recording materials P are conveyed to a transfer unit N at a predetermined controlled timing by a conveying means (not shown). A transfer roller 5 contacts the surface of the photosensitive drum 1 with a predetermined pressing force to form a transfer unit (transfer nip) N. The recording material P is conveyed to the transfer unit N via a transfer guide 9 serving as a guide member. As the recording material P is conveyed between the photosensitive drum 1 and the transfer roller 5, the toner image, serving as a developer image on the surface of the photosensitive drum 1, is electrostatically transferred onto the surface of the recording material P during the process of passing through the transfer unit N. At this time, a transfer voltage, which is a DC voltage of a polarity opposite to the charge polarity (negative in this embodiment) of the toner during development, is applied to the transfer roller 5 from a transfer power source (high-voltage power source) (not shown) provided in the apparatus main body 110.

[0020] The recording material P with the transferred toner image is separated from the photosensitive drum 1 and transported to a fixing device 10, which serves as a fixing means and is located downstream of the transfer portion N in the transport direction of the recording material P. The recording material P is heated and pressurized in the fixing device 10 to fix the unfixed toner image. In this embodiment, the fixing device 10 includes a heating roller with an internal halogen heater and a pressure roller pressed against the heating roller. The fixing device 10 then heats and pressurizes the toner image transferred to the surface of the recording material P while nipping and transporting the recording material P in the fixing nip between the fixing roller and the pressure roller. This melts the toner image and fixes it to the surface of the recording material P. The recording material P is then discharged to a discharge tray 11 located at the top of the apparatus main body 110 in FIG. 1.

[0021] After the recording material P is separated, the surface of the photosensitive drum 1 is cleaned by the cleaning device 6 and is then repeatedly used for the image formation process starting from the charging described above. The cleaning device 6 uses a cleaning blade 61 as a cleaning member arranged in contact with the photosensitive drum 1 to remove deposits such as toner that remains untransferred during transfer from the surface of the rotating photosensitive drum 1 and collects the toner in a recovered toner container 62.

[0022] (Process cartridge) FIG. 1 is a schematic cross-sectional view of a process cartridge 120. In this embodiment, a photosensitive drum 1, a charging roller 2 as a process means acting on the photosensitive drum 1, a developing device 4, and a cleaning device 6 are integrally formed into a cartridge to constitute a process cartridge 120 that is detachable from an apparatus main body 110. The process cartridge 120 is constituted by connecting a cleaning unit 12 and a developing device 4 (also referred to as a developing unit) that is separate from the cleaning unit 12. The cleaning unit 12 has the photosensitive drum 1, the charging roller 2, and the cleaning device 6. The cleaning unit 12 also forms a collected toner container 62 and has a cleaning frame 60 for supporting the photosensitive drum 1, the charging roller 2, and a cleaning blade 61. Details of the developing device 4 will be described later.

[0023] A process cartridge generally refers to a cartridge in which an image carrier such as a photosensitive member and a process means that acts on the image carrier are integrated into one cartridge, and which is detachable from the main body of an image forming apparatus. Examples of the process means include a charging means, a developing means, a cleaning means, and a toner charging means that charges residual toner after transfer. Here, a process cartridge is defined as a cartridge in which at least a developer container or a developing device and an image carrier are integrated into one cartridge, and which is detachable from the main body of an image forming apparatus.

[0024] (developing device) 3 is a schematic cross-sectional view of the developing device 4 of this embodiment. The developing device 4 of this embodiment has a developing chamber 46a, a toner storage chamber 46b that stores developer, and a developing frame 40 that supports each element described below. The toner used as the developer in this embodiment is toner T, a one-component developer that contains a magnetic material inside. The toner storage chamber 46b has an agitator 45 having an agitator shaft 45a and an agitator sheet 45b, and the agitator 45 rotates in the X4 direction in FIG. 3 to transport the toner T to the developing chamber 46a.

[0025] The developing chamber 46a has a developing opening 46c (developing opening) at the boundary with the toner storage chamber 46b. The developing chamber 46a also has a developing roller 41, which is a cylindrical member serving as a developer carrier. Both ends of the developing roller 41 in the longitudinal direction (direction of the rotation axis) are rotatably supported by the developing frame 40. The developing roller 41 is disposed in contact with the photosensitive drum 1. A rotational driving force is transmitted to the developing roller 41 from a driving motor (not shown) provided in the apparatus main body 110, and the developing roller 41 is driven to rotate in the direction of arrow X2 in FIG. 3. A developing voltage required to develop the electrostatic latent image into a toner image is applied to the developing roller 41 from a developing voltage application unit 49b serving as a developing voltage application means.

[0026] A supply roller 43 is disposed on the periphery of the developing roller 41, rotating in the X3 direction in FIG. 3 in contact with the developing roller 41. A desired voltage is applied to the supply roller 43 as a supply member from a supply voltage application unit 49a as a supply voltage application means. In addition, a developing blade 42, which is a regulating member made of an elastic member, is disposed in the developing chamber 46a so as to abut against the outer peripheral surface of the developing roller 41. The developing blade 42 is supported by the developing frame 40.

[0027] Next, the developing roller 41, supply roller 43, and developing blade 42 will be described. The developing roller 41 has a conductive core with a silicone rubber base layer and a urethane rubber surface layer. Coarse particles are present on the surface layer of the developing roller 41 to optimize the amount of toner adhesion. The supply roller 43 is a conductive sponge roller with a urethane sponge structure in which a foamed layer is formed on a conductive core. The developing blade 42 is a metal SUS sheet metal with a resin laminate coating on the long side that contacts the developing roller 41 and forms the free end. Note that in Example 1 as well, the developing roller 41 and supply roller 43 are supported (fixed) at both longitudinal ends to the frame (not shown) of the image forming apparatus 100, as described in FIG. 10.

[0028] The developing roller 41 and the photosensitive drum 1 rotate so that their surfaces move in the same direction at the opposing portion (contact portion, developing area). In this embodiment, the developing roller 41 is arranged in contact with the photosensitive drum 1, but the developing roller 41 may also be arranged in close proximity to the photosensitive drum 1 with a predetermined gap therebetween.

[0029] The photosensitive drum 1 is electrically grounded, and a developing voltage applied to the developing roller 41 generates an electric field in the region between the photosensitive drum 1 and the developing roller 41. The charged toner T transported to the developing region is transferred to the surface of the photosensitive drum 1 by the action of this electric field in accordance with the electrostatic latent image on the surface of the photosensitive drum 1. In this way, the electrostatic latent image on the photosensitive drum 1 is developed with the toner T. In this embodiment, the photosensitive drum 1 is uniformly charged and then exposed to light, and toner T charged to the same polarity (negative polarity) as the charging polarity of the photosensitive drum 1 is attached to the exposed portion (image portion) on the photosensitive drum 1 where the absolute value of the potential has attenuated. In this way, the electrostatic latent image on the photosensitive drum 1 is developed (reverse development method).

[0030] In this embodiment, negative toner is used as the developer, but positive toner may also be used. 3The toner used contained magnetic material. The movement of the toner inside the developing container, i.e., the toner fluidity, can be understood by a physical parameter called cohesion. Cohesion is an index that indicates how easily the toner clumps together; a high cohesion value indicates poor toner fluidity, and a low value indicates good fluidity.

[0031] (supply roller) The supply roller 43 has a conductive shaft and a sponge layer containing cross-linked urethane resin on the shaft. The supply roller 43 shown in FIG. 4(a) includes a conductive shaft 52 and a sponge layer 51 containing cross-linked urethane resin disposed on the outer periphery of the conductive shaft 52. The layer configuration of the supply roller 43 is not limited to one in which the sponge layer 51 is located on the outermost surface of the supply roller 43. Examples of the supply roller 43 include a supply roller 43 having an additional surface layer on the shaft 52 and the sponge layer 51 disposed on the outer periphery of the shaft 52, or a supply roller 43 having an additional elastic layer between the shaft 52 and the sponge layer 51. The sponge layer 51 may also be molded to contain a conductive agent. This can generate a potential difference by applying a voltage or the like to the development roller 41, thereby improving the performance required of the supply roller 43. The supply roller 43 may be configured to scrape residual toner from the development roller 41 and resupply the toner. The configuration of a supply roller according to one embodiment of the present invention is described in detail below.

[0032] <Shaft> The shaft 52 functions as a support member for the supply roller 43 and as an electrode. The shaft 52 is made of a conductive material such as a metal or alloy such as aluminum, copper alloy, or stainless steel; iron plated with chromium or nickel; or a conductive synthetic resin. The shaft 52 has a solid cylindrical or hollow cylindrical shape.

[0033] <Sponge layer> The sponge layer 51 (foam layer) contains a cross-linked urethane resin, which will be described later. The sponge layer 51 preferably has voids capable of storing toner particles within the layer so that it can uniformly supply toner particles to the surface of the developing roller 41 as the supply roller 43. Examples of the voids include numerous through-holes and non-through-holes. Another example of the voids is a porous layer with interconnected bubbles (open cells). As shown in FIG. 9, when the voids are bubbles, the size of each bubble (cell) is expressed as the cell diameter. The sponge layer 51 containing the cross-linked urethane resin preferably has large open-cell voids. The characteristics of the sponge layer 51 with such voids, such as the average cell diameter, number of cells, air permeability, and density of the entire layer, are important. The physical properties of the sponge layer 51 are not particularly limited, but preferably have values ​​within the following ranges: Average surface cell diameter: 100 μm or more and 500 μm or less; Number of cells: 50 to 450 cells / inch; Airflow rate: 0.5L / min or more and 4.5L / min or less; Density: 0.05g / cm 3 More than 0.45g / cm 3 below The lower limit of the ventilation rate is the lowest value at which toner that has entered the cell can be easily expelled from the cell, and the upper limit is the maximum value at which appropriate toner can be supplied to the developing roller 41 and residual toner on the developing roller 41 can be properly scraped off.

[0034] The airflow rate can be measured using the following measurement method. As shown in FIG. 4(b), a measurement tool is prepared. The tool includes a pair of 1-cm-diameter through-holes 161a and 161b, symmetrically positioned about the center axis, on the sliding surface of a cylinder 162 having an inner diameter smaller than the outer diameter of the conductive layer, e.g., 1 mm smaller. The supply roller 43 is inserted into the measurement tool, and the conductive layer not covered by the cylinder 162 is sealed with a sealant. One through-hole 161b of the cylinder 162 is connected to a suction pump 166 equipped with a pressure gauge 164 and a flow meter 165. The other through-hole 161a of the cylinder 162 is placed under atmospheric pressure (101.3 kPa), and the suction pump 166 is driven to reduce the pressure to 125 Pa. The flow rate measured by the flow meter 165 at this time can be used as the airflow rate. This measurement can be performed not only at the center of the supply roller 43 in the longitudinal direction, but also over the entire longitudinal area.

[0035] The method for adjusting the air permeability is not particularly limited, and can be adjusted by a conventionally known method. For example, when adjusting the air permeability using a foamed elastic layer formed from a raw material composition containing polyol, polyisocyanate, blowing agent, catalyst, and foam stabilizer, a highly open cell structure can be obtained by adding a foam stabilizer that has a strong effect of opening up the cells (gas bubbles) formed in the surface layer. For example, commercially available products such as "L-3415" (trade name, manufactured by Momentive Performance Materials Japan, LLC) and "F-606" (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.) are preferably used.

[0036] Of course, the breathability of the sponge layer can also be adjusted by components other than the foam stabilizer mentioned above. For example, the amount of foaming agent added and the type and amount of catalyst added can be used to adjust the breathability by controlling the foaming and curing reactions. To increase the breathability, the curing reaction can be suppressed and the foaming reaction promoted. In addition to adjusting the material components, the breathability can also be adjusted by a method in which a roller is rotated while applying a load stress to the sponge layer, or by a manufacturing method in which high-pressure air is blown onto the sponge layer to break the membrane that forms the cell skeleton near the surface, thereby forming interconnected cells with excellent breathability.

[0037] (Method of manufacturing the supply roller) The supply roller 43 of this embodiment is molded, for example, by the following manufacturing method. A roller molding die is prepared by holding an iron cylindrical member (16.5 mm inner diameter, 260 mm long) with a release agent applied to its inner surface and a stainless steel core (5 mm outer diameter, 270 mm long) between an upper bridge member and a lower bridge member. The lower bridge member has an injection hole for injecting the foaming material into the roller molding die. A blend of premixed polyol and polyisocyanate is placed in the tank of a casting machine and stirred and mixed in the casting machine. The polyurethane foam material that will form the inner layer of the foamed elastic layer is then placed in the foaming material receiving section. Using the same procedure, the polyurethane foam material that will form the surface layer of the foamed elastic layer is then placed in the foaming material receiving section, and two types of polyurethane foam material are separated into upper and lower sections within the foaming material receiving section. The polyurethane foam material for the surface layer is prepared to foam first, while the polyurethane foam material for the inner layer is prepared to foam subsequently. The foaming material receiving section is then attached to the lower bridge member, and the roller molding die is heated to promote foaming. The foam material is cured in the mold to produce a foam elastic roller.

[0038] (Poor solid tracking) As explained in FIG. 3, toner T is transported by agitation sheet 45b and guided through development opening 46c into development chamber 46a. The supply voltage applied by supply voltage application unit 49a causes toner T to be absorbed into supply roller 43 (in sponge layer 51 thereof). The amount of toner absorbed into supply roller 43 at this time is referred to as the "absorbed amount." If the absorbed amount is small, in a solid black image, the density meets the standard for one revolution of developing roller 41, but the density thereafter does not meet the standard and becomes lighter, resulting in an image defect known as poor solid tracking. Hereinafter, in a solid black image, one revolution of developing roller 41 (the leading edge of the image or recording material in the rotation direction) is referred to as the "white trailing edge." Furthermore, the area after the white trailing edge (the trailing edge of the image or recording material) is referred to as the "black trailing edge."

[0039] There is a sufficient amount of toner on one rotation of the developing roller 41, and sufficient density can be achieved only at the leading edge of the recording material P. However, after the first rotation of the developing roller 41, the density depends on the amount of toner supplied from the supply roller 43, so if the amount is small, sufficient density cannot be achieved.

[0040] The amount of toner content depends on the charging characteristics and fluidity of the toner during image formation. Therefore, there are two ways to increase the amount of toner content: either increasing the absolute value of the supply voltage even more than the absolute value of the development voltage, or improving the fluidity of the toner in the developing chamber 46a. The former, if performed continuously, can cause deterioration of the electrical conductivity of the supply roller 43 and reduce durability, so it is not a good solution. As for the latter, toner fluidity depends in part on the specific gravity and cohesion of the toner itself, but is also greatly influenced by the posture of the process cartridge 120 and the circulation within the developing chamber 46a, so it can be improved depending on the configuration.

[0041] The developing device 4 shown in FIG. 3 is in a position where the toner storage chamber 46b is disposed above the developing chamber 46a (a so-called gravity system). In the vertical direction Dr, the developing opening 46c is located below the agitation shaft 45a, and the center (rotation axis) of the supply roller 43 is located below the developing opening 46c. In this system, when the image forming apparatus 100 starts to operate, the toner T transferred to the developing chamber 46a by the agitation sheet 45b does not return to the toner storage chamber 46b, but remains in the direction of gravity (the vertical direction Dr), i.e., in the developing chamber 46a, even when the agitation sheet 45b stops operating. In this situation, if the agitation sheet 45b continues to rotate, the toner T in the developing chamber 46a is pushed in by its own weight, causing a clogging of the toner T and hindering toner circulation. At this time, the toner T collides with the wall of the developing device 4 and gathers, being pushed toward the center. Then, the toner T collected from both wall surfaces passes through the developing opening 46c, and a large powder pressure of the toner T is applied to the midpoint of the supply roller 43.

[0042] In this state, the supply roller 43 cannot adequately contain toner T, resulting in a low toner content. Furthermore, even after toner T is expelled onto the developing roller 41 due to the potential difference between the supply voltage and the developing voltage, the next toner T to be supplied is not properly supplied to the supply roller 43. This phenomenon occurs more easily after black printing than after white printing, and the amount of toner that is contained is more likely to be low. This causes poor solid image tracking. For this reason, in a solid black image where all the toner on the developing roller 41 needs to be expelled onto the photosensitive drum 1, the gravity-based developing device 4 exhibits particularly noticeable poor solid image tracking in the longitudinal center of the black image.

[0043] To solve this problem, other than adjusting the toner itself, one method for improving fluidity is to increase the amount of toner contained inside the supply roller 43 by increasing the amount of airflow through the supply roller 43. FIG. 5(a) is a graph showing the amount of airflow [L / min] through the supply roller 43 of this embodiment on the horizontal axis and the amount of toner contained in the black backing [g] on the vertical axis. As shown in the graph of FIG. 5(a), it can be seen that there is a correlation between the amount of airflow through the supply roller 43 for the black backing and the amount of toner contained. Specifically, the amount of toner contained increases as the amount of airflow increases. In this embodiment, poor solid printing performance occurs unless the amount of toner T contained in the supply roller 43 is 7g or more.

[0044] (Disadvantages of increasing ventilation and solutions) Next, we will discuss the issues associated with increasing the ventilation rate of the supply roller 43. Increasing the ventilation rate strengthens the foaming of the sponge, which tends to suppress the cross-linking structure of the sponge, making the supply roller 43 itself softer and more susceptible to deformation. If the process cartridge 120 is transported in a high-temperature, high-humidity environment or left standing for a long period of time with the ventilation rate increased, the supply roller 43 may be severely deformed permanently at the contact point between the supply roller 43 and the developing roller 41 due to the rigidity of the developing roller 41. A deformed supply roller 43 may cause image defects such as horizontal bands called supply roller sets in halftone images and solid black images. The contact pressure between the supply roller 43 and the developing roller 41 is stronger at the longitudinal ends where the fixed ends are located than at the longitudinal center, making the supply roller 43 particularly susceptible to deformation.

[0045] In FIG. 5(b), the horizontal axis shows the airflow rate [L / min] of the supply roller 43 of this embodiment, and the vertical axis shows the deformation [mm] of the supply roller 43 after being left in a harsh environment. Note that the harsh environment is the high-temperature, high-humidity environment described above. The graph in FIG. 5(b) shows the relationship between the airflow rate and deformation of the supply roller 43 after the supply roller 43 was left in a high-temperature, high-humidity environment with a temperature of 50°C and a humidity of 60% for three days. As shown in FIG. 5(b), the deformation rate increases as the airflow rate increases. In this embodiment, when the deformation rate exceeds 0.2 mm, horizontal bands become visible, causing image degradation (NG level).

[0046] Therefore, in this embodiment, both the poor solid image tracking problem, which can be solved by increasing the airflow rate, and the supply roller set problem, which occurs when the airflow rate is increased, are solved in the following way: that is, the poor solid image tracking problem is suppressed while the supply roller set problem is prevented. That is, in this embodiment, these image defects are solved by changing the airflow rate between the longitudinal ends and the central portion of the supply roller 43. As explained above, the poor solid image tracking problem occurs in the longitudinal central portion of the supply roller 43, while the supply roller set problem occurs at the ends. Therefore, by increasing the airflow rate in the longitudinal central portion of the supply roller 43 to a level where the poor solid image tracking problem does not occur, and by decreasing the airflow rate at both ends to a level where the supply roller set problem does not occur, both of these problems are solved.

[0047] (Method of changing the ventilation volume in the longitudinal direction) (Method 1) Two examples of methods for changing the air permeability between the center and both ends in the longitudinal direction of the supply roller 43 will be described below. The first is a pattern in which sponge layers 51 with different air permeabilities are joined as shown in FIG. 6. FIG. 6 shows method 1 for changing the air permeability in the longitudinal direction in this embodiment. As shown in FIG. 6(a), first, sponge rollers with two different air permeabilities, air permeability A (second air permeability) and air permeability B (first air permeability), are made. Note that air permeability A is lower than air permeability B (A <B)。

[0048] As shown in Figure 6(b), in supply roller 43, a primer adhesive is applied to the rod-shaped core (shaft 52), and a sponge roller with high air permeability B and a sponge roller with low air permeability A are inserted. Hereinafter, the sponge roller with air permeability B will be referred to as sponge roller 51B (first sponge roller), and the sponge roller with air permeability A will be referred to as sponge roller 51A (second sponge roller). Sponge roller 51B is placed in the center in the longitudinal direction of the rod-shaped core, and sponge rollers 51A are placed at both ends of sponge roller 51B, i.e., at both ends in the longitudinal direction.

[0049] As shown in Fig. 6(c), sponge rollers 51A and 51B are closely spaced and bonded together in the longitudinal direction (the dashed line α portion). In this way, by using the method shown in Fig. 6, supply roller 43 with different ventilation amounts in the longitudinal direction can be produced.

[0050] (Method 2) The other method, Method 2, involves subjecting the completed sponge roller to a crushing process, gradually changing the airflow rate along its length. Figure 7 shows Method 2 for changing the airflow rate along its length. Figure 7 is a schematic diagram of the crushing section of the crushing device used in the crushing process. The crushing process is as follows: The sponge roller is sandwiched between two metal drums 1000 and 1001, and while pressure is applied to the foamed sponge layer, air is blown onto the sponge surface using an air nozzle 90. This breaks the surface cells of the sponge roller and opens the cells to the interior of the sponge. The crushing process is performed to stabilize the hardness and airflow rate of the supply roller 43, which are its performance characteristics. An air nozzle 90 with a diameter of 1 / 10 to 1 / 4 of the diameter of the supply roller 43 is positioned 5 to 30 mm from the surface of the supply roller 43. While the air nozzle 90 is moved in the axial direction Da of the supply roller 43, which is rotating at a speed of 1 rpm to 300 rpm, high-pressure air of 0.2 MPa to 1.0 MPa is sprayed from a direction approximately perpendicular to the surface of the supply roller 43.

[0051] At this time, the degree of cell interconnectivity in the longitudinal direction can be changed by varying the speed at which the air nozzle 90 is applied and the rotation speed of the supply roller 43 itself depending on the position in the longitudinal direction. For example, if the rotation speed of the supply roller 43 is increased to 300 rpm while keeping the longitudinal movement speed of the air nozzle 90 constant, the amount of air entering the supply roller 43 is reduced, making it difficult to increase the amount of ventilation. On the other hand, if the rotation speed of the supply roller 43 is decreased to 1 rpm, sufficient air enters the supply roller 43, making it easier to increase the amount of ventilation. Conversely, the amount of ventilation can also be controlled by keeping the rotation speed of the supply roller 43 at 100 rpm and slowing the longitudinal movement speed of the air nozzle 90 only at the center compared to the ends. During this crushing process, the amount of ventilation through the supply roller 43 can be continuously changed in the longitudinal direction.

[0052] (Area of ​​change in ventilation volume in the longitudinal direction) Consider the airflow rate of the supply roller 43 that will solve both the problems of poor solid tracking and supply roller set. To prevent poor solid tracking in this embodiment, the load inside the supply roller 43 must be 7.0 g or more, and the airflow rate at this time must be 2.5 L / min or more, as described in FIG. 5(a). To prevent supply roller set in this embodiment, the deformation must be 0.2 mm or less, and the airflow rate at this time must be 2.0 L / min or less, as described in FIG. 5(b).

[0053] The minimum airflow rate required for the supply roller 43 to suck in and expel toner is between 0.5 L / min and 4.5 L / min. Therefore, it is desirable to set the airflow rate in the center to between 2.5 L / min and 4.5 L / min to prevent poor solid printing performance, and to set the airflow rate at both ends to between 0.5 L / min and 2.0 L / min to prevent supply roller set. If the airflow rate in the center in the longitudinal direction is 4.5 L / min or more, supply roller set becomes an issue even in the center. Furthermore, if the airflow rate at the ends in the longitudinal direction is less than 0.5 L / min, the supply roller 43 will not be able to absorb enough toner, and it will not be able to function as the supply roller 43.

[0054] The position for measuring the air permeability was the midpoint in the longitudinal direction in the center, and at both ends, it was measured at a position 1 / 10 of the way from both ends toward the midpoint in the longitudinal direction. The air permeability measured at each position should be within the above range. Details and effects will be described in the following examples.

[0055] (Evaluation experiment) The experiment conducted to demonstrate the effects of this embodiment will be described below. The supply roller 43 used in this embodiment, which has different air permeability rates at the center and ends in the longitudinal direction, and several supply rollers shown in Table 1 below as comparative examples, were assembled into the process cartridge 120 shown in FIG. 2 and stored for three days in a harsh environment of 50°C temperature and 60% humidity. After that, 600 g of toner was loaded, and an all-black image and a halftone image were printed in an environment of 22.5°C temperature and 40% humidity, and solid image tracking failure and supply roller assembly were evaluated. The halftone image in this embodiment was an image pattern with a density of 0.6 in X-rite.

[0056] [Table 1] In Table 1, the first column shows Examples 1 to 4 and Comparative Examples 1 to 10, the second column shows the air permeability [L / min] at the center in the longitudinal direction of the supply roller 43 for each example, and the third column shows the air permeability [L / min] at the end in the longitudinal direction of the supply roller 43 for each example.

[0057] Examples 1 to 4 satisfy the condition that the air permeability at the center is 2.5 L / min to 4.5 L / min and the condition that the air permeability at both ends is 0.5 L / min to 2.0 L / min, respectively. On the other hand, Comparative Examples 1 to 10 do not satisfy the condition that the air permeability at the center is 2.5 L / min to 4.5 L / min and / or the condition that the air permeability at both ends is 0.5 L / min to 2.0 L / min.

[0058] To evaluate poor solid image tracking, the density of the leading edge and trailing edge of the image in the longitudinal direction was measured using an X-Rite, and the ratio of the leading edge density to the trailing edge density was calculated and ranked into A to C as the evaluation criteria. Similarly, the image edges in the longitudinal direction were also ranked. The goal for the image forming apparatus was to achieve rank B or higher. A: The density at the center of the tip is 1.35 or more and the density ratio is 0.91 or more B: The density at the center of the tip is 1.35 or more and the density ratio is 0.71 or more but less than 0.91 C: The density at the center of the tip is 1.35 or more and the density ratio is less than 0.71

[0059] The supply roller set was evaluated by ranking it from A to C based on the difference in density between horizontal bands that appeared on the halftone image at intervals equivalent to the circumferential length of the supply roller 43 or developing roller 41, extending from either end of the image to 2 / 10 of the total in the longitudinal direction, and the surrounding area. Similarly, supply roller sets that occurred in the center in the longitudinal direction were also ranked. The goal for the image forming apparatus was to achieve rank B or higher. A: Horizontal bands cannot be identified B: Horizontal bands are slightly visible, but the density difference is less than 0.1 C: Horizontal bands can be seen, and the density difference is 0.1 or more

[0060] Table 2 below summarizes the image rank for each example after printing. FIG. 8(a) is a graph showing the ratio of density at the trailing end to the density at the leading end (density ratio) versus the amount of airflow at the center and end of the supply roller 43 in the longitudinal direction. In FIG. 8(a), the horizontal axis shows the amount of airflow [L / min], and the vertical axis shows the ratio of density at the trailing end to the density at the leading end (density ratio). FIG. 8(b) is a graph showing the amount of deformation versus the amount of airflow at the center and end of the supply roller 43 in the longitudinal direction. In FIG. 8(b), the horizontal axis shows the amount of airflow [L / min], and the vertical axis shows the amount of deformation [mm]. In both graphs, the center is indicated by a solid line, and the end is indicated by a dashed line.

[0061] [Table 2] In Table 2, the first column shows Examples 1 to 4 and Comparative Examples 1 to 10. The second column shows poor solid tracking at the longitudinal ends of the supply roller 43 (poor solid tracking at the ends), and the third column shows poor solid tracking at the longitudinal center of the supply roller 43 (poor solid tracking at the centers). The fourth column shows supply roller sets at the longitudinal ends of the supply roller 43 (poor solid tracking at the centers), and the fifth column shows supply roller sets at the longitudinal center of the supply roller 43 (poor solid tracking at the centers).

[0062] From the results in Table 2, the ranking of poor edge solid tracking was Rank A when the air permeability was 2.5 L / min or more, Rank B when it was 0.5 L / min or more but less than 2.5 L / min, and Rank C when it was less than 0.5 L / min. Also, the ranking of poor center solid tracking was Rank A when the air permeability was over 3.0 L / min, Rank B when it was 2.5 L / min or more but less than 3.0 L / min, and Rank C when it was less than 2.5 L / min.

[0063] As shown in the graph in FIG. 8(a), the range of air permeability required for a rank C differs between the ends and the center of supply roller 43. Specifically, according to the results in Table 2, the air permeability required for a rank C is less than 0.5 L / min at the ends and less than 2.5 L / min at the center. Because the toner powder pressure is more intense in the center than at the ends, and fluidity is reduced, the range of air permeability required for a rank C for poor solid print performance is wider in the center. In Comparative Examples 1, 3, 4, 6, and 7, the air permeability at the center was less than 2.5 L / min, and the poor solid print performance was ranked C. In Comparative Example 9, the air permeability at the ends was less than 0.5 L / min, and supply roller 43 was unable to properly discharge toner, resulting in a small toner load, resulting in a rank C for poor solid print performance even at the ends.

[0064] Regarding the supply roller sets, the end supply roller sets were ranked A for less than 1.5 L / min, B for 1.5 L / min to 2.0 L / min, and C for over 2.0 L / min. The center supply roller sets were ranked A for less than 3.5 L / min, B for 3.5 L / min to 4.5 L / min, and C for over 4.5 L / min.

[0065] As shown in the graph in Figure 8(b), the range of air permeability at which the deformation exceeds 0.2 mm and is classified as Rank C differs between the ends and the center of supply roller 43. Specifically, the air permeability at the ends exceeds 2.0 L / min, while at the center it exceeds 4.5 L / min. The ends have larger deformations than the center because the fixed end shafts are closer, and the range of air permeability at which the supply roller set is classified as Rank C is wider. Figure 8(b) and Table 2 show that a deformation of 0.17 mm or less corresponds to Rank A, a deformation of 0.18 mm to 0.20 mm corresponds to Rank B, and a deformation of 0.2 mm or more corresponds to Rank C.

[0066] In Comparative Examples 2, 3, 5, and 8, the air permeability at the ends exceeded 2.0 L / min, and the deformation increased to more than 2.0 mm, resulting in the evaluation of the supply roller set as rank C. In Comparative Example 10, the air permeability at the center was 4.5 L / min or more, resulting in more voids in the sponge layer, and the deformation exceeded 0.2 mm even at the center, resulting in the evaluation of the supply roller set as rank C.

[0067] From these results, in order to achieve both poor solid print followability and a supply roller set evaluation of rank B or higher, the air permeability in the center must be 2.5 L / min to 4.5 L / min and the air permeability in the end must be 0.5 L / min to 2.0 L / min. Therefore, in Examples 1 to 4, supply roller 43 with appropriate air permeability in the center and end was used, and therefore both poor solid print followability and the supply roller set were evaluated as rank B or higher, thereby solving both problems.

[0068] Furthermore, the ratio of central air permeability to edge air permeability required to achieve rank B or higher was 1.25 or more and 9 or less, and to achieve rank A or higher, which solves at least both the problems of poor central solid tracking and edge supply roller set, it was 2 or more and 9 or less.

[0069] As described above, according to this embodiment, even when the ventilation amount of the supply roller is increased, the occurrence of image defects can be reduced.

[0070] The disclosure of this embodiment includes the following configurations and methods. (Configuration 1) a developer carrier that carries a developer and develops the electrostatic latent image with the developer to form a developer image; a supply roller that contacts the developer carrier and supplies the developer to the developer carrier; a storage chamber for holding the developer; a developing chamber having the developer carrier and the supply roller; a developing opening separating the developing chamber from the containing chamber; a stirring shaft provided in the accommodation chamber; an agitating member that rotates around the agitating shaft in the containing chamber to agitate the developer; Equipped with When the supply roller is attached to the image forming apparatus and both ends of the supply roller in the longitudinal direction are supported by a frame of the image forming apparatus, the developing opening is located above the rotation axis of the supply roller, the stirring shaft is installed above the developing opening, The developing device is characterized in that the absolute value of the air permeability at the center of the supply roller in the longitudinal direction is greater than the absolute value of the air permeability at a position one-tenth of the way from the end. (Configuration 2) The supply roller is characterized in that the absolute value of the air permeability at the center in the longitudinal direction is 2.5 L / min or more and 4.5 L / min or less, the absolute value of the air permeability at both ends in the longitudinal direction is 0.5 L / min or more and 2 L / min or less, and the ratio of the air permeability at the center to the air permeability at the ends is 1.25 or more and 9 or less. (Configuration 3) 3. The developing device according to claim 1, wherein the ratio of the amount of air permeation at the center portion to the amount of air permeation at the ends in the longitudinal direction of the supply roller is 2 or more and 9 or less. (Configuration 4) 4. The developing device according to any one of configurations 1 to 3, wherein the supply roller has a conductive sponge layer. (Configuration 5) 5. The developing device according to claim 4, wherein the sponge layer contains a cross-linked urethane resin. (Configuration 6) An image forming apparatus for forming an image on a recording material, an image carrier that carries an electrostatic latent image; a developing device according to any one of configurations 1 to 5 that develops the electrostatic latent image; An image forming apparatus comprising: (Configuration 7) a supply roller that contacts a developer carrier and supplies developer to the developer carrier, When the image forming apparatus is attached to the image forming apparatus and both ends of the image forming apparatus are supported by the frame of the image forming apparatus, A supply roller characterized in that the absolute value of the air permeability at the center in the longitudinal direction is greater than the absolute value of the air permeability at a position one-tenth of the way from the end. (Method 1) A method of manufacturing a supply roller that contacts a developer carrier and supplies developer to the developer carrier, comprising the steps of: a step of applying a primer coat of adhesive to a rod-shaped mandrel; inserting the core into the first sponge roller and the second sponge roller so that a first sponge roller with a first air permeability is disposed in the center of the core in the longitudinal direction, and second sponge rollers with a second air permeability lower than the first air permeability are disposed at both ends of the core in the longitudinal direction; a step of adhering a second sponge roller disposed at one end to the first sponge roller in the longitudinal direction, and adhering a second sponge roller disposed at the other end to the first sponge roller; A method for manufacturing a supply roller, comprising: (Method 2) A method of manufacturing a supply roller that contacts a developer carrier and supplies developer to the developer carrier, comprising the steps of: A process of sandwiching a sponge roller between two metal drums, a step of blowing air onto the surface of the sponge roller while moving an air nozzle in the longitudinal direction while applying pressure to the sponge roller with the two metal drums; Equipped with In the step of blowing air, a moving speed of the air nozzle in the longitudinal direction is kept constant, and a rotation speed of the sponge roller when the air nozzle is blowing air onto the sponge roller at the end portion is made faster than a rotation speed when the air nozzle is blowing air onto the sponge roller at the central portion; Or, A method for manufacturing a supply roller, characterized in that the rotation speed of the sponge roller is constant and the movement speed of the air nozzle when moving at the end is faster than the movement speed of the air nozzle when moving at the center. [Explanation of symbols]

[0071] 1 Photosensitive drum 41 Developing roller 43 Supply roller 45a Stirring shaft 45b Stirring sheet 46a Developing Room 46b Toner Storage Room 46c developing opening

Claims

1. a developer carrier that carries a developer and develops the electrostatic latent image with the developer to form a developer image; a supply roller that contacts the developer carrier and supplies the developer to the developer carrier; a storage chamber for holding the developer; a developing chamber having the developer carrier and the supply roller; a developing opening separating the developing chamber from the containing chamber; a stirring shaft provided in the accommodation chamber; an agitating member that rotates around the agitating shaft in the containing chamber to agitate the developer; Equipped with When the supply roller is attached to the image forming apparatus and both ends of the supply roller in the longitudinal direction are supported by a frame of the image forming apparatus, the developing opening is located above the rotation axis of the supply roller, the stirring shaft is installed above the developing opening, The developing device is characterized in that the absolute value of the air permeability at the center of the supply roller in the longitudinal direction is greater than the absolute value of the air permeability at a position one-tenth of the way from the end.

2. 2. The developing device according to claim 1, wherein the absolute value of the air permeability at the center in the longitudinal direction of the supply roller is 2.5 L / min or more and 4.5 L / min or less, the absolute value of the air permeability at both ends in the longitudinal direction is 0.5 L / min or more and 2 L / min or less, and the ratio of the air permeability at the center to the air permeability at the ends is 1.25 or more and 9 or less.

3. 2. The developing device according to claim 1, wherein the ratio of the amount of air permeation at the central portion to the amount of air permeation at the end portions in the longitudinal direction of the supply roller is 2 or more and 9 or less.

4. 2. The developing device according to claim 1, wherein the supply roller has a conductive sponge layer.

5. 5. The developing device according to claim 4, wherein the sponge layer contains a cross-linked urethane resin.

6. An image forming apparatus for forming an image on a recording material, an image carrier that carries an electrostatic latent image; a developing device according to any one of claims 1 to 5, which develops the electrostatic latent image; An image forming apparatus comprising:

7. a supply roller that contacts a developer carrier and supplies developer to the developer carrier, When the image forming apparatus is attached to the image forming apparatus and both ends of the image forming apparatus are supported by the frame of the image forming apparatus, A supply roller characterized in that the absolute value of the air permeability at the center in the longitudinal direction is greater than the absolute value of the air permeability at a position one-tenth of the way from the end.

8. A method of manufacturing a supply roller that contacts a developer carrier and supplies developer to the developer carrier, comprising the steps of: a step of applying a primer coat of adhesive to a rod-shaped mandrel; inserting the core into the first sponge roller and the second sponge roller so that a first sponge roller with a first air permeability is disposed at the center of the core in the longitudinal direction, and second sponge rollers with a second air permeability lower than the first air permeability are disposed at both ends of the core in the longitudinal direction; a step of adhering a second sponge roller disposed at one end to the first sponge roller in the longitudinal direction, and adhering a second sponge roller disposed at the other end to the first sponge roller; A method for manufacturing a supply roller, comprising:

9. A method of manufacturing a supply roller that contacts a developer carrier and supplies developer to the developer carrier, comprising the steps of: a step of sandwiching the sponge roller between two metal drums; a step of blowing air onto the surface of the sponge roller while moving an air nozzle in the longitudinal direction while applying pressure to the sponge roller by the two metal drums; Equipped with In the step of blowing air, a moving speed of the air nozzle in the longitudinal direction is kept constant, and a rotation speed of the sponge roller when the air nozzle is blowing air onto the sponge roller at the end portion is made faster than a rotation speed when the air nozzle is blowing air onto the sponge roller at the central portion; Or, A method for manufacturing a supply roller, characterized in that the rotation speed of the sponge roller is constant and the movement speed of the air nozzle when moving at the end is faster than the movement speed of the air nozzle when moving at the center.

Images