Optical scanning device, imaging forming apparatus, and optical element

An optical scanning device includes an optical element and an optical base. The optical element includes a first bonding surface, while the optical base includes a second bonding surface. A groove in which a bonding agent flows is formed in at least one of the first bonding surface of the optical element and the second bonding surface of the optical base. The optical element is bonded and fixed to the optical base through the first bonding surface and the second boding surface by means of the bonding agent.

INCORPORATION BY REFERENCE

The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2012-066629, filed Mar. 23, 2012. The contents of this application are incorporated herein by reference in their entirety.

BACKGROUND

The present disclosure relates to optical scanning devices in which an optical element is bonded and fixed to an optical base by means of a bonding agent, image forming apparatuses including such an optical scanning device, and optical elements.

In image forming apparatuses, such as copiers, printers, etc. that form images on a recording medium, such as paper by electrophotography, an image carrier of which surface is charged by a charger uniformly is subjected to exposure scanning by an optical scanning device to form an electrostatic latent image according to image information on the surface of the image carrier. The electrostatic latent image formed on the image carrier is developed with toner as a developer in a developing unit to be visualized as a toner image. Further, the toner image is transferred onto the recording medium through a transfer unit. The recording medium on which the toner image is thus transferred is conveyed to a fusing unit and then is heated and pressurized by the fusing unit to be subjected to fusing of the toner image. Thereafter, the recording medium to which the toner image is fused is ejected outside the apparatus. Upon ejection of the recoding medium outside the apparatus, a series of image forming operation is completed.

Incidentally, in the optical scanning device, light emitted from a light source, such as a laser diode (LD), or the like enters into a deflection means, such as a polygon mirror or the like through a collimator lens and a cylindrical lens. Then, the light deflected by the deflection means is imaged on an image carrier on a photoconductive drum or the like through an fθ lens. Subsequently, the image is subjected to exposure scan. In the optical scanning device, the optical elements, such as the collimator lens, the cylindrical lens, the fθ lens, etc. are directly fixed to an optical base by means of a bonding agent in order to reduce the number of parts.

Moreover, in order to maintain the high scanning performance of the optical scanning device, the optical elements, such as the fθ lens, etc. are bonded and fixed to the optical base with high accuracy. To do so, a positioning rib119A is formed so as to protrude from an optical base119, as shown inFIG. 6. An fθ lens124, for example, abuts on the positioning rib119A for positioning. Then, the positioned fθ lens124is fixed to the optical base119by means of a bonding agent130.

However, in the case employing the fixing scheme as described with reference toFIG. 6, when the fθ lens124and the optical base119are thermally expanded by driving the optical scanning device or the like, the shear stress concentrates at bonding points. Because, (1) the fθ lens124cannot be moved relative to the optical base119because of abutment of the fθ lens124on the positioning rib119A of the optical base119; (2) the fθ lens124has a coefficient of linear expansion different from the optical base119; and the like. As a result, the shear stress may overpower the bonding strength to cause the fθ lens124to come off from the optical base119.

By contrast, a method as shown inFIGS. 7A and 7Bhas been proposed as still another technique for fixing an fθ lens.

Specifically,FIGS. 7A and 7Bare cross sectional views showing the method for fixing an fθ lens. In the fixing method explained with reference toFIGS. 7A and 7B, in order to fix an fθ lens224to an optical base219by means of a bonding agent230, the fθ lens224is positioned accurately by using a jig250, as shown inFIG. 7A, and is bonded to the optical base219. Then, the jig250is removed, as shown inFIG. 7B.

SUMMARY

An optical scanning device according to one aspect of the present disclosure includes an optical element and an optical base. The optical element includes a first bonding surface, while the optical base includes a second bonding surface. A groove in which a bonding agent flows is formed in at least one of the first bonding surface of the optical element and the second bonding surface of the optical base. The optical element is bonded and fixed to the optical base through the first bonding surface and the second boding surface by means of the bonding agent.

An image forming apparatus according to one aspect of the present disclosure includes an optical element and an optical base. The optical element includes a first bonding surface, while the optical base includes a second bonding surface. A groove in which a bonding agent flows is formed in at least one of the first bonding surface of the optical element and the second bonding surface of the optical base. The optical element is bonded and fixed to the optical base through the first bonding surface and the second boding surface by means of the bonding agent.

An optical element according to one aspect of the present disclosure is bonded and fixed to an optical base by means of a bonding agent. The optical element includes a bonding surface. A groove in which the bonding agent flows is formed in the bonding surface of the optical element. The optical element and the optical base are bonded and fixed together by means of the bonding agent through the bonding surface.

DETAILED DESCRIPTION

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

FIG. 1is a side cross sectional view of a color laser printer as one embodiment of an image forming apparatus according to the present disclosure. The color laser printer shown inFIG. 1is of tandem type. In the central part of a main body100of the color laser printer, a magenta image forming unit1M, a cyan image forming unit1C, a yellow image forming unit1Y, and a black image forming unit1K are arranged at regular intervals in tandem.

A photoconductive drum2aas an image carrier is arranged in the magenta image forming unit1M. A charger3a, a developing unit4a, a transfer roller5a, and a cleaning unit6aare arranged around the photoconductive drum2a. A photoconductive drum2bas an image carrier is arranged in the cyan image forming unit1C. A charger3b, a developing unit4b, a transfer roller5b, and a cleaning unit6bare arranged around the photoconductive drum2b. A photoconductive drum2cas an image carrier is arranged in the yellow image forming unit1Y. A charger3c, a developing unit4c, a transfer roller5c, and a cleaning unit6care arranged around the photoconductive drum2c. A photoconductive drum2das an image carrier is arranged in the black image forming unit1K. A charger3d, a developing unit4d, a transfer roller5d, and a cleaning unit6dare arranged around the photoconductive drum2d.

Here, the photoconductive drums2a-2dare photoreceptors in dram shape and are driven and rotated at a predetermined processing speed in the directions (anticlockwise direction) indicated by the arrows inFIG. 1by a drive motor (not shown). Further, each charger3a-3delectrostatically charges the surface of the corresponding photoconductive drum2a-2duniformly to a predetermined potential with charged bias applied from a charged bias power supply (not shown).

Further, the developing units4a-4daccommodate magenta (M) toner, cyan (C) toner, yellow (Y) toner, and black (K) toner, respectively, and allow the respective toner in corresponding colors to adhere to electrostatic latent images formed on the respective photoconductive drums2a-2d, thereby visualizing the electrostatic latent images as toner images in the respective colors.

Furthermore, the primary transfer rollers5a-5dare arranged so as to be capable of being in direct contact with the photoconductive drums2a-2d, respectively, with an intermediate transfer belt7interposed. Hereinafter, respective contact portions between the photoconductive drums2a-2dand the primary transfer rollers5a-5dmay be referred to as primary transfer portions in the present specification. The intermediate transfer belt7is wound between a drive roller8and a tension roller9so as to be capable of running on the upper surfaces of the photoconductive drums2a-2d. The drive roller8is arranged so as to be capable of being in contact with a secondary transfer roller10with the intermediate transfer belt7interposed. Hereinafter, a contact portion between the drive roller8and the secondary transfer roller10may be referred to as a secondary transfer portion in the present specification. Further, an optical density sensor11is disposed in the vicinity of the drive roller8where the intermediate transfer belt7faces.

Moreover, four optical scanning devices12according to the present disclosure are arranged below the magenta image forming unit1M, the cyan image forming unit1C, the yellow image forming unit1Y, and the black image forming unit1K in the printer main body100so as to correspond to the magenta image forming unit1M, the cyan image forming unit1C, the yellow image forming unit1Y, and the black image forming unit1K, respectively. Further, a paper feed cassette13is detachably provided at the bottom of the printer main body100below the four optical scanning devices12. A plurality of sheets of paper (not shown in the drawings) are accommodated and stacked in the paper feed cassette13. A conveyance roller pair14is provided in the vicinity of the paper feed cassette13. The conveyance roller pair14picks up the paper from the paper feed cassette13and sends out it sheet by sheet to a conveyance path S. The conveyance path S is a path extending in the vertical direction along the side of the printer main body100.

In addition, a paper stop roller pair15is provided on the conveyance path S. The paper stop roller pair15makes the paper picked out from the paper feed cassette13to temporarily wait and then supplies it to the secondary transfer portion at predetermined timing.

Incidentally, the conveyance path S extends to an exit tray16provided on the upper surface of the printer main body100. A fusing unit17and a paper delivery roller pair18are provided in the middle of the path to the exit tray16.

Image forming operation by the color laser printer with the above configuration will be described next.

Upon issuance of an image formation start signal, the photoconductive drums2a-2dare driven and rotated at a predetermined processing speed in the directions (anticlockwise direction) indicated by the arrows inFIG. 1in the magenta image forming unit1M, the cyan image forming unit1C, the yellow image forming unit1Y, and the black image forming unit1K, respectively, and are charged by the respective chargers3a-3duniformly. Then, the optical scanning devices12each emit a light beam, which is modulated by a color image signal in corresponding color, to irradiate the surface of the corresponding photoconductive drum2a-2d, thereby forming electrostatic latent images according to the color image signals in respective colors on the respective photoconductive drums2a-2d.

Next, the developing unit4afirst allows the magenta toner to adhere to the electrostatic latent image formed on the photoconductive drum2aof the magenta image forming unit1M to visualize the electrostatic latent image as a magenta toner image. Developing bias having the same charge polarity as that of the photoconductive drum2ais applied to the developing unit4a. The magenta toner image is primarily transferred onto the intermediate transfer belt7, which is driven and rotated in the direction indicated by the arrows in the drawing, at the primary transfer portion (transfer nip) between the photoconductive drum2aand the transfer roller5aby the operation of the transfer roller5a. It is noted that the primary transfer bias having a polarity opposite to that of the toner is applied to the transfer roller5a.

The intermediate transfer belt7to which the magenta toner image is primarily transferred as described above moves the magenta toner image to the next cyan image forming unit1C. Then, also in the cyan image forming unit1C, the cyan toner image formed on the photoconductive drum2bis transferred in the same manner to be overlaid on the magenta toner image on the intermediate transfer belt7at the primary transfer portion between the photoconductive drum2band the transfer roller5b.

Likewise, the yellow toner image and the black toner image respectively formed on the photoconductive drum2cof the yellow image forming unit1Y and the photoconductive dram2dof the block image forming unit1K are sequentially overlaid on the magenta toner image and the cyan toner image, which are transferred and overlaid on the intermediate transfer belt7, at the respective primary transfer portions, thereby forming a full color toner image on the intermediate transfer belt7. It is noted that non-transferred remaining toner, which has not been transferred to the intermediate transfer belt7and remains on the photoconductive drum2a-2d, is removed by the respective cleaning units6a-6d, thereby preparing each photoconductive drum2a-2dfor the next image formation.

Thereafter, the paper stop roller pair15conveys the paper, which is sent out from the paper feed cassette13to the conveyance path S by the conveyance roller pair14, to the secondary transfer portion at the timing when the tip end of the full color toner image on the intermediate transfer belt7reaches the secondary transfer portion (transfer nip) between the drive roller8and the secondary transfer roller10. Then, the secondary transfer roller10secondarily transfers the full color toner image from the intermediate transfer belt7to the paper in batch. It is noted that secondary transfer bias having a polarity opposite to that of the toner is applied to the secondary transfer roller10.

Subsequently, the paper on which the full color toner image is transferred is conveyed to the fusing unit17, and the full color toner image is heated and pressurized to be thermally fused on the surface of the paper. The paper delivery roller pair18delivers the paper, on which the toner image is fused, onto the exit tray16, thereby completing a series of image forming operation.

Next, the basic configuration and operation of the optical scanning devices12according to the present disclosure will be described below with reference toFIG. 2. It is noted that the four optical scanning devices12have the same configuration, and therefore, only one optical scanning device12will be described below.

FIG. 2is a perspective view of an optical scanning device according to the present disclosure. The optical scanning device12includes an optical base19as a box body. A laser diode (LD)20as a light source is provided on a wall19astanding perpendicular to the bottom of the optical base19. Inside the optical base19, a collimator lens21, a cylindrical lens22, and a polygon mirror23as a deflector are disposed in a line along the direction where the laser diode20emits a light beam L.

Inside the optical base19, two fθ lenses of an fθ lens24and an fθ lens25and a steering mirror26are also disposed along the direction where the light beam L deflected by the polygon mirror23proceeds. In addition, a synchronization sensor27and a anterior-to-PD mirror28are disposed left and right, respectively, apart from an effective scanning range (actual scanning range used as a printing width) R of the light beam L between the fθ lens25and the steering mirror26. The anterior-to-PD mirror28reflects to lead the light beam L1to the synchronization sensor27. It is noted that the light beam L1is a light beam deflected by the polygon mirror23and proceeding in a light path deviated from the effective scanning range R.

Upon detection of the light beam L1, the synchronization sensor27outputs a synchronization signal. Any of various optical sensors may be employed as the synchronization sensor27, such as a photodiode, a phototransistor, a photo IC, etc.

Moreover, in the present embodiment, the anterior-to-PD mirror28is mounted so as to incline at a predetermined angle with respect to the horizontal plane (main scanning surface) to reflect the light beam L1, thereby allowing the light beam L1to enter into the synchronization sensor27in the sub scanning direction. By contrast, the light beam L deflected by the polygon mirror23and proceeding in the light path within the effective scanning range R proceeds horizontally in the steering mirror26, thereby performing exposure scan in the main scanning direction on the photoconductive drum2a(2b-2d).

The laser diode20of the optical scanning device12emits the light beam L modulated according to the image data. The collimator lens21makes the light beam L to be a parallel luminous flux. The parallel luminous flux is imaged on the reflection surface of the polygon mirror23by the cylindrical lens22, which has power only in the sub scanning direction, and is then deflected by the polygon mirror23, which is rotated at high speed. Next, the deflected light beam L is condensed by the fθ lens24and the fθ lens25at uniform speed, and is steered by the steering mirror26, thereby forming a focal spot on the photoconductive drum2aserving as a to-be-scanned surface. Subsequently, accompanied by formation of the focal spot, the photoconductive drum2ais subjected to exposure scan in the main scanning direction to form an electrostatic latent image according to the color image signal in the magenta color onto the photoconductive drum2a.

Further, when the anterior-to-PD mirror28reflects the light beam L1to allow the light beam L to enter into the synchronization sensor27in the sub scanning direction, the synchronization sensor27detects the light beam L1and outputs a synchronization signal. Then, according to the synchronization signal, start timing for exposure scan (writing) on the photoconductive drums2a-2dby the light beam L is determined.

Next, a fixing structure of the fθ lens24will be described below with reference toFIGS. 3 and 4.

FIG. 3is a cross sectional view showing the fixing structure of the fθ lens24.FIG. 4is an enlarged detailed view of the encircled part A inFIG. 3. The optical scanning device12according to one embodiment of the present disclosure includes an optical element (e.g., the fθ lens24) and the optical base19. Bosses (e.g., bosses24A) including bonding surfaces protrude from at least one of the optical element and the optical base19. Grooves (e.g., groves29) in which a bonding agent30is filled are formed in the bonding surfaces of the bosses. The optical element is bonded and fixed to the optical base19through the bonding surfaces of the bosses by means of the bonding agent30. The optical scanning device12according to one embodiment of the present disclosure will be described below in detail with reference toFIGS. 3 and 4.

As shown inFIG. 3, height positioning bosses19A are formed at two points of the optical base19(two points in the longitudinal direction of the fθ lens24(transverse direction inFIG. 3)) so as to protrude perpendicularly to the bottom of the optical base19and integrally with the optical base19.

On the other hand, two bosses24A are formed at two bonding points on the lower surface of the fθ lens24(two points corresponding to the height positioning bosses19A of the optical base19) so as to protrude perpendicularly downward and integrally with the fθ lens24. Each of the bosses24A has a flat bonding surface24a(first bonding surface) at the bottom thereof. The bonding surface24aof each boss24A is a surface in parallel to the boding surface (second bonding surface) of the optical base19.

As shown in detail inFIG. 4, a groove29is formed in the bonding surface24aof each boss24A. The groove29has a T-shape (dovetail groove shape) open at the bonding surface24a. The T-shape herein means a combination of an I-shape extending toward the depth of the boss24A and a rotated I-shape horizontally widened at the depth of the boss24A with a narrow opening at the bonding surface24a. For example, in the case where the boss24A protrudes perpendicularly downward from the fθ lens24, as shown inFIG. 4, the groove29is formed in an I-shape from the opening at the bonding surface24ato the depth of the boss24A and then in a rotated I-shape at the depth of the boss24A. Further, a bonding agent30flows in the groove29.

Then, the fθ lens24is positioned in the following manner and is then bonded and fixed to the optical base19.

Specifically, as shown inFIG. 3, the fθ lens24is placed on the two height positioning bosses19A of the optical base19. Then, the bonding surfaces24aof the two bosses24A are bonded to the corresponding two height positioning bosses19A of the optical base19by means of the bonding agent30entered in the grooves29. As a result, the two points in the longitudinal direction of the fθ lens24are fixed to the optical base19.

In this way, in the present embodiment, the bonding agent30is entered in the grooves29formed in the bosses24A of the fθ lens24to increase the bonding area of the fθ lens24. This can increase the bonding strength of the fθ lens24. Further, the bonding agent30entered in the grooves29is hardened to function to prevent the fθ lens24from falling off. Accordingly, even when the fθ lens24and the optical base19, which are different from each other in coefficient of linear expansion, are thermally expanded, coming off of the fθ lens24from the optical base19can be restrained with the above simple structure. Further, in the present embodiment, with the grooves29in T-shape (dovetail groove shape) when viewed in cross section in which the bonding agent30is entered, the bonding agent30, which is entered in the groves29and is hardened, can further enhance the effect of preventing the fθ lens24from falling off.

Here, another embodiment of the fixing structure of the fθ lens24is shown inFIG. 5.

Specifically,FIG. 5is a cross sectional view showing the other embodiment of the fixing structure of the fθ lens24. In this embodiment, each of the bosses24A of the fθ lens24has a bonding surface24b. The bonding surface24bof each boss24A inclines relative to the bonding surface of the optical base19. The bonding surface24bis an inclined surface reduced in width as it goes toward the T-shaped groove29. The “width” herein means the distance between a first inclined surface and a second inclined surface which incline toward the opening of the bonding surface24b. The bonding surface24bof each boss24A may be in a shape of, for example, a mortar or a gable roof.

Accordingly, in the present embodiment, the bonding surface24bof each boss24A of the fθ lens24is an inclined surface reduced in width as it goes toward the groove29. This means that the area of the bonding surface24bis larger than that of the bonding area24a. As such, the bonding area of the fθ lens24is further increased, and the bonding agent30can be easily entered each groove29along the bonding surface24b. Thus, the bonding strength can be further increased, and assemblability can be enhanced.

In addition, where the laser beam printer shownFIG. 1is provided with the optical scanning devices12according to the present embodiment, coming off of the fθ lens24of each optical scanning device12can be restrained, thereby stably forming desired images.

The embodiments of the present disclosure have been described with reference toFIGS. 1-5. It is noted that although the fixing structure of only one of the fθ lenses24has been described, the other optical elements, such as the other fθ lens25, the collimator lens21, the cylindrical lens22, etc. can be bonded and fixed to the optical base19with the same fixing structure. Further, the embodiments have been described in which the grooves29are formed in the bosses24A of the fθ lens24as an optical element, but formation of grooves similar to the grooves29in the height positioning bosses19A of the optical base19can obtain the same advantages as above.

In detail, where the grooves are formed in the bosses24A of the fθ lens24, the bosses24A of the fθ lens24have the bonding surfaces24ain parallel to the bonding surface of the optical base19or the bonding surfaces24binclined relative to the bonding surface of the optical base19. By contrast, in the case where the grooves are formed in the height positioning bosses19A, each of height positioning bosses19A has a bonding surface in parallel to the bonding surface of the corresponding optical element or a bonding surface inclined relative to the bonding surface of the corresponding optical element.

It is noted that besides the cases with the grooves formed only in bosses (e.g., the bosses24A) of an optical element (e.g., the fθ lens24) and with the grooves formed only in the bosses19A of the optical base19, the grooves can be formed in both the bosses of the optical element and the bosses19A of the optical base19. In the case where the grooves are formed in both the bosses of the optical element and the bosses19A of the optical base19, the bonding area is large compared to the case where the grooves are formed in only one of them. Accordingly, the optical element can be further firmly bonded to the optical base19. As a result, coming off of the optical element from the optical base19can be restrained.

In addition, both of the bosses of an optical element and the bosses19A of the optical base19protrude in the embodiments of the present disclosure. However, as long as a boss protrudes from at least one of the optical element and the optical base19, the scope of the present disclosure is not limited to protrusion from both of them. For instance, an example in which only a boss protrudes only from an optical element, while no boss is provided at the optical base19is also within the scope of the present disclosure. Alternatively, an example in which only a boss protrudes only from the optical base19, while no boss are provided at an optical element is also within the scope of the present disclosure.

Still, both the bosses of the optical element and the bosses19A of the optical base19protrude in the embodiments of the present disclosure. However, the scope of the present disclosure is not limited to protrusion of the bosses of the optical element and the bosses19A of the optical base19. As long as a groove29in which the bonding agent30flows is formed in at least one of the first bonding surface of the optical element and the second bonding surface of the optical base19, the bosses are not necessarily to protrude from at least one of the optical element and the optical base19. An example in which the groove29in which the bonding agent30flows is formed in at least one of the first bonding surface of the optical element and the second bonding surface of the optical base19so that the optical element and the optical base19are bonded and fixed together by means of the bonding agent30through the first bonding surface and the second bonding surface is also within the scope of the present disclosure, free from the limitation that the bosses protrude from at least one of the optical element and the optical base19.

Description has been made about the embodiments that apply the present disclosure to the color laser printer and the optical scanning devices12included therein. However, the present disclosure is, of course, applicable likewise to any other image forming apparatuses including monochrome printers, copiers, etc. and optical scanning devices included therein. In the case where any image forming apparatus includes the optical scanning devices according to any of the above embodiments, coming off of the optical elements included in the optical scanning devices from the optical base can be restrained, thereby stably forming desired images.

Furthermore, the number of the grooves formed in the bonding surface of each boss is not limited to one. As long as the bonding area between an optical element and the optical base can be increased, the number of the grooves formed in the bonding surface of each boss may be plural.