Image forming apparatus and developing apparatus

Abstract

This enables the stable supply of toner to the surface of the developer carrier without requiring a supply roller in the developing device. [Solution] The developing apparatus 50 includes a developing container 53, a developer carrier 51, a flexible sheet 521, and a holding member 522 that can hold and rotate the sheet 521. The sheet 521 can change between a first state and a second state in which at least a portion is closer to the surface of the developer carrier 51 than in the first state, as the holding member 522 rotates. By changing from the first state to the second state, the toner contained in the developing container 53 is biased toward the surface of the developer carrier 51.

Description

Technical Field

[0006] , ,

[0005] , , ,

[0001] The present invention relates to an image forming apparatus such as a printer, a copying machine, a facsimile apparatus, or a multifunction machine having a plurality of functions among these functions, which uses an electrophotographic method or an electrostatic recording method, and a developing apparatus used in this image forming apparatus.

Background Art

[0002] An image forming apparatus using an electrophotographic method or an electrostatic recording method forms an electrostatic latent image on an image carrier such as a photosensitive drum, and develops the electrostatic latent image by supplying toner to the electrostatic latent image by a developing apparatus, thereby forming a toner image on the image carrier.

[0003] As a developing apparatus, for example, a developing apparatus using a non-magnetic one-component developer as a developer is known (Patent Document 1). This developing apparatus includes a developing roller (developer carrier) that carries toner and conveys it toward the image carrier, a supply roller that supplies toner to the developing roller, and a regulating member that regulates the amount of toner carried on the developing roller and conveyed toward the image carrier. As the supply roller, a sponge roller having a porous sponge layer provided around a metal core is widely used.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The toner stored in the developing apparatus changes its characteristics such as chargeability and fluidity as the developing apparatus is repeatedly used.

[0006] ​Factors contributing to such changes in toner characteristics include the toner being subjected to friction and other stresses at the contact points between the developing roller and the supply roller.

[0007] To mitigate the changes in toner characteristics mentioned above and to miniaturize the image forming apparatus, it is conceivable to omit the supply roller from the developing apparatus.

[0008] However, it is difficult to stably supply toner to the surface of the developing roller without providing a supply roller in the developing device. For example, in a configuration where the supply roller is simply removed from the developing device, density unevenness and white spots may occur even while developing one page of image, depending on the image being formed.

[0009] Therefore, an object of the present invention is to enable the stable supply of toner to the surface of a developer carrier without providing a supply roller in the developing device. [Means for solving the problem]

[0010] The above objectives are achieved by the image forming apparatus and developing apparatus according to the present invention. In summary, according to a typical embodiment of the present invention, an image forming apparatus having a rotatable image carrier for carrying a toner image, and a developing apparatus for forming a toner image on the surface of the image carrier, comprising: a developing container for containing toner, and a rotatable developer carrier that contacts the surface of the image carrier to form a developing section, carries the toner contained in the developing container, and transports it toward the image carrier, wherein the developing apparatus comprises a supply mechanism that can change between a first state and a second state in which at least a part is closer to the surface of the developer carrier than in the first state, and by changing from the first state to the second state, biases the toner contained in the developing container toward the surface of the developer carrier, a drive unit capable of operating the supply mechanism to change the state of the supply member between the first state and the second state, and a control unit for the drive unit An image forming apparatus is provided, comprising a control unit and a drive unit, wherein the timing at which the leading edge of the image forming region on the image carrier, in the rotational direction, reaches the developing unit is defined as a first timing, the timing at which the trailing end of the image forming region, in the rotational direction, finishes passing the developing unit is defined as a second timing, and the period between the first timing and the second timing is defined as a predetermined period, the control unit controls the drive unit such that, for at least a portion of the predetermined period, the supply mechanism operates to change the state of the supply member from a first state to a second state, and does not operate the supply mechanism to change the state of the supply member from a second state to a first state during the predetermined period.

[0011] Furthermore, according to another representative aspect of the present invention, a developing apparatus is provided comprising: a developing container for containing toner; a rotatable developer carrier for carrying the toner contained in the developing container; a flexible sheet having a first direction aligned with the rotation axis direction of the developer carrier, with a first portion on one end and a second portion on the other end held in a second direction intersecting the first direction; and a holding member that holds the second portion of the sheet and is rotatable about a rotation axis along the first direction, wherein the sheet can change between a first state and a second state in which at least a portion is closer to the surface of the developer carrier than in the first state by rotation of the holding member, and the change from the first state to the second state biases the toner contained in the developing container toward the surface of the developer carrier. [Effects of the Invention]

[0012] According to the present invention, it is possible to stably supply toner to the surface of the developer carrier without providing a supply roller in the developing device. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic cross-sectional view of an image forming apparatus. [Figure 2] This is a schematic cross-sectional diagram illustrating the operation of the rotary developing machine. [Figure 3] This is a schematic cross-sectional view illustrating how to replace a toner cartridge. [Figure 4] This is a schematic block diagram illustrating the control configuration of an image forming apparatus. [Figure 5] This is a schematic cross-sectional view of the developing unit. [Figure 6] This is a schematic perspective view showing a portion of the developing unit. [Figure 7] This is a schematic perspective of the supply mechanism. [Figure 8] This is a schematic cross-sectional view of the drive configuration of the supply mechanism. [Figure 9A] This is a schematic cross-sectional diagram illustrating the toner agitation process. [Figure 9B] It is a schematic cross-sectional view for explaining the stirring operation of toner. [Figure 9C] It is a schematic cross-sectional view for explaining the stirring operation of toner. [Figure 10] It is a schematic cross-sectional view of a developing unit. [Figure 11] It is a schematic diagram for explaining the circulation of toner in the developing unit. [Figure 12] It is a schematic cross-sectional view of a developing unit of a comparative example. [Figure 13] It is a schematic diagram for explaining the circulation of toner in the developing unit of a comparative example. [Figure 14] It is a schematic cross-sectional view of a developing unit of a comparative example. [Figure 15] It is a schematic cross-sectional view of a developing unit of a comparative example. [Figure 16] It is a schematic cross-sectional view of a developing unit of a comparative example. [Figure 17] It is a schematic cross-sectional view of a developing unit for explaining the operation of the supply mechanism. [Figure 18] It is a timing chart for explaining the operation of the supply mechanisms of a comparative example and an embodiment. [Figure 19] It is a timing chart for explaining the operation of the supply mechanism of a comparative example. [Figure 20] It is a timing chart for explaining another example of the control of the supply mechanism. [Figure 21] It is a schematic cross-sectional view of another example of a developing unit. [Figure 22] It is a schematic perspective view of another example of a holding shaft. [Figure 23] It is a schematic exploded perspective view of a holding shaft and a rotation assisting member. [Figure 24] It is a schematic exploded perspective view of a holding shaft and a rotation assisting member, a cross-sectional view of the rotation assisting member, and a graph showing the cam profile of the rotation assisting member. [Figure 25] It is a schematic cross-sectional view of another example of a developing unit. [Figure 26] It is a schematic exploded perspective view of a holding shaft and a biasing shaft. [Figure 27] This is a schematic exploded perspective view of the retaining shaft and slide assist member. [Figure 28] This is a schematic cross-sectional view of another example of a developing unit. [Figure 29] This is a schematic cross-sectional view of another example of a developing unit. [Figure 30] This is a schematic cross-sectional view of another example of a developing unit. [Figure 31] This is a schematic cross-sectional view of another example of a developing unit. [Figure 32] This is a schematic cross-sectional view of another example of an image forming apparatus. [Figure 33] This is a schematic cross-sectional view of another example of a developing unit. [Figure 34] This is a schematic cross-sectional view of another example of a developing unit. [Figure 35] This is a schematic cross-sectional view of another example of a developing unit. [Figure 36] This is a schematic cross-sectional view of another example of a developing unit. [Figure 37] This is a schematic cross-sectional view of another example of a developing unit. [Figure 38] This is a schematic cross-sectional view of another example of a developing unit. [Figure 39] This is a schematic perspective view of an example of a supply plate. [Figure 40] This is a schematic cross-sectional view of another example of an image forming apparatus. [Figure 41] This is a schematic cross-sectional view of another example of a developing unit. [Modes for carrying out the invention]

[0014] The image forming apparatus and developing apparatus according to the present invention will be described in more detail below with reference to the drawings. Note that the dimensions, materials, shapes, and relative arrangements of the components described in the following embodiments can be appropriately changed depending on the configuration and various conditions of the apparatus to which the present invention is applied, and the present invention is not limited to the following embodiments. Furthermore, in the following embodiments, elements having the same or corresponding functions or configurations are denoted by the same reference numerals, and redundant explanations are omitted as appropriate.

[0015] [Example 1] <Overall configuration of the image forming apparatus> First, the overall configuration of the image forming apparatus 1 of this embodiment will be described using Figure 1. Figure 1 is a schematic cross-sectional view of the image forming apparatus 1 of this embodiment. The image forming apparatus 1 of this embodiment is a rotary developing type color laser printer capable of forming a full-color image on a sheet S as a recording material using an electrophotographic method.

[0016] Here, for example, as shown in Figure 1, the direction approximately parallel to the vertical direction (direction of gravity) when the image forming apparatus 1 is installed on a horizontal surface is defined as the "Z-axis direction". The direction perpendicular to the Z-axis direction and approximately parallel to the rotation axis direction of the photosensitive drum 2 (the direction of the rotation axis 90C of the rotary body 90, described later) is defined as the "Y-axis direction". The direction perpendicular to both the Z-axis direction and the Y-axis direction is defined as the X-axis direction. Then, as needed, the directions of the arrows X, Y, and Z shown in the figure are defined as the positive directions of the X-axis, Y-axis, and Z-axis, respectively. The positive direction of the X-axis is the direction from left to right in Figure 1, the positive direction of the Y-axis is the direction from the front to the back of the page in Figure 1, and the positive direction of the Z-axis is the direction from the bottom to the top in Figure 1. The direction opposite to the positive directions of the X-axis, Y-axis, and Z-axis is defined as the negative direction. Furthermore, the positive directions of the X, Y, and Z axes (or the ends of the positive directions of the X, Y, and Z axes) are also called the positive X-axis side, the positive Y-axis side, and the positive Z-axis side, respectively, and their opposite directions are called the negative X-axis side, the negative Y-axis side, and the negative Z-axis side, respectively. Also, "up" and "down" refer to the up and down directions in the vertical direction (direction of gravity), but do not mean only directly above and directly below, but also include the areas above and below the horizontal plane passing through the element or position of interest. In addition, a direction along a given direction typically includes directions that are approximately parallel to the given direction. In addition, a direction intersecting a given direction typically includes directions that are approximately perpendicular to the given direction.

[0017] The image forming apparatus 1 has a photosensitive drum 2, which is a rotatable drum-shaped (cylindrical) photoreceptor (electrophotographic photoreceptor) that serves as an image carrier. The image forming apparatus 1 also has the following means arranged around the photosensitive drum 2: a charging roller 3, which is a roller-shaped charging member that serves as a charging means; a scanner 4, which serves as an exposure means; a developing rotary (rotary developing apparatus) 100, which serves as a developing means; and a photosensitive drum cleaning unit 6, which serves as a photoreceptor cleaning means. The surface of the photosensitive drum 2, which has been uniformly charged by the charging roller 3, is irradiated with laser light corresponding to the image information by the scanner 4, thereby forming an electrostatic latent image (electrostatic image) on the surface of the photosensitive drum 2. The developing rotary 100 has a rotary body 90 that serves as a developing apparatus support. The rotary body 90 has developing units 50y, 50m, 50c, and 50k, which serve as a developing apparatus that develop (reveal) the electrostatic latent images of the yellow, magenta, cyan, and black color components formed on the surface of the photosensitive drum 2 using toners of the corresponding colors. Furthermore, the developing rotary 100 has toner cartridges 70y, 70m, 70c, and 70k, which serve as detachable developer replenishment containers for the rotary body 90, corresponding to each developing unit 50y, 50m, 50c, and 50k. Inside each toner cartridge 70y, 70m, 70c, and 70k are yellow toner, magenta toner, cyan toner, and black toner, respectively, for replenishing the developing units 50y, 50m, 50c, and 50k. In this embodiment, in all of the developing units 50y, 50m, 50c, and 50k, a negatively charged, non-magnetic, one-component developer with an average particle size of 7 μm is used as the developer. Details of the image forming operation will be described later.

[0018] The suffixes y, m, c, and k in the designations for the developing units 50y, 50m, 50c, and 50k indicate the toner colors, respectively. y represents yellow, m represents magenta, c represents cyan, and k represents black. The same applies to other components such as the toner cartridges 70y, 70m, 70c, and 70k, and the trays 80y, 80m, 80c, and 80k, which will be described later. However, for components with the same or corresponding functions or configurations provided for each color, the suffixes y, m, c, and k indicating that they are components for one of the colors may be omitted, and they may be described collectively.

[0019] The image forming apparatus 1 further includes an intermediate transfer unit 10, a secondary transfer roller 12, a fixing device 40, and the like. The intermediate transfer unit 10 has an intermediate transfer belt 10a, which is an endless belt that serves as an intermediate transfer body. The intermediate transfer belt 10a is stretched over a plurality of tension rollers, namely drive rollers 10b and tension rollers 10d, and is taut with a predetermined tension. The intermediate transfer belt 10a rotates (moves in a circular motion) in the direction of arrow R3 (clockwise) when the drive rollers 10b are rotationally driven. A primary transfer roller 11, which is a roller-shaped primary transfer member that serves as a primary transfer means, is arranged on the inner circumferential surface side of the intermediate transfer belt 10a. The primary transfer roller 5 presses the intermediate transfer belt 10a toward the photosensitive drum 2 to form a primary transfer nip (primary transfer portion) N1, which is the contact portion between the photosensitive drum 2 and the intermediate transfer belt 10a. Furthermore, on the outer circumferential surface side of the intermediate transfer belt 10a, a secondary transfer roller 12, which is a roller-shaped secondary transfer member serving as a secondary transfer means, is positioned opposite the drive roller 10b, which also serves as a secondary transfer opposing roller. The secondary transfer roller 12 is pressed toward the drive roller 10b and contacts the drive roller 10b via the intermediate transfer belt 10a, thereby forming a secondary transfer nip (secondary transfer portion) N2, which is the contact point between the intermediate transfer belt 10a and the secondary transfer roller 12. In addition, a belt cleaning device 13, which serves as an intermediate transfer body cleaning means, is provided on the outer circumferential surface side of the intermediate transfer belt 10a, downstream of the secondary transfer nip N2 and upstream of the primary transfer nip N1 in the rotational direction of the intermediate transfer belt 10a.

[0020] <Rotary Developer> Next, the configuration and operation of the developing rotary 100 will be explained further.

[0021] As shown in Figure 1, the rotary body 90 is fitted with trays 80y, 80m, 80c, and 80k, which serve as cartridge holders for detachably holding each toner cartridge 70y, 70m, 70c, and 70k. Each tray 80y, 80m, 80c, and 80k is fitted with the corresponding color toner cartridges 70y, 70m, 70c, and 70k. This makes it possible to supply the corresponding color toner to each developing unit 50y, 50m, 50c, and 50k. Each tray 80y, 80m, 80c, and 80k is movably attached to the rotary body 90 for detaching the toner cartridges 70y, 70m, 70c, and 70k. Also, as shown in Figure 1, each developing unit 50y, 50m, 50c, and 50k has developing rollers 51y, 51m, 51c, and 51k, respectively, which serve as developer carriers. The developing roller 51 carries toner as a developer and rotates, supplying toner to the photosensitive drum 2. The developing unit 50 may be detachable from the rotary body 90. Details of the configuration of the developing unit 50 will be described later.

[0022] As shown in Figure 1, the rotary body 90 is rotatable in the direction of arrow R2 (clockwise) about a rotation axis 90C extending in the Y-axis direction. This allows the rotary body 90 to position any of the developing rollers 51y, 51m, 51c, or 51k facing the photosensitive drum 2. Also, as shown in Figure 1, the rotary body 90 is supported by the image forming apparatus body 1a so as to be able to swing about a pivot axis 91. The rotary body 90 is biased in the direction of arrow R4a (counterclockwise) about the pivot axis 91 extending in the Y-axis direction by a biasing means such as a spring, so as to bring the developing roller 51 into contact with the photosensitive drum 2. This allows the developing rotary 100 to form a developing nip (developing section) G, which is the contact point between the developing roller 51 and the photosensitive drum 2. Furthermore, the image forming apparatus body 1a is provided with a rotatable cam 96 that can contact the rotary body 90. By rotating the cam 96, the contact and separation state between the developing roller 51 and the photosensitive drum 2 can be controlled. The rotation axis 90C of the rotary body 90, the rotation axis of the developing roller 51, and the axis of the oscillating shaft 91 are all approximately parallel to the rotation axis (Y-axis direction) of the photosensitive drum 2.

[0023] Using Figure 2, the rotational movement of the rotary body 90 and the contact and separation movement between the photosensitive drum 2 and the developing roller 51 will be explained. Figure 2 is a schematic cross-sectional view of the developing rotary 100 and its surrounding components.

[0024] Figure 2(a) shows the operating standby position of the developing rotary 100 when the image forming apparatus 1 is waiting to perform an image forming operation. The rotary body 90 is positioned such that the photosensitive drum 2 and the developing roller 51 are separated, and the photosensitive drum 2 is in a phase position facing the cyan developing roller 51c and the black developing roller 51k.

[0025] Figure 2(b) shows the contact standby position of the developing rotary 100 when the rotary body 90 is rotated by a predetermined angle in the direction of arrow R2 from the state shown in Figure 2(a), bringing the developing roller 51 close to the photosensitive drum 2. The rotary body 90 is in a phase where the photosensitive drum 2 is facing the developing roller 51, with the photosensitive drum 2 separated from the developing roller 51. When the rotary body 90 is in this phase, it is possible to bring the developing roller 51 and the photosensitive drum 2 into contact through the contact operation between the developing roller 51 and the photosensitive drum 2, which will be described later. In the case of Figure 2(b), the yellow developing roller 51y is facing the photosensitive drum 2, which is the yellow contact standby position. In contrast, the position where the magenta developing roller 51m faces the photosensitive drum 2 is the magenta contact standby position. Similarly, the position where the cyan developing roller 51c faces the photosensitive drum 2 is the cyan contact standby position. Furthermore, the position in which the black developing roller 51k faces the photosensitive drum 2 is defined as the black contact standby position.

[0026] Figure 2(c) shows the developing position of the developing rotary 100 when the developing roller 51 is brought into contact with the photosensitive drum 2 to develop the electrostatic latent image on the drum 2. Specifically, from the contact standby position of the developing rotary 100 shown in Figure 2(b), the rotation of the rotary body 90 is stopped, and the cam 96 is rotated in the direction of arrow R5 (clockwise). This causes the cam 96 to move away from the rotary body 90. As mentioned above, a biasing force acts on the rotary body 90 in the direction of arrow R4a, centered on the pivot axis 91. Therefore, as the cam 96 rotates, the rotary body 90 oscillates (rotates) in the direction of arrow R4a around the pivot axis 91, and the developing roller 51 comes into contact with the photosensitive drum 2. In the case of Figure 2(c), the yellow developing roller 51y is in contact with the photosensitive drum 2, which is the yellow developing position. In contrast, the magenta developing position is defined as the position in which the magenta developing roller 51m is in contact with the photosensitive drum 2. The cyan developing position is defined as the position in which the cyan developing roller 51c is in contact with the photosensitive drum 2. The black developing position is defined as the position in which the black developing roller 51k is in contact with the photosensitive drum 2. In this embodiment, the developing position of the developing rotary 100 is defined as the position in which the angle between the horizontal line and the line drawn from the rotation axis 90C of the rotary body 90 to the developing nip G in contact with the developing roller 51 and the photosensitive drum 2 is 20°.

[0027] After the development operation to form a yellow toner image on the photosensitive drum 2 is completed, the yellow developing roller 51y is moved away from the photosensitive drum 2 in order to proceed with the development operation to form a magenta toner image. Specifically, from the yellow developing position shown in Figure 2(c), with the rotation of the rotary body 90 stopped, the cam 96 is rotated in the direction of arrow R5 to bring the cam 96 into contact with the rotary body 90. As a result, the rotary body 90 is biased by the cam 96 and oscillates (rotates) around the pivot axis 91 in the direction of arrow R4b (clockwise). Then, the yellow developing roller 51y is once again separated from the photosensitive drum 2, returning to the yellow contact standby position shown in Figure 2(b).

[0028] Here, the rotational movement of the rotary unit 90 was explained in relation to the yellow development position, but the rotational movement of the rotary unit 90 in relation to the magenta development position, cyan development position, and black development position are similar.

[0029] In this embodiment, the rotary body 90 is stopped rotating when bringing the developing roller 51 into contact with and separating from the photosensitive drum 2. Alternatively, the cam 96 may be rotated while the rotary body 90 is rotated in the direction of arrow R2 to perform the contact and separation operation between the developing roller 51 and the photosensitive drum 2.

[0030] Furthermore, Figure 2(d) shows the replacement position of the developer rotary 100 when a user replaces the toner cartridge 70. In the case of Figure 2(d), this is the replacement position of the developer rotary 100 when replacing the black toner cartridge 70k. In this embodiment, the replacement position of the developer rotary 100 is such that the longitudinal direction of the toner cartridge 70 in the XZ plane (cross-section perpendicular to the Y-axis direction) is approximately parallel to the horizontal line (X-axis direction).

[0031] The replacement of the toner cartridge 70 will be further explained using Figure 3. Figure 3 is a schematic cross-sectional view of the developing rotary 100 and its surrounding components, showing how the black toner cartridge 70k is attached to and detached from the image forming apparatus body 1a (rotary body 90). The image forming apparatus 1 has an attachment / detachment opening 16a, which is an opening provided on the side surface 16 on the X-axis positive side. The image forming apparatus 1 also has a door 14 that opens and closes the attachment / detachment opening 16a. As shown in Figure 3(a), when replacing the black toner cartridge 70k, the rotary body 90 stops with the black toner cartridge 70k supported by the black tray 80k in a position facing the attachment / detachment opening 16a and the door 14. This position of the developing rotary 100 is the replacement position of the developing rotary 100 when replacing the black toner cartridge 70k, and the longitudinal direction of the black toner cartridge 70k in the XZ plane is approximately parallel to the horizontal line (X-axis direction). From this state, as shown in Figure 3(b), the door 14 is opened and the black tray 80k is slid almost horizontally through the attachment / detachment opening 16a to the outside of the rotary body 90. In this state, the black toner cartridge 70k can be attached to and detached from the rotary body 90 (black tray 80k), and the user can replace the black toner cartridge 70k. After the black toner cartridge 70k has been replaced, the black tray 80k is returned to the inside of the rotary body 90 and the door 14 is closed in the reverse order of the above procedure.

[0032] Here, we have explained how to replace the black toner cartridge 70k as an example, but the replacement method for the yellow, magenta, and cyan toner cartridges 70y, 70m, and 70c is the same.

[0033] In this embodiment, the black toner cartridge 70k has a longer longitudinal length in the XZ plane than the other color toner cartridges 70y, 70m, and 70c. Of the toner cartridges 70y, 70m, 70c, and 70k, only the black toner cartridge 70k is positioned within the rotary body 90 such that one end in the longitudinal direction in the XZ plane coincides with the rotation axis 90C of the rotary body 90.

[0034] <Image Formation Process> Next, the image formation operation in this embodiment will be explained using Figures 1, 2, and 4. First, the image formation operation when forming a full-color image on sheet S will be explained.

[0035] When the video controller 160 (Figure 4) located in the main body 1a of the image forming apparatus receives image information from an external device (not shown), such as a host computer, it transmits a print signal to the control unit 150 located in the main body 1a of the image forming apparatus. The control unit 150 then controls each part of the image forming apparatus 1 to start the image forming operation. As mentioned above, at the time the image forming operation starts, the developing rotary 100 is in the operation standby position as shown in Figure 2(a). With the start of the image forming operation, the drum drive unit 171 (Figure 4), which is the photoreceptor driving means, starts rotating the photosensitive drum 2 in the direction of arrow R1 (counterclockwise). Almost simultaneously, the belt drive unit 172 (Figure 4), which is the intermediate transfer material driving means, starts rotating the intermediate transfer belt 10a in the direction of arrow R3 (clockwise). The surface of the rotating photoreceptor drum 2 is uniformly charged by the charging roller 3. In this embodiment, the photosensitive drum 2 has a negative charge polarity, and the surface of the photosensitive drum 2 is uniformly charged to a predetermined negative potential by the charging roller 3. During charging, a charge bias (charging voltage), which is a negative DC voltage, is applied to the charging roller 3 by the charge bias application unit 183 (Figure 4), which serves as a charge bias application means.

[0036] In this embodiment, when forming a full-color image, the image forming apparatus 1 sequentially moves the developing rollers 51y, 51m, 51c, and 51k to developing positions that contact the photosensitive drum 2. This causes the image forming apparatus 1 to sequentially form yellow, magenta, cyan, and black toner images on the photosensitive drum 2. The image forming apparatus 1 then performs a primary transfer of the yellow, magenta, cyan, and black toner images formed on the photosensitive drum 2 onto the intermediate transfer belt 10a. Subsequently, the image forming apparatus 1 performs a secondary transfer of the toner images formed on the intermediate transfer belt 10a onto a sheet S, such as a sheet of paper, which serves as a recording material.

[0037] A laser beam based on image data corresponding to the yellow image is shone onto the charged surface of the photosensitive drum 2 by the scanner 4, forming an electrostatic latent image corresponding to the yellow image on the surface of the photosensitive drum 2. In parallel with the formation of this electrostatic latent image, the rotary body 90 is rotated in the direction of arrow R2 (clockwise) by the rotary drive unit 173 (Figure 4), which serves as the rotary driving means. As a result, the developing rotary 100 is in a yellow contact standby position, as shown in Figure 2(b), with the yellow developing roller 51y close to the photosensitive drum 2. The cam 96 is then rotated in the direction of arrow R5 (clockwise) by the developing / disengaging drive unit 174 (Figure 4), which serves as the developing / disengaging driving means. As a result, the developing rotary 100 is positioned in a yellow developing position, as shown in Figure 2(c), with the yellow developing roller 51y in contact with the photosensitive drum 2.

[0038] Furthermore, if the developing roller 51 is stopped when it comes into contact with the rotating photosensitive drum 2, the surface of the developing roller 51 may be damaged by friction with the photosensitive drum 2. Therefore, in this embodiment, before rotating the cam 96 to bring the developing roller 51 into contact with the photosensitive drum 2, the developing roller 51 is started to rotate by the developing roller drive unit 175 (Figure 4), which serves as a developing drive means. In this embodiment, before the developing roller 51 comes into contact with the photosensitive drum 2, the developing roller clutch mechanism 175a (Figure 4) transmits the driving force from the developing drive gear (not shown) to the developing roller 51, causing the developing roller 51 to rotate in the direction of arrow R6 (clockwise) (Figure 5). The developing roller clutch mechanism 175a and the developing drive gear constitute the developing roller drive unit 175. The developing roller clutch mechanism 175a is controlled by the control unit 150. As a result, the developing roller 51 contacts the photosensitive drum 2 while rotating (in this embodiment, with a predetermined peripheral speed ratio between the peripheral speed of the photosensitive drum 2 and the peripheral speed of the developing roller 51). Furthermore, as the developing roller 51 moves to the developing position, the developing bias application unit 181 (Figure 4), which serves as a developing bias application means, is connected to the developing roller 51, making it possible to apply a predetermined developing bias (developing voltage) to the developing roller 51. In this embodiment, the application of the developing bias to the developing roller 51 begins almost simultaneously with the development roller 51 moving to the developing position. Furthermore, as the developing roller 51 moves to the developing position, the blade bias application unit 182 (Figure 4), which serves as a blade bias application means, is connected to the regulating blade 54 (Figure 5), which will be described later, making it possible to apply a predetermined blade bias to the regulating blade 54. In this embodiment, the application of the blade bias to the regulating blade 54 begins almost simultaneously with the development roller 51 moving to the developing position.

[0039] In this embodiment, the developing roller 51 is positioned in a developing position that contacts the photosensitive drum 2 before the leading edge of the area on the photosensitive drum 2 corresponding to one sheet S (hereinafter also simply referred to as the "area corresponding to sheet S") reaches the position corresponding to the developing nip G. The area on the photosensitive drum 2 corresponding to sheet S is an area that includes an image forming area, which will be described later, and is set for each page of image transferred to one sheet S. The leading edge and trailing edge of the area on the photosensitive drum 2 corresponding to sheet S refer to the leading edge and trailing edge, respectively, in the direction of movement of the surface of the photosensitive drum 2 (the same applies to the image forming area and the image formed in the image forming area). The developing roller 51 only needs to be positioned in a developing position that contacts the photosensitive drum 2 before the leading edge of the image forming area (hereinafter also simply referred to as the "image forming area") of the image transferred to one sheet S (one page of image) reaches the position corresponding to the developing nip G. The image-forming area on the photosensitive drum 2 is a region where a toner image can be formed, set for each image transferred to a sheet S (one page of image). If a margin is provided at least one of the following: the leading edge, the trailing edge in the transport direction of the sheet S, and one end and the other end in the width direction which is approximately perpendicular to the transport direction of the sheet S, the image-forming area will be narrower than the area corresponding to the sheet S. However, if no margin is provided, the image-forming area and the area corresponding to the sheet S may be the same region.

[0040] When the yellow developing roller 51y is positioned in the developing position, an electrostatic latent image corresponding to the yellow image formed on the surface of the photosensitive drum 2 moves to the developing nip G, which is the contact point between the yellow developing roller 51y and the photosensitive drum 2. Then, due to the potential difference between the electrostatic latent image formed on the surface of the photosensitive drum 2 and the developing bias applied to the yellow developing roller 51y, the yellow toner carried on the yellow developing roller 51y moves to the surface of the photosensitive drum 2. As a result, a yellow toner image is formed on the surface of the photosensitive drum 2. In this embodiment, toner charged with the same polarity as the charging polarity of the photosensitive drum 2 (negative polarity in this embodiment) adheres to the exposed area on the photosensitive drum 2, where the absolute value of the potential has decreased after being uniformly charged and then exposed (reverse development method). In this embodiment, the normal charging polarity of the toner, which is the main charging polarity of the toner during development, is negative polarity.

[0041] The yellow toner image formed on the surface of the photosensitive drum 2 is transferred (primary transfer) onto the intermediate transfer belt 10a at the primary transfer nip N1 where the photosensitive drum 2 and the intermediate transfer belt 10a come into contact, by the action of the primary transfer roller 11. During primary transfer, the primary transfer roller 11 is subjected to a primary transfer bias (primary transfer voltage), which is a DC voltage with the opposite polarity to the normal charging polarity of the toner, by the primary transfer bias application unit 184 (Figure 4), which serves as a primary transfer bias application means. Here, the intermediate transfer belt 10a has a circumference that is somewhat long relative to the length of the sheet S in the transport direction. Furthermore, the secondary transfer roller 12 and the belt cleaning device 13 are kept away from the surface of the intermediate transfer belt 10a until the toner images of the four colors—yellow, magenta, cyan, and black—are formed on the surface of the intermediate transfer belt 10a.

[0042] The image forming apparatus 1 performs a developing operation to form a yellow toner image up to a position corresponding to the rear end of the image forming area on the photosensitive drum 2 (in this embodiment, after the rear end of the area corresponding to the sheet S on the photosensitive drum 2 has passed the developing nip G), and then proceeds to a developing operation to form a magenta toner image. That is, from the state in which the developing rotary 100 is in the yellow developing position, the developing contact drive unit 174 rotates the cam 96 in the direction of arrow R5. As a result, the developing rotary 100 moves to the yellow contact standby position, where the yellow developing roller 51y is separated from the photosensitive drum 2. Subsequently, the rotary body 90 is rotated in the direction of arrow R2 by the rotary drive unit 173, and the developing rotary 100 moves to the magenta contact standby position.

[0043] In this embodiment, when the developing rotary 100 transitions from the developing position to the contact standby position, the developing roller clutch mechanism 175a interrupts the transmission of driving force from the developing drive gear to the developing roller 51, stopping the rotation of the developing roller 51. If the developing roller 51 continues to rotate, toner deterioration may progress, mainly at the contact point between the regulating plate 542 of the regulating blade 54 (described later) and the developing roller 51. To suppress this, it is desirable to stop the rotation of the developing roller 51 as much as possible when the developing rotary 100 is not in the developing position. Also in this embodiment, when the developing rotary 100 transitions from the yellow developing position to the yellow contact standby position, the developing bias application unit 181 is separated from the developing roller 51, thereby interrupting the developing bias applied to the developing roller 51. Furthermore, in this embodiment, when the developing rotary 100 transitions from the yellow developing position to the yellow contact standby position, the blade bias application unit 182 is separated from the regulating blade 54, thereby interrupting the blade bias applied to the regulating blade 54.

[0044] Subsequently, as with the yellow toner image, an electrostatic latent image corresponding to the magenta image is formed on the surface of the photosensitive drum 2, and the developing rotary 100 is moved to the magenta developing position. Then, a magenta toner image is formed on the surface of the photosensitive drum 2 and transferred onto the intermediate transfer belt 10a. In this case, for example, when outputting a red image, the magenta toner image is transferred on top of the yellow toner image already transferred on the intermediate transfer belt 10a.

[0045] In this way, the developing rotary 100 is rotated by 90° increments, sequentially adopting the developing positions for magenta, cyan, and black. As a result, toner images of yellow, magenta, cyan, and black are sequentially formed on the surface of the photosensitive drum 2. The toner images formed on the surface of the photosensitive drum 2 are then sequentially transferred to the surface of the intermediate transfer belt 10a. As a result, toner images of the four colors that constitute a full-color image are formed on the surface of the intermediate transfer belt 10a. In addition, the secondary transfer roller 12 is brought into contact with the intermediate transfer belt 10a in accordance with the timing of the formation of the four toner images on the intermediate transfer belt 10a, preparing for secondary transfer.

[0046] In parallel with the formation of a toner image on the intermediate transfer belt 10a, a sheet S is fed from a sheet storage section 300 located at the bottom of the image forming apparatus 1 by a pickup roller 310. Separated one sheet at a time by a feed roller 311 and a separation roller 312, the sheets S are sent to a transport roller pair 320. The transport roller pair 320 then transports the sheets S to a secondary transfer nip N2 where the intermediate transfer belt 10a and the secondary transfer roller 12 come into contact, in time with the toner image on the intermediate transfer belt 10a. As a result, the toner image on the intermediate transfer belt 10a is transferred (secondary transfer) to the surface of the sheet S as it passes through the secondary transfer nip N2. During secondary transfer, a secondary transfer bias (secondary transfer voltage), which is a DC voltage with the opposite polarity to the normal charging polarity of the toner, is applied to the secondary transfer roller 12 by a secondary transfer bias application unit 185 (Figure 4), which serves as a secondary transfer bias application means.

[0047] The sheet S onto which the toner image has been transferred is sent to a fixing device 40, which serves as a fixing means. The fixing device 40 has a heating unit 41 and a pressure roller 42. The fixing device 40 heats and pressurizes the sheet S using the heating unit 41 and the pressure roller 42, thereby fixing (melting and solidifying) the toner image onto the sheet S. After passing through the fixing device 40, the sheet S is discharged (output) as an output product onto a discharge section 44 located outside (above) the image forming apparatus 1 by a pair of discharge rollers 43.

[0048] As mentioned above, the rotary body 90 may be rotated in the direction of arrow R2 while the developing roller 51 and the photosensitive drum 2 are brought into contact and separated. For example, while rotating the rotary body 90, the developing roller 51 is started to rotate just before the image forming area on the photosensitive drum 2 reaches the position corresponding to the developing nip G, and the developing roller 51 is brought into contact with the photosensitive drum 2 in that state. In other words, in this case, the developing rotary 100 does not enter the contact standby position but enters the developing position. After the developing operation is completed, the rotary body 90 is rotated while the developing roller 51 is still rotating, so that the developing roller 51 is separated from the photosensitive drum 2, and then the rotation of the developing roller 51 is stopped. In other words, in this case, the developing rotary 100 does not enter the contact standby position from the developing position but moves to the developing position for the next color.

[0049] Specifically, for example, the following configuration can be used. Similar to this embodiment, the rotary body 90 is made oscillating and biased toward the photosensitive drum 2. In addition, a cam is provided at the end of the rotary body 90 in the Y-axis direction, which is rotatable concentrically and integrally with the rotary body 90, and a contact member (such as a roller) is provided on the image forming apparatus body 1a that contacts the outer circumference of this cam to guide the rotation of the cam. This cam has a shape with recesses corresponding to each color developing unit 50 so that as the rotary body 90 rotates, the developing rollers 51 of each color developing unit 50 come into contact with the photosensitive drum 2 and move away from the photosensitive drum 2. When the developing rollers 51 move away from the photosensitive drum 2, the contact member contacts the outer circumference of the cam other than the recesses. As the rotary body 90 rotates and the contact member is positioned in the recess of the cam, the rotary body 90 oscillates toward the photosensitive drum 2, causing the developing rollers 51 to come into contact with the photosensitive drum 2. Furthermore, as the rotary body 90 rotates, the contact member disengages from the recess in the cam and contacts the outer circumference of the cam other than the recess, causing the developing roller 51 to separate from the photosensitive drum 2. Also, the developing roller 51 starts rotating just before contacting the photosensitive drum 2 and stops rotating immediately after separating from the photosensitive drum 2.

[0050] Thus, the image forming apparatus 1 may be configured such that the rotary body 90 rotates, causing the developing roller 51 to come into contact with the photosensitive drum 2, and then releasing the contact between the developing roller 51 and the photosensitive drum 2. In other words, the image forming apparatus 1 may be configured such that the rotary body 90 is stopped while developing is being performed, but when developing is complete, the rotary body 90 rotates and the developing roller 51 moves away from the photosensitive drum 2. In this case, the developing roller 51 of each color developing unit 50 can be sequentially brought into contact with and separated from the photosensitive drum 2 by substantially only the operation of rotating the rotary body 90. Therefore, there is no need to provide special configurations or drive sources for contact and separation, which is advantageous for miniaturization and cost reduction of the apparatus. In addition, since the contact and separation operations and the switching operations of the developing units 50 can be performed simultaneously, it is advantageous for high speed.

[0051] Next, the image formation operation when forming a black monochrome image on sheet S will be described. In this case, the developing rotary 100 moves from the operation standby position to the black developing position. In this state, similar to the formation of toner images of each color when forming a full-color image, the photosensitive drum 2 is charged and exposed, and an electrostatic latent image corresponding to the black image is formed on the surface of the photosensitive drum 2. The electrostatic latent image formed on the surface of the photosensitive drum is then developed with black toner by the black developing roller 51k positioned in the developing position. When forming black monochrome images on multiple sheets S consecutively, the developing rotary 100 remains in the black developing position, and the development of the electrostatic latent images of the images to be formed on multiple sheets S continues. If black monochrome images are not to be formed consecutively, the developing rotary 100 returns to the operation standby position. The black toner image formed on the photosensitive drum 2 is first transferred onto the intermediate transfer belt 10a, and then secondarily transferred onto sheet S. The subsequent operations are the same as when forming a full-color image.

[0052] <Control Configuration> Figure 4 is a schematic block diagram of the control configuration of the image forming apparatus 1 in this embodiment. The image forming apparatus 1 includes a control unit 150 that controls the operation of the image forming apparatus 1, and a video controller (image processing unit) 160. The control unit 150 includes a CPU 151 as an arithmetic processing means (arithmetic processing unit), a memory 152 composed of ROM, RAM, non-volatile memory, etc. as a storage means (storage unit), and an input / output unit (not shown) that exchanges signals between the control unit 150 and devices outside the control unit 150. The ROM stores control programs and control data. The RAM stores calculation results by the CPU 151 and detection results by various sensors. The non-volatile memory stores various setting information and various history information. The video controller 160 receives image information from an external device (not shown), such as a host computer, generates a print signal for image forming in the image forming apparatus 1, and transmits it to the control unit 150. The control unit 150 controls each part of the image forming apparatus 1 based on this print signal to execute the image forming operation.

[0053] The control unit 150 is connected to various parts of the image forming apparatus 1. For example, the control unit 150 is connected to various drive units such as the drum drive unit 171, belt drive unit 172, rotary drive unit 173, developing / disconnecting drive unit 174, developing roller drive unit 175, and the supply member drive unit 176, which will be described later. The control unit 150 is also connected to various bias application units such as the developing bias application unit 181, blade bias application unit 182, charging bias application unit 183, primary transfer bias application unit 184, and secondary transfer bias application unit 185. The scanner 4 is also connected to the control unit 150. The control unit 150 controls each part of the image forming apparatus 1 to perform image forming operations based on the print signal. Note that some components of the drum drive unit 171, belt drive unit 172, rotary drive unit 173, developing / disconnecting drive unit 174, developing roller drive unit 175, and supply member drive unit 176 may be common to all components. For example, the drive motor may be provided independently for each object to be driven, or a single drive motor may be shared for multiple objects to be driven. In this embodiment, the developing drive gear that transmits driving force to the developing roller 51 and the supply mechanism 52 (described later) is shared, and this developing drive gear constitutes the developing roller drive unit 175 and the supply member drive unit 176, respectively.

[0054] <Developing Unit Configuration> Next, the developing unit 50 of this embodiment will be further described with reference to Figures 5 and 6. In this embodiment, the developing units 50y, 50m, 50c, and 50k are substantially identical except for the color of the toner they contain.

[0055] Figure 5 is a schematic cross-sectional view of the developing unit 50, toner cartridge 70, and tray 80. Note that Figure 5 shows the developing rotary 100 in the developing position and the developing roller 51 positioned in the developing location, as shown in Figure 2(c). Figure 6 is a schematic perspective view of the developing unit 50 with the developing roller 51 removed, viewed from the outside of the developing unit 50 (the side where the photosensitive drum 2 is located).

[0056] As shown in Figure 5, the developing unit 50 includes a developing container (developing frame) 53, a developing roller 51 as a developer carrier (developing member), a regulating blade 54 as a regulating member, and a supply mechanism (supply device) 52.

[0057] The developing roller 51 is a roller consisting of a conductive developing roller core 511 and a conductive rubber layer 512 provided around the developing roller core 511. The developing roller 51 is attached to the developing container 53 by rotatably supporting both ends of the developing roller core 511 in the direction of its rotation axis. The developing roller 51 is rotatable in the direction of arrow R6 (clockwise) by a driving force transmitted to a developing roller gear (not shown) attached to one end of the developing roller core 511 in the direction of its rotation axis. In other words, in this embodiment, the developing roller 51 rotates so that the surface (outer surface) of the photosensitive drum 2 and the surface (outer surface) of the developing roller 51 move in the forward direction at the developing nip G. The developing roller gear receives a driving force from a developing drive gear (not shown) via a developing roller clutch mechanism 175a (Figure 4). Furthermore, by connecting the developing roller core 511 to the developing bias application unit 181 (Figure 4), a predetermined developing bias can be applied to the developing roller 51. A predetermined potential difference is formed between the potential of the image portion of the electrostatic latent image on the photosensitive drum 2 and the potential of the developing roller 51 (the potential of the developing bias), causing the toner supported on the surface of the developing roller 51 to move to the photosensitive drum 2.

[0058] The regulating blade 54 includes a support plate 541 as a blade support member and a regulating plate 542 as a regulating part. The developing blade 54 is attached to the developing container 53 by fixing the support plate 541 to the developing container 53 with screws (not shown). The support plate 541 is fixed to the surface of the developing container 53 that extends in the Y-axis direction (direction of the rotation axis of the developing roller 51) adjacent to the developing roller 51 upstream of the developing nip G in the rotational direction of the developing roller 51. In this embodiment, the regulating plate 542 is made of a flat plate of SUS (stainless steel). The regulating plate 542 is in contact with the rubber layer 512 of the developing roller 51 with a predetermined contact pressure. As a result, the regulating plate 542 can regulate the amount of toner carried on the surface of the developing roller 51 to a predetermined amount. Furthermore, by connecting the blade bias application unit 182 (Figure 4) to the blade sheet metal 541, a predetermined current can be supplied between the rubber layer 512 of the developing roller 51 and the regulating plate 542 of the regulating blade 54. The regulating plate 542 is composed of a plate-shaped member that is elongated in one direction (long-length) and approximately rectangular in plan view, and is arranged so that its longitudinal direction is along the Y-axis direction. The regulating plate 542 has a fixed end, which is one end in the short direction approximately perpendicular to its longitudinal direction, fixed to the support sheet metal 541, and a free end, which is the other end, in contact with the rubber layer 512 of the developing roller 51. The regulating plate 542 is in contact with the developing roller 51 in a counter-direction with respect to the rotation direction of the developing roller 51 such that the free end is located upstream of the fixed end in the direction of movement of the surface of the developing roller 51.

[0059] The developing container 53 is provided with a sealing sheet 561. The sealing sheet 561 is made of a flexible, elongated (long-length) sheet-like member that is roughly rectangular in plan view, and is positioned so that its longitudinal direction is along the Y-axis. One end of the sealing sheet 561, which is a fixed end in the short direction substantially perpendicular to its longitudinal direction, is fixed to the developing container 53, and the other end, which is a free end, is in contact with the rubber layer 512 of the developing roller 51 at a predetermined contact pressure. The fixed end of the sealing sheet 561 in the short direction is fixed to the surface of the developing container 53 that extends in the Y-axis direction adjacent to the developing roller 51, downstream of the developing nip G in the rotational direction of the developing roller 51. The sealing sheet 561 seals the space between the developing container 53 and the developing roller 51 along the Y-axis direction, preventing toner from leaking from the developing container 53.

[0060] Furthermore, as shown in Figure 6, end sealing members 562a and 562b are provided at both ends of the developing container 53 in the Y-axis direction. The end sealing members 562a and 562b are in contact with the rubber layer 512 of the developing roller 51 at both ends of the developing roller 51 in the Y-axis direction. The end sealing members 562a and 562b prevent toner from leaking from both ends of the developing container 53 in the Y-axis direction.

[0061] Here, the opening (space) of the developing unit 50 formed by the regulating plate 542 of the regulating blade 54, the sealing sheet 561, and the end sealing members 562a and 562b is referred to as the developing opening 53a. The toner contained in the developing container 53 is supplied to the surface of the developing roller 51 at the developing opening 53a and is carried on the surface of the developing roller 51. Of the surface of the developing roller 51, the portion corresponding to the developing opening 53a, that is, the portion facing the inside of the developing container 53 to which the toner contained in the developing container 53 can be supplied, is referred to as the supplied surface 51a. As will be described in more detail later, the more toner is supplied to this supplied surface 51a, in other words, the larger the area of ​​the supplied surface 51a to which toner is supplied, the greater the amount of toner supplied to the developing roller 51, and the less likely white spots will occur, as will be described later.

[0062] As shown in Figure 5, the toner cartridge 70 has a toner container (toner frame) 71. Inside the toner container 71, there is a toner storage section 71a for storing toner. The toner container 71 is also provided with a discharge opening 71b, which is an opening for discharging toner from the toner storage section 71a and communicates with the toner storage section 71a. The toner cartridge 70 is movable relative to the developer container 53 between the mounting position shown in Figure 3(a) and the retracted position shown in Figure 3(b), which is retracted from the mounting position. On the other hand, the developer container 53 is provided with a receiving opening 53b, which is an opening for receiving toner into the developer container 53. When the toner cartridge 70 is positioned in the mounting position, the discharge opening 71b of the toner cartridge 70 and the receiving opening 53b of the developer container 53 face each other. The toner storage section 71a of the toner cartridge 70 and the inside of the developer container 53 communicate with each other via a communication section 60 (dashed line in Figure 5) which is composed of the discharge opening 71b and the receiving opening 53b. As will be explained in more detail later, when toner is supplied from the toner cartridge 70 to the developing unit 50, the developing unit 50 and the toner cartridge 70 are positioned so that the orientation of the communication section 60 is vertically downward (towards the negative Z-axis) rather than horizontal. The orientation of the communication section 60 can be represented by a straight line that is approximately perpendicular to the inner wall of the developing container 53 and the inner wall of the toner container 71 adjacent to the communication section 60 in the XZ plane.

[0063] Furthermore, the developing unit 50 is provided with a backflow prevention member 55 capable of covering the receiving opening 53b. The backflow prevention member 55 has an opening / closing section 55a and a weight section 55b, which are made of a flexible, elongated (long-length) sheet-like member that is roughly rectangular in plan view. The opening / closing section 55a is positioned so that its longitudinal direction is along the Y-axis direction, and one end of the short direction which is roughly perpendicular to its longitudinal direction, which is the fixed end (upper end), is fixed to the developing container 53, while the other end, the free end (lower end), is provided with a weight section 55b. The opening / closing section 55a is movable between a position where it abuts the inner wall of the developing container 53 so as to cover the receiving opening 53b and a position where it is spaced away from the inner wall of the developing container 53, thereby opening and closing the receiving opening 53b (communication section 60). The weight section 55b stabilizes the behavior of the opening / closing section 55a. As will be explained in more detail later, the rotation of the rotary body 90 changes the positional relationship between the weight portion 55b and the communication portion 60, thereby controlling the contact and separation state between the opening / closing portion 55a and the inner wall of the developing container 53. That is, when supplying toner from the toner cartridge 70 to the developing container 53 through the communication portion 60, the opening / closing portion 55a is separated from the inner wall of the developing container 53 to facilitate toner supply. On the other hand, when not supplying toner other than when supplying toner from the toner cartridge 70 to the developing container 53, the weight portion 55b causes the opening / closing portion 55a to contact the inner wall of the developing container 53, thereby preventing backflow of toner from the communication portion 60 to the toner cartridge 70. Note that the communication portion 60 may be provided at multiple locations (for example, 2 to 3 locations) in the Y-axis direction. In that case, a backflow prevention member 55 is provided for each communication portion 60.

[0064] Next, the supply mechanism 52 in this embodiment will be described using Figures 5 to 7. Figure 7 is a schematic perspective view of the supply mechanism 52 in this embodiment. The supply mechanism 52 includes a supply sheet 521, which is a sheet portion serving as a supply member, and a holding shaft 522, which is a sheet holding member.

[0065] The supply sheet 521 is composed of a flexible, elongated (long-length) sheet-like member that is approximately rectangular in plan view, and is arranged so that its longitudinal direction is along the Y-axis. The length of the supply sheet 521 in the longitudinal direction is set to cover approximately the entire area inside the developing container 53 in the Y-axis direction. The supply sheet 521 is fixed to the inner wall of the developing container 53 at a fixing portion (first portion) 521a, which is the surface of one end of the supply sheet 521 in the short direction which is approximately perpendicular to its longitudinal direction, and joined (fixed) to the holding shaft 522 at a joining portion (second portion) 521b, which is the surface of the other end. In this embodiment, the fixing portion 521a is fixed to the inner wall of the developing container 53 by double-sided tape over approximately the entire width of the supply sheet 521 in the Y-axis direction. In this embodiment, the joining portion 521b is joined to the holding shaft 522 by double-sided tape over approximately the entire width of the supply sheet 521 in the Y-axis direction. Depending on the configuration of the image forming apparatus 1, the fixing part 521a may be fixed to the main body 1a of the image forming apparatus.

[0066] In this embodiment, a polycarbonate sheet with a thickness of 150 μm was used as the supply sheet 521. However, the material of the supply sheet 521 is not limited to this. The supply sheet 521 may be a resin sheet such as polycarbonate, PET (polyethylene terephthalate), PPS (polyphenylene sulfide), and Kapton (trade name for ultra-heat-resistant and ultra-cold-resistant polyimide film), a rubber sheet such as urethane rubber, or a metal sheet such as SUS. Furthermore, the thickness of the sheet can be set as appropriate, as long as it has sufficient flexibility. In addition, the fixing part 521a is not limited to being fixed to the developing container 53, but may be fixed to the regulating blade 54, for example. Also, the fixing part 521a is not limited to being fixed to the developing container 53, etc., by double-sided tape, but may be fixed by adhesive or welding, for example. Furthermore, the fixing portion 521a does not need to be tightly fixed to the developing container 53 or the like by double-sided tape or adhesive. It is sufficient that it does not detach from the developing container 53 or the like when the supply sheet 521 is moved (deformed), as will be described later. For this reason, the supply sheet 521 may be provided with a hole (engaged portion) that serves as the fixing portion 521a, and the developing container 53 may be provided with a projection (engaged portion) that has a return, for example, and the supply sheet 521 may be held by the developing container 53 by engaging this projection with the hole.

[0067] The holding shaft 522 has a rectangular prism-shaped holding portion 5221 with a substantially square cross-section in the XZ plane, and cylindrical rotating shaft portions 5222 provided at both ends of the holding portion 5221 in the direction of the rotation axis of the holding shaft 522. The joint portion 521b of the supply sheet 521 is attached to one of the four faces of the holding portion 5221 with double-sided tape. A notch 5222a is provided in the rotating shaft portion 5222 on the Y-axis minus side of the rotating shaft portions 5222 at both ends in the Y-axis direction, and the supply member gear 591 (Figures 8(a), (b)), which will be described later, engages with this notch 5222a. As a result, the holding shaft 522 can rotate (rotate) in the direction of arrow R7a (clockwise) and arrow R7b (counterclockwise) about the rotation axis 522C extending in the Y-axis direction. In each figure, the direction of arrow R7a indicates the rotation direction that changes the supply sheet 521 from a state of relatively large deflection (the first state described later) to a state of relatively small deflection (the second state described later). Also, in each figure, the direction of arrow R7b indicates the rotation direction that changes the supply sheet 521 from a state of relatively small deflection (the second state described later) to a state of relatively large deflection (the first state described later). The developing container 53 is provided with holding shaft support holes 5341 (Figure 8(b)) at both ends in the Y-axis direction. The holding shaft 522 is attached to the developing container 53 by the fact that the rotating shaft portions 5222 at both ends in the Y-axis direction are rotatably supported in the holding shaft support holes 5341. This defines the positional relationship between the developing container 53 and the holding shaft 522.

[0068] Furthermore, the joint portion 521b is not limited to being fixed to the holding shaft 522 by double-sided tape, but may also be fixed by means of adhesive or welding, for example. Also, the joint portion 521b does not need to be tightly fixed to the holding shaft 522 by double-sided tape or adhesive, as long as it does not detach from the holding shaft 522 and become free when the supply sheet 521 is moved (deformed), as will be described later. For this reason, the supply sheet 521 may be provided with a hole (engaged portion) as the joint portion 521b, and the holding shaft 522 may be provided with a projection (engaged portion) having a barb, for example, and the supply sheet 521 may be held by the holding shaft 522 by engaging this projection with the hole.

[0069] As shown in Figure 5, in this embodiment, the supply sheet 521 is provided in the developing container 53 with a predetermined deflection. That is, in this embodiment, in the XZ plane, the length of the supply sheet 521 excluding the fixing part 521a and the connecting part 521b is set to be longer than the length of the straight line connecting the position of the fixing part 521a fixed to the developing container 53 (the position where the fixing part 521a is fixed in the developing container 53) and the position of the connecting part 521b joined to the holding shaft 522 (the position of the holding shaft 522 as defined above). The supply sheet 521 is curved so as to be convex on the opposite side from the surface of the developing roller 51. As will be described in detail later, as the holding shaft 522 rotates in the direction of arrow R7a, the deflected supply sheet 521 becomes taut (the deflection of the supply sheet 521 decreases). In other words, the supply sheet 521 moves (deforms) so that at least a part of it approaches the surface of the developing roller 51. As a result, the toner in the developing container 53 (more specifically, the supply area 53g, which will be described later) is supplied to the supply surface 51a of the developing roller 51.

[0070] Furthermore, as shown in Figure 5, the internal space of the developing container 53 is separated by a supply sheet 521. Here, the space on the developing roller 51 side of the supply sheet 521 is referred to as the "supply area 53g". On the other hand, the space on the opposite side of the supply area 53g of the supply sheet 521 is referred to as the "back side area 53d". As will be described in more detail later, the toner contained in the supply area 53g is supplied to the supply surface 51a of the developing roller by the supply mechanism 52. This makes the amount of toner carried on the surface of the developing roller 51 more stable.

[0071] Next, the drive configuration (drive mechanism) of the supply mechanism 52 (holding shaft 522) will be explained using Figure 8. Figure 8 shows the gear train that drives the supply mechanism 52. Figure 8(a) is a schematic cross-sectional view taken in the XZ plane (a cross-section perpendicular to the Y-axis direction), and Figure 8(b) is a schematic cross-sectional view taken in the XY plane (a cross-section perpendicular to the Z-axis direction).

[0072] The developing unit 50 is equipped with a supply gear 591, an idler gear 592, and a biasing spring 593.

[0073] The idler gear 592 is a two-stage gear in which a missing-tooth gear portion 5921 and an input-receiving gear portion 5922 are integrated. The idler gear 592 is attached to the developing unit 50 by the fact that a support-receiving hole portion 592a provided in the center of the idler gear 592 is supported by a support shaft 5811 provided on the side cover 581. The side cover 581 is attached to the side of the developing container 53 on the negative Y-axis side. The input-receiving gear portion 5922 is located on the negative Y-axis side of the idler gear 592, and when driving force is transmitted from the developing drive gear (not shown) to the input-receiving gear portion 5922, the idler gear 592 rotates in the direction of arrow R8 (counterclockwise). The missing-tooth gear portion 5921 is located on the positive Y-axis side of the idler gear 592, and a gear portion 5921a and a missing portion 5921b are provided on its circumferential surface. Furthermore, a supply member clutch mechanism 176a (Figure 4) is connected to the idler gear 592. The control unit 150 can control whether or not to transmit the driving force from the developer drive gear to the idler gear 592 by controlling the supply member clutch mechanism 176a. The supply member clutch mechanism 176a and the developer drive gear constitute the supply member drive unit 176.

[0074] The supply member gear 591 has a gear portion 5911 and a protruding portion 5912. The supply member gear 591 is attached to the supply mechanism 52 by the gear portion 5911 being attached to a rotating shaft portion 5222 provided on the holding shaft 522 of the supply mechanism 52. The supply member gear 591 transmits driving force to the holding shaft 522 by the engagement portion 5911a provided on the gear portion 5911 engaging with a notch portion 5222a provided on the rotating shaft portion 5222 of the holding shaft 522. The gear portion 5911 is arranged to be connectable to the notched gear portion 5921 of the idler gear 592. The supply member gear 591 rotates in the direction of arrow R7a (clockwise) as the idler gear 592 rotates in the direction of arrow R8. Furthermore, a cylindrical projection 5912 is positioned on the Y-axis minus side of the supply member gear 591, and a notch 5912a is formed on a part of the circumferential surface of the projection 5912.

[0075] The biasing spring 593 is composed of a torsion coil spring, which is a biasing member acting as a biasing means, and has an engaging portion 593a at one end and a held portion 593b at the other end. The biasing spring 593 is positioned to cover the periphery of the protrusion 5912 of the supply member gear 591. The engaging portion 593a of the biasing spring 593 is engaged with a notch 5912a formed in the protrusion 5912 of the supply member gear 591. On the other hand, the held portion 593b of the biasing spring 593 is held by a holding portion 5812 provided on the side cover 581.

[0076] When the idler gear 592 rotates in the direction of arrow R8, and the gear portion 5921a of the idler gear 592 engages with the gear portion 5911 of the supply member gear 591, the supply member gear 591 rotates in the direction of arrow R7a. The engaging portion 593a of the biasing spring 593 engages with the notch 5912a formed in the protruding portion 5912 of the supply member gear 591. Therefore, as the supply member gear 591 rotates, the engaging portion 593a of the biasing spring 593 also rotates in the direction of arrow R7a. On the other hand, the held portion 593b of the biasing spring 593 is held by the holding portion 5812. Therefore, as the supply member gear 591 rotates, the biasing spring 593 accumulates elastic energy. As the idler gear 592 rotates further, the notched portion 5921b of the idler gear 592 faces the supply member gear 591, causing the supply member gear 591 to disengage from the idler gear 592. As a result, no power acts on the supply member gear 591 to rotate in the direction of arrow R7a, and the elastic energy stored in the biasing spring 593 biases the supply member gear 591 in the direction of arrow R7b. Subsequently, as the idler gear 592 rotates further, the gear portion 5921a of the idler gear 592 engages with the gear portion 5911 of the supply member gear 591, causing the supply member gear 591 to rotate again in the direction of arrow R7a.

[0077] In this embodiment, with the configuration described above, the holding shaft 522 of the supply mechanism 52 is rotatable in both the direction of arrow R7a and arrow R7b. Note that the configuration for making the holding shaft 522 rotatable is not limited to the configuration described above, and can be appropriately selected depending on constraints such as the shape of the developing container 53. For example, another gear may be provided between the supply member gear 591 and the idler gear 592. Alternatively, the biasing spring 593 may be configured to engage with the holding shaft 522 instead of the supply member gear 591.

[0078] <Toner agitation by the rotation of the rotary unit> Next, the method for agitating the toner in the developing unit 50 in this embodiment will be described. As shown in Figure 5, the developing unit 50 in this embodiment is not equipped with any special components for agitating the toner contained in the developing container 53. In this embodiment, the toner in the developing unit 50 is agitated by the rotation of the rotary body 90. As will be described in detail later, as the developing roller 51 rotates during the image forming operation, the toner present in the supply area 53g gradually becomes slightly aggregated, and the fluidity of the toner decreases. In contrast, by agitating the toner in the developing unit 50 by the rotation of the rotary body 90, the fluidity of the toner present in the supply area 53g can be restored to a high state.

[0079] The toner agitation operation in the developing unit 50 in this embodiment will be explained using Figure 9. Figure 9 is a schematic cross-sectional view of the developing unit 50 and its surrounding components.

[0080] Note that in Figure 9, for illustrative purposes, only one color of the developing unit 50 and toner cartridge 70 are shown. Also, Figures 9(a) to 9(i) show the states when the rotary body 90 is rotated 45° in the direction of arrow R2, starting from Figure 9(a). The state in Figure 9(a) shows the state immediately after the development period (details to be described later) in which the electrostatic latent image on the photosensitive drum 2 is developed has ended. Then, in the states shown in Figures 9(c), 9(e), and 9(g), which are obtained by rotating the rotary body 90 90° in the direction of arrow R2 from the state in Figure 9(a), the development operation (development process) is performed with each color of toner. After that, by rotating the rotary body 90 another 90° in the direction of arrow R2, the state in Figure 9(i), which is the same as the state in Figure 9(a), is reached. Hereafter, each state shown in Figure 9 may be referred to by the rotation angle of the rotary body 90 in the direction of arrow R2 from the state in Figure 9(a). For example, the state shown in Figure 9(d) is sometimes referred to as the "135° rotated state." Also, for convenience, Figure 9 is divided into Figures 9A, 9B, and 9C, and the explanation will use the figure numbers 9(a) to 9(i) shown in each section.

[0081] Furthermore, the toner contained in the developing unit 50 and the toner cartridge 70 is collectively referred to as "toner T". In Figure 9, two types of toner T are illustrated with black circles and white circles. In the state shown in Figure 9(a) (the state immediately after the development period has ended), the toner T present in the supply area 53g is shown with black circles, and the toner T present in the back side area 53d or the toner cartridge 70 in the state shown in Figure 9(a) is shown with white circles. The toner T shown with black circles is referred to as "charged toner Tc". The toner T shown with white circles is referred to as "discharged toner Tn". As will be explained in more detail later, charged toner Tc is toner T with a higher surface charge than discharged toner Tn. Discharged toner Tn is unused toner T or toner T that has been discharged to some extent over time. The more discharged toner T there is in the supply area 53g, the less likely electrostatic aggregation occurs and the higher the fluidity.

[0082] First, in the state shown in Figure 9(a), the proportion of charged toner Tc is greater than the proportion of de-static toner Tc in the supply area 53g (typically, it is dominated by charged toner Tc). This is because, as will be explained in more detail later, when the developing rotary 100 is in the developing position, the surface charge of the toner T in the supply area 53g gradually increases due to friction mainly at the contact point between the developing roller 51 and the regulating blade 54. On the other hand, even in the state shown in Figure 9(a), the proportion of de-static toner Tn is greater than the proportion of charged toner Tc in the back side area 53d (typically, it is dominated by de-static toner Tn).

[0083] Subsequently, the developing roller 51 is separated from the photosensitive drum 2, and the rotary body 90 is rotated in the direction of arrow R2. This results in the state of 45° rotation shown in Figure 9(b), followed by the state of 90° rotation shown in Figure 9(c). At this time, a portion of the charged toner Tc that was present in the supply area 53g in the state shown in Figure 9(a) moves to the back side area 53d due to gravity acting on the negative Z-axis side. Also, at this time, gravity acts on the weight portion 55b of the backflow prevention member 55, causing the opening / closing portion 55a of the backflow prevention member 55 to come into contact with the inner wall of the developing container 53. This prevents toner T from flowing back from the developing container 53 to the toner cartridge 70.

[0084] Subsequently, the rotary body 90 is further rotated in the direction of arrow R2, passing through the 135° rotated state shown in Figure 9(d) and then reaching the 180° rotated state shown in Figure 9(e). At this time, some of the static elimination toner Tn that was present in the rear side region 53d in the state shown in Figure 9(a) moves to the supply region 53g due to gravity. Subsequently, in the 225° rotated state shown in Figure 9(f), almost all of the static elimination toner Tn that was present in the rear side region 53d in the state shown in Figure 9(a) has been transported to the supply region 53g.

[0085] Subsequently, the rotary body 90 is further rotated in the direction of arrow R2, passing through the 270° rotated state shown in Figure 9(g) and then reaching the 315° rotated state shown in Figure 9(h). At this time, gravity acting on the weight portion 55b of the backflow prevention member 55 causes the opening / closing portion 55a of the backflow prevention member 55 to move again away from the inner wall of the developing container 53. This allows the static-eliminating toner Tn contained in the toner cartridge 70 to move to the developing container 53. At least a portion of the static-eliminating toner Tn moving from the toner cartridge 70 to the developing container 53 moves to the supply area 53g. Subsequently, the rotary body 90 is further rotated in the direction of arrow R2, reaching the 360° rotated state shown in Figure 9(i).

[0086] In this manner, as the rotary body 90 rotates 360° from the state shown in Figure 9(a), the static-eliminating toner Tn is transported from the toner cartridge 70 to the supply area 53g, and the static-eliminating toner Tn that was present in the rear side area 53d is also transported to the supply area 53g. At that time, if there is enough toner T inside the developing container 53 to sufficiently fill the supply area 53g, the toner T that does not fit into the supply area 53g is transported to the rear side area 53d.

[0087] Furthermore, the series of rotational movements of the rotary body 90 shown in Figures 9(a) to 9(i) agitate the toner T contained in the developing container 53. As a result, in the 360° rotation state shown in Figure 9(i), the supply area 53g and the back side area 53d contain a mixture of charged toner Tc and discharged toner Tn. Also, as will be described in more detail later, the toner T present in the supply area 53g tends to be compacted as the developing roller 51 rotates. In contrast, by performing the agitation operation described above, the toner T present in the supply area 53g can be returned to a highly fluid state.

[0088] <Toner supply to the surface of the developing roller> Next, the supply of toner T to the surface of the developing roller 51, specifically the toner-receiving surface 51a of the developing roller 51, will be explained using Figures 10 to 13.

[0089] {Explanation of the state shown in Figures 10-13} Figures 10 to 13 are schematic cross-sectional views of the developing unit 50 or a part thereof, showing the developing rotary 100 in the developing position and the developing roller 51 positioned in the developing position, as shown in Figure 2(c). In Figures 10 to 13, it is assumed that a predetermined amount of toner T is contained in the developing container 53. Note that the toner T shown in Figures 10 and 12, for example, is depicted as being approximately 100 to 1000 times larger than the actual size ratio of the toner T to the developing unit 50. Regarding numerical ranges, "~" indicates a range that includes the numbers before and after it.

[0090] Figure 10 shows the state after the rotary body 90 has rotated (and oscillated) to position the developing roller 51 in contact with the photosensitive drum 2, and before the development period (described in detail later) begins, in which the electrostatic latent image on the photosensitive drum 2 is developed. In this state, the toner T contained in the developing container 50 is not lightly aggregated due to the rotation of the rotary body 90 and is in a highly fluid state. Figure 11 is a schematic cross-sectional view showing the circulation of toner T in the supply area 53g immediately after the developing unit 50 has reached the state shown in Figure 10 and the developing roller 51 has started rotating in the direction of arrow R6. The supply area 53g is formed by the developing roller 51 and the supply sheet 521.

[0091] On the other hand, Figure 12 shows the state after the electrostatic latent image development operation on the photosensitive drum 2 has been performed without moving (deforming) the supply sheet 521, while remaining in the state shown in Figure 10. Note that the state of the supply sheet 521 in Figures 10 and 12 is substantially the same as the state of the supply sheet 521 in Figure 5 (the first state described later). Figure 13 is a schematic cross-sectional view showing the circulation of toner T in the supply area 53g in the state shown in Figure 12.

[0092] As will be explained in more detail later, in the states shown in Figures 12 and 13, the toner T forms a wall surface in the vicinity of the surface of the developing roller 51 that extends along the arc of the surface of the developing roller 51. As a result, the amount of toner T in contact with the surface of the developing roller 51, i.e., the supplied surface 51a, is reduced compared to the states shown in Figures 10 and 11. In other words, in the states shown in Figures 12 and 13, the area of ​​the supplied surface 51a to which toner T is supplied is reduced compared to the states shown in Figures 10 and 11.

[0093] {When the toner has high fluidity (Figures 10 and 11)} First, we will further explain the state in which the toner T has high fluidity (the state just before the development period begins), as shown in Figures 10 and 11, due to the rotation of the rotary body 90.

[0094] As shown in Figure 11, when image formation (development) is performed, the rotation of the developing roller 51 in the direction of arrow R6 generates a flow of toner T in the developing unit 50 in the directions indicated by arrows F1, F2, F3, F4, and F5.

[0095] First, the toner T supported on the surface of the developing roller 51 flows along the surface of the rubber layer 512 of the developing roller 51 in the direction of arrow F1. At this time, the toner T is deposited on the surface of the developing roller 51 in layers of approximately 1 to 10. In this embodiment, the average particle size of the toner T is 7 μm. Therefore, the thickness of the toner T layer that moves in the direction of arrow F1 as the developing roller 51 rotates is estimated to be slightly less than 100 μm, even with a generous estimate.

[0096] The toner T supported on the surface of the developing roller 51 is restricted to a predetermined amount by the restricting plate 542 of the restricting blade 54. In this embodiment, the toner T on the surface of the developing roller 51 is restricted to a thickness of 1 to 3 layers by the restricting plate 542. As a result, the toner T restricted by the restricting plate 542 flows away from the surface of the developing roller 51 in the direction of arrow F2. At this time, a predetermined amount of toner T already exists in the space between the restricting plate 542 and the inner wall of the developing container 53, located vertically below (Z-axis minus side) the contact portion between the developing roller 51 and the restricting plate 542, forming a stationary layer. Therefore, when an image is formed, the toner T that moves in the direction of arrow F1 flows in the direction of arrow F2 as if repelled by this stationary layer. On the other hand, of the toner T carried on the developing roller 51, the toner T that passes through the contact area between the developing roller 51 and the regulating plate 542 without being restricted by the regulating plate 542 has its surface charged more negatively due to friction between the rubber layer 512 of the developing roller 51 and the regulating plate 542. Furthermore, the blade bias applied to the regulating blade 54 injects an electric charge into the surface of this toner T. In other words, the toner T that passes through the contact area between the developing roller 51 and the regulating plate 542 has a higher surface charge than the toner T contained in the supply area 53g. Then, the toner T that has passed through the contact area between the developing roller 51 and the regulating plate 542, excluding the amount that has moved to the surface of the photosensitive drum 2, passes through the contact area between the developing roller 51 and the sealing sheet 561 and is transported back to the supply area 53g.

[0097] Next, the toner T repelled by the aforementioned immobile layer flows in the direction of arrow F3, gradually spreading along the surface of the supply sheet 521. That is, the flow of toner T is widely dispersed within the supply area 53g, and even in the part close to the developing roller 51, it flows towards the vertically upward side (Z-axis positive side). At this time, the toner T being transported in the direction of arrow F2 flows in a way that pushes out the toner T present in the supply area 53g, and the flow velocity of the toner T flowing in the direction of arrow F3 is slower than the flow velocity of the toner T flowing in the direction of arrow F1 and the flow velocity of the toner T flowing in the direction of arrow F2.

[0098] Subsequently, near the surface of the toner T on the vertically upward side (Z-axis positive side) of the supply area 53g (dashed line in Figure 11), the flow of toner T diffuses in the direction of arrow F4. That is, the toner T that reaches the surface loses its upward thrust (Z-axis positive side), and most of it is dragged along by the flow of toner T carried on the surface of the developing roller 51 in the direction of arrow F1, flowing towards the developing roller 51 (X-axis negative side). Along with this flow, the toner T inside the surface (Z-axis negative side) also flows towards the developing roller 51, creating a swirling flow of toner T near the surface.

[0099] Then, the toner T transported to the vicinity of the surface of the developing roller 51 by the flow in the direction of arrow F4 flows in the direction of arrow F5. That is, this toner T flows toward the surface of the developing roller 51 and along the rotation direction of the developing roller 51 (arrow R6 direction) due to the flow of toner T in the direction of arrow F1 carried on the surface of the developing roller 51. At this time, in most cases, the surface of the developing roller 51 is covered with toner T that has passed through the contact area between the developing roller 51 and the regulating plate 542 of the regulating blade 54, as described above. However, if a large portion of the toner T on the surface of the developing roller 51 is used for developing the electrostatic latent image on the photosensitive drum 2, the amount of toner T carried on the surface of the developing roller 51 at this time may be relatively small. Furthermore, the toner T that has passed through the contact area between the developing roller 51 and the regulating plate 542 has a higher surface charge than the toner T contained in the supply area 53g due to friction and blade bias, as described above. Due to this surface charge, the toner T contained in the supply area 53g is electrostatically attracted toward the surface of the developing roller 51.

[0100] Furthermore, this electrostatic force does not act over a wide area. In other words, this electrostatic force does not widely affect the supply sheet 521 side (X-axis positive side) of the supply area 53g. Therefore, the propulsive force of the toner T flow in the direction of arrow F4 toward the developing roller 51 side (X-axis negative side) is limited to filling the empty space near the developing roller 51 with toner T. That is, the toner T only flows to the extent that it fills the space of toner T that has flowed along the rotation direction of the developing roller 51 (arrow R6 direction) due to the toner T flow in the directions of arrows F1 and F5. In other words, this electrostatic force does not actively push the entire toner T of the supply area 53g toward the surface side (X-axis negative side) of the developing roller 51.

[0101] {When the supply mechanism is not controlled (Figures 12 and 13)} Next, we will further explain the state after the electrostatic latent image development operation on the photosensitive drum 2 has been performed without moving (deforming) the supply sheet 521, as shown in Figures 12 and 13 (the state immediately after the development period has ended).

[0102] As shown in Figure 13, in this state, the toner T in the developing unit 50 may no longer flow in the directions indicated by arrows F3, F4, and F5 in Figure 11. In this state, the toner T may form a wall surface near the surface of the developing roller 51 that extends along the arc of the surface of the developing roller 51. As a result, the amount of toner T in contact with the surface of the developing roller 51, i.e., the supplied surface 51a, is reduced compared to the state shown in Figure 11. In other words, in the state shown in Figure 13, the area of ​​the supplied surface 51a to which toner T is supplied is reduced compared to the state shown in Figure 11.

[0103] First, as described above, in the supply area 53g, the toner T flows as if being pushed out by the toner T itself. Therefore, as the developing roller 51 is rotated and the toner T is circulated in the developing unit 50, the toner T present in the supply area 53g gradually becomes more densely arranged.

[0104] In addition, toner used in electrophotographic image forming apparatuses generally does not have the high fluidity of water, but flows in a somewhat lightly aggregated state due to electrostatic and non-electrostatic forces. Furthermore, as described above, toner T that has passed through the contact area between the developing roller 51 and the regulating plate 542 of the developing blade 54 acquires a higher surface charge. Therefore, as the developing roller 51 is rotated and the toner T is circulated in the developing unit 50, the proportion of toner T with a higher surface charge in the supply area 53g increases, making it more prone to electrostatic aggregation.

[0105] As a result, as the developing roller 51 rotates during the image forming process, the toner T present in the supply area 53g gradually aggregates densely, reducing its fluidity. Consequently, toner blocks Tb with macroscopic walls on the order of several millimeters to several centimeters become visible, particularly near the surface of the toner T (the dashed line in Figure 13). These aggregated toner blocks Tb do not collapse due to gravity and form walls with angles closer to vertical than the angle of repose.

[0106] Thus, at least before the development period shown in Figures 10 and 11 begins, the toner T in the supply area 53g is agitated by the rotation of the rotary body 90 and is in a highly fluid state. Then, as the developing roller 51 rotates during the image forming operation, the toner T is compressed and electrostatically aggregated, causing the fluidity of the toner T in the supply area 53g to gradually decrease. As a result, after the development period shown in Figures 12 and 13 has ended, the toner T in the supply area 53g is in a somewhat lightly aggregated state, with toner blocks Tb being formed near the surface (dashed line in Figure 13).

[0107] In other words, from the start to the end of the development period, the toner T flowing in the directions of arrows F4 and F5 shown in Figure 11 flows in a lightly aggregated state. As a result, the toner T, which has solidified into blocks to some extent, is conveyed toward the surface of the developing roller 51. When this lightly aggregated toner T comes into contact with the flow in the direction of arrow F1, the entire block of solidified toner T is not necessarily conveyed by the flow in the direction of arrow F1, and only a portion of the lightly aggregated toner T may be scraped away by the flow in the direction of arrow F1. As this process is repeated, the lightly aggregated toner T remains near the surface of the developing roller 51 (it stays with a gap between it and the surface of the developing roller 51), as shown in Figure 13. As a result, the toner T present in the supply area 53g forms a wall surface with a radius of curvature larger than the outer surface of the developing roller 51 by a distance equivalent to the thickness of the toner layer supported on the surface of the developing roller 51. Therefore, in the state shown in Figures 12 and 13, the amount of toner T in contact with the surface of the developing roller 51, i.e., the toner to be supplied surface 51a, decreases compared to the state immediately after the toner T is agitated by the rotational movement of the rotary body 90 shown in Figures 10 and 11. As a result, the supply of toner T to the toner to be supplied surface 51a ceases, and as shown in Figure 13, the toner T may stop circulating within the supply area 53g.

[0108] In such a situation, for example, if an image is formed with a continuous area of ​​high print density, the amount of toner T supplied to the supply surface 51a of the developing roller 51 may be insufficient, resulting in white spots.

[0109] {Example of a configuration where white areas may occur} Using Figures 12 and 13, we explained the condition in which the amount of toner T supplied to the toner-receiving surface 51a of the developing roller 51 is insufficient, assuming that the developing operation is performed without moving (deforming) the supply sheet 521. A similar condition can occur in the configurations shown in Figures 14 to 16. Table 1 shows the occurrence of white spots in this embodiment and the comparative example. In Table 1, the comparative example includes the case in which the phase of the holding shaft 522 of the supply mechanism 52, as explained using Figures 12 and 13, is not changed (the supply sheet 521 is not moved (deformed)), as well as the configuration shown in Figures 14 to 16. Figures 14 to 16 are schematic cross-sectional views of the developing unit 50 of the comparative example. Also, in Table 1, the embodiment described later using Figure 17 is shown as Example 1. In Table 1, the occurrence of white spots is indicated as "○ (good)" when white spots can be sufficiently suppressed, and "× (bad)" when white spots occur beyond the acceptable range.

[0110] [Table 1]

[0111] For example, as shown in Figure 14, if a toner supply member is not provided to supply to the developing roller 51, the amount of toner supplied to the supplied surface 51a may be insufficient, similar to the example described using Figures 12 and 13. Also, as shown in Figure 15, if the inner wall of the developing container 53 is brought closer to the surface of the developing roller 51 to the same position as the supply sheet 521 shown in Figure 12, the amount of toner supplied to the supplied surface 51a may be insufficient, similar to the example described using Figure 12.

[0112] Therefore, as shown in Figure 16, it is conceivable to configure the developing unit 50 in such a way that it creates a flow of toner toward the surface of the developing roller 51. In the example in Figure 16, the developing unit 50 has a partition wall portion 533 that is molded integrally with the developing container 53. In the example in Figure 16, the space inside the developing container 53 is divided by this partition wall portion 533 into a supply area 53g and a rear side area 53d, similar to the developing unit 50 in this embodiment. The tip of the portion of this partition wall portion 533 that faces the supply area 53g, shown by the diagonal lines in Figure 16, is designated as the discharge surface 533a. The line extending from this discharge surface 533a (dashed line L1 in Figure 16) extends toward the surface of the developing roller 51. The toner that flows along the wall surface of the partition wall portion 533 flows toward the surface of the developing roller 51 along the discharge surface 533a. As a result, the discharge surface 533a of the partition wall portion 533 increases the amount of toner supplied to the surface of the developing roller 51. However, in the example shown in Figure 16, the thrust force toward the surface of the developing roller 51 acts only on the toner near the discharge surface 533a. Therefore, the increase in toner supply on the supply surface 51a of the developing roller 51 is limited to the portion 51a1 facing the discharge surface 533a, which is shown by the diagonal lines in Figure 16. As a result, the amount of toner supplied to the entire supply surface 51a is insufficient, and white spots may occur.

[0113] {Summary of the function of the supply sheet in this embodiment} The operation of the supply sheet 521 in this embodiment will be explained using Figure 17. Figure 17 is a schematic cross-sectional view of the developing unit 50 in this embodiment, showing the state immediately after the development period has ended (similar to the state in Figure 12).

[0114] In this embodiment, as shown in Figure 17, immediately after the development period ends, the holding shaft 522 of the supply mechanism 52 is rotated by a predetermined phase in the direction of arrow R7a. As a result, the supply sheet 521 fixed to the holding shaft 522 moves (deforms) as if being wound onto the holding shaft 522, reducing the deflection (stretching) of the supply sheet 521. Then, the toner T present in the supply area 53g is biased toward the surface of the developing roller 51 in the direction of arrow F6. As a result, toner T can be stably supplied to the supply surface 51a of the developing roller 51, and white spots can be suppressed.

[0115] <Control of the supply mechanism> Next, the control of the supply mechanism 52 in this embodiment will be described.

[0116] To suppress the white spots that occur due to the mechanism described above, it is effective to press the lightly aggregated toner near the surface of the developing roller 51 toward the surface of the developing roller 51, or to break up the toner that has settled near the surface of the developing roller 51. The function of the supply sheet 521 in this embodiment will be further explained below, comparing this embodiment with a comparative example.

[0117] {Explanation of Sequence Chart} Figures 18 to 20 are sequence charts illustrating the control of the supply mechanism 52, showing examples of changes in the control conditions of the supply mechanism 52.

[0118] In Figures 18 to 20, the horizontal axis represents the passage of time. Here, the process is shown in which the developing roller 51 is moved to a developing position in contact with the photosensitive drum 2 to develop the electrostatic latent image on the photosensitive drum 2, and then the developing roller 51 is moved away from the photosensitive drum 2 again.

[0119] Furthermore, in Figures 18 to 20, the vertical axis represents the phase of the holding shaft 522 of the supply mechanism 52 and the toner powder pressure (here also simply referred to as "powder pressure") acting on the supplied surface 51a of the developing roller 51. As for the phase of the holding shaft 522, "d1" represents the "first phase (holding shaft first position)" which brings the supply sheet 521 to a "first state (supply sheet first position)" where the deflection is relatively large (the largest in this embodiment), as shown in Figure 10. Also, as for the phase of the holding shaft 522, "d2" represents the "second phase (holding shaft second position)" which brings the supply sheet 521 to a "second state (supply sheet second position)" where the deflection is relatively small (the smallest in this embodiment), as shown in Figure 17. Note that the second state of the supply sheet 521 may be a taut state with virtually no deflection. Furthermore, as for the powder pressure, "P0" represents the powder pressure at the timing when the driving (rotation) of the developing roller 51 is started. Furthermore, a value of "0" for powder pressure indicates a state where almost no powder pressure is acting. Note that powder pressure is often not uniform in the direction of the rotation axis (Y-axis direction) of the developing roller 51. Here, the powder pressure shown is, as an example, the powder pressure at a predetermined position in the direction of the rotation axis (Y-axis direction) of the developing roller 51.

[0120] Furthermore, Figures 18 and 19 show the output images alongside the output images, schematically illustrating the occurrence of whiteouts and density unevenness. When the amount of toner supplied to the developing roller becomes unstable, "density unevenness" can occur, where the density (amount of toner) of a part of the image decreases in the area where the toner supply to the developing roller has decreased. In addition, if the amount of toner supplied to the developing roller decreases significantly, "whiteouts" can occur, where parts of the image are missing. Details of these output images will be described later.

[0121] {Explanation of various timings} First, we will explain the various timings in the process shown in Figures 18 to 20.

[0122] As mentioned above, as shown in Figure 2(a), the rotary body 90 rotates from a state where the developing rotary 100 is in an operating standby position. Then, at "timing t_ds", the driving force from the developing drive gear is transmitted to the developing roller gear via the developing roller clutch mechanism 175a, and the driving (rotation) of the developing roller 51 begins. This timing t_ds is also called the "driving start timing t_ds". Almost simultaneously, the driving force from the developing drive gear is transmitted to the supply member gear 591 engaged with the holding shaft 522 of the supply mechanism 52 via the idler gear 592, making it possible to drive the holding shaft 522. At that time, the supply member clutch mechanism 176a can control whether or not to transmit the driving force from the developing drive gear to the idler gear 592. Therefore, by controlling the supply member clutch mechanism 176a, the timing of starting the transmission of drive to the holding shaft 522 can be arbitrarily controlled.

[0123] Next, at "timing t_ts," the developing roller 51 is brought into contact with the photosensitive drum 2, as shown in Figure 2(c). That is, if an electrostatic latent image has formed on the photosensitive drum 2, development of the electrostatic latent image on the photosensitive drum 2 becomes possible from timing t_ts. This timing t_ts is also called the "contact timing t_ts."

[0124] Subsequently, "timing t_ps" indicates the timing when the leading edge of the area corresponding to sheet S on the photosensitive drum 2 reaches the developing nip G. This timing t_ps is also called the "image leading edge timing t_ps". Then, "timing t_pe" indicates the timing when the trailing edge of the area corresponding to sheet S on the photosensitive drum 2 has finished passing through the developing nip G. This timing t_pe is also called the "image trailing edge timing t_pe". As an example of a predetermined period, the period between this image leading edge timing t_ps and image trailing edge timing t_pe is called the "development period". Note that the image leading edge timing t_ps may be the timing when the leading edge of the image forming area on the photosensitive drum 2 reaches the developing nip G. Also, the image trailing edge timing t_pe may be the timing when the trailing edge of the image forming area on the photosensitive drum 2 has finished passing through the developing nip G.

[0125] After the development period is complete, at "timing t_te", the developing roller 51 is separated from the photosensitive drum 2, as shown in Figure 2(b). This timing t_te is also called the "separation timing t_te". In other words, the period from the contact timing t_ts to the separation timing t_te is the period during which toner can be supplied from the developing roller 51 to the photosensitive drum 2 to develop the electrostatic latent image on the photosensitive drum 2.

[0126] Subsequently, at "timing t_de", the transmission of driving force to the developing roller 51 is cut off. This timing t_de is also called the "drive termination timing t_de".

[0127] Furthermore, Figure 18(a) shows the reference image formed in the examples of Figures 18(b), (c), and 19(a), (b). In other words, the following explains what kind of image will be output in each example when the image shown in Figure 18(a) is input as a print signal. Note that the input image shown in Figure 18(a) is assumed to be a solid image with maximum density covering the entire image formation area, as it is an image with a high print density that makes it easy to see the occurrence of white spots and density unevenness. Here, normally, image formation on the sheet S does not proceed to the furthest end on the leading side and the furthest end on the trailing side in the transport direction of the sheet S, and a predetermined margin is provided at least one of these. The same applies to one end and the other end in the width direction of the sheet S. This is to prevent the image from being missing on the sheet S due to skew of the sheet S or mounting errors of the photosensitive drum 2.

[0128] {Explanation of each example} Next, we will explain each of the examples shown in Figures 18 to 20.

[0129] • Example in Figure 18(b) (Comparative Example) Figure 18(b) shows an example (comparative example) of the image forming operation performed without changing the phase of the holding axis 522, as explained using Figures 12 and 13.

[0130] In the example shown in Figure 18(b), the phase of the holding shaft 522 remains at the first phase d1, as shown in Figure 18(b1).

[0131] Furthermore, in the example shown in Figure 18(b), as shown in Figure 18(b2), the powder pressure gradually decreases from "P0" starting from the drive start timing t_ds, and becomes "0" during the development period (midway through the development period in the illustrated example). In other words, as explained using Figures 12 and 13, the toner that has lightly aggregated gradually settles near the surface of the developing roller 51, which reduces the amount of toner supplied to the supplied surface 51a, meaning that the powder pressure decreases. As a result, as shown in Figure 18(b3), the image becomes incomplete, with white areas appearing from the middle of the image.

[0132] As mentioned above, the powder pressure is often not uniform in the direction of the rotation axis of the developing roller 51. Therefore, the timing of white spots is uneven in the Y-axis direction (vertical direction in Figure 18(b3)), resulting in icicle-shaped white spots, for example, as shown in Figure 18(b3). In addition, as the amount of toner supplied to the supply surface 51a gradually decreases, the density of the output image may thin out in a stepwise or gradual gradient from the maximum density, eventually resulting in white spots. Furthermore, even if lightly aggregated toner remains near the surface of the developing roller 51, the toner may be temporarily transported to the surface of the developing roller 51. Therefore, as shown in Figure 18(b3), at the same time that white spots occur at any position in the Y-axis direction, an image may be partially formed (toner is output) at any other position in the Y-axis direction.

[0133] Thus, if the phase of the holding shaft 522 is not changed and no biasing force is applied to the toner by the supply sheet 521, the powder pressure gradually decreases, causing white spots to occur.

[0134] • Example in Figure 18(c) (Implementation) Figure 18(c) shows an example of the control of the supply mechanism 52 in this embodiment.

[0135] In the example shown in Figure 18(c), as shown in Figure 18(c1), the phase of the holding shaft 522 is gradually changed from the first phase d1 to the second phase d2, starting from the image tip timing t_ps. That is, the supply sheet 521 is gradually wound onto the holding shaft 522 from a first state in which the deflection is relatively large, to a second state in which the deflection is relatively small, and the surface of the supply sheet 521 gradually approaches the surface of the developing roller 51. As a result, throughout the development period, a biasing force is always applied by the supply sheet 521 that presses the toner toward the surface of the developing roller 51. Consequently, the supply of toner to the supplied surface 51a of the developing roller 51 is sufficient, and white spots can be suppressed. Hereinafter, the operation of bringing the supply sheet 521 toward the surface of the developing roller 51 will also be simply called the "approach operation".

[0136] Furthermore, in the example shown in Figure 18(c), as shown in Figure 18(c1), the elastic energy stored in the biasing spring 593 is released starting from the image trailing timing t_pe. As a result, the phase of the holding shaft 522 returns from the second phase d2 to the first phase d1, the surface of the supply sheet 521 moves away from the surface of the developing roller 51, and the supply sheet 521 returns from a second state in which the deflection is relatively small to a first state in which the deflection is relatively large. Hereinafter, the operation of moving the supply sheet 521 away from the surface of the developing roller 51 will also be simply called the "separation operation".

[0137] Furthermore, in the example of Figure 18(c), as shown in Figure 18(c2), the powder pressure gradually decreases from "P0" starting from the drive start timing t_ds, but gradually increases starting from the image leading edge timing t_ps. Subsequently, the powder pressure decreases starting from the image trailing edge timing t_pe. In the example of Figure 18(c), when the supply sheet 521 is moved away from the surface of the developing roller 51, the powder pressure temporarily becomes "0". In other words, by moving the supply sheet 521 away from the surface of the developing roller 51, the toner in the supply area 53g also moves away from the surface of the developing roller 51 as the supply sheet 521 moves. Therefore, the amount of toner supplied to the supplied surface 51a decreases, and the powder pressure temporarily becomes "0". However, if the powder pressure decreases at a timing after the development period has ended (after the image trailing edge timing t_pe), there is no problem. As shown in Figure 18(c), moving the supply sheet 521 away from the surface of the developing roller 51 temporarily reduces the powder pressure, and then the powder pressure rises again even without bringing the supply sheet 521 closer to the surface of the developing roller 51. This is because, as the supply sheet 521 moves, the toner in the supply area 53g also temporarily moves away from the surface of the developing roller 51, but if the toner has a certain degree of fluidity, the toner will come into contact with the surface of the developing roller 51 again. On the other hand, it is undesirable to move the supply sheet 521 away from the surface of the developing roller 51 during the development period. This will be explained using the example in Figure 19(a).

[0138] • Example in Figure 19(a) (Comparative Example) Figure 19(a) shows an example (comparative example) in which the supply sheet 521 is moved closer and further away multiple times during a single development period (Figure 19(a1)).

[0139] In the example shown in Figure 19(a), the powder pressure decreases sharply when the supply sheet 521 is moved away from the surface of the developing roller 51 during the development period (Figure 19(a2)). This temporarily reduces the amount of toner supplied to the feed surface 51a of the developing roller 51, resulting in density unevenness where the density is lighter in a horizontal band (Figure 19(a3)).

[0140] Furthermore, even in a configuration in which toner is supplied to the developing roller 51 by rapidly rotating a sheet-shaped or plate-shaped agitator, for example, density unevenness occurs in the rotational period pitch of the agitator, similar to the example in Figure 19(a).

[0141] Furthermore, even if the supply sheet 521 is not moved closer or further away multiple times, as in the example in Figure 19(a), and the movement of the supply sheet 521 is only moved away once during the development period, density unevenness will occur in the same way as in the example in Figure 19(a). In this case, as explained in the example in Figure 18(c), the powder pressure temporarily decreases by moving the supply sheet 521 away from the surface of the developing roller 51, and then increases again even if the supply sheet 521 is not brought close to the surface of the developing roller 51. Therefore, density unevenness occurs due to a temporary decrease in the amount of toner supplied. However, if the supply sheet 521 is not brought close to the surface of the developing roller 51 again after that, white areas will occur.

[0142] Thus, it is undesirable to control the supply mechanism 52 to move the supply sheet 521 away from the surface of the developing roller 51 during the developing period. On the other hand, it is also undesirable to keep the supply sheet 521 close to the surface of the developing roller 51. This will be explained using the example in Figure 19(b).

[0143] • Example in Figure 19(b) (Comparative Example) Figure 19(b) shows an example (comparative example) where the supply sheet 521 is kept close to the surface of the developing roller 51 (Figure 19(b1)). Specifically, at the drive start timing t_ds, the phase of the holding shaft 522 is changed from the first phase d1 to the second phase d2, bringing the supply sheet 521 closer to the surface of the developing roller 51. This temporarily increases the powder pressure (Figure 19(b2)). However, in the example of Figure 19(b), as in the example of Figure 18(b), the powder pressure decreases and white spots occur as lightly aggregated toner gradually settles near the surface of the developing roller 51.

[0144] Other examples of supply mechanism control Next, using Figure 20, another example (modification) of the control of the supply mechanism 52 according to the present invention will be described.

[0145] First, in the example shown in Figure 20(a), the phase of the holding shaft 522 is changed in steps (multi-stages) from the first phase d1 to the second phase d2, starting from the image tip timing t_ps, as a control to bring the supply sheet 521 closer to the surface of the developing roller 51 (Figure 20(a1)). In this case as well, as in the case where the phase of the holding shaft 522 is changed linearly (straightforward) as shown in Figure 18(c), the toner is biased toward the surface of the developing roller 51 (Figure 20(a2)), and white spots and density unevenness can be suppressed. Alternatively, the phase of the holding shaft 522 may be changed curvilinearly from the first phase d1 to the second phase d2 as a control to bring the supply sheet 521 closer to the surface of the developing roller 51. Furthermore, control methods that change the phase of the holding shaft 522 linearly, stepwise, and curvilinearly may be used in any combination. In other words, the phase of the holding shaft 522 can be changed linearly, stepwise, or curvilinearly for at least a portion of the period during which the phase of the holding shaft 522 is changed from the first phase d1 to the second phase d2.

[0146] Furthermore, in the example of Figure 20(b), the timing at which the phase of the holding shaft 522 is changed from the first phase d1 to initiate the approaching movement of the supply sheet 521 (hereinafter also referred to as the "approach start timing") is set before the image front timing t_ps. Also, in the example of Figure 20(b), the timing at which the phase of the holding shaft 522 is changed from the second phase d2 to initiate the separation movement of the supply sheet 521 (hereinafter also referred to as the "separation start timing") is set after the image rear timing t_pe. In the example of Figure 20(b), the approach start timing is set to the drive start timing t_ds, and the separation start timing is set to the drive stop timing t_de (Figure 20(b1)). In this case as well, the toner is biased toward the surface of the developing roller 51 (Figure 20(b2)), and white spots and density unevenness can be suppressed. In other words, if the contact and separation intervals between the developing roller 51 and the photosensitive drum 2, and the transmission and interruption of drive to the developing roller 51 can be appropriately controlled, the approach operation may start before the start of the development period and the separation operation may start after the end of the development period. Note that either starting the approach operation before the start of the development period or starting the separation operation after the end of the development period may be applied. That is, the approach operation may start before the start of the development period and the separation operation may start almost simultaneously with the end of the development period, or the approach operation may start almost simultaneously with the start of the development period and the separation operation may start after the end of the development period.

[0147] Furthermore, by using a control system like the example in Figure 20(b), the drive configuration of the supply mechanism 52 can be simplified. In other words, in this embodiment, the image forming apparatus 1 is provided with a supply member clutch mechanism 176a to control the phase of the idler gear 592 that transmits driving force to the holding shaft 522. On the other hand, if the drive start timing and drive stop timing of the idler gear 592 and the developing drive gear are simultaneous, the image forming apparatus 1 does not need to be provided with a supply member clutch mechanism 176a.

[0148] On the other hand, caution is necessary when setting the timing for approach and separation within the development period.

[0149] First, let's explain the case where the approach start timing is set during the development period. For example, in the example in Figure 20(c), the approach start timing is set during the development period (in the example shown, in the middle of the development period) (Figure 20(c1)). In this case, as shown by the dashed line in Figure 20(c2), if the powder pressure gradually decreases from the drive start timing t_ds and becomes "0" before the approach start timing, white spots may occur. However, the time required for the powder pressure to decrease with the rotation of the developing roller 51 until sufficient toner is no longer supplied to the surface of the developing roller 51 varies depending on various conditions. For example, if the fluidity of the toner is improved by adding a large amount of fine inorganic particles as an external additive to the surface of the toner, it may be possible to maintain a sufficient supply of toner to the developing roller 51 over multiple rotations of the developing roller 51 without biasing the toner toward the surface of the developing roller 51 by the supply sheet 521. In that case, as shown by the solid line in Figure 20(c2), the rate at which the powder pressure decreases with the rotation of the developing roller 51 is lower than that shown by the dashed line. In this case, even if the approach start timing is set during the development period, the toner can be biased toward the surface of the developing roller 51 before the powder pressure becomes "0", thereby suppressing white spots.

[0150] Conversely, if the toner fluidity decreases, such as when the developing unit 50 is used repeatedly (increasing cumulative usage) or when the image forming apparatus 1 is used in a low-temperature environment, the following may occur. That is, for example, even at the timing when the amount of phase change of the holding shaft 522 temporarily decreases, as in the example in Figure 20(a), there is a concern that the biasing of the toner to the developing roller 51 by the supply sheet 521 will be insufficient, and the amount of toner supplied to the developing roller 51 will decrease. Also, if the approach start timing is set during the development period, as in the example in Figure 20(c), there is a concern that the powder pressure will become "0" before the approach start timing, as shown by the dashed line. Therefore, in such cases, the control of the supply mechanism 52 as in the examples in Figure 18(c) and Figure 20(b) is preferable to the control of the supply mechanism 52 as in the examples in Figure 20(a) and Figure 20(c). In this way, the control of the supply mechanism 52 can be appropriately set according to the expected toner fluidity, etc.

[0151] Next, we will explain the case where the separation start timing is set during the development period. As explained using Figure 19(a), it is undesirable to set the separation start timing during the development period. This is true even when the toner has high fluidity. In other words, when the toner has high fluidity, the time required to recover from the reduced powder pressure after the supply sheet 521 is moved away from the surface of the developing roller 51, as explained using Figure 18(c), is shortened. However, the powder pressure still temporarily decreases as the toner in the supply area 53g moves along with the movement of the supply sheet 521.

[0152] However, in the following cases, the separation start timing can be set during the development period. For example, as explained using Figure 18(a), a predetermined margin is usually provided with respect to the shape of the sheet S. Therefore, it is not a problem to set the separation start timing at least by this margin amount before the image trailing edge timing t_pe. In other words, in the example of Figure 18(c), the separation start timing was set after the trailing edge of the area corresponding to the sheet S on the photosensitive drum 2 had finished passing through the development nip G. In contrast, the separation start timing can be set after the trailing edge of the image forming area on the photosensitive drum 2 has finished passing through the development nip G, and before the trailing edge of the area corresponding to the sheet S on the photosensitive drum 2 has finished passing through the development nip G.

[0153] Similarly, if it can be determined, for example, based on image information, that an image will not be formed in the area at the rear end of the sheet S, then the separation start timing for the area at the rear end where no image is formed can be set before the image rear end timing t_pe. In other words, the separation start timing can be set after the rear end of the area where the image is formed in the image forming area on the photosensitive drum 2 has finished passing through the developing nip G, and before the rear end of the area on the photosensitive drum 2 corresponding to the sheet S has finished passing through the developing nip G. For example, the control unit 150 can determine the leading edge of the area at the rear end of the sheet S where no image is formed (the rear end of the area where the image is formed) based on the image information of the print signal received from the video controller 160. Then, for example, the control unit 150 can change the separation start timing to be before the image rear end timing t_pe based on the position information of this leading edge of the area at the rear end of the sheet S where no image is formed (the rear end of the area where the image is formed).

[0154] Furthermore, even if the powder pressure becomes "0" and the amount of toner carried on the surface of the developing roller 51 decreases, a predetermined amount of time is required before the density of the toner image on the photosensitive drum 2 decreases as a result. This predetermined time is at least the time required for the surface of the developing roller 51, whose amount of toner has decreased due to the reduction in powder pressure, to rotate from the contact position with the regulating plate 542 to the contact position with the photosensitive drum 2 (developing nip G). Therefore, in the rotational direction of the developing roller 51, it is acceptable to set the separation start timing before the image trailing edge timing t_pe, at least for the phase difference from the contact position between the developing roller 51 and the regulating plate 542 to the contact position between the developing roller 51 and the photosensitive drum 2. The same applies when setting the separation start timing to correspond to the margin or the area on the trailing edge side of the sheet S where no image is formed, as described above. In other words, in the rotational direction of the developing roller 51, the phase difference from at least the contact position between the developing roller 51 and the regulating plate 542 to the contact position between the developing roller 51 and the photosensitive drum 2 allows the separation start timing to be set earlier than when the rear end of the image forming area on the photosensitive drum 2 has finished passing the developing nip G, or when the rear end of the area where the image is formed in the image forming area on the photosensitive drum 2 has finished passing the developing nip G. The separation start timing may also be a timing between the timing when the rear end of the image forming area on the photosensitive drum 2 has finished passing the developing nip G (or the timing when the rear end of the area where the image is formed has finished passing the developing nip G) and a timing that is the above phase difference earlier.

[0155] In this way, the timing of approach start and separation start can be appropriately set in relation to the development period in order to sufficiently suppress whiteout and density unevenness.

[0156] Furthermore, in this embodiment (and the other examples described above according to the present invention), the phase of the holding shaft 522 was set to the first phase d1 at the drive start timing t_ds and the drive stop timing t_de. In other words, in this embodiment (and the other examples described above according to the present invention), the first state of the supply sheet 521 in Figure 5 is the initial state of the supply sheet 521, and the corresponding first phase d1 of the holding shaft 522 is the initial state of the holding shaft 522. However, the present invention is not limited to such embodiments. For example, in the example of Figure 20(d), the phase of the holding shaft 522 is set to the second phase d2 at the drive start timing t_ds and the drive stop timing t_de. In this case, for example, the phase of the holding shaft 522 is set to the first phase d1 before the start of the development period, and the supply sheet 521 is set to a first state in which the deflection is relatively large. Then, during the development period, the supply sheet 521 is gradually brought closer to the surface of the developing roller 51. This makes it possible to suppress white spots and density unevenness, similar to this embodiment (and the other examples described above according to the present invention).

[0157] Furthermore, in the control of this embodiment (Figure 18(c)) and its modified example (Figure 20), the method of changing the phase of the holding shaft 522 (linear, stepwise, curved, etc.), the setting of the approach start timing and separation start timing, and the initial state of the holding shaft 522 can be arbitrarily combined.

[0158] <Effects> As described above, according to this embodiment and its modifications, toner can be stably supplied to the surface of the developing roller 51, and the occurrence of image defects such as white spots and density unevenness can be suppressed. In order to stably supply toner to the supply surface 51a of the developing roller 51 and suppress the occurrence of image defects such as white spots and density unevenness, it is important to maintain sufficient powder pressure on the surface of the developing roller 51 during the development period. For this reason, as described above, assuming that the toner around the developing roller 51 will slightly aggregate as the developing roller 51 rotates, it is desirable to control the supply mechanism 52 to bias the toner toward the surface of the developing roller 51 during the development period. Furthermore, it is desirable to control the supply mechanism 52 so that the powder pressure does not decrease even temporarily during the development period.

[0159] Conventionally, developing machines are equipped with a supply roller that supplies toner to the developing roller. The properties of the toner contained in the developing machine change as the developing machine is repeatedly used, such as its electrostatic properties and fluidity. When the fluidity of the toner decreases, image defects such as uneven density and white spots may occur. In other words, when the fluidity of the toner decreases, even if there is a sufficient amount of toner contained in the developing machine, the amount of toner contained in the sponge layer of the supply roller decreases, which can cause the amount of toner supplied to the developing roller to become unstable. This can result in "uneven density," where the density (amount of toner) of a part of the image corresponding to the area where the amount of toner supplied to the developing roller has decreased decreases. Also, if the amount of toner supplied to the developing roller decreases significantly, "white spots," where parts of the image are missing, may occur. Furthermore, if the electrostatic properties of the toner decrease, "fogging," where toner adheres to non-image areas where it is not desirable for toner to adhere, may occur. Factors that cause such changes in the properties of the toner include the toner being subjected to friction and other loads at the contact points between the developing roller and the supply roller.

[0160] According to this embodiment and its modified form, compared to a configuration in which a supply roller is provided on the developing unit 50, it is possible to reduce changes in the performance of the toner contained in the developing container 53 while suppressing the occurrence of image defects such as white spots and density unevenness. According to the inventors' studies, according to this embodiment and its modified form, compared to a configuration in which a supply roller is provided on the developing unit 50, the rate at which the fluidity of the toner decreases with respect to the total number of rotations of the developing roller 51 can be reduced to about 25%.

[0161] As mentioned above, the toner supported on the surface of the developing roller 51 is approximately 1 to 10 layers thick, and the thickness of the toner layers that move in the direction of arrow F1 as the developing roller 51 rotates is estimated to be slightly less than 100 μm at most. Furthermore, the toner wall formed near the surface of the developing roller 51, as explained using Figures 12 and 13, is formed at a distance of approximately 100 μm from the surface of the developing roller 51. Therefore, when the supply sheet 521 biases the toner in the supply area 53g, it is sufficient to bias at least this 100 μm gap. In this embodiment and its modified form, for example, as shown in Figure 17, when the supply sheet 521 is brought closer to the surface of the developing roller 51, the holding shaft 522 is rotated by approximately 30° from the initial state shown by the dotted line. However, if the 100 μm gap can be sufficiently biased when the supply sheet 521 biases the toner in the supply area 53g, this rotation angle may be smaller. This rotation angle can be appropriately selected from, for example, 5 to 90 degrees, with 10 to 60 degrees being preferable, and typically around 20 to 45 degrees.

[0162] Furthermore, the time required to return the phase of the holding shaft 522 from the second phase d2 to the first phase d1 can be adjusted by the spring constant of the biasing spring 593, and can be set appropriately in consideration of the strength of the holding shaft 522 and the time required for processes after the development period.

[0163] Furthermore, in monochrome image mode, by keeping the developing rotary 100 in the developing position shown in Figure 2(c) and not rotating the rotary body 90, multiple images for multiple pages to be transferred to multiple sheets S can be formed in a shorter time and more images can be formed. In this case, as with the example in Figure 18(c), the phase of the holding axis 522 can be returned to the first phase d1 after each page's development period is completed. For example, when forming two pages' worth of images to be transferred to two sheets S, the following can be done. That is, as with the example in Figure 18(c), when the development period for the first page is completed, the phase of the holding axis 522 is returned from the second phase d2 to the first phase d1, and then changed again from the first phase d1 to the second phase d2 during the development period for the second page. Alternatively, when the development period for the first page is completed, the phase of the holding axis 522 may be left at the second phase d2. Furthermore, during the development period for the second page, the phase of the holding axis 522 may be changed to a third phase (third holding axis position) d3, which brings the supply sheet 521 even closer to the surface of the developing roller 51 than the second phase d2. Also, similar to the example in Figure 20(b), in monochrome image mode, the phase of the holding axis 522 may be continuously changed so that the supply sheet 521 continues to be brought closer to the surface of the developing roller 51 while the developing roller 51 is rotating. In this case, the phase of the holding axis 522 may be returned to the first phase each time a predetermined number of pages (for example, 2 to 10 pages) of development period is completed. Note that the monochrome image mode is generally a mode in which a black monochrome image is formed with black toner, but it may also be a mode in which a monochrome image of another color is formed.

[0164] As described above, in this embodiment, the image forming apparatus 1 includes a rotatable image carrier (photosensitive drum) 2 that carries a toner image, and a developing apparatus (developing unit) 50 that forms a toner image on the surface of the image carrier 2, the developing apparatus 50 comprising a developing container 53 for containing toner, and a rotatable developer carrier (developing roller) 51 that contacts the surface of the image carrier 2 to form a developing section (developing nip) G, carries the toner contained in the developing container 53 and transports it toward the image carrier 2. Furthermore, in this embodiment, the image forming apparatus 1 is capable of changing between a first state and a second state in which at least a portion is closer to the surface of the developer carrier 51 than in the first state. The apparatus includes a supply mechanism 52 equipped with a supply member (supply sheet) 521 that biases the toner contained in the developing container 53 toward the surface of the developer carrier 51 when it changes from the first state to the second state, a drive unit (supply member drive unit) 176 that can operate the supply mechanism 52 to change the state of the supply member 521 between the first state and the second state, and a control unit 150 that controls the drive unit 176. In this embodiment, the first timing is defined as the timing when the leading edge of the image carrier 2 in the rotational direction of the image forming region on the image carrier, where a toner image for one page can be formed, reaches the developing unit G. The second timing is defined as a timing that has a predetermined relationship with the timing when the rear end of the image carrier 2 in the rotational direction of the image forming region has finished passing through the developing unit G. The period between the first timing and the second timing is defined as a predetermined period. The control unit 150 controls the drive unit 176 so that, for at least a portion of the predetermined period, the supply mechanism 52 operates to change the state of the supply member 521 from a first state to a second state, and so that the supply mechanism 52 does not operate to change the state of the supply member 521 from a second state to a first state during the predetermined period. The second timing may be the timing when the rear end of the image carrier 2 in the rotational direction of the image forming region has finished passing through the developing unit G.Furthermore, the developing device 50 may have a regulating member (regulating blade) 54 that contacts the surface of the developer carrier 51 to form a contact portion and regulates the amount of toner carried on the developer carrier 51. The second timing may be earlier than the timing at which the rear end of the image carrier 2 in the rotational direction of the image forming region has finished passing through the developing unit G by the amount of time it takes for the surface of the developer carrier 51 to move from the contact portion to the developing unit G. In this embodiment, when the image forming region is called the first image forming region, the predetermined period is called the first period, and the period between the first timing and the second timing with respect to the second image forming region on the image carrier in which the next page of toner image can be formed is called the second period, the control unit 150 controls the drive unit 176 to operate the supply mechanism 52 which changes the state of the supply member 521 in the direction from the second state to the first state after the first period and before the second period.

[0165] In this embodiment, the supply member 521 is made of a flexible sheet in which the first direction (longitudinal direction) is arranged along the rotation axis direction of the developer carrier 51 (approximately parallel in this embodiment), and a first portion (fixed portion) 521a on one end and a second portion (joint portion) 521b on the other end are held in the second direction (short direction) which intersects (approximately perpendicular in this embodiment) with the first direction. The supply mechanism 52 has a holding member (holding shaft) 522 that holds the second portion 521b of the supply member 521 and is rotatable about the rotation axis along the first direction (approximately parallel in this embodiment). The drive unit 176 can change the state of the supply member 521 between a first state and a second state by rotating the holding member 522. In this embodiment, the first portion 521a of the supply member 521 is held by the developing container 53. Furthermore, in this embodiment, the supply member 521 is capable of changing between a first state in which it has deflection in the second direction and a second state in which the deflection is smaller than that of the first state. Also, in this embodiment, the supply member 521 forms a first region (supply region) 53g inside the developing container 53 that houses the developer carrier 51 and a second region (back side region) 53d that does not house the developer carrier 51, and the image forming apparatus 1 has a moving means that enables the movement of toner between the first region 53g and the second region 53d. In this embodiment, the image forming apparatus 1 has a rotary (rotary body) 90 that can rotate the developing apparatus 50, and the moving means enables the movement of toner between the first region 53g and the second region 53d by rotating the rotary 90.

[0166] Furthermore, according to this embodiment, it is possible to stably supply toner to the surface of the developer carrier without providing a supply roller in the developing device.

[0167] [Example 2] Next, other embodiments of the present invention will be described. In this embodiment, other examples of the configuration of the supply mechanism 52 and the drive configuration of the supply mechanism 52 will be described. In this embodiment, the present invention is applied to an image forming apparatus 1 with a basic configuration similar to that of Embodiment 1.

[0168] <Other examples of supply mechanisms> First, let's describe another example of the supply mechanism 52.

[0169] In Example 1, the supply mechanism 52 was configured to rotate the joint portion 521b of the supply sheet 521 around the rotation center 522C of the holding shaft 522. In contrast, the supply mechanism 52 may be configured to swing the joint portion 521b of the supply sheet 521.

[0170] Figure 21 is a schematic cross-sectional view of another example of the developing unit 50, which includes another example of the supply mechanism 52. Figure 22 is a schematic perspective view of another example of the holding shaft 522 of the supply mechanism 52. Figures 22(a), (b), and (c) show examples of the holding shaft 522, respectively, and Figure 21 shows the developing unit 50 with the holding shaft 522 shown in Figure 22(a). The holding shaft 522 shown in Figure 22 also shows the joining portion 521b of the supply sheet 521 for joining the supply sheet 521 to the holding shaft 522.

[0171] As shown in Figures 21 and 22(a), the holding portion 5221 of the holding shaft 522 may have a substantially rectangular cross-section in the XZ plane. This holding shaft 522 can rotate (rotate) in the direction of arrow R7a (clockwise) and arrow R7b (counterclockwise) about a rotation axis 522C extending in the Y axis direction. In this holding shaft 522, the rotation axis 522C is positioned towards one end in the longitudinal direction of the holding shaft 522 in the XZ plane. Also, in this holding shaft 522, the joint portion 521b of the supply sheet 521 is joined at a position away from the rotation axis 522C in the holding portion 5221 in the rotational radius direction of the holding shaft 522. In other words, the joint portion 521b of the supply sheet 521 is joined to the end surface (the surface extending longitudinally in the XZ plane) opposite to the end side where the rotation axis 522C is located, in the longitudinal direction of the holding portion 5221 in the XZ plane. As a result, when the holding shaft 522 is rotated about the rotation axis 522C, the joint portion 521b of the supply sheet 521 swings in the directions of arrows R7a and R7b with the rotation axis 522C as the pivot point. By configuring the joint portion 521b of the supply sheet 521 to swing in this way, it becomes possible to control the slack of the supply sheet 521 by rotating the holding shaft 522 by a smaller angle. In this case as well, the degree of deflection of the supply sheet 521 can be adjusted, and the toner in the supply area 53g can be biased toward the surface of the developing roller 51.

[0172] Furthermore, the retaining shaft 522 may have a protruding portion, as shown in Figure 22(b), by cutting out a portion of the retaining shaft 522 shown in Figure 22(a). In addition, the retaining shaft 522 may have a crank shape, as shown in Figure 22(c), by cutting out a portion of the retaining shaft 522 shown in Figure 22(a). For example, by using a material with sufficient strength for the retaining shaft 522 and configuring it as shown in Figures 22(b) and 22(c), the amount of material used can be reduced. Even with such a configuration, the joint portion 521b of the supply sheet 521 can be oscillated with the rotation axis 522C as the pivot point, and the toner in the supply area 53g can be biased toward the surface of the developing roller 51.

[0173] The supply mechanism 52, which includes the holding shaft 522 shown in Figures 21 and 22, is driven by the same drive configuration as in Embodiment 1.

[0174] <Other examples of drive configurations for supply mechanisms> Next, we will describe other examples of the drive configuration of the supply mechanism 52.

[0175] Figures 23 and 24(a) are schematic exploded perspective views illustrating other examples of the drive configuration of the supply mechanism 52. Figure 23 shows a holding shaft 522 and a rotating assist member 571, which is an example of a rotating assist member (moving member). Figure 24(a) shows a supply mechanism 52 and a rotating assist member 572, which is another example of a rotating assist (moving member). Figure 24(b) is a cross-sectional view of the rotating assist member 572 shown in Figure 24(a). Figure 24(c) is a graph showing the change in radius r of the cam portion 5721 (cam profile), which will be described later, in the rotational direction of the rotating assist member 572 shown in Figure 24(a). The holding shaft 522 shown in Figures 23 and 24(a) also shows the joint portion 521b of the supply sheet 521 for joining the supply sheet 521 to the holding shaft 522.

[0176] The holding portion 5221 of the holding shaft 52 shown in Figures 23 and 24(a) has a main portion 5221b with a substantially square cross-section in the XZ plane, similar to the holding portion 5221 in Embodiment 1 (Figure 7). The holding shaft 52 is provided with a protruding portion 5221a that extends outward from the main portion 5221b in the radial direction of rotation of the holding shaft 522.

[0177] The rotating shaft portion 5222 of the holding shaft 52 shown in Figures 23 and 24(a) does not have the notch 5222a for transmitting driving force to the holding shaft 522 that was provided in the rotating shaft portion 5222 (Figure 7) in Embodiment 1, and is cylindrical in shape. In other words, the holding shaft 522 shown in Figures 23 and 24(a) is not powered by a member such as the supply member gear 591 (Figure 8) in Embodiment 1, but is rotated around the rotation axis 522C by a rotation assist member 571 or rotation assist member 572, which will be described later.

[0178] Furthermore, the rotating shaft portion 5222 shown in Figures 23 and 24(a) is capable of having a biasing spring 5731 attached. In the configuration shown in Figures 23 and 24(a), the biasing spring 5731 is attached to the rotating shaft portion 5222 on the negative Y-axis side, but it may also be attached to the rotating shaft portions 5222 at both ends in the Y-axis direction. The biasing spring 5731 is made of a torsion coil spring and has an engaging portion 5731a at one end and a held portion 5731b at the other end. The biasing spring 5731 is positioned to cover the periphery of the rotating shaft portion 5222. When the biasing spring 5731 is attached to the rotating shaft portion 5222, the engaging portion 5731a of the biasing spring 5731 is engaged with the protrusion 5221a of the holding shaft 52. On the other hand, the held portion 5731b of the biasing spring 5731 is held by a holding portion (not shown) provided on the developing container 53.

[0179] The rotating assist member 571 shown in Figure 23 has a plate-shaped paddle portion 5711 and a cylindrical rotating shaft portion 5712. The rotating assist member 571 is attached to the developing container 53 by the rotating shaft portions 5712, which are provided at both ends in the Y-axis direction, being rotatably supported in support holes (not shown) provided at both ends of the developing container 53 in the Y-axis direction. The rotating assist member 571 is rotatable in the direction of arrow R9 (counterclockwise) about the rotation axis 571C extending in the Y-axis direction by engaging a rotating assist member drive gear (not shown) with a notch 5712a provided in the rotating shaft portion 5712. Furthermore, the rotating assist member 571 has four paddle portions 5711 arranged radially around the rotation axis 571C such that its cross-section in the XZ plane is approximately cross-shaped. Note that in Figure 23, for explanatory purposes, the holding shaft 522 and the rotating assist member 571 are shown separated along the dashed line in the figure. However, the retaining shaft 522 and the rotation assist member 571 are positioned such that the protrusion 5221a of the retaining shaft 52 and the paddle portion 5711 of the rotation assist member 571 can engage with each other. Therefore, by rotating the rotation assist member 571 in the direction of arrow R9, a driving force is transmitted to the retaining shaft 522 via the protrusion 5221a of the retaining shaft 52, causing the retaining shaft 522 to rotate in the direction of arrow R7a (clockwise) around the rotation axis 522C. At this time, elastic energy is stored in the biasing spring 5731. When the rotation assist member 571 rotates further in the direction of arrow R9, the paddle portion 5711 of the rotation assist member 571 and the protrusion 5221a of the retaining shaft 522 are no longer engaged. Then, due to the elastic energy stored in the biasing spring 5731, the retaining shaft 522 rotates in the direction of arrow R7b (counterclockwise).

[0180] The rotation assist member 572 shown in Figure 24(a) has a cam portion 5721 and a cylindrical rotating shaft portion 5722. The rotation assist member 572 is attached to the developing container 53 by the rotating shaft portions 5722, which are provided at both ends in the Y-axis direction, being rotatably supported in support holes (not shown) provided at both ends of the developing container 53 in the Y-axis direction. Similar to the rotation assist member 571 shown in Figure 23, the rotation assist member 572 is rotatable in the direction of arrow R9 (counterclockwise) about a rotation axis 572C extending in the Y-axis direction by engaging a rotation assist member drive gear (not shown) with a notch 5722a provided in the rotating shaft portion 5722. The cam portion 5721 has a loose portion 5721a and a bent portion 5721b, as shown in Figure 24(b). Furthermore, as shown in Figure 24(c), the loosening portion 5721a is configured such that when the rotation assist member 572 rotates in the direction of arrow R9, the radius r at the contact position with the holding shaft 522 increases linearly from r1 to r2. Also, as shown in Figure 24(c), the bending portion 5721b is configured such that when the rotation assist member 572 rotates in the direction of arrow R9, the radius r at the contact position with the holding shaft 522 returns from r2 to r1 (decreases linearly) at a greater incline than that of the loosening portion 5721a (but in the opposite direction). Note that in Figure 24(a), for explanatory purposes, the holding shaft 522 and the rotation assist member 572 are shown separated along the dashed line in the figure. However, the holding shaft 522 and the rotation assist member 572 are arranged so that the protrusion 5221a of the holding shaft 52 and the cam portion 5721 of the rotation assist member 572 can contact each other.

[0181] With this configuration, rotating the rotation assist member 572 in the direction of arrow R9 causes the holding shaft 522 to rotate in accordance with the change in radius r of the cam portion 5721 as shown in Figure 24(c). That is, by rotating the rotation assist member 572 in the direction of arrow R9, the loose portion 5721a of the rotation assist member 572 comes into contact with the protruding portion 5221a of the holding shaft at a predetermined timing. Subsequently, by further rotating the rotation assist member 572 in the direction of arrow R9, the rotation radius of the rotation assist member 572 (loose portion 5721a) at the contact position with the holding shaft 572 increases, and the rotation assist member 572 gradually biases the protruding portion 5221a of the holding shaft 572 in the direction of arrow R7a. As a result, the holding shaft 522 rotates about the rotation axis 522C in the direction of arrow R7a (clockwise). At that time, elastic energy is accumulated in the biasing spring 5731. Subsequently, when the rotation assist member 572 is rotated further in the direction of arrow R9, the bent portion 5721b of the rotation assist member 572 reaches a position where it contacts the protruding portion 5221a of the holding shaft 572, and the cam portion 5721 and the protruding portion 5221a of the holding shaft 572 no longer come into contact. Then, due to the elastic energy stored in the biasing spring 5731, the holding shaft 522 rotates in the direction of arrow R7b (counterclockwise).

[0182] Furthermore, the driving force for the rotating auxiliary member drive gear is transmitted from the developing drive gear via the supply member clutch mechanism, similar to the driving configuration of the holding shaft 522 in Embodiment 1.

[0183] By using the drive configuration shown in Figures 23 and 24, the holding shaft 522 can be rotated in both the direction of arrow R7a and arrow R7b with a simpler configuration than the drive configuration in Embodiment 1 (Figure 8). On the other hand, the rotation assist members 571 and 572 occupy a certain volume in the space inside the developing container 53. Therefore, when using the drive configuration shown in Figures 23 and 24, the volume available for storing toner in the developing container 53 is reduced compared to when using the drive configuration in Embodiment 1 (Figure 8). For example, the drive configuration of the supply mechanism 52 can be appropriately selected in view of these factors.

[0184] In the examples shown in Figures 23 and 24, the paddle portion 5711 of the rotating assist member 571 and the cam portion 5721 of the rotating assist member 572 extended over substantially the entire area of ​​the rotating assist members 571 and 572 in the Y-axis direction, respectively. Similarly, in the examples shown in Figures 23 and 24, the projection 5221a of the holding shaft 52 extended over substantially the entire area of ​​the holding shaft 52 in the Y-axis direction. However, the present invention is not limited to such configurations. For example, the rotating assist members 571 and 572 and the holding shaft 52 may be made of materials with sufficient strength, and they may be provided only in a part of the Y-axis direction. Alternatively, they may be divided into multiple sections in the Y-axis direction.

[0185] Furthermore, in order to facilitate the transmission of drive to the protruding portion 5221a of the holding shaft 52, a further protruding portion may be provided on at least one of the protruding portion 5221a and the paddle portion 5711. Also, in order to reduce the torque of the rotation assist members 571 and 572, a roller member such as a roller may be provided on the holding shaft 522, for example. In addition, any other configuration may be used as long as the driving force can be transmitted directly to the holding portion 5221 of the holding shaft 52 without going through the rotating shaft portion 5222 of the holding shaft 52, as can be done with the rotation assist members 571 and 572.

[0186] Furthermore, in the example shown in Figure 24, the cam portion 5721 of the rotation assist member 572 was shaped such that the radius r of the slow-moving portion 5721a increased linearly as shown in Figure 24(c). However, the present invention is not limited to such configurations. As explained in Example 1, if it is possible to control the supply mechanism 52 to bias the toner toward the surface of the developing roller 51 during the developing period, the shape of the cam portion 5721 can be set as appropriate, for example, the cross-section may be elliptical or egg-shaped. Also, as rotation assist members 571 and 572, any configuration can be used as long as the distance from the rotation axis 571C, 572C to the contact portion with the holding shaft 522 can be changed. For example, as shown in Figure 22 as an example of the shape of the holding shaft 522, a rectangular cross-section, a shape with a protruding part cut out, or a crank shape may be used as rotation assist members 571 and 572.

[0187] <Configuration that allows the holding axis to slide> Figure 25 is a schematic cross-sectional view of another example of a developing unit 50, which has a drive configuration for a supply mechanism 52 configured to slide a holding shaft 522. As shown in Figure 25, the developing unit 50 may be configured such that the holding shaft 522 slides (reciprocates) in the direction of arrow S1a (towards the developing roller 51) and the direction of arrow S2b (away from the developing roller 51). In each figure, the direction of arrow S1a indicates the direction of movement that changes the supply sheet 521 from a state of relatively large deflection (first state) to a state of relatively small deflection (second state). Also in each figure, the direction of arrow S1b indicates the direction of movement that changes the supply sheet 521 from a state of relatively small deflection (second state) to a state of relatively large deflection (first state).

[0188] As a configuration that allows the retaining shaft 522 to move in both the direction of arrow S1a and arrow S1b, for example, a configuration using a gear with missing teeth and a biasing spring, as described with reference to Figure 8, can be used. Alternatively, a configuration as described next with reference to Figure 26 may also be used.

[0189] Figure 26 is a schematic exploded perspective view of the retaining shaft 522 and the biasing shaft 574 (described later) to illustrate the drive configuration of the supply mechanism 52, which is configured to allow the retaining shaft 522 to slide (reciprocate). The retaining shaft 522 shown in Figure 26 also shows the joint portion 521b of the supply sheet 521 for joining the supply sheet 521 to the retaining shaft 522.

[0190] The basic configuration of the retaining shaft 522 shown in Figure 26 is the same as that of the retaining shaft 522 in Embodiment 1 (Figure 7). However, the retaining shaft 522 shown in Figure 26 is attached to the developing container 53 by the fact that the supported portions 5223 provided at both ends in the Y-axis direction are movably supported in support holes 5342 provided at both ends of the developing container 53 in the Y-axis direction. The support holes 5342 extend along the directions of arrows S1a and S1b, and the retaining shaft 522 is movable along the directions of arrows S1a and S1b. A sealing member (not shown) is provided in the support holes 5342 to prevent toner leakage.

[0191] Another example of a moving member shown in Figure 26, the biasing shaft 574, has a cam portion 5741 and a cylindrical rotating shaft portion 5742, similar to the rotation assist member 572 described using Figure 24, and is rotatable in the direction of arrow R9 (counterclockwise) about a rotation axis 574C extending in the Y-axis direction. Furthermore, the cam portion 5741 of this biasing shaft 5744 has a loosening portion 5742a and a bent portion 5742b, similar to the cam portion 5721 of the rotation assist member 572 described using Figures 24(b) and (c). The loosening portion 5742a and bent portion 5742b of this cam portion 5741 have the same shape as those described using Figures 24(b) and (c).

[0192] In Figure 26, for illustrative purposes, the holding shaft 522 and the biasing shaft 574 are shown separated along the directions of arrows S1a and S1b, as indicated by the dashed lines in the figure. However, the holding shaft 522 and the biasing shaft 574 are arranged so that the holding portion 5221 of the holding shaft 52 and the cam portion 5741 of the biasing shaft 574 can come into contact with each other. Furthermore, at both ends in the Y-axis direction, notches 5223a are provided in the supported portion 5223 of the holding shaft 52. Similarly, at both ends in the Y-axis direction, notches 5742a are provided in the rotating shaft portion 5742 of the biasing shaft 574. At both ends in the Y-axis direction, one end and the other end of a biasing spring 5732, which is composed of a tension coil spring, are attached to these notches 5223a and 5742a, respectively. As a result, the holding shaft 522 and the biasing shaft 574 are biased to pull each other (towards each other).

[0193] The biasing shaft 574 is driven by a drive configuration similar to that of the rotational assist member 572 in the configurations shown in Figures 23 and 24, through which driving force is transmitted via a biasing shaft drive gear (not shown).

[0194] With this configuration, rotating the biasing shaft 574 in the direction of arrow R9 causes the retaining shaft 522 to slide in accordance with the change in radius r of the cam portion 5741, similar to that described using Figure 24(c). That is, when the biasing shaft 574 is at a rotation angle near 0° as shown in Figure 24(c), the retaining shaft 522 is closest to the rotation axis 574C of the biasing shaft 574. Then, rotating the biasing shaft 574 in the direction of arrow R9 increases the rotation radius of the biasing shaft 574 (loosening portion 5741a) at the contact position with the retaining shaft 572, causing the biasing shaft 574 to bias the retaining shaft 522 in the direction of arrow S1a. As a result, the retaining shaft 522 slides in the direction of arrow S1a. At that time, elastic energy is accumulated in the biasing spring 5732. Subsequently, when the biasing shaft 574 is rotated further in the direction of arrow R9, the bent portion 5741b of the biasing shaft 574 reaches a contact position with the holding shaft 522, and the elastic energy stored in the biasing spring 5732 causes the holding shaft 522 to slide in the direction of arrow S1b.

[0195] In this way, the holding shaft 522 can be slid (reciprocated) in both the direction of arrow S1a (towards the developing roller 51) and the direction of arrow S1b (away from the developing roller 51). In this case as well, as the holding shaft 522 moves back and forth between the state shown by the solid line in Figure 25 (first holding shaft position) and the state shown by the dashed line (second holding shaft position), the supply sheet 521 moves back and forth between the state shown by the solid line in Figure 25 (first state, first supply sheet position) and the state shown by the dashed line (second state, second supply sheet position). This allows the toner in the supply area 53g to be biased toward the surface of the developing roller 51. Furthermore, in the configuration where the holding shaft 522 slides, the holding shaft 522 (i.e., the fixing portion 521b of the supply sheet 521) is moved to a predetermined position. This makes it easier to control the amount by which the supply sheet 521 is brought closer to the surface of the developing roller 51 and the amount by which the supply sheet 521 is moved away from the developing roller 51, compared to the case where the holding shaft 522 is rotated as described above.

[0196] As with the case of the rotation assist member 574 explained using Figure 24, the shape of the cam portion 5741 of the biasing shaft 574 is not limited to the shape shown in Figure 26. As long as it is possible to control the supply mechanism 52 to bias the toner toward the surface of the developing roller 51 during the developing period, as explained in Example 1, the shape of the cam portion 5741 can be changed as appropriate. Also, the biasing shaft 574 may be paddle-shaped, for example, like the rotation assist member 571 explained using Figure 23. Furthermore, as with the cases of the rotation assist members 571 and 572, the portion of the biasing shaft 574 that acts on the holding shaft 52 (cam portion or paddle portion) may be provided only in a part of the Y-axis direction, or it may be divided into multiple parts in the Y-axis direction.

[0197] Furthermore, as shown in Figure 25, a configuration in which the holding shaft 522 is moved in the direction of arrow S1a and in the direction of arrow S1b, which is 180° opposite to the direction of arrow S1a, has been described. However, the trajectory of the movement of the holding shaft 522 is not limited to being a straight line; for example, it may be configured to bend or to draw an arc. Also, the sliding direction is not limited to the direction shown in Figure 25; it may be a direction along the X-axis (for example, approximately parallel) as long as it can bring the supply sheet 521 closer to and further away from the surface of the developing roller 51.

[0198] Thus, the supply mechanism 52 may have a holding member (holding shaft) 522 that holds the second portion (joint portion) 521b of the supply member 521 and is slidable along a direction intersecting the first direction (the direction along the rotation axis of the developer carrier 51), and the drive unit 176 may be able to change the state of the supply member 521 between a first state and a second state by sliding the holding member 522.

[0199] <Another configuration that slides the holding axis> As shown in Figure 25, another example of a configuration in which the retaining shaft 522 slides in the direction of arrows S1a and S1b will be described. Figure 27(a) is a schematic perspective view of the slide assist member 575, which will be described later, to illustrate another example of the drive configuration of the supply mechanism 52 configured to slide the retaining shaft 522, and also shows surrounding members such as the retaining shaft 522. Figure 27(b) is a schematic plan view of the outer circumferential surface of the slide assist member 575, which will be described later.

[0200] The slide assist member 575 is an axial member having a cam portion 5751 and a rotating shaft portion 5752. This slide assist member 575 is attached to the developing container 53 by being rotatably supported by a side cover (not shown) attached to the Y-axis minus side of the developing container 53. The rotating shaft portion 5752 has a notch 5752a, and a slide assist member drive gear (not shown) is engaged with this notch 5752a. As a result, the slide assist member 575 is rotatable in the direction of arrow R10 (counterclockwise when viewed in the direction of arrow S1a) about a rotation axis 575C which is substantially parallel to the directions of arrows S1a and S1b. The cam portion 5751 is a barrel cam having a groove portion 5751a, and this groove portion 5751a engages with the supported portion 5223 on the Y-axis minus side of the holding shaft 522. This allows the retaining shaft 522 to slide in the direction of arrow S1a and arrow S1b, following the cam portion 5751.

[0201] In the cam portion 5751, the protrusion on the upstream side in the direction of arrow S1a (downstream side in the direction of arrow S1b) relative to the groove portion 5751a is defined as the first protrusion 5751b. In the cam portion 5751, the protrusion on the downstream side in the direction of arrow S1a (upstream side in the direction of arrow S1b) relative to the groove portion 5751a is defined as the second protrusion 5751c. Furthermore, as shown in Figure 27(b), the groove portion 5751a has a gently sloping section 5751a1 with respect to the direction of arrow R10, and a bent section 5751a2 with respect to the direction of arrow R10, but in the opposite direction to the gently sloping section 5751a1.

[0202] Furthermore, one end of a biasing spring 5732, which is made of a tension coil spring, is attached to a notch 5223a provided in the supported portion 5223 on the Y-axis negative side of the holding shaft 52. In addition, a support projection 535 is provided on the developing container 53, located upstream in the direction of arrow S1a (downstream in the direction of arrow S1b) relative to the support hole portion 5342. The other end of the biasing spring 5732 is attached to this support projection 535. The support projection 535 is provided with a barb portion 535a that protrudes toward the upstream side in the direction of arrow S1a (downstream in the direction of arrow S1b), preventing the biasing spring 5732 from falling off the support projection 535. The holding shaft 522 is biased in the direction of arrow S1b by this biasing spring 5732.

[0203] With this configuration, when the supported portion 5223 is engaged with the loose portion 5751a1 (Figure 27(b)), the slide assist member 575 rotates in the direction of arrow R10, causing the holding shaft 522 to slide in the direction of arrow S1a. At this time, elastic energy is stored in the biasing spring 5732. Subsequently, when the supported portion 5223 engages with the bent portion 5751a2 (Figure 27(b)), the holding shaft 522 is biased in the direction of arrow S1b by the biasing spring 5732 and slides in the direction of arrow S1b.

[0204] In this way, the holding shaft 522 can be moved in both the direction of arrow S1a and the direction of arrow S1b. In this case as well, as the holding shaft 522 moves back and forth between the state shown by the solid line in Figure 25 (first holding shaft position) and the state shown by the dashed line (second holding shaft position), the supply sheet 521 moves back and forth between the state shown by the solid line in Figure 25 (first state, first supply sheet position) and the state shown by the dashed line (second state, second supply sheet position). This allows the toner in the supply area 53g to be biased toward the surface of the developing roller 51. Furthermore, by using a slide assist member 575 as shown in Figure 27, even in a configuration in which the holding shaft 522 is slid, the space inside the developing container 53 can be used more widely, similar to the configuration of Embodiment 1 (Figure 8), and the amount of toner that can be filled can be increased.

[0205] Note that the configuration of the slide assist member 575 is not limited to the configuration shown in Figure 27. For example, the retaining shaft 522 is always biased in the direction of arrow S1b by the biasing spring 5732. As a result, the supported portion 5223 of the retaining shaft 522 moves in contact with the interface between the first protrusion 5751b and the groove 5751a at the cam portion 5751 of the slide assist member 575. Therefore, the second protrusion 5751c in the configuration shown in Figure 27 may be omitted, and the portion corresponding to the second protrusion 5751c may be made to the same height (radius of rotation) as the groove 5751a. Alternatively, for example, a rail-shaped protrusion may be provided on the outer circumferential surface of the cam portion 5751 of the slide assist member 575, and a member that engages with this protrusion may be provided on the retaining shaft 522.

[0206] [Example 3] Next, other embodiments of the present invention will be described. In this embodiment, a member that supports the supply sheet 521 by contacting the surface between the fixing portion 521a and the joining portion 521b of the supply sheet 521 will be described. In addition, in this embodiment, in addition to the case in which the present invention is applied to an image forming apparatus 1 with a basic configuration similar to that of Embodiment 1, the case in which the present invention is applied to an image forming apparatus 1 with a basic configuration different from that of Embodiment 1 will also be described.

[0207] <Example of a suspension axis> Figure 28 is a schematic cross-sectional view of an example of the developing unit 50 of this embodiment. In the configuration shown in Figure 28, the supply mechanism 52 comprises a supply sheet 521, a holding shaft 522, and a suspension shaft 523, which is a support member (suspension member) that abuts against the surface between the fixing portion 521a and the joint portion 521b of the supply sheet 521 and supports the supply sheet 521. In the configuration shown in Figure 28, the suspension shaft 523 is made of a cylindrical rod with a substantially circular cross-section in the XZ plane. This suspension shaft 523 is arranged so that its longitudinal direction is along the Y axis direction. Furthermore, this suspension shaft 523 is attached to the developing container 53 by being supported by support holes (not shown) provided at both ends of the developing container 53 in the Y axis direction. This suspension shaft 523 abuts against the surface of the supply sheet 521 facing the back side region 53d. By rotating the holding shaft 522 in the direction of arrow R7a or arrow R7b, the amount of deflection of the portion of the supply sheet 521 on the fixed portion 521a side of the suspension shaft 523 can be changed.

[0208] In this configuration as in Example 1, rotating the holding shaft 522 in the direction of arrow R7a (counterclockwise direction) brings the supply sheet 521 closer to the surface of the developing roller 51, thereby biasing the toner in the supply area 53g toward the surface of the developing roller 51. Furthermore, by configuring the supply sheet 521 to be pulled or returned via the suspension shaft 523, the degree of freedom in the arrangement of the supply sheet 521 and the holding shaft 522, as well as the degree of freedom in the configuration of the supply sheet 521 and the holding shaft 522, can be increased.

[0209] <Other examples of suspension shafts> Furthermore, the developing unit 50 may be configured to control the approach and separation movements of the supply sheet 521 from the surface of the developing roller 51 by controlling the movement of the movable suspension shaft 523.

[0210] Figure 29 is a schematic cross-sectional view of another example of the developing unit 50 of this embodiment. In the configuration shown in Figure 29, the suspension shaft 523 is made of a rod with a substantially elliptical cross-section in the XZ plane. Similar to the suspension shaft 523 in the configuration shown in Figure 28, this suspension shaft 523 is positioned so that its longitudinal direction is along the Y-axis direction. Furthermore, this suspension shaft 523 is attached to the developing container 53 by the fact that the rotating shaft portions (not shown) provided at both ends in the Y-axis direction are supported by support holes (not shown) provided at both ends of the developing container 53 in the Y-axis direction. This suspension shaft 523 is in contact with the surface of the supply sheet 521 facing the back side region 53d. In the configuration shown in Figure 29, the suspension shaft 523 is configured to rotate in the direction of arrow R11 (clockwise) around a rotation axis 523C extending in the Y-axis direction, by a driving force transmitted to the suspension shaft 523 from a suspension shaft drive gear (not shown) that engages with the suspension shaft 523. In this case, as the suspension shaft 523 rotates in the direction of arrow R11, the supply sheet 521 can change between a first state (supply sheet first position, separated state) shown by a solid line in Figure 29 and a second state (supply sheet second position, approached state) shown by a dashed line. The first state of the supply sheet 521 is a state in which the deflection is relatively large (the largest in this example), and the second state of the supply sheet 521 is a state in which the deflection is relatively small (the smallest in this example). In this case, the phase of the suspension shaft 523 when the supply sheet 521 is in the first state is the first phase (first position of the suspension shaft), and the phase of the suspension shaft 523 when the supply sheet 521 is in the second state is the second phase (second position of the suspension shaft). In this example, the suspension shaft 523 goes through the first phase and the second phase twice each during one rotation. This allows the toner in the supply area 53g to be biased toward the surface of the developing roller 51.

[0211] Furthermore, the drive force to the suspension shaft drive gear is transmitted from the developing drive gear via a clutch mechanism, similar to the drive configuration of the holding shaft 522 in Embodiment 1.

[0212] In this way, the function of moving the supply sheet 521 closer to and further away from the surface of the developing roller 51 can be provided to a component other than the holding shaft 522. This increases the degree of freedom in the arrangement of the supply sheet 521 and the holding shaft 522 in the space formed by the developing container 53, as well as the degree of freedom in the configuration of the supply sheet 521 and the holding shaft 522. The supply sheet 521 can be moved closer to and further away from the surface of the developing roller 51 by operating at least one (or both) of the holding shaft 522 and the suspension shaft 523.

[0213] Here, for example, in a configuration where the suspension shaft 523 controls the approach and separation movements of the supply sheet 521 from the surface of the developing roller 51, as shown in Figure 29, a mechanism for rotating the holding shaft 522 is not particularly necessary. Therefore, the holding shaft 522 may be configured to swing around the rotation axis 522C, or it may be fixed to the developing container 53 so as not to rotate. Furthermore, as will be explained next with reference to Figure 30, the joint portion 521b of the supply sheet 521 is not limited to being fixed to the holding shaft 522.

[0214] Figure 30 is a schematic cross-sectional view of another example of the developing unit 50 of this embodiment. As shown in Figure 30, the joint 521b of the supply sheet 521 may be fixed to the inner wall of the developing container 53 instead of the holding shaft 522. In this case, the supply mechanism 52 is configured to have a supply sheet 521 and a suspension shaft 523, but does not have a holding shaft 523. In this case as well, the toner in the supply area 53g can be biased toward the surface of the developing roller 51 by controlling the approach and separation movements of the supply sheet 521 from the surface of the developing roller 51 using the suspension shaft 523.

[0215] In the configuration in which the suspension shaft 523 controls the approaching and moving away movements of the supply sheet 521 from the surface of the developing roller 51, the cross-sectional shape of the suspension shaft 523 in the XZ plane is not limited to the shapes shown in Figures 29 and 30. For example, the cross-sectional shape may be rectangular, oval, or a cross-sectional shape such as that of the rotating assist member 572 described using Figure 24. Furthermore, the configuration in which the suspension shaft 523 controls the approaching and moving away movements of the supply sheet 521 from the surface of the developing roller 51 is not limited to a configuration in which the suspension shaft 523 rotates. For example, the suspension shaft 523 may be slid by a mechanism using a biasing shaft 574 described using Figure 26 or a sliding assist member 575 described using Figure 27. In addition, any configuration may be used instead of the suspension shaft 523 as long as it is possible to control the supply mechanism 52 to bias the toner toward the surface of the developing roller 51 during the developing period. For example, the state of the supply sheet 521 may be controlled using an actuator that can move back and forth, or a balloon-like member whose volume can be changed by the inflow and outflow of air. Furthermore, the state of the supply sheet 521 may be controlled by directly inflowing and outflowing air into the rear side region 53d.

[0216] Thus, the supply mechanism 52 may have a support member (suspension shaft) 523 that supports the supply member 521 between the first part (fixing part) 521a and the second part (joint part) 521b in a second direction (a direction intersecting the rotation axis direction of the developer carrier 51). The supply mechanism 52 may also have a movable support member 523, and the drive unit 176 may be able to change the state of the supply member 521 between a first state and a second state by operating the support member 523. Furthermore, the support member 523 may be rotatable about a rotation axis along the first direction (a direction along the rotation axis direction of the developer carrier 51), or slidable along a direction intersecting the first direction.

[0217] <Supply sheet sealing member> Furthermore, the suspension shaft 523 is not limited to being located at a position away from the inner wall of the developing container 53, as shown in Figures 28 to 30.

[0218] Figure 31 is a schematic cross-sectional view of another example of the developing unit 50 of this embodiment. In the configuration shown in Figure 31, the suspension shaft 524 is positioned near the inner wall of the developing container 53. The suspension shaft 523 in the configuration shown in Figure 31 is the same as that in the configuration shown in Figure 28. A supply sheet sealing member 563 is also provided on the inner wall of the developing container 53. The supply sheet sealing member 563 has a base layer made of flexible sponge and an adhesive layer, and is fixed to the inner wall of the developing container 53 by bonding the adhesive layer to the inner wall of the developing container 53. The supply sheet 521 is held between this supply sheet sealing member 563 and the suspension shaft 523. This seals the gap between the supply sheet 521 and the inner wall of the developing container 53, thereby preventing toner from flowing into the back side region 53d. In this case as well, the degree of deflection of the supply sheet 521 can be adjusted by rotating the holding shaft 522.

[0219] Furthermore, in the configuration shown in Figure 31, where the supply sheet sealing member 563 suppresses toner leakage into the back side region 53d, it is not necessary to consider processing the toner that has leaked into the back side region 53d by rotating the rotary body 90, as explained using Figure 9. In other words, the developing unit 50 with the configuration shown in Figure 31 can also be used in an image forming apparatus 1 with a different basic configuration than the rotary developing type image forming apparatus 1 shown in Figure 1, as will be explained next.

[0220] <Other examples of image forming apparatus> Figure 32 is a schematic cross-sectional view of another example of the image forming apparatus 1. Figure 33 is a schematic cross-sectional view of the developing unit 50 used in the image forming apparatus 1 shown in Figure 32.

[0221] The image forming apparatus 1 shown in Figure 32 is a tandem-type color laser printer employing an intermediate transfer method that can form a full-color image on a sheet S using an electrophotographic method. This image forming apparatus 1 includes multiple process cartridges Cy, Cm, Cc, and Ck, a scanner 4, an intermediate transfer unit 10, a secondary transfer roller 12, a fuser 40, and the like. Each process cartridge Cy, Cm, Cc, and Ck has a photosensitive drum 2, a charging roller 3, a developing unit 50, and a photosensitive drum cleaning unit 6, respectively. The process cartridges Cy, Cm, Cc, and Ck are detachably attached to the main body 1a of the image forming apparatus as a single unit. Each process cartridge Cy, Cm, Cc, and Ck has substantially the same configuration except for the color of the toner contained in the developing unit 50. The developing unit 50 of the yellow, magenta, cyan, and black process cartridges Cy, Cm, Cc, and Ck contains the respective toners of yellow, magenta, cyan, and black, respectively. The intermediate transfer unit 10 includes an intermediate transfer belt 10a and primary transfer rollers 11y, 11m, 11c, 11k, etc., which are provided corresponding to each photosensitive drum 2. Each primary transfer roller 11y, 11m, 11c, 11k forms a primary transfer nip N1y, N1m, N1c, N1k. The secondary transfer roller 12 forms a secondary transfer nip N2. In this image forming apparatus 1, the toner images of each color formed on the photosensitive drum 2 in each process cartridge Cy, Cm, Cc, Ck are primary transferred by each primary transfer nip N1 so as to be sequentially superimposed onto the intermediate transfer belt 10a. This toner image formed on the intermediate transfer belt 10a is secondary transferred onto the sheet S by the secondary transfer nip N2 and fixed onto the sheet S by the fixing device 40.

[0222] Furthermore, as shown in Figure 33, the developing unit 50 provided in the image forming apparatus 1 shown in Figure 32 has the same configuration as the developing unit 50 shown in Figure 31. In the supply mechanism 52 provided in this developing unit 50, the fixing portion 521a of the supply sheet 521 is fixed to the inner wall of the developing container 53, the joining portion 521b is joined to the holding shaft 522, and the surface between the fixing portion 521a and the joining portion 521 is supported by the suspension shaft 523. The supply sheet 521 is then held between the supply sheet sealing member 563 provided on the inner wall of the developing container 53 and the suspension shaft 523.

[0223] Even in this configuration, by rotating the holding shaft 522 in the direction of arrow R7a, the toner present in the supply area 53g can be biased toward the surface of the developing roller 51. Therefore, toner can be stably supplied to the surface of the developing roller 51 while reducing changes in the performance of the toner contained in the developing unit 50.

[0224] It should be noted that the configuration of the image forming apparatus 1 that can use the developing unit 50 with the configuration shown in Figure 31 is not limited to the configurations shown in Figures 1 and 32. For example, the developing unit 50 with the configuration shown in Figure 31 can also be used in an image forming apparatus that uses a build-up type developing unit 50, which will be described later in Example 6, or in a black monochrome image forming apparatus that uses magnetic toner.

[0225] [Example 4] Next, other embodiments of the present invention will be described. In Embodiments 1 to 3, a configuration was described in which the holding shaft 522 moves back and forth between a first phase d1 and a second phase d2, which are specific phases, and the supply sheet 521 moves back and forth between a first state and a second state. In contrast, the holding shaft 522 may not only move back and forth between predetermined phases, but may also be able to wind up the supply sheet 521 as needed. This makes it possible to change the phase in which the holding shaft 522 moves back and forth, for example, according to the amount of toner contained in the developing container 53. In this embodiment, the present invention will be described as being applied to an image forming apparatus 1 with a basic configuration similar to that of Embodiment 1, but it can also be applied to an image forming apparatus 1 with the configuration shown in Figure 32, which was described in Embodiment 3.

[0226] <Other examples of controlling the holding axis> Figure 34 is a schematic cross-sectional view of an example of the developing unit 50 of this embodiment. Figure 34(a) shows a state in which the amount of toner contained in the developing container 53 is relatively large, and Figure 34(b) shows a state in which the amount of toner contained in the developing container 53 has decreased from the state shown in Figure 34(a).

[0227] In the state shown in Figure 34(a) where there is a large amount of toner, the phase of the holding shaft 522 is controlled so that the supply sheet 521 alternates between the first state shown by the solid line and the second state shown by the dashed line during the image forming operation. Subsequently, as the image forming operation is repeated and the amount of toner in the developing container 53 decreases, the surface area of ​​the toner in the developing container 53 becomes lower in the state of the supply sheet 521 shown in Figure 34(a). In other words, the area of ​​the developing roller 51 that is supplied with toner and comes into contact with it decreases.

[0228] In contrast, as shown in Figure 34(b), the volume of the supply area 53g can be reduced by rotating the holding shaft 522 by a predetermined amount in the direction of arrow R7a and winding the supply sheet 521 onto the holding shaft 522 by a predetermined amount. This makes it possible to maintain a sufficiently high toner surface in the developing container 53 even when the amount of toner contained in the developing container 53 decreases, thereby suppressing a reduction in the opportunity for the toner to come into contact with the surface of the developing roller 51.

[0229] Then, as shown in Figure 34(b), the state in which the supply sheet 521 is wound up by a predetermined amount by rotating the holding shaft 522 is set as the reference for the phase of the holding shaft 522 when controlling the phase of the holding shaft 522 in the image forming operation. In other words, in the state shown in Figure 34(b), the phase of the holding shaft 522 is controlled in the image forming operation so that the supply sheet 521 moves back and forth between the third state (reference state) shown by the solid line and the fourth state shown by the dashed line. The third state of the supply sheet 521 is the state in which the deflection is relatively large when the supply sheet 521 is wound up by a predetermined amount on the holding shaft 522, and the fourth state of the supply sheet 521 is the state in which the deflection is relatively small in that case. In this case, the phase of the holding shaft 522 when the supply sheet 521 is in the third state is the third phase (third position of the holding shaft), and the phase of the holding shaft 522 when the supply sheet 521 is in the fourth state is the fourth phase (fourth position of the holding shaft).

[0230] This configuration allows the toner surface in the developing container 53 to maintain a predetermined height, i.e., the opportunity for the toner to contact the surface of the developing roller 51, even when the amount of toner contained in the developing container 53 changes. Furthermore, the supply mechanism 52 can be controlled to bias the toner toward the surface of the developing roller 51 during the developing period.

[0231] Any available means can be used to determine the amount of toner contained in the developing container 53. For example, the control unit 150 counts the time (number of pixels) during which the photosensitive drum 2 is irradiated with laser light when an image is formed, and stores information regarding the count result in a storage unit (such as a memory attached to the developing unit 50 (not shown)). The control unit 150 can then determine the amount of toner in the developing container 53 (toner remaining amount or toner used amount) based on this information (such as the integrated value of the number of pixels). Alternatively, a light-receiving window that transmits light may be provided in the developing container 53, and the amount of toner in the developing container 53 may be determined based on the transmittance of light irradiated toward this light-receiving window. Alternatively, a conductive sheet material may be provided on the inner wall of the developing container 53, and the amount of toner in the developing container 53 may be determined based on the current value flowing between this sheet material and the developing roller 51. Furthermore, the amount of toner in the developing container 53 may be determined based on the torque when the holding shaft 522 is rotated. Alternatively, the amount of toner in the developing container 53 may be determined based on the density of a predetermined test pattern transferred to the intermediate transfer belt 10a. For example, a density sensor for detecting the amount of toner transferred to the intermediate transfer belt 10a can be provided in the intermediate transfer unit 10 or the like. Alternatively, as explained using Figure 18(b), for example, a predetermined test pattern is formed without the supply sheet 521 approaching the surface of the developing roller 51. Then, the amount of toner in the developing container 53 can be determined based on whether or not the density of the test pattern transferred to the intermediate transfer belt 10a satisfies predetermined conditions. That is, if the amount of toner contained in the developing container 53 decreases and the opportunity for toner to contact the surface of the developing roller 51 decreases as described above, white spots as shown in Figure 18(b3) are more likely to occur in the test pattern. By detecting this with the density sensor, the amount of toner in the developing container 53 can be determined. The control unit 150 can set and control the operation of the holding shaft 522 based on the detection result from the detection means for detecting the amount of toner contained in the developing container 50 as described above.

[0232] Furthermore, in the state shown in Figure 34(b), the developing unit 50 may be provided with a mechanism to prevent the holding shaft 522 from returning to the state shown in Figure 34(a) by the biasing spring 593 explained with reference to Figure 8. For example, the supply member gear 591 may be provided with a claw-shaped part as a stopper to stop the holding shaft 522 from rotating by more than a predetermined amount in the direction of arrow R7b. Alternatively, for example, an electromagnetic clutch may be used to control the holding shaft 522 from rotating by more than a predetermined amount in the direction of arrow R7b. With such a configuration, for example, when toner is supplied to the developing container 53, the electromagnetic clutch can be controlled to allow the holding shaft 522 to rotate beyond the predetermined amount in the direction of arrow R7b. This makes it possible to return the holding shaft 522 to the state where the supply sheet 521 is not wound around it, as shown in Figure 34(a).

[0233] Furthermore, the phase difference of the holding axis 522 that changes during image formation (for example, the difference between the first phase d1 and the second phase d2) may be changed according to the amount of toner contained in the developing container 53. For example, in light of the decrease in fluidity due to the deterioration of toner caused by repeated use of the developing unit 50, the phase difference when the amount of toner in the developing container 53 is small can be controlled to be larger than the phase difference when the amount of toner in the developing container 53 is large. Also, the amount of phase change with respect to time (for example, the slope when the phase changes linearly from the first phase d1 to the second phase d2) may be changed according to the amount of toner contained in the developing container 53. For example, in light of the same reason as above, the amount of phase change with respect to time when the amount of toner in the developing container 53 is small can be controlled to be larger than the amount of phase change with respect to time when the amount of toner in the developing container 53 is large. This may allow for more appropriate control of the biasing of the toner on the surface of the developing roller 51 according to the amount of toner contained in the developing container 53. Furthermore, at least one of the following can be changed according to the amount of toner contained in the developing container 50: the reference phase of the moving phase of the holding shaft 522, the phase difference between phases, and the amount of phase change with respect to time.

[0234] Furthermore, while we have described setting the reference phase for the movement of the holding shaft 522 according to the amount of toner contained in the developing container 53, it may also be set according to other conditions. For example, as mentioned above, the fluidity of the toner may decrease when the developing unit 50 is used repeatedly or when the image forming apparatus 1 is used in a low-temperature environment. Therefore, the reference phase for the movement of the holding shaft 522 may be set according to changes in the cumulative amount used in the developing unit 50 or changes in the operating environment of the image forming apparatus 1, such as temperature and humidity. The same applies to the phase difference between phases of the holding shaft 522 and the amount of phase change with respect to time. These can be set based on information stored in the memory provided in the developing unit 50, the detection results of the temperature and humidity sensor, etc.

[0235] <Other examples of developing units according to this embodiment> In this embodiment as well, as described in Embodiment 2, the configuration of the supply mechanism 52 and the drive configuration of the supply mechanism 52 can be appropriately selected. For example, in this embodiment as well, the developing unit 50 may have a configuration in which the holding shaft 522 swings or slides.

[0236] Furthermore, in this embodiment as well, as described in Embodiment 3, the supply mechanism 52 may be configured to have a suspension shaft 523. Figure 35 is a schematic cross-sectional view of another example of the developing unit 50 of this embodiment. The supply mechanism 52 provided in this developing unit 50 has the same configuration as shown in Figure 34, but it has a suspension shaft 523. The suspension shaft 523 in the configuration shown in Figure 35 is the same as the one in the configuration shown in Figure 28. In the configuration shown in Figure 35, the suspension shaft 523 is provided to abut against the surface of the supply sheet 521 that faces the supply area 53g. Thus, the surface of the supply sheet 521 that the suspension shaft 523 abuts against can be appropriately set according to the configuration of the supply mechanism 52.

[0237] Furthermore, as described in Example 3, the state of the supply sheet 521 during image formation may be controlled by the suspension shaft 523, or by an actuator or a balloon-shaped member. In that case, as described with reference to Figure 30, the fixing portion 521a and the joint portion 521b of the supply sheet 521 may be fixed to the inner wall of the developing container 53.

[0238] Furthermore, if the reference phase of the moving phase of the holding shaft 522, the phase difference between phases, or the amount of phase change with respect to time are to be changed due to changes in the amount of toner in the developing container 53 as described above, these may also be controlled by a balloon-shaped member or the like.

[0239] <The supply sheet also serves as a pre-use sealing component.> Furthermore, the developing unit 50 may be configured such that the supply sheet 521 also serves as a pre-use sealing member that seals the toner into the developing container 53 before the developing unit 50 is put into use (when not in use).

[0240] Figure 36 is a schematic cross-sectional view of another example of the developing unit 50 of this embodiment. Figure 36(a) shows the developing unit 50 in the state before use begins, and Figure 36(b) shows the developing unit 50 in the state ready for image formation after the initial setup control described later has been completed.

[0241] The developing unit 50 shown in Figure 36 has a similar configuration to that shown in Figure 35, but differs in that the length between the fixing portion 521a and the joining portion 521b of the supply sheet 521 is different, and the supply sheet 521 is configured to also serve as a pre-use sealing member.

[0242] As shown in Figure 36(a), in the state before the development unit 50 is put into use, the supply sheet 521 is positioned along the inner wall of the development container 53, extending from a fixed portion 521a fixed to the inner wall of the development container 53, across the suspension shaft 523 and the holding shaft 522, passing near the development roller 51, extending to the surface near the fixed portion 521a, then folded back and extended to the holding shaft 522, where it is joined to the holding shaft 522 at the joint portion 521b. In addition, the supply sheet 521 is bonded to the surface near the fixed end portion 521a of the supply sheet 521 at the adhesive portion (third portion) 521 provided in the folded portion. In this way, a part of the supply sheet 521 and another part of the supply sheet 521 are bonded at the adhesive portion 521 (i.e., the supply members are fixed to each other), forming a filling region 53e, which is a space surrounded by the supply sheet 521. Toner T is then filled into this filling region 53e. This allows the toner T to be sealed inside the developing container 53 in the sealing portion 521d between the adhesive portion 521 and the holding shaft 522, where the supply sheet 521 is folded back and doubled.

[0243] Here, the contact strength between a part of the supply sheet 521 and other parts of the supply sheet 521 at the adhesive portion 521e (i.e., between sheets) is set to be weaker than the adhesive strength between the supply sheet 521 and the inner wall of the developing container 53 at the fixing portion 521a. Therefore, in the initial setup control of the developing unit 50, the adhesive portion 521e can be peeled off (fixed) by rotating the holding shaft 522 in the direction of arrow R7a and winding up the supply sheet 521 with the holding shaft 522. After that, by winding up the portion of the supply sheet 521 that was used as the sealing portion 521d with the holding shaft 522, it becomes possible to supply toner to the developing roller 51 as shown in Figure 36(b). For example, the control unit 150 can detect that the developing unit 50 is unused (new) based on usage history information stored in the storage unit (such as a memory attached to the developing unit 50 (not shown)). The control unit 150 can then control the system to execute the initial setup control when it detects that the developing unit 50 is unused (new).

[0244] Thus, before the development device 50 is put into use, the supply members are fixed together in the third part (adhesive part) 521e between the first part (fixing part) 521a and the second part 521b in the second direction (a direction intersecting the rotation axis direction of the developer carrier 51), and toner is contained in the area surrounded by the supply members 521. The control unit 150 may be configured to control the drive unit 176 so that when the development device 50 is put into use, the holding member 522 winds up the supply members 521, thereby releasing the fixation in the third part 521e and making it possible to supply the toner contained in the surrounded area to the developer carrier 51.

[0245] Even with this configuration, the supply mechanism 52 can be controlled to bias the toner toward the surface of the developing roller 51 during the developing period. Therefore, the member that seals the toner and the member that supplies the toner to the developing roller 51 can be combined into a single component.

[0246] <Further examples of developing units according to this embodiment> Figure 37 is a schematic cross-sectional view of yet another example of the developing unit 50 of this embodiment. As shown in Figure 37, the retaining shaft 522 may be provided outside the developing container 53. In that case, a sealing valve 564 may be provided in the developing container 53, and the supply sheet 521 may be clamped by this sealing valve 564. This prevents toner from leaking out of the developing container 53. With this configuration, the space inside the developing container 53 becomes larger by the volume previously occupied by the retaining shaft 522, allowing more toner to be filled.

[0247] [Example 5] Next, other embodiments of the present invention will be described. In embodiments 1 to 4, a configuration was described in which a supply mechanism 52 equipped with a flexible supply sheet 521 as the supply section was used. In contrast, the developing unit 50 may be configured to be equipped with a supply member having a predetermined rigidity that does not substantially deform during operation.

[0248] FIG. 38(a) is a schematic cross-sectional view of an example of the developing unit 50 of this embodiment, and FIG. 38(b) is a schematic cross-sectional view of another example of the developing unit 50 of this embodiment. The developing unit 50 shown in FIGS. 38(a) and 38(b) has a supply plate 524 as a supply member. The supply plate 524 has a predetermined rigidity that does not substantially deform during operation. In this embodiment, the supply plate 524 is composed of a plate-like member made of polystyrene resin. However, the material of the supply plate 524 is not limited to this, and other resin materials or metal materials such as SUS may be used. The supply plate 524 is arranged such that its longitudinal direction is along the Y-axis direction. The length of the supply plate 524 in the longitudinal direction is set to be approximately the entire length of the region inside the developing container 53 in the Y-axis direction.

[0249] The supply plate 524 is supported by the developing container 53 so as to be swingable about a swing shaft 5241 extending in the Y-axis direction provided at one end in the short direction substantially orthogonal to the longitudinal direction of the supply plate 524. In this embodiment, the supply plate 524 is arranged to be swingable in the directions of arrow R11a and arrow R11b about the swing shaft 5241 supported by the developing container 53. Here, in the configuration shown in FIG. 38(a), the swing shaft 5241 is provided at the end of the supply plate 524 on the lower side in the vertical direction (Z-axis minus side). On the other hand, in the configuration shown in FIG. 38(b), the swing shaft 5241 is provided at the end of the supply plate 524 on the upper side in the vertical direction (Z-axis plus side). In each figure, the direction of arrow R11a indicates the moving direction in which at least a part of the supply plate 524 approaches the surface of the developing roller 51. Also, in each figure, the direction of arrow R11b indicates the moving direction in which at least a part of the supply plate 524 moves away from the surface of the developing roller 51.

[0250] Furthermore, in the configuration shown in Figure 38(a), a biasing shaft 576, which is a movable member capable of contacting the supply plate 524, is arranged inside the developing container 53. This biasing shaft 576 is a cam member having the same configuration as the biasing shaft 574 described using Figure 26. However, in the configuration shown in Figure 38(a), the biasing shaft 576 has a configuration that is inverted left and right in the XZ plane compared to the biasing shaft 574 described using Figure 26. This biasing shaft 576 is driven by a biasing shaft drive gear (not shown) and can rotate in the direction of arrow R12 (clockwise) around a rotation axis 576C extending in the Y axis direction. By rotating the biasing shaft 576 in the direction of arrow R12, the supply plate 524 is gradually swung (rotated) in the direction of arrow R11a. Then, as shown by the dashed line in the figure, after bringing the feed plate 524 closer to the surface of the developing roller 51, the biasing shaft 576 is further rotated in the direction of arrow R12, causing the feed plate 524 to temporarily move away from the biasing shaft 576. Then, due to gravity acting in the negative Z-axis direction, the feed plate 524 swings (rotates) in the direction of arrow R11b.

[0251] On the other hand, in the configuration shown in Figure 38(b), the developing unit 50 is provided with a biasing spring (not shown) as a biasing member that biases the feed plate 524 in the direction of arrow R11b. In addition, a biasing shaft 577 is arranged inside the developing container 53 as a movable member that can contact the feed plate 524. This biasing shaft 577 is a cam member having the same configuration as the suspension shaft 523 described using Figure 30. This biasing shaft 577 is driven by a biasing shaft drive gear (not shown) and can rotate in the direction of arrow R13 (clockwise) around a rotation axis 577C extending in the Y-axis direction. By rotating the biasing shaft 577 in the direction of arrow R13, the feed plate 524 is gradually swung (rotated) in the direction of arrow R11a. Then, as shown by the dashed line in the figure, after bringing the supply plate 524 closer to the surface of the developing roller 51, the biasing shaft 576 is further rotated in the direction of arrow R13, causing the supply plate 524 to swing (rotate) in the direction of arrow R11b, biased by the biasing spring.

[0252] Thus, the driving unit 176 may have a moving member 756 (or 577) disposed inside the developing container 53 so as to be able to contact the supply member 521, and by operating to bring the moving member into contact with the supply member 524, it may be possible to change the state of the supply member 524 between a first state and a second state.

[0253] Even with such a configuration, the supply plate 524 can be controlled so as to urge toner toward the surface of the developing roller 51 during the developing period. In the configurations of FIGS. 38(a) and (b), the supply plate 524 moves back and forth between the state shown by the solid line in the figure (first state, supply plate first position) and the state shown by the two-dot chain line (second state, supply plate second position). Thereby, the toner in the supply area 53g can be urged toward the surface of the developing roller 51.

[0254] In addition, in the configuration shown in FIG. 38(a) as well, an urging member for urging the supply plate 524 in the direction of arrow R11b may be provided, similar to the configuration shown in FIG. 38(b).

[0255] Further, the supply plate 524 is provided with a bent portion 524a bent so as to be convex toward the side opposite to the developing roller 51. Thereby, the surface of the supply plate 524 has a shape along the circumferential surface of the developing roller 51, and it becomes easier to urge the toner in the supply area 53g toward the developing roller 51. Note that a plurality of bent portions 524a may be provided. Also, the supply plate 524 may have a curved shape that forms an arc convex toward the side opposite to the surface of the developing roller 51.

[0256] In addition, in the configuration shown in FIG. 38(a), rotation prevention protrusions 536 are provided on the inner walls on both sides of the developing container 53 in the Y-axis direction. The rotation prevention protrusions 536 are disposed so as to be able to contact the supply plate 524, and prevent the supply plate 524 from falling unintentionally toward the developing roller 51 side.

[0257] Furthermore, it is not necessary to provide holes in the supply plate 524 in this embodiment. The supply plate 524 in this embodiment is configured to bias the toner in the supply area 53g toward the surface of the developing roller 51. Therefore, if holes are provided in the supply plate 524, the toner in the supply area 53g will escape through the holes to the rear side area 53d. For this reason, it is desirable not to provide holes in the supply plate 524. However, if the toner can be sufficiently biased toward the surface of the developing roller 51, slits or the like may be provided in the supply plate 524.

[0258] Figure 39 is a schematic perspective view of another example of the oscillating plate 524. This oscillating plate 524 is provided with a pivot shaft 5241 at its upper vertical end (positive Z-axis side), similar to the configuration shown in Figure 38(b). This supply plate 524 is also provided with a positioning slit 5242 at its lower vertical end (negative Z-axis side). In this case, the developing container 53 is provided with a positioning projection 537 that can engage with the positioning slit 5242 of the oscillating plate 524. The positioning projection 537 and the positioning slit 5242 define the position of the supply plate 524 in the Y-axis direction. Even in this configuration, the toner can be biased toward the surface of the developing roller 51 by oscillating the supply plate 524 in the direction of arrow R11a.

[0259] Furthermore, paddle-shaped biasing shafts 576 and 577, as shown in Figure 23, may be used. Also, as means for biasing the supply plate 524, actuators or balloon-shaped members, as described in Example 3, may be used.

[0260] In this way, by controlling the supply plate 524 to bias the toner toward the surface of the developing roller 51 during the developing period, toner can be supplied stably to the developing roller 51, and the occurrence of image defects such as white spots and density unevenness can be suppressed. Furthermore, if the developing unit 50 is to be used for a long period of time, it can be expected that the performance will be maintained for a longer period of time when using the supply plate 524 compared to when using the supply sheet 521.

[0261] [Example 6] Next, other embodiments of the present invention will be described. In this embodiment, the present invention will be described in the case where it is applied to an image forming apparatus 1 with a different basic configuration from that of Embodiment 1 (an image forming apparatus 1 using an assembly-type developing unit 50).

[0262] Figure 40 is a schematic cross-sectional view of another example of the image forming apparatus 1 using a pump-type developing unit 50. Figure 41 is a schematic cross-sectional view of a portion of the pump-type developing unit 50, magnified.

[0263] The image forming apparatus 1 shown in Figure 40 uses an electrophotographic method to create full-color images on a sheet S. This is a tandem-type color laser printer that employs an intermediate transfer method capable of image formation and uses a build-up type developing unit 50. This image forming apparatus 1 has multiple process cartridges Cy, Cm, Cc, Ck, a scanner 4, an intermediate transfer unit 10, a secondary transfer roller 12, a fixing unit 40, etc. Each process cartridge Cy, Cm, Cc, and Ck has a photosensitive drum 2, a charging roller 3, a developing unit 50, and a photosensitive drum cleaning unit 6, respectively. The process cartridges Cy, Cm, Cc, and Ck are detachably attached to the main body 1a of the image forming apparatus as a single unit. Each process cartridge Cy, Cm, Cc, and Ck has substantially the same configuration except for the color of the toner contained in the developing unit 50. The developing unit 50 of the yellow, magenta, cyan, and black process cartridges Cy, Cm, Cc, and Ck contains the respective toners of yellow, magenta, cyan, and black, respectively. The intermediate transfer unit 10 includes an intermediate transfer belt 10a and primary transfer rollers 11y, 11m, 11c, and 11k, which are provided corresponding to each photosensitive drum 2. Each primary transfer roller 11y, 11m, 11c, and 11k forms a primary transfer nip N1y, N1m, N1c, and N1k. The secondary transfer roller 12 forms a secondary transfer nip N2. This image forming apparatus 1 forms an image on the sheet S in the same manner as the image forming apparatus 1 shown in Figure 32.

[0264] As shown in Figures 40 and 41, in this embodiment, the developing container 53 of the developing unit 50 has a toner chamber 53f, which is a space on the lower vertical side (negative Z-axis side), and a supply area 53g, which is a space on the upper vertical side (positive Z-axis side). Toner is contained in the toner chamber 53f, and the toner is supplied from this toner chamber (first chamber) 53f to the supply area (second chamber) 53g by being pumped up. Thus, the developing unit 50 in this embodiment is a pump-type developing unit 50.

[0265] A stirring member 578 is provided inside the toner chamber 53f. The stirring member 578 is composed of a flexible stirring sheet 5781 that abuts against the inner wall of the developing container 53 forming the toner chamber 53f, and a stirring shaft 5782 that can rotate in the direction of arrow R14 (clockwise). The toner chamber 53f and the supply area 53g are separated by a partition 53j. In this embodiment, the partition 53j is composed of a partition wall 53h formed from a part of the developing container 53, and a supply mechanism 52. In other words, in this embodiment, the supply mechanism 52 has a fixing part 521a of the supply sheet 521 fixed to the partition wall 53h, and a joining part 521b joined to the holding shaft 522. The toner chamber 53f and the supply area 53g are in communication via a communication part 53i formed by the holding shaft 522 and the inner wall of the developing container 53. As the stirring member 578 rotates in the direction of arrow R14, the toner in the toner chamber 53f is lifted (bounced up) by the stirring sheet 5781 and transported to the supply area 53g through the communication section 53i. The supply mechanism 52 in this embodiment has the same configuration as that of Embodiment 1. By rotating the holding shaft 522 in the direction of arrow R7a, the toner present in the supply area 53g can be biased toward the surface of the developing roller 51.

[0266] With this configuration, the toner present in the supply area 53g can be biased toward the surface of the developing roller 51 in the assembly-type developing unit 50 with a relatively simple structure. Therefore, toner can be supplied stably to the developing roller 51, and the occurrence of image defects such as white spots and density unevenness can be suppressed.

[0267] In this embodiment, it is preferable to transport the toner from the toner chamber 53f to the supply area 53g by the stirring member 578 at a time other than the development period. This further reduces the possibility of density unevenness occurring.

[0268] [others] Although the present invention has been described above with reference to specific embodiments, the present invention is not limited to the embodiments described above.

[0269] The supply roller used in the developing device takes in toner into the sponge layer once, and the sponge layer is compressed at the contact part with the developing roller to discharge the internal toner and supply it to the developing roller. On the other hand, the supply roller often also has the function of scraping off the toner carried on the surface of the developing roller by the cell wall surface forming the sponge layer of the supply roller. By scraping off the toner carried on the surface of the developing roller in this way, it is possible to suppress charge-up and the like caused by the toner carried on the surface of the developing roller being repeatedly rubbed against the regulating member. In the developing unit described in the above embodiment, a means for scraping off toner from the developing roller can also be provided as necessary. Speaking in accordance with the above embodiment, for example, the following configuration can be adopted. In the rotational direction of the developing roller 51, a scraping member that abuts on the developing roller 51 and scrapes off toner from the developing roller 51 is provided on the downstream side of the contact part between the sealing sheet 561 and the developing roller 51 and on the upstream side of the contact part between the regulating blade 54 and the developing roller 51. Such a scraping member may be provided so as to appropriately supply toner to the developing roller 51 described in the above embodiment. Conventionally, various techniques for removing toner from a developer carrier in a developing device using, for example, magnetic toner have been proposed. In the case of a developing device using magnetic toner, since the configuration is such that the supply of toner to the developer carrier is performed using magnetic force, a supply roller provided in a developing device using non-magnetic toner is not required. Among the means for removing toner on the developer carrier in such a developing device using magnetic toner, those that can be applied to remove non-magnetic toner from the developing roller are suitable for use in the developing unit described in the above embodiment. Therefore, in the developing unit described in the above embodiment, such means may be appropriately selected and used.

Explanation of Signs

[0270] 1 Image forming apparatus 50 Developing unit 51 Developing roller 51a Supplied surface 52 Supply mechanism 53 Developing container 53g supply area 54 Regulatory Blade 70 Toner Cartridges 90 Rotary body 100 Rotary Developing Machine (Rotary Developing Device) 521 Supply Sheet 521a Fixed part 521b Joint 522 Holding axis 523 Hanging shaft

Claims

1. A rotatable image carrier that holds a toner image, A developing apparatus for forming a toner image on the surface of an image carrier, comprising: a developing container for containing toner; and a rotatable developer carrier that contacts the surface of the image carrier to form a developing section, carries the toner contained in the developing container, and transports it toward the image carrier; In an image forming apparatus having, A supply mechanism comprising a supply member that can change between a first state and a second state in which at least a portion is closer to the surface of the developer carrier than in the first state, and which biases the toner contained in the developing container toward the surface of the developer carrier when changing from the first state to the second state, A drive unit capable of operating the supply mechanism to change the state of the supply member between the first state and the second state, It includes a control unit that controls the drive unit, Image forming apparatus characterized in that, when the timing at which the leading edge of the image carrier in the rotational direction of the image carrier reaches the developing unit in an image forming region on the image carrier in which a toner image for one page can be formed is defined as a first timing, the timing at which the trailing end of the image carrier in the rotational direction of the image forming region has finished passing the developing unit is defined as a second timing, and the period between the first timing and the second timing is defined as a predetermined period, the control unit controls the drive unit such that, for at least a portion of the predetermined period, the supply mechanism operates to change the state of the supply member from a first state to a second state, and does not operate the supply mechanism to change the state of the supply member from a second state to a first state during the predetermined period.

2. The image forming apparatus according to claim 1, characterized in that the second timing is the timing at which the rear end of the image carrier in the rotational direction of the image forming region has finished passing the developing section.

3. The developing apparatus has a regulating member that contacts the surface of the developer carrier to form a contact portion and regulates the amount of toner carried on the developer carrier. The image forming apparatus according to claim 1, characterized in that the second timing is earlier than the timing at which the rear end of the image carrier in the rotational direction of the image forming region has finished passing the developing section by the amount of time it takes for the surface of the developer carrier to move from the contact section to the developing section.

4. The image forming apparatus according to claim 1, wherein the image forming region is defined as a first image forming region, the predetermined period as a first period, and the period between the first timing and the second timing with respect to a second image forming region on the image carrier in which a toner image for the next page of the first image forming region can be formed is defined as a second period, the control unit controls the drive unit to perform an operation of the supply mechanism that changes the state of the supply member in the direction from the second state to the first state after the first period and before the second period.

5. The supply member is composed of a flexible sheet in which a first direction is arranged along the rotation axis direction of the developer carrier, and a first portion on one end and a second portion on the other end are held in a second direction intersecting the first direction. The supply mechanism has a holding member that holds the second portion of the supply member and is rotatable about a rotation axis along the first direction, The image forming apparatus according to claim 1, characterized in that the drive unit can change the state of the supply member between the first state and the second state by rotating the holding member.

6. Before the development device is put into use, the supply members are fixed together in the third portion between the first and second portions in the second direction, and toner is contained in the area surrounded by the supply members. The image forming apparatus according to claim 5, characterized in that the control unit controls the drive unit so that when the development apparatus is put into use, the holding member winds up the supply member, thereby releasing the fixation in the third portion and enabling the toner contained in the enclosed area to be supplied to the developer carrier.

7. The supply member is composed of a flexible sheet in which a first direction is arranged along the rotation axis direction of the developer carrier, and a first portion on one end and a second portion on the other end are held in a second direction intersecting the first direction. The supply mechanism has a holding member that holds the second portion of the supply member and is slidable along a direction intersecting the first direction, The image forming apparatus according to claim 1, characterized in that the drive unit can change the state of the supply member between the first state and the second state by sliding the holding member.

8. The image forming apparatus according to any one of claims 5 to 7, characterized in that the supply mechanism has a support member that supports the supply member between the first portion and the second portion in the second direction.

9. The supply member is composed of a flexible sheet in which a first direction is arranged along the rotation axis direction of the developer carrier, and a first portion on one end and a second portion on the other end are held in a second direction intersecting the first direction. The supply mechanism has a movable support member that supports the supply member between the first and second portions in the second direction, The image forming apparatus according to claim 1, characterized in that the drive unit can change the state of the supply member between the first state and the second state by operating the support member.

10. The image forming apparatus according to claim 9, characterized in that the support member is rotatable about a rotation axis along the first direction, or slidable along a direction intersecting the first direction.

11. The image forming apparatus according to any one of claims 5, 7, or 9, characterized in that the supply member is capable of changing between a first state having deflection in the second direction and a second state having less deflection than the first state.

12. The image forming apparatus according to claim 1, wherein the drive unit has a movable member disposed inside the developing container so as to be able to contact the supply member, and by operating the movable member to contact the supply member, the state of the supply member can be changed between a first state and a second state.

13. The supply member provides a first region for housing the developer carrier and a second region for not housing the developer carrier within the developing container. The image forming apparatus according to claim 1, characterized by having a moving means that enables the movement of toner between the first region and the second region.

14. The developing device has a rotary that can rotate it, The image forming apparatus according to claim 13, characterized in that the moving means enables the movement of toner between the first region and the second region by rotating the rotary.

15. A developing container for holding toner, A rotatable developer carrier that holds the toner contained in the developing container, A flexible sheet having a first direction aligned with the rotation axis direction of the developer carrier, and a first portion on one end and a second portion on the other end in a second direction intersecting the first direction, A holding member that holds the second portion of the sheet and is rotatable about a rotation axis along the first direction, It has, The developing apparatus is characterized in that the sheet is capable of changing between a first state and a second state in which at least a portion is closer to the surface of the developer carrier than in the first state, by the rotation of the holding member, and by changing from the first state to the second state, the toner contained in the developing container is biased toward the surface of the developer carrier.

16. Before the development device is put into use, the sheets are fixed together in the third portion between the first and second portions in the second direction, and toner is contained in the area surrounded by the sheets. The developing apparatus according to claim 15, characterized in that when the use of the developing apparatus is started, the sheet is wound up by the holding member, thereby releasing the fixation in the third portion and allowing the toner contained in the enclosed area to be supplied to the developer carrier.

17. A developing container for holding toner, A rotatable developer carrier that holds the toner contained in the developing container, A flexible sheet having a first direction aligned with the rotation axis direction of the developer carrier, and a first portion on one end and a second portion on the other end in a second direction intersecting the first direction, A holding member that holds the second portion of the sheet and is slidable along a direction intersecting the first direction, It has, The developing apparatus is characterized in that the sheet is capable of changing between a first state and a second state in which at least a portion is closer to the surface of the developer carrier than in the first state, by the sliding of the holding member, and by changing from the first state to the second state, the toner contained in the developing container is biased toward the surface of the developer carrier.

18. The developing apparatus according to any one of claims 15 to 17, characterized in that it has a support member that supports the sheet between the first portion and the second portion in the second direction.

19. A developing container for holding toner, A rotatable developer carrier that holds the toner contained in the developing container, A flexible sheet having a first direction aligned with the rotation axis direction of the developer carrier, and a first portion on one end and a second portion on the other end in a second direction intersecting the first direction, A movable support member that supports the sheet between the first and second portions in the second direction, It has, The developing apparatus is characterized in that the sheet is capable of changing between a first state and a second state in which at least a portion of it is closer to the surface of the developer carrier than in the first state, by the operation of the support member, and by changing from the first state to the second state, the toner contained in the developing container is biased toward the surface of the developer carrier.

20. The developing apparatus according to claim 19, characterized in that the support member is rotatable about a rotation axis along the first direction, or slidable along a direction intersecting the first direction.

21. The developing apparatus according to any one of claims 15, 17, or 19, characterized in that the sheet is capable of changing between a first state having deflection in the second direction and a second state having less deflection than the first state.

22. A developing container for holding toner, A rotatable developer carrier that holds the toner contained in the developing container, A supply member capable of biasing the toner contained in the developing container toward the surface of the developer carrier, A movable member is positioned inside the developing container so as to be able to contact the supply member, It has, The developing apparatus is characterized in that the supply member is capable of changing between a first state and a second state in which at least a portion of it is closer to the surface of the developer carrier than in the first state when the moving member comes into contact with it, and the change from the first state to the second state biases the toner contained in the developing container toward the surface of the developer carrier.

Images