JP4622489B2 - Optical scanning device - Google Patents

Description

  The present invention relates to an optical scanning device.

  In recent years, with the increase in speed and resolution of an image recording apparatus, the motor that drives the polygon mirror is also rotated at a high speed. The fundamental frequency of the motor increases due to the high speed rotation of the motor. When the fundamental frequency of the motor approximates the resonance frequency of the housing, the motor enters a resonance state. As a result, the housing vibrates violently, resulting in uneven pitch in the image.

  Further, if the fundamental frequency of the motor exceeds the resonance frequency of the housing, the housing resonates when the motor starts up or stops, and a large noise is generated.

  Further, the housing formed of a resin material is easily transmitted with vibrations caused by the rotation of the motor. As a result, troubles such as image quality deterioration tend to occur. Therefore, if the thickness of the housing is increased in order to give the housing sufficient rigidity, a large amount of resin material is required to mold the housing, leading to an increase in cost. In this case, the weight of the housing increases, which leads to an increase in the weight of the entire image forming apparatus.

  In order to solve this problem, measures have been taken to reinforce the periphery of the motor, which is a vibration source, with ribs (see Patent Document 1) (see Patent Document 1). . However, in any case, the rib is high enough to avoid the light beam passage region, and the rigidity of the housing cannot be sufficiently increased.

As shown in FIG. 11, another optical scanning device 100 includes a rib 110 that connects the side wall of the housing 108. The height of the rib 110 is not less than the light beam passage height, but the light beam passage region is cut out in a U shape to secure the light beam transmission region. Stiffness will decrease.
JP 9-33844 A JP 2003-185960 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide an optical scanning device that can prevent the occurrence of image defects by constituting a rib that can ensure the rigidity of a housing and reducing the occurrence of noise and vibration when a polygon mirror is driven. .

The present invention according to claim 1 is a polygon mirror that deflects and scans a light beam emitted from a light source, an imaging lens that forms an image on the exposure surface of the light beam deflected and scanned by the polygon mirror, and the polygon An optical scanning device comprising: an optical box in which a mirror and the imaging lens are housed and reinforced by a rib standing from the bottom; and a transmissive optical element through which the light beam is transmitted. The rib is provided between the image forming lens, an opening through which the light beam can pass is formed, and a first surface is formed on the bottom surface of the optical box on the image forming lens side of the rib. A base plate in which a screw hole is formed and a second screw hole is formed; a wall portion standing on both ends of the base plate and closing both ends of the opening; and the transmission type provided between the wall portions stage that holds the optical element And parts, the holding member having a first threaded hole and removably attached to the opening by inserting fastening screws into the second screw hole, said transmission optical element and the opening in the holding member part is closed, and the rib, the circumferential rib extending in a direction perpendicular to the ribs, the space formed by the side wall of the optical box surrounding the polygon mirror, and characterized in that it is closed by the lid.

  According to the first aspect of the present invention, the rib is erected from the bottom surface of the optical box between the polygon mirror and the imaging lens so that the light beam passes through the opening formed in the rib. It has become. For this reason, a rib can be made higher than the passage area of a light beam, and the rigidity of an optical box can be raised. Further, compared to the case where the rib is cut out to allow the light beam to pass therethrough, the rib is partially continuous in the opening, so that the rigidity of the rib is maintained. As a result, it is possible to increase the rigidity of the optical box while securing a light beam passage region.

Therefore, since it is not necessary to increase the thickness of the optical box or increase the number of ribs, the resin material necessary for forming the optical box can be reduced. Further, since the resonance frequency of the optical box is increased by increasing the rigidity of the optical box, the optical box is less likely to resonate even when the polygon mirror is rotated at a high speed, thereby preventing image pitch unevenness and the like. Furthermore, the rib provided between the polygon mirror and the imaging lens can separate the inside of the optical box into a region where the polygon mirror is provided and a region where the imaging lens is provided. Thereby, it is possible to suppress the vibration generated when the polygon mirror is driven from being conducted to the region where the imaging lens is provided as much as possible.

Further, the opening is closed by attaching a transmissive optical element to the opening formed in the rib. Thereby, it is possible to prevent dust, dust, and the like from entering the region where the polygon mirror is installed. In addition, when the transmissive optical element is attached to the direct opening formed on the rib, the attachment part to which the transmissive optical element is attached is damaged or the transmissive optical element needs to be replaced. The need to replace the entire optical box arises. Therefore, the transmission optical element is held by the holding member, and the holding member is attached to the opening, and the opening is closed with the transmission optical element. As a result, when the mounting portion to which the transmissive optical element is attached is damaged or when it is necessary to replace the transmissive optical element, the holding member can be removed from the opening and replaced. There is no need to replace the box.

Further, by covering the space formed by the ribs and the side walls with the lid, the region where the polygon mirror is provided is closed in the optical box. That is, the polygon mirror is isolated. Thereby, noise generated when the polygon mirror is driven can be reduced. Furthermore, dust and dust can be prevented from entering the area where the polygon mirror is provided.

  The present invention according to claim 2 is characterized in that the rib is formed integrally with the optical box continuously between the side walls of the optical box.

  According to the second aspect of the present invention, the ribs are integrally formed with the optical box, so that the number of parts is not increased and the assembly process of the optical scanning device is not complicated. Further, by forming the ribs continuously between the side walls of the optical box, the rigidity of the optical box can be increased as compared with the first aspect.

  The present invention according to claim 3 is characterized in that the opening is opened to the bottom surface leaving the top of the rib.

  According to the third aspect of the present invention, the opening portion is opened to the bottom plate portion of the optical box, leaving the top of the rib, thereby ensuring a large area of the opening portion while maintaining the rigidity of the optical box. it can.

The present invention according to claim 4 is characterized in that the circumferential rib and the height of the rib are the same.

According to the invention described in claim 4 , the rigidity of the periphery of the polygon mirror can be increased by making the height of the rib the same as the height of the peripheral rib and the side wall extending in the direction orthogonal to the rib. Thereby, it is possible to suppress the vibration generated when the polygon mirror is driven from being transmitted outside the region where the polygon mirror is disposed.

  Since the present invention has the above-described configuration, the present invention provides an optical scanning device that can prevent the occurrence of image defects by configuring ribs that can ensure the rigidity of the housing and reducing the occurrence of noise and vibration when the polygon mirror is driven. be able to.

  A first embodiment of the present invention will be described below with reference to the drawings.

  As shown in FIG. 1, the optical scanning device 10 has a substantially box-shaped housing 42. The housing 42 includes a bottom surface 42A and a side wall 42B that stands up from the outer periphery of the bottom surface 42A. A semiconductor laser substrate 11 that emits a light beam L toward the inside of the housing 42 is disposed outside the side wall 42B.

  As shown in FIG. 2, the semiconductor laser substrate 11 is provided with a semiconductor laser that emits a light beam L (hereinafter referred to as “LD”), and is on the optical path of the light beam L emitted from the LD 12. A collimator lens 13 and a slit 14 are provided.

  The light beam L emitted from the LD 12 is passed through the slit 14 by the collimator lens 13 so that the light beam having a substantially normal distribution emitted from the LD 12 is not a substantially parallel light beam but a light beam L of loosely diverging light. Is shaped into a light beam L having a rectangular cross section consisting only of light near the optical axis.

  On the optical path of the light beam L that has passed through the slit 14, a cylinder lens 17, an optical system 18 that is an expansion optical system, plane mirrors 15 and 16, filters 21, fθ lenses 22 and 24, and a polygon mirror 20 are provided. ing. The light beam L passes through the cylinder lens 17 and the optical system 18 and is reflected by the plane mirror 15. Then, the light passes through the filter 21, is reflected by the plane mirror 16, passes through the fθ lenses 22 and 24, and is guided to the polygon mirror 20.

  The fθ lenses 22 and 24 are arranged so that both the light beam L incident on the polygon mirror 20 from the front by the plane mirror 16 and the light beam L reflected and deflected by the polygon mirror 20 are incident. That is, the light beam passes through the fθ lenses 22 and 24 twice before and after the reflection deflection by the polygon mirror 20, and this optical system forms a so-called front incidence / double pass optical system as a whole. . As a result, in the present optical system, a wide scanning width is ensured while keeping the amount of light in the main scanning direction uniform to some extent.

  The light beam L reflected by the polygon mirror 20 and passed through the fθ lenses 24 and 22 is reflected by the plane mirrors 26 and 31 and the cylinder mirror 28, and is emitted from the transmission window 30 toward the photosensitive drum 40 as a scanning line. Scanning exposure is performed by moving the surface of the photosensitive drum 40 at a constant speed.

  Further, in order to detect the scanning start position by the polygon mirror 20, the SOS (scanning start position) mirror 36 that reflects the light beam L reflected at the end portion in the longitudinal direction of the plane mirror 26, and the light beam from the SOS mirror 36. An SOS sensor 32 that receives light and emits a synchronization detection signal, and an SOS lens 34 that is disposed in the optical path between the SOS mirror 36 and the SOS sensor 32 and converges the light beam L on the SOS sensor 32 are provided. The light beam L reflected at the longitudinal end of the flat mirror 26 is reflected by the SOS mirror 36 and converged in the sub-scanning direction by the SOS lens 34. The SOS sensor 32 is connected to a control unit that modulates the output of the LD 12 and plays a role as a synchronous detector. When the light beam L is incident on the SOS sensor 32, a signal to that effect is transmitted to the control unit. The control unit modulates the output of the LD 12. The modulated light beam L is reflected by the cylinder mirror 28, is emitted from the transmission window 30, reaches the surface of the photosensitive drum 40, and image recording is started.

  The upper opening of the housing 42 (see FIG. 1) is configured to be closed by a lid member (not shown).

  As shown in FIG. 3, the motor 38 that rotationally drives the polygon mirror 20 is provided on the motor substrate 39. The motor substrate 39 is surrounded by a step 48 formed on the rib 44, the ribs 46 and 50, and the side wall 42B. The ribs 44 are continuously provided between the bottom surface 42A of the housing 42 and the side wall 42B of the housing 42 (see FIG. 1). Further, the rib 46 and the rib 50 are erected from the bottom surface 42 </ b> A of the housing 42 so as to be orthogonal to the rib 44. Further, the step 48 is cut down by one step from the side wall 42 </ b> B of the housing 42 and has the same height as the ribs 44, 46, and 50.

  The heights of the ribs 44, 46, 50 and the step 48 are made higher than those of the polygon mirror 20 mounted on the motor 38. The motor substrate 39, the motor 38, and the polygon mirror 20 have the ribs 44, 46, 50, and the step. 48 is surrounded by the four sides.

  A substantially rectangular opening 52 is formed at a substantially central portion of the rib 44 formed between the polygon mirror 20 and the fθ lens 22. The opening 52 is surrounded by a continuous upper frame portion 44A and lower frame portion 44B, and allows the light beam L (see FIG. 2) to pass therethrough.

  The light beam L passing through the fθ lens 22 toward the polygon mirror 20 and the light beam L deflected by the polygon mirror 20 and incident on the fθ lens 22 pass through the opening 52.

  The opening 52 is undercut with respect to the mold for molding the bottom surface 42 </ b> A of the housing 42 and the rib 44. Therefore, in order to form the opening 52, a mold for forming the bottom surface 42A of the housing 42 and the rib 44 has a slide structure. The opening 52 is formed by sliding the slide core in a direction orthogonal to the opening and closing direction of the mold by opening and closing the mold.

  As shown in FIG. 4A, the fθ lens 24 is attached to the elevation surface of the opening 52 on the polygon mirror 20 side. As shown in FIG. 4B, a step 54 is formed in the lower frame portion 44B of the opening 52, and the fθ lens 24 is placed on the step 54 to close the opening 52. At this time, both end surfaces of the fθ lens 24 are fixed to the corners 44C of the ribs 44 with an adhesive.

  In the present embodiment, the fθ lens 24 is attached to the polygon mirror 20 side of the opening 52, but may be attached to the fθ lens 22 side.

  In this embodiment, the opening 52 is closed by the fθ lens 24. However, as a member for closing the opening 52, a transmission optical element such as optical glass can be used in addition to the fθ lens 24. .

  Next, the operation of the first embodiment of the present invention will be described.

  As shown in FIG. 3, a rib 44 is erected from the bottom surface of the housing 42 between the polygon mirror 20 and the fθ lens 22 so that the light beam L passes through the opening 52 formed in the rib 44. It has become. For this reason, the rib 44 can be made higher than the passage region of the light beam L, and the rigidity of the housing 42 can be increased. In addition, the opening 52 is surrounded by the continuous upper frame portion 44A and lower frame portion 44B as compared with the case where the rib is cut out to allow the light beam L to pass therethrough, so that the rigidity of the rib 44 is maintained. It is. As a result, it is possible to increase the rigidity of the housing 42 while securing the passage region of the light beam L.

  Therefore, since it is not necessary to increase the thickness of the housing 42 or increase the number of ribs, the resin material necessary for forming the housing 42 can be reduced.

  Further, since the resonance frequency of the housing 42 is increased by increasing the rigidity of the housing 42, the housing 42 is less likely to resonate even when the polygon mirror 20 is rotated at a high speed, and the occurrence of uneven pitch of the image can be prevented.

  Furthermore, the inside of the housing 42 can be separated into an area where the polygon mirror 20 is provided and an area where the fθ lens 22 is provided by a rib 44 provided between the polygon mirror 20 and the fθ lens 22. . Thereby, it is possible to suppress the vibration generated when the polygon mirror 20 is driven from being transmitted to the region where the fθ lens 22 is provided as much as possible.

  Further, by integrally forming the rib 44 in the housing 42, the number of parts does not increase and the assembly process of the optical scanning device 10 does not become complicated. Further, the rib 44 can be formed continuously between the side walls 42 </ b> B of the housing 42, whereby the rigidity of the housing 42 can be increased by the rib 44.

  Next, an optical scanning device according to a second embodiment of the present invention will be described. In addition, the description about the part similar to 1st Embodiment is omitted.

  As shown in FIG. 5, an opening 56 is formed at a substantially central portion of the rib 44. The opening 56 is open to the bottom surface 42 </ b> A of the housing 42, leaving the upper frame portion 44 </ b> A. That is, the opening 56 opens to the bottom surface 42 </ b> A of the housing 42, leaving the top portion of the rib 44 as the upper frame portion 44 </ b> A.

  As shown in FIG. 6, the holder 60 is attached from the surface of the opening 56 on the polygon mirror 20 side to the bottom surface 42 </ b> A of the housing 42.

  As shown in FIG. 7A, the holder 60 includes a substantially L-shaped block 62 when viewed from one direction. The base plate 62B of the block 62 is inserted into the opening 56. Wall portions 62A are erected at both ends of the base plate 62B, and openings through which the light beam L passes are formed between the wall portions 62A. Further, when the base plate 62 </ b> B is inserted into the opening 56, the wall 62 </ b> A is positioned in the opening 56. Thereby, the gaps on both sides of the opening 56 are closed. Further, a screw hole 76 is formed in the base plate 62B. A screw 72 is inserted into the screw hole 76, and is inserted and fastened into a screw hole 58 formed in the bottom surface 42A of the housing 42 (see FIG. 5).

  FIG. 7B shows the holder 60 when viewed from the polygon mirror 20 side when the holder 60 is attached to the opening 56.

  A small block 64 is formed on the polygon mirror 20 side of the block 62 (see FIG. 6). In the central portion of the small block 64, an opening 68 having substantially the same size as the opening formed between the wall portions 62A is formed. A step 66 is formed around the opening 68. The fθ lens 24 is fitted into the step 66 and fixed with an adhesive applied to the wall surface 66A constituting the step 66.

  The holder 60 to which the fθ lens 24 is fixed is fitted into the opening 56 and fixed to the bottom surface 42 </ b> A of the housing 42 with the screw 72, so that the opening 56 is closed with the fθ lens 24 and the holder 60.

  Next, the operation of the second exemplary embodiment of the present invention will be described.

  As shown in FIG. 1, when the fθ lens 24 is directly attached to the opening 52 formed in the rib 44, the step portion 54 to which the fθ lens 24 is attached is damaged or the fθ lens 24 is replaced. When it becomes necessary, the housing 42 needs to be replaced.

  Therefore, as shown in FIG. 7, if the fθ lens 24 is held by the holder 60, the holder 60 is attached to the opening 56, and the opening 56 is closed by the fθ lens 24, the fθ lens 24 is replaced. When the necessity arises, the holder 60 may be removed from the housing 42 and replaced.

  Further, as shown in FIG. 8, the ribs 44, 46, 50 and the step 48 have the same height, so that a plate-like lid 78 is placed on the top surfaces of the ribs 44, 46, 50 and the step 48. Thus, the region where the polygon mirror 20 is provided is sealed in the housing 42. That is, the polygon mirror 20 is isolated. Thereby, it is possible to prevent the vibration generated when the polygon mirror 20 is driven from being transmitted to the region where the fθ lens 22 is provided. In addition, noise generated when the polygon mirror 20 is driven can be reduced. Furthermore, dust and dust can be prevented from entering the area where the polygon mirror 20 is provided.

  Next, an optical scanning device 80 according to a third embodiment of the present invention will be described.

  First, a schematic configuration of the optical scanning device 80 will be briefly described.

  As shown in FIG. 9, the optical scanning device 80 has a substantially box-shaped housing 82. The housing 82 is composed of a bottom surface 82A and a side wall 82B erected from the outer periphery of the bottom surface 82A, and the upper opening is closed by a lid (not shown).

  An LD substrate 84 having a light source (LD) for emitting laser light is attached to the side wall 82B of the housing 82, and a collimator lens 86, a cylinder lens 88, a polygon mirror 90, fθ are attached to the bottom surface 82A of the housing 82. Parts such as a lens 94 are installed. A motor (not shown) for rotating the polygon mirror 90 is provided on the motor substrate 92.

  The collimator lens 86 converts the light beam from the LD mounted on the LD substrate 84 into substantially parallel light, passes it through the cylinder lens 88, passes through the opening 83 formed in the rib 81 of the housing 82, and then passes through the polygon mirror. 90 enters and is deflected. The light beam deflected by the polygon mirror 90 is condensed by the fθ lens 94 through the opening 158 formed in the rib 150, and the opening 160 formed in the rib 154 and the opening 96 formed in the side wall 82B. The image is formed on a photosensitive member (not shown) disposed at a position separated from the optical scanning device 80 by a predetermined distance. That is, in the optical scanning device 80, unlike the first embodiment, the light beam is scanned in one plane. The illustration of the SOS mirror, the SOS substrate, etc. for detecting the optical scanning start position is omitted.

  In the optical scanning device 80 having such a configuration, the fθ lens 94 is surrounded by the ribs 150, 152, 156, and 154. The rib 150 is erected from the bottom surface 82 </ b> A of the housing 82 and is continuously formed between the side walls 82 </ b> B of the housing 82. Further, the ribs 152 and 156 are erected from the bottom surface 82 </ b> A of the housing 82 so as to be orthogonal to the rib 150. Further, the rib 154 is formed continuously between the side walls 82 </ b> B of the housing 82 so as to be parallel to the rib 150.

  The rib 150 is formed between the polygon mirror 90 and the fθ lens 94. A rectangular opening 158 is formed at a substantially central portion so that the light beam can pass therethrough. Thus, the light beam deflected by the polygon mirror 90 passes through the opening 158, enters the fθ lens 94, and passes through the opening 160 formed in the rib 154 and the opening 96 formed in the side wall 82B. Then, the light is emitted to a photoconductor (not shown).

  Thus, by providing the rib 150 continuously formed between the side walls of the housing 82 between the polygon mirror 90 and the fθ lens 94, the rigidity of the housing 82 can be increased.

  In this embodiment, the light beam L is applied to both the rib 150 provided between the polygon mirror 90 and the fθ lens 94 and the rib 154 provided at a position facing the rib 150 with the fθ lens 94 interposed therebetween. Although the openings 158 and 160 that pass therethrough are formed, as shown in FIG. 10, the rib 154 may be formed with a notch 162 having a notch shape that opens upward rather than an opening. Since at least the rib 150 between the fθ lens 94 is an opening, the rigidity of the housing 82 can be increased. Therefore, the structure of the mold for molding the housing 82 is compared with the case where two openings are formed. Becomes easier.

1 is a perspective view showing an optical scanning device according to a first embodiment of the present invention. 1 is a perspective view showing an optical scanning device according to a first embodiment of the present invention. It is a fragmentary perspective view which shows the opening part of the optical scanning device concerning the 1st Embodiment of this invention. (A) It is a fragmentary perspective view which shows the opening part of the optical scanner which concerns on the 1st Embodiment of this invention, (B) It is side sectional drawing. It is a fragmentary perspective view which shows the opening part of the optical scanner which concerns on the 2nd Embodiment of this invention. It is a fragmentary perspective view which shows the state which attached the holder to the opening part of the optical scanning device which concerns on the 2nd Embodiment of this invention. It is a disassembled perspective view which shows the holder of the optical scanning device concerning the 2nd Embodiment of this invention. It is a disassembled perspective view which shows the opening part of the optical scanner which concerns on other embodiment of this invention. It is a perspective view which shows the optical scanner which concerns on the 3rd Embodiment of this invention. It is a perspective view which shows the optical scanner which concerns on other embodiment of this invention. It is a perspective view which shows the conventional optical scanning device.

Explanation of symbols

10 Optical scanning device 20 Polygon mirror 22 fθ lens (imaging lens)
24 fθ lens (transmission type optical element)
42 Housing (optical box)
44 rib 46 rib (circumferential rib)
48 steps (side wall)
50 ribs (circumferential ribs)
52 Opening 56 Opening 68 Opening 78 Lid (Cover)
80 Optical scanning device 82 Housing (optical box)
90 polygon mirror 150 rib 158 opening

Claims (4)

A polygon mirror that deflects and scans the light beam emitted from the light source;
An imaging lens that forms an image on the exposure surface of the light beam deflected and scanned by the polygon mirror;
An optical box that accommodates the polygon mirror and the imaging lens and is reinforced by ribs standing from the bottom surface;
A transmissive optical element through which the light beam is transmitted;
In an optical scanning device having
The rib is provided between the polygon mirror and the imaging lens, and the rib is formed with an opening through which the light beam can pass.
A first screw hole is formed on the bottom surface of the optical box on the imaging lens side of the rib,
A base plate in which a second screw hole is formed, a wall portion standing on both ends of the base plate and closing both ends of the opening, and a step provided between the wall portions and holding the transmission optical element And a holding member having the first and second screw holes are detachably attached to the opening by inserting and tightening screws into the first screw hole and the second screw hole, and the opening is formed by the transmissive optical element and the holding member. Part is blocked,
And the rib, the circumferential rib extending in the direction orthogonal to the ribs, the space surrounding the polygon mirror is formed in a side wall of the optical box is an optical scanning device, characterized in that it is closed by the lid.   The optical scanning device according to claim 1, wherein the rib is integrally formed with the optical box continuously between the side walls of the optical box.   The optical scanning device according to claim 1, wherein the opening is opened to the bottom surface leaving a top portion of the rib. The optical scanning device according to claim 1, wherein the circumferential rib and the height of the rib are the same.

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