JP3424985B2 - Scanning optical device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning optical device,
More specifically, the present invention relates to the structure of a writing start position detection unit of an image forming apparatus that writes an image with a light beam in a scanning optical device.

[0002]

2. Description of the Related Art Conventionally, a scanning optical apparatus applied to an electrophotographic image forming apparatus such as a laser printer, a copying machine, a facsimile apparatus or the like has an upper surface open as disclosed in Japanese Utility Model Laid-Open No. 19194/1993. In a box-shaped housing case, a rotary polygonal mirror having a hexagonal shape in plan view as a deflector that is rotated by a motor attached to the bottom surface thereof and a lens group as a scanning optical system such as an fθ lens are fixedly provided. A laser unit including a semiconductor laser element as a light source and a collimating lens is attached to one side wall surface of the housing case, and a light beam emitted from the laser unit is modulated in accordance with image data and is rotated by a rotating polygon mirror. The light beam that has been irradiated onto the laser beam and is reflected here has its path changed by a mirror provided in the housing case through a lens group such as an fθ lens. The surface of the rotating photosensitive drum is scanned from the mirror through a window hole formed on one side of the housing case so as to be parallel to the rotation axis of the photosensitive drum, and light is condensed (imaged). Are known.

In the scanning optical device, a writing position detecting mirror, a slit body, and an optical fiber as a writing position detecting portion are provided in the housing case, and a laser unit emits light when detecting the writing position. After being reflected by the writing position detection mirror through the light beam lens group, the light beam passes through a slit, which is a narrow gap in the slit body, and enters the optical fiber, and is arranged at the other end of the optical fiber. The photo sensor is used to obtain the write start position detection signal.

In the above scanning optical device, in order to adjust the timing of detecting the write start position, the slit body is
Move it in parallel with the light blocking wall. In other words, the slit body is moved in the direction orthogonal to the incident optical axis of the slit portion.

[0005]

However, when the slit body is moved in the direction orthogonal to the incident optical axis with respect to the slit portion as described above, the size of the housing case must be increased so as to allow the movement. However, there is a problem that the housing case becomes large.

Further, in adjusting the parallel movement of the slit body, it is necessary to devise a guide groove in parallel with the moving direction of the slit body, and there is a problem that the fine adjustment work is extremely difficult. The present invention has been made to solve these technical problems, and an object of the present invention is to provide a compact scanning optical device in which the writing position adjustment is easy and compact.

[0007]

In order to achieve the above object, a scanning optical apparatus according to the invention of claim 1 irradiates an image forming surface by deflecting a light beam emitted from a light source through a deflector. Horizontal scanning is performed, the light beam incident on the scanning start end is reflected by the mirror, and is incident on the writing position signal detection sensor through the slit in the slit body to obtain the horizontal scanning synchronization signal. A scanning optical device, which is rotatably mounted so as to adjust the position of the slit body disposed between the mirror and the writing position detection sensor in a direction in which the slit intersects the incident optical axis of the light beam. It was done.

According to a second aspect of the present invention, in the scanning optical device according to the first aspect, the deflector, the slit body, and the write start position signal detection sensor are mounted in the housing case, and the rotation center position of the slit body is set. Is located near the incident optical axis of the light beam. According to a third aspect of the present invention, in the scanning optical device according to the second aspect, the inner surface of the peripheral side wall of the housing case is in a direction in which one light shielding wall of the slit body is appropriately inclined with respect to the incident optical axis. On the inner surface of the peripheral side wall, a ridge for shielding incident light passing between the peripheral side wall and the light shielding wall of the slit body is provided.

[0009]

EXAMPLES Next, examples embodying the present invention will be described. FIG. 1 is a schematic sectional side view of a laser beam printer 1 as an image forming apparatus, FIG. 2 is a sectional side view of a scanning optical device, and FIG. 3 is a bottom view showing an arrangement relationship of components inside a housing case 30. A paper feed cassette 3 as a paper feed unit is detachably mounted on one side of the main body case 2 of the printer 1 of this embodiment, and is stacked in the paper feed cassette 3 by a paper feed roller 4 and a separation pad 5. Sheets P as recording media are separated one by one and sent to the image forming unit 9 via the pair of feeding rollers 6.

The image forming unit 9 includes a rotating photosensitive drum 7 as a photosensitive member and a transfer roller 8 as a transfer means.
In the case, a developing device unit 12 including a toner cartridge 10 and a developing roller 11 located near the paper feed cassette 3 side, a charging device 13 on the lower surface side of the photosensitive drum 7, a cleaning device 14 and the like are included in a kit. Stored in a single unit.

A fixing device 17 including a pressing roller 15 and a heating roller 16 is arranged on the discharge side of the image forming unit 9. Below the image forming unit 9, a downward open box-shaped housing case 30 in the scanner unit 18 as a scanning optical device for scanning the laser beam toward the lower surface of the photosensitive drum 7 is provided.
0a on the upper side of the flat plate portion 2b of the main frame 2a in the main body case 2 and the sealing material 42 such as a sponge material.
And the top plate 30a of the housing case 30 that is mounted via the
The main frame 2a is detachably attached to both left and right sides through tie bars 40 and 41 attached to the upper surface.

A laser emitted from a scanner unit 18, which will be described later, according to image data transmitted from an external device such as a host computer (not shown) on the surface of the photosensitive drum 7 which has been precharged by the charging device 13. An electrostatic latent image is formed on the surface (image forming surface) of the photoconductor drum 7 by forming an image of light, and then the developing roller 11 is rotated to supply the charged powdery toner to the latent image. After the development for converting the toner image into a visible image is performed, the toner image is transferred onto the sheet P supplied to the transfer portion between the photosensitive drum 7 and the transfer roller 8, and then the heating in the fixing device 17 is performed. After passing between the roller 16 and the pressing roller 15, heat and pressure are applied to the transferred toner image to fix the toner image on the paper P. After that, the paper is discharged to the paper discharge tray 63 via the paper discharge roller pair 62.

A control board 60 and a high-voltage board 61 for applying a high voltage to the charging device 13 and the transfer roller 8 are arranged below the main frame 2a. Next, regarding the configuration of the scanner unit 18, FIG.
~ Will be described with reference to FIG. Figure 3 is III-II of Figure 2.
FIG. 1 is a view from the direction of arrow I, which is a downward open box type and is a bottom view of the inside of a housing case 30 made of glass reinforced plastic in which short glass fibers are mixed.

In the scanner unit 18, the laser emitting unit 20 and the rotary polygon mirror 27, f as a deflector.
A component including a θ lens 21, a cylindrical lens 22, a folding mirror 23, a writing position signal (BD) mirror 25, a slit body 35, a condenser lens 36, a writing position signal detection (BD) sensor 26 such as a light receiving element, etc. , The top plate 3 in the downward open box type housing case 30.
It is configured to be fixed to the inner surface (lower surface) of 0a.

A laser light emitting unit 20 in which a semiconductor laser as a light source and a collimating lens (both not shown) are built in a block body 28 is arranged on one side far from the photosensitive drum 7 and on the top plate 30a. It is fixed to the bottom surface with screws. A printed wiring board 29 is provided on the back surface of the block body 28.
Is installed. A rotary polygon mirror 27 such as a six-sided mirror that rotates in the direction of arrow A in FIG. 4 by a drive motor 31 fixed to the inner surface of the top plate 30a is incident from the laser emitting unit 20 toward this mirror surface. The optical axis of the light beam is arranged so as to be substantially parallel to the rotation axis of the photosensitive drum 7. The light beam L reflected by the mirror surface of the rotary polygon mirror 27 has a mounting member 32 made of a leaf spring at both ends.
After passing through the fθ lens 21 and the cylindrical lens 22 fixed to the top plate 30a via a, 32b, 33a, and 33b, the light is reflected by the folding mirror 23 toward the lower surface of the photosensitive drum 7. The top plate 30a of the housing case 30 is provided with a long window hole 34 in a portion near the lower surface of the photosensitive drum 7 in parallel with the axis of the photosensitive drum 7, and a glass plate covering the window hole 34. The deflected light beam L is scanned on the lower surface of the photoconductor drum 7 along the axial direction of the photoconductor drum 7 through the light-transmitting cover plate 24.

In the fθ lens 21, the distance from the optical axis of the lens 21 to the image spot on the surface of the photosensitive drum 7 is the principal ray reflected by the reflecting surface of the rotary polygon mirror 27 which is a deflector. Deflection angle θ formed by the optical axis of fθ lens 21
It has the characteristic of being proportional to. As shown in FIGS. 3 and 4, a writing position signal mirror (BD (Beam Detector) mirror) fixed by a leaf spring (not shown) in the vicinity of one end in the longitudinal direction of the folding mirror 23. ) 25 are arranged. The optical path from the rotary polygon mirror 27 to the writing position signal mirror 25 and the slit body 35, the condenser lens 36, and the writing position signal detection sensor 26, which are reflected by the writing position signal mirror 25 and will be described later. It is separated from the optical path that reaches it by a partition wall 43, and only the light beam L reflected by the writing position signal mirror 25 is directed to the slit body 35, and the rotary polygon mirror 27.
The light beam L from is diffusely reflected by the peripheral side wall 30b and the inner surface of the partition wall 43, and is then shielded so as not to enter the slit body 35, the condenser lens 36, and the writing position signal detection sensor 26.

In the illustrated embodiment, the partition wall 43 is arranged substantially parallel to one side wall (right side in FIGS. 3 and 4) of the housing case 30. Further, the slit body 35 made of synthetic resin, as shown in FIGS.
Both left and right light shielding walls 35 extending in a direction substantially perpendicular to the inner surface of the top plate 30a of the housing case 30 and having a substantially L-shaped cross section.
a, 35b, a narrow slit 44 formed between the left and right light-shielding walls 35a, 35b and extending in a direction substantially perpendicular to the inner surface of the top plate 30a, and the left and right light-shielding walls 35a, 35b.
A substrate 35c that is provided continuously with 35b and extends along the inner surface of the top plate 30a;
To adjust the position of the slit 44, the slit body 35 is attached to the top plate 3.
It has a boss 35d which is a center position for rotating with respect to the mounting recess 45 on the inner surface of 0a.

Then, after the light beam L reflected by the writing position signal mirror 25 is incident on the slit 44, the attitude of the slit body 35 is adjusted so as to enter the writing position signal detection sensor 26 via the condenser lens 36. to do so,
A rotating jig (not shown) is pressed against the upper surface of the slit body 35 to rotate the slit body 35 with the boss 35d fitted in the mounting recess 45. At this time, the line connecting the slit 44 and the substantially center of the boss 35d is set to be substantially coincident with the incident optical axis line from the writing position signal mirror 25, or to be displaced in a substantially parallel manner by a minute distance. .
The position of the slit 44 may be located downstream of the incident light with respect to the position of the boss 35d.
Further, the incident light from the writing position signal mirror 25 is set to form an image at the slits 44.

With this structure, the position of the slit 44 is orthogonal to the incident optical axis line by adjusting the rotation angle smaller than moving the slit body 35 in the direction orthogonal to the incident optical axis line. It can be adjusted so as to move in a wide range in the direction, and the defocusing phenomenon of image formation at the slit 44 is reduced. in this way,
After rotating and adjusting the position of the slit body 35, an adhesive is used to adjust the position of the boss 35d of the slit body 36 and / or the substrate 37.
Is fixed to the inner surface of the top plate 30a.

The slit body 3 whose position is adjusted as described above
5, the surfaces of the left and right light shielding walls 35a and 35b are
As shown in FIGS. 4 and 5, they are arranged so as to be inclined at an appropriate angle with respect to the incident optical axis of the light beam L. With this configuration, a writing start position signal (BD signal) for detecting the writing start position of the light beam L emitted from the laser emitting unit 20 in the horizontal direction of the photoconductor drum 7 is sent to the rotary polygon mirror 27. , Fθ
The rotary polygon mirror 27 rotates in the direction of arrow A in FIG. 4 when inputting to the write position signal detection sensor 26 via the path of the lens 21, the cylindrical lens 22, the write position signal mirror 25, the slit body 35, and the condenser lens 36. As the light beam L is reflected by the writing position signal mirror 25, the partition wall 43 from the side closer to the peripheral side wall 30b in FIG.
Scan by angle θ1 in the direction. And the light beam L
At the moment when the light enters into the edge of the slit 44 and a predetermined or more light energy is incident on the write position signal detection sensor 26, the write position signal detection is performed.

As in this embodiment, the surfaces of the left and right light shielding walls 35a and 35b sandwiching the slit 44 are indicated by arrows B in FIG.
If the light beam L which is scanned in the direction is not orthogonal to the incident optical axis of the light beam L but is tilted by an appropriate angle, the light beam L reflected by the surfaces of the left and right light shielding walls 35a and 35b is directly written out. It does not return to the signal mirror 25 and is not reflected again by the mirror 25. Therefore, the light beam L is reflected by the surface orthogonal to the incident optical axis as in the conventional technique, and the writing position signal mirror 25 is directly transmitted.
There is no phenomenon that an unnecessary ghost image is generated in the image forming area on the surface of the photosensitive drum 7 (image forming surface) after returning to the rotary polygon mirror 27 from.

Incidentally, the left and right light-shielding walls 35a, 35b.
The light beam L reflected by the surface of the
Even after returning to the writing position signal mirror 25 after repeating the diffused reflection on the inner surface of 0b, the light energy is greatly attenuated (a few tenths to a few tenths). The optical energy necessary for forming an electrostatic latent image on the surface does not remain, and the ghost image as described above is not generated.

Further, the slit 44 is formed in the light shielding wall 35a or 35b which is inclined by an appropriate angle with respect to the incident optical axis of the light beam L scanned in the direction of arrow B in FIG.
By piercing, the incident light strikes the edge corner of the slit 44, and the rising edge of the light beam L (signal) incident on the writing position signal detection sensor 26 becomes sharp,
An accurate and stable detection signal can be obtained.

Further, as shown in FIG. 5, the slit body 3
On the inner surface of the peripheral side wall 30b in the vicinity of which 5 is arranged, there is provided a ridge 46 projecting so as to approach one of the light shielding walls 35b of the slit body 35 and parallel to the extending direction of the slit 44. As a result, of the light beam L traveling from the writing position signal mirror 25 toward the slit body 35, the light beam L approaching the inner surface of the peripheral side wall 30b.
However, even if it enters the light blocking wall 35b of the slit body 35 without being disturbed, it is disturbed at the location of the ridge 46, so that it directly enters the condenser lens 36 and is erroneously detected as a write start position signal. Never.

A laser drive board (printed wiring board) for processing the horizontal synchronizing signal input to the write position signal detection sensor 26 to drive the laser emitting unit 20.
37 is abutted on the end surface of a rib protruding downward from the inner surface of the top plate 30a, and is fixed by a screw 38. In this case, as shown in FIG. 3, FIG. 7 and FIG.
Is a position between the writing position signal mirror 25 and the writing position signal detection sensor 26, and is loosened in a pair of mounting grooves 47a, 47b formed between the peripheral side wall 30b and the inner surface of the partition wall 43 and having a substantially U shape in a plan view. The printed wiring board 37 is prevented from falling off by inserting the printed wiring board 37 without any sticking. Also, the printed wiring board 37 may be formed by soldering the feet of the writing position signal detection sensor 26 or the like.
By directly fixing to the writing position signal detecting sensor 26, the mounting work can be extremely simplified as compared with the mounting of the writing position signal detection sensor 26 alone.

As another embodiment, the housing case 30
It goes without saying that the laser light emitting unit 20 and the write start position signal detection sensor 26 may be fixed to one outer side of the peripheral side wall. Further, it goes without saying that the present invention can also be applied to a scanning optical device in an electrophotographic image forming apparatus such as a facsimile or a copying machine, and other optical devices used for image processing and the like.

[0027]

As described above, claim 1
The scanning optical device of the invention described above deflects a light beam emitted from a light source through a deflector to irradiate an image forming surface to perform horizontal scanning, and a light beam incident on a scanning start end thereof is reflected by a mirror. In a scanning optical device configured to reflect and enter a writing position signal detection sensor through a slit in a slit body to obtain a horizontal scanning synchronization signal, the scanning optical device is arranged between the mirror and the writing position detection sensor. The slit body is rotatably mounted so as to adjust the position of the slit body in a direction intersecting the incident optical axis of the light beam.

Therefore, the position can be adjusted just by rotating the slit body about the rotation center, and the adjustment work becomes extremely easy. In addition, since the slit body is rotated around the rotation center away from the slit position instead of moving the entire slit body in parallel, the space for allowing the movement of the slit body is small, and the housing for installing the slit body is small. It also has the effect of making the case compact.

According to a second aspect of the present invention, in the scanning optical device according to the first aspect, the deflector, the slit body, and the writing start position signal detection sensor are mounted in a housing case, and the rotation center position of the slit body is set to the above. It is located near the incident optical axis of the light beam. According to this structure, even when the position of the slit in the slit body moves in a direction substantially orthogonal to the incident optical axis, there is an error that the position of the slit is displaced in the upstream side or the downstream side of the incident light. It is possible to prevent the diffusion phenomenon of the incident light with respect to the writing start position detection sensor and to obtain a stable writing start position signal.

According to a third aspect of the present invention, in the scanning optical device according to the second aspect, one of the slit walls of the slit body is appropriately inclined with respect to the incident optical axis and is a peripheral side wall of the housing case. On the inner surface of the peripheral side wall, a ridge is provided on the inner surface of the peripheral side wall for shielding incident light passing between the peripheral side wall and the light shielding wall of the slit body.

Therefore, the light beam reflected by the surface of the light shielding wall in the slit body inclined by an appropriate angle with respect to the incident optical axis of the light beam is not directly reflected again by the writing position signal mirror. Therefore, after the light beam is reflected by the surface orthogonal to the incident optical axis as in the conventional technique and directly returns from the mirror for the write start position signal to the deflector, the light beam does not reach the image forming area of the image forming surface. Since the phenomenon of generating a necessary ghost image does not occur, it is possible to obtain an effect that an image of good quality can be obtained.

Further, even if incident light from the writing position signal mirror passes between the peripheral side wall and the light shielding wall of the slit body, it is blocked at the ridge portion.
There is also an effect that light does not enter the writing position signal detection sensor at an incorrect timing, and it is possible to reliably prevent generation of an erroneous signal.

[Brief description of drawings]

FIG. 1 is a schematic side sectional view of a laser printer.

FIG. 2 is a side sectional view of a scanning optical device.

FIG. 3 is a view taken along the line III-III in FIG.

FIG. 4 is a plan sectional view of an essential part.

5 is an enlarged cross-sectional view of the main parts of FIG.

6 is a sectional view taken along the line VI-VI of FIG.

FIG. 7 is an enlarged plan view of an arrangement portion of a condenser lens and a writing start position signal detection sensor.

8 is a sectional view taken along the line VIII-VIII of FIG.

[Explanation of symbols]

1 printer 18 Scanner unit 20 Laser emission unit 21 fθ lens 23 Folding mirror 24 cover plate 25 Mirror for writing position signal 26 Writing position signal detection sensor 27 rotating polygon mirror 30 housing case 30b Surrounding side wall 35 slit body 35a, 35b left and right light shielding walls 35d boss 36 Condensing lens 43 partitions 44 slits 45 mounting recess 46 ridges

Claims (3)

(57) [Claims] 1. A light beam emitted from a light source is deflected by a deflector to irradiate an image forming surface to perform horizontal scanning, and a light beam incident on a scanning start end is reflected by a mirror to form a slit. In a scanning optical device configured to enter a writing position signal detection sensor through a slit in the body to obtain a horizontal scanning synchronization signal, the slit body arranged between the mirror and the writing position detection sensor, A scanning optical device, wherein the slit is rotatably mounted to adjust a position in a direction intersecting with an incident optical axis of a light beam. 2. A deflector, a slit body, and a writing position signal detection sensor are mounted in a housing case, and a rotation center position of the slit body is located near an incident optical axis of the light beam. The scanning optical device according to claim 1. 3. One of the light shielding walls of the slit body extends in a direction inclined with respect to the incident optical axis line so as to be close to the inner surface of the peripheral side wall of the housing case, and on the inner surface of the peripheral side wall. 3. The scanning optical device according to claim 2, wherein the scanning optical device has a ridge for blocking incident light passing between the peripheral side wall and the light shielding wall of the slit body.