Image forming apparatus

Abstract

To prevent the occurrence of fogging at the start of using a new developing device.SOLUTION: In an operation period A, a control unit controls a power supply unit so that a supply potential difference and a regulation potential difference have the same polarity as the polarity of the supply potential difference and the regulation potential difference in an image forming operation, and an absolute value is reduced or become zero. In an operation period B, the control unit controls the power supply unit so that the supply potential difference and a regulation potential difference have the same polarity as the polarity of the supply potential difference and the regulation potential difference in the operation period A, and the absolute value is increased. In transition from the operation period A to the operation period B, the control unit controls the power supply unit to change the regulation potential difference at a timing earlier than the timing when a surface of a developing roller located at a first position when the supply potential difference is changed reaches a second position without passing through a developing unit in accordance with the rotation of the developing roller.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an image forming apparatus, and more particularly, to an electrophotographic image forming apparatus that forms an image on a recording material.

Background Art

[0002] In an electrophotographic image forming apparatus, an electrostatic latent image formed on the surface of an image carrier is developed with a developer on a developer carrier to form an image. As a developing device, a contact developing system configuration in which the developer carrier performs a developing operation while in contact with the image carrier is known. A contact developing system developing device generally includes a developing roller as a developer carrier, a regulating blade as a developer regulating member, and a supply roller as a developer supply member. Toner as a developer is carried and conveyed by the supply roller and supplied to the surface of the developing roller at the contact portion between the supply roller and the developing roller. Then, the toner on the developing roller is charged by friction at the contact portion with the regulating blade and the thickness of the layer is regulated, and the electrostatic latent image formed on the surface of the photosensitive drum as the image carrier is developed at the contact portion with the photosensitive drum. Also, a configuration in which the regulating blade and the supply roller perform an image forming operation with a predetermined potential difference with respect to the developing roller is known. In such a developing device, a conductive regulating blade and supply roller are used, and a predetermined voltage is applied to each member, thereby providing a predetermined potential difference between the members and the developing roller. In this way, the supply of toner from the supply roller to the developing roller and the application of charged charges to the toner by the regulating blade are stabilized.

[0003] On the other hand, a configuration has also been proposed in which the potential difference between the regulating blade and the supply roller and the developing roller is switched to a different value than that used during the image forming operation (hereinafter referred to as "non-image forming"). For example, Patent Document 1 describes that during non-image forming, when the developing device is judged to be in a relatively new condition, the developing device is driven under conditions in which the potential difference between the regulating blade and the developing roller is set to zero or to a polarity in which the toner is biased from the developing roller side to the regulating blade side. This suppresses the adhesion of external additives to the regulating blade even when there is a large amount of new toner in the developing device that contains abundant external additives that are easily transferred to surrounding materials with the opposite polarity to the toner. Furthermore, Patent Document 1 also discloses a configuration in which, during non-image forming, when the developing device is judged to be in a relatively new condition, the potential difference between the supply roller and the developing roller is set to zero or to a polarity in which the toner is biased from the developing roller side to the supply roller side. In such a configuration, when a new developing device is first used, toner is quickly filled inside the foam material that makes up the supply roller, reducing the frictional force between the supply roller and the developing roller, and thus reducing stress on the toner. Therefore, external additives are less likely to migrate from the toner surface. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2005-134651 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, in image forming apparatuses that do not have a separation mechanism between the photosensitive drum and the developing roller, for example, in order to reduce costs, the photosensitive drum and the developing roller are always in contact when the developing roller is rotated. In such a configuration, in the conventional example described above, when a new developing apparatus is first used, toner may adhere to the non-image area of ​​the photosensitive drum surface (hereinafter referred to as "fogging"). Here, "when a new developing apparatus is first used" corresponds to the non-image forming period from when the unused developing apparatus is installed in the image forming apparatus until it is ready to perform image forming operations. Fogging occurs for reasons such as the following: In new developing apparatuses, lubricants are generally used to protect the surfaces of the developing roller and the supply roller. When a developing apparatus is first used, the lubricant is present on the surface of the developing roller and the supply roller until the toner held inside the developing apparatus reaches the developing roller, and is gradually replaced by toner. If the potential difference between the regulating blade and supply roller and the developing roller is not appropriately set according to the state on the developing roller from the start of use until the toner layer is stably formed on the developing roller, and if toner supply and the application of static charge are not controlled, the following problems will occur: namely, insufficient static charge will not be obtained, resulting in fogging. The conventional example described above was not intended to suppress fogging when a new developing device is first used, and therefore this point was not taken into consideration.

[0006] When fogging occurs during the initial use of a new developing machine, the following problems may arise in a cleanerless image forming machine, for example, one that does not have a cleaning means to remove and recover toner remaining on the photosensitive drum. Specifically, toner due to fogging may adhere to the charging roller, which is used as a charging means, potentially degrading its charging performance. Furthermore, if a cleaning means is present, fogging may result in unexpected toner consumption.

[0007] This invention was made under these circumstances and aims to suppress the occurrence of fogging when a new developing device is first used. [Means for solving the problem]

[0008] To solve the above-mentioned problems, the present invention has the following configuration. (1) An image forming apparatus for performing an image forming operation to form an image on a recording material, comprising: a photoreceptor that is rotatably mounted and on which an electrostatic latent image is formed on its surface; a developer carrier that is rotatably mounted and in contact with the photoreceptor to form a developing section and in the developing section to supply a developer charged to the photoreceptor with a normal charging polarity; a supply member that is rotatably mounted and in contact with the developer carrier to supply the developer to the developer carrier; and downstream and forward of a first position in the rotational direction of the developer carrier where the developer carrier and the supply member come into contact. A regulating member that contacts the developer carrier at a second position upstream of the developing unit and restricts the developer on the developer carrier; a power supply device that applies a first voltage to the developer carrier, a second voltage to the supply member, and a third voltage to the regulating member; and a photoreceptor, a developer carrier and the photoreceptor, in contact with each other during a period different from the image forming operation, with a surface potential difference such that an electric field is generated between the photoreceptor and the developer carrier, causing the developer, which is charged with the normal charging polarity, to move from the photoreceptor to the developer carrier. The system includes a control unit that controls the system to perform a first non-image forming operation, in which a supply member is rotated, a first voltage is applied from the power supply to the developer carrier, a second voltage is applied to the supply member, and a third voltage is applied to the regulating member, and a second non-image forming operation is performed following the first non-image forming operation, wherein in the first non-image forming operation, the first potential difference, which is the difference between the second voltage and the first voltage, and the second potential difference, which is the difference between the third voltage and the first voltage, are compared with the first potential difference in the image forming operation. The power supply is controlled so that the polarity of the first potential difference is the same as that of the second potential difference, and the absolute value is small or zero. In the second non-image forming operation, the power supply is controlled so that the first potential difference and the second potential difference are the same polarity as those of the first potential difference and the second potential difference in the first non-image forming operation, and the absolute value is large. When transitioning from the first non-image forming operation to the second non-image forming operation, the surface of the developer carrier that was located at the first position when the first potential difference was changed is...An image forming apparatus characterized by controlling the power supply device to change the second potential difference at a timing earlier than the timing at which the developer carrier reaches the second position without passing through the developing section due to rotation. [Effects of the Invention]

[0009] According to the present invention, it is possible to suppress the occurrence of fogging when a new developing device is first used. [Brief explanation of the drawing]

[0010] [Figure 1] Schematic diagram showing an example of the image forming apparatus in Examples 1 and 2. [Figure 2] Block diagram showing the control system of the image forming apparatus in Example 1. [Figure 3] Timing chart of the initial setup operation of the image forming apparatus in Example 1 [Figure 4] Timing chart of the initial setup operation of the image forming apparatus in Example 2 [Modes for carrying out the invention]

[0011] The embodiments for carrying out this invention will be described in detail below with reference to the drawings, based on examples. However, the dimensions, materials, shapes, and relative arrangements of the components described in these embodiments should be appropriately modified depending on the configuration of the device to which the invention is applied and various conditions. In other words, the scope of this invention is not intended to be limited to the following embodiments.

[0012] [Example 1] <Overview of an image forming apparatus> Referring to Figure 1, the overall configuration and image forming operation of the electrophotographic image forming apparatus (hereinafter referred to as the image forming apparatus) of Example 1 will be described. Figure 1 is a schematic cross-sectional view showing the general configuration of the image forming apparatus 100. In Example 1, four image forming stations (hereinafter referred to as image forming units) for yellow, magenta, cyan, and black are arranged side by side from left to right in the drawing. Each image forming unit is an electrophotographic image forming mechanism with a similar configuration to the others, except that the color of the developer (hereinafter referred to as the toner) 90 contained in their respective developing devices is different. In the following description, unless otherwise specified, the subscripts Y (yellow), M (magenta), C (cyan), and K (black), which are given to the reference numerals to indicate that an element is provided for one of the colors, will be omitted, and a general description will be given. Each image forming unit mainly consists of a photosensitive drum 1 which is a photosensitive element, a charging roller 2 which is a charging means, a developing device 4, a primary transfer device 51, etc. The exposure device 3 may be common to all image forming units, or it may be provided for each image forming unit.

[0013] In Example 1, the photosensitive drum 1, the charging roller 2, and the developing device 4 are integrated as a process cartridge 8 and are configured to be detachable from the main body of the image forming apparatus (the part of the image forming apparatus 100 excluding the process cartridge 8). However, the invention is not limited to this, and the process cartridge in the present invention may include at least the photosensitive drum 1 and the developing device 4, and be configured to be detachable from the main body of the apparatus as a whole. Alternatively, the developing device 4 may be configured to be detachable from the main body of the apparatus or the process cartridge 8 on its own. Furthermore, the photosensitive drum 1 and the developing device 4 may be fixed to the main body of the image forming apparatus, eliminating the need for user replacement.

[0014] The photosensitive drum 1 is a rotatable cylindrical photoreceptor that rotates around its axis in the direction of the arrow shown in the diagram (counterclockwise). In Embodiment 1, the outer surface of the photosensitive drum 1 is driven to rotate at a rotational speed of, for example, 180 mm / sec. 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 on a metal core, and is arranged in parallel with the photosensitive drum 1 in contact with it at a predetermined pressure, and rotates in conjunction with the rotation of the photosensitive drum 1. Furthermore, it is possible to apply a charging voltage, which is a fourth voltage, to the charging roller 2 from a power supply device 67, which is a power supply means. In Embodiment 1, the photosensitive drum 1 is charged by applying a DC voltage of, for example, -1150V to the charging roller 2, and the surface potential of the photosensitive drum 1 at that time is approximately -500V.

[0015] The exposure unit, exposure apparatus 3, acquires an image signal from the control unit 65 and scans the surface of the photosensitive drum 1 with laser light corresponding to the image signal. As a result, an electrostatic latent image corresponding to the image signal is formed on the charged surface of the photosensitive drum 1. The image signal is input to the control unit 65 upon request from the user, for example, from an image reading device (not shown) connected to the main body of the image forming apparatus, or from a host device (not shown), such as a personal computer, that is communicatively connected to the main body of the image forming apparatus. The control unit 65 can be, for example, an information processing device such as a control circuit equipped with computing resources such as a processor and memory.

[0016] The developing device 4 deposits toner 90, which is charged with the same polarity as the charging polarity of the photosensitive drum 1, onto the areas (image area, exposed area) on the surface of the photosensitive drum 1 where the charge has been attenuated by exposure, thereby forming a toner image, which is a developer image. In Example 1, the developing device 4 contains, for example, toner 90 as a non-magnetic one-component developer whose normal charging polarity (charging polarity for developing an electrostatic latent image) is negative. The developing device 4 is equipped with a rotatable developing roller 42 which is a developer carrier, a rotatable supply roller 43 which is a supply member, and a regulating blade 44 which is a regulating member. The developing roller 42 contacts the photosensitive drum 1 to form a developing section, and in the developing section, toner 90 charged with the normal charging polarity is supplied to the photosensitive drum 1.

[0017] Toner 90 is supplied to the surface of the developing roller 42 by the supply roller 43. The toner 90 held on the developing roller 42 (on the developer carrier) is then thinned by the regulating blade 44, which restricts the thickness of the layer (hereinafter referred to as the layer thickness), and is then used for development. Here, the regulating blade 44 has the function of restricting the layer thickness of the toner 90 on the developing roller 42, and also functions as a developer charging means that imparts a predetermined charge to the toner 90 on the developing roller 42.

[0018] The developing roller 42 has a conductive elastic rubber layer with a predetermined volume resistance on the outer circumference of a metal core, and its surface is further provided with a predetermined surface roughness. The developing roller 42 can be a single-layer roller or a multi-layer roller. For a single-layer roller, an elastic layer made of rubber material such as silicone rubber, urethane rubber, or hydrin rubber is formed on the metal core. For a multi-layer roller, a surface layer is formed by coating the surface of the elastic layer with silicone resin, urethane resin, polyamide resin, fluororesin, etc.

[0019] The developing roller 42 stops in a state of being separated from the photosensitive drum 1 by the contact-separation mechanism 70 (see FIG. 2). Note that the contact-separation mechanism 70 is a mechanism that causes the developing roller 42 to contact or separate from the photosensitive drum 1. The control unit 65 controls the contact-separation mechanism 70 so that the developing roller 42 contacts the photosensitive drum 1 in the image forming operation, the first non-image forming operation, and the second non-image forming operation described later. Further, the control unit 65 controls the developing clutch mechanism 49 (see FIG. 2) to rotationally drive the developing roller 42 in accordance with the timing when the developing roller 42 contacts the photosensitive drum 1 and stop the developing roller 42 in accordance with the timing when it separates. Here, the reason why the developing roller 42 is rotationally driven in a state of contacting the photosensitive drum 1 and stops when it becomes separated is to reduce the stress on the toner 90 accompanying the rotation of the developing roller 42 as much as possible. In the first embodiment, the developing roller 42 contacts the photosensitive drum 1 with a predetermined contact width by an urging means (not shown) in accordance with the drive in the image forming operation or the like, and is rotationally driven in the direction of the illustrated arrow (clockwise direction) in which the moving direction of the surface is the same at the facing position with the photosensitive drum 1. However, it is not limited to this, and any configuration in which the developing roller 42 is in a contact state with the photosensitive drum 1 when rotationally driven, for example, a configuration without the contact-separation mechanism 70 or the developing clutch mechanism 49 may be used. Also, in the first embodiment, in order to obtain an appropriate image density, the developing roller 42 is rotationally driven at a speed such that the moving speed of the surface of the developing roller 42 is, for example, 140% of the moving speed of the surface of the photosensitive drum 1.

[0020] The supply roller 43 is an elastic sponge roller having a conductive foam formed on the outer periphery of a metal core. The supply roller 43 is arranged to contact the developing roller 42 with a predetermined penetration amount. In Example 1, the supply roller 43 having a urethane foam layer and containing an ionic conductive agent was used. As an example, the supply roller 43 in Example 1 has a configuration in which an ionic conductive agent composed of a salt of a cation and an anion having a reactive functional group that reacts with an isocyanate group is chemically bonded to the urethane foam layer via the above-described reactive functional group. For example, the supply roller 43 having such a configuration can be manufactured by foaming and curing a urethane composition containing an ionic conductive agent.

[0021] The regulating blade 44 has a plate-like elastic member having conductivity and flexibility. One end of the elastic member is fixed to the developing container (frame body) and supported in a cantilever manner, and the other end is a free end and abuts on the circumferential surface of the developing roller 42. Further, the regulating blade 44 is arranged in contact with the circumferential surface of the developing roller 42 at a second position on the downstream side in the moving direction (rotation direction) of the surface of the developing roller 42 with respect to the facing portion (contact portion) (first position) between the supply roller 43 and the developing roller 42. In Example 1, a SUS material was used as the elastic member of the regulating blade 44. Further, in Example 1, the regulating blade 44 is provided such that the tip portion on the free end side of the elastic member faces the upstream side in the moving direction of the surface of the developing roller 42 (counter direction) at the contact position (second position) with the developing roller 42.

[0022] Furthermore, a predetermined DC voltage is applied from the power supply unit 67 to the developing roller 42, the supply roller 43, and the regulating blade 44 according to the image forming operation. In Example 1, a DC voltage of -300V is applied to the developing roller 42, -400V to the supply roller 43, and -400V to the regulating blade 44 according to the image forming operation. Since the normal charge polarity of the toner 90 in Example 1 is negative, the potential difference between the supply roller 43 and the developing roller 42 is such that the toner 90 is biased (moves) from the supply roller 43 side to the developing roller 42 side. This stabilizes the supply of toner 90 from the supply roller 43 to the developing roller 42. On the other hand, the potential difference between the regulating blade 44 and the developing roller 42 is such that the toner 90 is biased from the regulating blade 44 side to the developing roller 42 side. This stabilizes the intake of toner into the contact area between the regulating blade 44 and the developing roller 42, and also stabilizes the application of charge to the toner 90 by the regulating blade 44.

[0023] The toner image formed on the photosensitive drum 1 is electrostatically transferred to the transfer target, the intermediate transfer belt 53, by a primary transfer device 51, which is one of the transfer members. The toner images of each color are sequentially superimposed and transferred onto the intermediate transfer belt 53 to form a full-color toner image. The full-color toner image is then transferred to the recording material P by a secondary transfer device 52, which is a different transfer member from the primary transfer device 51. Subsequently, the unfixed toner image on the recording material P is fixed to the recording material P by a fixing device 6 through pressurization and heating, and the image is discharged outside the image forming apparatus 100 as an image formed product.

[0024] Furthermore, a belt cleaning device 7 is provided downstream of the secondary transfer device 52 in the direction of movement of the intermediate transfer belt 53 to remove and recover toner 90 remaining on the intermediate transfer belt 53. In Example 1, a cleanerless image carrier system is employed in which no dedicated cleaning device is provided for the photosensitive drum 1, and toner 90 remaining on the surface of the photosensitive drum 1 after primary transfer (hereinafter referred to as residual toner) is recovered by the developing device 4. That is, the surface of the photosensitive drum 1, after passing the position opposite the primary transfer device 51 (primary transfer position), does not come into contact with any other components until it reaches the contact position with the charging roller 2 (charging position). Therefore, during the image forming operation, residual toner after primary transfer that has passed the charging position on the photosensitive drum 1 is recovered by the developing roller 42 in contact with the photosensitive drum 1 and returned to the developing device 4. However, the effects of the present invention are not limited to the above configuration.

[0025] The power supply unit 67 can function as a developing voltage application unit, a supply voltage application unit, and a regulating voltage application unit. The developing voltage application unit applies a first voltage, the developing voltage, to the developing roller 42 included in the developing device 4. The supply voltage application unit applies a second voltage, the supply voltage, to the supply roller 43. The regulating voltage application unit applies a third voltage, the regulating voltage, to the regulating blade 44. However, it is not limited to this, and the power supply unit 67 may be provided separately as a charging power supply for the charging roller 2 and a developing power supply for the developing device 4. In that case, the charging power supply and the developing power supply may be considered together as a power supply means. Furthermore, the developing power supply for the developing roller 42, the supply power supply for the supply roller 43, and the regulating power supply for the regulating blade 44 may be separate. In that case, the charging power supply, developing power supply, supply power supply, and regulating power supply may be considered together as a power supply means. In addition, the power supply unit 67 may be used to apply voltage during toner image transfer, or a separate transfer power supply may be provided. In the first embodiment, the power supply 67 changes the voltage applied to each component according to the control of the control unit 65. Furthermore, the image forming apparatus 100 is not limited to the configuration shown in Figure 1, and may be configured such that, for example, the recording material P is the transfer target to which the toner image is directly transferred from the photosensitive drum 1.

[0026] <Haze control during initial setup operation> Next, the control of fogging during the initial setup operation in the image forming apparatus 100 of Example 1 will be described. Figure 2 is a block diagram showing the control system of the image forming apparatus 100 of Example 1. In Example 1, the power supply unit 67, under the control of the control unit 65, applies a developing voltage from the developing voltage application unit 62 to the developing roller 42, a supply voltage from the supply voltage application unit 63 to the supply roller 43, and a regulating voltage from the regulating voltage application unit 64 to the regulating blade 44. Here, the developing voltage application unit 62, the supply voltage application unit 63, and the regulating voltage application unit 64 are control mechanisms that supply the voltages necessary for their operation, and are configured as part of the power supply unit 67, but are not limited to this. The control unit 65 also transmits rotational driving force to the photosensitive drum 1, the developing roller 42, and the supply roller 43 by the drive motor 15, which is the drive unit, and drives them. However, it is not limited to this, and for example, a motor that transmits rotational driving force to the photosensitive drum 1 and a motor that transmits rotational driving force to the developing roller 42 and the supply roller 43 may be provided separately.

[0027] In the image forming apparatus 100 of Example 1, when a process cartridge 8 including a developing device 4 is mounted on the main body of the image forming apparatus 100, the control unit 65 determines whether the mounted process cartridge 8 (or developing device 4) is unused (new). Here, a predetermined known detection means can be used to determine whether the process cartridge 8 (or developing device 4) is unused (new). Based on the detection result of the known detection means, the control unit 65 determines whether the process cartridge 8 (or developing device 4) is unused (new). An example of a known detection means is memory. If the process cartridge 8 (or developing device 4) is unused, the control unit 65 performs an initial setup operation. On the other hand, if the process cartridge 8 (or developing device 4) is not unused, the control unit 65 performs a predetermined preparation operation and enters a standby state (READY state) where the image forming operation can be started.

[0028] <Initial installation operation> Figure 3 is a timing chart of the initial setup operation in the image forming apparatus 100 of Example 1. In Figure 3, (i) shows the charging voltage applied to the charging roller 2, (ii) shows the surface potential of the photosensitive drum 1, and (iii) shows the contact and separation (contact (drive), separation (stop)) between the developing roller 42 and the photosensitive drum 1. Figure 3(iv) shows the developing voltage applied to the developing roller 42, and (v) shows the supply voltage applied to the supply roller 43 and the regulating voltage applied to the regulating blade 44. In all cases, the horizontal axis represents time, and t1 to t4 represent the respective timings.

[0029] In Example 1, when the initial setup operation starts at timing t1, the photosensitive drum 1 is rotated, and a DC voltage of -1150V is applied to the charging roller 2, so that the surface of the photosensitive drum 1 is charged and the surface potential becomes -500V. The developing roller 42 and the supply roller 43 are also rotated, and the developing roller 42 comes into contact with the photosensitive drum 1 at a predetermined contact width by a biasing means (not shown). At timing t1, a DC voltage of -300V is applied to the developing roller 42, and a DC voltage of -350V is applied to the supply roller 43 and the regulating blade 44.

[0030] In Embodiment 1, the initial setup operation has two operating periods, A and B. During these periods, the control unit 65 rotates the photosensitive drum 1, the developing roller 42, and the supply roller 43. At this time, the control unit 65 rotates the photosensitive drum 1 and the developing roller 42 in a state where they are in contact with each other, with a surface potential difference that generates an electric field that moves the toner 90, which is charged with the normal charging polarity, from the photosensitive drum 1 to the developing roller 42. Operating period A, in which the first non-image forming operation is performed, is the period from timing t1 to timing t2, and operating period B, in which the second non-image forming operation is performed, is the period from timing t2 to timing t3. The control unit 65 sets the potential difference between the supply roller 43 and the developing roller 42 (hereinafter referred to as the supply potential difference) and the potential difference between the regulating blade 44 and the developing roller 42 (hereinafter referred to as the regulating potential difference) for each operating period. Here, the supply potential difference is set to supply potential difference V1A in operating period A and to supply potential difference V1B in operating period B. Furthermore, the regulated potential difference is set to V2A during operating period A and to V2B during operating period B. In addition, Example 1 specifies the timing for changing the supply potential difference and the regulated potential difference when transitioning from operating period A to operating period B. That is, timing t2 is the change timing. At timing t2, the supply voltage and the regulated voltage are changed from -350V to -400V, thereby changing (switching) the supply potential difference and the regulated potential difference. The following describes in detail the issues (occurrence of fouling) in each operating period and the fouling control, which is a feature of the present invention.

[0031] (Operating period A) Operating period A is the period from timing t1, when the initial setup operation begins, to timing t2, when the supply potential difference and regulated potential difference are switched. During operating period A, the developing device 4 starts operating from an unused state, and the toner 90 contained within the developing device 4 begins to be supplied from the supply roller 43 to the surface of the developing roller 42 while filling the foam layer inside the supply roller 43. In Example 1, in the unused state of the developing device 4, a predetermined amount of lubricant is applied to the surfaces of the developing roller 42 and the supply roller 43 in order to protect the surface of the components and reduce the torque at the start of operation. That is, lubricant is mainly present on the developing roller 42 until a certain period of time has elapsed since the start of operation of the developing device 4, and as the operating time of the developing device 4 progresses, the lubricant is gradually replaced by the toner 90. In Example 1, the same type of Y (yellow) toner contained within the developing device 4Y was used as the lubricant. However, it is not limited to this. As a lubricant, any particles that satisfy the required characteristics of a lubricant may be used, for example, spherical cross-linked fine particles of polyurethane resin. Here, the required properties of the lubricant include, for example, that it does not react with any of the components such as the developing roller 42 or the supply roller 43, and that its adhesion to the developing roller 42 is not too high. Note that the material, shape, charge amount, and application amount of the lubricant are not limited to those of Example 1, but should be appropriately selected according to the various configurations.

[0032] Since the lubricant is repeatedly used in the coating machine during the assembly of the developing device 4, the Y toner used as a lubricant in Example 1 may have inferior charging performance compared to the Y toner 90Y contained in the developing device 4Y. Therefore, if a large amount of lubricant is present on the developing roller 42, it may adhere to the non-image areas of the surface of the photosensitive drum 1 at the contact point with the surface of the photosensitive drum 1, causing fogging. In Example 1, toner was used as a lubricant, but a similar tendency can be observed even if, for example, the polyurethane resin particles mentioned above are used.

[0033] (Operating period B) Operating period B is the period from the timing t2 when the supply potential difference and regulating potential difference switch, to the timing t3 when the initial setup operation is completed. During operating period B, toner 90 is sufficiently filled inside the foam layer of the supply roller 43, and toner 90 is actively supplied from the supply roller 43 to the surface of the developing roller 42. This stably forms a toner 90 layer on the developing roller 42, preparing it for image formation operation. Therefore, because the amount of toner 90 on the developing roller 42 increases, if the amount of charge applied by the regulating blade 44 is insufficient, toner 90 will be generated that does not receive a sufficient amount of charge. As a result, fogging is more likely to occur in the non-image areas of the surface of the photosensitive drum 1 at the contact point with the surface of the photosensitive drum 1. When fogging occurs in this way, in an image forming apparatus that does not have a dedicated cleaning device for the photosensitive drum 1, such as in Example 1, the fogging may adhere to the charging roller 2, degrading its charging performance.

[0034] (Voltage control in Example 1) In Example 1, the occurrence of fogging is suppressed by controlling the voltage applied to the developing roller 42, supply roller 43, and regulating blade 44 during the initial setup operation as follows. First, the control unit 65 controls the supply potential difference V1A and regulating potential difference V2A during the operation period A to be zero, or to have the same polarity as the supply potential difference and regulating potential difference during the image forming operation, and to have a small absolute value. This suppresses the supply of lubricant from the supply roller 43 to the surface of the developing roller 42, and also suppresses the intake of lubricant to the contact area between the regulating blade 44 and the developing roller 42. As a result, during the operation period A, the amount of lubricant on the developing roller 42 that is carried and transported to the contact area with the surface of the photosensitive drum 1 is reduced, thereby suppressing the occurrence of fogging.

[0035] Next, the control unit 65 controls the supply potential difference V1B and the regulating potential difference V2B during the operating period B to have the same polarity as the supply potential difference and regulating potential difference during the image forming operation, and to have a larger absolute value than the supply potential difference V1A and the regulating potential difference V2A. This allows for the active supply of toner 90 from the supply roller 43 to the surface of the developing roller 42, stably forming a toner 90 layer on the developing roller 42, while also allowing sufficient charge to be imparted to the toner 90 by the regulating blade 44. As a result, the toner 90 layer on the developing roller 42 can be sufficiently charged, and the occurrence of fogging can be suppressed.

[0036] Furthermore, in Example 1, the timing is controlled as follows when transitioning from operating period A to operating period B. Specifically, the control unit 65 changes the regulating potential difference from V2A to V2B at an earlier timing than when the surface of the developing roller 42, where the supply potential difference has been changed from V1A to V1B, reaches the contact position with the regulating blade 44 due to the rotation of the developing roller 42. This reliably prevents insufficient application of static charge by the regulating blade 44 in areas where the amount of toner 90 on the developing roller 42 increases when transitioning from operating period A to operating period B, thereby suppressing the occurrence of fogging.

[0037] In Example 1, as shown in Figure 3, during operating period A, a DC voltage of -300V is applied to the developing roller 42, and a DC voltage of -350V is applied to the supply roller 43 and the regulating blade 44, respectively. During operating period B, a DC voltage of -300V is applied to the developing roller 42, and a DC voltage of -400V is applied to the supply roller 43 and the regulating blade 44, respectively. That is, during operating period A, both the supply potential difference V1A and the regulating potential difference V2A are -50V, and during operating period B, both the supply potential difference V1B and the regulating potential difference V2B are -100V. When transitioning from operating period A to operating period B, the control is such that both the supply potential difference and the regulating potential difference are changed.

[0038] In Example 1, the developing voltage applied to the developing roller 42 was fixed at -300V, and when transitioning from operating period A to operating period B, the voltages applied to the supply roller 43 and the regulating blade 44 (supply voltage and regulating voltage) were changed to alter the supply potential difference and regulating potential difference, respectively. However, the method is not limited to this. For example, the voltages applied to the supply roller 43 and the regulating blade 44 may be fixed while the voltage applied to the developing roller 42 is changed, or each may be changed separately. Also, in Example 1, the supply potential difference V1A and regulating potential difference V2A in operating period A, and the supply potential difference V1B and regulating potential difference V2B in operating period B were set to the same potential, but the method is not limited to this.

[0039] The operating periods A and B during the initial setup operation are set appropriately based on the time required for the lubricant on the developing roller 42 to be replaced by toner 90 and the time required for the toner 90 layer on the developing roller 42 to be stably formed and for the image formation operation to be possible. In Example 1, operating period A was set to 8 seconds, for example, and operating period B was set to 42 seconds. After performing the initial setup operation as described above, the post-rotation process (print completion operation) that is normally performed after the image formation operation is completed is performed from timing t3, and at timing t4, the machine enters a standby state (READY state) where the image formation operation can be started.

[0040] In Embodiment 1, the control unit 65 controls the operation period A and the operation period B, which is executed following operation period A, to be performed at different times than the image forming operation. During operation period A, the control unit 65 controls the power supply unit 67 so that the first potential difference, the supply potential difference, and the second potential difference, the regulated potential difference, have the same polarity as the supply potential difference and regulated potential difference in the image forming operation, and their absolute values ​​are small. Alternatively, during operation period A, the control unit 65 controls the power supply unit 67 so that the supply potential difference and regulated potential difference are zero. During operation period B, the control unit 65 controls the power supply unit 67 so that the supply potential difference and regulated potential difference have the same polarity as the supply potential difference and regulated potential difference in operation period A, and their absolute values ​​are large. The control unit 65 executes the operations during operation period A and operation period B when it determines, based on the detection means described above, that the developing device 4 (process cartridge 8) is new. Furthermore, during the image forming operation, the control unit 65 controls the power supply unit 67 so that the supply potential difference is polarity such that toner 90 charged with the normal charging polarity moves from the supply roller 43 to the developing roller 42. Also, during the image forming operation, the control unit 65 controls the power supply unit 67 so that the regulated potential difference is polarity such that toner 90 charged with the normal charging polarity moves from the regulating blade 44 to the developing roller 42.

[0041] When transitioning from operating period A to operating period B, the control unit 65 performs the following timing control. Specifically, the control unit 65 controls the power supply unit 67 to change the regulated potential difference at an earlier timing than when the surface of the developing roller 42, which was in the first position described above when the supply potential difference is changed, reaches the second position described above due to the rotation of the developing roller 42.

[0042] In Example 1, it was assumed that a predetermined amount of lubricant was applied to the surfaces of the unused developing roller 42 and supply roller 43, but this is not the only possible solution. For example, the predetermined amount of lubricant may be applied to only one of the developing roller 42 or the supply roller 43, or neither may have lubricant applied.

[0043] [Comparative Example 1] Comparative Example 1 will now be described. The basic configuration and operation of the image forming apparatus 100 in Comparative Example 1 are the same as those in Example 1. Therefore, elements having the same or corresponding functions or configurations as those in the image forming apparatus 100 of Example 1 are denoted by the same reference numerals as in Example 1, and detailed explanations are omitted. In Comparative Example 1, the supply potential difference and regulating potential difference during the initial setup operation are fixed to constant values. That is, the voltages applied to the developing roller 42, the supply roller 43, and the regulating blade 44 are fixed to constant values ​​throughout the initial setup operation.

[0044] [Comparative Example 2] Comparative Example 2 will now be described. The basic configuration and operation of the image forming apparatus 100 in Comparative Example 2 are the same as those in Example 1. Therefore, elements having the same or corresponding functions or configurations as those in the image forming apparatus 100 of Example 1 are denoted by the same reference numerals as in Example 1, and detailed explanations are omitted. In Comparative Example 2, either the supply potential difference or the regulating potential difference during the initial setup operation is fixed to a constant value, while the other is changed during operating periods A and B. In Comparative Example 2, the voltage applied to the developing roller 42 is fixed, and the voltage applied to the supply roller 43 and the regulating blade 44 is changed to alter the supply potential difference or the regulating potential difference during operating periods A and B.

[0045] [Comparative Example 3] Comparative Example 3 will now be described. The basic configuration and operation of the image forming apparatus 100 in Comparative Example 3 are the same as those of Example 1. Therefore, elements having the same or corresponding functions or configurations as those of the image forming apparatus 100 in Example 1 are denoted by the same reference numerals as in Example 1, and detailed explanations are omitted. In Comparative Example 3, as in Example 1, the supply potential difference and regulated potential difference during the initial setup operation were changed in operating periods A and B. However, the difference is that when transitioning from operating period A to operating period B, the regulated potential difference is changed from V2A to V2B at the timing after the surface of the developing roller 42, where the supply potential difference has been changed from V1A to V1B, has passed the contact position with the regulated blade 44.

[0046] [Example 2] The following describes Example 2. The basic configuration and operation of the image forming apparatus 100 in Example 2 are the same as those in Example 1. Therefore, elements having the same or corresponding functions or configurations as those in the image forming apparatus 100 of Example 1 are denoted by the same reference numerals as in Example 1, and detailed descriptions are omitted.

[0047] Figure 4 is a timing chart of the initial setup operation in the image forming apparatus 100 of Example 2. Since (i) to (v) and t1 to t4 are the same as the chart in Figure 3, their explanation is omitted. Figure 4(vi) shows the rotational speed (stop, 35% speed, etc.) of the developing roller 42 and the supply roller 43. Here, the rotational speed of the developing roller 42 and the supply roller 43 is set to 100% during the image forming operation.

[0048] In Embodiment 2, the control unit 65 controls the rotation speed of the developing roller 42 and the supply roller 43 during operation period A to be slower than the rotation speed during image formation (100%) (for example, 35%). Furthermore, the rotation speed of the developing roller 42 and the supply roller 43 during operation period B is controlled to be faster than the rotation speed during operation period A. In Embodiment 2, the rotation speed of the developing roller 42 and the supply roller 43 during operation period A is driven at a rotation speed that is 35% of the rotation speed during image formation. Also, the rotation speed of the developing roller 42 and the supply roller 43 during operation period B is the same as the rotation speed during image formation.

[0049] As a result, the amount of lubricant discharged from the foam layer of the supply roller 43 at the contact point between the supply roller 43 and the developing roller 42 is reduced, thereby reducing the supply of lubricant from the supply roller 43 to the surface of the developing roller 42. Therefore, it is possible to reduce the occurrence of fogging on the non-image area of ​​the surface of the photosensitive drum 1 during operating period A. In Example 2, operating period A was set to 18 seconds, for example, and operating period B was set to 42 seconds, for example.

[0050] In Embodiment 2, in addition to the control described in Embodiment 1, the control unit 65 controls the drive motor 15 so that the rotational speed of the developing roller 42 and the supply roller 43 during operating period A is slower than the rotational speed of the developing roller 42 and the supply roller 43 during the image forming operation. More specifically, the control unit 65 controls the drive motor 15 so that the rotational speed of the developing roller 42 and the supply roller 43 during operating period A is slower than the rotational speed of the developing roller 42 and the supply roller 43 during operating period B. Furthermore, the control unit 65 controls the drive motor 15 so that the rotational speed of the developing roller 42 and the supply roller 43 during operating period B is the same as the rotational speed of the developing roller 42 and the supply roller 43 during the image forming operation.

[0051] [Verification of the effects of the present invention] <Details of Examples 1 and 2 and Comparative Examples 1-3> Examples 1 and 2, and Comparative Examples 1 (1-1, 1-2), 2 (2-1 to 2-3), and 3 (3-1 to 3-3) are shown in detail in Table 1. In Table 1, the second to fourth columns show the set values ​​for the supply potential difference V1A, the regulated potential difference V2A, and the rotation speeds of the developing roller 42 and supply roller 43 during operating period A. The fifth to seventh columns show the set values ​​for the supply potential difference V1B, the regulated potential difference V2B, and the rotation speeds of the developing roller 42 and supply roller 43 during operating period B. The eighth column shows whether or not timing control for the change in the supply potential difference and regulated potential difference was implemented when transitioning from operating period A to operating period B (timing t2). The ninth column shows the image evaluation results (○, ◎, ×). [Table 1]

[0052] (Settings for Example 1 and Example 2) For Example 1, the settings described in Figure 3 were used. For Example 2, the settings described in Figure 4 were used. In Example 1, during operating period A, the rotation speeds of the developing roller 42 and the supply roller 43 were set to the rotation speed during image formation (100%).

[0053] (Settings for Comparative Examples 1-1 and 1-2) In Comparative Example 1-1, both the supply potential difference V1A and V1B were set to -100V, and both the regulated potential difference V2A and V2B were set to -100V. The rotation speed of the developing roller 42 and the supply roller 43 was set to the rotation speed during image formation (100%) for both operating periods A and B. In Comparative Example 1-2, both the supply potential difference V1A and V1B were set to -50V, and both the regulated potential difference V2A and V2B were set to -50V. The rotation speed of the developing roller 42 and the supply roller 43 was set to the rotation speed during image formation (100%) for both operating periods A and B. In other words, in Comparative Examples 1-1 and 1-2, no switching of the supply potential difference and regulated potential difference was performed at timing t2.

[0054] (Settings for Comparative Examples 2-1, 2-2, and 2-3) In Comparative Example 2-1, the supply potential difference V1A was set to -50V, and the supply potential difference V1B was changed to -100V at timing t2. The regulated potential differences V2A and V2B were set to -100V for both operating periods A and B, and the rotation speed of the developing roller 42 and the supply roller 43 was set to the rotation speed during image formation (100%) for both operating periods A and B. In Comparative Example 2-2, the regulated potential difference V2A was set to -50V, and the regulated potential difference V2B was changed to -100V at timing t2. The supply potential differences V1A and V1B were set to -100V for both operating periods A and B, and the rotation speed of the developing roller 42 and the supply roller 43 was set to the rotation speed during image formation (100%) for both operating periods A and B. In Comparative Example 2-3, the supply potential difference V1A was set to -50V, and the supply potential difference V1B was changed to -100V at timing t2. Furthermore, the regulated potential differences V2A and V2B were set to -50V for both operating periods A and B, and the rotational speed of the developing roller 42 and the supply roller 43 was set to the rotational speed during image formation (100%) for both operating periods A and B. In other words, in comparative examples 2-1 to 2-3, at timing t2, only one of the supply potential difference or the regulated potential difference was switched.

[0055] (Settings for Comparative Examples 3-1, 3-2, and 3-3) In Comparative Example 3-1, the supply potential difference V1A and regulated potential difference V2A were set to -50V, and the supply potential difference V1B and regulated potential difference V2B were changed to -100V. The rotation speed of the developing roller 42 and the supply roller 43 was set to the rotation speed during image formation (100%) for both operating periods A and B. In Comparative Example 3-2, the supply potential difference V1A and regulated potential difference V2A were set to 0V, and the supply potential difference V1B and regulated potential difference V2B were changed to -100V. The rotation speed of the developing roller 42 and the supply roller 43 was set to the rotation speed during image formation (100%) for both operating periods A and B. In Comparative Example 3-3, the supply potential difference V1A and regulated potential difference V2A were set to +100V, and the supply potential difference V1B and regulated potential difference V2B were changed to -100V. The rotational speeds of the developing roller 42 and the supply roller 43 were set to the rotational speed during image formation (100%) for both operating periods A and B. In comparative examples 3-1 to 3-3, both the supply potential difference and the regulating potential difference were changed between operating period A and operating period B. However, the regulating potential difference was changed from V2A to V2B at the timing after the surface of the developing roller 42, whose supply potential difference had been changed from V1A to V1B, had passed the contact position with the regulating blade 44.

[0056] <Evaluation Method> This section describes the evaluation method for contamination of the charging roller 2 (hereinafter referred to as "charging roller 2 contamination") performed to confirm the effectiveness of the present invention. If fouling adheres to the charging roller 2, it degrades the charging performance, and if uneven adhesion occurs, charging unevenness occurs, for example, density unevenness occurs when forming intermediate grayscale images. In the evaluation of charging roller 2 contamination in the effectiveness verification, horizontal streaks in the output image when forming intermediate grayscale images were judged and evaluated visually according to the following criteria. If horizontal streaks were significantly present in the output image and posed a problem in actual use, it was marked with ×; if there were slight horizontal streaks but no problem in actual use, it was marked with ○; and if no horizontal streaks occurred, it was marked with ◎. The evaluation of charging roller 2 contamination was performed in an environment of 23°C and 50% relative humidity, and intermediate grayscale images were output after the initial setup operation in each example and comparative example.

[0057] <Comparison of Examples 1 and 2 with Comparative Examples 1-3> (Rating 1) First, we compare Example 1 with Comparative Examples 1-1, 2-1, and 2-2. In Example 1 and Comparative Examples 1-1, 2-1, and 2-2, the setting value for operating period B is the same, but the supply potential difference and regulated potential difference during operating period A differ between Example 1 and each of the comparative examples. In the three comparative examples, horizontal streaks occurred due to contamination of the charging roller 2. This is because, during operating period A, the supply potential difference and regulated potential difference were not controlled to have a smaller absolute value than those during the image forming operation. As a result, the supply of lubricant from the supply roller 43 to the surface of the developing roller 42 and the intake of lubricant at the contact point between the regulating blade 44 and the developing roller 42 increased, causing fouling.

[0058] (Rating 2) Next, we compare Example 1 with Comparative Examples 1-2 and 2-3. In Example 1 and Comparative Examples 1-2 and 2-3, the setting value for operating period A is the same, but the supply potential difference and regulated potential difference in operating period B differ between Example 1 and each comparative example. In two comparative examples, horizontal streaks occurred due to contamination of the charging roller 2. This is because the regulated potential difference in operating period B was not controlled to have a larger absolute value than that in operating period A. As a result, the regulated blade 44 did not adequately impart charge to the toner 90, causing fogging. In addition, in Comparative Example 1-2, it took a long time for the toner 90 layer on the developing roller 42 to be stably formed in operating period B. This is because the absolute value of the supply potential difference in operating period B was small, resulting in insufficient toner 90 supply from the supply roller 43 to the surface of the developing roller 42. Therefore, it is preferable for the absolute value of the supply potential difference in operating period B to be larger, and it is preferable that it be controlled to have an absolute value at least larger than the supply potential difference in operating period A.

[0059] (Rating 3) Next, we compare Example 1 with Comparative Example 3-1. In Comparative Example 3-1, the supply potential difference and regulated potential difference during operating periods A and B of the initial setup operation were controlled to appropriate conditions, but horizontal streaks occurred due to contamination of the charging roller 2. This is because the timing of the change in the supply potential difference and regulated potential difference when transitioning from operating period A to operating period B was not controlled to appropriate conditions. As a result, when the supply potential difference changed from V1A to V1B and the amount of toner 90 increased, sufficient charge was not applied to the surface of the developing roller 42 at the contact position with the regulated blade 44, causing fogging.

[0060] Furthermore, in Comparative Examples 3-2 and 3-3, horizontal streaks occurred due to contamination of the charging roller 2 for the same reasons as in Comparative Example 3-1. In addition, in Comparative Example 3-3, it took a long time for the lubricant on the developing roller 42 to be replaced by toner 90 during operating period A. This is because the polarity of the supply potential difference and regulating potential difference during operating period A was set to the opposite polarity of those during the image forming operation (opposite polarity to the normal charging polarity of toner 90). In other words, because the supply potential difference and regulating potential difference were set to the opposite polarity, the supply of toner 90 from the supply roller 43 to the surface of the developing roller 42 and the intake of toner 90 at the contact point between the regulating blade 44 and the developing roller 42 were excessively reduced. On the other hand, in Comparative Example 3-2, although it took longer than in Comparative Example 3-1, it was within a range that did not cause problems in actual use. Therefore, it is preferable that the supply potential difference and regulating potential difference during operating periods A and B of the initial setup operation be zero, or have the same polarity as the supply potential difference and regulating potential difference during the image forming operation.

[0061] Thus, in Example 1, compared to the comparative examples described above, the supply potential difference and regulated potential difference during operating periods A and B of the initial setup operation, as well as the timing of the change in the supply potential difference and regulated potential difference when transitioning from operating period A to operating period B, are controlled to appropriate conditions. As a result, in Example 1, the toner 90 layer on the developing roller 42 is stably formed while suppressing the occurrence of fogging, and horizontal streaks caused by dirt on the charging roller 2 are less likely to occur.

[0062] Furthermore, in Example 2, in addition to the conditions in Example 1, the rotation speeds of the developing roller 42 and the supply roller 43 during operating periods A and B were controlled to appropriate conditions. As a result, in Example 2, the occurrence of fogging was further suppressed, and a good image without horizontal streaks caused by dirt on the charging roller 2 was obtained.

[0063] As described above, according to Examples 1 and 2, it is possible to suppress the occurrence of fogging when a new developing device is first put into use.

[0064] [Differentiation] The following describes modifications of the present invention. The basic configuration and operation of the modified image forming apparatus 100 are the same as those of Example 1. Therefore, elements having the same or corresponding functions or configurations as those of the image forming apparatus 100 of Example 1 are denoted by the same reference numerals as in Example 1, and detailed descriptions are omitted.

[0065] In this modified example, a dedicated cleaning device is provided on the photosensitive drum 1. The cleaning device is located downstream of the primary transfer device 51 and upstream of the charging roller 2 in the rotational direction of the photosensitive drum 1, and recovers the toner remaining on the photosensitive drum 1 after the toner image has been transferred to the transfer target by the primary transfer device 51. Therefore, the toner 90 remaining on the surface of the photosensitive drum 1 after primary transfer is removed and recovered by the cleaning device before it reaches the charging position. In this case, even if fogging occurs during the initial setup operation, it will not adhere to the charging roller 2 and reduce the charging performance. However, unexpected toner consumption may occur, which may be detrimental to the user. For this reason, even when a dedicated cleaning device is provided on the photosensitive drum 1, unexpected toner consumption can be prevented by controlling the timing of changes in the supply potential difference and regulated potential difference as in Examples 1 and 2.

[0066] As described above, even with the modified configuration, it is possible to suppress the occurrence of fogging when a new developing device is first used. Therefore, this method is also effective when a dedicated cleaning device is provided for the photosensitive drum 1. [Explanation of Symbols]

[0067] 100 Image forming apparatus 1 Photosensitive drum 2 Charging rollers 42 Developing roller 43 Supply roller 44 Regulatory Blade 65 Control Unit 67 Power supply

Claims

1. An image forming apparatus that performs an image forming operation to form an image on a recording material, a photoreceptor that is rotatably provided and has a surface on which an electrostatic latent image is formed; a developer carrier that is rotatably provided, that contacts the photoconductor to form a developing section, and that supplies a developer that is charged to a normal charging polarity to the photoconductor in the developing section; a supply member that is rotatably provided and that contacts the developer carrying member to supply the developer to the developer carrying member; the developer carrying member contacts the developer carrying member at a second position downstream of a first position where the developer carrying member contacts the supply member and upstream of the developing unit in a rotation direction of the developer carrying member, a regulating member that regulates the developer on the developer carrier; a power supply device that applies a first voltage to the developer carrier, applies a second voltage to the supply member, and applies a third voltage to the regulating member; a control unit which controls, during a period different from the image forming operation, to execute a first non-image forming operation in which the first voltage is applied from the power supply device to the developer carrier, the second voltage is applied to the supply member, and the third voltage is applied to the regulating member while rotating the photoconductor, the developer carrier, and the supply member in a state in which the photoconductor and the developer carrier are in contact with each other with a surface potential difference that generates an electric field that moves the developer charged to the normal charging polarity from the photoconductor to the developer carrier, and a second non-image forming operation which is executed subsequent to the first non-image forming operation; Equipped with The control unit is controlling the power supply device so that, in the first non-image forming operation, a first potential difference which is a difference between the second voltage and the first voltage and a second potential difference which is a difference between the third voltage and the first voltage have the same polarity as the first potential difference and the second potential difference in the image forming operation, and have a small absolute value or become zero; controlling the power supply device so that, in the second non-image forming operation, the first potential difference and the second potential difference have the same polarity as the first potential difference and the second potential difference in the first non-image forming operation and have larger absolute values; an image forming apparatus characterized in that, when transitioning from the first non-image forming operation to the second non-image forming operation, the power supply device is controlled so as to change the second potential difference at a timing earlier than the timing at which the surface of the developer carrier positioned at the first position when the first potential difference is changed reaches the second position without passing through the development section due to the rotation of the developer carrier.

2. a charging unit that charges the surface of the photoconductor by applying a fourth voltage from the power supply device; 2. The image forming apparatus according to claim 1, wherein the control unit controls the power supply device so that, during the first non-image forming operation and the second non-image forming operation, a surface potential difference between the photoconductor and the developer carrier has a polarity that moves the developer charged to the normal charging polarity from the photoconductor to the developer carrier.

3. The image forming apparatus according to claim 2, characterized in that, during the image forming operation, the control unit controls the power supply device so that the first potential difference has a polarity that moves the developer charged to the normal charging polarity from the supply member to the developer carrier, and controls the power supply device so that the second potential difference has a polarity that moves the developer charged to the normal charging polarity from the regulating member to the developer carrier.

4. a drive unit that drives the developer carrier and the supply member, 4. The image forming apparatus according to claim 2, wherein the control unit controls the drive unit so that the rotational speeds of the developer carrier and the supply member in the first non-image forming operation are slower than the rotational speeds of the developer carrier and the supply member in the image forming operation.

5. a drive unit that drives the developer carrier and the supply member, 5. The image forming apparatus according to claim 4, wherein the control unit controls the drive unit so that the rotational speed of the developer carrier and the supply member in the first non-image forming operation is slower than the rotational speed of the developer carrier and the supply member in the second non-image forming operation.

6. 6. The image forming apparatus according to claim 5, wherein the control unit controls the drive unit so that the rotational speeds of the developer carrier and the supply member in the second non-image forming operation are the same as the rotational speeds of the developer carrier and the supply member in the image forming operation.

7. a developing device including the developer, the developer carrier, the supply member, and the regulating member; a detection means for detecting whether the developing device is new or not; Equipped with 7. The image forming apparatus according to claim 1, wherein the control unit executes the first non-image forming operation and the second non-image forming operation when the detection means determines that the developing device is new.

8. a process cartridge including the photoconductor, the developer, the developer carrying member, the supply member, and the regulating member; a detection means for detecting whether the process cartridge is a new one; Equipped with 7. The image forming apparatus according to claim 1, wherein the control unit executes the first non-image forming operation and the second non-image forming operation when the detection means determines that the process cartridge is new.

9. 9. The image forming apparatus according to claim 7, wherein said developer carrying member and said supplying member are coated with a lubricant when they are new.

10. a transfer member that transfers a developer image formed by developing the electrostatic latent image with the developer to a transfer target in the image forming operation, 10. The image forming apparatus according to claim 2, wherein the developer carrier collects developer remaining on the photosensitive member after the developer image is transferred to the transfer target member by the transfer member.

11. a transfer member that transfers a developer image formed by developing the electrostatic latent image with the developer to a transfer target in the image forming operation; a cleaning device that is provided downstream of the transfer member and upstream of the charging means in the rotation direction of the photoconductor, and that collects developer remaining on the photoconductor after the developer image is transferred to the transfer-receiving body by the transfer member; The image forming apparatus according to claim 2 , further comprising:

12. a contact / separation mechanism that brings the developer carrier into contact with the photoconductor or separates the developer carrier from the photoconductor; 12. The image forming apparatus according to claim 1, wherein the control unit controls the contact / separation mechanism to contact the developer carrier with the photosensitive member during the image forming operation, the first non-image forming operation, and the second non-image forming operation.

Images