Image forming device

Abstract

To provide an image forming device capable of improving user operability when a component is taken out from a device body with a structure stabilized in development performance.SOLUTION: An image forming device 1 comprises: an image forming unit; a development separation mechanism; and a development pressure mechanism 12. The development separation mechanism moves a development unit 63 from a development position to a separation position when the image forming unit is pulled out from a device body. The development pressure mechanism 12 biases the development unit 63 toward a photosensitive drum 61 in a direction in which contact pressure between a development roller 632 and the photosensitive drum 61 increases. The development pressure mechanism 12 changes the biasing direction of the development unit 63 so as to reduce moment around a rotary shaft 65 as the development unit 63 moves from the development position to the separation position.SELECTED DRAWING: Figure 19

Description

Technical Field

[0001] The present invention relates to an image forming apparatus.

Background Art

[0002] In image forming apparatuses such as copiers and printers, maintenance or replacement of components may be required, for example, when a predetermined number of printed sheets is reached. For this reason, the image forming apparatus may be configured such that a photoreceptor drum (image carrier) and a developing unit are detachable from the main body of the image forming apparatus.

[0003] For example, a conventional image forming apparatus disclosed in Patent Document 1 includes a support member that supports a developing unit. The support member is movable between a first position where a developing roller is in contact with the photoreceptor drum and a second position where the developing roller is separated from the photoreceptor drum more than the first position. When removing the developing unit from the apparatus main body, the support member moves to a predetermined position between the first position and the second position. This improves the operability related to attaching and detaching the developing unit.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Here, in order to stabilize the developing performance, the developing unit may be biased toward the photoreceptor drum. In this case, the biasing force applied to the developing unit becomes a load when removing components such as the photoreceptor drum and the developing unit from the apparatus main body, and there is a problem that the load is added to the load when removing. As a result, there is a concern that the user feels heavier when removing the component from the apparatus main body, and the operability of the user may be reduced.

[0006] The present invention has been made in view of the above points, and an object thereof is to provide an image forming apparatus having a configuration in which developing performance is stabilized and the operability of a user when removing a component from the apparatus main body can be improved.

Means for Solving the Problems

[0007] In order to solve the above problems, an image forming apparatus of the present invention includes an image forming unit, a developing separation mechanism, and a developing pressure mechanism. The image forming unit includes an image carrier on which an electrostatic latent image is formed on an outer peripheral surface, and a developer carrier that supplies toner to the electrostatic latent image to form a toner image, and a developing unit that is movable around a rotation axis between a developing position where the developer carrier contacts the image carrier and a separation position where the developer carrier is separated from the image carrier, and is pullable out from the apparatus main body. The developing separation mechanism moves the developing unit from the developing position to the separation position when the image forming unit is pulled out from the apparatus main body. The developing pressure mechanism biases the developing unit toward the image carrier in a direction in which the contact pressure between the developer carrier and the image carrier increases. The developing pressure mechanism changes the biasing direction of the developing unit so that the moment around the rotation axis decreases as the developing unit moves from the developing position to the separation position.

Effects of the Invention

[0008] According to the configuration of the present invention, a developing pressure mechanism is provided to stabilize developing performance. And the moment generated by the biasing force on the developing unit decreases as the developing unit moves from the developing position to the separation position. Thereby, the generation of other loads added to the load when pulling out the image forming unit from the apparatus main body can be suppressed. Therefore, it is possible to improve the operability of the user when pulling out the image forming unit from the apparatus main body with a configuration in which developing performance is stabilized.

Brief Description of the Drawings

[0009]

Figure 1

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Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the following content.

[0011] FIG. 1 is a schematic cross-sectional side view of an image forming apparatus 1 according to an embodiment. FIG. 2 is a schematic cross-sectional side view around an image forming unit 6 of the image forming apparatus 1 in FIG. 1. FIG. 3 is a perspective view showing a front view of the image forming apparatus 1 in FIG. 1 and a pulled-out state of an image forming unit 6U. As an example of the image forming apparatus 1 of the present embodiment, it is a tandem type color printer that receives image data and a print command related to a print job from an external computer and transfers a toner image onto a sheet S using an intermediate transfer belt 71. The image forming apparatus 1 may be a so-called multifunction machine having functions such as printing, scanning (image reading), and facsimile transmission.

[0012] In the drawings of this document, the direction indicated by the arrow Df is the front (front side) of the image forming apparatus 1, and the direction indicated by the arrow Db is the rear (back side) of the image forming apparatus 1. The direction indicated by the arrow Dx is the left-right lateral direction of the image forming apparatus 1 and is the axial direction of a roller-shaped member including a photosensitive drum 61 and a developing roller 632 described later.

[0013] As shown in FIGS. 1 and 2, the image forming apparatus 1 includes a paper supply unit 3, a paper conveyance unit 4, an exposure unit 5, an image forming unit 6, a transfer unit 7, a fixing unit 8, a paper discharge unit 9, and a control unit 10 provided in its apparatus main body 2.

[0014] The paper supply unit 3 is disposed at the bottom of the apparatus main body 2. The paper supply unit 3 stores a plurality of sheets of paper (recording medium) S before printing, and separates and feeds out the sheets of paper S one by one during printing. The paper conveyance unit 4 extends in the vertical direction along the side wall of the apparatus main body 2. The paper conveyance unit 4 conveys the sheet of paper S fed out from the paper supply unit 3 to the secondary transfer unit 73 and the fixing unit 8, and further discharges the sheet of paper S after fixing from the paper discharge port 4a to the paper discharge unit 9. The exposure unit 5 is disposed at the upper part of the apparatus main body 2. The exposure unit 5 irradiates laser light controlled based on image data toward the image forming unit 6.

[0015] The image forming unit 6 is disposed below the exposure unit 5 and above the intermediate transfer belt 71. The image forming unit 6 includes a yellow image forming unit 6Y, a cyan image forming unit 6C, a magenta image forming unit 6M, and a black image forming unit 6B. These four image forming units 6 have the same basic configuration. Accordingly, in the following description, the identification symbols "Y", "C", "M", and "B" representing each color may be omitted unless particularly limited.

[0016] The image forming unit 6 includes a photosensitive drum (image carrier) 61 rotatably supported in a predetermined direction (counterclockwise in FIGS. 1 and 2). The image forming unit 6 further includes a charging unit 62, a developing unit 63, and a drum cleaning unit 64 disposed around the photosensitive drum 61 along its rotation direction. Note that a primary transfer unit 72 is disposed between the developing unit 63 and the drum cleaning unit 64.

[0017] The photoreceptor drum 61 has a photosensitive layer formed on its outer peripheral surface. The charging unit 62 charges the outer peripheral surface of the photoreceptor drum 61 to a predetermined surface potential. The exposure unit 5 exposes the outer peripheral surface of the photoreceptor drum 61 charged by the charging unit 62, and forms an electrostatic latent image of the original image with attenuated charge on the outer peripheral surface of the photoreceptor drum 61. The developing unit 63 supplies toner to the electrostatic latent image on the outer peripheral surface of the photoreceptor drum 61 for development, and forms a toner image. Each of the four image forming units 6 forms a toner image of a different color. The drum cleaning unit 64 removes and recovers deposits such as toner remaining on the outer peripheral surface of the photoreceptor drum 61 after the toner image is primarily transferred to the outer peripheral surface of the intermediate transfer belt 71. In this way, the image forming unit 6 forms an image (toner image) to be later transferred to the paper S.

[0018] Note that the four image forming units 6 are mounted on the image forming unit 6U shown in FIG. 3. In this regard, the apparatus main body 2 includes an opening / closing door 2a and a guide portion (not shown). The opening / closing door 2a is disposed in front of the apparatus main body 2, and by opening it, the image forming unit 6U inside the apparatus main body 2 can be exposed. The guide portion extends in the front-rear direction inside the apparatus main body 2 and supports the image forming unit 6U so as to be slidable in the front-rear direction. When the opening / closing door 2a is opened as shown in FIG. 3, the image forming unit 6U can be pulled out and inserted with respect to the apparatus main body 2.

[0019] The transfer unit 7 includes an intermediate transfer belt 71, primary transfer units 72Y, 72C, 72M, 72B, a secondary transfer unit 73, and a belt cleaning unit 74. The intermediate transfer belt 71 is disposed below the four image forming units 6 and above the paper supply unit 3. The intermediate transfer belt 71 is rotatably supported in a predetermined direction (clockwise in FIGS. 1 and 2), and is an endless intermediate transfer member on which the toner images formed on the outer peripheral surfaces of the photoreceptor drums 61 in each of the four image forming units 6 are sequentially superposed and primarily transferred. The four image forming units 6 are arranged in a so-called tandem method in a row from the upstream side to the downstream side in the rotation direction of the intermediate transfer belt 71.

[0020] The primary transfer units 72Y, 72C, 72M, and 72B are arranged below the image forming units 6Y, 6C, 6M, and 6B for each color, sandwiching the intermediate transfer belt 71. The secondary transfer unit 73 is located upstream of the fixing unit 8 with respect to the paper conveyance direction of the paper conveyance unit 4 and downstream of the four image forming units 6Y, 6C, 6M, and 6B with respect to the rotation direction of the intermediate transfer belt 71. The belt cleaning unit 74 is arranged downstream of the secondary transfer unit 73 with respect to the rotation direction of the intermediate transfer belt 71.

[0021] The primary transfer unit 72 transfers the toner image formed on the outer peripheral surface of the photosensitive drum 61 to the outer peripheral surface of the intermediate transfer belt 71. In other words, the toner image is primarily transferred to the outer peripheral surface of the intermediate transfer belt 71 by the primary transfer units 72Y, 72C, 72M, and 72B for each color. Then, as the intermediate transfer belt 71 rotates, the toner images of the four image forming units 6 are continuously transferred and overlapped onto the intermediate transfer belt 71 at a predetermined timing, thereby forming a color toner image on the outer peripheral surface of the intermediate transfer belt 71 in which toner images of yellow, cyan, magenta, and black are overlapped.

[0022] The color toner image on the outer peripheral surface of the intermediate transfer belt 71 is transferred to the paper S that has been sent in synchronization by the paper conveyance unit 4 at the secondary transfer nip formed in the secondary transfer unit 73. The belt cleaning unit 74 removes and cleans the attachments such as toner remaining on the outer peripheral surface of the intermediate transfer belt 71 after secondary transfer. In this way, the transfer unit 7 transfers (records) the toner image formed on the outer peripheral surface of the photosensitive drum 61 to the paper S.

[0023] The fixing unit 8 is arranged above the secondary transfer unit 73. The fixing unit 8 heats and presses the paper S onto which the toner image has been transferred to fix the toner image to the paper S.

[0024] The paper discharge unit 9 is arranged above the transfer unit 7. The paper S on which the toner image has been fixed and the printing is completed is conveyed to the paper discharge unit 9. The paper discharge unit 9 allows the printed paper (printed matter) to be taken out from above.

[0025] The control unit 10 includes a CPU, an image processing unit, a storage unit, and other electronic circuits and components (none of which are shown). Based on the control programs and data stored in the storage unit, the CPU controls the operations of the respective components provided in the image forming apparatus 1 to perform processes related to the functions of the image forming apparatus 1. Each of the paper supply unit 3, the paper conveyance unit 4, the exposure unit 5, the image forming unit 6, the transfer unit 7, and the fixing unit 8 receives individual commands from the control unit 10 and cooperates to perform printing on the paper S. The storage unit is configured by a combination of a non-volatile storage device such as a program ROM (Read Only Memory), a data ROM, etc., and a volatile storage device such as a RAM (Random Access Memory).

[0026] Subsequently, regarding the configuration around the image forming unit 6, in addition to FIGS. 1, 2, and 3, FIGS. 4, 5, and 6 will be used for explanation. FIG. 4 is a schematic side view of the image forming unit 6U in FIG. 2. FIG. 5 is a side view of the developing separation mechanism 11 of the image forming apparatus 1 in FIG. 1. FIG. 6 is an exploded perspective view of the developing separation mechanism 11 in FIG. 5. Note that in FIG. 4, the drawings of the charging unit 62 and the drum cleaning unit 64 of the image forming unit 6 are omitted.

[0027] As shown in FIG. 2, the upper surface of the intermediate transfer belt 71, which faces the four image forming units 6, is inclined downward at a predetermined angle from the rear Db to the front Df. For example, in the present embodiment, the inclination angle is 3 degrees with respect to the horizontal plane. The guide unit (not shown) that supports the image forming unit 6U so as to be slidable in the front-rear direction is parallel to the upper surface of the intermediate transfer belt 71 and extends inclined with respect to the horizontal plane. As shown in FIGS. 2 and 4, the image forming unit 6U is pulled out from the apparatus main body 2 along the pulling-out direction X1 from the rear Db to the front Df, and is inserted into the apparatus main body 2 along the insertion direction X2 opposite thereto, from the front Df to the rear Db.

[0028] As shown in FIG. 3, the image forming unit 6U has a pair of side plates 6s positioned on the left and right when viewed from the front Df. The pair of left and right side plates 6s each extend in the front-rear direction and the vertical direction of the image forming apparatus 1. The photosensitive drums 61, charging units 62, developing units 63, and drum cleaning units 64 (all shown in FIG. 2) of each of the four image forming units 6 are supported between the pair of left and right side plates 6s.

[0029] As shown in FIG. 4, the developing unit 63 has a developing container 631, a developing roller (developer carrier) 632, a stirring paddle and a supply roller (not shown), a pair of bearing portions 633, and a drive gear 634.

[0030] The developing container 631 has an elongated shape extending along the axial direction Dx of the photosensitive drum 61 (the depth direction of the paper surface of FIG. 4, the left-right horizontal direction of the image forming apparatus 1), and is arranged with its longitudinal direction horizontal. The developing container 631 has an opening (not shown) in a part facing the photosensitive drum 61. The developing container 631 accommodates, for example, non-magnetic one-component toner as a developer. That is, the developing container 631 accommodates the toner to be supplied to the photosensitive drum 61.

[0031] The stirring paddle is arranged at the upper part inside the developing container 631. The stirring paddle is rotatably supported by the developing container 631 around an axis extending parallel to the photosensitive drum 61, and stirs the toner inside the developing container 631 by rotating around the axis. The supply roller is arranged at the lower part inside the developing container 631 and is arranged to face the developing roller 632. The supply roller is rotatably supported by the developing container 631 around an axis extending parallel to the photosensitive drum 61, and supplies toner to the outer peripheral surface of the developing roller 632 in the facing area with the developing roller 632.

[0032] The developing roller 632 is disposed at the opening of the developing container 631, and a part of it is exposed from the developing container 631. The developing roller 632 is disposed opposite to the photosensitive drum 61 and contacts the photosensitive drum 61. The developing roller 632 is rotatably supported by the developing container 631 so as to be rotatable about an axis extending parallel to the axis of the photosensitive drum 61. The developing roller 632 carries toner to be supplied to the outer peripheral surface of the photosensitive drum 61 in the facing area with the photosensitive drum 61. The developing roller 632 supplies the toner in the developing container 631 to the outer peripheral surface of the photosensitive drum 61, develops the electrostatic latent image, and forms a toner image.

[0033] A pair of bearing portions 633 are disposed on the outer surface of the developing container 631 and on the opposing surfaces of the pair of left and right side plates 6s of the image forming unit 6U, respectively. The pair of bearing portions 633 are disposed above the facing area between the developing roller 632 and the photosensitive drum 61. The pair of bearing portions 633 receive a pair of rotating shafts 65 provided on the pair of left and right side plates 6s of the image forming unit 6U, respectively. Note that the pair of rotating shafts 65 are provided on the opposing surfaces (inner surfaces) of the two side plates 6s with the developing container 631 and extend toward the developing container 631 along the axial direction Dx of the photosensitive drum 61 (the depth direction of the paper surface in FIG. 4, the left and right horizontal direction of the image forming apparatus 1). The developing unit 63 is supported by the side plate 6s so as to be rotatable (oscillatable) about the rotating shaft 65 via the rotating shaft 65.

[0034] The developing unit 63 is movable about the rotating shaft 65 between a developing position (the solid line position in FIG. 4) where the developing roller 632 contacts the photosensitive drum 61 and a separated position (the broken line position in FIG. 4) where the developing roller 632 is separated from the photosensitive drum 61. Note that the developing unit 63 is moved from the developing position to the separated position, that is, clockwise in FIG. 4, by a developing separation mechanism 11 described later. Further, a torsion coil spring (not shown) is disposed on the rotating shaft 65. The torsion coil spring biases the developing unit 63 in the direction of the developing position with respect to the separated position, that is, counterclockwise in FIG. 4.

[0035] The drive gear 634 is exposed from the developing container 631 on one side in the axial direction Dx of the photosensitive drum 61 (the depth direction of the paper in FIG. 4, the left - right horizontal direction of the image forming apparatus 1). The drive gear 634 meshes with the output gear 6g. The output gear 6g is rotatably supported by the side plate 6s of the image forming unit 6U that faces the developing unit 63 in the axial direction Dx of the photosensitive drum 61.

[0036] Specifically, when the developing unit 63 is disposed at the developing position (the solid - line position in FIG. 4), it meshes with the output gear 6g. Thereby, rotational driving force is transmitted to the developing roller 632, the stirring paddle, and the supply roller in the developing container 631. On the other hand, when the developing unit 63 is disposed at the separated position (the dashed - line position in FIG. 4), the meshing with the output gear 6g is released. Thereby, the transmission of rotational driving force to the developing roller 632, the stirring paddle, and the supply roller in the developing container 631 is blocked.

[0037] The image forming apparatus 1 includes a developing separation mechanism 11 shown in FIGS. 5 and 6. FIG. 5 is a side view of the developing separation mechanism 11 of the image forming apparatus 1 in FIG. 1. FIG. 6 is an exploded perspective view of the developing separation mechanism 11 in FIG. 5.

[0038] The developing separation mechanism 11 is provided on the side plate 7s on the left side of the transfer unit 7 when viewing the image forming apparatus 1 from the front Df. The transfer unit 7 has a pair of side plates 7s located on the left and right when viewed from the front Df. The intermediate transfer belt 71 is rotatably installed between the pair of left - right side plates 7s by a plurality of rollers (not shown).

[0039] As shown in FIGS. 5 and 6, the developing separation mechanism 11 includes a color separation lever 111C, a monochrome separation lever 111B, two pairs of link members 112, a plurality of separation members 113, a two - stage cam 114, a drive gear 115, and torsion coil springs 116, 117.

[0040] Both the color separation lever 111C and the monochrome separation lever 111B extend in the front-rear direction of the image forming apparatus 1. The color separation lever 111C is disposed on the rear Db side with respect to the monochrome separation lever 111B. The monochrome separation lever 111B is disposed on the front Df side with respect to the color separation lever 111C.

[0041] The color separation lever 111C and the monochrome separation lever 111B are arranged side by side with respect to the side plate 7s in the axial direction Dx (the depth direction of the paper surface in FIG. 5, the left-right horizontal direction) in the order of the color separation lever 111C and the monochrome separation lever 111B. FIG. 5 shows the postures of the color separation lever 111C and the monochrome separation lever 111B in a state where the four developing units 63 are arranged at the separation positions. At this time, approximately half of the front Df side portion of the color separation lever 111C and approximately half of the rear Db side portion of the monochrome separation lever 111B overlap when viewed from the axial direction Dx (the left-right horizontal direction) (see FIG. 5). Similarly, even in a state where the four developing units 63 are arranged at the developing positions, approximately half of the front Df side portion of the color separation lever 111C and approximately half of the rear Db side portion of the monochrome separation lever 111B overlap when viewed from the axial direction Dx (the left-right horizontal direction) (see FIG. 10).

[0042] The color separation lever 111C and the monochrome separation lever 111B are each supported by the side plate 7s via a pair of link members 112. Further, the color separation lever 111C and the monochrome separation lever 111B each support a separation member 113. The color separation lever 111C and the monochrome separation lever 111B each have a pair of hole portions 111h to which the pair of link members 112 are connected and a pin portion 111p to which the separation member 113 is connected.

[0043] The pair of hole portions 111h are disposed near the front end portions and the rear end portions of the color separation lever 111C and the monochrome separation lever 111B, respectively. The hole portions 111h are circular and penetrate the color separation lever 111C and the monochrome separation lever 111B along the axial direction Dx (the left-right horizontal direction).

[0044] The color separation lever 111C has three pin portions 111p arranged in accordance with the positions of the three-color developing units 63M, 63C, and 63Y for colors in the front-rear direction. The monochrome separation lever 111B has one pin portion 111p arranged near the front end portion in accordance with the position of the developing unit 63B for black. The pin portion 111p has a cylindrical shape and protrudes from the color separation lever 111C and the monochrome separation lever 111B along the axial direction Dx (left-right horizontal direction). Specifically, the three pin portions 111p of the color separation lever 111C protrude toward the monochrome separation lever 111B side, and the single pin portion 111p of the monochrome separation lever 111B protrudes toward the color separation lever 111C side.

[0045] The two pairs of link members 112 are respectively arranged between the color separation lever 111C and the side plate 7s and between the monochrome separation lever 111B and the side plate 7s. One pair of the link members 112 is connected to the pair of hole portions 111h of the color separation lever 111C. The other pair of the link members 112 is connected to the pair of hole portions 111h of the monochrome separation lever 111B.

[0046] The link member 112 is formed in a crank shape when viewed from the front Df or the rear Db. The link member 112 has a support shaft 112a formed at one end in the longitudinal direction of the crank shape and a connection shaft 112b formed at the other end. The support shaft 112a extends along the axial direction Dx (left-right horizontal direction) and is inserted into and connected to the hole portion 7sh provided in the side plate 7s. The connection shaft 112b extends along the axial direction Dx (left-right horizontal direction) and is inserted into and connected to the hole portion 111h provided in each of the color separation lever 111C and the monochrome separation lever 111B.

[0047] The side plate 7s, the color separation lever 111C, and one pair of link members 112, and the side plate 7s, the monochrome separation lever 111B, and the other pair of link members 112 respectively constitute a parallel link mechanism. That is, the color separation lever 111C and the monochrome separation lever 111B are each supported by a pair of link members 112 so as to maintain a posture inclined with respect to the horizontal plane along the pulling-out direction X1 and the insertion direction X2 (see FIG. 5). The color separation lever 111C and the monochrome separation lever 111B each place the developing unit 63 at the developing position (the solid line position in FIG. 4) when descending while maintaining the posture inclined with respect to the horizontal plane, and place the developing unit 63 at the separated position (the broken line position in FIG. 4) when ascending.

[0048] A torsion coil spring 116 is disposed on the support shaft 112a of the link member 112. The torsion coil spring 116 biases the link member 112 in the direction from the separated position of the developing unit 63 to the developing position, that is, clockwise in FIG. 5.

[0049] A plurality of separation members 113 are provided in a quantity corresponding to the developing unit 63. That is, in the present embodiment, the developing separation mechanism 11 includes four separation members 113. The color separation lever 111C supports three separation members 113 at three pin portions 111p. The monochrome separation lever 111B supports one separation member 113 at one pin portion 111p. The four separation members 113 are linearly arranged along the pulling-out direction X1 and the insertion direction X2 by being connected to the pin portions 111p of the color separation lever 111C and the monochrome separation lever 111B respectively.

[0050] The separation member 113 extends in the front-rear direction and the up-down direction, and is configured in a substantially flat plate shape that is rectangular when viewed from the axial direction Dx (left-right lateral direction). The separation member 113 has a hole portion 113h formed at one end in the longitudinal direction of the rectangular shape. The hole portion 113h penetrates the separation member 113 along the axial direction Dx (left-right lateral direction), and the pin portions 111p provided on the color separation lever 111C and the monochrome separation lever 111B are inserted and connected thereto.

[0051] Torsion coil springs 117 are arranged on the pin portions 111p of the color separation lever 111C and the monochrome separation lever 111B, respectively. The torsion coil springs 117 bias the separation member 113 to project upward with respect to the color separation lever 111C and the monochrome separation lever 111B, that is, in the clockwise direction in FIG. 5.

[0052] Further, the separation member 113 has a contact portion 113c at the other end on the side opposite to the one end in the longitudinal direction where the hole portion 113h is formed. The contact portion 113c is located rearward Db with respect to the hole portion 113h and faces rearward Db, and has a flat or curved surface that contacts the developing unit 63 (developing container 631). As the color separation lever 111C and the monochrome separation lever 111B each rise, the contact portion 113c contacts the developing unit 63, and as they descend, the contact portion 113c separates from the developing unit 63.

[0053] The two-stage cam 114 is substantially at the center of the region that overlaps when viewed from the axial direction Dx (left-right lateral direction) of the color separation lever 111C and the monochrome separation lever 111B with respect to the front-rear direction, and is disposed below the color separation lever 111C and the monochrome separation lever 111B. The two-stage cam 114 is rotatably supported by the drive shaft 7sx of the side plate 7s. The drive shaft 7sx has a cylindrical shape and projects along the axial direction Dx (left-right lateral direction) in the direction where the color separation lever 111C and the monochrome separation lever 111B are located with respect to the side plate 7s.

[0054] The two-stage cam 114 has an inner cam 114a and an outer cam 114b. The inner cam 114a and the outer cam 114b are arranged in the order of the inner cam 114a and the outer cam 114b with respect to the side plate 7s in the axial direction Dx (left-right horizontal direction). The inner cam 114a contacts the lower surface of the color separation lever 111C from below. The outer cam 114b contacts the lower surface of the monochrome separation lever 111B from below. The inner cam 114a has a major diameter portion formed in a sector shape with a central angle of about 180 degrees when viewed from the axial direction Dx (left-right horizontal direction). The outer cam 114b has a major diameter portion formed in a sector shape with a central angle of about 80 degrees when viewed from the axial direction Dx (left-right horizontal direction).

[0055] The two-stage cam 114 obtains power through the drive gear 115 and rotates. The two-stage cam 114 is controlled by the control unit 10 so as to stop rotating at three rotation angles: a first rotation angle (see FIG. 9) at which the minor diameter portions of both the inner cam 114a and the outer cam 114b contact the color separation lever 111C and the monochrome separation lever 111B, a second rotation angle (see FIG. 10) at which the major diameter portion of the inner cam 114a contacts the color separation lever 111C and the minor diameter portion of the outer cam 114b contacts the monochrome separation lever 111B, and a third rotation angle (see FIG. 11) at which the major diameter portions of both the inner cam 114a and the outer cam 114b contact the color separation lever 111C and the monochrome separation lever 111B.

[0056] The drive gear 115 is fixed to one end of the two-stage cam 114 along the axial direction of the drive shaft 7sx. The drive gear 115 is connected to a drive unit (not shown) including a drive source such as a motor and obtains rotational power from the drive unit. When the two-stage cam 114 rotates via the drive gear 115, the color separation lever 111C and the monochrome separation lever 111B that contact the inner cam 114a and the outer cam 114b respectively move sequentially in the vertical direction. Details of the operations of these color separation lever 111C and monochrome separation lever 111B will be described later.

[0057] Next, the operation of the developing separation mechanism 11 will be described with reference to FIGS. 7 to 11. FIGS. 7 and 8 are side views of the developing unit 63 disposed at the developing position and the separation position of the image forming unit 6U in FIG. 4. FIGS. 9 and 10 are side views showing the arrangement of the developing unit 63 in the color printing state and the monochrome printing state. FIG. 11 is a side view showing a state where all the developing units 63 are disposed at the separation position. Note that in FIGS. 7 to 11, the drawing of the separation member 113 is simplified.

[0058] As shown in FIGS. 7 and 8, the developing container 631 of the developing unit 63 has a contacted portion 631b. The contacted portion 631b is formed at the lower end of the developing container 631 and is located above the separation member 113. The contacted portion 631b faces forward Df and has a flat or curved surface that contacts the contact portion 113c of the separation member 113.

[0059] As shown in FIG. 7, when the color separation lever 111C and the monochrome separation lever 111B are lowered by the rotation of the two-stage cam 114, the separation member 113 is separated from the developing unit 63. The developing unit 63 is urged counterclockwise in FIG. 7 by the action of a torsion coil spring (not shown) disposed on the rotating shaft 65, and is disposed at the developing position shown in FIG. 7. The developing roller 632 of the developing unit 63 contacts the photosensitive drum 61. The drive gear 634 of the developing unit 63 meshes with the output gear 6g, and the rotational driving force is transmitted.

[0060] As shown in FIG. 8, when the color separation lever 111C and the monochrome separation lever 111B are raised by the rotation of the two-stage cam 114, the separation member 113 contacts the developing unit 63. Specifically, the contact portion 113c of the separation member 113 contacts the contacted portion 631b of the developing container 631. The developing unit 63 is moved clockwise in FIG. 8 against the urging force of the torsion coil spring disposed on the rotating shaft 65 by the operation of the developing separation mechanism 11, and is disposed at the separation position shown in FIG. 8. The developing roller 632 of the developing unit 63 is separated from the photosensitive drum 61. The meshing of the drive gear 634 of the developing unit 63 with the output gear 6g is released, and the transmission of the rotational driving force is blocked.

[0061] As shown in FIG. 9, when the two-stage cam 114 rotates to the first rotation angle, the minor diameter portions of both the inner cam 114a and the outer cam 114b are in contact with the color separation lever 111C and the monochrome separation lever 111B, and the two separation levers are descending. All four separation members 113 are separated from the developing unit 63, and all four developing units 63 are arranged at the developing positions.

[0062] As shown in FIG. 10, when the two-stage cam 114 rotates to the second rotation angle, the major diameter portion of the inner cam 114a contacts the color separation lever 111C, and the color separation lever 111C rises. Also, in this case, the minor diameter portion of the outer cam 114b is in contact with the monochrome separation lever 111B, and the monochrome separation lever 111B is descending. The separation members 113 facing the color developing units 63M, 63C, 63Y of three colors contact the color developing units 63M, 63C, 63Y, and the color developing units 63M, 63C, 63Y of three colors are moved to the separation positions. Also, the separation member 113 facing the black developing unit 63B is separated from the developing unit 63B, and the black developing unit 63B is arranged at the developing position.

[0063] As shown in FIG. 11, when the two-stage cam 114 rotates to the third rotation angle, the major diameter portions of both the inner cam 114a and the outer cam 114b are in contact with the color separation lever 111C and the monochrome separation lever 111B, and the two separation levers rise. All four separation members 113 contact the developing unit 63, and all four developing units 63 are moved to the separation positions.

[0064] Subsequently, the detailed configuration around the separation member 113 will be described with reference to FIGS. 12 and 13. FIG. 12 is a perspective view of the developing unit 63 and the separation member 113 in FIG. 8. FIG. 13 is a side view of the separation member 113 in FIG. 12. FIG. 12 shows a state where the separation member 113 contacts the developing unit 63 and the developing unit 63 is moved to the separation position.

[0065] The image forming unit 6U includes a protrusion 66 shown in FIG. 12. The protrusion 66 is provided on the left side plate 6s (see FIG. 3) when the image forming unit 6U is viewed from the front Df. The protrusion 66 is provided on the opposing surface (inner surface) of the side plate 6s facing the developing container 631 and the separating member 113. The protrusion 66 is formed in a cylindrical shape extending toward the developing container 631 and the separating member 113 along the axial direction Dx of the photosensitive drum 61.

[0066] In a state where the developing unit 63 is disposed at the separated position, the protrusion 66 faces the separating member 113 in the axial direction Dx (see FIGS. 12 and 14). Also, in a state where the developing unit 63 is disposed at the developing position, the protrusion 66 faces the developing container 631 in the axial direction Dx (see FIG. 16).

[0067] As shown in FIGS. 12 and 13, the separating member 113 has a retracting engaging portion 113e. The retracting engaging portion 113e projects toward the side plate 6s provided with the protrusion 66 along the axial direction Dx with respect to the main body portion 113m of the separating member 113 configured in a substantially flat plate shape that is rectangular when viewed from the axial direction Dx (left - right horizontal direction). The retracting engaging portion 113e extends from the location of the hole portion 113h to the intermediate portion up to the contact portion 113c along the longitudinal direction of the main body portion 113m.

[0068] The retracting engaging portion 113e has an inclined surface 113s. The inclined surface 113s is formed at the tip end portion on the contact portion 113c side in the longitudinal direction of the main body portion 113m in the retracting engaging portion 113e. The inclined surface 113s has an inclination that rises as it goes toward the front Df. The inclined surface 113s faces the outer peripheral surface of the cylindrical protrusion 66.

[0069] Next, the operation of the separation member 113 when the image forming unit 6U is pulled out from and inserted into the apparatus main body 2 will be described with reference to FIGS. 14 to 18. FIG. 14 is a side view showing the developing unit 63 and the separation member 113 disposed at the separation position when the image forming unit 6U is pulled out from the apparatus main body 2. FIG. 15 is a side view showing a state in which the separation member 113 is pushed down with respect to FIG. 14. FIG. 16 is a side view showing a state in which the developing unit 63 has passed over the separation member 113 with respect to FIG. 15. FIG. 17 is a side view showing a state in which the developing unit 63 contacts the separation member 113 when the image forming unit 6U is inserted into the apparatus main body 2. FIG. 18 is a side view showing a state in which the developing unit 63 has passed over the separation member 113 with respect to FIG. 17.

[0070] When the image forming unit 6U is pulled out from the apparatus main body 2, as shown in FIG. 14, as the image forming unit 6U moves in the pulling-out direction X1, the separation member 113 comes into contact with the developing unit 63 (developing container 631). As a result, the developing unit 63 is moved to the separation position.

[0071] Then, as the movement of the image forming unit 6U in the pulling-out direction X1 proceeds, as shown in FIG. 14, the protrusion 66 of the image forming unit 6U comes into contact with the retraction engaging portion 113e of the separation member 113. Specifically, the protrusion 66 comes into contact with the inclined surface 113s of the retraction engaging portion 113e.

[0072] Furthermore, as the movement of the image forming unit 6U in the pulling-out direction X1 proceeds, as shown in FIG. 15, the protrusion 66 slides on the inclined surface 113s of the retraction engaging portion 113e, and the image forming unit 6U moves forward in the direction Df. As a result, the protrusion 66 pushes down the separation member 113 via the retraction engaging portion 113e. Then, the lower end of the contacted portion 631b of the developing container 631 slides on the upper surface of the main body portion 113m of the separation member 113, and the image forming unit 6U further moves forward in the direction Df.

[0073] In this way, as shown in FIG. 16, all four developing units 63 can pass over the separation member 113, and the image forming unit 6U can be pulled out from the apparatus main body 2.

[0074] When the image forming unit 6U is inserted into the apparatus main body 2, as shown in FIG. 17, as the image forming unit 6U moves in the insertion direction X2, the developing unit 63 (developing container 631) comes into contact with the separation member 113. As a result, the separation member 113 rotates counterclockwise in FIG. 17 against the biasing force of the torsion coil spring 117. Then, as the movement of the image forming unit 6U in the insertion direction X2 progresses, the lower end of the contact portion 631b of the developing container 631 moves so as to slide on the upper surface of the main body portion 113m of the separation member 113.

[0075] In this way, as shown in FIG. 18, all four developing units 63 can pass over the separation member 113, and the image forming unit 6U can be inserted into and mounted in the apparatus main body 2.

[0076] The image forming unit 6U includes a developing pressure mechanism 12 shown in FIG. 19. FIG. 19 is a side view of the developing unit 63 and the developing pressure mechanism 12 in FIG. 7. FIG. 20 is a schematic partial enlarged side view of the developing pressure mechanism 12 in FIG. 19. FIGS. 21 and 22 are partial enlarged side views of the developing unit 63 and the developing pressure mechanism 12 arranged at the developing position and the separation position. In the figures before this, the drawing of the developing pressure mechanism 12 is omitted.

[0077] The developing pressure mechanism 12 is adjacent to the developing unit 63 and is arranged above the rotation axis 65 of the developing unit 63. In other words, the developing pressure mechanism 12 is arranged at a position on the opposite side across the rotation axis 65 with respect to the arrangement position of the developing roller 632 when viewed from the axial direction Dx (left - right horizontal direction). The developing pressure mechanism 12 is arranged in front Df of the developing unit 63 and faces the developing unit 63 (developing container 631) in the front - rear direction.

[0078] As shown in FIG. 19, the developing pressure mechanism 12 includes a housing member 121, a compression coil spring 122, and a pressing member 123.

[0079] The housing member 121 is fixed to the frame portion (not shown) of the image forming unit 6U. The housing member 121 is formed in a cylindrical shape extending in the front-rear direction in which one end on the front Df side is closed and the other end on the rear Db side is open. The housing member 121 houses the compression coil spring 122 and the pressing member 123 from the opening on the rear Db side.

[0080] The compression coil spring 122 is housed within the housing member 121. The compression coil spring 122 is arranged such that the central axis of the coil coincides with the axis of the cylindrical housing member 121. The compression coil spring 122 is disposed between the housing member 121 and the pressing member 123. The compression coil spring 122 biases the pressing member 123 toward the rear Db, in other words, biases the pressing member 123 toward the developing unit 63 side.

[0081] The pressing member 123 is housed in the housing member 121, and a part on the rear Db side is exposed from the opening of the housing member 121. The pressing member 123 is formed in a cylindrical shape with one end on the rear Db side closed, and contacts the developing unit 63 (developing container 631) at the tip on the rear Db side. That is, by obtaining the biasing force from the compression coil spring 122, the pressing member 123 contacts the developing unit 63 and biases the developing unit 63 toward the photosensitive drum 61 around the rotation shaft 65.

[0082] With the above configuration, the developing pressure mechanism 12 biases the developing unit 63 toward the photosensitive drum 61 in a direction in which the contact pressure between the developing roller 632 and the photosensitive drum 61 increases. Thereby, it becomes possible to stabilize the developing performance.

[0083] As shown in FIG. 20, the pressing member 123 has a first pressing contact surface 123a and a second pressing contact surface 123b. On the other hand, the developing container 631 has a first pressed contact surface 631c and a second pressed contact surface 631d.

[0084] As shown by the solid line in Fig. 20 and Fig. 21, the first pressure contact surface 123a contacts the first pressure-contact surface 631c of the developing unit 63 at the developing position. The first pressure contact surface 123a extends in a direction substantially orthogonal to the pulling-out direction X1 and the inserting direction X2 of the image forming unit 6U, or in a direction substantially orthogonal to the front-back direction of the image forming apparatus 1. That is, the direction of the urging force applied to the developing unit 63 by the developing pressure mechanism 12 generated on the first pressure contact surface 123a at the developing position is substantially parallel to the inserting direction X2 or the front-back direction (the left-right horizontal direction in Figs. 20 and 21).

[0085] As shown by the two-dot chain line in Fig. 20 and Fig. 22, the second pressure contact surface 123b contacts the second pressure-contact surface 631d of the developing unit 63 at the separated position. The second pressure contact surface 123b extends in a direction substantially parallel to the pulling-out direction X1 and the inserting direction X2 of the image forming unit 6U, or in a direction substantially parallel to the front-back direction of the image forming apparatus 1. That is, the direction of the urging force applied to the developing unit 63 by the developing pressure mechanism 12 generated on the second pressure contact surface 123b at the separated position is substantially orthogonal to the inserting direction X2 or the front-back direction (the left-right horizontal direction in Figs. 20 and 22).

[0086] The moment around the rotation axis 65 of the developing unit 63 by the developing pressure mechanism 12 at the separated position where the urging direction of the developing unit 63 is substantially orthogonal to the inserting direction X2 or the front-back direction is smaller than the moment around the rotation axis 65 of the developing unit 63 by the developing pressure mechanism 12 at the developing position where the urging direction of the developing unit 63 is substantially parallel to the inserting direction X2 or the front-back direction. That is, when the developing unit 63 moves from the developing position to the separated position, the contact area between the pressure member 123 and the developing unit 63 is changed from the first pressure contact surface 123a to the second pressure contact surface 123b, so that the moment around the rotation axis 65 of the developing unit 63 by the developing pressure mechanism 12 becomes smaller.

[0087] As described above, the developing pressure mechanism 12 changes the biasing direction of the developing unit 63 so that the moment about the rotation axis 65 decreases as the developing unit 63 moves from the developing position to the separated position. The developing separation mechanism 11 moves the developing unit 63 from the developing position to the separated position when the image forming unit 6U is pulled out from the apparatus main body 2 of the image forming apparatus 2. Thereby, generation of other loads added to the load when the image forming unit 6U is pulled out from the apparatus main body 2 can be suppressed. Therefore, it is possible to improve the user operability when the image forming unit 6U is pulled out from the apparatus main body 2 with a configuration in which the developing performance is stabilized by providing the developing pressure mechanism 12.

[0088] Also, as described above, in the developing pressure mechanism 12, the first pressure contact surface 123a contacts the developing unit 63 at the developing position, and the second pressure contact surface 123b contacts the developing unit 63 at the separated position. Then, as shown in FIG. 22, at the separated position, the second pressure contact surface 123b faces so as to oppose the central axis of the rotation axis 65 of the developing unit 63. That is, when the developing unit 63 moves to the separated position, the developing pressure mechanism 12 changes the biasing direction of the developing unit 63 in the direction of the rotation axis 65.

[0089] When the biasing force of the developing pressure mechanism 12 on the developing unit 63 acts in the direction of the rotation axis 65, the force for rotating the developing unit 63 about the rotation axis 65 becomes close to zero. That is, the moment about the rotation axis 65 with respect to the developing unit 63 becomes close to zero. Therefore, when the image forming unit 6U in which the developing unit 63 is disposed at the separated position is pulled out from the apparatus main body 2, it is possible to suppress the biasing force of the developing pressure mechanism 12 on the developing unit 63 from being added to the load when pulling out.

[0090] And the second pressure contact surface 123b is preferably formed such that the rotation axis 65 is located on the normal line at the contact point with the developing unit 63. Thereby, the force for rotating the developing unit 63 about the rotation axis 65 becomes zero. Therefore, when the image forming unit 6U is pulled out from the apparatus main body 2, it is possible to effectively prevent the biasing force of the developing pressure mechanism 12 on the developing unit 63 from being added to the load when pulling out.

[0091] Also, the first pressing contact surface 123a is preferably formed such that the rotation axis 65 is positioned on the tangent line at the contact point with the developing unit 63. Thereby, the force for rotating the developing unit 63 around the rotation axis 65 is maximized. Therefore, when the developing unit 63 is disposed at the developing position, the biasing force of the developing pressure mechanism 12 on the developing unit 63 becomes maximum, and it becomes possible to effectively improve the stabilization of the developing performance.

[0092] As described above, the embodiments of the present invention have been described. However, the scope of the present invention is not limited thereto, and various modifications can be made without departing from the gist of the invention.

[0093] For example, in the above embodiment, the image forming apparatus 1 is a so-called tandem type image forming apparatus for color printing. However, the present invention is not limited to such a model. The image forming apparatus may be an image forming apparatus having another configuration as long as it is a model including an image forming unit that can be pulled out from the apparatus main body.

Industrial Applicability

[0094] The present invention can be used in an image forming apparatus.

Explanation of Signs

[0095] 1 Image forming apparatus 2 Apparatus main body 6, 6B, 6Y, 6C, 6M Image forming section 6U Image forming unit 6s Side plate 7 Transfer section 7s Side plate 10 Control section 11 Developing separation mechanism 12 Developing pressure mechanism 61 Photoconductor drum 62 Charging section 63, 63B, 63M, 63C, 63Y Developing unit 64 Drum cleaning section 65 Rotation axis 71 Intermediate transfer belt 111B Monochrome separation lever 111C Color separation lever 112 Link member 113 Separation member 123 Pressing member 123a First pressing contact surface 123b Second pressing contact surface 631 Developing container 632 Developing roller (developer carrier) S Paper X1 Pull-out direction X2 Insertion direction

Claims

1. an image forming unit including: an image carrier having an electrostatic latent image formed on an outer peripheral surface thereof; and a developing section having a developer carrier that supplies toner to the electrostatic latent image to form a toner image, the developing section being movable about a rotation axis between a developing position where the developer carrier contacts the image carrier and a spaced position where the developer carrier is spaced from the image carrier; and the image forming unit being removable from a main body of the apparatus; a developing separation mechanism that moves the developing section from the developing position to the separated position when the image forming unit is pulled out from the apparatus main body; a developing pressure mechanism that biases the developing unit toward the image carrier in a direction in which a contact pressure between the developer carrier and the image carrier increases; Equipped with the developing and pressing mechanism changes a biasing direction of the developing unit so that a moment about the rotation axis becomes smaller as the developing unit moves from the developing position to the separated position.

2. 2 . The image forming apparatus according to claim 1 , wherein the developing and pressing mechanism changes a biasing direction of the developing unit in the direction of the rotation axis when the developing unit moves to the separated position.

3. the developing and pressing mechanism has a pressing member that contacts and presses the developing unit, The pressure member is a first pressure contact surface that contacts the developing unit at the developing position; a second pressure contact surface that contacts the developing unit at the separated position; having 3. The image forming apparatus according to claim 2, wherein the second pressure contact surface is formed such that the rotation axis is positioned on a normal line of a contact point with the developing unit.

4. 4. The image forming apparatus according to claim 3, wherein the first pressure contact surface is formed so that the rotation axis is positioned on a tangent line of a contact point with the developing unit.

Images