JP5106003B2 - Optical scanning device - Google Patents

Description

  The present invention relates to an optical scanning apparatus that performs optical writing using a laser beam in an image forming apparatus such as an LBP, a digital copying machine, or a digital FAX.

  Conventionally, in an optical scanning device using an optical deflection device that performs sinusoidal vibration, a deviation between the center of the deflection angle of the laser beam deflected and scanned and the center of the imaging optical system, that is, between the optical deflection device and the imaging optical system. A device for adjusting the mounting angle deviation has been proposed. Thereby, a change in linear velocity and aberration are reduced (see, for example, Patent Document 1).

Japanese Patent No. 3445691

  However, in the above conventional example, the deflecting surface is arranged so as to be orthogonal to the mounting surface parallel to the scanning plane, and thus there are the following problems.

  Conventionally, the deflecting surface of the optical deflecting device is configured to be substantially orthogonal to the mounting surface parallel to the scanning plane and fixed at its root portion, and the entire optical deflecting device is cantilevered with the root as a support portion against vibration. It is the arrangement which becomes. Then, there may be a vibration mode that vibrates so that the entire mirror surface fluctuates back and forth depending on the frequency band, and the scanning line height changes with each vibration cycle, and there is a risk that the scanning pitch will be uneven at the time of printing. is there. In addition, there is a possibility that an unexpected vibration mode may be put on the vibration mode of the deflection surface.

  The object of the invention according to the present application is to eliminate the above-mentioned problems and to improve the image quality by stabilizing the vibration mode of the deflection surface.

In order to achieve the above object, a typical configuration according to the present invention includes a light source for emitting a laser beam and a deflection surface for deflecting and scanning the laser beam emitted from the light source by oscillating by resonance vibration. A plate member including the movable element, an actuator unit that swings the movable element, a holding member that holds the plate member and the actuator part, and a laser beam deflected and scanned by the deflection surface of the movable element. An optical box configured in a box shape by a passing lens, a bottom portion, and a side wall portion surrounding the bottom portion, the optical box holding the light source and the holding member and including the lens in the optical scanning apparatus, the holding member is fixed to the side wall portion from the outside of the optical box, the holding member includes a first seat surface abutting on said plate member, A second seating surface is formed which abuts on the serial side wall portion, and the second seating surface is Ri parallel der and the deflecting surface in the initial rest state of the movable element, said second seating surface and the first seat surface Are in the same plane .

  According to the above configuration, the optical deflecting device can be firmly assembled to the optical box while reducing the influence of vibration or the like.

[First Embodiment]
A first embodiment of the present invention will be described with reference to the drawings.

(Image forming device)
First, an outline of the configuration and operation of the image forming apparatus will be described. FIG. 1 is a cross-sectional view illustrating a configuration of an image forming apparatus including an optical scanning device.

  As shown in FIG. 1, in the image forming operation, first, a laser beam L modulated based on image information is emitted from an optical scanning device, and the photosensitive drum 32 (on the surface to be scanned) is scanned. Thereby, a latent image is formed on the photosensitive drum 32. This latent image is formed on the surface of the photosensitive drum 32 that is uniformly charged by the primary charger 33.

  The latent image is visualized by the developer (toner) of the developing device 34. Thereafter, the toner images formed on the surface of the photosensitive drum 32 are sequentially transferred onto the transfer material 36 conveyed to the transfer nip portion by the transfer roller 35, and a toner image is formed on the transfer material 36. After the image formed on the transfer material 36 is thermally fixed by the fixing device 37, the transfer material 36 is output to the outside of the apparatus by the discharge roller 38 or the like.

(Optical scanning device)
Next, an outline of the configuration and operation of the optical scanning device will be described.

  The configuration of the optical scanning device will be described with reference to FIG. FIG. 2 is a perspective view illustrating a schematic configuration of the optical scanning device according to the first embodiment.

  As shown in FIG. 2, members constituting the optical scanning device are integrally accommodated and held in an optical box 31 as a device housing. Here, the optical box 31 has a box shape constituted by a bottom portion and a side wall portion, and includes an fθ lens 43. In addition, the light source device 41, the light deflection device 42, the reflection mirror 44, the BD mirror 45, the BD sensor 46, and the cylinder lens 47 are assembled in the optical box 31.

  As shown in FIG. 2, the light deflection device 42 is assembled to the outer wall surface of the optical box 31 from the outside of the optical box 31. In this configuration, the light deflection device 42 is located on the outermost side. Since the conventional optical deflecting device is arranged inside the optical scanning device, the outer wall of the optical scanning device is arranged outside the optical deflecting scan so as to cover the whole, so that the entire device is increased in size and cost. It was. On the other hand, this structure can make the size of the optical box 31 the smallest. The light deflection device 42 is firmly fixed to the optical box 31 with screws (not shown) (C portion). Since it is firmly fixed in a plane parallel to the deflection surface, the resonance frequency of the side wall portion to which the optical deflector 42 is assembled is shifted to a high range, and it is difficult to pick up vibrations from other vibration sources. It has a strong structure. Furthermore, there is little possibility that the deflection surface of the plate member 1 (see FIGS. 4 and 5) that vibrates using resonance vibration described later picks up an extra vibration mode.

  The light deflecting device 42 is assembled by abutting against the side wall surface of the optical box 31. When assembling, it can be easily assembled with high accuracy using a positioning pin or the like, and the workability in the process is good and the assembly tact can be expected to be improved.

  Also, heat generated by an actuator unit 7 (see FIGS. 4 and 5), which will be described later, is efficiently radiated to the outside of the device by the light deflection device 42 being assembled from the outside of the optical box 31 and facing the outside air. For this reason, the temperature of the entire apparatus rises due to heat trapped in the optical scanning device, the optical box is deformed, the position of the lens, etc. shifts, or the characteristics of the light source device 41, the lens, etc. change due to heat. It is possible to effectively prevent the deterioration of the print image quality due to the operation.

  When these optical scanning devices are assembled, a sheet metal or resin lid member (not shown) is finally assembled from above, and the optical scanning device is substantially sealed together with the optical deflection device 42.

  The operation of the optical scanning device will be described with reference to FIG. FIG. 3 is a perspective view for explaining the operation of the optical scanning device.

  As shown in FIG. 3, the collimated light emitted from the light source device 41 is deflected and scanned by the light deflecting device 42, sequentially passes through the fθ lens 43, is reflected by the reflecting mirror 44, and is finally a photosensitive member that is a scanned object. It reaches the surface of the body drum 32 (dashed line).

  The collimated light is shaped by the fθ lens 43 so as to be scanned as a beam that is optimally narrowed within the width of the photosensitive drum 32. At the same time, a part of the scanning beam is reflected by the BD mirror 45 and is detected by the BD sensor 46, so that the BD substrate 48 synchronizes the writing signal for each scanning time based on the output signal from the BD sensor 46. . This prevents a beam writing position shift every scanning.

  In addition, the cylinder lens 47 is used to prevent the beam position deviation in the sub-scanning direction on the photosensitive drum 32 due to the tilting error of the deflecting surface of the optical deflecting device, and the beam emitted from the light source device 41 on the deflecting surface. A line image is formed by compression in the sub-scanning direction. At the same time, the deflecting surface and the surface of the photosensitive drum 32 have a conjugate relationship in the sub-scanning direction. The sub-scanning direction is a direction perpendicular to the optical axis and the beam scanning direction, and is a transfer material feeding direction.

(Light deflection device)
The configuration of the optical deflecting device 42 of the present embodiment will be described in detail with reference to FIGS. FIG. 4 is a perspective view showing the configuration of the optical deflection apparatus of the first embodiment. FIG. 5 is an exploded perspective view showing the configuration of the optical deflection apparatus of the first embodiment. FIG. 6 is an exploded perspective view of an actuator unit used in the optical deflection apparatus of the first embodiment. FIG. 7 is a perspective view of a plate member used in the light deflection apparatus of the first embodiment. These perspective views are perspective views of the light deflection device 42 as viewed from the optical box 31 side.

  As shown in FIGS. 4 and 5, the light deflection device 42 includes a plate member 1, an actuator portion 7, a holder 8 (support member), and a circuit board 9. The plate member 1 is integrally fixed to the holder 8. In the direction of the holder 8 on the fixed surface side of the plate member 1, there are an actuator part 7 for driving the movable element 2 and the movable element 3 of the plate member 1, a circuit board 9 for supplying electric power to the actuator part 7, and the like. Arranged and held fixed. The circuit board 9 is provided with a connector 10 for electrically connecting to a control circuit (not shown) provided in the image forming apparatus. Here, the circuit board 9 is fixed to the holder 8 using screws 11 (shown in FIG. 5) or the like. The circuit board 9 is outside the space surrounded by the optical box 31 and the lid member.

  As shown in FIG. 5, the actuator unit 7 is inserted into the holder 8 in the direction of arrow B, and is fixed to a hole (not shown) provided in the holder 8 by a method such as press fitting. After the actuator unit 7 is fixed to the holder 8, the plate member 1 is integrally fixed to the holder 8 from above. By adopting such a configuration, the actuator unit 7 and the plate member 1 are integrally held by a single member called the holder 8, and the configuration is strong against strong vibrations. Moreover, since it is positioned by one component, the assembling accuracy is also good.

  Next, the configuration of the actuator unit 7 will be described in detail. As shown in FIG. 6, in the actuator portion 7, a core (iron core) 12 is formed integrally with a bobbin 13 made of a resin member, and a coil (winding) 14 is wound around the core. The resin bobbin 13 is interposed between the core 12 and the coil 14 to ensure electrical insulation.

  Two pins 15 are press-fitted into the bobbin 13, and both ends of the coil 14 are entangled with these pins 15 and soldered. The two pins 15 are terminal pins and have a role of reliably taking out an electrical connection from both ends of the coil 14 to the outside of the optical deflecting device 42. Since the bobbin 13 is made of resin, it is possible to take out an electrical connection to the outside of the optical deflecting device 42 with a predetermined positional accuracy while reliably insulating these two pins 15. The pin 15 is bent into an L shape, and its tip protrudes out of the holder 8 through the hole of the holder 8. It is inserted into a hole 9a (see FIG. 5) provided in the circuit board 9, and is electrically connected to the circuit board 9 by soldering or the like. With these configurations, connection can be easily made by connector connection.

  Next, the plate member 1 will be described with reference to FIG. The plate member (element) 1 is manufactured by etching a Si single crystal wafer. The plate member 1 includes at least two movers 2 and 3. These movers 2 and 3 are supported by torsion springs 4 and 5, respectively.

  A magnet 6, which is a rod-like permanent magnet, is integrally fixed to one mover (drive element) 3. Aluminum or the like is deposited on the surface of the other mover (deflector) 2 (on the side opposite to the magnet mounting surface of the mover 3). The surface on which aluminum or the like is deposited is a reflective film suitable for reflecting a laser beam. Thus, the mover has a deflection surface that deflects and scans the laser beam that is oscillated by the resonance vibration and emitted from the light source device 41.

  As described above, in the light deflecting device 42 of the present embodiment, the plate member 1 includes the magnet 6 and is disposed at a predetermined gap from the actuator portion 7 including the core 12 and the coil 14 (see FIG. 6). . As a result, a magnetic circuit is formed, and when a predetermined current is applied to the coil 14, the movers 2 and 3 are driven to swing.

  As shown in FIG. 7, the laser beam is deflected by the surface (deflection surface) of the mover 2 as indicated by an arrow A. These at least two movers 2 and 3 have a plurality of natural vibration modes, for example, a fundamental frequency corresponding to the scanning period and a vibration mode having a frequency twice the fundamental frequency.

  The light deflecting device 42 is driven by superposing a plurality of natural frequencies (at least twice the basic frequency) of the plate member 1. This will be described with reference to FIG. FIG. 8 is a graph showing the time change of the amplitude of the optical deflecting device in the first embodiment.

  As shown in FIG. 8, when the amplitude angle of the movable element (deflector) 2 used for the deflection of the laser beam is θ and the time is t, the behavior expressed by the following formula 1 is shown.

θ (t) = A ₁ sin (ωt) + A ₂ sin (2ωt + φ) + A ₃ [Formula 1]
In Equation 1, A ₁ : amplitude at the fundamental frequency (fundamental wave), A ₂ : amplitude at twice the fundamental frequency (harmonic wave), ω: fundamental frequency, φ: phase difference between fundamental wave and harmonic wave, A ₃ : Static angle error, for example, the angle error of the posture when the deflector is not vibrating. In FIG. 8, φ = 0 and A ₃ = 0.

  Here, by appropriately setting each parameter, it is possible to approximate the following equation 2 within a certain range within one period.

θ (t) ≒ kt + α [Formula 2]
In Equation 2, k and α are both constants.

  In this range, the movable element (deflector) 2 vibrates at a substantially constant angular velocity, and the laser beam incident on the movable element (deflector) 2 is deflected and scanned at a substantially uniform angular speed.

(Arrangement of optical deflection device in optical box)
Next, the arrangement of the light deflection device 42 with respect to the optical box 31 will be described with reference to FIG. FIG. 9 is an exploded perspective view illustrating the configuration of the optical scanning device when only the optical deflecting device is disassembled from the optical box in the first embodiment.

  As shown in FIG. 9, the light deflection device 42 is configured to abut against a seating surface E that is a part of the outer wall surface of the optical box 31. The seat surface E is provided with a screw hole. A hole D is provided at the center of the portion surrounded by the seating surface E, from which a laser beam is incident on the optical deflector 42 and deflected and scanned.

  In FIG. 9, the plane formed by the four seating surfaces E is orthogonal to the scanning plane, and is a plane parallel to the plate member 1 of the light deflection device 42. Specifically, it is a plane parallel to the deflection surface in the initial stationary state of the mover 2. The geometrical tolerances such as the squareness and the parallelism are guaranteed by the molding accuracy of the optical box 31.

  Since the hole D is substantially sealed by assembling the light deflecting device 42, there is no fear that dust or the like flows from the hole D and contaminates the optical component. The seating surface E is slightly protruded from the optical box 31, but it is not always necessary to protrude. When not projecting, the gap between the light deflecting device 42 and the optical box 31 is narrowed, and the sealing performance is improved.

  The electrical connection of the light deflecting device 42 is made through the connector 10 of the circuit board 9, and the circuit board 9 is disposed at the outermost position of the optical scanning device. If the optical deflecting device is arranged inside the optical scanning device as in the prior art, the bundle path for taking out the power bundle necessary for driving the optical deflecting device out of the optical scanning device is provided in the optical box. I had to make a hole. When dust or the like flows into the inside of the apparatus through the hole and adheres to the optical system, the amount of light is reduced, and the print image quality may be reduced. On the other hand, this configuration is easy to connect. What is necessary is just to connect to the connector 10 after assembling an optical scanning device. In addition, it is not necessary to provide a wiring portion for winding the bundled wires (not shown) connected to the optical scanning device.

  The four seating surfaces F (see FIG. 5) of the holder 8 of the light deflector 42 are in contact with the seating surface E of the optical box 31 shown in FIG. 9, and the four seating surfaces F are in the same plane. . Screws (not shown) are inserted through holes provided in the seating surfaces E and F, and the light deflecting device 42 is firmly attached to the optical box 31.

  Further, the seating surface G (see FIG. 5) of the light deflecting device 42 is a surface on which the plate member 1 is assembled, and is flush with the four seating surfaces F of the light deflecting device 42. The holder 8 is a molded product made of resin or the like, and since it is easy to configure the mold so that the seating surface F and the seating surface G are in the same plane, the flatness can be easily and highly accurately guaranteed. . If the seating surface F and the seating surface G are different planes, a parallelism error between the two seating surfaces occurs. However, in this embodiment, since it is the same plane, the parallelism error between the seating surface F and the seating surface G can be prevented.

  Note that the four seating surfaces F of the holder 8 and the four seating surfaces E of the optical box 31 are not necessarily four. If there are at least three seating surfaces, one plane is determined. If there are two or less seating areas, a sufficient posture can be guaranteed.

  Further, if there are four or more seating surfaces, at least one or more seating surfaces become auxiliary seating surfaces. If it is the structure of this embodiment, the seat surface without a screw hole will be made low about 0.05-0.1. Since the plane is guaranteed with the remaining three bearing surfaces, there is no problem in reducing the height itself. The seating surface to be lowered may be either on the optical box 31 side or on the holder 8 side of the light deflection device 42.

  Conventionally, when the member to which the element is attached is a resin, if the die-cutting direction is brought in the direction of the assembly screw hole, a draft angle at the time of molding occurs on the element mounting surface, which may cause a large rotation axis collapse. It was. In addition, when the direction perpendicular to the element mounting surface is set, the screw hole portion must be slid out of the mold, and there is a problem that the cost of the dies is greatly increased due to the complicated structure of the mold. there were. On the other hand, in this configuration, the holder 8 is configured with a plane formed by the seating surface F and the seating surface G as a parting line, and the assembly direction of each member such as the actuator unit 7 and the plate member 1, that is, an arrow In this configuration, the mold is pulled out in the B direction (see FIG. 5). For this reason, it is not necessary to use expensive means such as a slide. Thus, the holder 8 has a shape that can be manufactured at low cost in terms of mold structure. This is because, as shown in the drawing, it is possible to adopt a configuration in which a hole or the like is not provided in a direction orthogonal to the arrow B direction.

  Depending on the convenience of component arrangement, the seating surface F and the seating surface G may not necessarily be arranged on the same plane, and the height between the four seating surfaces F may have to be different. In this case, although the accuracy and cost are slightly inferior, other effects can be similarly expected as long as the plate member 1 and the seating surfaces F and G are parallel to each other.

  As described above, in the present embodiment, since the light deflection device 42 is disposed on the outermost side and is assembled to the outer wall of the optical box 31, the size can be minimized and the light deflection device 42 can be minimized. Can be easily assembled from the outer wall surface. Further, since the optical box 31 is assembled to the highly accurate side wall using a positioning pin or the like, the assembly can be performed with high accuracy.

  Since the light deflecting device 42 is firmly assembled to the side wall of the optical box 31, it has a structure resistant to vibration as described above, and it is difficult to pick up a vibration mode in which the movable element 2 bows back and forth. For this reason, it is possible to reduce unevenness in scanning pitch during image formation due to extra vibration on the deflection surface.

  Further, since the mounting surface of the plate member 1 with respect to the holder 8 is the same plane as the plane of the side wall portion of the optical box 31 to which the light deflection device 42 is fixed, the parallelism tolerance is canceled and the so-called direction in which the rotation axis is tilted. It is possible to improve the accuracy of axis collapse.

  Further, since the light deflecting device 42 is assembled to the outer wall surface of the optical box 31, the power necessary for driving the light deflecting device 42 can be easily supplied from the connector facing the outside of the device. For this reason, it is not necessary to twist the bundled wires inside the optical box 31, and the structure and the assembly process can be simplified.

  In addition, there is no concern about dust inflow from the bundled wire outlet. As a result, the optical deflecting device 42 can be assembled with high accuracy and simply, so that it is possible to reduce the tact time of the process and to reduce the cost. In addition, an effect of improving the image quality of the image can be expected by reducing vibration and a stable vibration mode.

[ Reference example ]
A reference example of the present invention will be described with reference to the drawings. The same components as those in the above-described embodiment are denoted by the same reference numerals, and description thereof is omitted. FIG. 10 is a perspective view illustrating a schematic configuration of an optical scanning device according to a reference example .

As shown in FIG. 10, in this reference example , the side wall of the optical box 31 has a double structure. For example, in the vicinity of the reflection mirror 44, the inner wall portion H and the outer wall portion I are arranged in parallel, and are configured to cover the periphery of the optical box 31. An infinite number of ribs R are disposed between the inner and outer walls to increase rigidity. In the configuration of this reference example , the surrounding sidewalls are doubled, which increases the structural rigidity and is stronger against vibration.

  The arrangement of the light deflecting device 42 is not necessarily the configuration positioned at the outermost part of the optical scanning device, but the configuration is such that the periphery is covered with another wall portion, but the same effect as in the above-described embodiment is achieved. Obtainable.

The effect peculiar to this reference example is that the side wall of the optical box 31 is made double, so that the rigidity of the entire optical scanning device is improved and it is strong against deformation and the like. In addition, by completely covering the side surface with another wall portion, there is an effect that the hermeticity is improved and it is difficult to receive heat from the outside. This is particularly effective when the heat received from the outside is greater than the heat generated by the light deflector 42.

[ Second Embodiment]
A second embodiment of the present invention will be described with reference to the drawings. The same components as those in the above-described embodiment are denoted by the same reference numerals, and description thereof is omitted. FIG. 11 is a cross-sectional view of an optical box near the optical scanning device according to the second embodiment. For example, in the drawing of FIG. 1, the plate member 1 is cut in a cross section including the rotation axis of the movable element (deflector) 2 in the direction perpendicular to the scanning plane.

  As shown in FIG. 11, the laser beam is incident on the plate member 1 from the J direction and reflected in the arrow K direction. A direction perpendicular to the plate member 1 is a direction indicated by a two-dot chain line N. A laser beam indicated by an arrow K, which is deflected and scanned by a movable element (deflector) 2 provided in the plate member 1, is scanned linearly in a direction perpendicular to the paper surface.

  In the above-described embodiment, the incident beam and the outgoing beam are configured to be in the same plane (so-called scanning plane incidence), but in this configuration, the beam is incident at an angle with a direction perpendicular to the deflection surface. It is the composition to do. That is, the incident beam and the outgoing beam are not in the same plane (so-called oblique incidence).

  The effect peculiar to the present embodiment is that, for example, in the above configuration, when the optical scanning device is viewed from substantially above, the beam is incident from the resonance center direction of the light deflection device 42 (from the front when it is not resonating). Even if it makes it, it can carry out reflection deflection scanning of a beam. This is because the scanning plane can be configured to avoid the incident system by being obliquely incident in the sub-scanning direction (direction orthogonal to the scanning direction and the optical axis direction) as described above. As a result, the angle formed by the outgoing beam with respect to the incident beam at the maximum scanning angle can be minimized, and the lateral width of the movable element (deflector) 2 can be minimized. In addition, with the configuration of the present embodiment, the same effects as those of the first embodiment can be obtained.

1 is a cross-sectional view illustrating a configuration of an image forming apparatus including an optical scanning device. FIG. 3 is a perspective view illustrating a schematic configuration of the optical scanning device according to the first embodiment. The perspective view explaining operation | movement of the optical scanning device in 1st Embodiment. The perspective view which shows the structure of the optical deflection apparatus in 1st Embodiment. The disassembled perspective view which shows the structure of the optical deflection apparatus in 1st Embodiment. The disassembled perspective view of the actuator part used for the optical deflection apparatus in a 1st embodiment. The perspective view of the plate member used for the optical deflection apparatus in a 1st embodiment. The graph which shows the time change of the amplitude of the optical deflection apparatus in a 1st embodiment. The exploded perspective view explaining the composition of the optical scanning device when only the optical deflection device is disassembled from the optical box in the first embodiment. The perspective view explaining schematic structure of the optical scanning device in a reference example . Sectional drawing of the optical box of the optical scanning device vicinity in 2nd Embodiment.

  DESCRIPTION OF SYMBOLS 1 ... Plate member, 2 ... Movable element (deflector), 3 ... Movable element (driving element), 7 ... Actuator part, 8 ... Holder (support member), 9 ... Circuit board, 31 ... Optical box 41 ... Light source device, 42: Optical deflecting device, 43: fθ lens

Claims (4)

A light source that emits a laser beam;
A plate member provided with a movable element formed with a deflection surface for deflecting and scanning a laser beam emitted from the light source by oscillating by resonance vibration ;
An actuator for swinging the mover ;
A holding member for holding the plate member and the actuator unit ;
A lens through which a laser beam deflected and scanned by the deflection surface of the mover passes;
An optical box configured in a box shape by a bottom part and a side wall part surrounding the bottom part, the optical box holding the light source and the holding member and enclosing the lens;
In an optical scanning device having
The holding member is fixed to the side wall portion from the outside of the optical box,
The holding member is formed with a first seat surface that contacts the plate member and a second seat surface that contacts the side wall portion , and the second seat surface is the deflection surface in an initial stationary state of the mover. parallel der and is, the optical scanning device in which the first seating surface and the second seating surface, characterized in that the in the same plane. Said actuator unit includes a core, a winding wound around the core, and a resin member for insulating the said winding and the iron core, and two pins at both ends has been tied in the winding, the the optical scanning apparatus according to claim 1, characterized in that it comprises. A lid member covering the optical box;
The said holding member hold | maintains the circuit board electrically connected with the said actuator part, and the said circuit board is outside the space enclosed by the said optical box and the said cover member. Or the optical scanning device of 2. The optical scanning device according to claim 1, wherein the holding member is resin-molded .

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