WO2014010134A1

WO2014010134A1 - Image formation device

Info

Publication number: WO2014010134A1
Application number: PCT/JP2012/080846
Authority: WO
Inventors: 弘司半田; 啓城森
Original assignee: ブラザー工業株式会社
Priority date: 2012-07-09
Filing date: 2012-11-29
Publication date: 2014-01-16
Also published as: JP2014016503A

Abstract

Provided is an image formation device capable of suppressing the spurting out of developing agent which has passed through a contact section between a layer-thickness-limiting blade and the peripheral surface of a developing roller, and minimizing the occurrence of misprinting, while retaining a simple configuration. A printer (1) equipped with a photosensitive drum (20), a developing roller (34) for facing and contacting the photosensitive drum (20), and a layer-thickness-limiting blade (35) for contacting the peripheral surface of the developing roller (34), wherein the developing roller (34) is positioned in a manner such that the tangential direction (F) of the peripheral surface of the developing roller (34) in the contact section (N) between the layer-thickness-limiting blade (35) and the peripheral surface of the developing roller (34) is substantially identical to the vertical direction.

Description

Image forming apparatus

The present invention relates to an image forming apparatus employing an electrophotographic system.

As described in Patent Document 1, as an electrophotographic image forming apparatus, a photosensitive member on which an electrostatic latent image is formed, a developing roller for carrying toner to be supplied to the photosensitive member, and a developing roller. There is known an image forming apparatus including a blade for regulating the toner layer thickness.

In such an image forming apparatus, the thickness of the toner carried on the developing roller is regulated by the tip of the blade contacting the outer peripheral surface of the developing roller.

JP 2010-170021 A

However, in the image forming apparatus described in Patent Document 1, when the toner carried on the developing roller deteriorates due to repeated image forming operations, the toner passes through the contact portion between the tip of the blade and the outer peripheral surface of the developing roller. The toner may be ejected along the tangential direction of the outer peripheral surface of the developing roller at the contact portion.

In this case, the ejected toner may contaminate a member disposed around the photoreceptor, for example, a charger for charging the photoreceptor. When the charger is contaminated with toner, a charging failure of the photosensitive member may occur, and an image formation failure resulting from the charging failure may occur.

Accordingly, an object of the present invention is to suppress the ejection of the developer that has passed through the contact portion between the layer thickness regulating blade and the peripheral surface of the developing roller, and to suppress the occurrence of image formation defects, while having a simple configuration. An object is to provide an image forming apparatus.

(1) In order to achieve the above-described object, an image forming apparatus according to the present invention is arranged so that an electrostatic latent image is formed, a photoconductor and a surface of the photoconductor facing each other. A developing roller configured to carry a developer to be supplied to the developing roller, and a configuration in which the layer thickness of the developer carried on the circumferential surface of the developing roller is controlled by being in contact with the circumferential surface of the developing roller A layer thickness regulating blade; and a charger that is disposed on the upper side of the developing roller so as to face the surface of the photosensitive member and is configured to charge the surface of the photosensitive member.

Further, the tangential direction of the peripheral surface of the developing roller at the contact portion with the layer thickness regulating blade is substantially the same as the vertical direction.

According to such a configuration, since the tangential direction of the circumferential surface of the developing roller at the contact portion with the layer thickness regulating blade is substantially the same as the vertical direction, the contact between the layer thickness regulating blade and the circumferential surface of the developing roller Gravity acts on the developer passing through the part.

For this reason, even if the developer carried on the developing roller deteriorates, the developer that has passed through the contact portion between the layer thickness regulating blade and the peripheral surface of the developing roller due to gravity does not move to the outer peripheral surface of the developing roller at the contact portion. It is possible to suppress ejection along the tangential direction.

As a result, the developer can be prevented from reaching the charger disposed above the developing roller, and the charger can be prevented from being contaminated by the developer. Therefore, the charging failure of the photoconductor can be suppressed, and consequently, the image formation failure caused by the charging failure of the photoconductor can be suppressed.

Therefore, it is possible to suppress the developer that has passed through the contact portion between the layer thickness regulating blade and the peripheral surface of the developing roller from being ejected, and to suppress the occurrence of defective image formation, although the configuration is simple. (2) In addition, the charger includes a discharge member configured so that a cross-sectional shape in a direction orthogonal to the axial direction of the developing roller is formed in a circular shape, and is discharged when a voltage is applied from the outside. Also good.

In this case, the discharge member is arranged so that all common tangents of the peripheral surface of the discharge member and the peripheral surface of the developing roller overlap with the photosensitive member.

According to such a configuration, since all the common tangent lines of the peripheral surface of the discharge member and the peripheral surface of the developing roller overlap with the photosensitive member, the photosensitive member is interposed between the peripheral surface of the discharging member and the peripheral surface of the developing roller. Is arranged.

Therefore, for example, even when the developer that has passed through the contact portion between the layer thickness regulating blade and the peripheral surface of the developing roller is ejected, the ejected developer hits the photoreceptor and reliably falls due to gravity.

As a result, it is possible to reliably suppress the ejected developer from reaching the charger, and thus it is possible to reliably suppress the charger from being contaminated by the developer.

Further, the developer that has fallen on the photoreceptor reaches the surface of the developing roller and is carried on the developing roller. Therefore, it is possible to suppress the dropped developer from contaminating the periphery of the photoreceptor.

Accordingly, it is possible to reliably prevent the ejected developer from reaching the charger, and to prevent the periphery of the photoreceptor from being contaminated by the developer.
(3) Further, the image forming apparatus may include an exposure device configured to form an electrostatic latent image on the surface of the photoconductor with a laser beam.

Further, the photoconductor may be configured to rotate. In this case, at least one intersection of the common tangent and the photoconductor is arranged on the downstream side in the rotation direction of the photoconductor relative to the incident position of the laser beam on the photoconductor.

According to such a configuration, since at least one intersection of the common tangent and the photoconductor is disposed downstream in the rotation direction of the photoconductor with respect to the incident position of the laser beam on the photoconductor, the layer thickness The developer ejected after passing through the contact portion between the regulating blade and the peripheral surface of the developing roller hits the photoreceptor on which the electrostatic latent image is formed. Then, the developer hitting the photoreceptor is electrostatically held in the electrostatic latent image portion on the surface of the photoreceptor. Therefore, it is possible to reliably suppress the ejected developer from contaminating the periphery of the photoreceptor.

As a result, it is possible to reliably suppress the periphery of the photoconductor from being contaminated by the developer while further reliably suppressing the ejected developer from reaching the charger.
(4) Further, the discharge member may be a discharge wire disposed along the axial direction of the developing roller.

According to such a configuration, since the discharge member is a discharge wire, the discharge wire can be reliably arranged so that all common tangents of the peripheral surface of the discharge wire and the peripheral surface of the developing roller overlap with the photosensitive member.
(5) In addition, the image forming apparatus includes a housing in which an opening is formed, a photoconductor frame configured to be detachably attached to the housing through the opening, and a detachable from the photoconductor frame. A further developing cartridge may be further provided.

In this case, the photosensitive frame includes a photosensitive member and a charger, and the developing cartridge includes a developing roller and a layer thickness regulating blade.

According to such a configuration, since the photosensitive member is provided in the photosensitive member frame and the developing roller is provided in the developing cartridge, for example, when the photosensitive member reaches the end of its life, only the photosensitive member frame can be replaced. When the developing roller reaches the end of its life, only the developing cartridge can be replaced.

Therefore, it is possible to reduce the running cost as compared with the case where both the photosensitive member and the developing roller are provided in one cartridge.

However, when the developing cartridge is configured to be attachable to and detachable from the photoconductor frame in this manner, when the developing cartridge is attached and detached between the charger provided in the photoconductor frame and the developing roller provided in the developing cartridge. In addition, a space for preventing the developing roller and the charger from contacting each other is secured.

Therefore, when the developer that has passed through the contact portion between the layer thickness regulating blade and the peripheral surface of the developing roller is ejected, the developer passes through the space between the developing roller and the charger and reaches the charger. May contaminate the charger.

However, in this image forming apparatus, the developer that has passed through the contact portion between the layer thickness regulating blade and the peripheral surface of the developing roller can be prevented from being ejected, and the developer can be prevented from reaching the charger. While the cost can be reduced, the occurrence of image formation defects can be suppressed.
(6) The image forming apparatus may further include a supply roller that is arranged to face the developing roller along the axial direction of the developing roller and configured to supply the developer to the developing roller.

Further, the photoconductor may be a photoconductor drum arranged along the axial direction.

The developing roller is a first common line that is a common tangent of the peripheral surface of the photosensitive drum and the peripheral surface of the supply roller located on one side with respect to a virtual straight line passing through the axial center of the photosensitive drum and the axial center of the supply roller. You may arrange | position between a tangent and the 2nd common tangent which is a common tangent of the surrounding surface of the photosensitive drum located in the other side, and the surrounding surface of a supply roller.

According to such a configuration, since the image forming apparatus includes the supply roller, the developer can be reliably supplied to the developing roller.

In addition, since the developing roller is disposed between the first common tangent and the second common tangent, an efficient arrangement of the photosensitive drum, the developing roller, and the supply roller can be ensured. Therefore, it is possible to reduce the size of the image forming apparatus.
(7) Further, the developing roller may be arranged so that its axial center is located on the virtual straight line.

According to such a configuration, since the shaft center of the photosensitive drum, the shaft center of the supply roller, and the shaft center of the developing roller are arranged on the same virtual straight line, A more efficient arrangement of the rollers and the supply rollers can be ensured.

Therefore, the image forming apparatus can be further downsized.

According to the present invention, the developer that has passed through the contact portion between the layer thickness regulating blade and the peripheral surface of the developing roller can be suppressed from being ejected while having a simple configuration, and the occurrence of defective image formation can be suppressed.

1 is a side sectional view showing a printer of an embodiment of an image forming apparatus of the present invention. FIG. 2 is a central sectional view of the process cartridge shown in FIG. 1. FIG. 3 is an enlarged view of main parts of a developing roller and a layer thickness regulating blade shown in FIG. 2. FIG. 3 is a perspective view of the developing cartridge and the drum cartridge shown in FIG. 2 as viewed from the upper left side.

1. Printer A printer 1 as an example of an image forming apparatus includes a main body casing 2 as an example of a casing, as shown in FIG.

The main casing 2 is formed in a substantially box shape, and includes a paper feeding unit 3 for feeding the paper S and an image forming unit 4 for forming an image on the fed paper S. ing.

In the following description, when referring to the direction, the right side of the paper surface in FIG. 1 is the front side and the left side of the paper surface in FIG. 1 is the rear side, based on the state where the printer 1 is placed horizontally. Further, when the printer 1 is viewed from the front side, the left and right sides of FIG. 1 are the left side, and the back side of the page is the right side. That is, the front-rear direction and the left-right direction are horizontal directions, and the up-down direction is a vertical direction.
(1) Main Body Casing The main body casing 2 is formed with a cartridge opening 5 as an example of an opening for attaching and detaching a process cartridge 15 (described later) and a paper opening 6 for introducing the paper S. Yes.

The cartridge opening 5 is formed through the upper end of the main casing 2 in the vertical direction.

The paper opening 6 is formed to penetrate in the front-rear direction at the lower end of the front end of the main casing 2.

Further, the main body casing 2 is provided with a top cover 7 at its upper end and a paper feed cover 8 at its front end. The top cover 7 is provided with a paper discharge tray 41 from which the paper S is discharged.

The top cover 7 is swingably (moved) between a closed position for closing the cartridge opening 5 and an open position for opening the cartridge opening 5 with the rear end as a fulcrum (shown in FIG. 1). (See the two-dot chain line).

The paper feed cover 8 is provided so as to be swingable (movable) between a first position where the paper opening 6 is closed and a second position where the paper opening 6 is opened with the lower end portion as a fulcrum (see FIG. 1).
(2) Paper Feed Unit The paper feed unit 3 includes a paper placement unit 9 provided at the bottom of the main casing 2.

The paper stacking portion 9 is communicated with the outside of the main casing 2 through the paper opening 6.

The sheet S is stacked on the upper surface of the sheet feed cover 8 while the sheet feed cover 8 is disposed at the second position, and the rear part is loaded on the sheet via the sheet opening 6. Stacked in the placement unit 9.

The paper feeding unit 3 includes a pickup roller 11 disposed on the upper side of the rear end portion of the paper placing unit 9, a paper feeding roller 12 disposed on the rear side of the pickup roller 11, and a rear lower side of the paper feeding roller 12. The sheet feeding pad 13 is disposed opposite to the sheet feeding side, and the sheet feeding path 14 extends continuously upward from the rear end portion of the sheet feeding pad 13.
(3) Image Forming Unit The image forming unit 4 includes a process cartridge 15, a scanner unit 16 as an example of an exposure device, and a fixing unit 17.
(3-1) Process Cartridge The process cartridge 15 is configured to be detachable from the main casing 2 through the cartridge opening 5, and is mounted on the main casing 2 above the rear portion of the paper feeding section 3. Yes.

As shown in FIG. 4, the process cartridge 15 includes a drum cartridge 18 and a developing cartridge 19.
(3-1-1) Drum Cartridge The drum cartridge 18 includes a drum frame 50 as an example of a photoconductor frame.

The drum frame 50 is configured to be attachable to and detachable from the main casing 2 through the cartridge opening 5, a rear portion thereof is formed as a drum housing portion 51, and a front portion thereof is formed as a cartridge mounting portion 52.

The drum accommodating portion 51 is formed in a substantially box shape extending in the left-right direction and opened on the front side, and the front end portion is partitioned as a drum opening 53.

Further, as shown in FIG. 2, the drum accommodating portion 51 includes a photosensitive drum 20 as an example of a photosensitive member, a transfer roller 21, and a scorotron charger 22 as an example of a charger.

The photosensitive drum 20 includes a drum body 57 and a drum shaft 58.

The drum body 57 includes a metal base tube formed in a substantially cylindrical shape extending in the left-right direction and a resin photosensitive layer covering the surface of the base tube (see FIG. 4).

The drum shaft 58 is made of metal and has a substantially cylindrical shape extending in the left-right direction, and the length in the left-right direction is longer than the length in the left-right direction of the drum body 57. The drum shaft 58 is inserted into the drum main body 57 so as to be relatively rotatable so that the central axis thereof coincides with the central axis of the drum main body 57.

As shown in FIG. 2, the photosensitive drum 20 is provided at a substantially central portion in the drum accommodating portion 51 so that the front peripheral surface of the drum body 57 is exposed through the drum opening 53.

Further, the photosensitive drum 20 is provided so that the left and right ends of the drum shaft 58 are supported by the left and right side walls of the drum accommodating portion 51 (see FIG. 4), so that the photosensitive drum 20 can rotate about the shaft center A1 of the drum body 57. It has been.

The photosensitive drum 20 receives a driving force from a driving source (not shown) such as a motor provided in the main body casing 2 during an image forming operation (described later), and rotates in the rotation direction X (left side view) indicated by an arrow. It is driven to rotate clockwise.

The transfer roller 21 is formed in a substantially cylindrical shape extending in the left-right direction, and is pressed against the drum body 57 of the photosensitive drum 20 from the rear side.

Specifically, the transfer roller 21 is disposed on the rear side of the photosensitive drum 20 so that the axis center thereof is positioned slightly below the axis center A1 of the drum main body 57. The lower end edge of the transfer roller 21 is disposed above the lower end edge of the drum main body 57. Specifically, an imaginary line segment (not shown) connecting the axis center of the transfer roller 21 and the axis center A1 of the photosensitive drum 20, and an imaginary straight line (not shown) extending horizontally along the front-rear direction. The acute angle formed by is about 3 °. Therefore, the pressure (transfer pressure) at which the transfer roller 21 is pressed against the photosensitive drum 20 is not affected by the weight of the transfer roller 21.

The scorotron charger 22 includes a discharge wire 23 as an example of a discharge member and a grid 24.

The discharge wire 23 is formed in a circular shape in cross section, is stretched so as to extend in the left-right direction, and is opposed to the front upper side of the photosensitive drum 20 with a space therebetween.

The grid 24 is formed in a substantially U-shape in a side view opened toward the front upper side, and is provided so as to surround the discharge wire 23 from the lower rear side.

The scorotron charger 22 is disposed on the upper end portion of the drum housing portion 51 so that the lower end portion of the grid 24 is opposed to the peripheral surface of the drum main body 57 with an interval on the front upper side of the photosensitive drum 20. It is supported.

Specifically, the scorotron charger 22 is disposed with a distance in the circumferential direction of the drum body 57 with respect to the transfer roller 21, and connects the shaft center A 1 of the photosensitive drum 20 and the shaft center of the transfer roller 21. The angle formed by a virtual line segment (not shown) and a virtual line segment (not shown) connecting the axial center A1 of the photosensitive drum 20 and the discharge wire 23 is arranged to be about 120 °. Has been.

As shown in FIG. 4, the cartridge mounting portion 52 is formed in a substantially box shape whose upper side and rear side are open so as to allow the mounting and dismounting of the developing cartridge 19, and the drum accommodating portion 51 via the drum opening 53. And communicated in the front-rear direction.
(3-1-2) Developing Cartridge As shown in FIG. 2, the developing cartridge 19 is detachably mounted on the cartridge mounting portion 52 of the drum cartridge 18 (see FIG. 4), and is disposed on the front lower side of the photosensitive drum 20. Has been.

The developing cartridge 19 includes a developing frame 25 as shown in FIG.

The developing frame 25 is formed in a substantially box shape extending in the left-right direction, and inside thereof, as shown in FIG. 2, a toner storage chamber 26 and a developing chamber 27 are formed side by side. The toner storage chamber 26 and the developing chamber 27 are formed to have substantially the same volume, and communicate with each other through a communication port 28.

The toner storage chamber 26 stores toner (an example of a developer), and an agitator 29 is provided at a substantially central portion in the front-rear and vertical directions. That is, the agitator 29 is disposed below the photosensitive drum 20.

In the developing chamber 27, a supply roller groove 30, a developing roller facing surface 31, and a lower film attaching surface 32 are formed on the upper surface of the lower wall.

The supply roller groove 30 has a substantially semicircular shape along the peripheral surface of a supply roller 33 (described later), and is formed so as to be recessed downward in the rearward direction.

The developing roller facing surface 31 has a substantially arc shape along the peripheral surface of the developing roller 34 (described later), and is formed so as to extend continuously rearward from the rear end portion of the supply roller groove 30.

The lower film attaching surface 32 is formed continuously from the rear end portion of the developing roller facing surface 31 so as to incline slightly upward toward the rear. That is, the lower film attaching surface 32 is disposed above the developing roller facing surface 31.

Further, the lower film attaching surface 32 is disposed to face the lower portion of the drum main body 57 with an interval in the vertical direction, and overlaps the axial center A1 of the drum main body 57 when projected in the vertical direction. Are arranged as follows.

The developing chamber 27 is provided with a supply roller 33, a developing roller 34, a layer thickness regulating blade 35, and a lower film 36.

The supply roller 33 includes a metal supply roller shaft 63 that extends in the left-right direction and a sponge roller 64 that covers the supply roller shaft 63 so that both left and right ends of the supply roller shaft 63 are exposed.

The supply roller 33 is disposed on the rear side of the toner storage chamber 26 so that the lower portion thereof is disposed in the supply roller groove 30, and is substantially the same height as the toner storage chamber 26 in the vertical direction. Is located.

Further, the supply roller 33 is rotatably provided around the axis center A2 of the front side of the developing chamber 27 by supporting the left and right ends of the supply roller shaft 63 by the developing frame 25.

The driving force from a driving source (not shown) such as a motor provided in the main body casing 2 is transmitted to the supply roller 33 during image formation (described later). Then, the supply roller 33 rotates in the rotation direction Y (counterclockwise as viewed from the left side) indicated by an arrow in FIG. 2 so as to rotate in a direction opposite to the development roller 34 in a portion (described later) that faces the development roller 34. Driven by rotation. A supply bias is applied to the supply roller shaft 63 of the supply roller 33 from a power source (not shown) provided in the main body casing 2 during image formation (described later).

The developing roller 34 includes a metal developing roller shaft 65 extending in the left-right direction and a rubber roller 66 that covers the developing roller shaft 65 so that both left and right ends of the developing roller shaft 65 are exposed.

The developing roller 34 is disposed such that the peripheral surface of the lower portion of the rubber roller 66 and the developing roller facing surface 31 are opposed to each other with a space therebetween.

Further, the developing roller 34 is rotatably provided around the shaft center A3 at the rear portion of the developing chamber 27 by supporting the left and right ends of the developing roller shaft 65 with the developing frame 25. .

Further, in the developing roller 34, the rubber roller 66 is opposed to the sponge roller 64 of the supply roller 33 from the rear upper side along the left-right direction. Further, the developing roller 34 is provided so that the upper and rear portions of the rubber roller 66 are exposed from the developing chamber 27, and the rubber roller 66 faces the drum body 57 of the photosensitive drum 20 from the front lower side along the left-right direction. In contact.

That is, the developing roller 34 is disposed on the rear upper side of the supply roller 33 and on the lower front side of the photosensitive drum 20 so as to be sandwiched between the supply roller 33 and the photosensitive drum 20. Is located below the axial center A1 of the photosensitive drum 20.

Further, as shown in FIG. 3, the developing roller 34 is arranged so that a common tangent line A between the front peripheral surface of the discharge wire 23 and the front peripheral surface of the rubber roller 66 overlaps the drum body 57. Specifically, the common tangent line A and the peripheral surface of the drum body 57 have two intersection points, and the lower intersection point P1 is located above the developing roller 34 with a space therebetween.

That is, all the common tangents of the peripheral surface of the discharge wire 23 and the peripheral surface of the rubber roller 66 overlap with the drum body 57.

Further, as shown in FIG. 2, the developing roller 34 has a peripheral surface of the drum main body 57 positioned on the front side with respect to a virtual straight line L1 passing through the axial center A1 of the photosensitive drum 20 and the axial center A2 of the supply roller 33, and Common tangent B (an example of the first common tangent) on the peripheral surface of the sponge roller 64 and a common tangent C (an example of the second common tangent) on the peripheral surface of the drum body 57 and the peripheral surface of the sponge roller 64 located on the rear side. It is arranged between. The axial center A3 of the developing roller 34 is located on the virtual straight line L1.

Further, the developing roller 34 is disposed at a distance from the scorotron charger 22 in the circumferential direction of the drum body 57. Specifically, in the developing roller 34, an angle formed by a virtual line segment (not shown) connecting the axial center A1 of the photosensitive drum 20 and the discharge wire 23 and the virtual straight line L1 is about 120 °. Are arranged as follows. That is, the developing roller 34, the scorotron charger 22, and the transfer roller 21 are arranged at substantially equal intervals in the circumferential direction of the drum body 57.

Further, a driving force from a driving source (not shown) such as a motor provided in the main body casing 2 is transmitted to the developing roller 34 during an image forming operation (described later). Then, the developing roller 34 is rotationally driven in a rotation direction Z (counterclockwise as viewed from the left side) indicated by an arrow shown in FIG. The peripheral speed (rotational speed) of the developing roller 34 is faster than the peripheral speed (rotational speed) of the supply roller 33.

Further, a developing bias is applied to the developing roller shaft 65 of the developing roller 34 from a power source (not shown) provided in the main casing 2 during image formation (described later).

As shown in FIG. 3, the layer thickness regulating blade 35 is formed in a substantially flat plate shape extending in the vertical and horizontal directions from a thin metal plate having elasticity.

The layer thickness regulating blade 35 includes a base end portion 70 supported by the developing frame 25, a tip end portion 71 disposed on the developing roller 34 side, and a straight portion defined between the base end portion 70 and the tip end portion 71. 72.

In the following description, the tip surface of the tip portion 71 is a tip T, and the boundary between the straight portion 72 and the tip portion 71 is an inflection point I.

The base end portion 70 is formed so as to incline backward as it goes downward, and is fixed to the rear end portion of the upper wall of the developing chamber 27.

The straight line portion 72 is continuous with the lower end portion of the base end portion 70, is partitioned between the lower end portion of the base end portion 70 and the upper end portion of the tip end portion 71, and is a substantially flat plate extending along the direction in which the base end portion 70 extends. It is formed into a shape. Specifically, the linear portion 72 is formed to incline backward as it goes downward.

The front end portion 71 is continuous from the lower end portion of the linear portion 72 and is partitioned into a lower end portion including the front end T of the layer thickness regulating blade 35. Moreover, the front end portion 71 is formed so as to be bent in a substantially circular arc shape in a side view from the lower end portion (inflection point I) of the linear portion 72 toward the front end T.

Further, the front end portion 71 includes a contact portion 73 that comes into contact with the peripheral surface of the rubber roller 66 and a separation portion 74 that is separated from the peripheral surface of the rubber roller 66 toward the front end T from the contact portion 73.

The contact portion 73 is continuous from the lower end portion of the linear portion 72 and is disposed at a fixed position in the vertical direction with respect to the rubber roller 66. Further, the contact portion 73 is pressed (contacted) from the front side by the elastic force of the layer thickness regulating blade 35 over the entire lateral direction of the peripheral surface of the rubber roller 66. A contact portion N between the contact portion 73 and the peripheral surface of the rubber roller 66 is disposed below a horizontal line D passing through the axial center A3 of the developing roller 34.

Further, the tangent line E of the rubber roller 66 at the contact portion N extends in substantially the same direction as the vertical direction. That is, the tangential direction F of the rubber roller 66 at the contact portion N is substantially the same as the vertical direction.

More specifically, the acute angle θ formed by the tangent line E and the vertical line G passing through the contact portion N is, for example, 0 to 5 °, specifically about 3 °.

The separation part 74 is formed in a substantially curved shape in a side view so as to be separated from the peripheral surface of the rubber roller 66 as it continues from the contact part 73 and moves from the contact part 73 toward the tip T.

As shown in FIG. 2, the lower film 36 has a rear portion fixed to the lower film attaching surface 32, and a front end thereof is in contact with the peripheral surface of the rubber roller 66 above the developing roller facing surface 31. .
(3-2) Scanner Unit As shown in FIG. 1, the scanner unit 16 is disposed on the front side of the process cartridge 15 so as to face the photosensitive drum 20 with a space in the front-rear direction.

The scanner unit 16 emits a laser beam L toward the photosensitive drum 20 based on the image data, and exposes the peripheral surface of the drum body 57 of the photosensitive drum 20.

Specifically, the laser beam L is emitted backward from the scanner unit 16 and exposes the peripheral surface at the front end portion of the drum body 57. That is, an exposure point P2 (a peripheral surface at the front end portion of the photosensitive drum 20) as an example of an incident position where the drum main body 57 is exposed is at an axial center A1 of the drum main body 57 of the photosensitive drum 20, as shown in FIG. On the other hand, it is set on the opposite side of the nip point where the photosensitive drum 20 and the transfer roller 21 come into contact with each other.

Further, the exposure point P2 is arranged on the upstream side in the rotation direction X with respect to the intersection point P1 between the common tangent line A and the peripheral surface of the drum body 57.

At this time, as shown in FIG. 1, the developing cartridge 19 is arranged below the emission locus of the laser beam L, and the scorotron charger 22 is arranged above the emission locus of the laser beam L. .

As shown in FIG. 1, a guide portion 37 that guides attachment / detachment of the process cartridge 15 is provided on the inner surface of the main body casing 2 between the scanner unit 16 and the photosensitive drum 20. When the process cartridge 15 is detached from the main casing 2, the process cartridge 15 is guided by the guide portion 37, so that the developing cartridge 19 attached to the drum cartridge 18 has a lower emission locus of the laser beam L. Pass from the top to the top.

At this time, the various rollers (transfer roller 21, supply roller 33 and developing roller 34) provided in the process cartridge 15 also pass the emission locus of the laser beam L from the lower side to the upper side.
(3-3) Fixing Unit The fixing unit 17 is disposed above the rear portion of the drum cartridge 18. Specifically, the fixing unit 17 includes a heating roller 38 disposed above the scorotron charger 22 and a pressure roller 39 pressed against the heating roller 38 from the rear upper side.

That is, the heating roller 38 is disposed in the vicinity of the upper end portion (open end portion) of the grid 24 of the scorotron charger 22.
2. Image Forming Operation The toner in the toner storage chamber 26 of the developing cartridge 19 is supplied to the sponge roller 64 of the supply roller 33 through the communication port 28 by the rotation of the agitator 29 and further supplied to the rubber roller 66 of the developing roller 34. Then, it is frictionally charged positively between the sponge roller 64 and the rubber roller 66.

As shown in FIG. 3, the positively charged toner reaches the contact portion 73 of the layer thickness regulating blade 35 as the developing roller 34 rotates in the rotation direction Z.

Then, when the toner passes between the rear surface of the contact portion 73 and the peripheral surface of the rubber roller 66 (contact portion N), the toner is carried on the peripheral surface of the rubber roller 66 as a thin layer.

On the other hand, as shown in FIG. 1, a voltage is applied to the discharge wire 23 of the scorotron charger 22 from a power source (not shown, an example of the outside) provided in the main body casing 2. Then, the discharge wire 23 is discharged, and the peripheral surface of the drum body 57 of the photosensitive drum 20 is uniformly charged. Then, the charged peripheral surface of the drum body 57 is exposed by the laser beam L of the scanner unit 16.

Thereby, an electrostatic latent image based on the image data is formed on the peripheral surface of the drum body 57.

Then, when the photosensitive drum 20 is rotated, the electrostatic latent image on the peripheral surface of the drum body 57 and the rubber roller 66 of the developing roller 34 face each other.

Then, the toner carried on the rubber roller 66 is supplied to the electrostatic latent image on the peripheral surface of the photosensitive drum 20.

Thereby, a toner image (visible image) is formed on the peripheral surface of the drum body 57 of the photosensitive drum 20.

The sheets S stacked on the sheet loading unit 9 are sent between the sheet feeding roller 12 and the sheet feeding pad 13 by the rotation of the pickup roller 11 and are turned one by one by the rotation of the sheet feeding roller 12.

Thereafter, the sheet S is conveyed to the sheet feeding path 14 by the rotation of the sheet feeding roller 12 and fed one by one between the photosensitive drum 20 and the transfer roller 21 at a predetermined timing ( Paper feeding operation).

The sheet S passes between the photosensitive drum 20 and the transfer roller 21 from the lower side to the upper side. At this time, the toner image is transferred to the paper S, and an image is formed (transfer operation).

The sheet S on which the toner image is transferred is conveyed between the heating roller 38 and the pressure roller 39.

And, when passing between the heating roller 38 and the pressure roller 39, it is heated and pressurized. As a result, the image is thermally fixed on the sheet S (fixing operation).

Thereafter, the paper S is conveyed toward the paper discharge roller 40 and is discharged onto the paper discharge tray 41 of the main casing 2 by the paper discharge roller 40 (paper discharge operation).

In this way, the sheet S is fed from the sheet placing portion 9, passes between the photosensitive drum 20 and the transfer roller 21 (nip point), and then passes between the heating roller 38 and the pressure roller 39. After that, the paper is transported through a substantially C-shaped transport path in side view so that the paper is discharged onto the paper discharge tray 41.
3. Operation and Effect (1) In the printer 1, as shown in FIG. 3, the tangent E of the peripheral surface of the rubber roller 66 at the contact portion N between the contact portion 73 of the layer thickness regulating blade 35 and the peripheral surface of the rubber roller 66 of the developing roller 34. However, it extends in substantially the same direction as the vertical direction (vertical direction). That is, the tangential direction F of the rubber roller 66 at the contact portion N is substantially the same as the vertical direction. Specifically, the acute angle θ formed by the tangent line E and the vertical line G passing through the contact portion N is, for example, 0 to 5 °, specifically about 3 °.

Therefore, gravity acts on the toner passing through the contact portion N.

As a result, even if the toner carried on the rubber roller 66 of the developing roller 34 deteriorates, the toner that has passed through the contact portion N due to the gravity is along the tangential direction F of the peripheral surface of the rubber roller 66 at the contact portion N. Spouting can be suppressed.

Therefore, the toner can be prevented from reaching the discharge wire 23 of the scorotron charger 22 disposed above the developing roller 34, and the discharge wire 23 can be prevented from being contaminated by the toner. Therefore, the charging failure of the photosensitive drum 20 can be suppressed, and consequently the image formation failure caused by the charging failure of the photosensitive drum 20 can be suppressed.

Accordingly, it is possible to suppress the ejection of the toner that has passed through the contact portion N between the contact portion 73 of the layer thickness regulating blade 35 and the peripheral surface of the rubber roller 66 of the developing roller 34 with a simple configuration, and image formation. The occurrence of defects can be suppressed.
(2) Further, as shown in FIG. 3, the scorotron charger 22 includes a discharge wire 23 having a circular cross-sectional shape in the front-rear and up-down direction (direction perpendicular to the axial direction of the developing roller 34). Yes.

As shown in FIG. 2, the discharge wire 23 has a common tangent line (for example, common tangent line A) between its peripheral surface and the peripheral surface of the rubber roller 66 of the developing roller 34, and the drum body 57 of the photosensitive drum 20. They are arranged so as to overlap. That is, the drum body 57 is disposed between the peripheral surface of the discharge wire 23 and the peripheral surface of the rubber roller 66.

Therefore, for example, even when the toner that has passed through the contact portion N is ejected, the ejected toner hits the peripheral surface of the drum body 57 and reliably falls by gravity.

As a result, the scattered toner can be reliably prevented from reaching the discharge wire 23, so that the discharge wire 23 can be reliably prevented from being contaminated by the toner.

Further, the toner that falls on the peripheral surface of the drum body 57 reaches the peripheral surface of the rubber roller 66 and is carried on the rubber roller 66. Therefore, it is possible to suppress the dropped toner from contaminating the periphery of the photosensitive drum 20.

Therefore, it is possible to reliably prevent the scattered toner from reaching the discharge wire 23 and to prevent the periphery of the photosensitive drum 20 from being contaminated by the dropped toner.

In particular, as shown in FIG. 3, of the intersections between the common tangent line A and the peripheral surface of the drum main body 57, the intersection P <b> 1 located on the lower side (developing roller 34 side) is located above the developing roller 34. Therefore, the toner that has fallen on the peripheral surface of the drum body 57 surely reaches the peripheral surface of the rubber roller 66.
(3) The printer 1 also includes a scanner unit 16 configured to form an electrostatic latent image on the peripheral surface of the drum body 57 of the photosensitive drum 20 by the laser beam L as shown in FIG. Yes.

Further, the photosensitive drum 20 is configured to rotate in the rotation direction X as shown in FIG. Of the intersection points between the common tangent line A and the peripheral surface of the drum body 57, the lower intersection point P1 is on the downstream side in the rotation direction X with respect to the exposure point P2 of the laser beam L on the peripheral surface of the drum body 57. Has been placed.

Therefore, even if the toner that has passed through the contact portion N is ejected, the ejected toner hits the peripheral surface of the drum body 57 of the photosensitive drum 20 on which the electrostatic latent image is formed. Then, the toner hitting the peripheral surface of the drum main body 57 is electrostatically held in the electrostatic latent image portion on the peripheral surface of the drum main body 57. As a result, the ejected toner can be reliably prevented from contaminating the periphery of the photosensitive drum 20.

Accordingly, it is possible to more reliably suppress the periphery of the photosensitive drum 20 from being contaminated by the toner while further reliably suppressing the ejected toner from reaching the discharge wire 23.
(4) In addition, as shown in FIGS. 1 and 4, the printer 1 includes a main body casing 2 in which the cartridge opening 5 is formed, and a drum that is detachably attached to the main body casing 2 through the cartridge opening 5. A frame 50 and a developing cartridge 19 that can be attached to and detached from the cartridge mounting portion 52 of the drum frame 50 are provided.

Further, as shown in FIG. 2, the drum frame 50 includes a photosensitive drum 20 and a scorotron charger 22, and the developing cartridge 19 includes a developing roller 34 and a layer thickness regulating blade 35.

Therefore, for example, when the photosensitive drum 20 reaches the end of its life, only the drum frame 50 can be replaced, and when the developing roller 34 reaches the end of its life, only the developing cartridge 19 can be replaced.

Therefore, the running cost can be reduced as compared with the case where both the photosensitive drum 20 and the developing roller 34 are provided in one cartridge.

As a result, it is possible to suppress the occurrence of image formation defects while reducing the running cost.
(5) The printer 1 also includes a supply roller 33 for supplying toner to the developing roller 34 as shown in FIG.

Therefore, the toner can be reliably supplied to the rubber roller 66 of the developing roller 34.

Further, the developing roller 34 has a peripheral surface of the drum body 57 positioned on the front side (one side) and a sponge roller 64 with respect to an imaginary straight line L1 passing through the shaft center A1 of the photosensitive drum 20 and the shaft center A2 of the supply roller 33. Are disposed between the common tangent line B of the peripheral surface of the drum body 57 and the common tangent line C of the peripheral surface of the drum body 57 and the peripheral surface of the sponge roller 64 located on the rear side (the other side).

Therefore, an efficient arrangement of the photosensitive drum 20, the developing roller 34, and the supply roller 33 can be ensured, and the printer 1 can be downsized.
(6) Further, the developing roller 34 is arranged so that its axis center A3 is located on the virtual straight line L1.

Therefore, further efficient arrangement of the photosensitive drum 20, the developing roller 34, and the supply roller 33 can be ensured, and the printer 1 can be further reduced in size.
4). Modification The printer 1 described above is an embodiment of the image forming apparatus of the present invention, and the present invention is not limited to the above-described embodiment.

The image forming apparatus of the present invention can be configured as a color printer in addition to the above-described monochrome printer.

When the image forming apparatus is configured as a color printer, the image forming apparatus includes a direct tandem type color printer including a plurality of photosensitive members and a recording medium conveying member, a plurality of photosensitive members, an intermediate transfer member, and a transfer member. It can be configured as an intermediate transfer type tandem color printer.

Further, the process cartridge 15 may be configured as an integral type integrally including the drum cartridge 18 and the developing cartridge 19 in addition to the separation type in which the drum cartridge 18 and the developing cartridge 19 are separated as described above.

Further, the photosensitive drum 20 can be provided in the main casing 2 as an example of the casing, and only the developing cartridge 19 can be attached to and detached from the main casing 2.

Further, the developing cartridge 19 can be configured such that a toner cartridge that contains toner is detachably attached to a frame having the developing roller 34.

Further, in place of the above-described photosensitive drum 20, for example, a photosensitive member such as a photosensitive belt can be applied.

Further, instead of the developing roller 34 described above, for example, a developer carrier such as a developing sleeve, a developing belt, or a brush-like roller can be applied.

Further, instead of the above-described supply roller 33, for example, a supply member such as a supply sleeve, a supply belt, or a brush-like roller can be applied.

Further, instead of the agitator 29 described above, for example, a conveying member such as an auger screw or a conveying belt can be applied.

Further, instead of the transfer roller 21 described above, for example, a contact type transfer member such as a transfer belt, a transfer brush, a transfer blade, or a film type transfer device, or a non-contact type transfer member such as a corotron type is used. It can also be applied.

Further, instead of the above scorotron charger 22, for example, a non-contact charger such as a corotron charger, a sawtooth discharge member, or a contact charger such as a charging roller may be applied. it can.

Further, instead of the scanner unit 16 described above, an exposure member such as an LED unit can be applied.

Furthermore, the image forming apparatus of the present invention can also be configured as a multi-function machine equipped with an image reading unit and the like.

Also by these, the same effect as the above-described embodiment can be obtained.

Note that the above-described embodiments and modifications can be combined as appropriate.

DESCRIPTION OF SYMBOLS 1 Printer 2 Main body casing 5 Cartridge opening part 16 Scanner unit 19 Developing cartridge 20 Photosensitive drum 22 Scorotron charger 23 Discharge wire 33 Supply roller 34 Developing roller 35 Layer thickness control blade 50 Drum frame A1 Shaft center A2 of photosensitive drum Axis center A3 Axis center N of developing roller Contact portion L1 A virtual straight line A passing through the axis center A1 and the axis center A2 A common surface line B L1 of the discharge wire and the rubber roller A front surface of the drum body and the periphery of the sponge roller The common tangent line F between the peripheral surface of the drum body and the peripheral surface of the sponge roller on the rear side with respect to the common tangent line C L1 with the surface. Tangent direction P1 of the peripheral surface of the rubber roller at the contact portion N The intersection of the common axis A and the drum body P2 exposure point

Claims

A photoreceptor (20);
A developing roller (34) arranged to face the surface of the photoconductor (20) and configured to carry a developer to be supplied to the surface of the photoconductor (20);
A layer thickness regulating blade (35) configured to regulate the layer thickness of the developer carried on the circumferential surface of the developing roller (34), which is in contact with the circumferential surface of the developing roller (34);
A charger (22) facing the surface of the photoconductor (20) and disposed above the developing roller (34) and configured to charge the surface of the photoconductor (20); Prepared,
The image forming apparatus according to claim 1, wherein a tangential direction (F) of the peripheral surface of the developing roller (34) at a contact portion with the layer thickness regulating blade (35) is substantially the same as a vertical direction.
The charger (22) has a circular cross-sectional shape in a direction orthogonal to the axial direction of the developing roller (34), and is a discharge member configured to discharge when a voltage is applied from the outside. 23)
The discharge member (23) is arranged so that all common tangent lines (A) between the peripheral surface of the discharge member (23) and the peripheral surface of the developing roller (34) overlap the photoconductor. The image forming apparatus according to claim 1, wherein the image forming apparatus is characterized.
An exposure device (16) configured to form an electrostatic latent image on the surface of the photoreceptor (20) by laser light;
The photoreceptor (20) is configured to rotate,
At least one intersection of the common tangent and the photoconductor (20) is arranged on the downstream side in the rotation direction of the photoconductor (20) with respect to the incident position of the laser beam on the photoconductor (20). The image forming apparatus according to claim 2, wherein the image forming apparatus is an image forming apparatus.
The image forming apparatus according to claim 2, wherein the discharge member (23) is a discharge wire (23) disposed along an axial direction of the developing roller (34).
A housing (2) in which an opening (5) is formed;
A photoconductor frame (50) comprising the photoconductor (20) and the charger (22) and configured to be detachably mounted on the housing (2) through the opening (5). When,
The developing roller (34) and the layer thickness regulating blade (35), and further comprising a developing cartridge (19) detachably attached to the photoreceptor frame (50). The image forming apparatus described.
A supply roller (33) arranged to face the development roller (34) along the axial direction of the development roller (34) and configured to supply developer to the development roller (34);
The photoconductor (20) is a photoconductive drum (20) disposed along the axial direction,
The developing roller (34)
The peripheral surface of the photosensitive drum (20) and the supply roller (on one side) with respect to an imaginary straight line (L1) passing through the axial center of the photosensitive drum (20) and the axial center of the supply roller (33). 33) a first common tangent line (B) that is a common tangent line of the peripheral surface, and a second common tangent line of the peripheral surface of the photosensitive drum (20) and the peripheral surface of the supply roller (33) located on the other side. The image forming apparatus according to claim 1, wherein the image forming apparatus is arranged between the common tangent line (C).
The image forming apparatus according to claim 6, wherein the developing roller (34) is arranged such that an axial center thereof is positioned on the virtual straight line (L1).