Image forming apparatus

Abstract

The invention relates to an image forming apparatus. The image forming apparatus includes an image bearing roller, a developing roller, and a supply roller. In a first period in which the developing roller moves from a separation position to a contact position, circumferential speeds of the image bearing roller, the developing roller, and the supply roller are Vo1, Vd1, and Vr1, respectively, and in a second period in which an electrostatic latent image is formed on the image bearing roller, circumferential speeds of the image bearing roller, the developing roller, and the supply roller are Vo2, Vd2, and Vr2, respectively. The controller performs control so as to satisfy the following relationships: Vo1-Vd1lt; vo2-Vd2, Vd1-Vr1lt, Vd1-Vr1lt; vd2-Vr2, and the circumferential speeds of the image bearing roller, the developing roller, and the supply roller are monotonically changed from Vo1 to Vo2, monotonically changed from Vd1 to Vd2, and monotonically changed from Vr1 to Vr2.

Description

Technical Field

[0001] The present invention relates to an image forming apparatus, and to an image forming apparatus such as a copier, printer and fax machine, for example, using electrophotographic or electrostatic recording types. Background Technology

[0002] Electrophotographic image forming apparatus includes an image forming process that includes the steps of uniformly charging the surface of a photosensitive drum, which serves as an image carrier, to a predetermined polarity and potential; forming an electrostatic latent image on the charged surface; and developing the electrostatic latent image using a toner as a developer. Furthermore, as the type of development used to develop the electrostatic latent image formed on the photosensitive drum, contact development is generally used. This contact development type performs development by bringing a developing roller, which serves as a developer carrier, into contact with the photosensitive drum.

[0003] Contact developing types include a contact and separation mechanism between the developing roller and the photosensitive drum in the contact portion between the developing roller and the photosensitive drum, in order to prevent deformation of the elastic developing roller. The contact and separation mechanism is a structure that brings the photosensitive drum and the developing roller into contact with each other during image formation and separates them during periods other than image formation. In image forming apparatuses provided with contact and separation mechanisms, for example, in Japanese Patent Application Publication No. 2006-085127, to reduce impact jitter in the image caused by vibration of the photosensitive drum due to impact during contact, the photosensitive drum and the developing roller are brought into contact with each other while the circumferential speed of the photosensitive drum is set to a low speed. A configuration that absorbs the impact during contact in this way is proposed. Furthermore, for example, in Japanese Patent Application Publication No. H05-107902, when there is contact between photosensitive drums and developing rollers with different circumferential speeds, to prevent image disturbance caused by uneven rotation due to load fluctuations in the photosensitive drum, the circumferential speeds of the photosensitive drum and the developing roller are set to be the same during contact. A configuration to reduce rotational unevenness in this way is proposed. Summary of the Invention

[0004] To address the aforementioned problems, the present invention includes the following configuration.

[0005] (1) An image forming apparatus, comprising: a rotatable image carrier member on which an electrostatic latent image is formed; a rotatable developing member configured to supply developer to the image carrier member, develop the electrostatic latent image, and form a developer image; a rotatable supply member configured to supply developer to the developing member by contacting the developing member; a moving portion configured to move the developing member to a contact position where the developing member contacts the surface of the image carrier member, or to a separation position where the developing member is separated from the surface of the image carrier member; a driving source configured to drive the image carrier member, the developing member, and the supply member; and a control member configured to control the moving portion and the driving source, wherein, during a first time period in which the developing member is moved from the separation position to the contact position by the moving portion before the electrostatic latent image is formed on the image carrier member, when the circumferential speed, which is the moving speed of the surface of the image carrier member, is defined as Vo1, ... The circumferential velocity of the surface moving on the developing member is defined as Vd1, the circumferential velocity of the surface moving on the supply member is defined as Vr1, the absolute value of the difference between the circumferential velocity of the image carrier member and the circumferential velocity of the developing member is defined as |Vo1-Vd1|, and the absolute value of the difference between the circumferential velocity of the developing member and the circumferential velocity of the supply member is defined as |Vd1-Vr1|, and during the second time period when the electrostatic latent image is formed on the image carrier member, when the surface of the image carrier member... When the circumferential velocity of the moving surface is defined as Vo2, the circumferential velocity of the moving surface of the developing member is defined as Vd2, the circumferential velocity of the moving surface of the supply member is defined as Vr2, the absolute value of the difference between the circumferential velocity of the image carrying member and the circumferential velocity of the developing member is defined as |Vo2-Vd2|, and the absolute value of the difference between the circumferential velocity of the developing member and the circumferential velocity of the supply member is defined as |Vd2-Vr2|, the control unit controls the drive source to satisfy the following relationship:

[0006] |Vo1-Vd1|<|Vo2-Vd2|, and

[0007] |Vd1-Vr1|<|Vd2-Vr2|, and

[0008] So that the circumferential speed of the moving speed of the surface of the image carrier member is monotonically changed from Vo1 to Vo2, the circumferential speed of the moving speed of the surface of the developing member is monotonically changed from Vd1 to Vd2, and the circumferential speed of the moving speed of the surface of the supply member is monotonically changed from Vr1 to Vr2.

[0009] Further features of the present invention will become clear from the following description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0010] Figure 1 This is a diagram of the image forming apparatus in Embodiments 1 and 2.

[0011] Figure 2 This is a block diagram of the control configuration of the image forming apparatus in Embodiments 1 and 2.

[0012] Figure 3 This is a diagram of the processing box in Embodiments 1 and 2.

[0013] Figure 4 This includes timing diagrams of contact and separation in Example 1, as well as the circumferential velocity of each component.

[0014] Figure 5 The timing diagram includes contact and separation in Comparative Example 1 of Embodiment 1, as well as the circumferential velocity of each component.

[0015] Figure 6 Parts (a) and (b) include diagrams illustrating the unevenness of the toner-containing feed rollers during contact and separation in Example 1.

[0016] Figure 7 This is a graph showing the torque fluctuation of the developing roller in Example 1.

[0017] Figure 8 This includes a timing diagram of contact and separation, development voltage, and supply voltage as shown in Example 2. Detailed Implementation

[0018] In the following description, suitable embodiments of the invention will be described in detail by way of example, with reference to the accompanying drawings. However, the dimensions, materials, shapes, and relative arrangements of the constituent components described in the embodiments are not intended to limit the scope of the invention thereto, unless otherwise specifically stated. Furthermore, the materials, shapes, etc., of components described once in the following description are the same as those described in the first description, unless otherwise specifically stated again.

[0019] [Example 1]

[0020] <Summary of the configuration of the image forming apparatus>

[0021] refer to Figure 1 The operation of the image forming apparatus 100 in Embodiment 1 will be described. Figure 1 This is a schematic cross-sectional view of the image forming apparatus 100 with processing cartridge 88 provided in Embodiment 1. The image forming apparatus 100 in Embodiment 1 is a full-color laser beam printer employing an inline type and intermediate transfer type. The image forming apparatus 100 can form a full-color image on a transfer material P (e.g., recording sheet, plastic sheet, fabric, etc.) as the transfer material based on image information. Image information is input to the main component of the image forming apparatus 100 from an image reading device connected to the main component of the image forming apparatus 100 or a host device such as a personal computer communicatively connected to the main component of the image forming apparatus 100.

[0022] In the image forming apparatus 100, Figure 1 In the center, from left to right, four image forming stations (hereinafter also referred to as image forming sections) for yellow, magenta, cyan, and black are provided side by side. Each image forming section is an electrophotographic image forming mechanism that is identical to the others, except that the color of the toner 90 contained as the developer in each developing device 4 is different. Incidentally, in the following description, unless it is necessary to make special distinctions, the subscripts Y (yellow), M (magenta), C (cyan), and K (black) indicating that the elements are provided for one of the colors will be omitted, and the elements will be described uniformly.

[0023] The processing cartridge 88 is configured to be mountable to and removable from the image forming apparatus 100 via mounting components such as mounting guides and positioning members provided in the main assembly of the image forming apparatus 100. In Embodiment 1, all processing cartridges 88 for each color have the same shape, and each processing cartridge 88 for each color contains toner for each of the following colors: Y (yellow), M (magenta), C (cyan), and K (black). The processing cartridge 88 includes a developing apparatus 4, and the developing apparatus 4 includes a developing roller 42, a supply roller 43, and an adjusting blade 44.

[0024] The photosensitive drum 1, which serves as the image carrier, is driven by a motor 85 (see...). Figure 2The charging roller 2 uniformly charges the surface of the photosensitive drum 1. A scanner unit 3 is deployed around the photosensitive drum 1. The scanner unit 3 is an exposure component that forms an electrostatic latent image on the photosensitive drum 1 by irradiating a laser based on an image signal. Opposite to the four photosensitive drums 1, an intermediate transfer belt 53 is deployed as an intermediate transfer member for transferring the toner image (developer image) on the photosensitive drum 1 to the transfer material P. The intermediate transfer belt 53, formed by an annular belt, contacts all the photosensitive drums 1 and moves (rotates) cyclically in the direction of arrow B in the figure.

[0025] On the inner circumferential surface side of the intermediate transfer belt 53, opposite to each photosensitive drum 1, four primary transfer rollers 51Y, 51M, 51C, and 51K are provided side-by-side as primary transfer components. Furthermore, a primary transfer voltage power supply 73 (see [link to primary transfer voltage application component]) is used to apply the primary transfer voltage. Figure 2 A voltage of opposite polarity to the normal charging polarity of the toner is applied to the primary transfer roller 51. As a result, the toner image on the photosensitive drum 1 is transferred (primary transfer) to the intermediate transfer belt 53. The portion of the toner image transferred from the photosensitive drum 1 to the intermediate transfer belt 53 is referred to as the primary transfer portion.

[0026] Furthermore, a secondary transfer roller 52 (transfer member) serving as a secondary transfer component is deployed on the outer peripheral surface side of the intermediate transfer belt 53. And, a secondary transfer voltage power supply 74 (see [link to relevant documentation]) serves as a secondary transfer voltage application component. Figure 2 A voltage of opposite polarity to the normal charging polarity of the toner is applied to the secondary transfer roller 52. As a result, the toner image on the intermediate transfer belt 53 is transferred (secondary transfer) to the transfer material P. The portion where the toner image is transferred from the intermediate transfer belt 53 to the transfer material P is called the secondary transfer portion. For example, during the formation of a full-color image, the above process is performed sequentially in the image forming portions Y, M, C, and K, and the toner images of each color are sequentially superimposed and transferred once onto the intermediate transfer belt 53. Thereafter, the transfer material P is conveyed to the secondary transfer portion in sync with the movement of the intermediate transfer belt 53. Furthermore, through the action of the secondary transfer roller 52, which contacts the intermediate transfer belt 53 via the transfer material P, the toner images of the four colors on the intermediate transfer belt 53 are transferred together onto the transfer material P. The transfer material P, on which the unfixed toner image is transferred, is conveyed to the fixing device 6, which serves as the fixing component. By applying heat and pressure to the transfer material P in the fixing device 6, the toner image is fixed onto the transfer material P, and the transfer material P is discharged outside the image forming apparatus 100 as an image forming product.

[0027] Control of the image forming apparatus

[0028] Figure 2This is a block diagram illustrating the general control mode of the main parts of the image forming apparatus 100 in Embodiment 1. The control unit 202 is a component that controls the operation of the image forming apparatus 100 and sends and receives various types of electrical information signals. Furthermore, the control unit 202 processes electrical information signals input from various types of processing devices and sensors, as well as command signals to various types of processing devices. The controller 200 sends and receives various types of electrical information from the host device, and, according to a predetermined control program and reference table, jointly controls the image forming operation of the image forming apparatus 100 with the control unit 202 via the interface 201.

[0029] The control section 202, serving as a control unit, includes a CPU 155 as the central element performing various computational processes, and a memory 15 such as RAM and ROM as storage elements. The RAM stores sensor detection results, counter counting results, calculation results, etc., while the ROM stores control programs, data tables obtained through prior experiments, etc. Each control target, sensor, counter, etc., in the image forming apparatus 100 is connected to the control section 202. The control section 202 executes control of a predetermined image forming sequence by controlling the transmission and reception of various types of electrical information signals, and the timing of the driving of each component.

[0030] The control unit 202 controls, for example, the following high-voltage power supply and equipment to form a toner image on the surface of the photosensitive drum 1. Specifically, the control unit 202 controls the charging voltage power supply 71, the developing voltage power supply 72, the supply voltage power supply 75, the adjusting doctor blade voltage power supply 76, the scanner unit 3, etc. Here, the charging voltage power supply 71 is a charging voltage application member that applies a charging voltage to the charging roller 2. The developing voltage power supply 72 is a developing voltage application member that applies a developing voltage to the developing roller 42. The supply voltage power supply 75 is a supply voltage application member that applies a supply voltage to the supply roller 43. The adjusting doctor blade 44 is a toner adjustment member, and the adjusting doctor blade voltage power supply 76 is a power supply for adjusting the doctor blade 44. In addition, the control unit 202 controls the primary transfer voltage power supply 73, the secondary transfer voltage power supply 74, etc. In addition to these, the control unit 202 performs control of the contact and separation mechanism 50 and the drive transmission unit 80, which performs contact and separation between the photosensitive drum 1 and the developing roller 42, and the drive transmission unit 80 performs control of the drum unit 11 (see...). Figure 3 The drive transmission section 80 transmits the driving force of the drive motor 85 to the drum unit 11 and the developing equipment 4. The photosensitive drum 1, the developing roller 42, and the supply roller 43 rotate under the driving force of the drive motor 85.

[0031] <Summary of Processor Box Configuration>

[0032] The overall configuration of the processing cartridge 88 installed in the image forming apparatus 100 of Embodiment 1 will be described. In Embodiment 1, the drum unit 11 and the developing device 4 are integrated into the processing cartridge 88. Figure 3 This is a main cross-sectional view of the processing cartridge 88 in Embodiment 1 as seen along the longitudinal direction (rotation axis direction) of the photosensitive drum 1. Incidentally, in Embodiment 1, the configuration and operation of the processing cartridge 88 for each color are substantially the same, except for the type (color) of the toner contained therein.

[0033] The rotational driving force of the drive motor 85 is transmitted from the drive output section (not shown) of the image forming apparatus 100 to the processing cartridge 88, and voltage (charging voltage, developing voltage, supply voltage, adjusting squeegee voltage, etc.) is supplied to the processing cartridge 88 from the contact point with the image forming apparatus 100. The drum unit 11 is provided with a photosensitive drum 1 and a charging roller 2 as a charging component.

[0034] The photosensitive drum 1 is a rotatable cylindrical photosensitive component, and a coupling member (not shown) is provided at one end in the longitudinal direction of the photosensitive drum 1 for transmitting driving force to the photosensitive drum 1. The coupling member engages with a drum drive coupling member on the image forming apparatus side, which is the drum drive output portion of the image forming apparatus 100, and the driving force of the drive motor 85 of the image forming apparatus 100 is transmitted to the photosensitive drum 1. The photosensitive drum 1 rotates about its axis in a first direction. Figure 3 Rotate in the direction of arrow R1 (counterclockwise). In Embodiment 1, at full speed, the photosensitive drum 1 is driven to rotate at a rotational speed that makes the speed (circumferential speed) of the outer peripheral surface of the photosensitive drum 1 148 mm / sec.

[0035] Furthermore, the surface of the photosensitive drum 1 is uniformly charged by the charging roller 2. In Embodiment 1, the charging roller 2 is a conductive roller with a conductive rubber layer provided on its core metal, deployed parallel to the photosensitive drum 1 and in contact with it at a predetermined pressure, and rotates following the rotation of the photosensitive drum 1. Furthermore, a charging voltage can be applied to the charging roller 2 from the charging voltage power supply 71. In Embodiment 1, for example, by applying a DC voltage of -1350V to the charging roller 2, the photosensitive drum 1 is charged, and the surface potential of the photosensitive drum 1 at this time becomes approximately -700V. It is set such that in Embodiment 1, after exposure, the surface potential (brightness potential) of the photosensitive drum 1 becomes -150V.

[0036] The developing apparatus 4 includes, for example, a toner 90 whose normal charging polarity (charging polarity for developing electrostatic latent images) is negative. At one end of the developing apparatus 4 in the longitudinal direction, a developing drive input gear (not shown) is provided for transmitting driving force to the developing apparatus 4. A developing input coupling portion (not shown) is provided to the developing drive input gear, which receives drive from a developing drive coupling member (not shown) on the image forming apparatus side of the image forming apparatus 100, and the driving force of the drive motor 85 of the image forming apparatus 100 is input to the developing apparatus 4. The developing apparatus 4 is provided with a rotatable developing roller 42 (developing member) as a developer carrying member, a rotatable supply roller 43 (supply member) as a developer supply member, and an adjusting blade 44 as a developer adjusting member. The aforementioned gear and coupling member are included in the drive transmission portion 80.

[0037] Toner 90 is supplied to the surface of developing roller 42 by supply roller 43. The thickness of the toner 90 held on developing roller 42 (hereinafter referred to as layer thickness) is adjusted by adjusting doctor blade 44, making it a thin layer. Here, adjusting doctor blade 44 functions to adjust the layer thickness of toner 90 on developing roller 42, and also functions as a developer charging member that applies a predetermined charge to the toner 90 on developing roller 42. The toner 90, now a thin layer, is conveyed to the contact portion with photosensitive drum 1 as developing roller 42 rotates, the toner 90 is applied to the surface of photosensitive drum 1, and the electrostatic latent image formed on photosensitive drum 1 is developed by the toner 90. Furthermore, toner 90 that is not supplied to the developing roller and remains on developing roller 42 is removed from developing roller 42 at the contact portion with supply roller 43. The removed toner 90 is then stirred and mixed with the toner 90 in developing apparatus 4.

[0038] The developing roller 42 is a roller having a conductive elastic rubber layer with a predetermined volume resistivity provided on the outer periphery of its metal core, and is configured such that its surface has a predetermined surface roughness. The developing roller 42 can be a single-layer roller or a roller with a multi-layer structure. As a single-layer roller, for example, a roller in which an elastic layer is formed on its core metal by a rubber material such as silicone rubber, polyurethane rubber, or epichlorohydrin rubber can be used. As a roller with a multi-layer structure, for example, a roller in which a surface layer is formed by applying silicone resin, polyurethane resin, polyamide resin, fluororesin, etc., to the surface of the elastic layer can be used.

[0039] The supply roller 43 is an elastic sponge roller with a conductive foamed member layer (hereinafter also referred to as the foamed member layer or foam layer) formed on the outer periphery of its metal core. On the surface of this foam layer, the foamed cell openings facilitate the retention and delivery of toner 90. The supply roller 43 is positioned to contact the developing roller 42 with a predetermined intrusion amount and forms a clamping portion N. In the clamping portion N, the developing roller 42 deforms the supply roller 43 into a concave shape. The supply roller 43, in the clamping portion N with respect to the developing roller 42, is positioned in a direction opposite to the rotation direction of the developing roller 42. Figure 3 The supply roller 43 rotates in the direction of arrow R3 and supplies toner 90 to the developing roller 42. In other words, the rotation direction (R3) of the supply roller 43 is the same as the rotation direction (R2) of the developing roller 42 (second direction) and opposite to the rotation direction (R1) of the photosensitive drum 1.

[0040] Furthermore, the supply roller 43 uses openings in its foam layer to scrape away toner 90 remaining on the developing roller 42 that was not used for developing the electrostatic latent image on the photosensitive drum 1, and returns the toner 90 to the interior of the developing container 41. The foam layer of the supply roller 43 deforms just before its clamping portion N with the developing roller 42, and the deformation causes the toner 90 remaining on the surface and inside the foam layer to be discharged into region X in the direction of arrow T1. As the deformation recovers through the foam layer on the surface of the supply roller 43 and past the clamping portion N, the toner 90 in region Y is absorbed in the direction of arrow T2.

[0041] In Example 1, the supply roller 43 uses a roller comprising a polyurethane foam layer and containing an ionic conductive agent. As an example, the supply roller 43 in Example 1 has a structure in which an ionic conductive agent, consisting of a salt of a cation and anion having reactive functional groups that react with isocyanate groups, is chemically bonded to the polyurethane foam layer via the aforementioned reactive functional groups. For example, a supply roller 43 having such a structure can be produced by foaming and curing a polyurethane composition containing an ionic conductive agent.

[0042] The driving force of the drive motor 85 input to the developing equipment 4 can be transmitted to the developing roller gear (not shown) to cause the developing roller 42 to rotate. Figure 3 Rotate in the direction of arrow R2. Furthermore, the driving force input to the drive motor 85 of the developing apparatus 4 can be transmitted to the supply roller gear (not shown) to cause the supply roller 43 to rotate in the direction of arrow R2. Figure 3Rotating in the direction of arrow R3. In Embodiment 1, in order to obtain appropriate image density, it is desirable that the moving speed of the surface of the developing roller 42 (hereinafter also referred to as the circumferential speed) be set to a ratio (hereinafter referred to as the circumferential speed ratio) between 1.2 and 1.5 times the moving speed of the surface of the photosensitive drum 1. In Embodiment 1, the developing roller 42 is set to a circumferential speed ratio of 1.4 for a balance between density and durability, and is rotated in the direction of arrow R2 at a moving speed that becomes 207 mm / sec at full speed.

[0043] Furthermore, to balance the supply of toner 90 to the developing roller 42 and the scraping of toner 90 from the developing roller 42, it is desirable that the supply roller 43 be set to 0.85 to 0.95 times the moving speed of the surface of the developing roller 42. In Embodiment 1, considering durability, its circumferential speed ratio is set to 0.9 times, and the supply roller 43 is rotated in the direction of arrow R3 at a speed that becomes 186 mm / sec at full speed.

[0044] The adjusting blade 44 includes an elastic member in the shape of a plate, possessing conductivity and flexibility. One end of the elastic member is fixed to the developing container (frame member) and cantilevered, leaving the other end free and in contact with the outer peripheral surface of the developing roller 42. Furthermore, the adjusting blade 44 is positioned downstream of the relative portion (contact portion) between the supply roller 43 and the developing roller 42 in the direction of movement (rotation) of the developing roller 42, thus contacting the outer peripheral surface of the developing roller 42. In Embodiment 1, SUS material is used as the elastic member of the adjusting blade 44. Additionally, in Embodiment 1, the adjusting blade 44 is positioned at the contact point with the developing roller 42 such that the tip of the free end of the elastic member is upstream (opposite direction) in the direction of movement facing the surface of the developing roller 42.

[0045] Furthermore, depending on the image forming operation, the developing voltage power supply 72, the supply voltage power supply 75, and the adjusting doctor blade voltage power supply 76 are respectively controlled (see...). Figure 2 A predetermined DC voltage is applied to the developing roller 42, the supply roller 43, and the adjusting doctor blade 44. In Example 1, during image formation, a DC voltage of -450V is applied to the developing roller 42, a DC voltage of -550V is applied to the supply roller 43, and a DC voltage of -550V is applied to the adjusting doctor blade 44. In Example 1, since the normal charging polarity of the toner 90 is negative, the potential difference between the supply roller 43 and the developing roller 42 becomes the polarity at which the toner 90 is pushed (moved) from the supply roller 43 side to the developing roller 42 side.

[0046] In Example 1, a non-magnetic toner with negative charge, manufactured by suspension polymerization, was used for toner 90. However, toner 90 is not limited to this and can be a toner manufactured, for example, by other polymerization methods such as pulverization and emulsion polymerization. Furthermore, the volume average particle size of toner 90 is preferably 5.0–8.0 μm. Here, the volume average particle size of toner 90 is measured using a Multisizer 3 precision particle size distribution measuring device manufactured by Beckman Coulter Inc. In Example 1, the volume average particle size of toner 90 is approximately 7.0 μm.

[0047] Furthermore, to improve fluidity, chargeability, and cleanliness, fluidizing agents or similar additives (hereinafter referred to as external additives) can be added to the toner 90. Examples of external additives include inorganic oxide particles composed of silica particles, alumina particles, titanium oxide particles, etc.; inorganic stearate compound particles such as aluminum stearate particles and zinc stearate particles; and inorganic titanate compound particles such as strontium titanate and zinc titanate. These external additives can be used alone or in combination of two or more. Preferably, these inorganic particles are treated with a gloss finish by using silane coupling agents, titanium coupling agents, higher fatty acids, silicone oils, etc., to improve heat storage resistance and environmental stability. Furthermore, the BET specific surface area of ​​the external additive is preferably 10 m². 2 / g or more and 450m 2 / g or less.

[0048] BET specific surface area can be measured using the BET method (preferably the BET multi-point method) through a low-temperature gas adsorption method with dynamic constant pressure. For example, the BET specific surface area (m²) can be calculated by adsorbing nitrogen gas onto the sample surface using a specific surface area measuring device (trade name: Gemini2375Ver.5.0, manufactured by Shimadzu Corporation) and measuring it using the BET multi-point method. 2 / g). The total amount of these various external additives is set to be more than 0.05 parts by mass and less than 5 parts by mass relative to 100 parts by mass of the colorant, or preferably more than 0.1 parts by mass and less than 3 parts by mass. Furthermore, various external additives can be combined and used.

[0049] Furthermore, a considerable amount of residual toner that has not yet been transferred by the intermediate transfer belt 53 remains on the photosensitive drum 1. In the image forming apparatus 100 of Embodiment 1, such residual toner is charged to a negative polarity by discharge from the charging roller 2, which is the normal polarity (normal charging polarity) of the toner 90. The charged residual toner rushes into the charging section, which serves as the contact portion between the charging roller 2 and the photosensitive drum 1. At this time, in the charging section, the residual toner is negatively charged due to the discharge through the charging roller 2, and passes through the charging section while remaining electrostatically on the photosensitive drum 1. Then, the residual toner that has passed through the charging section is moved to the developing section, which serves as the contact portion between the developing roller 42 and the photosensitive drum 1. In this developing section, when the surface of the photosensitive drum 1 with the residual toner is a non-image forming portion (dark potential forming area), the toner is recovered from the surface of the photosensitive drum 1 to the developing roller 42 due to the relationship between the potentials of the photosensitive drum 1 and the developing roller 42. In other words, the negatively polar residual toner is recovered through a potential difference of 350V between -700V, the dark potential of the photosensitive drum 1, and -350V, the developing voltage potential. A larger potential difference improves recyclability; however, the potential difference is determined taking into account latent image formation and developing performance during image formation. Furthermore, developer recyclability also varies depending on the difference in the moving speed of the surfaces of the photosensitive drum 1 and the developing roller 42 (hereinafter referred to as the surface moving speed difference), and a larger surface moving speed improves developer recyclability. On the other hand, when the surface of the photosensitive drum 1 with residual toner is the image forming area (the bright potential forming area), the residual toner continues to remain on the surface of the photosensitive drum 1 and is used as toner 90 to form an image.

[0050] The system that recovers residual toner via the developing roller 42 is a so-called cleaner-less type. Because the cleaner-less drum unit 11 has only a photosensitive drum 1 and a charging roller 2, the photosensitive drum 1 has a hollow internal structure and is lightweight, and the charging roller 2 rotates by following the rotation of the photosensitive drum 1, the load torque during rotational drive is extremely small. Therefore, in Embodiment 1, the drum unit 11 and the developing device 4 are driven by a drive motor 85 as the same drive source, and by minimizing the number of drive sources, the size of the image forming apparatus 100 is reduced.

[0051] <Configuration and Operation of Contact and Separation Mechanisms>

[0052] In Embodiment 1, to avoid unnecessary contact between the photosensitive drum 1 and the developing roller 42 during periods when image formation is not performed (hereinafter referred to as during non-image formation or during non-image formation), the following control is performed. Specifically, the control unit 202 uses the contact and separation mechanism 50 to control the presence or absence of contact between the photosensitive drum 1 and the developing roller 42 (developing contact and separation operation). During image formation, the developing roller 42 contacts the surface of the photosensitive drum 1 at contact position A (hereinafter referred to as developing contact), and during non-image formation periods (except during continuous image formation), it is moved to a separation position, which separates from the surface of the photosensitive drum 1 at a predetermined distance G (hereinafter referred to as developing separation). Incidentally, Figure 3 The illustration shows the developing separation state in which the developing roller 42 is moved to the separation position.

[0053] Next, the configuration and operation of the contact and separation mechanism 50, which is a moving part, will be described. The contact and separation mechanism 50 includes a rod 81, which serves as an action receiving part, provided to the developing apparatus 4, and a moving member 82, which serves as an action part, provided to the main assembly of the image forming apparatus 100. Furthermore, the developing apparatus 4 is connected to a frame member that fixes the position of the photosensitive drum 1 so that it can swing about a rotation axis approximately parallel to the rotation axis of the photosensitive drum 1. By operating the moving member 82 to move the rod 81, the developing apparatus 4 swings and moves between a contact position and a separation position.

[0054] The movement of the developing device 4 to the contact position is achieved by the spring force of a tension spring (not shown) and a rotational torque centered on the drive input of the developing device 4 during its operation. Here, the tension spring acts as a pushing component, with both ends attached to the frame member that fixes the position of the photosensitive drum 1 and the developing device 4. The moving member 82 of the contact and separation mechanism 50 is controlled by the control section 202. Figure 3 The developing device 4 moves in the direction of arrow P1, which is linked to the movement of lever 81, releasing it from the separated position. Then, through the spring force and rotational torque, the developing device 4 swings, and the developing roller 42 is moved to the side of the photosensitive drum 1. Thus, the developing device 4 can be moved to the contact position, and the developing roller 42 enters the contact state relative to the photosensitive drum 1.

[0055] Conversely, in order to move the developing device 4 to the separation position, the control unit 202 moves the moving member 82 of the contact and separation mechanism 50 away from the photosensitive drum 1 (in the direction of arrow P2), and moves the rod 81 in the same direction, so that the developing device 4 is held in the separation position. Thus, the developing device 4 can be moved to the separation position, and the developing roller 42 is brought into a separation state relative to the photosensitive drum 1. Incidentally, the movement of the moving member 82 is performed by receiving driving force from a motor or solenoid, which serves as a drive source, supplied to the image forming apparatus 100, via a drive transmission member.

[0056] In Embodiment 1, during image formation, the developing device 4 is deployed in the contact position, and the developing roller 42 is positioned in contact with the photosensitive drum 1. Furthermore, outside of image formation, such as in standby, sleep, and power-off states, the developing device 4 is deployed in the separation position, and the developing roller 42 is positioned separated from the photosensitive drum 1. Thus, by ensuring that the developing roller 42 only contacts the photosensitive drum 1 when necessary, deformation of the elastic developing roller 42 can be prevented, and its performance can be maintained for extended periods.

[0057] Figure 4 This includes timing diagrams of contact and separation in Example 1, as well as the circumferential velocity of each component. Figure 4 In the diagram, (i) shows the contact and separation (contact or separation) state t101 of the developing roller 42, and (ii) shows the speed of the drive motor 85 (drive motor speed t102) (full speed, low speed, stop). (iii) shows the moving speed of the surface of the photosensitive drum 1 (photosensitive drum speed t103) (full speed, low speed, stop), and (iv) shows the moving speed of the surface of the developing roller 42 (developing roller speed t104) (full speed, low speed, stop). (v) shows the moving speed of the surface of the supply roller 43 (supply roller speed t105) (full speed, low speed, stop). (vi) shows the developing voltage t113 (0V, -450V), and (vii) shows the supply voltage t114 (0V, -550V). In addition, “a” to “c” in t102 to t105, “a” and “c” in t113 and t114, t106 to t108, and t110 to t112 represent various time periods, and t109 represents a time period.

[0058] In Example 1, to prevent widthwise streak caused by developer contact during full-speed printing, which occurs over the rotation cycle of the supply roller 43 (hereinafter referred to as the supply roller cycle), the control unit 202 performs the following control. For example... Figure 4As shown in the timing diagram, after receiving the print signal at t106, the control unit 202 drives the drive motor speed t102 at a low speed (t102a) while the contact and separation t101 are in a separated state. As a result, the circumferential speeds of the photosensitive drum 1, the developing roller 42, and the supply roller 43 decrease uniformly. Therefore, at timing t107 when the developing roller 42 contacts, the photosensitive drum 1, the developing roller 42, and the supply roller 43 are all driven at a speed lower than during image formation at full speed. The circumferential speed of the photosensitive drum 1 is configured to be 49 mm / sec, the circumferential speed of the developing roller 42 to be 69 mm / sec, and the circumferential speed of the supply roller 43 to be 62 mm / sec.

[0059] (Regarding full-speed mode and low-speed mode)

[0060] The image forming apparatus 100 in Embodiment 1 can operate in multiple modes with different image forming speeds for performing image forming. The image forming apparatus 100 is configured to perform image forming in a low-speed mode when printing on thick paper or the like to improve fixing performance, and to perform image forming in a full-speed mode when printing on plain paper. In Embodiment 1, the low-speed mode corresponds to a first mode, which is the slowest image forming speed among multiple modes, and the full-speed mode corresponds to a second mode other than the first mode. When performing image forming in full-speed mode, from the developing separation state until the developing contact is complete, the control unit 202 performs rotational control of the photosensitive drum 1, the developing roller 42, and the supply roller 43 at this rotational speed of the low-speed mode.

[0061] On the other hand, when image formation is performed in low-speed mode, from the completion of development separation to the completion of development contact, and further until the completion of image formation, the control unit 202 is configured to perform rotational control of the photosensitive drum 1, the developing roller 42, and the supply roller 43 while maintaining the low-speed mode. Although described in detail below, it is important to reduce the absolute speed difference between the photosensitive drum 1 and the developing roller 42, and the absolute speed difference between the supply roller 43 and the developing roller 42, for transverse stripes in the supply roller cycle at the development contact. If each absolute speed difference has an effect on the transverse stripes in the supply roller cycle during image formation, the low-speed mode can be maintained from the completion of development separation to the completion of image formation. However, this is not the only option if a further effect on the transverse stripes in the supply roller cycle is desired; instead, the control unit 202 can control the rotation speed from development separation to the completion of development contact at a slower speed than the rotation speed during image formation in low-speed mode.

[0062] On the one hand, by rotating at a lower speed and performing developing contact, the absolute speed difference between the photosensitive drum 1 and the developing roller 42 becomes smaller, making it possible to achieve the effect of reducing transverse stripes during the supply roller cycle. However, when the photosensitive drum 1 or the developing roller 42 is in contact with the other while not rotating, the toner 90 on the developing roller 42 may become firmly fixed. Therefore, to prevent the toner from becoming firmly fixed, it is desirable to make the photosensitive drum 1 and the developing roller 42 contact each other while rotating. In Embodiment 1, the photosensitive drum 1 rotates at 1 mm / sec–88 mm / sec, the developing roller 42 rotates at 1.4 mm / sec–123 mm / sec, and the supply roller 43 rotates at 1.3 mm / sec–111 mm / sec, and developing contact is performed. As a result, an improvement in transverse stripes during the supply roller cycle can be confirmed. Incidentally, in this case, the absolute speed difference between the photosensitive drum 1 and the developing roller 42 is in the range of 0.4 mm / sec–35 mm / sec, and the absolute speed difference between the supply roller 43 and the developing roller 42 is in the range of 0.1 mm / sec–12 mm / sec. In Example 1, the circumferential speed ratio between the photosensitive drum 1 and the developing roller 42 at developing contact and the circumferential speed ratio between the developing roller 42 and the supply roller 43 are the same as the circumferential speed ratio during image formation, which are 1.4 times and 0.9 times, respectively.

[0063] In addition, after receiving the printing signal at t106, the control unit 202 drives the drive motor 85 at a low speed (t102a), and applies a voltage of -450V to the developing roller 42 (t113a) and a voltage of -550V to the supply roller 43 (t114a).

[0064] In this state, control unit 202 performs development contact at t107, and after development contact is completed (after t107), until the time when scanner unit 3 begins image exposure at t108, increases the speed of drive motor t102 to full speed (t102b). As a result, control unit 202 increases the circumferential speed of photosensitive drum 1 (t103b), developing roller 42 (t104b), and supply roller 43 (t105b) to the circumferential speed (full speed) used for image formation. Thereafter, control unit 202 begins image exposure at t108 and performs image formation during time period t109. After image exposure is completed at t110, by performing development separation at t111 and stopping drive motor 85 (t102c) after development separation, control unit 202 stops the rotation of photosensitive drum 1 (t103c), developing roller 42 (t104c), and supply roller 43 (t105c). Simultaneously, the control unit 202 stops applying voltage to the developing roller 42 (t113c) and the supply roller 43 (t114c), and terminates image formation at t112.

[0065] <Verification of the effect>

[0066] Image evaluation was performed using the image forming apparatus 100 and processing cartridge 88 as described in Example 1. Sensory evaluation was performed by printing a completely black image on A4-sized plain paper at 25°C / 50% RH. As a comparative example, in... Figure 5 The timing diagram in Comparison Example 1 is shown below. Incidentally, Figure 5 (i) to (vii) in Figure 4 (i) to (vii) correspond to each other, and t301 to t314 correspond to t101 to t114. In addition, “d” in t302 to t305, t313 and t314 indicates timing.

[0067] In Comparative Example 1, after receiving the print signal (t306), the control unit 202 drives the drive motor 85 at full speed (t302d). As a result, the control unit 202 drives the photosensitive drum 1 (t303d), the developing roller 42 (t304d), and the supply roller 43 (t305d) at full speed. Furthermore, after receiving the print signal (t306), the control unit 202 drives the drive motor 85 (t302d), applies a voltage of -450V to the developing roller 42 (t313d) and a voltage of -550V to the supply roller 43 (t314d), and performs developing contact (t307). Since the subsequent operations from the start of image exposure (t308) to the completion of image formation (t312) are the same as those in Example 1, their description will be omitted.

[0068] Table 1 shows the results of a sensory evaluation of the transverse stripes produced by the inventors during the supply roller cycle. The symbols A, B, C, and D in Table 1 (and Table 3, described later) represent: A: Excellent, B: Good, C: Acceptable, and D: Poor, respectively. In other words, in Table 1, C is better than D in the sensory evaluation, and A is better than B in the sensory evaluation (A>B>C>D).

[0069] [Table 1]

[0070] Example 1 Comparison Example 1 B D

[0071] As shown in Table 1, for the generation of transverse stripes during the supply roll cycle, the evaluation result in Example 1 is Grade B, which is superior to the Grade D result of Comparative Example 1. The reason will be explained using... Figure 6 and Figure 7 Describe it.

[0072] Figure 6Part (a) shows the state in which the photosensitive drum 1 and the developing roller 42 are rotated during development separation (within which a gap G is maintained). During development separation, the photosensitive drum 1 rotates at a circumferential speed of Vo, the developing roller 42 rotates at a circumferential speed of Vo, and the supply roller 43 rotates at a circumferential speed of Vr, and the order of the magnitudes of the circumferential speeds is Vd>Vr>Vo. Figure 6 Part (b) shows the state where the photosensitive drum 1 and the developing roller 42 have reached developing contact, and in order to achieve contact when the circumferential speed Vo of the photosensitive drum 1 is different from the circumferential speed Vd of the developing roller 42 (Vd>Vo), a braking effect, as indicated by arrow B, is generated on the surface of the developing roller 42. If the absolute velocity difference |Vo-Vd| between the circumferential speed Vo of the photosensitive drum 1 and the circumferential speed Vd of the developing roller 42 is large, then the kinetic energy increases, thus increasing the braking effect.

[0073] Furthermore, the circumferential speed of the supply roller 43, which has been rotated at Vr during development separation, is reduced due to the braking effect of the developing roller 42 upon development contact. As described above, the supply roller 43 repeatedly deforms and recovers the foamed layer as it contacts and rotates with the developing roller 42. Figure 6 In part (b), toner 90 is discharged towards region X in the T1 direction, and absorption of toner 90 is performed from region Y in the T2 direction. The greater the absolute velocity difference |Vr-Vd| between the circumferential velocity Vr of the supply roller 43 and the circumferential velocity Vd of the developing roller 42, the greater the kinetic energy, and therefore the greater the deformation and recovery of the foamed layer. If the circumferential velocity of the supply roller 43 is changed in a portion of the circumferential direction, the discharge and absorption of toner 90 at the location where the circumferential velocity has been changed, and an uneven portion U containing toner is generated on the circumferential surface of the supply roller 43. As a result, uneven frictional resistance is formed on the surface of the supply roller 43.

[0074] Figure 7 The torque data for the developing roller 42 are shown when toner 90, including an uneven portion U, is present on the circumferential surface of the supply roller 43. Figure 7 In the diagram, the horizontal axis represents time, and the vertical axis represents the torque of the developing roller 42. Furthermore, "▼" indicates the timing of the passage of the uneven portion U of the supply roller 43 through its contact portion with the developing roller 42. Figure 7 As shown in the graph, when the uneven portion U of the supply roller 43 passes through the contact portion with the developing roller 42, the torque of the developing roller 42 fluctuates due to the uneven frictional resistance. Because of this, the circumferential speed Vd of the developing roller 42 fluctuates after development contact, and transverse stripes are generated in the image according to the supply roller cycle. For the reasons described above, in Comparative Example 1, transverse stripes with a grade D in the sensory evaluation are generated according to the supply roller cycle.

[0075] On the other hand, in the configuration of Example 1, since the developing contact is performed under low-speed rotational drive, the absolute speed difference |Vo-Vd| between the circumferential speed Vo of the photosensitive drum 1 and the circumferential speed Vd of the developing roller 42 becomes smaller compared to the case of contact at full speed. Furthermore, compared to the case of contact at full speed, the absolute speed difference |Vr-Vd| between the circumferential speed Vr of the supply roller 43 and the circumferential speed Vd of the developing roller 42 also becomes smaller. Table 2 shows the values ​​of |Vo-Vd| and |Vr-Vd| in Example 1 and Comparative Example 1.

[0076] [Table 2]

[0077] Example 1 Comparison Example 1 |Vo-Vd| 20mm / sec 59mm / sec |Vr-Vd| 7mm / sec 21mm / sec

[0078] As described above, in Embodiment 1, the control unit 202 performs the following control. First, before forming an electrostatic latent image on the photosensitive drum 1 ( Figure 4 –t108) until the developing roller 42 moves from the separation position to the contact position via the contact and separation mechanism 50 ( Figure 4 The time period (-t107) is defined as the first time period. In the first time period, the circumferential speed of the photosensitive drum 1 is defined as Vo1, the circumferential speed of the developing roller 42 is defined as Vd1, and the circumferential speed of the supply roller 43 is defined as Vr1. Furthermore, in the first time period, the absolute value of the difference between the circumferential speed of the photosensitive drum 1 and the circumferential speed of the developing roller 42 is defined as |Vo1-Vd1|, and the absolute value of the difference between the circumferential speed of the developing roller 42 and the circumferential speed of the supply roller 43 is defined as |Vd1-Vr1|. Additionally, the time period during which an electrostatic latent image is formed on the photosensitive drum 1 ( Figure 4 The time interval (t108–t110) is defined as the second time period. During this second time period, the circumferential speed of the photosensitive drum 2 is defined as Vo2, the circumferential speed of the developing roller 42 is defined as Vd2, and the circumferential speed of the supply roller 43 is defined as Vr2. Furthermore, during the second time period, the absolute value of the difference between the circumferential speed of the photosensitive drum 1 and the circumferential speed of the developing roller 42 is defined as |Vo2 - Vd2|, and the absolute value of the difference between the circumferential speed of the developing roller 42 and the circumferential speed of the supply roller 43 is defined as |Vd2 - Vr2|. At this time, the control unit 202 controls the drive motor 85 to satisfy the following relationship:

[0079] |Vo1-Vd1|<|Vo2-Vd2|

[0080] |Vd1-Vr1|<|Vd2-Vr2|.

[0081] In other words, the control unit 202 controls the drive motor 85 to monotonically change the circumferential speed of the photosensitive drum 1 from Vo1 to Vo2, the circumferential speed of the developing roller 42 from Vd1 to Vd2, and the circumferential speed of the supply roller 43 from Vr1 to Vr2.

[0082] Furthermore, during the first time period, the ratio of the circumferential speed of the developing roller 42 to the circumferential speed of the photosensitive drum 1 is defined as Vd1 / Vo1, and the ratio of the circumferential speed of the supply roller 43 to the circumferential speed of the developing roller 42 is defined as Vr1 / Vd1. During the second time period, the ratio of the circumferential speed of the developing roller 42 to the circumferential speed of the photosensitive drum 1 is defined as Vd2 / Vo2, and the ratio of the circumferential speed of the supply roller 43 to the circumferential speed of the developing roller 42 is defined as Vr2 / Vd2. At this time, the control unit 202 controls the drive motor 85 to satisfy the following relationship:

[0083] Vd1 / Vo1=Vd2 / Vo2

[0084] Vr1 / Vd1=Vr2 / Vd2

[0085] Furthermore, regarding the mode, the control unit 202 controls the drive motor 85 so that during the first period of operation in full-speed mode, the circumferential speeds of the photosensitive drum 1, the developing roller 42, and the supply roller 43 are reduced to their low-speed circumferential speeds. The control unit 202 also controls the drive motor 85 to switch to full-speed mode during the second period. On the other hand, the control unit 202 also controls the drive motor 85 so that during the first period of operation in low-speed mode, the circumferential speeds of the photosensitive drum 1, the developing roller 42, and the supply roller 43 are reduced to their low-speed circumferential speeds, and this low-speed mode is maintained during the second period as well.

[0086] By reducing the absolute speed difference |Vo-Vd| between the circumferential speed Vo of the photosensitive drum 1 and the circumferential speed Vd of the developing roller 42 to perform the developing contact, the braking effect on the developing roller 42 during the developing contact becomes less. Furthermore, since the absolute speed difference |Vr-Vd| between the circumferential speed Vr of the supply roller 43 and the circumferential speed Vd of the developing roller 42 also decreases, the deformation and recovery of the foam layer of the supply roller 43 become less. Consequently, the unevenness of the toner 90 on the circumferential surface of the supply roller 43 becomes less, and torque fluctuations in the developing roller 42 are suppressed. Therefore, since the developing roller 42 can rotate stably even after the developing contact, in Embodiment 1, it achieves a grade B in the sensory evaluation, and the transverse stripes of the supply roller cycle are improved.

[0087] As described above, in a configuration where the photosensitive drum 1 and the developing roller 42 are separable and the developing apparatus 4 includes a supply roller 43 (which includes a foaming member in contact with the developing roller 42), the following effect can be achieved through the following configuration: In Embodiment 1, the absolute speed difference between the circumferential speed of the photosensitive drum 1 and the circumferential speed of the developing roller 42, and the absolute speed difference between the circumferential speed of the supply roller 43 and the circumferential speed of the developing roller 42, during developing contact, are configured to be less than the absolute speed difference during image formation. This makes it possible to improve lateral stripes during the supply roller cycle. With this configuration, it is not necessary to change the circumferential speed ratio of the photosensitive drum 1 to the developing roller 42 and / or the circumferential speed ratio of the developing roller 42 to the supply roller 43 during developing contact. Furthermore, in a configuration where the same drive motor 85 drives the photosensitive drum 1, the developing roller 42, and the supply roller 43, it is also possible to improve lateral stripes during the supply roller cycle.

[0088] As described above, according to Embodiment 1, in an image forming apparatus in which a photosensitive drum and a developing roller are provided to be contactable and separable from each other, it becomes possible to reduce the generation of transverse stripes during the rotation cycle of a supply roller that includes a foaming member in contact with the developing roller.

[0089] [Example 2]

[0090] In Embodiment 2, it controls the supply voltage applied to the supply roller 43 during developing contact as in Embodiment 1 and further improves the configuration of the transverse stripes of the supply roller cycle. Incidentally, descriptions of the same image forming apparatus 100, processing cartridge 88, and timing diagram as in Embodiment 1 will be omitted.

[0091] <Control of supply voltage at the developing contact>

[0092] Figure 8 A timing diagram from this embodiment is shown. Incidentally, Figure 8 (i) to (vii) in Figure 4 (i) to (vii) correspond to each other, and t201 to t214 and “a” to “c” correspond to each other. Figure 4 The numbers t101 to t114 and “a” to “c” correspond to each other. Incidentally, t214e indicates timing.

[0093] After receiving the print signal (t206), the control unit 202 drives the drive motor 85 at a low speed (t202a) in the developing separation state (t201). At this time, in Embodiment 2, the configuration control unit 202 applies a supply voltage to the supply roller 43 with the same value as the developing voltage (-450V) applied to the developing roller 42 (t214a). With the voltage applied to the supply roller 43 and the developing roller 42 set to the same state, the control unit 202 sets the circumferential speed of the photosensitive drum 1 (t203a), the developing roller 42 (t204a), and the supply roller 43 (t205a) to a low speed.

[0094] In this state, the developing contact is performed, and after the developing contact is completed (t207) and until the scanner unit 3 begins image exposure (t208), the control unit 202 increases the circumferential speed of the drive motor 85 to full speed (t202b). As a result, the control unit 202 increases the circumferential speeds of the photosensitive drum 1 (t203b), the developing roller 42 (t204b), and the supply roller 43 (t205b) to the circumferential speeds required for image formation. In addition, the control unit 202 also increases the supply voltage applied to the supply roller 43 to -550V (t214e). Thereafter, the control unit 202 begins image exposure (t208) and performs image formation (t209). Since the subsequent operations from the completion of image exposure (t210) to the completion of image formation (t212) are the same as those in Embodiment 1, their description will be omitted.

[0095] <Verification of the effect>

[0096] Image evaluation was performed using the image forming apparatus 100 and processing cartridge 88 from Example 2. Sensory evaluation was performed by printing a completely black image on A4-sized plain paper at 25°C / 50% RH. The results are shown in Table 3. Table 3 shows the results of a sensory evaluation of the transverse stripes during the supply roller cycle, conducted by the inventors.

[0097] [Table 3]

[0098] Example 2 Comparison Example 1 A D

[0099] As shown in Table 3, the evaluation result for the generation of transverse stripes during the supply roller cycle in Example 2 is Grade A, which is superior to Grade D in Comparative Example 1. The reasons for this will be described below.

[0100] Example 2 is a configuration in which the potential difference between the developing roller 42 and the supply roller 43 is the same during developing contact. Factors causing toner discharge from the supply roller 43 include deformation and recovery of the foaming member and the potential difference with the developing roller 42. With the configuration as in Example 2, it becomes possible to eliminate the discharge of toner 90 from the supply roller 43 to the developing roller 42 due to the potential difference. In other words, it becomes possible to suppress the amount of toner 90 discharged when the supply roller 43 experiences circumferential speed fluctuations. As a result, it becomes possible to reduce the toner-containing unevenness on the circumferential surface of the supply roller 43.

[0101] In this way, by setting the photosensitive drum 1 and the developing roller 42 to a low speed during the developing contact to reduce the absolute speed difference, and by setting the developing roller 42 and the supply roller 43 to the same potential, it becomes possible to suppress the unevenness of the toner-containing material in the supply roller 43 during the developing contact. Therefore, since it also becomes possible to make the developing roller 42 rotate stably after the developing contact, in Embodiment 2, it achieves grade A in sensory evaluation, and the transverse stripes of the supply roller cycle are improved. After the developing contact, by increasing the supply voltage to a voltage value that causes the toner 90 to move more easily from the supply roller 43 to the developing roller 42, it becomes possible to stably supply toner to the developing roller 42 during image formation.

[0102] Incidentally, in Embodiment 2, the developing roller 42 and the supply roller 43 are configured to be at the same potential during developing contact. However, the control unit 202 can control the developing voltage power supply 72 and the supply voltage power supply 75 such that the absolute value of the supply voltage (see Embodiment 1) is equal to or lower than the absolute value of the developing voltage during the first time period. In other words, a potential difference can be set to allow the toner 90 to move to the supply roller 43 side. For example, in Embodiment 2, if a toner 90 with negative charging properties is used, the following configuration can be made. Specifically, a voltage value higher than the voltage applied to the developing roller 42 can be applied to the supply roller 43 on the positive side until developing contact occurs, and after developing contact, the voltage can be increased to create a potential difference that makes it easier for the toner 90 to move from the supply roller 43 to the developing roller 42.

[0103] As described above, in a configuration where the photosensitive drum 1 and the developing roller 42 are separable and the developing apparatus 4 includes a supply roller 43 (which includes a foaming member in contact with the developing roller 42), the following configuration is made: The absolute speed difference between the circumferential speed of the photosensitive drum 1 and the circumferential speed of the developing roller 42 during developing contact is set to be less than the absolute speed difference during image formation, and the potential difference between the developing roller 42 and the supply roller 43 is set such that toner 90 does not move from the supply roller 43 to the developing roller 42. This reduces the toner-containing unevenness in the supply roller 43 during developing contact and improves lateral stripes during the supply roller cycle. With this configuration, it is also unnecessary to change the circumferential speed ratio of the photosensitive drum 1 to the developing roller 42 and / or the circumferential speed ratio of the developing roller 42 to the supply roller 43 during developing contact. Therefore, in a configuration where the same drive motor 85 drives the photosensitive drum 1, the developing roller 42, and the supply roller 43, it is also possible to improve lateral stripes during the supply roller cycle.

[0104] As described above, according to Embodiment 2, in an image forming apparatus in which a photosensitive drum and a developing roller are provided to be contactable and separable from each other, it becomes possible to reduce the generation of transverse stripes during the rotation cycle of a supply roller that includes a foaming member in contact with the developing roller.

[0105] <Other Embodiments>

[0106] The present invention can also be implemented by means of a program that implements one or more functions of the above embodiments being supplied to a system or device via a network or storage medium, and one or more processors in the computer of the system or device reading out and executing the processing of the program. Furthermore, the present invention can also be implemented by a circuit (e.g., an ASIC) that implements one or more functions.

[0107] The disclosure of this embodiment includes the following components.

[0108] (Component 1)

[0109] An image forming apparatus, comprising:

[0110] A rotatable image carrier component on which an electrostatic latent image is formed;

[0111] A rotatable developing member configured to supply developer to the image carrying member, develop the electrostatic latent image, and form a developer image;

[0112] A rotatable supply member configured to supply developer to the developing member by contacting the developing member;

[0113] The movable portion is configured to move the developing member to a contact position where the developing member contacts the surface of the image carrier member, or to a separation position where the developing member is separated from the surface of the image carrier member;

[0114] A driving source configured to drive the image carrier, the developing member, and the supply member; and

[0115] A control unit configured to control the moving part and the drive source.

[0116] During a first time interval in which the developing member moves from the separation position to the contact position by the moving part before the electrostatic latent image is formed on the image carrier member, when the circumferential velocity of the surface of the image carrier member is defined as Vo1, the circumferential velocity of the surface of the developing member is defined as Vd1, the circumferential velocity of the surface of the supply member is defined as Vr1, the absolute value of the difference between the circumferential velocity of the image carrier member and the circumferential velocity of the developing member is defined as |Vo1-Vd1|, and the absolute value of the difference between the circumferential velocity of the developing member and the circumferential velocity of the supply member is defined as |Vd1-Vr1|, and...

[0117] During the second time period when the electrostatic latent image is formed on the image carrier member, when the circumferential velocity of the surface of the image carrier member is defined as Vo2, the circumferential velocity of the surface of the developing member is defined as Vd2, the circumferential velocity of the surface of the supply member is defined as Vr2, the absolute value of the difference between the circumferential velocity of the image carrier member and the circumferential velocity of the developing member is defined as |Vo2-Vd2|, and the absolute value of the difference between the circumferential velocity of the developing member and the circumferential velocity of the supply member is defined as |Vd2-Vr2|,

[0118] The control unit controls the drive source.

[0119] In order to satisfy the following relationship,

[0120] |Vo1-Vd1|<|Vo2-Vd2|, and

[0121] |Vd1-Vr1|<|Vd2-Vr2|, and

[0122] In order to monotonically change the circumferential velocity of the surface that serves as the image-carrying component from Vo1 to Vo2,

[0123] The circumferential speed, which is the moving speed of the surface of the developing member, is monotonically changed from Vd1 to Vd2, and

[0124] The circumferential speed of the surface that serves as the supply component is monotonically changed from Vr1 to Vr2.

[0125] (Component 2)

[0126] According to the image forming apparatus of configuration 1, wherein, during the first time period, the ratio of the circumferential speed of the developing member to the circumferential speed of the image carrying member is defined as Vd1 / Vo1, and the ratio of the circumferential speed of the supply member to the circumferential speed of the developing member is defined as Vr1 / Vd1, and...

[0127] In the second time period, the ratio of the circumferential speed of the developing component to the circumferential speed of the image carrying component is defined as Vd2 / Vo2, and the ratio of the circumferential speed of the supply component to the circumferential speed of the developing component is defined as Vr2 / Vd2.

[0128] The control unit controls the drive source to satisfy the following relationship.

[0129] Vd1 / Vo1=Vd2 / Vo2, and

[0130] Vr1 / Vd1=Vr2 / Vd2.

[0131] (Component 3)

[0132] The image forming apparatus according to configuration 1 or configuration 2 further includes:

[0133] A developing voltage applying component, the developing voltage applying component being configured to apply a developing voltage to the developing member; and

[0134] A supply voltage application component is configured to apply a supply voltage to the supply member.

[0135] The control component controls the developing voltage application component and the supply voltage application component such that the absolute value of the supply voltage in the first time period is equal to or lower than the absolute value of the developing voltage in the first time period.

[0136] (Component 4)

[0137] The image forming apparatus according to any one of configurations 1 to 3 further includes:

[0138] A charging member configured to charge the image-bearing member prior to the formation of the electrostatic latent image; and

[0139] A transfer member configured to transfer the developer image onto a transferee member.

[0140] When the polarity of the developer is defined as normal polarity,

[0141] The charging component charges the developer remaining on the surface of the image-bearing component to its normal polarity after the developer image is transferred from the transfer component to the transferred component, and

[0142] The developing component recovers the developer that has been charged to the normal polarity by the charging component.

[0143] (Component 5)

[0144] According to any one of configurations 1 to 4, the image forming apparatus is capable of performing image forming in multiple modes with different image forming speeds, and

[0145] Wherein, when the first mode is the mode with the lowest image formation speed among the plurality of modes and the second mode is a mode other than the first mode,

[0146] The control unit controls the drive source such that, during the first time period when the second mode is executed, the circumferential speed of the image carrier member, the circumferential speed of the developing member, and the circumferential speed of the supply member become the circumferential speeds in the first mode, and during the first time period when the first mode is executed, the circumferential speed of the image carrier member, the circumferential speed of the developing member, and the circumferential speed of the supply member become the circumferential speeds in the first mode.

[0147] (Composition 6)

[0148] According to any one of configurations 1 to 5, the image forming apparatus wherein the image carrying member rotates in a first direction, and

[0149] The developing member and the supply member rotate in a second direction opposite to the first direction.

[0150] (Component 7)

[0151] According to any one of configurations 1 to 6, in an image forming apparatus, the control unit controls the drive source to satisfy the following relationship:

[0152] Vd1>Vr1>Vo1 or Vd2>Vr2>Vo2.

[0153] Although the invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the appended claims is to be given the broadest interpretation in order to cover all such modifications and equivalent structures and functions.

Claims

1. An image forming apparatus comprising: a rotatable image bearing member on which an electrostatic latent image is formed; a rotatable developing member configured to supply a developer to the image bearing member, develop the electrostatic latent image, and form a developer image; a rotatable supply member configured to supply the developer to the developing member by contacting the developing member; a moving portion configured to move the developing member to a contact position at which the developing member contacts a surface of the image bearing member, or a separation position at which the developing member is separated from the surface of the image bearing member; a drive source configured to drive the image bearing member, the developing member, and the supply member; and a control portion configured to control the moving portion and the drive source, wherein, in a first period in which the developing member is moved by the moving portion from the separation position to the contact position before the electrostatic latent image is formed on the image bearing member, when a peripheral speed as a moving speed of a surface of the image bearing member is defined as Vo1, a peripheral speed as a moving speed of a surface of the developing member is defined as Vd1, a peripheral speed as a moving speed of a surface of the supply member is defined as Vr1, an absolute value of a difference between the peripheral speed of the image bearing member and the peripheral speed of the developing member is defined as |Vo1-Vd1|, and an absolute value of a difference between the peripheral speed of the developing member and the peripheral speed of the supply member is defined as |Vd1-Vr1|, and in a second period in which the electrostatic latent image is formed on the image bearing member, when a peripheral speed as a moving speed of a surface of the image bearing member is defined as Vo2, a peripheral speed as a moving speed of a surface of the developing member is defined as Vd2, a peripheral speed as a moving speed of a surface of the supply member is defined as Vr2, an absolute value of a difference between the peripheral speed of the image bearing member and the peripheral speed of the developing member is defined as |Vo2-Vd2|, and an absolute value of a difference between the peripheral speed of the developing member and the peripheral speed of the supply member is defined as |Vd2-Vr2|, the control portion controls the drive source so as to satisfy the following relationships, |Vo1-Vd1| < |Vo2-Vd2|, and |Vd1-Vr1| < |Vd2-Vr2|, and so as to monotonously change the peripheral speed as the moving speed of the surface of the image bearing member from Vo1 to Vo2, monotonously change the peripheral speed as the moving speed of the surface of the developing member from Vd1 to Vd2, and monotonously change the peripheral speed as the moving speed of the surface of the supply member from Vr1 to Vr2. ​ 2. The image forming apparatus according to claim 1, wherein when a ratio of a circumferential speed of the developing member to a circumferential speed of the image bearing member in the first period is defined as Vd1 / Vo1 and a ratio of a circumferential speed of the supply member to a circumferential speed of the developing member is defined as Vr1 / Vd1, and when a ratio of a circumferential speed of the developing member to a circumferential speed of the image bearing member in the second period is defined as Vd2 / Vo2 and a ratio of a circumferential speed of the supply member to a circumferential speed of the developing member is defined as Vr2 / Vd2, the control member controls the driving source so as to satisfy the following relationship, Vd1 / Vo1 = Vd2 / Vo2, and Vr1 / Vd1 = Vr2 / Vd2.

3. The image forming apparatus according to claim 1, further comprising: a developing voltage applying member configured to apply a developing voltage to the developing member; and a supply voltage applying member configured to apply a supply voltage to the supply member, wherein the control member controls the developing voltage applying member and the supply voltage applying member so that an absolute value of the supply voltage in the first period is equal to or lower than an absolute value of the developing voltage in the first period.

4. The image forming apparatus according to claim 1, further comprising: a charging member configured to charge the image bearing member before the latent electrostatic image is formed; and a transfer member configured to transfer the developer image to a transferred member, wherein when a polarity of a developer is defined as a normal polarity, the charging member charges a developer remaining on a surface of the image bearing member after the developer image is transferred to the transferred member by the transfer member to the normal polarity, and the developing member recovers the developer charged to the normal polarity by the charging member. the image forming apparatus is capable of performing image formation in a plurality of modes having different image formation speeds, and wherein when a first mode is a mode having a lowest image formation speed among the plurality of modes and a second mode is a mode other than the first mode, 5. The image forming apparatus according to claim 1, wherein the control member controls the driving source so that, in the first period in a case where image formation is performed in the second mode, a circumferential speed of the image bearing member, a circumferential speed of the developing member, and a circumferential speed of the supply member become circumferential speeds in the first mode, and so that, in the first period in a case where image formation is performed in the first mode, the circumferential speed of the image bearing member, the circumferential speed of the developing member, and the circumferential speed of the supply member become the circumferential speeds in the first mode. the image bearing member rotates in a first direction, and wherein the developing member and the supply member rotate in a second direction opposite to the first direction.

6. The image forming apparatus of claim 1, wherein, the control member controls the driving source so as to satisfy the following relationship, Vd1 > Vr1 > Vo1 or Vd2 > Vr2 > Vo2.

7. The image forming apparatus of claim 1, wherein, ​ ​

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