Image forming apparatus

Abstract

The present invention provides an image forming apparatus that allows for easy and quick adjustment of the distance between the developing roller and the layer thickness regulating member while suppressing the occurrence of banding and other issues. [Solution] The image forming apparatus 1 comprises a developing unit 10 including a developing roller 11, a doctor blade that regulates the thickness of the developer layer on the surface of the developing roller 11, a drive gear that transmits rotational force to the driven gear of the developing roller 11, and a developing housing 18. The developing unit 10 includes a first eccentric bearing portion 20 that supports the shaft portion 11a of the developing roller 11 and is rotatably mounted on the developing housing 18 such that its center of rotation is eccentric with respect to the shaft portion 11a of the developing roller 11. The first eccentric bearing portion 20 is configured to adjust the DG by rotating relative to the developing housing 18, thereby moving the developing roller 11 in a direction substantially perpendicular to a virtual line VL passing through the center of the drive gear and the center of the driven gear.

Description

Technical Field

[0001] The present disclosure relates to an image forming apparatus, and more particularly to an image forming apparatus capable of easily adjusting the distance between a developing roller and a layer thickness regulating member while suppressing the occurrence of banding and the like.

Background Art

[0002] In an image forming apparatus that forms an image on a recording medium by an electrophotographic method, a developing roller carries a developer agitated in a developing tank on its surface, and toner is supplied from the developer layer on the surface of the developing roller to an electrostatic latent image on a photoreceptor drum to form a toner image. At this time, an excessive developer is scraped off by a layer thickness regulating member provided so as to have a gap from the surface of the developing roller, and the layer thickness of the developer layer on the surface of the developing roller is regulated.

[0003] Since a high accuracy is required for the distance between such a layer thickness regulating member and the developing roller (hereinafter also referred to as "DG"), in the manufacturing process of the image forming apparatus, when fixing the layer thickness regulating member, the adjustment of the screw hole and the screw fixing are manually performed to adjust DG. At present, this is the case. Therefore, since the adjustment of DG requires skilled techniques, there are problems such as large variations due to the adjuster and a large amount of time required.

[0004] Therefore, for example, in Patent Document 1, a developing roller supported by a support shaft, a developer regulating member that regulates the layer thickness of the developer on the developing roller, and a member that is rotatably attached to the support shaft and has a cross-sectional shape in which the distance from the rotation center of the support shaft to the outer peripheral portion continuously changes, and abuts on the developer regulating member to secure a desired distance between the developer regulating member and the developing roller. A developing device provided with a spacer member is disclosed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] In the above-mentioned Patent Document 1, a developer regulating member (layer thickness regulating member), biased toward the developing roller by a compression spring or the like, is brought into contact with the outer circumference of a spacer member whose distance from the rotation center of the support shaft changes continuously, and the DG is adjusted by rotating the spacer member. However, in a mechanism that makes the position of the layer thickness regulating member variable in this way, the fixing strength decreases, which presents a problem in that it becomes difficult to accommodate fine adjustments of the DG, such as ±50μ.

[0007] Therefore, it is conceivable to adjust the DG by making the position of the developing roller variable, but this presents the following problems. Specifically, the developing roller normally rotates when a driven gear, which is attached to its shaft, and a drive gear, which is rotated by a drive source such as a motor, mesh directly or indirectly via a belt or the like. It is known that if there is no backlash (play) between the gears, the gears will not mesh together. For example, when the driven gear and the drive gear are meshed, if they get too close to each other, the backlash becomes too narrow, which hinders the smooth rotation of the developing roller.

[0008] On the other hand, if, for example, a driven gear and a drive gear are meshed together and they are too far apart, the backlash becomes too large. This excessive backlash causes vibrations that shake the image, resulting in banding (the appearance of light and dark stripes in the smooth gradient of an image).

[0009] This disclosure has been made in view of the above, and its purpose is to provide an image forming apparatus that can easily and quickly adjust the distance between the developing roller and the layer thickness regulating member while suppressing the occurrence of banding and the like. [Means for solving the problem]

[0010] To achieve the above objective, the present disclosure provides an image forming apparatus comprising a developing unit including a developing roller that supplies toner to a photoreceptor drum, a layer thickness regulating member that regulates the thickness of the developer layer formed on the surface of the developing roller, a drive gear that transmits rotational force to a driven gear provided on the shaft of the developing roller, and a developing housing that houses these, wherein the developing unit further includes a first eccentric bearing portion that rotatably supports the shaft of the developing roller and is rotatably mounted in the developing housing such that its center of rotation is eccentric with respect to the shaft of the developing roller, and the first eccentric bearing portion is configured to rotate with respect to the developing housing, thereby moving the developing roller in a direction substantially perpendicular to the direction connecting the center of the drive gear and the center of the driven gear, and adjusting the distance between the surface of the developing roller and the layer thickness regulating member.

[0011] With this configuration, the gap between the surface of the developing roller and the layer thickness regulating member can be adjusted by simply rotating the first eccentric bearing, which is rotatably mounted on the developing housing, so that the center of rotation is eccentric with respect to the shaft of the developing roller. This makes it possible to adjust the DG more easily and quickly compared to when the layer thickness regulating member is fixed to the developing housing by, for example, manually adjusting screw holes.

[0012] Furthermore, for example, when a drive gear and a driven gear are meshed, if they get too close together, the smooth transmission of rotational force is hindered, while if they are too far apart, backlash increases and banding occurs. However, with this configuration, the rotation of the first eccentric bearing section moves the developing roller in a direction approximately perpendicular to the direction connecting the center of the drive gear and the center of the driven gear (hereinafter also referred to as the "gear-to-gear direction"), thus preventing the drive gear and the driven gear from getting too close or too far apart.

[0013] As a result, it is possible to realize an image forming apparatus that ensures smooth rotation of the developing roller, suppresses the occurrence of banding, and allows for easy and quick adjustment of the DG (developing gear ratio).

[0014] Incidentally, if the developing roller is moved in a direction "perpendicular to the gear-to-gear direction," which has the least effect on the approach and separation between the drive gear and the driven gear, it is possible to prevent the drive gear and the driven gear from getting too close or too far apart. However, even if the direction in which the developing roller is moved is not strictly "perpendicular to the gear-to-gear direction," as long as it is within the range of the angle of deviation (pressure angle) that occurs when the teeth of the two gears come into contact, it is possible to transmit a large force from the drive gear to the driven gear while preventing the drive gear and the driven gear from getting too close or too far apart.

[0015] Therefore, in the image forming apparatus, the substantially vertical direction may be a direction within a range of ±20° from the direction perpendicular to the direction connecting the center of the drive gear and the center of the driven gear.

[0016] With this configuration, the direction of movement of the developing roller is within a range of ±20° (pressure angle) from the direction perpendicular to the gear-to-gear direction, which prevents the drive gear and driven gear from getting too close or too far apart, thereby suppressing the occurrence of banding and other issues.

[0017] Furthermore, in the image forming apparatus, the rotational force of the drive gear may be transmitted to the driven gear by meshing the drive gear and the driven gear.

[0018] This configuration makes it possible to realize an image forming apparatus in which the drive gear and driven gear directly mesh, while suppressing the occurrence of banding and other issues, and allowing for easy and quick adjustment of the DG (Dynamic Gear).

[0019] Furthermore, in the image forming apparatus, the rotational force of the drive gear may be transmitted to the driven gear via a belt wrapped around the drive gear and the driven gear.

[0020] This configuration makes it possible to realize an image forming apparatus in which the rotational force of the drive gear is transmitted to the driven gear via a belt, while suppressing the occurrence of banding and other issues, and allowing for easy and quick adjustment of the DG (Deep Gear).

[0021] Furthermore, the image forming apparatus may further include a process unit, which is combined with the developing unit, and which includes the photoreceptor drum and a process frame that supports the photoreceptor drum, and the process unit further includes a second eccentric bearing portion that rotatably supports the shaft portion of the photoreceptor drum and is rotatably mounted on the process frame such that its center of rotation is eccentric with respect to the shaft portion of the photoreceptor drum, and the second eccentric bearing portion may be configured to rotate relative to the process frame, thereby moving the photoreceptor drum and adjusting the distance between the surface of the photoreceptor drum and the surface of the developing roller.

[0022] This configuration allows for the adjustment of the distance between the surface of the photoreceptor drum and the surface of the developing roller by simply rotating a second eccentric bearing, which is rotatably mounted on the process frame, so that its center of rotation is eccentric with respect to the axis of the photoreceptor drum. This makes it possible to realize an image forming apparatus that can easily and quickly adjust not only the DG (developing distance) but also the distance between the photoreceptor drum and the developing roller (hereinafter also referred to as "DSD").

[0023] Incidentally, in a state where the developing unit and the process unit are combined, when a virtual line passing through the tip of the layer thickness regulating member and the center of the developing roller (temporarily referred to as the "first virtual line") and a virtual line passing through the center of the photosensitive drum and the center of the developing roller (temporarily referred to as the "second virtual line") are substantially at right angles, when checking the adjustment value of DG, DG is often measured by laser light irradiated in a direction substantially parallel to the second virtual line from the photosensitive drum side. However, if the moving direction of the photosensitive drum coincides with the direction in which the developing roller moves with respect to the layer thickness regulating member (the direction in which the first virtual line extends), the photosensitive drum becomes an obstacle, the gap between the developing roller and the layer thickness regulating member is hidden, and it may be difficult to measure DG.

[0024] Therefore, in the image forming apparatus, the moving direction of the developing roller due to the rotation of the first eccentric bearing portion and the moving direction of the photosensitive drum due to the rotation of the second eccentric bearing portion may be configured to be substantially perpendicular.

[0025] According to this configuration, since the moving direction of the developing roller due to the rotation of the first eccentric bearing portion and the moving direction of the photosensitive drum due to the rotation of the second eccentric bearing portion are configured to be substantially perpendicular, the moving direction of the photosensitive drum does not coincide with the direction in which the first virtual line extends, so it is possible to suppress the photosensitive drum from obstructing the laser light.

[0026] Furthermore, in the image forming apparatus, the process unit is rotatably provided on the process frame, and when the rotational position reaches a predetermined position, the tip thereof further includes a cleaning blade that contacts the surface of the photosensitive drum to clean residual toner, and the second eccentric bearing portion may have a contact portion that rotates with respect to the process frame and contacts the cleaning blade to position the rotational position of the cleaning blade at the predetermined position.

[0027] According to this configuration, by rotating the second eccentric bearing portion, the DSD can be adjusted, and at the same time, the cleaning blade can be positioned so as to contact the surface of the photosensitive drum.

Advantages of the Invention

[0028] As described above, according to the image forming apparatus according to the present disclosure, it is possible to easily and quickly adjust the distance between the developing roller and the layer thickness regulating member while suppressing the occurrence of banding and the like.

Brief Description of the Drawings

[0029] [Figure 1] It is a perspective view schematically showing a main part of an image forming apparatus according to Embodiment 1 of the present disclosure. [Figure 2] It is a perspective sectional view schematically showing a state where the developing unit and the process unit are integrated. [Figure 3] It is a diagram schematically explaining the relationship between the developing unit and the photosensitive drum. [Figure 4] It is a diagram schematically explaining the structure of the first eccentric bearing portion. [Figure 5] It is a diagram schematically explaining the relationship between the driving gear and the driven gear. [Figure 6] It is a perspective view schematically showing the first eccentric bearing portion. [Figure 7] It is a perspective view schematically showing a state where the first eccentric bearing portion is attached to the developing housing. [Figure 8] It is a perspective view schematically showing a state where the first eccentric bearing portion is attached to the developing housing. [Figure 9] It is a perspective view schematically explaining the moving direction of the developing roller. [Figure 10] It is a perspective view schematically showing the relationship between the operation direction of the operation lever and the moving directions of the developing roller and the photosensitive drum. [Figure 11] It is a perspective view schematically showing the relationship between the moving directions of the developing roller and the photosensitive drum and DG and DSD. [Figure 12]This is a schematic perspective view showing the direction of laser beam irradiation when checking the adjustment values ​​for DG and DSD. [Figure 13] This figure schematically shows a process unit according to Embodiment 2 of the present disclosure. [Figure 14] This diagram schematically shows the cleaning blade in an inverted position. [Figure 15] This is a schematic perspective view showing the second eccentric bearing section. [Figure 16] This diagram schematically shows the state before the photoreceptor drum is installed. [Figure 17] This diagram schematically shows the state after the photoreceptor drum has been installed. [Figure 18] This diagram schematically illustrates the relationship between the drive gear and the driven gear according to another embodiment. [Figure 19] This figure schematically shows the main parts of an image forming apparatus according to another embodiment. [Modes for carrying out the invention]

[0030] The following describes the implementation of this disclosure based on the drawings.

[0031] (Embodiment 1) -Overview of Image Forming Apparatus- Figure 1 is a schematic perspective view showing the main parts of the image forming apparatus 1 according to this embodiment, and Figure 2 is a schematic perspective cross-sectional view showing the developed unit 10 and the process unit 30 integrated together. This image forming apparatus 1 forms an image on a recording medium by an electrophotographic method and is configured as a multifunction peripheral (MFP) having functions such as copying, printing, scanning, and facsimile. As shown in Figures 1 and 2, this image forming apparatus 1 comprises a developed unit 10 and a process unit 30 integrated with the developed unit 10 that transfers a toner image onto the recording medium. The developed unit 10 and the process unit 30 extend in the same direction as the photoreceptor drum 31, such that the direction of the arrow LD in Figure 1 is the longitudinal direction.

[0032] The image forming apparatus 1 according to this embodiment is a monochrome image forming apparatus, and the following description will focus on the case using key plate toner. However, it is not limited to this, and can also be applied to a color image forming apparatus using four toners: cyan, magenta, yellow, and key plate (black) (YMCK).

[0033] - Overview of the developing unit - The developing unit 10 visualizes the electrostatic latent image formed on the surface of the photoreceptor drum 31 contained in the process unit 30 using key plate toner (forming a toner image). As shown in Figures 1 and 2, it includes a developing roller 11 as a magnetic roller that supplies toner to the photoreceptor drum 31, first and second transport screws 13 and 14, a doctor blade 17 that regulates the thickness of the developer layer formed on the surface of the developing roller 11, and a developing housing 18 that houses these components. Note that in Figure 1, only the shaft portions 11a, 13a, 14a, and 31a of the developing roller 11, first and second transport screws 13 and 14, and photoreceptor drum 31 are shown.

[0034] Figure 3 is a schematic diagram illustrating the relationship between the developing unit 10 and the photoreceptor drum 31. The developing housing 18 constitutes the outer casing of the developing unit 10, and a developing tank 19 containing the developer is formed inside it. The developer is, for example, a two-component developer mainly composed of non-magnetic toner and a ferrite-based carrier. The developer contained in the developing tank 19 is conveyed in the direction of the rotation axis while being agitated by the rotation of the first and second transport screws 13 and 14. At that time, the agitation of the developer generates triboelectric charging, causing the ferrite-based carrier to become negatively charged while the toner becomes positively charged.

[0035] A drive gear 15 is provided on the shaft 14a of the second conveying screw 14, while a driven gear 12 (see Figure 5) is provided on the shaft 11a of the developing roller 11, and a belt 16 is wrapped around these drive gear 15 and driven gear 12. The second conveying screw 14 is configured to rotate by a drive source (not shown), and as a result, the rotational force of the drive gear 15 is transmitted to the driven gear 12 via the belt 16, causing the developing roller 11 to rotate in the same direction as the rotation of the second conveying screw 14.

[0036] In this way, as the developing roller 11, which is a magnetic roller, rotates, the developer being agitated and conveyed by the second conveying screw 14 is drawn up, and a developer layer is formed on the surface of the developing roller 11. At the same time, the tip of the doctor blade (layer thickness regulating member) 17, which is provided at a distance from the surface of the developing roller 11, scrapes off excess developer, thereby regulating the thickness of the developer layer formed on the surface of the developing roller 11.

[0037] When the developing unit 10 and the process unit 30 are integrated, the developing roller 11 and the photoreceptor drum 31 face each other with a predetermined distance between them, as shown in Figures 2 and 3. As a result, the positively charged toner is attracted from the developer layer formed on the surface of the developing roller 11 to the surface of the photoreceptor drum 31, which is negatively charged by a charger (not shown), and the toner is supplied to the photoreceptor drum 31 via the developing roller 11.

[0038] - Process Unit Overview - As shown in Figure 2, the process unit 30 includes a photoreceptor drum 31, a charger (not shown), and a cleaner unit 34. The process frame 33, which supports the photoreceptor drum 31, holds the photoreceptor drum 31, the charger, the cleaner unit 34, etc., and these are unitized. As described above, the process unit 30 transfers a toner image onto a recording medium to form an image. The image data used to form the image on the recording medium is image data read by an image reading unit (not shown) provided in the image forming apparatus 1, or image data transmitted from an external computer.

[0039] The charger has comb teeth (sawtooth) (not shown) and is configured to discharge corona from these comb teeth onto the photoreceptor drum 31 to charge the surface of the photoreceptor drum 31 to a predetermined potential. The photoreceptor drum 31 is supported by a process frame 33 and is configured to rotate around an axis by a drive unit (not shown). After being charged by the charger, the photoreceptor drum 31 is exposed by an exposure unit (not shown) configured as a laser scanning unit, so that an electrostatic latent image corresponding to the image data is formed on its surface.

[0040] As described above, toner is supplied to the photoreceptor drum 31 via the developing roller 11, and the electrostatic latent image formed on the surface of the photoreceptor drum 31 is revealed by the toner (a toner image is formed on the surface of the photoreceptor drum 31). In this way, in the process unit 30, the toner image formed on the photoreceptor drum 31 is directly transferred to the recording medium, thereby forming a monochrome image on paper or the like (recording medium).

[0041] The cleaner unit 34 is equipped with a cleaning blade 36 for scraping waste toner from the photoconductor drum 31 and a waste toner transport screw 35 for transporting waste toner. After the toner image is transferred to the intermediate transfer belt, the rubber tip of the cleaning blade 36 is applied to the surface of the photoconductor drum 31 to remove and recover any toner remaining on the surface of the photoconductor drum 31. Reference numeral 39 in Figure 2 indicates a peeling claw provided to prevent paper peeling defects after transfer.

[0042] -DG adjustment- As described above, in the image forming apparatus 1 according to this embodiment, when the toner image is transferred to the recording medium, since a ferrite-based carrier is used as described above, adhesion of the coat carrier to the photoreceptor is less likely to occur, and it is possible to obtain an image with high dot reproduction. However, since the ferrite-based carrier has a low saturation magnetization and a low specific gravity, it is conceivable that the developer may easily scatter when supplying toner to the photoreceptor drum 31 via the developing roller 11. Therefore, in order to properly regulate the thickness of the developer layer, high precision (for example, adjustment of about ±50 μm) is required for the distance between the doctor blade 17 and the developing roller 11 (hereinafter also referred to as "DG").

[0043] Therefore, in the manufacturing process of image forming apparatus, the doctor blade 17 is currently adjusted by manually adjusting the screw holes and fixing the screws. However, adjusting the doctor blade 17 requires skilled techniques, which can lead to significant variations depending on the adjuster and can be very time-consuming. While a mechanism to make the position of the doctor blade 17 variable could be considered, this would reduce the fixing strength, making it difficult to achieve fine adjustments of the doctor blade 17, such as ±50μ.

[0044] Therefore, in the image forming apparatus 1 according to this embodiment, in order to move the developing roller 11 rather than the doctor blade 17, the first eccentric bearing portion 20 that rotatably supports the shaft portion 11a of the developing roller 11 is rotatably mounted on the developing housing 18 such that its center of rotation is eccentric with respect to the shaft portion 11a of the developing roller 11.

[0045] Figure 4 is a schematic diagram illustrating the structure of the first eccentric bearing section 20. Note that in Figure 4, the size of the roller support hole 21a and other elements are exaggerated for clarity. As shown in Figure 4, the first eccentric bearing section 20 has a cylindrical bearing body 21 and an operating lever 23 extending radially outward from the bearing body 21. The first eccentric bearing section 20 is rotatably supported in the developing housing 18 by fitting the cylindrical bearing body 21 into a circular bearing support hole 18a formed through the developing housing 18. Specifically, when the operating lever 23 is rotated counterclockwise in Figure 4, the bearing body 21 rotates counterclockwise within the bearing support hole 18a, while when the operating lever 23 is rotated clockwise in Figure 4, the bearing body 21 rotates clockwise within the bearing support hole 18a.

[0046] The bearing body 21 has a roller support hole 21a formed through it, which rotatably supports the shaft 11a of the developing roller 11 when the shaft 11a of the developing roller 11 is inserted into it. As shown in the center diagram of Figure 4, the roller support hole 21a is formed such that its rotation center CL2 is eccentric by a length L from the rotation center CL1 of the first eccentric bearing part 20 (the center of the bearing support hole 18a). By eccentricating the rotation center of the first eccentric bearing part 20 with respect to the center of the shaft 11a of the developing roller 11 in this way, when the operating lever 23 is turned counterclockwise, the shaft 11a of the developing roller 11 moves to the left, as shown by the white arrow on the left side of Figure 4, while when the operating lever 23 is turned clockwise, the shaft 11a of the developing roller 11 moves to the right, as shown by the white arrow on the right side of Figure 4.

[0047] Figure 5 is a schematic diagram illustrating the relationship between the drive gear 15 and the driven gear 12. Note that in Figure 5, the size and shape of the driven gear 12, drive gear 15, and belt 16 are exaggerated for clarity. As described above, the drive gear 15, located on the shaft portion 14a of the second transport screw 14, and the driven gear 12, located on the shaft portion 11a of the developing roller 11, transmit rotational force from the drive gear 15 to the driven gear 12 via the belt 16 wrapped around both, causing the developing roller 11 to rotate.

[0048] Here, as shown in the enlarged view of Figure 5, a gap BL called backlash is intentionally provided between the teeth 12a of the driven gear 12 and the teeth 16a of the belt 16. Without this backlash BL, the teeth 12a of the driven gear 12 and the teeth 16a of the belt 16 would interfere with each other, making it difficult to rotate the driven gear 12. On the other hand, if the backlash BL is too large, it will cause vibration.

[0049] Thus, in a structure like this embodiment, where the rotational force of the drive gear 15 is transmitted to the driven gear 12 via the belt 16, if the driven gear 12 and the drive gear 15 are too far apart (the belt 16 is pulled too tight), the driven gear 12 will be pressed too hard against the belt 16, causing the backlash BL to become too narrow and hindering the smooth rotation of the developing roller 11. On the other hand, if the driven gear 12 and the drive gear 15 are too close together (the belt 16 is too loose), the driven gear 12 will move away from the belt 16, causing the backlash BL to become too large, resulting in vibrations that shake the image and causing banding.

[0050] Here, the drive gear 15 and the driven gear 12 become too close or too far apart when the driven gear 12 is moved in the direction connecting the centers of the drive gear 15 and the driven gear 12 (hereinafter also referred to as the "gear-to-gear direction"). Therefore, by moving the developing roller 11 in a direction "perpendicular to the gear-to-gear direction," which has the least effect on the approach and separation of the drive gear 15 and the driven gear 12, it is possible to prevent the drive gear 15 and the driven gear 12 from becoming too close or too far apart. However, even if the direction in which the developing roller 11 is moved is not strictly "perpendicular to the gear-to-gear direction," it is possible to suppress the effects of backlash and other factors as long as it is within the range of the angle (pressure angle) that occurs when the teeth 12a of the driven gear 12 and the teeth 16a of the belt 16 come into contact.

[0051] More specifically, conventional gears are shaped such that when teeth come into contact, an angle called the "pressure angle" occurs. More precisely, the "pressure angle" is the angle between the direction of the contact force between two gears and the direction of the velocity of the driven gear (tangential direction). A smaller "pressure angle" allows for more effective force transmission from the driving gear to the driven gear. In this embodiment, as shown in Figure 5, a pressure angle PA is set between the direction F of the contact force between the teeth 12a of the driven gear 12 and the teeth 16a of the belt 16, and the tangential direction T of the driven gear 12. Furthermore, the pressure angle PA is set to 20° in accordance with JIS standards.

[0052] Therefore, in the image forming apparatus 1 according to this embodiment, the first eccentric bearing portion 20 is configured such that the developing roller 11 moves in a direction within ±20° from the direction perpendicular to the gear-to-gear direction as the first eccentric bearing portion 20 rotates relative to the developing housing 18. The movement of the developing roller 11 due to the rotation of the first eccentric bearing portion 20 will be described in detail below.

[0053] Figure 6 is a schematic perspective view showing the first eccentric bearing section 20, Figures 7 and 8 are schematic perspective views showing the first eccentric bearing section 20 mounted on the developing housing 18, and Figure 9 is a schematic perspective view illustrating the direction of movement of the developing roller 11. As shown in Figure 6, an engaging projection 25 is formed at the tip of the operating lever 23 of the first eccentric bearing section 20 so as to protrude inward in the longitudinal direction of the developing unit 10. The first eccentric bearing section 20 is made of, for example, resin and is designed to flex in the direction of the white arrow in Figure 6. As shown in Figures 7 and 8, the developing housing 18 has five positioning holes 18b, 18c, 18d, 18e, and 18f into which the engaging projection 25 can be inserted, arranged at equal intervals on an arc centered on the center (rotation center CL1) of the bearing support hole 18a into which the bearing body 21 of the first eccentric bearing section 20 fits.

[0054] In this configuration, as shown in Figure 7, the engaging projection 25 is inserted into the middle positioning hole 18d of the five positioning holes 18b to 18f. The operating lever 23 is then flexed to remove the engaging projection 25 from the positioning hole 18d, and the bearing body 21 is rotated clockwise in Figure 7 within the bearing support hole 18a so that the engaging projection 25 aligns with the rightmost positioning hole 18f when viewed longitudinally. As a result, as shown by the black arrow in Figure 9, the developing roller 11 moves away from the doctor blade 17 by a predetermined amount corresponding to the rotation angle from the middle positioning hole 18d to the rightmost positioning hole 18f. Then, as shown in Figure 8, the engaging projection 25 is inserted into the rightmost positioning hole 18f, fixing the developing roller 11 in its new position.

[0055] Thus, by adopting a configuration in which the engaging projections 25 are inserted into multiple positioning holes 18b to 18f arranged at equal intervals, it becomes possible to move the developing roller 11 by a predetermined amount corresponding to the interval between the positioning holes 18b to 18f with a simple operation of rotating the operating lever 23 using the positioning holes 18b to 18f as a guide, without having to finely adjust the amount of rotation of the first eccentric bearing section 20.

[0056] Figure 10 is a schematic perspective view showing the relationship between the operating directions of the operating levers 23 and 43 and the movement directions of the developing roller 11 and the photoreceptor drum 31. Figure 11 is a schematic perspective view showing the relationship between the movement directions of the developing roller 11 and the photoreceptor drum 31 and DG and DSD. In Figures 10 and 11, the symbol VL indicates a dashed line passing through the center of the drive gear 15 (axis of the second transport screw 14) and the center of the driven gear 12 (axis of the developing roller 11).

[0057] In the image forming apparatus 1 according to this embodiment, when the operating lever 23 is rotated, as shown by the black arrow in Figure 10, the first eccentric bearing portion 20 rotates relative to the developing housing 18, causing the developing roller 11 to move in a direction within ±20° from the direction perpendicular to the virtual line VL, as shown by the white arrow in Figure 10. As the developing roller 11 moves in this way, the DG changes, as shown in Figure 11, making it possible to fine-tune the DG to, for example, ±30μ.

[0058] As described above, in the developing unit 10 according to this embodiment, the distance between the surface of the developing roller 11 and the doctor blade 17 can be adjusted by a simple configuration in which the first eccentric bearing portion 20, which is rotatably mounted on the developing housing 18, is rotated so that the center of rotation is eccentric with respect to the shaft portion 11a of the developing roller 11. Therefore, compared to the case where the doctor blade 17 is fixed to the developing housing 18 by, for example, manual adjustment of screw holes, the DG can be adjusted easily and in a short amount of time.

[0059] Furthermore, the rotation of the first eccentric bearing section 20 moves the developing roller 11 in a direction approximately perpendicular to the gear-to-gear direction (±20° from the vertical direction), thereby reducing (or suppressing) the change in the distance between the centers of the drive gear 15 and the driven gear 12. This prevents the drive gear 15 and the driven gear 12 from getting too close or too far apart. Consequently, it becomes possible to easily adjust the distance between the developing roller 11 and the doctor blade 17 while suppressing rotational problems of the developing roller 11 (driven gear 12) and the occurrence of banding.

[0060] -DSD adjustment- As described above, ferrite carriers have low saturation magnetization and low specific gravity, so when supplying toner to the photoreceptor drum 31 via the developing roller 11, it is conceivable that the developer may easily scatter. Therefore, high precision is required for the distance between the photoreceptor drum 31 and the developing roller 11 (hereinafter also referred to as "DSD").

[0061] Therefore, in the image forming apparatus 1 according to this embodiment, the second eccentric bearing portion 40 (see Figure 1), which rotatably supports the shaft portion 31a of the photoreceptor drum 31, is rotatably mounted on the process frame 33 such that its center of rotation is eccentric with respect to the shaft portion 31a of the photoreceptor drum 31. This makes it possible to adjust the DSD by moving the photoreceptor drum 31 by rotating the second eccentric bearing portion 40 relative to the process frame 33. Note that the second eccentric bearing portion 40 has the same structure as the first eccentric bearing portion 20 illustrated in Figure 4, so its explanation is omitted to avoid duplication.

[0062] Figure 12 is a schematic perspective view illustrating the direction of laser beam irradiation when checking the adjustment values ​​of DG and DSD. In the image forming apparatus 1 according to this embodiment, as shown in Figure 12, when the developing unit 10 and the process unit 30 are combined, the imaginary line VL1 connecting the tip of the doctor blade 17 and the center of the developing roller 11 and the imaginary line VL2 connecting the center of the photoreceptor drum 31 and the center of the developing roller 11 are at approximately a right angle. In the image forming apparatus 1 with such a layout, when checking the adjustment values ​​of DSD and DG, the DSD is often measured by laser beam irradiated as shown by the white arrow in Figure 12, and the DG is often measured by laser beam irradiated from the photoreceptor drum 31 side in a direction approximately parallel to the imaginary line VL2, as shown by the black arrow in Figure 12.

[0063] However, if the direction of movement of the photoreceptor drum 31 coincides with the direction of movement of the developing roller 11 relative to the doctor blade 17 (the direction in which the imaginary line VL1 extends), the photoreceptor drum 31 may obstruct the gap between the developing roller 11 and the doctor blade 17, as shown by the dashed line in Figure 12, making it difficult to measure DG.

[0064] Therefore, in this embodiment, the second eccentric bearing section 40 is configured such that the direction of movement of the developing roller 11 due to the rotation of the first eccentric bearing section 20 and the direction of movement of the photoreceptor drum 31 due to the rotation of the second eccentric bearing section 40 are substantially perpendicular. As a result, as shown by the dotted arrow in Figure 10, when the operating lever 43 is rotated, the second eccentric bearing section 40 rotates relative to the process frame 33, causing the photoreceptor drum 31 to move substantially parallel to the virtual line VL, as shown by the hatched arrow in Figure 10, and as shown in Figure 11, the DSD changes, making it possible to fine-tune the DSD. In this way, since the direction of movement of the photoreceptor drum 31 is substantially parallel to the virtual line VL and does not coincide with the direction in which the virtual line VL1 extends, it is possible to suppress the photoreceptor drum 31 from interfering with the laser beam.

[0065] As described above, in the process unit 30 according to this embodiment, the DSD can be adjusted by a simple configuration in which the second eccentric bearing portion 40, which is rotatably mounted on the process frame 33, is rotated so that the center of rotation is eccentric with respect to the shaft portion 31a of the photoreceptor drum 31. Therefore, an image forming apparatus 1 can be realized in which not only the DG but also the DSD can be adjusted easily and in a short time, and the adjustment values ​​of DG and DSD can be easily confirmed.

[0066] Furthermore, it is preferable to adjust the DG and DSD in the following order: first, adjust the DG by rotating the first eccentric bearing section 20, and then adjust the DSD by rotating the second eccentric bearing section 40.

[0067] (Embodiment 2) This embodiment differs from Embodiment 1 in that the second eccentric bearing section is provided with a positioning function for the cleaning blade. The following description will focus on the differences from Embodiment 1.

[0068] Figure 13 is a schematic diagram showing the process unit 30A according to this embodiment. Similar to the process unit 30 of Embodiment 1, this process unit 30A includes a photoreceptor drum 31, a charger, and a cleaner unit 34. As shown in Figure 13, the cleaner unit 34 is equipped with a cleaning blade 37, a waste toner transport screw 35, and the like.

[0069] By the way, since the photoreceptor drum 31 is a consumable item, it is necessary to remove the peeling claw 39 and replace it periodically. However, when attaching the photoreceptor drum 31 to the process unit 30 by pressing it as shown by the white arrow in Figure 14, there are cases where the rubber tip 36a of the cleaning blade 36 comes into contact with the photoreceptor drum 31 and flips over.

[0070] Therefore, in this embodiment, the cleaning blade 37 is provided so as to be rotatable around a rotation axis 38 relative to the process frame 33, and the process unit 30A is configured such that when the rotation position of the cleaning blade 37 reaches a predetermined position, the tip portion 37a of the cleaning blade 37 contacts the surface of the photoreceptor drum 31 to clean the remaining toner. In addition, a contact portion 55 is provided on the second eccentric bearing portion 50, and as the second eccentric bearing portion 50 rotates relative to the process frame 33, the contact portion 55 contacts the cleaning blade 37, thereby positioning the rotation position of the cleaning blade 37 at a predetermined position.

[0071] Figure 15 is a schematic perspective view of the second eccentric bearing section 50. As shown in Figure 15, the second eccentric bearing section 50 has a cylindrical bearing body 51 and an operating lever 53 extending radially outward from the bearing body 51. A contact portion 55 is formed at the tip of the operating lever 53 so as to protrude inward in the longitudinal direction of the process unit 30A.

[0072] Figure 16 schematically shows the state before the photoreceptor drum 31 is installed, and Figure 17 schematically shows the state after the photoreceptor drum 31 is installed. The cleaning blade 37 is biased in the counterclockwise direction in Figure 16 by a biasing member (such as a spring) not shown, as indicated by the black-filled arrow in Figure 16. Therefore, even when the photoreceptor drum 31 is pressed and installed in the process unit 30 as indicated by the white-outlined arrow in Figure 16, the tip 37a of the cleaning blade 37 and the photoreceptor drum 31 do not come into contact, thus preventing the tip 37a of the cleaning blade 37 from reversing. When the second eccentric bearing portion 50 is rotated clockwise in Figure 17 relative to the process frame 33, the contact portion 55 comes into contact with the cleaning blade 37, causing the cleaning blade 37 to rotate against the biasing force as indicated by the black-filled arrow in Figure 17 and be positioned in a predetermined position. This allows the tip 37a of the cleaning blade 37 to come into contact with the surface of the photoreceptor drum 31, thereby cleaning away any remaining toner.

[0073] As described above, according to this embodiment, the distance between the surface of the photoreceptor drum 31 and the surface of the developing roller 11 can be adjusted by rotating the second eccentric bearing portion 50, and at the same time, the cleaning blade 37 can be positioned so as to contact the surface of the photoreceptor drum 31. It might seem that if the second eccentric bearing portion 50 is rotated to move the photoreceptor drum 31, the cleaning blade 37 will also rotate, causing the tip portion 37a of the cleaning blade 37 to move away from the surface of the developing roller 11. However, the positioning accuracy of the cleaning blade 37 does not require the same level of precision as the amount of movement of the photoreceptor drum 31 (the amount of rotation of the second eccentric bearing portion 50). Therefore, except in cases where the second eccentric bearing portion 50 is rotated to an extreme degree, the tip portion 37a of the cleaning blade 37 can maintain contact with the surface of the photoreceptor drum 31 even when the second eccentric bearing portion 50 is rotated.

[0074] (Other embodiments) This disclosure is not limited to embodiments and can be implemented in various other ways without departing from its spirit or main features.

[0075] In the above embodiment, the developing roller 11 is moved by the rotation of the first eccentric bearing portion 20, and the photoreceptor drum 31 is moved by the rotation of the second eccentric bearing portion 40. However, the embodiment is not limited to this, and a configuration in which only the developing roller 11 is moved by the rotation of the first eccentric bearing portion 20 may also be adopted.

[0076] Furthermore, in the above embodiment, the present invention was applied to an image forming apparatus 1 of the type in which the rotational force of the drive gear 15 is transmitted to the driven gear 12 via a belt 16. However, the present invention is not limited to this, and may also be applied to an image forming apparatus of the type in which the rotational force of the drive gear 15' is transmitted to the driven gear 12' by meshing the drive gear 15' and the driven gear 12', as shown in Figure 16. In this way, the occurrence of banding and the like can be suppressed in an image forming apparatus of the type in which the drive gear 15' and the driven gear 12' mesh directly.

[0077] Furthermore, in the above embodiment, the present invention was applied to an image forming apparatus 1 in which the drive gear 15 (second transport screw 14) and the driven gear 12 (developing roller 11) are at approximately the same height. However, the present invention is not limited to this, and may also be applied to an image forming apparatus 1' of a type in which the heights of the second transport screw 14' and the developing roller 11' are different, as shown in Figure 19. Even in this case, by moving the developing roller 11' as shown by the hatched arrow in Figure 19 and moving the photoreceptor drum 31' as shown by the black-filled arrow in Figure 19, DG and DSD can be easily adjusted while suppressing the occurrence of banding and the like.

[0078] Furthermore, although a ferrite-based carrier was used in the above embodiment, the invention is not limited to this, and for example, an iron powder-based carrier may also be used.

[0079] Thus, the embodiments described above are merely illustrative in all respects and should not be interpreted restrictively. Furthermore, any variations or modifications that fall within the equivalent scope of the claims are all within the scope of this disclosure. [Industrial applicability]

[0080] According to this disclosure, the distance between the developing roller and the layer thickness regulating member can be easily and quickly adjusted while suppressing the occurrence of banding and other issues, making it extremely useful when applied to an image forming apparatus equipped with a developing unit including a developing roller and a layer thickness regulating member. [Explanation of Symbols]

[0081] 1, 1' Image forming apparatus 10 developing units 11, 11' Developing roller 11a Shaft 12, 12' driven gear 15, 15' drive gear 16 belts 17, 17' Doctor blade (layer thickness regulating member) 18. Developing Housing 20 1st eccentric bearing part 30 process units 31, 31' Photoconductor drum 31a Shaft 33 Process Frames 37 Cleaning Blades 40, 50 2nd eccentric bearing part 55 Contact part CL1 Rotation Center

Claims

1. An image forming apparatus comprising a developing unit including a developing roller that supplies toner to a photoreceptor drum, a layer thickness regulating member that regulates the thickness of the developer layer formed on the surface of the developing roller, a drive gear that transmits rotational force to a driven gear provided on the shaft of the developing roller, and a developing housing that houses these, The developing unit further includes a first eccentric bearing portion that rotatably supports the shaft portion of the developing roller and is rotatably mounted to the developing housing such that its center of rotation is eccentric with respect to the shaft portion of the developing roller. The image forming apparatus is characterized in that the first eccentric bearing portion rotates relative to the developing housing, thereby moving the developing roller in a direction substantially perpendicular to the direction connecting the center of the drive gear and the center of the driven gear, and adjusting the distance between the surface of the developing roller and the layer thickness regulating member.

2. In the image forming apparatus according to claim 1, The image forming apparatus is characterized in that the aforementioned substantially vertical direction is within a range of ±20° from the direction perpendicular to the direction connecting the center of the drive gear and the center of the driven gear.

3. In the image forming apparatus according to claim 1, An image forming apparatus characterized in that the rotational force of the drive gear is transmitted to the driven gear by the meshing of the drive gear and the driven gear.

4. In the image forming apparatus according to claim 1, An image forming apparatus characterized in that the rotational force of the drive gear is transmitted to the driven gear via a belt wrapped around the drive gear and the driven gear.

5. In the image forming apparatus according to claim 1, The process unit further comprises the photoreceptor drum and a process frame supporting the photoreceptor drum, and is combined with the developing unit, The process unit further includes a second eccentric bearing portion that rotatably supports the shaft portion of the photoreceptor drum and is rotatably mounted on the process frame such that its center of rotation is eccentric with respect to the shaft portion of the photoreceptor drum. The image forming apparatus is characterized in that the second eccentric bearing portion is configured to rotate relative to the process frame, thereby moving the photoreceptor drum and adjusting the distance between the surface of the photoreceptor drum and the surface of the developing roller.

6. In the image forming apparatus described in claim 5, An image forming apparatus characterized in that the direction of movement of the developing roller due to the rotation of the first eccentric bearing and the direction of movement of the photoreceptor drum due to the rotation of the second eccentric bearing are configured to be substantially perpendicular.

7. In the image forming apparatus described in claim 5, The process unit further includes a cleaning blade that is rotatably mounted on the process frame and, when rotated to a predetermined position, has its tip contact the surface of the photoreceptor drum to clean up any remaining toner. The image forming apparatus is characterized in that the second eccentric bearing portion has a contact portion that rotates relative to the process frame, contacts the cleaning blade, and positions the rotational position of the cleaning blade at the predetermined position.

Images