JP5966551B2 - Optical scanning apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an optical scanning device and an image forming apparatus.

  The image forming apparatus can be implemented as a “laser printer, digital copying machine, or the like” that forms an image by scanning a photoconductive photosensitive member by optical scanning.

  2. Description of the Related Art Image forming apparatuses such as laser printers and digital copying machines are widely known that perform optical scanning using laser light from a laser light source driven by a signal according to image information as scanning light.

  In general, in an optical scanning device equipped with a laser light source, a polygon mirror that deflects and scans a light beam from the laser light source together with the laser light source, or a deflected light beam by the polygon mirror is spot-shaped on an image carrier that forms the substance of the surface to be scanned. The scanning optical system that forms an image, as well as the “circuit board that controls the drive of the laser light source and the polygon mirror” are assembled in the housing as individual components, and the laser light source and the polygon mirror are assembled during assembly. It is necessary to fix each of the components constituting the scanning optical system and the like so that the mutual arrangement is maintained as designed.

For this reason, the optical scanning device has a large number of components, and it takes time to make adjustments to ensure the placement accuracy between the components. In addition, a new design of the optical scanning device is required for each model of the image forming apparatus, which causes an increase in cost.
Conventionally, in order to solve such a problem of cost increase, Patent Documents 1 and 2 disclose a configuration in which the component configuration of the optical scanning device is reviewed to reduce the cost.
In these, the drive circuit of the polygon mirror and the light condensing element are “installed on the same base as a unit” to reduce the number of parts.

2. Description of the Related Art Conventionally, a configuration in which a polygon mirror is pivotally supported on a sheet metal substrate on which a drive circuit is formed is frequently used.
In the optical scanning device, the light spot, the coupling lens that is a condensing optical system, the polygon mirror, and the scanning lens that is a scanning optical system have a uniform spot diameter of the beam spot on the surface of the photosensitive drum that is the surface to be scanned. As described above, each arrangement is adjusted to be fixed to the housing and unitized. However, for each model of the image forming apparatus using the optical scanning device, the “arrangement layout with the photosensitive drum” or “to the photosensitive drum” Since the “incident angle of the light beam” is different, a new unit design is required for each model.

In order to eliminate such an increase in cost, it is necessary to share parts so that the units of a plurality of models can be used in common.
In particular, it is desired to reduce the cost by making mass production possible by making a polygon mirror, which has a relatively high manufacturing cost, common to different models and enabling mass production.
The polygon mirror is “rotated at several tens of thousands of revolutions per minute” and is a part that needs to be replaced as a consumable part. Therefore, it is desired to reduce the cost in order to reduce the maintenance cost.
However, if the polygon mirror is shared and replaced as a single unit, in order to prevent the spot diameter on the surface to be scanned from becoming uneven due to the posture error of the rotation axis of the polygon mirror, For the exchanged polygon mirror, it takes time to readjust the arrangement state such as a coupling lens.

  To avoid this problem, in the past, when a polygon mirror broke down, or when a polygon mirror was replaced and collected for reuse or recycling, replacement was performed in units instead of replacing the polygon mirror alone. Even the parts that do not need to be replaced were replaced, and extra costs were incurred.

  A typical “parts that do not need to be replaced” is a “scanning optical system” such as an fθ lens. The scanning optical system is a “non-moving member” in the optical scanning apparatus, does not generate heat, and needs almost no replacement after being once installed. Also, they are not cheap.

  The present invention has been made in view of the above-described circumstances, and it is an object of the present invention to realize a novel optical scanning apparatus that can easily perform replacement of a polygon mirror, a light source, and the like at low cost, and an image forming apparatus using the same. To do.

Optical scanning device comprising a light source, a focusing optical system for condensing the divergent light beam from the light source, a polygon mirror for deflecting and scanning the light beam from the condensing optical system, deflected by the polygon mirror In an optical scanning device having a scanning optical system for condensing a light beam as a light spot on a surface to be scanned and making the optical scanning constant speed, the light source, the condensing optical system, and the polygon mirror, A core unit that maintains a predetermined positional relationship; and a subunit that supports the scanning optical system. The core unit includes a base member, and the base member has a posture of a rotation axis of the polygon mirror. A posture restraining means for restraining is fixed, and the light source, the condensing optical system, and the polygon mirror are integrally held in a predetermined positional relationship, and the predetermined positional relationship is established with respect to the subunit. Also Is detachable Te, when mounting the core unit to the sub unit has a positioning means for positioning the positional relationship between the units one another,
The positioning means performs positioning at two points: a rotation axis center of the polygon mirror and a position away from the rotation axis center.

  As described above, the portion from the light source to the polygon mirror is held by the core unit, and the scanning optical system is held by the “subunit separate from the core unit”. In this case, it is not necessary to replace the scanning optical system.

In addition, the light source, the condensing optical system, and the polygon mirror are integrated in a “predetermined positional relationship”, and the rotation axis of the polygon mirror is constrained in “position and orientation”. It is possible to appropriately handle the scanning optical system on the unit side, and replacement work is easy.
Further, the positional relationship between the units is determined at two points, that is, the rotational axis center of the polygon mirror and a position away from the center, so that highly accurate positioning is possible.

  For example, replacement when there is a difference in the layout with the photosensitive drum, the incident angle of the scanning light beam on the photosensitive drum, or a difference in the scanning optical system according to the “writing width” such as A3 size or A4 size. Can be easily accommodated.

It is a figure for demonstrating the procedure which assembles a subunit to a core unit. It is a figure for demonstrating the state which assembled | attached the core unit to the subunit. It is a figure which shows another example of a core unit. It is a figure which shows the other example of a core unit. It is a figure for demonstrating another form of implementation of an optical scanning device. It is a figure for demonstrating the state which connected the light source and drive circuit which were fixed to the core unit with the flexible cable. It is a figure for demonstrating the example of the form of the core unit in other forms of implementation of an optical scanning device. It is a figure for demonstrating the example of a form of FIG. It is a figure for demonstrating the assembly | attachment of the core unit and subunit shown in FIG. 7, FIG. It is a figure for demonstrating another form of a core unit. It is a figure which shows the state which assembled | attached the core unit of FIG. 10 to the subunit. It is a figure for demonstrating the assembly | attachment of the core unit of FIG. 10, and a subunit. FIG. 4 is a perspective view showing a state of optical scanning in the color image forming apparatus. It is a figure for demonstrating one Embodiment of a color image forming apparatus.

Hereinafter, embodiments will be described.
FIG. 1 is a diagram for explaining a characteristic part of the invention in one embodiment of an optical scanning device.
This optical scanning device is deflected by a light source 10, a condensing optical system 12 that condenses the divergent light beam from the light source 10, a polygon mirror 14 that deflects and scans the light beam from the condensing optical system 12, and the polygon mirror 14. And a scanning optical system 16 for condensing the luminous flux as a light spot on the surface to be scanned and making the optical scanning at a constant speed.

  It is well known that the direction in which the light spot is moved by optical scanning and the direction corresponding to this direction are called “main scanning direction”, and the direction orthogonal to the main scanning direction and the direction corresponding to this direction are called “sub-scanning direction”. It is.

The light source 10 is a “semiconductor laser” and emits a “divergent laser beam” as is well known.
The condensing optical system 12 is a “coupling lens” and converts a divergent light beam from the light source 10 into a light beam form suitable for the subsequent optical system. Hereinafter, the condensing optical system 12 is referred to as a coupling lens 12.

  In this embodiment, the coupling lens 12 has “a different positive power in the main scanning direction and the sub-scanning direction”. The positive power in the main scanning direction has a collimating function for converting the divergent light beam from the light source 10 into a parallel light beam, and converts the divergent light beam into a focused light beam in the sub-scanning direction.

  The polygon mirror 14 receives the light beam from the coupling lens 12, reflects off the deflecting reflection surface, and rotates at a constant speed, thereby deflecting and scanning the reflected light beam at a constant angular velocity. The light beam from the coupling lens 12 is formed as a “line image long in the main scanning direction” in the vicinity of the deflection reflection surface of the polygon mirror 14.

  The deflected and scanned light beam (referred to as “deflected light beam”) enters the scanning optical system 16. The scanning optical system 16 is a so-called “fθ lens”, and forms an image of a deflected light beam as a light spot on a scanning surface (not shown). Hereinafter, the scanning optical system 16 is referred to as a scanning lens 16.

  The scanning lens 16 speeds up the displacement of the light spot on the surface to be scanned by the fθ function. The scanning lens 16 is also an anamorphic lens having positive powers that are different in the main scanning direction and the sub-scanning direction. With respect to the sub-scanning direction, the imaging position of the above-mentioned “line image long in the main scanning direction” is used. A conjugate relationship is established with the surface to be scanned, thereby correcting “surface tilt of the deflecting / reflecting surface” in the polygon mirror 14.

  In FIG. 1, the part indicated by reference numeral CU is “core unit”, and the part indicated by reference numeral SU is “subunit”.

The core unit CU holds the light source 10, the coupling lens 12, and the polygon mirror 14 in a “predetermined positional relationship” as illustrated.
The sub unit SU supports the scanning lens 16 that is a scanning optical system at a predetermined position.

  The core unit CU has a base member 100. The base member 100 integrally holds the light source 10, the coupling lens 12, and the polygon mirror 14 so that these are in a “predetermined positional relationship”. A connector 13 and an electronic component 13 are also mounted on the base member 100.

  A state in which the base member 100, the light source 10, the coupling lens 12, and the polygon mirror 14 are attached to the base member 100 will be described.

The base member 100 is formed of a sheet metal (a parallel plate made of a metal such as aluminum), and includes a first plate surface portion 101 and a second plate surface portion 102.
A coupling lens 12 and a polygon mirror 14 are attached to the first plate surface portion 101, and a light source 10 is attached to the second plate surface portion 102.
The surface of the second plate surface portion 102 is orthogonal to the surface of the first plate surface portion 101.

  The polygon mirror 14 includes a polygon mirror portion having a plurality of deflection reflection surfaces (four surfaces in the example being described), a rotation drive mechanism (coil for generating driving force) that rotates the polygon mirror portion around a rotation axis, It has “posture restraining means” for restraining the posture of the rotating shaft (the direction of the rotating shaft that does not vary due to rotation). The “posture restraining means” is a bearing (bearing) that pivotally supports the rotating shaft or a “shaft supporting member that holds the bearing”.

The polygon mirror 14 is integrated with the base member 100 by fixing the posture restraining means to “a predetermined position in the first plate surface portion 101” of the base member 100.
The orientation (orientation) of the rotation axis of the polygon mirror 14 is designed to be “the direction orthogonal to the plate surface” of the first plate surface portion 101, but in reality, there is an error. It is not “a direction strictly perpendicular to the first plate surface portion”.

  However, as described above, the position of the polygon mirror attached to the first plate surface portion 101 of the base member 100 with respect to the first plate surface portion 101 and the attitude of the rotating shaft are determined.

The light source 10 is a semiconductor laser as described above, and is provided on the second plate surface portion 102.
That is, the outer portion of the semiconductor laser package is fixed by being press-fitted into a “fitting hole” formed in a predetermined position of the second plate surface portion 102. At this time, the posture of the semiconductor laser is adjusted so that the central beam of the divergent laser beam is in a direction orthogonal to the second plate surface portion 102.

  The circuit board 110 on which a drive circuit that keeps the output of the semiconductor laser as the light source 10 constant and modulates according to the image signal is fixed to the back side of the second plate surface portion 102.

  In general, since the sheet metal substrate is limited to a single layer, if the circuit scale is large, it may be possible to reduce the total cost by configuring the substrate by using a separate substrate, and in the example being described, the polygon mirror 14 may be reduced. Are formed on the first plate surface portion 101, and the semiconductor laser drive circuit is formed on a separate circuit board 110 and arranged on the back surface side of the second plate surface portion 102.

  Between the light source (semiconductor laser) 10 and the polygon mirror 14, a coupling lens 12 for condensing the light beam from the light source 10 as described above is disposed. The coupling lens 12 is a first plate. It is fixed to the standing bent portion 103 formed on the surface portion 101.

  In the “optical axis direction”, the coupling lens 12 converts the divergence constraint from the light source 10 into a parallel light beam in the main scanning direction, and “in the vicinity of the deflecting reflection surface of the polygon mirror 14” in the sub-scanning direction. The position is adjusted so as to form an image as a “line image long in the main scanning direction”.

  There is a possibility that the axis of rotation of the polygon mirror 14 may be “axially tilted due to an attitude error.” When such an axis is tilted, the light beam incident on the deflecting / reflecting surface from the light source 10 side is a surface including the rotational axis. In this case, the incident light is incident from a direction different from the “designated incident direction”, and “a light spot having a uniform spot diameter cannot be obtained at all scanning positions”.

  In order to cope with this problem, when the coupling lens 12 is fixed to the standing and bending portion 103, a “first plate surface portion” is used for the semiconductor laser together with the above “position adjustment in the optical axis direction” using a jig. Position adjustment in the direction orthogonal to 101, that is, "position adjustment in the sub-scanning direction" is also performed.

  Then, the position is adjusted and held, and an adhesive is filled in the “gap between the standing bent portion 103 and the coupling lens 12” to fix the coupling lens 12 to the standing bent portion 103.

  In this state, the three of the light source 10, the coupling lens 12, and the polygon mirror 14 have a “predetermined positional relationship” and are fixedly held on the base member 100.

  In other words, the divergent light beam (laser light beam) from the light source 10 is converted into a parallel light beam in the main scanning direction by the coupling lens 12, and in the sub-scanning direction, near the deflection reflection surface of the polygon mirror 14, “in the main scanning direction”. In the form of a light beam that forms a “long line image”, it enters the polygon mirror 14 and is deflected and scanned by the polygon mirror 14.

On the other hand, the subunit SU is formed by supporting a scanning lens 16 as a scanning optical system at a predetermined position on a support substrate 200 made of a parallel plate-shaped sheet metal.
The scanning lens 16 is fixedly supported by support columns 201, 202, and 203 formed on the support substrate 200. The support position and support position of the scanning lens 16 are adjusted so as to have a predetermined relationship with the support substrate 200.

  The core unit CU is detachable with a “predetermined positional relationship” with respect to the subunit SU. The “predetermined positional relationship” between the core unit CU and the subunit SU is “when the core unit CU is fixedly attached to the subunit SU,“ a position where the relationship between the deflected light beam by the polygon mirror 14 and the scanning lens 16 is appropriate. This is a positional relationship.

  Here, alignment when both units are mounted will be described.

  As shown in FIG. 1, the first plate surface portion 101 of the core unit CU has an in-plane perpendicular to the rotation axis of the polygon mirror 14 with respect to the scanning lens 16 fixed to the subunit SU (“main scanning surface”). In addition, the hole H1 which is a coupling portion for “relatively accurately positioning” the units is provided such that “the incident state of the deflected light flux on the scanning lens 16 is a predetermined state”. On the other hand, the support substrate 200 of the subunit SU is provided with a hole H2 and a pin P1.

  These holes and pins constitute “positioning means” for relatively accurately positioning the positional relationship between the units when the core unit CU is attached to the subunit SU.

  As shown in FIG. 1, the pin P1 formed in the subunit SU is fitted into the hole H1 of the first plate surface portion 101 on the core unit CU side. In addition, a “fitting shaft (not shown)” that is coaxial with the rotational axis of the polygon mirror 14 is fitted into the hole H2 formed in the subunit SU.

  The hole H2 formed in the subunit SU and the “fitting shaft” of the polygon mirror 14 constitute means for determining the position of the polygon mirror 14 with respect to the base member 100.

In this way, after aligning the core unit CU with the subunit SU and determining the mutual positional relationship, the two are “fixed with screws” to form an optical scanning device.
Of course, the core unit CU can be removed from the state in which the core unit CU is fixed to the subunit SU by removing the coupling. That is, the core unit CU is detachable from the subunit SU.

  FIG. 2 shows a state where the core unit CU is mounted on the subunit SU as viewed from the direction of the rotation axis of the polygon mirror 14 (sub-scanning direction). Symbol BS indicates a “screw” for fastening.

As shown in FIGS. 1 and 2, it is preferable in terms of accuracy to perform positioning at “two points: the center of the rotation axis of the polygon mirror 14 and a position at a certain distance (the position of the hole H1)”. If the positional relationship between the rotation axis center of the polygon mirror 14 and the scanning lens 16 is not ensured accurately, the scanning speed due to the light spot changes, a magnification error occurs, and a color image has a problem such as a large color shift. This is to prevent this.
The positioning position may be a position other than the hole H1, and may be positioning by shape such as “corner and surface” or “surface and surface” instead of the pin and hole. Other appropriate means can be used as the posture restraining means.

  In the embodiment described above, since the positional relationship between the light source 10, the coupling lens 12, and the polygon mirror 14 held in the core unit CU is determined as “predetermined positional relationship”, the core unit of the same specification is used. If there are different core units, the “deflection state” of the deflected light beam deflected and scanned by the polygon mirror 14 is the same.

Therefore, in the optical scanning device used for the same type of image forming apparatus, when the polygon mirror is replaced, the side of the subunit supporting the scanning lens 16 is not replaced, only the core unit is replaced. Therefore, it is possible to obtain an optical scanning device having the same performance only by mounting on a subunit that is not exchanged.
This replacement is not affected at all by the optical system after the scanning lens, for example, the arrangement of a mirror or the like for guiding the deflected light beam to the surface to be scanned. Even if there is a difference in layout due to angle, etc., it can be exchanged in units of core units without much effort.

  In addition, since the scanning lens is provided in the subunit, it is possible to “commonize in units of core units” regardless of the scanning lens, and common to “optical scanning devices with different writing widths” such as A4 size and A3 size. The core unit can be installed and the cost can be greatly reduced.

3 and 4 show a modification.
In the embodiment shown in FIG. 3, the polygon mirror drive substrate 140 on which the drive circuit for the polygon mirror 14 is formed is formed separately from the base member 100 and joined to the first plate surface portion 101 of the base member 100.
Instead of this, a semiconductor laser drive circuit can be formed on the second plate surface portion 102 (the back surface) of the base member 100 or the like.

In the embodiment shown in FIGS. 1 and 2, the standing bent portion 103 is formed on the first plate surface portion 101, and the coupling lens 12 is supported by this portion. However, as in the embodiment shown in FIG. It is also possible to form a standing portion 12A integrally formed with the ring lens 12 and to directly bond this to the first plate surface portion 101.
The standing portion 12A in which the coupling lens 12 is integrally formed may be directly joined to the first plate surface portion 101 of the base member shown in FIG.

  In the embodiment described above, the base member 100 is formed of a sheet metal, and the first plate surface portion 101 that fixes the posture restraining means of the polygon mirror 16 and the second plate surface orthogonal to the first plate surface portion 101. The light source 10 has a plate surface portion 102 and is fixed with the emission direction constrained so that the “principal ray of the light beam” is emitted in a direction orthogonal to the second plate surface portion 102.

  This eliminates the need for separate support means for positioning and supporting the light source with respect to the polygon mirror, thereby reducing the number of parts of the optical scanning device and reducing costs.

  Further, the coupling lens 12 that is a condensing optical system has a polygonal mirror 14 so as to define the incident direction of the light flux from the light source 10 on the deflecting / reflecting surface within the plane including the rotation axis of the polygonal mirror 14. The position is adjusted according to the posture of the rotation shaft, and the base member 100 is fixed.

  For this reason, optical performance can be guaranteed in units of core units.

  The base member may be provided with a “polygon mirror drive circuit and a light source drive circuit”. In this way, “consumables that need to be replaced over time can be replaced without adjustment”. Maintenance costs can be reduced.

FIG. 5 shows another embodiment of the optical scanning device.
This embodiment is an example in which “a structure that supports an image carrier that is a surface to be scanned” is used as a subunit that supports a scanning lens that is a scanning optical system.

  The core unit CU has the same configuration as that shown in FIG. 1, and the light source 10, the coupling lens 12, and the polygon mirror 14 are fixedly held in a “predetermined positional relationship”.

  On the other hand, the subunit SU is formed by supporting the scanning lens 16 on the main body structure 300.

The main body structure 300 is a “structure that supports an image carrier (photosensitive drum) that is a surface to be scanned”, and includes a pair of side plates and a bottom plate that form an outline of the main body of the image forming apparatus. It is a member that positions and supports the photosensitive drum and the “unit that holds the photosensitive drum”, such as a structural member that maintains rigidity by bridging the frame casing or side plates to be formed.
Since the arrangement of the semiconductor laser 10, the coupling lens 12, and the polygon mirror 14 is adjusted in units of core units, the “units for positioning (pins and pins) are formed by forming the core unit CU in the core unit CU and the main body structure 300. It is possible to construct an optical scanning device without using a housing and to perform positioning with respect to the photosensitive drum.

  In FIG. 5, symbol SL indicates a slit formed in the main body structure 300. The mirror denoted by reference symbol M constitutes a part of an optical path that reflects the deflected light beam that has passed through the scanning lens 16 and passes through the slit SL toward the photosensitive drum below the main body structure 300.

  According to such a configuration, the optical scanning device can be configured without using a housing, the number of parts can be reduced, the assembly process can be simplified, the number of steps can be reduced, and the manufacturing cost of the image forming apparatus can be reduced.

  FIG. 6 illustrates characteristic portions of another embodiment in an explanatory manner.

  “At least one of a polygon mirror drive circuit and a light source drive circuit” can be formed on the plate surface of the base member made of sheet metal, and in this way, the base member is used as a circuit board. Therefore, the number of parts can be reduced and the cost can be reduced.

  In the embodiment of FIG. 6, a “polygon mirror drive circuit (not shown)” is mounted on the plate surface of the first plate surface portion 101 to which the polygon mirror is fixed, and on the back surface side of the second plate surface portion 102. A drive circuit (not shown) of a semiconductor laser that is the light source 10 is mounted.

  A terminal of the semiconductor laser press-fitted into the fitting hole of the second plate surface portion 102 and a “semiconductor laser drive circuit (not shown)” formed on the back surface side of the second plate surface portion 102 are the flexible cable 112. Connected by.

  If comprised in this way, the base member in which at least any one of the drive circuit of a polygon mirror or the drive circuit of a light source was formed can be used as a circuit board, a number of parts can be reduced and cost can be reduced.

Another embodiment will be described with reference to FIGS.
FIG. 7 shows a portion of the core unit CU. Since it is considered that there is no possibility of confusion, the symbol “CU” is assigned to the core unit and the symbol “SU” is assigned to the subunit in each of the following drawings in order to avoid complication.

  In FIG. 7 showing the core unit CU, the base member 100A is formed of a sheet metal (a parallel plate made of a metal such as aluminum), but is different from the base member 100 shown in FIG.

A light source 10 (semiconductor laser), a coupling lens 12A, and a polygon mirror 14 are fixed to a “predetermined positional relationship” on one surface of the base member 100A to form a core unit CU.
The base member 100 </ b> A is also loaded with a connector 11 and an electronic component 13.

  The attachment of the light source 10 to the base member 100A will be described with reference to FIGS. 7 and 8. The light source 10 is a semiconductor laser, and the outer portion of the package is the base as in the embodiment shown in FIG. The member 100A is press-fitted and fixed in a “fitting hole” formed at a predetermined position of the member 100A. At this time, the “posture of the semiconductor laser” is adjusted so that the central beam of the divergent laser beam is in a direction orthogonal to the plate surface portion of the base member 100A.

  A circuit board 110 on which a drive circuit that keeps the output of the semiconductor laser as the light source 10 constant and modulates it in accordance with an image signal is fixed to the back side of the base member 100A.

  Next, attachment of the polygon mirror 14 to the base member 100A will be described with reference to FIGS. In the embodiment described above, the “attachment to the base member” of the polygon mirror 14 has not been described in detail. However, in each of the above-described embodiments, the polygon mirror is attached by a method described below. It is the same.

  The polygon mirror 14 constrains the posture of the polygonal mirror portion 14A having a plurality of deflecting reflection surfaces (four in the example being described), a rotational drive mechanism for rotating the polygonal mirror portion around the rotational axis, and the posture of the rotational shaft. It has “posture restraining means”.

  As shown in FIGS. 8 and 9, the “rotation drive mechanism” includes a coil 14 </ b> C fixedly provided on the base member 100 </ b> A and a magnet housed in a portion indicated by reference numeral 14 </ b> B in FIG. 8. The polygonal mirror portion 14A is rotated by controlling energization to the coil 14C by a drive circuit that is not performed.

  The “posture restraining means” includes a shaft 14E that is coaxially integrated with the rotating shaft, and a bearing 14D that is a bearing that supports the shaft 14E. The bearing 14D restrains the orientation of the shaft 14E, so that the posture of the rotation axis of the polygon mirror 14 is restrained.

That is, the portion of the hole H3 of the base member 100A is surrounded, the coil 14C is fixedly arranged, the shaft 14E is fitted into the bearing 14D through the hole H3 , and is fixed to the base member 100A by the bearing 14D.

  At this time, the position of the polygon mirror 14 with respect to the base member 100A is determined by the “fit” of the hole H3 and the shaft 14E, and the posture of the rotating shaft is constrained by the fit of the bearing 14D and the shaft 14E. .

  Next, the coupling lens 12A that is a condensing optical system will be described.

  The coupling lens 12A is formed in a shape shown in a perspective view in FIGS. 7 and 9, and is fixed to the base member 100A so as to cover the position of the light source 10 on the surface of the base member 100A.

  As shown in FIG. 8, the coupling lens 12A has three optical surfaces 12A1, 12A2, and 12A3.

The optical surface 12A1 is a “lens surface”, and its arrangement is adjusted so that its optical axis position matches the central light beam of the diverging constraint emitted from the light source 10 (perpendicular to the plate surface of the base member 100A). Has been.
The lens surface 12A1 is an anamorphic surface, and the divergent light beam from the light source 10 is converted into a parallel light beam in the main scanning direction (direction orthogonal to the drawing), and is converted into a convergent light beam in the sub-scanning direction. To do.

  The light beam whose form has been converted by the lens surface 12A1 enters the optical surface 12A2. The optical surface 12A2 is a flat reflecting surface and is inclined at an angle of 45 degrees with respect to the plate surface of the base member 100A. The flat reflective surface 12A2 is coated with a reflective material.

  The light beam incident on the flat reflecting surface 12A2 is reflected by the flat reflecting surface 12A2 in a direction parallel to the plate surface of the base member 100A and enters the optical surface 12A3. The optical surface 12A3 is a flat “emission surface”.

  The light beam emitted from the exit surface 12A3 enters the polygon mirror 14 as a light beam parallel to the plate surface of the base member 100A, and is deflected and scanned at a constant angular velocity as the polygon mirror 14 rotates at a constant speed.

  In FIG. 8, the light beam emitted from the exit surface 12A3 of the coupling lens 12A and incident on the polygon mirror 14 is drawn as a “parallel light beam”. The incident light beam to the mirror 14 is a converged light beam in the sub-scanning direction (vertical direction in FIG. 8), and is formed as a “line image long in the main scanning direction” in the vicinity of the deflection reflection surface of the polygon mirror 14 in the sub-scanning direction. By doing so, "correction of the tilting of the polygon mirror 14" is performed together with the scanning lens.

  As described above, the divergent light beam from the light source 10 is converted into such a “light beam parallel to the main scanning direction and convergent in the sub-scanning direction”. This is done by making the lens surface 12A1 an “anamorphic lens surface”.

  However, the present invention is not limited to this, and the lens surface 12A1 is converted to a parallel light beam in both the main and sub-scanning directions as an “axisymmetric lens surface”, and the exit surface 12A3 is defined as “a cylinder surface having positive power in the sub-scanning direction”. The necessary convergence in the sub-scanning direction may be given.

  In order to make the light beam incident on the polygon mirror 14 “convergent in the sub-scanning direction”, a cylinder lens having a positive power in the sub-scanning direction is separately provided between the coupling lens and the polygon mirror. You may make it do.

  Of course, if it is not necessary to correct surface tilt, the light beam emitted from the exit surface 12A3 may be a parallel light beam, or the light beam emitted from the exit surface 12A3 may be a parallel light beam but in the vicinity of the surface to be scanned in the scanning optical system. In addition, it is possible to correct surface tilt by providing a “cylinder lens having positive power” or a toroidal lens in the sub-scanning direction.

  The coupling lens 12 </ b> A is “a direction in which the light source 10 is adjusted in the direction parallel to the plate surface of the base member 100 </ b> A and is incident on the polygon mirror 14 simultaneously with the position adjustment in the optical axis direction by the jig. Are accurately positioned in a state adjusted in the plane including the rotation axis, and then fixed to the base member 100A.

The core unit CU configured in this manner is attached to the subunit SU as follows.
That is, as shown in FIG. 9, the bearing 14D, which is a shaft support member that holds the rotation shaft of the polygon mirror 14, is inserted into the fitting hole H10 formed in the support substrate 200A of the subunit SU with the outer periphery as a reference. Fit together.

  Thereby, the rotational axis position of the polygon mirror 14 is fixed with respect to the subunit SU. Further, as in the embodiment of FIG. 1, the pin P1 formed on the support substrate 200A of the subunit SU is the hole H1 formed on the base substrate 100A (there is no possibility of confusion. 1 are used as in (1).

  In this way, “the polygon mirror 14 is positioned with respect to the scanning lens 16 fixedly provided on the support substrate 200A”, and the core unit CU is attached and fixed to the subunit SU to obtain an optical scanning device. The core unit CU and the subunit SU are fastened together by fixing the screw hole BS with a screw (not shown).

  The case where there is one light source and one coupling lens has been described above, but a plurality of light sources and coupling lenses may be used.

An embodiment in such a case will be described with reference to FIGS.
In this embodiment, it has two light sources 10C, 10D and two condensing optical systems (coupling lenses 12C, 12D). The polygon mirror 14 is shared by the light beam from the light source 10C and the light beam from the light source 10D.

  The base substrate 100B of the core unit CU is bifurcated on the light source side, and the end on the opened side is bent perpendicular to the portion (first plate surface portion 101B) held by the polygon mirror 14. The second plate surface portions 102C and 102D are formed.

  The light sources 10C and 10D are semiconductor lasers, and the outer portion of the package is press-fitted into the second plate surface portions 102C and 102D, respectively, and the central beam of the divergent light beam from these is subjected to the second plate surface portions 102C and 102D. The posture is constrained so as to radiate so as to be orthogonal to.

  Reference numerals 110C and 110D respectively denote "circuit boards on which drive circuits for keeping the outputs of the semiconductor lasers 10C and 10D constant and modulating them in accordance with image signals" are formed. These are the second plate surface portion 102C, It is fixed to the back side of 102D.

  The coupling lenses 12C and 12D are each a bent portion formed on the base substrate 100B so as to perform the same optical function as the coupling lens 12 in the above-described embodiment with respect to the light beams from the light sources 10C and 10D. 103C and 103D are fixed.

  On the other hand, the subunit SU to / from which the core unit CU is attached / detached has a configuration in which the two scanning lenses 16C and 16D are fixed to the support substrate 200B in a “predetermined positional relationship” as shown in FIG.

  The scanning lens 16C is for the light beam from the light source 10C, and the scanning lens 16D is for the light beam from the light source 10D. As shown in FIG. 12, the pin P1 formed on the support substrate 200B is fitted into the hole H1 formed in the base substrate 100B, and the axis of the polygon mirror 14 is aligned with the support substrate 200B as in FIG. The positional relationship between the core unit CU and the subunit SU is determined by fitting in the hole H2. Thereafter, as in the above-described embodiment, both units are fastened by screwing screws (not shown) into the screw holes BS.

FIG. 11 shows a state in which the core unit CU is mounted and fixed on the subunit SU as viewed from the direction of the rotation axis of the polygon mirror 14.
As shown in the figure, the light beam incident on the polygon mirror 14 from the light source 10C via the coupling lens 12C and the side incident on the polygon mirror 14 from the light source 10D via the coupling lens 12D are the rotational axes of the polygon mirror 14. The position is connected to the hole H1 and is symmetrical with respect to the plane orthogonal to the drawing, and the deflected light beam by the polygon mirror 14 is also symmetrical with respect to the plane (however, the directions of deflection are opposite to each other). To be done.

  In addition, it replaces with the base member 100B, uses the thing of the whole flat form, attaches the light sources 10C and 10D as FIG. 7 etc., replaces with the coupling lenses 12C and 12D, and shows in FIG. Needless to say, the coupling lens 12A or the like may be used.

  As described above, a plurality of light sources and condensing optical systems are arranged, and a structure that scans with a common polygon mirror can consolidate "optical systems of multiple image forming stations" and reduce the number of parts of the optical scanning device. This can simplify the assembly process, reduce the number of man-hours, and reduce the manufacturing and assembly costs of the optical scanning device.

In each of the embodiments described above, the core unit CU and the subunit SU are the back surface of the base member 100 (100A, 100B) and the upper surface of the support substrate 200 (200A, 200B) of the subunit SU. The “positional relationship in the lens width direction (sub-scanning direction)” between the polygon mirror 14 and the like arranged in the core unit CU and the scanning lenses 16, 16C, and 16D supported by the subunit SU is properly set. In order to set, a “predetermined interval” is provided between the two surfaces.
In FIG. 1, FIG. 9, and FIG. 12, the screw hole BS formed in the subunit SU protrudes in a columnar shape by a “predetermined height” from the upper side surface of the support substrate 200 (200A, 200B) of the subunit SU. Thus, the positional relationship is appropriately set according to the predetermined height.

  The screw hole BS is formed in the upper end surface of the protruding convex portion. That is, the “cylindrical convex portion” formed on the support substrate of the subunit is a spacer for properly setting the “positional relationship in the lens width direction (sub-scanning direction)” between the core unit and the subunit. Playing a role.

  Accordingly, the screw hole BS formed in the support substrate of the subunit forms part of the “positioning means”.

In general, an optical scanning device includes a “synchronization detection unit for determining write timing” in order to determine a start position (write start position) of optical scanning on a surface to be scanned.
As an example of such synchronization detection, as shown in FIG. 6, a synchronization sensor is formed on a circuit formed in the same manner as the polygon mirror drive circuit in the vicinity of the light source 10 in the second plate surface portion 102 of the base substrate. A synchronization detecting means may be provided on the core unit side by mounting SN or the like, and the light beam deflected and scanned by the polygon mirror 14 without passing through the scanning lens 16 may be detected. A holding unit for holding a circuit board on which the sensor is mounted may be provided, and the deflected light beam may be detected via the scanning lens 16.

13 and 14 are diagrams for explaining an example of the image forming apparatus.
This image forming apparatus is a tandem multicolor image forming apparatus.

  As shown in FIG. 14, the color image forming apparatus has an intermediate transfer belt 151 as an intermediate transfer member, and four photosensitive drums Y, M, C, and BK are provided along the moving direction of the belt. Yes. Here, “Y, M, C, and BK” represent “yellow, magenta, cyan, and black”, and the photosensitive drums Y, M, C, and BK are for forming the above-described images of the respective colors. Indicates that there is.

  The photosensitive drums Y, M, C, and BK are arranged in parallel along the belt surface of the intermediate transfer belt 15, and an “image forming station” is configured by these photosensitive drums and peripheral devices.

  That is, a yellow toner image is formed at the yellow image forming station, a magenta toner image is formed at the magenta image forming station, a cyan toner image is formed at the cyan image forming station, and a black toner image is formed at the black image forming station.

Image formation will be described on behalf of the “yellow image forming station”.
Around the photosensitive drum Y, a charging charger Y1 that uniformly charges the surface of the photosensitive drum Y, and a developing roller that attaches a charged toner to an electrostatic latent image formed by the optical scanning device and visualizes it. A developing device Y2 provided with an intermediate transfer belt, a primary transfer roller (not shown) for primarily transferring a toner image on the photosensitive drum Y to the intermediate transfer belt 151, and a photoconductor after transfer. A cleaning means Y3 for scraping and storing the toner remaining on the drum Y is disposed.

  The photosensitive drum Y is uniformly charged by the charging charger Y1, and an “electrostatic line image corresponding to a yellow image” is formed by optical scanning by the optical scanning device. This electrostatic ray image is developed by the developing device Y2, and a yellow toner image is formed. The formed yellow toner image is transferred onto the intermediate transfer belt 151.

  In the magenta or black image forming station, a magenta toner image, a cyan toner image, and a black toner image are formed on the corresponding photosensitive drums M to BK in the same manner as described above, and these color toner images are aligned with each other. The images are transferred onto the intermediate transfer belt 151 so as to overlap each other, thereby forming a color image.

  A recording sheet as a sheet-like recording medium is fed from a sheet feeding device 152 by a sheet feeding roller, and is sent out to a transfer site by a registration roller pair 153 in accordance with “recording start timing in the sub-scanning direction”.

  The color image superimposed on the intermediate transfer belt 151 is collectively transferred onto a recording sheet by a secondary transfer roller 154 as a secondary transfer unit at a transfer portion. The recording paper to which the color image is transferred is sent to a fixing device 155 having a fixing roller and a pressure roller, and the color image is fixed. After the fixing, the recording paper is discharged and stacked on a paper discharge tray 157 formed on the upper surface of the main body of the image forming apparatus by a paper discharge roller pair 156.

In this color image forming apparatus, two optical scanning devices are used as shown in FIGS. These two optical scanning devices are represented by symbols SYM and SCBK.
The optical scanning devices SYM and SCBK are structurally the same, and specifically the same as those described with reference to FIGS.
The optical scanning device SYM performs optical scanning on the photosensitive drums Y and M, and the optical scanning device SCBK performs optical scanning on the photosensitive drums C and BK.

  An optical path bending mirror ML that bends the light guide path for guiding the light beam that has passed through the scanning lens is provided from each optical scanning device to the corresponding photosensitive drum.

CU Core unit SU Sub unit 10 Light source (semiconductor laser)
12 Coupling lens (Condensing optical system)
14 Polygon mirror 16 Scanning lens (scanning optical system)
H1, H2 hole P1 pin

JP 2000-11824 A JP 2002-258188 A

Claims (10)

A light source, a condensing optical system for converging a divergent light beam from the light source, a polygon mirror for deflecting and scanning the light beam from the condensing optical system, and a light beam deflected by the polygon mirror on the surface to be scanned In an optical scanning device having a scanning optical system that collects light as a spot and makes optical scanning at a constant speed,
And the light source, and the light converging optical system, and said polygon mirror, a core unit for holding a predetermined positional relationship,
Anda subunit supporting said scanning optical system,
The core unit has a base member, said base member, to secure the attitude restraining means for restraining the orientation of the rotation axis of the polygon mirror, and the light source, and the light converging optical system, and said polygon mirror, It is integrally held in a predetermined positional relationship, and can be attached to and detached from the subunit with a predetermined positional relationship.
When mounting the core unit to the sub unit has a positioning means for determining position positional relationship of the unit one another,
The optical scanning device characterized in that the positioning means performs positioning at two points, a rotation axis center of the polygon mirror and a position away from the rotation axis center . The optical scanning device according to claim 1,
The positioning means includes a first hole configured to fit a shaft coaxial with a rotation axis of the polygon mirror when the core unit is attached to the subunit, and is separated from the first hole. A second hole at a position, and using the first hole and the second hole, the positioning is performed,
The optical scanning device, wherein the subunit and the core unit are fixed to each other in the positioned state using the first hole and the second hole. The optical scanning device according to claim 1 or 2,
The base member is formed of sheet metal, and has a first plate surface portion that fixes the posture restraining means of the polygon mirror, and a second plate surface portion that is perpendicular to the first plate surface portion,
An optical scanning device characterized in that the light source is fixed by restricting an emission direction so that a light beam is emitted in a direction orthogonal to the second plate surface portion. The optical scanning device according to any one of claims 1 to 3,
The condensing optical system according to the attitude of the rotation axis of the polygon mirror so as to define the direction of incidence of the light beam from the light source on the deflection reflection surface within the plane including the rotation axis of the polygon mirror. An optical scanning device characterized in that the position is adjusted and fixed to a base member. The optical scanning device according to claim 1 or 2,
The base member is formed of sheet metal,
The plate surface for fixing the posture restraining means is orthogonal to the rotation axis of the polygon mirror,
The light source is fixed to a portion of the plate surface, constraining the emission direction so as to radiate a light beam in a direction perpendicular to the plate surface,
An optical scanning device comprising: a reflection member that changes a direction of a light beam from the light source within a plane including the rotation axis. In the optical scanning device according to any one of claims 1 to 5,
An optical scanning device, wherein the base member is provided with a drive circuit for the polygon mirror and a drive circuit for the light source. The optical scanning device according to claim 6.
The base member is formed of a sheet metal, and at least one of the drive circuit for the polygon mirror and the drive circuit for the light source is formed on the surface of the sheet metal. The optical scanning device according to any one of claims 1 to 7,
With a single polygon mirror in common, multiple combinations of light sources and condensing optics are deployed,
An optical scanning device that scans light beams from different light sources in different directions by the polygon mirror. The optical scanning device according to any one of claims 1 to 8,
An optical scanning device, wherein the scanning optical system is fixed as a subunit with a structure supporting an image carrier as a scanning surface. An image forming apparatus comprising the optical scanning device according to claim 1.

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