JP4596453B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, a printer, or a multifunction machine having both functions.

  Conventionally, as an image forming apparatus, a photosensitive unit including a protective cover that covers an exposed portion of a photosensitive drum when taken out from the main body of the image forming apparatus and moves to a retracted position when attached to the main body of the image forming apparatus. In some cases, the developing unit having a developing sleeve (magnet roller) as an image forming unit is configured separately. In this type of image forming apparatus, a photoreceptor 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 described above, for example, jumping development is performed, and the toner is blown onto the drum surface to form a toner image composed of a thin toner layer. In such development, the development sleeve is arranged at a certain distance (development gap) from the surface of the photosensitive drum. In the case of an image forming apparatus in which the photosensitive unit and the developing unit are configured separately, means for keeping the developing gap constant is necessary to output a stable image.

  Therefore, for example, in order to maintain a constant developing gap between the photosensitive drum rotatably supported on the photosensitive unit side and the developing sleeve rotatably supported on the developing unit side, Gap forming rollers for defining a developing gap are provided coaxially with the developing sleeve at both ends of the rotation shaft of the sleeve. The radius of the gap forming roller is set to be larger than the radius of the developing sleeve by the developing gap. The developing gap between the photosensitive drum and the developing sleeve can be kept constant by bringing the peripheral surface of the gap forming roller into contact with the peripheral surface of the photosensitive drum.

  As described above, in the image forming apparatus in which the photosensitive unit and the developing unit are configured separately, when the developing unit is inserted after the photosensitive unit is mounted on the main body of the image forming apparatus, the gap forming roller is inserted. The developing unit is pressed to the photosensitive drum side because it needs to be reliably applied to the photosensitive drum. Therefore, the developing sleeve tends to escape upward along the surface of the photosensitive drum. In order to improve this phenomenon, a developing unit position holding member has been conventionally attached to the image forming apparatus main body.

  In Patent Document 1, in an image forming apparatus in which a photosensitive unit and a developing unit are separately formed, during maintenance to open the developing unit, the opposite side of the photosensitive drum to the developing sleeve is covered. Further, there is shown a technique in which a protective cover is provided so as to be retracted from the opposite side of the photosensitive drum when the developing unit is closed.

  In Patent Document 2, the entire developing device is covered with a cover portion, and the developing device is supported so as to be pivotable about a fulcrum shaft, and the developing device is provided on the cover portion. A technique is shown in which an abutting roller is provided to hold the developing gap constant at both ends of the developing sleeve.

JP-A-2-272464 (2nd page, FIG. 1) JP-A-1-2003380 (page 3, Fig. 2)

  However, as in the prior art described above, in order to prevent the developing unit mounted on the image forming apparatus main body from escaping upward along the surface of the photosensitive drum, the number of components is not provided. Will increase work man-hours, leading to increased costs. Further, when the conventional protective cover is attached to the image forming apparatus main body, it does not perform any function and only occupies the space, resulting in narrowing the degree of freedom in designing the image forming apparatus main body. Become. Therefore, it would be advantageous if this protective cover could be used to prevent the developing unit mounted on the image forming apparatus main body from escaping upward along the surface of the photosensitive drum.

  Patent Document 1 does not disclose a technique for preventing the developing unit attached to the image forming apparatus main body from escaping upward along the surface of the photosensitive drum.

  Patent Document 2 has a structure in which the developing device is suspended and attached in the image forming apparatus main body, so that the developing device does not escape upward along the surface of the photosensitive drum. There is a problem that it is not easy to attach and detach the apparatus to and from the image forming apparatus main body.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of outputting a stable image while keeping a development gap constant with a simple structure.

  In the image forming apparatus according to the first aspect of the present invention, (1) a photosensitive 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. (2) A protective cover that protects the photosensitive drum is attached to the photosensitive unit so as to be rotatable from a shielding position that covers the photosensitive drum to an exposed position. (3) The developing unit is pressed toward the photosensitive unit in the image forming apparatus main body so that the photosensitive drum and the developing sleeve face each other with an appropriate developing gap.

The photosensitive unit includes a developing unit holding member that rotates integrally with the protective cover about a rotation axis, and a bias that constantly biases the protective cover toward the shielding position via the developing unit holding member. A member and an operation lever integrally attached to the developing unit holding member . When the photosensitive unit is inserted into the image forming apparatus main body, the operation lever comes into contact with an abutting member provided on the image forming apparatus main body, and is further inserted into the image forming apparatus main body. Then, the operation lever and the developing unit holding member are rotated against the urging force of the urging member by the contact member, and the protective cover is exposed to the position where the photosensitive drum is exposed. The developing unit holding member is rotated by the developing unit holding member so that the opening of the developing unit holding member faces the insertion direction of the developing unit into the image forming apparatus main body.

  The developing unit has a fitting protrusion at the front in the direction of insertion into the image forming apparatus main body. Then, after the photosensitive unit is inserted into the image forming apparatus main body after the developing unit is inserted into the image forming apparatus main body, the fitting protrusion is inserted into the opening of the developing unit holding member. And the fitting protrusion pushes up the hook portion of the opening so that the developing unit holding member rotates against the urging force of the urging member, and the urging force of the urging member The image forming apparatus main body is held at a predetermined position.

  According to the present invention, the developing unit holding member that rotates integrally with the protective cover has the urging member that urges the developing unit holding member in the shielding direction in which the protective cover covers the photosensitive drum. The mounted developing unit can be prevented from escaping upward along the surface of the photosensitive drum, whereby the developing gap can be kept constant and a stable image can be output.

Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings.
(Schematic configuration of image forming apparatus)
As shown in FIG. 1, an image forming apparatus 10 according to the present embodiment includes a sheet feeding unit 14 that feeds a sheet-like recording material 12 from a sheet feeding tray 13 into an image forming apparatus main body 11, and the sheet feeding unit 14. A sheet conveying unit 15 that conveys the recording material 12 fed from the recording medium 12 along the sheet conveying path R, an image forming unit 16 that transfers a toner image to the recording material 12 conveyed by the sheet conveying unit 15, and the image forming unit. A fixing device 17 for fixing the toner image on the recording material 12 onto which the toner image has been transferred by the unit 16; and a discharge unit 19 for discharging the recording material 12 on which the toner image has been fixed by the fixing device 17 onto a paper discharge tray 18. Are generally configured. Here, as the recording material 12, for example, paper, a plastic film, a cloth, an OHP sheet, or the like can be applied.

The image forming unit 16 includes a photoreceptor unit 30, a developing unit 40, a transfer roller 21, and the like. The photoconductor unit 30 and the developing unit 40 are configured separately from each other, and are guided by a pair of guide rails (not shown) formed in the image forming apparatus main body 11 so as to face each other. Has come to be supported.
(Configuration of photoconductor unit)
As shown in FIGS. 2 and 3, the photoconductor unit 30 includes a photoconductor drum 31 at a lower portion on the facing surface 30 </ b> A side facing the developing unit 40. A charger 32 is disposed above the photosensitive drum 31. Around the photosensitive drum 31 in the photosensitive unit 30, in addition to the charger 32, a static eliminator, a cleaner, and the like (not shown) are arranged toward the rotation upstream side of the charger 32. Further, laser light or the like can be incident on the photosensitive drum 31 from an exposure unit (not shown) on the downstream side of the charger 32 in the rotation direction.

  The photoconductor unit 30 includes two upper and lower bendable protective covers 50a and 50b that cover the photoconductor drum 31 exposed in a region extending from the surface 30A facing the developing unit 40 to the lower side. The protective covers 50 a and 50 b are made of, for example, synthetic resin, and a substantially rectangular plate having a width dimension substantially the same as the width dimension of the photosensitive drum 31 in the direction of the rotation shaft 33 is used as the outer peripheral surface of the photosensitive drum 31. It is formed by being curved so as to follow. Further, the protective covers 50 a and 50 b are rotated around the rotation shaft 33 of the photosensitive drum 31 so that the protective covers 50 a and 50 b can be rotated from the shielding position covering the photosensitive drum 31 to the exposed position. It is loosely fitted. When the protective covers 50a and 50b are rotated from the shielding position to the exposed position, only the lower protective cover 50b is first rotated in the exposure direction, and the upper protective cover 50a is also moved together with the protective cover 50b. Although it is configured to rotate, its details are omitted.

  In the present embodiment, as shown in FIGS. 4 and 5, the developing unit holding member 35 is attached to the rotary shaft 33 at a position where it does not interfere with the sheet passing on both sides in the width direction of the rotary shaft 33 of the photosensitive drum 31. It is loosely fitted freely. The protective covers 50 a and 50 b are pivotally attached to the developing unit holding member 35 via pivotal portions 52 and 53 on the left and right in the width direction of the rotation shaft 33. Further, the developing unit holding member 35 has a hook portion 35 a protruding toward the developing unit 40 in a state where the photosensitive unit 30 is inserted into the image forming apparatus main body 11.

  Further, when the developing unit 40 is inserted after the photosensitive unit 30 is inserted into the image forming apparatus main body 11, the developing unit holding member 35 is a fitting protrusion 49 (see FIG. 6) at the front of the developing unit 40. Has an opening 35b (see FIG. 2 and FIG. 3) into which is fitted. An operation lever 54 that is rotatable about the rotation shaft 33 is integrally attached to the developing unit holding member 35 on one side in the width direction of the rotation shaft 33 of the photosensitive drum 31. Then, by rotating the operation lever 54 counterclockwise in FIG. 2, the developing unit holding member 35 is rotated in the same direction (counterclockwise in FIG. 2) together with the protective covers 50a and 50b, so The body drum 31 is exposed.

  Further, the photosensitive unit 30 of the present embodiment urges the developing unit holding member 35 in the direction of the arrow in FIG. 2 (clockwise direction), thereby covering the photosensitive drum 31 with the protective covers 50a and 50b (see FIG. A torsion spring (biasing member) 37 that biases in the direction of the arrow in FIG. 2 is provided. One end of the torsion spring 37 is brought into contact with the rib 34 formed on the main body side of the photosensitive unit 30, and the other end of the torsion spring 37 is brought into contact with the rib portion 35 c formed in the developing unit holding member 35. (See FIG. 2). The developing unit holding member 35 (and the protective covers 50a and 50b) is urged by the urging force of the torsion spring 37 in the shielding direction (the arrow direction in FIG. 2) in which the protective covers 50a and 50b cover the photosensitive drum 31.

  As described above, when the photoreceptor unit 30 is inserted into the image forming apparatus main body 11, the operation lever 54 described above comes into contact with a contact member (main body side rib) (not shown) provided on the image forming apparatus main body 11 side. The developing unit holding member 35 (and the protective covers 50a and 50b) is rotated counterclockwise in FIG. 2 about the rotation shaft 33 against the urging force of the torsion spring 37. When the developing unit 40 is inserted after the photoconductor unit 30 is inserted into the image forming apparatus main body 11, the opening of the developing unit holding member 35 is inserted just before being inserted to the proper position as shown in FIG. 6. A fitting protrusion 49 at the front portion of the developing unit 40 is fitted into 35b. In this state, the protective covers 50a and 50b are rotated to a position where the photosensitive drum 31 is exposed.

Further, when the photoreceptor unit 30 is inserted into the image forming apparatus main body 11, as shown in FIGS. 3 and 10, the rotating shaft 33 protruding from both sides in the width direction of the photoreceptor drum 31 is provided with the image forming apparatus. It is guided and supported along a pair of rails 38 formed on both sides in the width direction of the main body 11.
(Development unit configuration)
As shown in FIGS. 1, 6, and 7, the developing unit 40 has a developing sleeve 41 that is opposed to the photosensitive drum 31 while holding a developing gap at the bottom of the surface facing the photosensitive unit 30. Is provided. Further, on the front part of the developing unit 40 in the direction of insertion into the apparatus main body, fitting protrusions 49 that fit into the developing unit holding member 35 of the photosensitive unit 30 described above are formed on both sides in the width direction. Further, a toner replenishing portion 43 for replenishing toner and a toner hopper 42 are formed at the rear of the developing unit 40 in the direction of insertion into the apparatus main body. Further, the projecting unit 40 is provided with three projecting shafts 44, 45, and 46 in order from the both sides in the width direction to the front to the rear in the insertion direction.

As shown in FIGS. 6, 7, and 10, such a developing unit 40 has two projecting shafts 44 and 46 of the image forming apparatus main body 11, similarly to the rotating shaft 33 of the photosensitive unit 30. It is guided and supported along a pair of rails 47 formed on both sides in the width direction, and one protruding shaft 45 is guided and supported along the pair of rails 47. Further, the developing unit 40 is pressed toward the photosensitive unit 30 by an urging means such as a spring (not shown) in the image forming apparatus main body 11.
[Operation and operation of image forming apparatus]
Next, the operation and operation of the image forming apparatus having the above-described configuration will be described.

  First, when the photosensitive unit 30 is removed from the image forming apparatus main body 11, as shown in FIG. 2, the developing unit holding member 35 is maximized in the arrow direction (clockwise) in the figure by the biasing force of the torsion spring 37. The protective cover 50 covers the exposed portion of the photosensitive drum 31. When the photoreceptor unit 30 is inserted into the image forming apparatus main body 11, as shown in FIG. 6, the photoreceptor unit 30 is rotatable about the rotation shaft 33 of the photoreceptor drum 31 and integrated with the developing unit holding member 35. The operation lever 54 comes into contact with a contact member (not shown) provided on the image forming apparatus main body 11 side, and the developing unit holding member 35 (and the protective covers 50a and 50b) is moved around the rotation shaft 33 as shown in FIG. Rotate counterclockwise to position.

  When the developing unit 40 is further inserted deeper from the position shown in FIG. 6 to the normal position in the image forming apparatus main body 11, the fitting protrusion at the front portion of the developing unit 40 is inserted into the opening 35 b of the developing unit holding member 35. 49 is fitted, and the hooking portion 35a of the developing unit holding member 35 is slightly pushed up by the fitting projection 49 upward in FIG. By this push-up, the developing unit holding member 35 rotates in the counterclockwise direction in FIG. As shown in FIGS. 8 and 9, when the developing unit 40 is inserted to the proper position, the fitting protrusion 49 of the developing unit 40 is moved by the developing unit holding member 35 (by the biasing force of the torsion spring 37). 8 and 9, the developing unit 40 is held in a predetermined position.

  As shown in FIG. 11, inclined surfaces B and C are formed on the upper surface of the fitting protrusion 49 of the developing unit 40, and the upper surface of the fitting protrusion 49 and the hook portion 35 a of the developing unit holding member 35 are formed. Is in contact at the contact point D. The urging force P from the hook portion 35a acts on the contact point D between the hook portion 35a and the fitting protrusion 49 to generate the component forces q and r, thereby preventing the developing unit 40 from being lifted. Needless to say, the development gap can be accurately maintained and good development can be achieved. Thus, the developing unit 40 mounted on the image forming apparatus main body 11 can be prevented from escaping upward (in the direction of arrow A in FIG. 8) along the surface of the photosensitive drum 31.

  The present invention can be used in the field of image forming apparatuses such as copying machines, facsimile machines, printers, or multifunction machines having both functions.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment. It is a side view of a photoreceptor unit. It is a perspective view of a photoreceptor unit. It is a perspective view of a photoreceptor unit. It is a front view of a photoconductor unit. It is a side view of a photoreceptor unit and a developing unit. It is a perspective view of a developing unit. FIG. 3 is a side view of a state in which the photosensitive unit and the developing unit are mounted on the image forming apparatus main body. It is a perspective view same as the above. FIG. 3 is a side view of the image forming apparatus main body with the photoreceptor unit and the developing unit insertion rails attached thereto. FIG. 10 is an enlarged view showing a contact state between the fitting protrusion of the developing unit and the hook portion of the developing unit holding member.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Image forming apparatus, 11 ... Image forming apparatus main body, 30 ... Photoconductor unit, 31 ... Photoconductor drum, 33 ... Rotating shaft, 35 ... Development unit holding member, 35a ... Hook part, 35b ... Opening, 37 ... Torsion spring (biasing member), 40 ... Developing unit, 41 ... Developing sleeve, 50a, 50b ... Protective cover

Claims (1)

A photosensitive unit having a photosensitive drum and a developing unit having a developing sleeve are detachably provided on the image forming apparatus main body,
A protective cover for protecting the photosensitive drum is attached to the photosensitive unit so that the protective cover can be rotated from a shielding position covering the photosensitive drum to a position to be exposed.
In the image forming apparatus, the developing unit is pressed toward the photosensitive unit side in the image forming apparatus main body so that the photosensitive drum and the developing sleeve are opposed to each other while maintaining an appropriate developing gap.
The photosensitive unit is:
A developing unit holding member that rotates integrally with the protective cover about a rotation axis; a biasing member that constantly biases the protective cover toward the shielding position via the developing unit holding member; and the developing unit An operating lever integrally attached to the holding member ,
When inserted into the image forming apparatus main body, the operation lever comes into contact with an abutting member provided on the image forming apparatus main body, and when further inserted into the image forming apparatus main body, the operation lever and The developing unit holding member is rotated by the contact member against the urging force of the urging member, and the protective cover is rotated by the developing unit holding member to a position where the photosensitive drum is exposed. And the opening of the developing unit holding member opens so as to face the insertion direction of the developing unit into the image forming apparatus main body,
The developing unit is
Having a fitting protrusion at the front in the direction of insertion into the image forming apparatus main body,
When the photosensitive unit is inserted into the image forming apparatus main body and then inserted into the image forming apparatus main body, the fitting protrusion fits into the opening of the developing unit holding member, and The hook of the opening is pushed up so that the fitting protrusion rotates the developing unit holding member against the urging force of the urging member, and the urging force of the urging member causes the inside of the image forming apparatus main body. Held in place,
An image forming apparatus.

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