JP3948564B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus including a developing unit and a drum unit.

  As a conventional image forming apparatus, there is an apparatus in which a drum unit having a photosensitive drum and a developing unit having a developing sleeve (mag roller) as an image forming unit are configured separately. In this type of image forming apparatus, a drum unit and a developing unit are detachably provided in the main body of the image forming apparatus.

  After the electrostatic latent image is formed on the surface of the photosensitive drum of the above-described drum unit, for example, jumping development is performed to blow toner on the drum surface to form a toner image composed of a thin toner layer. . In such development, the developing sleeve is arranged at a certain distance (hereinafter referred to as a developing gap) from the surface of the photosensitive drum. In the case where the drum unit and the developing unit are configured separately, means for holding the developing gap is required.

  FIG. 6 shows a structure for holding a developing gap between the surface of the photosensitive drum 1 rotatably supported on the drum unit side and the developing sleeve 2 rotatably supported on the developing unit side. ing. As shown in FIG. 6, the developing sleeve 2 is set so that the rotating shaft 3 thereof is parallel to the rotating shaft of the photosensitive drum 1. Further, at both ends of the developing sleeve 2, a gap forming roller 4 for defining a developing gap is provided coaxially with the developing sleeve 2. The radius of the gap forming roller 4 is set to be longer than the radius of the developing sleeve 2 by the developing gap. The clearance between the photosensitive drum 1 and the developing sleeve 2 can be kept constant by bringing the peripheral surface of the gap forming roller 4 into contact with the peripheral surface of the photosensitive drum 1.

  As described above, in the image forming apparatus in which the drum unit and the developing unit are configured separately, when the developing unit is inserted after the drum unit is mounted on the image forming apparatus main body, the gap forming roller is provided on the photosensitive drum. In order to suppress the impact when directly hitting, measures such as changing the system of the developing unit and taking an insertion path so that the impact force does not act when the developing unit is inserted are taken. However, when these measures are taken, the inserting operation of the developing unit becomes unnatural or the certainty of the impact suppressing effect is low.

As another improved technique, an elastic member is interposed between the drum unit and the image forming apparatus main body, and the impact when the developing unit comes into contact with the drum unit is reduced by the elastic member ( For example, see Patent Document 1.)
Japanese Unexamined Patent Publication No. 3-84564 (page 4, FIG. 1)

  However, in the above-described conventional example in which an elastic member is interposed between the drum unit and the image forming apparatus main body, the moving speed when the developing unit abuts against the drum unit is not regulated. When the impact speed is high, the impact may damage the drum surface or deform the gap forming roller. Further, there is a risk that the toner may be ejected from the developing unit by impact.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus that can reduce the impact insertion force of the developing unit, reduce the impact force, and protect the drum surface.

  Another object of the present invention is to provide an image forming apparatus capable of preventing toner from being discharged from the developing unit by reducing the impact force.

According to the first aspect of the present invention, a drum unit having a photosensitive drum and a developing unit having a developing sleeve are detachably provided on the image forming apparatus main body, and a protective cover for protecting the photosensitive drum is provided on the drum unit. The present invention relates to an image forming apparatus provided so as to be rotatable between a position covering the photosensitive drum and a position where the photosensitive drum is opened and exposed, and the protective cover being urged toward a position covering the photosensitive drum. It is.

  In the image forming apparatus according to the present invention, the drum unit includes a buffer unit that propagates a repulsive force in a direction opposite to a direction in which the drum unit is inserted into the developing unit inserted into the image forming apparatus main body. The one end of the tension spring is fixed to the drum unit side, and the other end is fixed to an urging force transmission lever that is slidably supported with respect to the drum unit, and the urging force transmission lever is engaged with the protective cover. A protective cover engaging portion that opens and exposes the protective cover, and a developing unit engaging portion that engages the developing unit side, and the insertion of the developing unit into the image forming apparatus main body The protective cover is opened by sliding against the tension of the tension spring.

  According to the present invention, it is possible to obtain an image forming apparatus capable of reducing the impact insertion speed of the developing unit, reducing the impact force, and protecting the drum surface.

  In addition, according to the present invention, it is possible to prevent the toner from being blown out from the developing unit by reducing the impact force.

  Hereinafter, an image forming apparatus according to the best mode for carrying out the present invention will be described. In the image forming apparatus according to this embodiment, a drum unit having a photosensitive drum and a developing unit having a developing sleeve are detachably provided on the image forming apparatus main body. The drum unit is provided with a protective cover for protecting the photosensitive drum so as to be rotatable. The protective cover is urged so as to rotate in a direction to cover the photosensitive drum. The drum unit includes a buffering means for propagating a repulsive force on the opposite side to the direction in which the drum unit is inserted with respect to the developing unit inserted into the image forming apparatus main body. The buffer means has one end of a coil spring (tensile spring) fixed to the drum unit side and the other end fixed to an urging force transmission lever supported slidably with respect to the drum unit.

  The urging force transmission lever includes a protective cover engaging portion that engages with the protective cover to open and expose the protective cover, and a developing unit engaging portion that engages with the developing unit. The urging force transmission lever is slid as the developing unit is inserted into the image forming apparatus main body to open the protective cover.

  With such a configuration, when the developing unit is mounted on the image forming apparatus main body, the impact of the developing unit on the photosensitive drum can be reduced. In addition, according to the present embodiment, it is possible to reduce the impact insertion force of the developing unit, reduce the impact force, and protect the drum surface.

  In addition, according to the present embodiment, it is possible to prevent the toner from being blown out from the developing unit by reducing the impact force.

Hereinafter, details of an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings. However, it should be noted that the drawings are schematic and the ratio of dimensions of each member is different from the actual one. Moreover, the part from which the relationship and ratio of a mutual dimension differ also in between drawings is contained.
(Schematic configuration of image forming apparatus)
First, an outline of the image forming apparatus 100 will be described with reference to FIGS. 1 and 2. 1 is a perspective view of a main part showing a state in which the developing unit 120 is inserted in the image forming apparatus 100 according to the present embodiment, and FIG.

  As illustrated in FIGS. 1 and 2, the image forming apparatus 100 according to the present exemplary embodiment includes a drum unit 110 and a developing unit 120 that are detachably attached to the image forming apparatus main body 101. The drum unit 110 includes a photosensitive drum 111 that is driven to rotate. The developing unit 120 includes a toner container 121 that stores toner containing a magnetic material, and a developing sleeve 122 that supplies toner to the electrostatic latent image formed on the photosensitive drum 111 for development. Yes.

  On the drum unit 110 side, a rotation drive gear (not shown) that meshes with a rotation drive transmission gear (not shown) provided on the image forming apparatus main body 101 side is provided on the rotation shaft 111 </ b> A of the photosensitive drum 111. Further, the developing unit 120 is held while being pressed toward the drum unit 110 side. In this embodiment, the drum unit 110 and the developing unit 120 are arranged in the horizontal direction, and the developing unit 120 is set to a slightly higher position.

The image forming apparatus 100 according to the present exemplary embodiment includes an image forming unit (not illustrated) that transfers a toner image onto a sheet-like recording material that is fed from a sheet feeding tray (not illustrated) and conveyed along a sheet conveyance path, and the image. A fixing device (not shown) for fixing the toner image onto the recording material onto which the toner image has been transferred by the forming unit, and a discharging unit for discharging the recording material on which the toner image has been fixed via the fixing device onto a paper discharge tray (not shown). In general, it is structured.
(Drum unit configuration)
The drum unit 110 includes the above-described photosensitive drum 111 at the lower portion facing the developing unit 120. The photosensitive drum 111 is pivotally supported on the drum unit 110 by a rotating shaft 111A. Above the photosensitive drum 111 in the drum unit 110, a charger, a cleaner, a static eliminator and the like (not shown) are arranged. Further, for example, laser light can enter the photosensitive drum 111 from an exposure unit (not shown).

  Further, in the drum unit 110 of this embodiment, as shown in FIGS. 1 to 4, a protective cover 112 is provided to cover the surface of the photosensitive drum 111 facing the developing sleeve 122 side. The protective cover 112 is formed by bending a substantially rectangular plate having substantially the same width as the width of the photosensitive drum 111 in the rotation axis direction so as to follow the outer peripheral surface of the photosensitive drum 111.

  The protective cover 112 is rotatably supported by the support shaft 113 with respect to the main body of the drum unit 110 at the upper part on both sides in the width direction. The support portions on both sides of the protective cover 112 are integrally formed with a hook portion 114 that is supported by an intermediate portion penetrating the support shaft 113. The hook portion 114 protrudes on the opposite side of the protective cover 112 with the support shaft 113 interposed therebetween, and a first engaged portion 115 that engages with a buffer means 130 described later, and a side (upward) of the support shaft 113. A second engaged portion 116 that protrudes toward the center is formed. As shown in FIG. 4, the first and second engaged portions 115 and 116 in the hook portion 114 are engaged with a buffer means 130 to be described later, and rotate in the direction indicated by the thick arrow A to protect the cover. The photosensitive drum 111 is exposed by jumping up 112.

  Incidentally, as shown in FIG. 3, the protective cover 112 is urged toward the photosensitive drum 111 by the urging member 117. Further, the rotation of the protective cover 112 is restricted by a stopper member (not shown) so as not to contact the photosensitive drum 111. 3 shows a state where the protective cover 112 is slightly opened for convenience of explanation, but when the developing unit 120 is not mounted, the photosensitive drum 111 is always covered.

  Next, the configuration of the buffer means 130 will be described. As shown in FIGS. 3 and 4, the buffer means 130 includes an urging force transmission lever 131 formed of a rectangular frame and a coil spring (tensile spring) 132 as a spring member.

  The urging force transmission lever 131 has an elongated rectangular shape, and is slidable along a guide member provided in the main body of the drum unit 110 so as to be slidable along the insertion direction of the developing unit 120. . The lower end portion of the urging force transmission lever 131 is a first cover engaging portion 133 that engages with the first engaged portion 115 of the hook portion 114 described above. Further, the lower long side portion of the urging force transmission lever 131 is formed wide from the first cover engaging portion 133 from a position of a predetermined dimension, and this wide stepped portion is the first portion of the hook portion 114. 2 It becomes the 2nd cover engagement part 134 engaged with the to-be-latched part 116. FIG. Further, a developing unit engaging portion 135 that engages with the developing unit 120 side protrudes below the upstream portion of the biasing force transmission lever 131 in the insertion direction. The buffering means 130 is engaged with the developing unit 120 and the developing unit engaging portion 135 and slides in the inserting direction together with the developing unit 120. At that time, the first cover engaging portion 133 has an action of engaging the first engaged portion 115 of the hook portion 114 to jump up the protective cover 112 to a predetermined angle, and then the second cover engaging portion. The part 134 is set so as to engage with the second engaged part 116 of the hook part 114 and to flip up the protective cover 112 to the maximum extent.

The coil spring 132 serving as a tension spring has one end 132A located on the upstream side in the insertion direction of the developing unit 120 fixed to the main body side of the drum unit 110, and the other end 132B located on the downstream side in the insertion direction. The force transmission lever 131 is fixed to the end portion 131A on the downstream side in the insertion direction. The coil spring 132 is biased so as to pull the drum unit 110 side and the end 131A of the biasing force transmission lever 131. For this reason, the urging force transmission lever 131 is held in a state where the first cover engaging portion 133 is not engaged with the first engaged portion 115 when the developing unit 120 is not inserted.
(Development unit configuration)
As shown in FIG. 4, the developing unit 120 is provided with a developing sleeve 122 facing the photosensitive drum 111 with a predetermined developing gap at the lower part on the side facing the photosensitive drum 111. In addition, a toner storage unit 121 that stores toner is provided on the opposite side of the developing unit 120 from the side facing the photosensitive drum 111. A toner supply means (not shown) such as a paddle is provided between the toner container 121 and the developing sleeve 122 to supply toner to the developing sleeve 122 side.

An engaging projection 123 that engages with the developing unit engaging portion 135 of the urging force transmission lever 131 at the time of insertion is projected from an upper portion of the side surface of the main body of the developing unit 120. Further, on both side surfaces of the developing unit 120, guide convex portions 124 projecting sideways are formed. The guide convex portion 124 is guided along a guide rail (not shown) formed on the image forming apparatus main body 101 side.
(Operation and operation of image forming apparatus)
The image forming apparatus 100 according to the present embodiment is assembled to the image forming apparatus main body 101 by first mounting the drum unit 110 and then inserting the developing unit 120 along a guide rail (not shown). . When the developing unit 120 is inserted into the image forming apparatus main body 101 as shown in FIG. 1 after the drum unit 110 is mounted in this manner, as shown in FIG. The convex portion 123 is engaged with the developing unit engaging portion 135 of the urging force transmission lever 131 slidably provided on the drum unit 110 side, and moves the urging force transmission lever 131 in the insertion direction. Then, as shown in FIG. 4, the first cover engaging portion 133 of the urging force transmission lever 131 engages with the first engaged portion 115 of the hook portion 114 to open the protective cover 112 halfway.

  Further, when the urging force transmission lever 131 moves in the insertion direction, the second engaged portion 116 rises toward the urging force transmission lever 130 with the rotation of the hook portion 114, and the second cover engagement of the urging force transmission lever 131. The hook portion 114 is engaged with the portion 134 and further rotates to raise the protective cover 112 to the maximum extent.

  Thus, when the urging force transmission lever 131 moves in the insertion direction, the coil spring 132 is gradually stretched and the reaction force increases. This reaction force is transmitted to the developing unit 120 via the urging force transmission lever 131, so that a force directed to the side opposite to the insertion direction acts on the developing unit 120. For this reason, it is possible to suppress an increase in the insertion speed due to the weight of the developing unit 120 and the like, and it is possible to reduce the impact force when the drum unit 110 is attached. FIG. 5 shows a state where the developing unit 120 is held in contact with the drum unit 110.

Here, the restoring force F, which is the reaction force of the coil spring 132, is F = k · x, where k is the spring constant and x is the displacement amount, and therefore the greater the displacement amount is. For this reason, as the developing unit 120 approaches the drum unit 110, the resistance force against the insertion of the developing unit 120 increases, and the impact force on the photosensitive drum 111 is reduced. Finally, if a lock member for pressing the developing unit 120 against the drum unit 110 is provided, the holding force for pressing the developing sleeve 122 against the photosensitive drum 111 can be maintained. At this time, the resistance force by the coil spring 132 does not become a problem with respect to maintaining the development gap.
(Other examples)
It should not be understood that the above description and drawings, which form part of the disclosure of the embodiments of the present invention, limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  For example, in the above-described embodiment, the buffer unit 130 is configured by the rectangular urging force transmission lever 131 and the coil spring 132, but in addition to the urging force transmission lever 131, a plate-like body, a rod-like body, or the like is used. Of course, it is also possible to use other spring means.

  Moreover, the structure of the hook part 114 for flipping up the protective cover 112 is not limited to the above structure, and the engaged part may be single.

  Further, in the above-described embodiment, the urging force transmission lever 131 and the coil spring 132 are used as the buffering means between the drum unit 110 and the developing unit 120. However, other buffering means can be applied within the scope of the present invention. is there.

  The present invention can be used in the field of manufacturing an image forming apparatus such as a copying machine, a facsimile machine, a printer, or a multifunction machine having both functions.

1 is a perspective view showing a main part of an image forming apparatus according to an embodiment of the present invention. 1 is an explanatory cross-sectional view showing a main part of an image forming apparatus according to an embodiment of the present invention. 1 is a perspective view showing a main part of an image forming apparatus according to an embodiment of the present invention. FIG. 5 is a cross-sectional view showing the mounting operation of the drum unit and the developing unit in the image forming apparatus according to the embodiment of the present invention. FIG. 3 is a perspective view of a main part showing a state where the developing unit is mounted in the image forming apparatus according to the embodiment of the present invention. FIG. 3 is a perspective view showing a photosensitive drum and a developing sleeve.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Image forming apparatus, 101 ... Image forming apparatus main body, 110 ... Drum unit, 111 ... Photosensitive drum, 112 ... Protective cover, 114 ... Hook part, 115 ... First engagement part, 116 ...... Second engaged portion, 120... Development unit, 122... Development sleeve, 123 .. Engaging convex portion, 130... Buffering means, 131. ...... First cover latching section, 134 ...... Second cover latching section, 135 ... Development unit latching section

Claims (1)

A drum unit having a photosensitive drum and a developing unit having a developing sleeve are detachably provided on the main body of the image forming apparatus, and a protective cover for protecting the photosensitive drum on the drum unit covers a position where the photosensitive drum is covered. And an image forming apparatus that is pivotably provided between the opening and the exposed position, and the protective cover is biased toward a position that covers the photosensitive drum,
The drum unit includes a buffering means for propagating a repulsive force on a side opposite to a direction in which the drum unit is inserted into the developing unit inserted into the image forming apparatus main body.
The buffer means has one end of a tension spring fixed to the drum unit side and the other end fixed to an urging force transmission lever supported slidably with respect to the drum unit.
The urging force transmission lever includes a protective cover engaging portion that engages with the protective cover to open and expose the protective cover, and a developing unit engaging portion that engages with the developing unit. An image forming apparatus, wherein the protective cover is opened by sliding against a pulling force as the developing unit is inserted into a main body of the image forming apparatus.

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