JP2013003316A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus in which pressure force produced when a developer supply device is connected to a developing device gives less influence on a difference in the longitudinal direction of a counter gap between a developer carrier and an image carrier, and which thereby generates no density error or density unevenness of an output image.SOLUTION: A developer supply device 20a is connected with pressure to a developer supply port 14 provided at one end side in the longitudinal direction of a developing device 4a. The developing device 4a can fluctuate around a fluctuation shaft 15 and to the direction in which a photosensitive drum 1a and a developing roller 17 are contacted with and separated from each other, and is pressed in the contact direction by a fluctuation pressure spring 16. At least a part of a vertical axis cross section of the fluctuation shaft 15 is positioned in an area A1 which is a projection of the developer supply port 14 within a vertical axis plane of the developing roller 17 in the pressure direction of the developer supply port 14.

Description

  The present invention provides an image forming apparatus in which a developing device is swingably supported in a direction in which a developer carrying member comes in contact with and separates from an image carrying member, and a developer replenishing device is connected to one end portion in the longitudinal direction of the developing device. More particularly, the present invention relates to an arrangement structure of swinging shafts in a plane perpendicular to the axis of a developer carrying member.

  The developing device develops the electrostatic image formed on the image carrier with toner carried on the developer carrier to form a toner image, and transfers the toner image formed on the image carrier to a recording material. 2. Description of the Related Art Image forming apparatuses that form images on recording materials by heating and pressurizing are widely used.

  In Patent Document 1, in order to make the selected developing device face the image carrier, the developing device is rotatably supported with respect to an image carrier support portion that rotatably supports the image carrier.

  In Patent Document 2, both ends in the longitudinal direction of the developing device are supported by a swing shaft so as to be swingable. Then, spacing regulating members arranged at both ends of the developer carrier are brought into contact with the image carrier to ensure a constant state of facing the image carrier along the longitudinal direction of the developer carrier.

  In Patent Document 2, both ends of the charging device in the longitudinal direction are supported by a swing shaft so as to be swingable. The coil spring of the urging member urges the charging device toward the image carrier, thereby ensuring a constant contact state with the image carrier along the longitudinal direction of the charging roller.

Japanese Patent Application Laid-Open No. 07-295386 JP 2002-123063 A

  However, in the developing device, the toner in the developing device is consumed as the image formation is accumulated. Therefore, a developer replenishing device is connected to one end in the longitudinal direction, and the toner just consumed from the outside is used as the replenishing developer. Need to replenish. At this time, it has been found that in the developing device arranged so as to be able to swing with respect to the image carrier, a new problem occurs with respect to connecting the developer supply device to the developing device.

  Referring to FIG. 2, the developer replenishing device (20a) connected to one end in the longitudinal direction of the developing device (4a) has a spacing between the developer carrying member (17) and the image carrying member (1a). Variation in the longitudinal direction is generated. When the swing shaft (15E) is arranged on a straight line (L6) passing through the contact point between the developer carrier (17) and the image carrier (1a), the development is performed when the developer replenishing device (20a) is connected. The applied pressure acting on the device (4a) generates a moment around the swing axis (15E). This moment causes an error in the facing distance between the developer carrier (17) and the image carrier (1a) at both ends in the longitudinal direction of the developing device (4a). For this reason, in the image forming apparatus having a large applied pressure acting on the developing device (4a), the variation in the spacing between the developer carrier (17) and the image carrier (1a) becomes large, and the developed output image Density defects and density unevenness occurred.

  In the present invention, the pressure applied when the developer replenishing device is connected to the developing device is less likely to affect the error in the longitudinal direction of the spacing between the developer carrying member and the image carrying member. An object of the present invention is to provide an image forming apparatus that does not cause the occurrence of the above.

  An image forming apparatus according to the present invention includes: an image carrier supporting portion that rotatably supports the image carrier; and a developing device that rotatably supports the developer carrier that supports the developer and supplies the developer to the image carrier. A swinging shaft that swingably supports the developing device in a direction in which the image carrier and the developer carrier are in contact with and away from the image carrier support, and the image carrier and the developer. An urging member that urges the developing device in a direction to contact the carrier, a developer supply port provided on one end side in the longitudinal direction of the developing device, and a pressure against the developer supply port And a developer replenishing device connected to the developing device for replenishing the developer, wherein at least a part of an axial vertical section of the swing shaft is in the axis vertical plane of the developer carrying member. The developer replenishing port is located in a region projected in the pressurizing direction of the developing device and the developer replenishing port. To have.

  In the image forming apparatus of the present invention, the position of the rocking shaft of the developing device is selected such that the pressure applied to the developing device due to the connection between the developer supply device and the developing device is less likely to generate a moment around the rocking shaft. The swing axis is arranged. For this reason, the oscillating shaft is arranged at a position that does not deviate from the range of the applied pressure acting on the developer supply port.

  Therefore, the pressure applied when the developer replenishing device is connected to the developing device is difficult to tilt or torsionally deform the developing device. For this reason, the connection of the developer replenishing device hardly affects the error in the longitudinal direction of the facing distance between the developer carrying member and the image bearing member, and the density defect or density unevenness of the output image due to the facing distance error does not occur. That's it.

1 is an explanatory diagram of a configuration of an image forming apparatus. It is explanatory drawing of the internal structure of a developing device. It is a perspective view of the appearance of a process cartridge. It is explanatory drawing of the possible arrangement | positioning range of the rocking | fluctuation shaft in Example 1. FIG. FIG. 6 is an explanatory diagram of a state in which a developer supply device is connected to the developing device. It is explanatory drawing of the attachment structure of a process cartridge. It is explanatory drawing of the relationship between the dispersion | variation in a development gap, and image density. It is explanatory drawing of the possible arrangement | positioning range of the rocking | fluctuation shaft in Example 3. FIG. FIG. 10 is an explanatory diagram of a measurement result of a relationship between a development gap and an image density in Example 3.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the present invention, as long as the swing shaft that supports the developing device so as to swing relative to the image carrier is arranged so as to be biased toward the developer replenishing device rather than the conventional common position, Another embodiment in which part or all of the configuration is replaced with the alternative configuration can be implemented.

  Therefore, the image forming apparatus is available in full color / monochrome, color 1 drum type, one component developer / two component developer, direct transfer method / recording material conveyance method / intermediate transfer method, charging method, exposure method, photoreceptor type, etc. It can be done regardless. In the present embodiment, only main parts related to toner image formation / transfer will be described. However, the present invention includes a printer, various printing machines, a copier, a fax machine, a composite machine, in addition to necessary equipment, equipment, and a housing structure. It can be implemented in various applications such as a machine.

<Image forming apparatus>
FIG. 1 is an explanatory diagram of the configuration of the image forming apparatus. As shown in FIG. 1, the image forming apparatus 200 is a tandem intermediate transfer type full color printer in which image forming portions Pa, Pb, Pc, and Pd are arranged along the downward surface of the intermediate transfer belt 7.

  In the image forming portion Pa, a yellow toner image is formed on the photosensitive drum 1 a and transferred to the intermediate transfer belt 7. In the image forming portion Pb, a magenta toner image is formed on the photosensitive drum 1 b and transferred to the intermediate transfer belt 7. In the image forming portions Pc and Pd, a cyan toner image and a black toner image are formed on the photosensitive drums 1c and 1d, respectively, and transferred to the intermediate transfer belt 7.

  The four-color toner images transferred to the intermediate transfer belt 7 are conveyed to the secondary transfer portion T2 and are collectively secondary transferred to the recording material P. The separation roller 61 separates the recording material P drawn from the recording material cassette 60 one by one and sends it to the registration roller 62. The registration roller 62 receives and waits for the recording material P in a stopped state, and sends the recording material P to the secondary transfer portion T2 in time with the toner image on the intermediate transfer belt 7. The toner image carried on the intermediate transfer belt 7 is secondarily transferred to the recording material P that is nipped and conveyed integrally with the secondary transfer portion T2.

  The recording material P on which the four-color toner images are secondarily transferred is heated and pressed by the heating nip of the fixing device 65 to fix the toner images on the surface, and then discharged to the tray 63 through the discharge roller 64. The belt cleaning device 66 rubs the intermediate transfer belt 7 with a cleaning blade to remove the transfer residual toner attached to the surface of the intermediate transfer belt 7 that has passed through the secondary transfer portion T2.

  The image forming portions Pa, Pb, Pc, and Pd are substantially the same except that the color of toner used in the developing devices 4a, 4b, 4c, and 4d is different from yellow, magenta, cyan, and black. Hereinafter, the image forming unit Pa will be described, and the other image forming units Pb, Pc, and Pd will be described by replacing “a” at the end of the reference numerals with “b”, “c”, and “d”.

  The image forming portion Pa surrounds the photosensitive drum 1a and includes a charging roller 2a, an exposure device 3a, a developing device 4a, a transfer roller 5a, and a drum cleaning device 6a. The photosensitive drum 1a has a photosensitive layer formed on the outer peripheral surface of an aluminum cylinder, and rotates at a predetermined process speed.

  The charging roller 2a charges the photosensitive drum 1a to a uniform negative potential. The exposure device 3 scans a scanning beam image data obtained by developing a yellow color separation image with a rotating mirror, and writes an electrostatic image of the image on the surface of the charged photosensitive drum 1a. The developing device 4a supplies toner to the photosensitive drum 1a to develop the electrostatic image into a toner image.

  The transfer roller 5 a presses the intermediate transfer belt 7 to form a primary transfer portion T 1 a between the photosensitive drum 1 a and the intermediate transfer belt 7. By applying a DC voltage to the transfer roller 5a, the toner image carried on the photosensitive drum 1a is primarily transferred to the intermediate transfer belt 7 passing through the primary transfer portion T1a. The drum cleaning device 6a rubs the photosensitive drum 1a with a cleaning blade to remove the transfer residual toner attached to the surface of the photosensitive drum 1a that has passed through the primary transfer portion T1a.

  The intermediate transfer belt 7 is supported around a tension roller 17, a driving roller 8 that also serves as a secondary transfer counter roller, and a stretching roller 18, and is driven by the driving roller 8 to rotate in the direction of arrow R7.

  The secondary transfer portion T <b> 2 is configured by bringing the secondary transfer roller 9 into contact with the intermediate transfer belt 7 whose inner surface is supported by the driving roller 8.

  Toner bottles Ta, Tb, Tc, and Td are disposed above the developing devices 4a, 4b, 4c, and 4d. The replenishment developer taken out from the toner bottles Ta, Tb, Tc, and Td is replenished to the developing devices 4a, 4b, 4c, and 4d by developer replenishing devices 20a, 20b, 20c, and 20d, respectively. The amount of toner consumed in the developing devices 4a, 4b, 4c, and 4d by the image formation is supplied from the toner bottles Ta, Tb, Tc, and Td, respectively, so that the toner in the developing devices 4a, 4b, 4c, and 4d The state of the developer is kept constant.

<Developing device>
FIG. 2 is an explanatory diagram of the internal structure of the developing device. FIG. 3 is a perspective view of the appearance of the process cartridge.

  As shown in FIG. 2, the developing device 4a develops the electrostatic image on the photosensitive drum 1a by charging the developer stored in the developing container 40 and carrying it on the developing roller 17. The developing container 40 is filled with a two-component developer composed of toner (nonmagnetic) and carrier (magnetic).

  The developing container 40 is partitioned into a developing chamber 41 and a stirring chamber 42 by a partition wall 45, and the developing chamber 41 and the stirring chamber 42 communicate with each other through openings (not shown) provided at both ends of the partition wall 45. The circulation path is formed. The developing agent 43 disposed in the developing chamber 41 and the agitating screw 44 disposed in the agitating chamber 42 cause the toner and the carrier to rub against each other while the developer is conveyed and circulated in the developing container 40. Charges up.

  A magnet roller (not shown) is installed in the developing roller 17 in a non-rotating manner, and the magnetic force of the magnet roller magnetically restrains the carrier so that the developer is carried on the surface of the developing roller 17. By applying an oscillating voltage in which an AC voltage is superimposed on a DC voltage to the developing roller 17, only the toner in the developer is transferred to the photosensitive drum 1a.

  As shown in FIG. 3, the photosensitive drum 1a and the developing device 4a are integrally formed as a cartridge including other process means, and can be attached to and detached from the main body housing of the image forming apparatus (200: FIG. 1). Is assembled. The process cartridge 10 is an integral configuration process cartridge that is used in a tandem system in which the photosensitive drum 1a and the developing roller (17: FIG. 2) are paired. In the process cartridge 10, the photosensitive drum 1a and the developing roller 17 may always be in contact with each other, and need not be separated from each other. However, in order to equalize the developing density, the developing gap between the photosensitive drum 1a and the developing roller 17 needs to be equal at each position along the longitudinal direction. Since the general configuration of the developing gap between the conventional photosensitive drum 1a and the developing roller 17 is to fix both the rotating shafts to a common member, the accuracy of the developing gap is low.

  In the image forming apparatus 200, swing shafts 15 are provided at both ends in the longitudinal direction of the developing device 4 a so that the developing device 4 a is swingably supported with respect to the process cartridge 10. Then, contact members against the peripheral surface of the photosensitive drum 1a are arranged at both ends of the rotation shaft of the developing roller 17, and the tip end portion of the contact member is brought into contact with the photosensitive drum 1a. Recently, this method has become common from the viewpoint of accuracy and color misregistration of the photosensitive drum 1a.

  As main components of the process cartridge 10, a developing container 40, a photosensitive drum 1a, a drum casing 12, and a bearing 13 can be listed. The photosensitive drum 1 a is held by the drum casing 12 via a bearing 13. The developing container 40 is held so as to be swingable with respect to the drum housing 12 around the swing shaft 15.

  The developing container 40 is spring biased toward the photosensitive drum 1 a by the swing biasing spring 16. The developing container 40 is biased about the swing shaft 15 by the spring biasing force of the swing biasing spring 16, thereby positioning the developing roller 17 on the photosensitive drum 1a.

  As shown in FIG. 2, the contact members 18 are disposed at both ends of the rotation shaft of the developing roller 17 held in the developing container 40. The abutting member 18 abuts the arcuate tip portion on the photosensitive drum 1a to regulate the facing distance between the developing roller 17 and the photosensitive drum 1a. A developing gap is formed between the developing roller 17 and the photosensitive drum 1a by the tip of the contact member 18 coming into contact with the photosensitive drum 1a. The developing roller 17 faces the photosensitive drum 1a with a predetermined interval (SD gap). Since the development gap between the developing roller 17 and the photosensitive drum 1a is a parameter sensitive to image density, it is desirable that the value of the development gap is constant at any position in the longitudinal direction.

  However, when the developer supply device 20a is connected to one end of the developing device 4a in the longitudinal direction, the developer supply port 14 faces downward in order to crush the sponge seal disposed in the developer supply port 14 and seal the gap. The nip force 14d is applied. At the final stage of pushing the process cartridge 10 from the front side to the back side of the image forming apparatus 200, the tip of the developing device 4a is pushed up and is in close contact with the powder filling unit 14c of the developer supply device 20a. At this time, the nip force 14d from the powder filling portion 14c acts on the developer supply port 14, and the back side of the developing device 4a is pushed down as shown in FIG.

  Since the developer supply port 14 is provided at the end on the back side of the developing container 40, the nip force 14 d causes the moment around the swing shaft 15 to be unevenly distributed between the back side and the near side of the process cartridge 10. Occurs and torsionally deforms the entire process cartridge 10. For this reason, it is difficult to keep the interval between the photosensitive drum 1a and the developing roller 17 constant over the entire area in the longitudinal direction.

  Since the developer replenishing port 14 is disposed at one end in the longitudinal direction of the process cartridge 10, the generated nip force 14 d is not applied to the contact members (18: FIG. 2) at both ends of the developing roller 17. Apply uniform pressure. As a result, the contact pressure of the contact member 18 at the both ends of the photosensitive drum 1a becomes non-uniform, and the difference in compression strain between the contact members 18 at both ends becomes a variation in the development gap, resulting in a difference in development density. The balance between the contact pressures of the pair of contact members 18 arranged at both ends of the developing roller 17 with respect to the photosensitive drum 1a is lost, and there is a difference in the spacing between the developing roller 17 and the opposite ends of the photosensitive drum 1a in the longitudinal direction. Arise.

  Here, if the nip force 14d is set small, the influence of the nip force 14d can be reduced. However, if the nip force 14d between the powder filling unit 14c and the developer supply port 14 is insufficient, toner leakage occurs from the gap between the powder filling unit 14c and the developer supply port 14. In the process cartridge 10 premised on connection to the developer replenishing device 20a, in order to prevent toner leakage, toner scattering and toner leakage do not occur at the joint between the powder filling portion 14c and the developer replenishing port 14. A certain amount of nip force 14d is required. If the nip force 14d of the developer supply port 14 is reduced in order to make the contact pressure of the developing roller 17 to the photosensitive drum 1a uniform, a problem of toner leakage from the developer supply port 14 occurs. Therefore, it is a problem to ensure both the nip force of the developer supply port 14 and the uniform contact pressure of the photosensitive drum 1a.

  In the following embodiments, an arrangement configuration of the swing shaft 15 is proposed in which the nip force generated at the developer supply port 14 does not affect the facing distance between the developing roller 17 and the photosensitive drum 1a. The nip pressure of the developer replenishing port 14 is ensured to reliably prevent toner leakage, and at the same time, the image density density unevenness due to the variation in the facing distance between the developing roller 17 and the photosensitive drum 1a is improved. The present invention provides a process cartridge and an image forming apparatus capable of improving image quality density unevenness without sacrificing the toner scattering and leakage prevention effects of the developer supply port.

<Example 1>
FIG. 4 is an explanatory diagram of a possible arrangement range of the swing shaft in the first embodiment. FIG. 5 is an explanatory diagram of a state in which a developer supply device is connected to the developing device. FIG. 6 is an explanatory diagram of a process cartridge mounting structure. FIG. 7 is an explanatory diagram of the relationship between development gap variation and image density.

  As shown in FIG. 4, a drum housing 12 that is an example of an image carrier support unit rotatably supports a photosensitive drum 1 a that is an example of an image carrier. The contact member 18, which is an example of an interval regulating member, is disposed at both ends of the developing roller 17 and regulates the facing interval between the photosensitive drum 1 a and the developing roller 17.

  The developing device 4a rotatably supports a developing roller 17 that is an example of a developer carrier. The developing roller 17 carries a developer and supplies it to the photosensitive drum 1a. The developer supply port 14 is provided on one end side in the longitudinal direction of the developing device 4a. The developer replenishing device 20a is connected to the developer replenishing port 14 with pressure and replenishes the developing device 4a with the developer.

  The swing shaft 15 supports the developing device 4a so as to be swingable with respect to the drum housing 12 in a direction in which the photosensitive drum 1a and the developing roller 17 are in contact with and away from each other. As shown in FIG. 3, a swinging biasing spring 16 that is an example of a biasing member biases the developing device 4a in a direction in which the photosensitive drum 1a and the developing roller 17 are brought into contact with each other.

  At least a part of the vertical cross section of the swing shaft 15 is located in a region where the developer supply port 14 is projected in the pressurizing direction of the developer supply port 14 in the axis vertical plane of the developing roller 17. The center of the swing shaft 15 is provided in a range A1, which is an example of a region in which the developer supply port 14 is projected in the normal direction of the surface on which the developer supply port 14 is provided. The developer supply port 14 is horizontally disposed on the upper surface of the developing device 4a, and the pressurizing direction with respect to the developer supply port 14 is a vertically downward direction.

  Further, the center of the swing shaft 15 is disposed at a position higher than the straight line L5 connecting the center of the developing roller 17 and the center of the photosensitive drum 1a in the axis vertical plane of the developing roller 17. Further, the center of the swing shaft 15 is provided at a position higher than a straight line connecting the center of the developing roller 17 and the center of the photosensitive drum 1a. The straight line L3 that passes through the center of the developing roller 17 and intersects the straight line L5 at a right angle is biased toward the developer supply port.

  A range A <b> 1 in which the swing shaft 15 is disposed is a range above a horizontal straight line L <b> 4 passing through the center of the developing roller 17. When the swing shaft 15 is arranged on a straight line L5 connecting the center of the photosensitive drum 1a and the center of the developing roller 17, even if the developing device 4a is swung around the swing shaft 15, As seen, the developing roller 17 does not move in the contact / separation direction with respect to the photosensitive drum 1a. In order to cause the developing device 4a to swing around the swinging shaft 15 so that the developing roller 17 contacts the photosensitive drum 1a reliably, the swinging shaft 15 is perpendicular to the straight line L5 and develops the photosensitive drum 1a and the developing roller 17. It is preferable to arrange on a straight line L6 passing through the gap.

  However, in the first embodiment, the swing shaft 15 is biased between the straight line L1 and the straight line L2. A rocking shaft 15 is disposed between a straight line L1 and a straight line L2 projected from the developer supply port 14 of the developing device 4a in the vertical direction. The swing shaft 15 is arranged between the straight line L1 and the straight line L2, and the nip force 14d acts toward the swing shaft 15.

  As shown in FIG. 5, since the nip force 14d acts toward the rocking shaft 15, the nip force 14d when the developer supply device 20a is connected to the developing device 4a has almost no moment around the rocking shaft 15. No longer occurs. As a result, the contact pressure of the contact member (18: FIG. 2) against the photosensitive drum 1a is stabilized even if the nip force 14d of the developer supply device 20a varies considerably due to individual differences in the development device 4a. The development gap is accurately reproduced.

  As shown in FIG. 6, the process cartridge 10 is attached to the frame 29 of the image forming apparatus 200. When positioning the process cartridge 10 to the machine, the bearing 13 of the photosensitive drum 1 a is inserted into the hole 29 a opened in the frame 29 of the image forming apparatus 200. A protrusion 15a is provided from the developing container 40 on the same axis as the swing center axis (15: FIG. 5), and is inserted into the hole 29b of the frame 29 of the image forming apparatus 200 for positioning as a rotation restriction of the process cartridge 10. .

  In the first embodiment, a replenishment process cartridge that employs a method in which the developing roller 17 contacts the photosensitive drum 1a is employed. Therefore, the nip force 14d generated at the joint between the developing device 4a and the developer replenishing device 20a causes non-uniformity in the state of facing the developing roller 17 on the front side and the rear side of the photosensitive drum 1a. Therefore, the securing of the nip force 14d of the developer supply port 14 and the equalization of the drum contact pressure are compatible.

  In the first embodiment, a process cartridge that can achieve the effect of preventing the developer replenishing port 14 from being soiled and improving the unevenness in image quality density by the configuration in which the nip force 14d generated at the developer replenishing port 14 does not affect the drum contact pressure. An image forming apparatus is realized.

  Therefore, the center position of the swing shaft 15 is higher than a straight line L5 connecting the center of the photosensitive drum 1a and the center of the developing roller 17 and lower than the nip boundary line between the powder filling portion 14b and the developer supply port 14. Deploy. The center position of the swing shaft 15 is arranged between a vertical direction line passing through the center of the developing roller 17 and a vertical line farthest from the photosensitive drum 1 a in the cross section of the developer supply port 14.

<Example 2>
FIG. 7 is an explanatory diagram of a possible arrangement range of the swing shaft in the second embodiment. As shown in FIG. 7, in the second embodiment, the oscillating shaft 15 is arranged in a range protruding vertically from the range of the first embodiment shown in FIG. A rocking shaft 15 is disposed between a straight line L1 and a straight line L2 projected from the developer supply port 14 of the developing device 4a in the vertical direction. The swing shaft 15 is arranged between the straight line L1 and the straight line L2, and the nip force 14d acts at the height of the swing shaft 15 indicated by a broken line.

  A range A2 in which the swing shaft 15 is disposed is a range above a straight line L5 connecting the center of the developing roller 17 and the center of the photosensitive drum 1a and overlaps with the developer supply width 14b of the developer supply device 20a. is there. By accommodating the swing shaft 15 within the developer supply width 14b, the moment around the swing shaft 15 due to the nip force 14d can be reduced. Even when the developer replenishing device 20a is connected to the developing device 4a, the nip force 14d when the developer replenishing device 20a is connected to the developing device 4a hardly generates a moment around the swing shaft 15. As a result, the contact pressure of the contact member (18: FIG. 2) against the photosensitive drum 1a is stabilized even if the nip force 14d of the developer supply device 20a varies considerably due to individual differences in the development device 4a.

<Example 3>
FIG. 8 is an explanatory diagram of a possible arrangement range of the swing shaft in the third embodiment. FIG. 9 is an explanatory diagram of the measurement result of the relationship between the development gap and the image density in the third embodiment. As shown in FIG. 8, in Example 3, the center of the swing shaft 15 in the vertical axis plane of the developing roller 17 is closer to the developer carrier than the straight line in the pressurizing direction passing through the center of the developer supply port 14. Has been placed. As compared with the first and second embodiments, the swinging shaft 15 is shifted to the developing roller 17 side, and the developing roller 17 is moved closer to and away from the photosensitive drum 1a. However, in order to suppress the moment of the swing shaft 15 that generates the nip force 14d when the developer supply device 20a is connected to the development device 4a, the developer supply port 14 side is significantly more than the straight line L6 shown in FIG. It is shifted to.

  In the third embodiment, the swing shaft 15 for swinging the developing container 40 is provided at any position in the range A3 surrounded by the straight lines L5, L3, L1, and L7. A straight line L5 is a straight line connecting the center of the photosensitive drum 1a and the center of the developing roller 17. The straight line L3 is a straight line that passes through the center of the developing roller 17 and is perpendicular to the straight line L5. The straight line L1 is a straight line on the side far from the developing roller 17 constituting the developer supply width 14b of the developer supply device 20a. A straight line L7 is a straight line on the nip plane of the developer supply port 14.

  On the other hand, when the swing shaft 15 deviates from the area A3 and is disposed on the side farther from the developing roller 17 than the straight line L1, the developing container 40 is rotated clockwise around the swing shaft 15 by the nip force 14d. A large moment to rotate is generated. As a result, the difference between the contact pressures 18a of the contact members 18 at both ends of the photosensitive drum 1a increases. In order to absorb a large difference, the urging force of the swinging urging spring 16 must be increased more than necessary, which is not preferable from the viewpoint of component cost and assembly. In addition, when arranged on the right side of the straight line L3 passing through the center of the developing roller 17, the difference between the contact pressures 18a of the contact members 18 at both ends of the photosensitive drum 1a increases.

  In the third embodiment, the developer supply device 20 a is connected to the developer supply port 14, and the photosensitive drum 1 a and the development roller 17 on the opposite side of the developer supply device side on the opposite side of the photosensitive drum 1 a and the development roller 17 are opposed to each other. The ratio of the facing distance is 90% or more as shown in FIG.

  As shown in FIG. 9, the image density changes according to the development gap between the photosensitive drum 1 a and the developing roller 17. When an electrostatic image having the maximum gradation of 255/255 is developed, the reflection density of the fixed image is set to 1.20, and the plus or minus 0.1 is within the allowable range. In many cases, this range is not recognized as a density difference.

  However, depending on the developing device 4a, the reflection density may not be within 1.20 plus or minus 0.10. In that case, it occurs due to a difference in compressive strain of the contact member 18 that contacts both ends of the photosensitive drum 1a in the longitudinal direction.

  In Example 1, the arrangement of the swing shaft 15 did not interrupt 300 μm on the developer supply device 20a side with respect to the target value 330 μm of the development gap on the opposite side of the developer supply device 20a. That is, no matter how large the nip pressure 14d of the developer supply device 20a is, the developer supply device 20a is pushed by the developer supply device 20a to increase the contact pressure 18a. The development gap on the developer supply device 20a side is 90% or more of the target value. Was secured.

  As a result, the variation in the reflection density of the fixed image could fall within the allowable range of plus or minus 0.1 with the central value of 1.20. A development gap of a target value of 300 μm or more was ensured, and the variation in reflection density of the fixed image was suppressed to a maximum of 0.2, so that sufficient density reproducibility of the output image could be secured.

1a, 1b, 1c, 1d Photosensitive drum, 4a, 4b, 4c, 4d Developing device 10 Process cartridge, 12 Drum housing, 13 Bearing 14 Developer supply port, 14b Developer supply width, 14c Powder supply unit 14d Nip force , 15 oscillating shaft, 15a protrusion, 16 oscillating biasing spring 17 developing roller, 18 abutting member, 18a abutting pressure, 40 developing container 43 developing screw, 44 conveying screw, 45 partition walls L1, L2, L3, L4, L5, L6, L7 Straight line A1, A2, A3 range

Claims (4)

An image carrier support section for rotatably supporting the image carrier;
A developing device that rotatably supports a developer carrier that carries the developer and supplies the developer to the image carrier;
A rocking shaft for rockingly supporting the developing device in a direction in which the image carrier and the developer carrier are in contact with and separated from the image carrier support portion;
A biasing member that biases the developing device in a direction in which the image carrier and the developer carrier are brought into contact with each other;
A developer supply port provided on one end side in the longitudinal direction of the developing device;
A developer replenishing device connected to the developer replenishing port with pressure to replenish the developer to the developer, and
At least a part of the axial vertical section of the swing shaft is located in a region where the developer supply port is projected in the pressurizing direction of the developing device and the developer supply port in the axis vertical plane of the developer carrier. An image forming apparatus.   The center of the rocking shaft in the axis vertical plane of the developer carrier is disposed on the developer carrier side of the straight line in the pressurizing direction passing through the center of the developer supply port. The image forming apparatus according to claim 1.   The image forming apparatus according to claim 1, wherein the developer supply port is horizontally disposed on an upper surface of the developing device, and the pressing direction is a vertically downward direction. An interval regulating member that is disposed at both ends of the developer carrying body and regulates the facing distance between the image carrying body and the developer carrying body;
In a state where the developer replenishing device is connected to the developer replenishing port, the image bearing member and the developer bearing on the side opposite to the facing distance between the image carrier and the developer bearing member on the developer replenishing device side The image forming apparatus according to any one of claims 1 to 3, wherein the ratio of the opposing distance between the bodies is 90% or more.

Images