JP5453216B2 - Optical scanning device and image forming apparatus having the same - Google Patents

Description

  The present invention relates to an optical scanning device for optically scanning a surface to be scanned and an image forming apparatus such as a copying machine and a printer provided with the optical scanning device.

  In an image forming apparatus such as a copying machine or a printer, a photoconductor whose surface is uniformly charged by a charger is optically scanned by an optical scanning device, and an electrostatic latent image corresponding to image information is formed on the surface. . The electrostatic latent image is developed by a developing device using toner as a developer to be visualized as a toner image, and the toner image is fixed after being transferred onto a recording material such as paper by a transfer device. A series of image forming operations is completed when the recording material is heated and pressurized by the apparatus and fixed on the recording material, and the recording material on which the toner image is fixed is discharged out of the apparatus.

  By the way, an optical scanning device that optically scans a photosensitive member to form an electrostatic latent image on a surface thereof includes a light source, a deflector that deflects a light beam emitted from the light source, and a deflector. A BD sensor that detects the scanning start timing on the surface to be scanned by the deflected light beam and a BD mirror that reflects the light beam and guides it to the BD sensor are accommodated.

  Such an optical scanning device has been miniaturized along with the miniaturization of the image forming apparatus. When the optical scanning device is miniaturized in this way, the distance between the scanning optical path of the image region and the BD detection optical path approaches, Arrangement of optical components becomes difficult, and secondary adverse effects such as flare easily occur.

  Regarding the holding of the BD mirror of the optical scanning device, for example, in Patent Documents 1 and 2, the reflecting surface of the BD mirror is abutted against the BD mirror holding portion standing on the housing, and the back surface of the BD mirror is integrated with the housing. The structure which hold | maintains a BD mirror by pressing with the formed mold spring is proposed.

JP 2002-328320 A JP 2002-341271 A

  However, in the case of adopting a configuration in which the synchronization signal is detected by light reflected near the edge of the BD mirror in order to reduce the size of the optical scanning device, the reflecting surface of the BD mirror cannot be sufficiently received by the housing, and the BD mirror This causes a problem that it cannot be stably held.

  The present invention has been made in view of the above problems, and an object thereof is to provide an optical scanning device capable of stably holding a BD mirror while achieving downsizing, and an image forming apparatus including the same. There is.

  In order to achieve the above object, a first aspect of the present invention is directed to a housing having a light source, a deflector for deflecting a light beam emitted from the light source, and a surface to be scanned by the light beam deflected by the deflector. In an optical scanning device that houses a BD sensor that detects the scanning start timing of the BD mirror and a BD mirror that reflects a light beam and guides it to the BD sensor, both ends of the reflecting surface of the BD mirror are formed in a casing. And holding the BD mirror in the casing by pressing the lower side of the straight line connecting the tip ends of the ribs at both ends of the reflection surface of the BD mirror with the convex portion of the leaf spring. It is characterized by.

  According to a second aspect of the present invention, in the first aspect of the present invention, a positioning recess is formed in the leaf spring, and a positioning boss formed on the housing is engaged with the positioning recess of the leaf spring, thereby making the leaf spring. Is positioned with respect to the housing.

  An image forming apparatus according to a third aspect includes the optical scanning device according to the first or second aspect.

  According to the first aspect of the present invention, even if the entire left and right edges of the BD mirror cannot be received by the casing in order to reduce the size of the optical scanning device, both ends of the reflecting surface of the BD mirror are used as the casing. Since it is received by two formed high and low ribs and pressed below the straight line connecting the ends of the ribs at both ends of the back surface of the reflecting surface of the BD mirror by the convex part of the leaf spring, the BD mirror is The housing can be reliably and stably held at a predetermined angle, and a stable BD detection can be realized by securing a BD detection optical path outside the scanning optical path.

  According to the second aspect of the present invention, since the leaf spring is positioned with respect to the housing by engaging the positioning boss of the housing with the positioning recess of the leaf spring, the position adjustment between the BD mirror and the BD sensor is performed. Is eliminated, and the assemblability of the optical scanning device is improved.

  According to the third aspect of the present invention, since writing to the photoconductor is started with high accuracy in the optical scanning device, a high-quality image can be stably obtained.

1 is a side sectional view of an image forming apparatus (laser printer) according to the present invention. 1 is a perspective view of an optical scanning device according to the present invention. It is a top view which shows the internal structure of the optical scanning device based on this invention. FIG. 4 is a perspective view of part A in FIG. 3. It is the A section enlarged detail drawing of FIG. FIG. 6 is a sectional view taken along line B-B in FIG. 5. It is CC sectional view taken on the line of FIG. It is a perspective view of a leaf | plate spring.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

[Image forming apparatus]
FIG. 1 is a longitudinal sectional view of an image forming apparatus according to the present invention. The illustrated image forming apparatus 1 is a laser printer, and an image forming unit 2 is disposed above the inside of the apparatus main body 1A. A sheet storage unit 3 is disposed in the lower half of the inside.

  The image forming unit 2 forms an image by electrophotography, and includes a photosensitive drum 4 as a rotatable photosensitive member, a charger 5 arranged around the photosensitive drum 4, a developing device 6, and a transfer device. In addition to the roller 7 and the cleaning device 8, the developing device 6 is provided with a toner hopper 9 for supplying toner as a developer. Next to the image forming unit 2, an optical scanning device (laser scanner unit (LSU)) 10 according to the present invention is arranged.

The paper storage unit 3 includes detachable upper and lower two-stage paper feed cassettes 11 and 12 in which a plurality of paper sheets are stacked and accommodated. 11 and 12 are provided with a pick roller 13 for sequentially taking out the papers from the upper one, a feed roller 14 for feeding out the taken papers one by one, and a retard roller 15. Are arranged with a first transport path S1 from the paper storage section 3 to the image forming section 2 and a second transport path S2 from the image forming section 2 to the paper discharge tray 16, and in the first transport path S1 A registration roller 17 and the transfer roller 7 are provided, and a fixing device 18, a conveyance roller 19, and a paper discharge roller 20 are provided in the second conveyance path S2. The fixing device 18 includes a fixing roller 18a and a pressure roller 18b that rotate in a pressure-contact state.

  Next, an image forming operation of the image forming apparatus 1 configured as described above will be described.

  When the image forming operation is started, in the image forming unit 2, the photosensitive drum 4 is rotationally driven in a direction indicated by an arrow (clockwise) in FIG. Uniformly charged. When a laser beam based on an electrical signal transmitted from a personal computer or the like is output from the optical scanning device 10 and the surface of the photosensitive drum 4 is exposed and scanned, an electrostatic latent image corresponding to image information is formed on the photosensitive drum 4. Is formed. The electrostatic latent image formed on the photosensitive drum 4 is developed by the developing device 6 using toner as a developer to be visualized as a toner image.

  By the way, when cassette feeding is performed, the sheets stored in, for example, the upper sheet feeding cassette 11 of the sheet storage unit 3 are picked up from the uppermost one by the pick roller 13, and 1 by the feed roller 14 and the retard roller 15. Each sheet is separated and conveyed to the registration roller 17 through the first conveyance path S1. In the registration roller 17, after the paper is temporarily in a standby state, the paper is supplied to the image forming unit 2 at a predetermined timing synchronized with the toner image on the photosensitive drum 4.

  In the image forming unit 2, the sheet supplied to the transfer nip between the photosensitive drum 4 and the transfer roller 7 is conveyed while being pressed against the photosensitive drum 4 by the transfer roller 7, so that the surface is exposed to the photosensitive drum. The toner image on 4 is transferred. The sheet onto which the toner image has been transferred is conveyed to the fixing device 18 and is heated and pressed in the process of passing through the fixing nip between the fixing roller 18a and the pressure roller 18b of the fixing device 18 to form a toner image. Get fixed. The toner remaining on the surface of the photosensitive drum 4 (transfer residual toner) after the transfer of the toner image onto the paper is removed by the cleaning device 8, and the photosensitive drum 4 whose surface has been cleaned is prepared for the next image forming operation.

  Thus, the sheet on which the toner image is fixed on the surface by the fixing device 18 is conveyed toward the sheet discharge roller 20 by the conveyance roller 19 through the second conveyance path S2, and is conveyed to the sheet discharge tray 16 by the sheet discharge roller 20. This completes a series of image forming operations.

[Optical scanning device]
Next, details of the optical scanning device 10 according to the present invention will be described with reference to FIGS.

  2 is a perspective view of the optical scanning device according to the present invention, FIG. 3 is a plan view showing the internal structure of the optical scanning device, FIG. 4 is a perspective view of portion A of FIG. 3, and FIG. 6 is a cross-sectional view taken along line BB in FIG. 5, FIG. 7 is a cross-sectional view taken along line CC in FIG. 5, and FIG. 8 is a perspective view of a leaf spring.

  As shown in FIG. 2, the optical scanning device 10 is configured by covering an upper surface opening of a casing 21 integrally formed with a resin in a rectangular box shape with a cover 22 made of resin, as shown in FIG. A laser diode 23 that is a light source is provided on a side portion of the housing 21, and a collimator lens 24, a cylindrical lens 25, and a deflection are arranged in the housing 21 along the emission direction of the laser beam from the laser diode 23. A polygon mirror 26 serving as a container is arranged on a straight line. The polygon mirror 26 is formed in a regular pentagon, and is rotated at high speed in the direction of the arrow (counterclockwise) in FIG. 3 by a polygon motor (not shown).

  In the housing 21, two fθ lenses 27 and 28 are arranged along the traveling direction of the laser beam deflected by the polygon mirror 26.

  Thus, a laser beam modulated in accordance with image data is emitted from the laser diode 23 which is a light source, and this laser beam is converted into a parallel light beam by the collimator lens 24. The parallel light beam is focused by a not-shown diaphragm provided in the collimator lens 24, and then imaged on the mirror surface of the polygon mirror 26 by a cylindrical lens 25 having power only in the sub-scanning direction, and is rotated at high speed. Is deflected by the polygon mirror 26. Then, the deflected laser beam is condensed at an equal speed by the fθ lenses 27 and 28 to form a condensed spot on the photosensitive drum 4 (see FIG. 1) as a surface to be scanned, and thereby the photosensitive drum 4. The top is exposed and scanned in the main scanning direction, and an electrostatic latent image corresponding to an image signal is formed on the photosensitive drum 4.

  By the way, a BD mirror 29 is arranged on one side outside the effective scanning range R by the laser beam in the housing 21, and a lens 30 and a BD sensor 31 are arranged on the other side. Here, the BD mirror 29 reflects the laser beam for synchronization detection reflected by the polygon mirror 26 and guides it to the BD sensor 31 through the lens 30. The BD sensor 31 detects the laser beam for synchronization detection. Thus, the exposure scanning (writing start) start timing on the photosensitive drum 4 by the laser beam within the effective scanning range R is determined.

  Incidentally, in the optical scanning device 10 according to the present embodiment, the BD mirror 29 is disposed close to the effective scanning range R in order to achieve downsizing, and the effective scanning range in which the photosensitive drum 4 is scanned as shown in FIG. The side of the casing 21 that supports the BD mirror 29 on the effective scanning range R side is cut away so as not to block the laser beam in R. That is, the BD mirror 29 is supported by a frame-shaped support portion 21 a erected on the casing 21 only on one side (side opposite to the effective scanning range R) and on the other side (effective scanning). The side portion on the range R side) is in a free state and is not supported by the housing 21.

  Thus, in the present embodiment, as shown in FIGS. 4 and 7, the reflecting surface of the BD mirror 29 is received by the two high and low ribs 21 </ b> A and 21 </ b> B whose left and right ends are erected on the housing 21. The back surface is pressed by a plate spring 32 made of a sheet metal provided on the back side of the BD mirror 29.

  Here, as shown in FIG. 8, the leaf spring 32 includes a lower horizontal portion 32A, a vertical portion 32B bent upward at a right angle from one end portion of the horizontal portion 32A, and the other end portion of the horizontal portion 32A. A spring portion 32C formed by bending is provided, and the upper end portion of the vertical portion 32B is bent toward the BD mirror 29 side. Then, on the left and right sides of the vertical portion 32B of the leaf spring 32, that is, on the side facing the rib 21A having a higher height standing on the casing 21, two upper and lower convex portions that bulge toward the rib 21A side. A (diaphragm) 32a is protruded, and one convex portion (diaphragm) 32a bulging toward the rib 21B is formed on the side facing the rib 21B on the lower side. In addition, semicircular cutout positioning recesses 32b are formed on the left and right sides of the 32 horizontal portions 32A of the leaf springs, and correspond to the positioning recesses 32b of the housing 21 when the leaf springs 32 are assembled. Positioning bosses 21b are erected vertically at the locations.

  Therefore, after the BD mirror 29 is incorporated into the housing 21 so that one side of the BD mirror 29 is fitted into the support portion 21 a of the housing 21 from above, a leaf spring is provided between the back surface of the BD mirror 29 and the housing 21. When the plate spring 32 is incorporated, the vertical positioning boss 21b formed in the housing 21 is engaged with the positioning recesses 32b formed in the left and right portions of the horizontal portion 32A so that the plate spring 32 is engaged with the housing 21. Is positioned. Also, the leaf spring 32 has two upper and lower convex portions 32 a formed on one side of the vertical portion 32 </ b> B pressing the back surface of the BD mirror 29, and one side of the reflecting surface of the BD mirror 29 is placed on the housing 21. While pressing the rib 21 </ b> A having the higher height, one convex portion 32 a formed on the left and right sides presses the back surface of the BD mirror 29, and the other side of the reflection surface of the BD mirror 29 is placed on the housing 21. The rib 21B having a low height is pressed. By adopting such a configuration, the three convex portions of the leaf spring 32 are located below the straight line connecting the tips of the ribs 21A and 21B at both ends of the back surface of the BD mirror 29 (the hatched area in FIG. 7). The BD mirror 29 is securely held by the housing 21 by being pressed by the member 32a.

  As described above, in the present embodiment, even if the entire left and right edges of the BD mirror 29 cannot be received by the housing 21 in order to reduce the size of the optical scanning device 10, the reflecting surface of the BD mirror 29. The leaf spring 32 is below the straight line connecting the tips of the ribs 21A and 21B at both ends of the back surface of the reflecting surface of the BD mirror 29, with both ends received by two high and low ribs 21A and 21B formed on the casing 21. The BD mirror 29 can be reliably and stably held at a predetermined angle on the casing 21 and the BD detection optical path is secured outside the scanning optical path and is stable. BD detection can be realized.

  In this embodiment, the leaf spring 32 is positioned with respect to the housing 21 by engaging the positioning boss 21b of the housing 21 with the positioning recess 32b formed in the horizontal portion 32A of the leaf spring 42. Therefore, it is not necessary to adjust the position of the BD mirror 29 and the BD sensor 31, and the assemblability of the optical scanning device 10 is improved.

  As described above, as a result of the BD mirror 29 being securely and stably held in the casing 21, writing to the photosensitive drum 4 is started with high accuracy in the optical scanning device 10, and the image forming apparatus shown in FIG. (Laser printer) 1 can stably obtain a high-quality image.

  Although the present invention has been described with respect to a mode in which the present invention is applied to a monochrome laser printer and an optical scanning device provided in the monochrome laser printer, the present invention is not limited to a color leather printer or a monochrome / color printer. Needless to say, the present invention can be similarly applied to any other image forming apparatus such as an image forming apparatus and an optical scanning device provided in the image forming apparatus.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 1A Image forming apparatus main body 2 Image forming part 3 Paper storage part 4 Photosensitive drum 5 Charging device 6 Developing device 7 Transfer roller 8 Cleaning device 9 Toner hopper 10 Optical scanning device (laser scanner unit)
DESCRIPTION OF SYMBOLS 11, 12 Paper feed cassette 13 Pick roller 14 Feed roller 15 Retard roller 16 Paper discharge tray 17 Registration roller 18 Fixing device 18a Fixing roller 18b Pressure roller 19 Carrying roller 20 Paper discharge roller 21 Optical scanning device case 21A, 21B Case Body rib 21a Housing support 21b Housing positioning boss 22 Cover 23 Laser diode (light source)
24 collimator lens 25 cylindrical lens 26 polygon mirror 27, 28 fθ lens 29 BD mirror 30 lens 31 BD sensor 32 leaf spring 32A leaf spring horizontal portion 32B leaf spring vertical portion 32C leaf spring spring portion 32a leaf spring convex portion 32b Plate spring positioning recess R Effective scanning range S1 First transport path S2 Second transport path

Claims (3)

In the housing, a light source, a deflector that deflects the light beam emitted from the light source, a BD sensor that detects scanning start timing on the surface to be scanned by the light beam deflected by the deflector, and a light beam In an optical scanning device that houses a BD mirror that reflects and guides it to the BD sensor,
The two ends of the reflecting surface of the BD mirror are received by two high and low ribs formed on the casing, and the convex portion of the leaf spring is below the straight line connecting the tips of the ribs at both ends of the back surface of the reflecting surface of the BD mirror. An optical scanning device characterized in that the BD mirror is held in the casing by being pressed by the lens.   The positioning spring is positioned with respect to the housing by forming a positioning recess in the leaf spring and engaging a positioning boss formed on the housing with the positioning recess of the leaf spring. The optical scanning device described. An image forming apparatus comprising the optical scanning device according to claim 1.

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