JP4478554B2 - Optical writing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an optical writing device covered with a cover member and an image forming apparatus including the optical writing device.

  In an image forming apparatus such as a printer or a copying machine, a light beam corresponding to image data is emitted from a light source, and the light beam is rotated and reflected by a rotary polygon mirror to form an image on a photoconductor. Light that includes an image optical system and a folding mirror for folding the light beam and guiding it to the photosensitive member, and irradiates the photosensitive member in a line, and on the other hand, includes a synchronous optical system that detects the scanning start timing of the light beam. One having a writing device is known.

  An electrostatic latent image is formed on the photosensitive member by the light beam emitted from the optical writing device, and the electrostatic latent image is developed by supplying toner to the photosensitive member on which the electrostatic latent image is formed. Thus, a toner image is formed, and the toner image formed on the photoreceptor is transferred to a recording medium by a transfer device. The recording medium on which the toner image has been transferred is subjected to a fixing process by a fixing device, and is then discharged out of the image forming apparatus.

  Such an image forming apparatus may be used at a low temperature or a high temperature by a user, and degradation of image quality must be avoided even if the temperature of the surrounding environment changes. Particularly in an optical writing device, it is important to suppress the amount of deviation of the light beam emitted from the light source from a desired position on the photosensitive member. As a countermeasure, it is common to place many optical elements in a housing using a material with a low coefficient of linear expansion so that changes in the posture and position of the optical elements due to temperature changes in the surrounding environment are minimized. is there.

  For example, in an optical writing device in which a storage unit that houses a deflection unit, an imaging unit, a reflection unit, and a scanning unit is hermetically sealed with a cover, scanning line bending or scanning line position shift caused by external vibration or thermal deformation is detected. In order to prevent image degradation and reduce image deterioration, an optical writing device is proposed in which the cover member is made of a material that is the same as or smaller than the linear expansion coefficient of the material forming the storage means. (For example, refer to Patent Document 1). However, since the thermal distribution of the optical writing device is actually not uniform, even if the linear expansion coefficient is the same, the thermal deformation is not necessarily eliminated.

  In addition, for example, with respect to a sealed structure of an optical box with an opening at the top and a cover that closes the opening, the cover is formed of resin and engaged with the optical box for the purpose of improving detachability while maintaining the sealing performance of the cover. The structure which formed the latching piece to perform and inserted the elastic member in the latching | locking part of a latching piece and an optical box is proposed (for example, refer patent document 2).

  In order to distinguish the description of this embodiment from the embodiment of the present invention, the cover (30) is made of resin and has a plurality of hook portions (31). When the tip of 31) is hooked on the hooked portion (29) of the housing (2), the space (32) is formed between the hooking portion (31) and the housing (2) when the cover (30) is closed. The hook (31) cannot be moved by filling the space, the cover (30) is prevented from being removed, and an elastic body is used as a means for filling the space.

  In such a configuration, the hooks (31) of the cover (30) are configured so as not to allow the cover (30) to be displaced upward in the figure with respect to the housing (2) at a plurality of locations, and means for eliminating thermal deformation It is thought that it does not function as.

  In the current optical writing apparatus, the housing and the cover are composed of a plurality of members having different linear expansion coefficients, and as a result of pulling between the members, the posture and position of the optical element may be changed. Many. In particular, since the cover member is often configured to be attached to a portion where the strength of the upper opening of the housing is lowered, a countermeasure is required.

JP 2000-137184 A JP 2002-277795 A

  The present invention relates to an optical writing device capable of suppressing the change in the posture and position of an optical element by avoiding the occurrence of pulling of a cover with respect to a housing even when a thermal change in the ambient environment of the optical writing device occurs. It is an object to provide an image forming apparatus.

The present invention to achieve the above objects, a housing optical element is mounted, in an optical writing device having a cover member for closing the housing on the opening, fastened between two members of the housing and the cover member has a fastening means at a plurality of positions, said fastening means, said cover includes a plurality of snap-fit feature to use the deflection of the member, corresponding to the fastening means, in the widthwise direction of the dust-proof member provided on the cover The same number of substantially the same shape is arranged at both end portions in the front-rear direction of the housing, and the plurality of snap-fit shapes are provided on the outer wall portions located at both end portions in the front-rear direction of the housing. A protrusion 31d having a triangular prism shape having a slope inclined with respect to the vertical direction in which the hem tends to spread outward as it goes, and provided at both ends in the front-rear direction of the cover, 1d, a rectangular hole 71d formed in a convex portion 71e partially convex downward, and the protrusion 31d is mounted under the condition that the cover is attached to the housing. A gap Δ1 is formed in the vertical direction between the lower end portion of the protrusion 31d and the lower end portion of the hole 71d. A gap of Δ2 is formed between the outer wall and the outer wall in the front-rear direction. In an optical writing apparatus having a housing to which an optical element is attached and a cover member for closing an opening on the housing, there are a plurality of fastening portions between the housing and the cover member, and the fastening means includes two members. The gap is not completely fastened and fixed in all directions (claim 1). Here, it is not excluded that the linear expansion coefficients of the housing and the cover coincide. The fastening means may be constituted by a screw that is screwed with an elastic member interposed therebetween. Here, a spring or a washer can be used as the elastic member. A stepped screw can be used as the screw. As said fastening means, it can comprise with the snap-fit form which utilizes the bending of a member. An image forming apparatus may be configured using the optical writing apparatus having such a configuration.

  The present invention provides an optical writing apparatus and an image forming apparatus capable of preventing the cover from being pulled against the housing even when the ambient environment undergoes a thermal change and suppressing changes in the posture and position of the optical element. can do.

Embodiments of the present invention will be described below.
[1] Image Forming Apparatus An example of an image forming apparatus suitable for carrying out the present invention will be described with reference to FIG. In an approximately central portion inside the main body case 2 of the color printer 1 as an image forming apparatus, four image forming units 3 (3Y, 3C, 3M, 3K), an optical writing device 4 for emitting a light beam, and a transfer An intermediate transfer belt 5 as a belt is disposed. Each image forming unit 3 is a part for forming an image (toner image) of a different color. In the description of the present specification and drawings regarding the components of each image forming unit 3, the suffixes Y, C, M, and K attached to the numbers are yellow, cyan, and magenta corresponding to each image forming unit. , Showing the color of black.

  The main body case 2 includes a photosensitive iron holding member and a belt holding member, which is an iron frame made of metal, and a resin cover attached to the frame. Each image forming unit 3, optical writing device 4. The intermediate transfer belt 5 is attached to the frame.

  The four image forming units 3Y, 3C, 3M, and 3K have the same basic structure except that the colors of the formed images are different because the colors of the toners used are different. Each image forming unit 3 includes a photosensitive member 6 (6Y, 6C, 6M, 6K) that is rotationally driven in the direction of an arrow, a charging unit 7, a developing unit 8, a cleaning unit 9, and the like disposed around the photosensitive member 6. Has been.

  The photoreceptor 6 is formed in a cylindrical shape and is rotationally driven by a drive source (not shown). A photosensitive layer is provided on the outer peripheral surface portion of the photosensitive member 6, and the outer peripheral surface 6 a which is the surface of the photosensitive member 6 is a scanned surface. When the light beam emitted from the optical writing device 4 is spot-irradiated on the outer peripheral surface 6a of the photosensitive member 6, an electrostatic latent image corresponding to the image information is written on the outer peripheral surface 6a of the photosensitive member 6.

  The charging unit 7 uniformly charges the outer peripheral surface 6 a of the photoconductor 6, and a non-contact type is used for the photoconductor 6. The developing unit 8 supplies toner to the photoconductor 6, and the supplied toner adheres to the electrostatic latent image written on the outer peripheral surface 6 a of the photoconductor 6, thereby causing the electrostatic latent image on the photoconductor 6. The toner image is visualized as a toner image, and a non-contact type is used for the photoreceptor 6.

  The cleaning unit 9 cleans residual toner adhering to the outer peripheral surface 6 a of the photoconductor 6, and a brush contact type in which a brush contacts the outer peripheral surface 6 a of the photoconductor 6 is employed.

  The intermediate transfer belt 5 is a loop belt formed with a resin film or rubber as a base, and a toner image formed on the photoreceptor 6 is transferred to the intermediate transfer belt 5. The intermediate transfer belt 5 is supported by rollers 11, 12, and 13 and is driven to rotate in the arrow direction. These rollers 11, 12, 13 are attached to the frame of the main body case 2, whereby the intermediate transfer belt 5 is attached to the frame of the main body case 2 via the rollers 11, 12, 13.

  Therefore, the rollers 11, 12, and 13 are belt holding members that hold the intermediate transfer belt 5 as a transfer belt together with the frame of the main body case 2. Here, the linear expansion coefficients of these rollers 11, 12, 13 are the same as the linear expansion coefficient of the main body case 2. On the inner peripheral surface side (inside the loop) of the intermediate transfer belt 5, there are four pieces that press the intermediate transfer belt 5 against the photoreceptor 6 in order to transfer the toner image on each photoreceptor 6 onto the intermediate transfer belt 5. A transfer roller 14 is disposed. On the outer peripheral surface 6 a side (outside the loop) of the intermediate transfer belt 5, a cleaning unit 15 that cleans residual toner, paper dust, and the like attached to the outer peripheral surface 6 a of the intermediate transfer belt 5 is disposed.

  Below the four image forming units 3 and the optical writing device 4 in the main body case 2, a paper feed cassette 16 on which recording media (paper sheets) are stacked and held is disposed. The recording media stacked and held in the paper cassette 16 are separated and fed in order from the highest one.

  In the main body case 2, a conveyance path 17 is formed through which a recording medium separated and fed from the sheet feeding cassette 16 is conveyed. On the conveyance path 17, a paper feed roller 18a, a registration roller 18b, an intermediate transfer roller 19, a fixing unit 20, a paper discharge roller 21 and the like are arranged.

  The registration roller 18b is a roller that is rotationally driven intermittently at a predetermined timing. By intermittently driving the registration roller 18b, the recording medium that has been transported to the position of the registration roller 18b and stopped is sent to a transfer position sandwiched between the intermediate transfer belt 5 and the intermediate transfer roller 19. At this transfer position, the toner image on the intermediate transfer belt 5 is transferred to the recording medium. Here, the intermediate transfer belt 5 and the intermediate transfer roller 19 constitute a transfer portion.

The fixing unit 20 is a part that fixes the toner image transferred onto the recording medium to the recording medium by applying heat and pressure. The recording medium on which the toner image is fixed in the process of passing through the fixing unit 20 is discharged onto a paper discharge tray 22 formed on the upper surface of the main body case 2 by a paper discharge roller 21.
[2] Optical Writing Device An optical writing device suitable for implementing the present invention will be described. FIG. 2 is a horizontal sectional view of the optical writing device 4, and FIG. 3 is a longitudinal side view of the optical writing device 4. As shown in FIGS. 2 and 3, the optical writing device 4 is of a so-called counter scanning type, and is an LD unit 41 (41Y, 41C) that is four laser light source units that are light source units that oscillate a light beam. , 41M, 41K), a deflector 42 that deflects and scans the light beam from each LD unit 41 in two symmetrical directions, and forms an image of the deflected and scanned light beam in a desired size on the photosensitive member 6. For example, an imaging optical system 43 that is a scanning lens unit composed of an fθ lens, a synchronous optical system 44 that detects the scanning start timing of the light beam, and a folding mirror 45 (for folding and guiding the light beam to the photosensitive member 6). An optical element such as 45a, 45b) is mounted in the housing 71, and the upper opening of the housing 71 is closed by the cover 71.

  The LD unit 41 is configured by a holding member 46 holding a laser light emitting element 48, a collimating lens that substantially collimates the divergent light emitted from the laser light emitting element 48, and a laser light emitting element driving circuit board. The deflector 42 includes a two-stage rotating polygon mirror 49, a polygon mirror motor 50 that rotates the rotating polygon mirror 49, a soundproof glass 51 that covers the rotating polygon mirror 49, and the like. The synchronous optical system 44 includes an imaging lens 44b, an electric circuit board 44d having a photoelectric element 44c, and a holding member (not shown) that holds them.

  In the optical writing device 4, color-separated image data input from a document reading device (scanner) or an image data output device (personal computer, word processor, facsimile receiver, etc.) (not shown) is used as a light source driving signal. According to the conversion, the laser light emitting element 48 in each LD unit 41 is driven to emit a light beam. The light beam emitted from each LD unit 41 is deflected through the aperture 52 for correcting the tilting, the cylinder lens 53, and the folding mirror 45a (however, only for the light beams emitted from the LD units 41Y and 41K). Thus, deflection scanning is performed in two symmetric directions by the rotating polygon mirror 49 rotated at a constant speed by the polygon mirror motor 50.

  The light beams deflected and scanned in two directions by the rotating polygon mirror 49 of the deflector 42 pass through the imaging optical system 43, are folded back by the folding mirror 45b, and are dust-proof members 34 made of a transparent member such as glass. Then, the surface of the photoconductor 6 for each color is spot-irradiated to write an electrostatic latent image. At this time, the irradiation angles of the four light beams to the photosensitive member 6 are substantially the same.

On the other hand, the synchronization optical system 44 for determining the write start timing returns the light beam that has passed through the imaging optical system 43 by the synchronization detection mirror 44a and receives it, and outputs a scan start synchronization signal. Here, since the original meaning of the synchronization detection is to take the timing of the scanning light, the synchronization optical system 44 may be installed so as to receive the light beam prior to the normal scanning. In order to detect a change in the speed (or time) of one scan, a detection means may be provided at the rear end of the scan. FIG. 2 shows a configuration in which synchronization is obtained before and after such scanning. Note that the folding mirror 45b in the vicinity of the rotary polygon mirror 49 in FIG.
[3] Optical Writing Device of the Present Invention FIGS. 4 to 14 are slightly different from the optical writing device 4 shown in FIGS. 2 and 3 in the arrangement and configuration of members. In addition to showing the entire optical writing device 40 having an optical writing function, a housing 310 to which an optical element is attached, a cover 710 for closing the upper opening of the housing 310, details of a cover attaching portion to the housing 310, and the like are shown. . Regarding the optical writing device 40, members having the same functions as those of the optical writing device 4 described above are denoted by the same reference numerals and description thereof is omitted.

  As shown in FIG. 4 in a plan view and in FIG. 5 in a perspective view, the housing 310 is a substantially rectangular housing having an upper opening. An optical element is attached inside. In FIG. 4, the direction in which the two imaging optical systems 43 face each other is the front-rear direction, and the direction orthogonal to the front-rear direction is the left-right direction. Also, the direction penetrating the paper surface is the vertical direction, the direction toward the back side of the paper surface is downward, and the opposite is upward. The same applies to other drawings.

  4 and 5, the upper surface of the housing 310 has a rectangular outline, and three screw holes 31 c are formed in the front-rear direction on the left portion thereof, and the front surface in the front-rear direction is similarly formed on the upper surface on the right side. Two screw holes 31c are formed at intervals.

  4 and 5, triangular prism-shaped protrusions 31 d protrude from the outer wall of the housing 310 in the front-rear direction. Two protrusions 31d are formed on the front side edge and two on the rear side edge. The detailed shape of the protrusion 31d is shown in an enlarged manner in FIG. 6, and the protrusion 31d has an inclined surface K inclined with respect to the vertical direction. The slope K is a slope whose bottom tends to spread outward as it goes down.

  FIG. 7 shows a cover member 710 that closes the upper opening of the housing 310. The cover member 710 has a substantially rectangular plate shape, and its shape and size are determined so as to be able to overlap and cover the housing 310. In the cover member 710, four dustproof members 34 that are long in the left-right direction and that pass through the laser light emitted from the LD unit 41, which is four laser light source units, pass through the optical element are arranged in the front-rear direction.

  A simple hole 71c for three screws is formed in the front-rear direction on the left side of the longitudinal direction (left-right direction) of the dust-proof member 34, and two screws are similarly spaced on the right upper surface in the front-rear direction. A simple hole 71c is formed so as to overlap with a screw hole 31c formed in the housing. Further, in FIG. 7, the front and rear ends of the cover 710 are L-shaped such as bent downward, and the positions corresponding to the protrusions 71d are partially convex downward. In addition, a rectangular hole 71d is formed in the convex portion 71e. FIG. 8 shows the hole 71d in an enlarged manner.

  A process of attaching the cover 710 to the housing 310 will be described.

  A cover 710 is placed from above the housing 310. At that time, the inner edge of the hole 71d slides with the inclined surface K of the protrusion 31d formed in the housing 310 to elastically deform the convex portion 71e, and when the inclined surface K gets over, the tip of the protrusion 31d penetrates the hole 71d. The cover 710 is attached to the housing 310 when the elastically deformed convex portion 71e returns to its original shape. The state where the tip of the protrusion 31d penetrates the hole 71d is shown in FIGS. Thus, a total of four protrusions 31 d formed on the housing 310 enter the four holes 71 c formed on the cover 710, and the cover 710 is held against the housing 310.

  As shown in FIG. 10, when the four protrusions 31d enter the holes 71d, the cover 710 is substantially positioned in the housing 310. At this time, the screw holes 31c of the housing 310 and the holes formed in the cover 710 71c substantially matches. Therefore, as shown in FIGS. 10 and 13, the stepped screw 80 is threaded from the upper side of the cover 710 via the spring 85 through the hole 71 c and the screw hole 31 c in this order and tightened. FIG. 14 shows a state where the stepped screw 80 is tightened.

  In this attachment state, the dimensional relationship between the projection 31d and the hole 71d and the attachment state will be described with reference to FIGS. In the vertical direction, the cover 710 is on the upper surface of the housing 310, and a gap Δ1 is formed between the lower end of the protrusion 31d and the lower end of the hole 71d. A gap Δ2 is formed between the inner wall of each bent portion and the outer wall of the housing 310 at the front-rear direction end of the cover 710. Next, in the left-right direction, the width W2 of the protrusion 31d is smaller than the width W1 of the hole 71d.

  In the attachment portion using the stepped screw 80 in FIG. 14, a gap Δ3 is formed between the lower surface of the screw head of the stepped screw 80 and the upper surface of the cover 710, and an extensible spring 85 is interposed in the gap Δ3. The position 710 is held by an elastic force. Further, in the front-rear and left-right directions, the outer diameter of the stepped screw 80 is formed to be smaller than the diameter of the hole 71 so that the cover 710 is displaced with respect to the stepped screw 80 even if the housing 310 or the cover 710 is thermally deformed. It is possible.

  As described above, the cover 710 is attached to the housing 310 with respect to the housing 310 in the up and down direction and in the front and rear and right and left directions when an external force greater than the holding force by elasticity is applied. Can be shifted. The allowable shift amount is determined in consideration of the amount that the cover can absorb deformation due to thermal expansion.

  As described above, there are a plurality of fastening portions between the two members of the housing 310 and the cover 710 at the location of the stepped screw 80 and four locations at the location of the projection 31d, and the fastening means (stepped screw 80, projection 31d and hole 71d) are configured such that the two members of housing 310 and cover 710 are not completely fastened and fixed by providing sufficient dimensions in all directions (up and down, front and rear, left and right). Even if this thermal change occurs, it is possible to prevent the cover from being pulled against the housing and to prevent changes in the posture and position of the optical element.

  The fastening means is preferably an example of a stepped screw 80 that is screwed together with a spring 85 that is an elastic member, but is not limited thereto, and a spring washer may be used as the elastic member, or A material such as heat-resistant rubber may be used. Moreover, not only a stepped screw but a normal bolt can also be used.

In this example, a so-called snap-fit shape using the deflection (elastic deformation) of the convex portion provided with the opening 71d combined with the protrusion 31d is used, but other shapes using the same principle, for example, the end of the cover are used. It may be configured with an L-shaped elastic material, and the L-shaped piece may be hooked on the edge of the housing.

  Even under such a configuration, it is not excluded that the housing 310 and the cover 710 are made of the same material. Moreover, the position of the fastening part by a stepped screw is not restricted to the position shown in figure. Similarly, the snap fit feature that fixes the two members so as not to separate by utilizing the deflection of the members, for example, the engagement relationship between the protrusion 31d and the hole 71d is not limited to the illustrated position.

1 is a schematic configuration diagram of an image forming apparatus. It is a top view of an optical writing device. FIG. 2 is a diagram illustrating an optical writing device, a photoconductor, and the like in the image forming apparatus. It is the perspective view explaining the principal part of the conveying apparatus which concerns on the 2nd Embodiment of this invention. It is a perspective view of a housing. It is a perspective view of a protrusion. It is a perspective view of a cover. It is a perspective view of a convex part and a hole. It is a side view of an optical writing device. It is a perspective view of an optical writing device. It is sectional drawing explaining the engagement state of protrusion and a hole. It is the perspective view explaining the engagement state of a processus | protrusion and a hole. It is the perspective view explaining the attachment process by a stepped screw. It is sectional drawing explaining the attachment state by the stepped screw.

Explanation of symbols

31d Protrusion 71d Opening 80 Stepped screw 310 Housing 710 Cover

Claims (2)

In an optical writing device having a housing to which an optical element is attached and a cover member for closing an opening on the housing,
Has a fastening means for fastening between two members of the housing and the cover member at a plurality of positions, said fastening means includes a plurality of snap-fit feature to utilize flexure members, said fastening means, provided on the cover The same number of substantially the same shape is arranged on both ends of the cover corresponding to the short direction of the dustproof member and the front and rear directions of the housing,
The plurality of snap fit features are:
Protrusions in the form of triangular prisms having slopes inclined with respect to the vertical direction that are provided on each outer wall portion located at both ends in the front-rear direction of the housing and tend to spread outward as it goes down,
A rectangular hole provided at both ends in the front-rear direction of the cover, and a position corresponding to the protrusion is formed in a convex portion that is partially convex downward;
Under the state where the cover is attached to the housing, the protrusion enters the hole,
A gap of Δ1 is formed in the vertical direction between the lower end portion of the protrusion and the lower end portion of the hole, and the front-rear direction is formed between the inner wall of each bent portion and the outer wall of the housing at the front-rear end of the cover. An optical writing device is characterized in that a gap of Δ2 is formed . An image forming apparatus comprising the optical writing device according to claim 1 .

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