JP6384676B2 - Optical deflector and image forming apparatus provided with the optical deflector - Google Patents

Description

  The present invention relates to an optical deflector and an image forming apparatus including the optical deflector.

  2. Description of the Related Art Conventionally, an optical deflector including a vibrating mirror unit, a pair of torsion bar units that support the vibrating mirror unit, and a piezoelectric element that swings and vibrates the vibrating mirror unit around the pair of torsion bar units is known. ing. In this type of optical deflector, there is a problem that the scanning mirror of the oscillating mirror is deformed by the inertial force at the time of oscillating and the light scanning accuracy is lowered.

  In order to solve this problem, for example, in the optical deflector disclosed in Patent Document 1, a connecting beam portion that connects the vibrating mirror portion and the torsion bar portion is provided. The connecting beam portion branches in a Y shape (bifurcated shape) from one side end portion of each torsion bar portion, and supports the vibrating mirror portion at two locations.

JP 2005-173082 A

  However, in the optical deflector shown in Patent Document 1, since the Y-shaped connecting beam portion is provided between the torsion bar portion and the vibrating mirror portion, compared to the case where the connecting beam portion is not provided, There is a problem that the dimension of the optical deflector in the direction of the oscillation axis (sub-scanning direction) increases.

  The present invention has been made in view of this point, and an object of the present invention is to suppress deformation of the oscillating mirror unit during oscillation while suppressing the size of the optical deflector in the sub-scanning direction to be small. .

An optical deflector according to the present invention includes a plate-like vibrating mirror portion having a reflecting surface portion for reflecting light, and both ends of the vibrating mirror portion in the sub-scanning direction perpendicular to the main scanning direction via connecting beam portions. A pair of connected plate-like torsion bar portions and a drive portion that swings the vibrating mirror portion around the pair of torsion bar portions to vibrate are provided.

The vibrating mirror part, the pair of torsion bar parts, and the connecting beam part have the same thickness, and are connected to each other so as to form a single plate when viewed from the side, and the reflecting surface part Is provided on both side surfaces in the thickness direction of the vibrating mirror portion, and the connecting beam portion includes a first beam portion extending in the main scanning direction and one side end portion of the first beam portion in the main scanning direction. has a second beam portion which is connected to the oscillating mirror portion, and a third beam portion of the other side end portion in the main scanning direction of the first beam portion is connected to the vibration mirror unit, the torsion bar portion, the The second beam and the three beam portions are connected to the center portion of the first beam portion in the main scanning direction, and the second beam and the three beam portions are located on the inner side of both end positions in the main scanning direction on the end surface in the sub-scanning direction of the vibration mirror portion and Are connected to predetermined connection locations that are spaced apart from each other in the direction of the main scanning direction. Each of the predetermined connection points has an edge connected in a right angle to the end face in the sub-scanning direction of the vibrating mirror section and an outer end edge in the main scanning direction inclined and connected to the end face. The dimension in the main scanning direction is set to be longer than the width dimension that is the dimension in the sub-scanning direction of the first beam portion, and the one side surface in the thickness direction of the connecting beam portion has the first beam portion and the A reinforcing rib portion extending across the second beam portion and the third beam portion is provided, and the reinforcing rib portion includes a first rib portion extending in the main scanning direction along the first beam portion, and the second rib portion. And second and third rib portions covering substantially the whole of the third beam portion, and the reinforcing rib portion is made of a piezoelectric element.

  According to the present invention, it is possible to suppress deformation of the oscillating mirror unit when it is swung while suppressing the size of the optical deflector in the sub-scanning direction to be small.

FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus including an optical deflector according to the embodiment. FIG. 2 is a plan view of the optical scanning device including the optical deflector according to the embodiment as viewed from the reflecting surface side. FIG. 3 is a plan view of the optical deflector according to the embodiment as viewed from the side opposite to the reflecting surface side. 4 is a cross-sectional view taken along line IV-IV in FIG. FIG. 5 is an enlarged view showing a V portion of FIG. 2 in an enlarged manner. FIG. 6 is an enlarged view showing the VI portion of FIG. FIG. 7 is an enlarged view showing a portion VII in FIG. 4 in an enlarged manner. FIG. 8 is a graph showing the result of calculating the deformation amount of the vibrating mirror portion by variously changing the thickness of the rib portion. FIG. 9 is a graph showing the calculation results of the deformation amount of the vibrating mirror portion when the rib portion is formed on the first beam portion and when the rib portion is formed on the vibrating mirror portion. FIG. 10 is a view corresponding to FIG. 6 showing another embodiment. FIG. 11 is a view corresponding to FIG. 6 showing another embodiment. FIG. 12 is a view corresponding to FIG. 7 showing another embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following embodiment.

Embodiment 1
FIG. 1 is a cross-sectional view showing a schematic configuration of a laser printer 1 as an image forming apparatus in the present embodiment.

  As shown in FIG. 1, the laser printer 1 includes a box-shaped printer main body 2, a manual paper feed unit 6, a cassette paper feed unit 7, an image forming unit 8, a fixing unit 9, and a paper discharge unit 10. It has. Thus, the laser printer 1 is configured to form an image on a sheet based on image data transmitted from a terminal (not shown) while conveying the sheet along the conveyance path L in the printer body 2. ing.

  The manual paper feed unit 6 includes a manual feed tray 4 that can be opened and closed on one side of the printer body 2, and a manual feed roller 5 that is rotatably provided inside the printer body 2. ing.

  The cassette paper feeding unit 7 is provided at the bottom of the printer main body 2. The cassette paper feeding unit 7 separates the paper fed one by one, a paper feeding cassette 11 that stores a plurality of papers stacked on each other, a pick roller 12 that takes out the paper in the paper feeding cassette 11 one by one, and A feed roller 13 and a retard roller 14 that are fed to the transport path L.

  The image forming unit 8 is provided above the cassette paper feeding unit 7 in the printer main body 2. The image forming unit 8 includes a photosensitive drum 16 which is an image carrier rotatably provided in the printer main body 2, a charger 17 disposed around the photosensitive drum 16, a developing unit 18, a transfer roller 19, A cleaning unit 20, an optical scanning device 30 disposed above the photosensitive drum 16, and a toner hopper 21 are provided. Thus, the image forming unit 8 forms an image on the sheet supplied from the manual sheet feeding unit 6 or the cassette sheet feeding unit 7.

  The transport path L is provided with a pair of registration rollers 15 that supply the fed paper to the image forming unit 8 at a predetermined timing after temporarily waiting.

  The fixing unit 9 is disposed on the side of the image forming unit 8. The fixing unit 9 includes a fixing roller 22 and a pressure roller 23 that are pressed against each other and rotate. Thus, the fixing unit 9 is configured to fix the toner image transferred to the sheet by the image forming unit 8 on the sheet.

  The paper discharge unit 10 is provided above the fixing unit 9. The paper discharge unit 10 includes a paper discharge tray 3, a pair of paper discharge rollers 24 for conveying paper to the paper discharge tray 3, and a plurality of conveyance guide rib portions 25 that guide the paper to the paper discharge roller pair 24. ing. The paper discharge tray 3 is formed in a concave shape at the top of the printer body 2.

  When the laser printer 1 receives the image data, the photosensitive drum 16 is rotationally driven in the image forming unit 8, and the charger 17 charges the surface of the photosensitive drum 16.

  Based on the image data, laser light is emitted from the optical scanning device 30 to the photosensitive drum 16. An electrostatic latent image is formed on the surface of the photosensitive drum 16 by irradiation with laser light. The electrostatic latent image formed on the photosensitive drum 16 is developed by the developing unit 18 to become a visible image as a toner image.

  Thereafter, the sheet passes between the transfer roller 19 and the photosensitive drum 16. At that time, the toner image on the surface of the photosensitive drum 16 is transferred to the paper and transferred by the transfer bias applied to the transfer roller 19. The sheet on which the toner image is transferred is heated and pressed by the fixing roller 22 and the pressure roller 23 in the fixing unit 9. As a result, the toner image is fixed on the paper.

  As shown in FIGS. 2 to 4, the optical scanning device 30 includes a light source 31 that emits light (shown only in FIG. 4), a deflector 40, and a housing 50 that houses the deflector 40. ing.

  The housing 50 is formed in a substantially rectangular parallelepiped shape as a whole. The casing 50 includes a bottomed casing main body 51 that opens on one side in the height direction, and a transparent lid 52 that closes the open side of the casing main body 51. The housing body 51 is made of, for example, a resin material, and the lid 52 is made of, for example, glass. The lid 52 is configured to transmit both light incident on a vibration mirror unit 41 described later from the light source 31 and light reflected on the vibration mirror unit 41.

  The deflector 40 is a so-called MEMS (Micro Electro Mechanical System) device, and is formed by etching a silicon plate.

  Specifically, as shown in FIG. 3, the deflector 40 includes an oscillating mirror portion 41, first and second torsion bar portions 42 and 43, first and second horizontal plate portions 44 and 45, and A rectangular plate-shaped fixed frame portion 46.

  The oscillating mirror unit 41 has a function of reflecting light from the light source 31 and scanning in the main scanning direction. The vibration mirror unit 41 is formed in a rectangular plate shape that is long in the main scanning direction. The oscillating mirror portion 41 is disposed substantially at the center of the fixed frame portion 46. A reflective surface portion 41a for reflecting light emitted from the light source 31 (see FIG. 4) is formed on one side surface in the thickness direction of the vibration mirror portion 41 (a surface on the near side toward the paper surface of FIG. 2). ing. The reflection surface portion 41a is composed of a light reflection film made of, for example, aluminum or chromium in order to increase the light reflectance. The oscillating mirror unit 41 oscillates by swinging around the torsion bar units 42 and 43, thereby changing the reflection direction of light incident from the light source 31 to the reflection surface unit 41a and reciprocatingly scanning light in the main scanning direction. Let The scanning light reflected by the reflecting surface portion 41 a is irradiated on the surface of the photosensitive drum 16.

  The first and second torsion bar portions 42 and 43 have a rectangular plate shape that is long in the sub-scanning direction. Both torsion bar portions 42 and 43 are arranged on an extension line (on the short axis extension line) of the swing axis A of the vibration mirror part 41 in a plan view. The first torsion bar portion 42 has one end connected to one side surface in the sub-scanning direction of the oscillating mirror 41 via a connecting beam portion 48 and the other end connected to the first horizontal plate portion 44. Yes. One end of the second torsion bar 43 is connected to the other side surface in the sub-scanning direction of the oscillating mirror 41 via a connecting beam 48, and the other end is connected to the second horizontal plate 45. Yes. Thus, the torsion bar portions 42 and 43 support the oscillating mirror portion 41 so as to be capable of swinging (vibrating) about the swing axis A.

  The first and second horizontal plate portions 44 and 45 are disposed on both sides of the vibrating mirror portion 41 in the sub-scanning direction. The first and second horizontal plate portions 44 and 45 are disposed across a pair of vertical side portions 46 a extending in the sub-scanning direction of the fixed frame portion 46. The fixed frame portion 46 is supported by a pair of pedestal portions 53 (shown only in FIG. 2) formed in the housing body portion 51.

  Two piezoelectric elements 47 (see FIGS. 2 and 4) as drive units are attached to the first horizontal plate portion 44 and the second horizontal plate portion 45, respectively. Each piezoelectric element 47 is electrically connected to a drive circuit (not shown). Then, by changing the applied voltage applied to each piezoelectric element 47 from this drive circuit at a predetermined frequency, the piezoelectric element 47 expands and contracts and vibrates.

  The torsion bars 42, 43, the pair of connecting beam portions 48, and the vibrating mirror portion 41 are integrally formed of a metal material. As shown in FIG. 5, each connecting beam portion 48 is formed in a trapezoidal frame shape that opens on the vibrating mirror portion 41 side as a whole. A rectangular opening S is formed between each connecting beam portion 48 and the vibrating mirror portion 41.

  Each connecting beam portion 48 is formed symmetrically with respect to the swing axis A in plan view. Specifically, each connecting beam portion 48 includes a first beam portion 48a, a second beam portion 48b, and a third beam portion 48c. The first beam portion 48a is formed in a rectangular plate shape extending in the main scanning direction (extending in parallel with the vibration mirror portion 41). The second beam portion 48b and the third beam portion 48c are right triangular plate portions connected to both ends in the main scanning direction of the first beam portion 48a. The second beam portion 48 b connects one end portion (left end portion in FIG. 5) of the first beam portion 48 a in the main scanning direction to one end portion of the vibrating mirror portion 41 in the main scanning direction. The third beam portion 48 c connects the other side end portion in the main scanning direction of the first beam portion 48 a (the right end portion in FIG. 5) to the other side end portion in the main scanning direction of the vibration mirror portion 41. Thus, each connecting beam portion 48 supports the vibrating mirror portion 41 at two locations separated from each other in the main scanning direction.

  As shown in FIG. 6 and FIG. 7, a thin plate-like reinforcing rib portion 49 is provided on the surface of the first beam portion 48 a of the connecting beam portion 48 opposite to the reflection surface portion 41 a. The reinforcing rib portion 49 extends over the entire main scanning direction along the first connecting beam portion 48a. The reinforcing rib portion 49 is integrally formed with the first connecting beam portion 48a. In FIG. 7, the thickness T of the reinforcing rib portion 49 is drawn larger than actual from the viewpoint of easy viewing. The thickness T of the reinforcing rib portion 49 is actually, for example, 50 μm to 100 μm.

  When the optical deflector 40 is operated, the oscillating mirror 41 resonates and swings around the torsion bar portions 42 and 43 as the piezoelectric element 47 vibrates at a predetermined resonance frequency as described above. At this time, there is a possibility that the oscillating mirror 41 is deformed by the inertial force acting on the oscillating mirror 41. This inertial force is particularly great at the part of the oscillating mirror 41 where the oscillation speed is the fastest, that is, at both ends of the oscillating mirror 41 in the main scanning direction. When the oscillating mirror 41 is deformed, there is a problem that the scanning accuracy of the reflected light is lowered.

  On the other hand, in the above-described embodiment, the connecting beam portion 48 that connects the torsion bar portions 42 and 43 and the vibrating mirror portion 41 is provided, and the vibrating mirror portion 41 is moved from the swing axis A by the connecting casing 48. It was supported at two spaced apart locations. As a result, the connection beam portion 48 can support the portion of the vibrating mirror portion 41 that is as close as possible to both ends in the main scanning direction. Therefore, each of the torsion bar portions 42, 43 acts on both ends of the oscillating mirror 41 in the main scanning direction as compared with the case where the oscillating mirror 41 is connected to the central portion of the oscillating mirror 41 in the main scanning direction. The inertial force can be reduced, and the deformation of the oscillating mirror unit 41 during the swinging can be suppressed.

  Moreover, in the above-described embodiment, the connecting beam portion 48 includes the first beam portion 48a extending in the main scanning direction, the second beam portion 48b and the third beam connecting the both end portions of the first beam portion 48a to the vibrating mirror portion 41, respectively. Part 48c, and is formed in a substantially trapezoidal frame shape as a whole. Therefore, for example, the dimension of the connecting beam portion 48 in the sub-scanning direction is reduced as compared with the case where the connecting beam portion 48 is branched in a Y shape (bifurcated shape) from one end portion of each torsion bar portion 42, 43. be able to. As a result, the size of the optical deflector 40 in the sub-scanning direction can be suppressed as much as possible.

  Furthermore, in the above embodiment, since the reinforcing rib portion 49 is provided on the first beam portion 48a, it is possible to prevent the first beam portion 48a from being deformed by an inertia force when the vibrating mirror portion 41 is swung. As a result, it is possible to suppress the deformation of the first beam portion 48a from being transmitted to the vibration mirror portion 41 and the deformation of the vibration mirror portion 41. Therefore, it is possible to suppress deformation of the oscillating mirror portion 41 during the swinging while suppressing the size of the optical deflector 40 in the sub-scanning direction.

  FIG. 8 is a graph showing the calculation results of the deformation amount of the vibrating mirror portion 41 when the thickness of the reinforcing rib portion 49 is changed to three types of 0 μm, 50 μm, and 100 μm. The horizontal axis of the graph indicates the position of the vibration mirror unit 41 in the main scanning direction, and the vertical axis indicates the amount of deformation of the vibration mirror unit 41 in the swing direction. Incidentally, 0 mm on the horizontal axis means the center position of the vibration mirror unit 41 in the main scanning direction.

  According to this graph, it can be seen that the deformation amount of the vibrating mirror portion 41 is remarkably reduced by providing the reinforcing rib portion 49 in the connecting beam portion 48.

  FIG. 9 shows the vibration when the reinforcing rib portion 49 is arranged on the surface opposite to the reflecting surface portion 41a of the vibrating mirror portion 41 and when the reinforcing rib portion 49 is arranged on the connecting beam portion 48 as in the above embodiment. It is a graph which shows the result of having calculated the deformation of the mirror part. As in FIG. 8, the horizontal axis of the graph indicates the position of the vibration mirror unit 41 in the main scanning direction, and the vertical axis of the graph indicates the amount of deformation of the vibration mirror unit 41 in the swing direction.

  According to this graph, it can be understood that the deformation amount of the vibrating mirror portion 41 can be suppressed by providing the reinforcing rib portion 49 in the connecting beam portion 48 as compared with the case where the reinforcing rib portion 49 is provided in the vibrating mirror portion 41. When the reinforcing rib portion 49 is provided in the connecting beam portion 48, the reflecting surface portions 41a can be formed on both side surfaces in the thickness direction of the vibrating mirror portion 41 as shown in FIG. Thereby, two scanning lights can be generated using one oscillating mirror unit 41. As a result, the number of the optical deflectors 40 mounted on the laser printer 1 can be reduced as much as possible to make the entire printer 1 compact.

In the above embodiment, since the reinforcing rib portion 49 is integrally formed with the connecting beam portion 48, the number of parts can be reduced and the manufacturing process can be simplified.
<< Other embodiments >>
In the above-described embodiment, the reinforcing rib portion 49 is formed integrally with the vibrating mirror portion 41, but the reinforcing rib portion 49 may be formed of a member different from the vibrating mirror portion 41.

  According to this, the processing cost of the reinforcement rib part 49 can be reduced compared with the case where the reinforcement rib part 49 is shape | molded integrally with the vibration mirror part 41 in a semiconductor process. Further, when the reinforcing rib portion 49 is formed of a separate member from the vibrating mirror portion 41, the reinforcing rib portion 49 may be formed of, for example, a piezoelectric element. Thereby, the piezoelectric element can be used also as the reinforcing rib portion 49, and the manufacturing cost of the optical deflector can be further reduced.

  In the above-described embodiment, the reinforcing rib portion 49 is provided only on the first beam portion 48a of the connecting beam portion 48. However, the present invention is not limited to this. That is, for example, as shown in FIG. 10, the reinforcing rib portion 48 includes a second beam reinforcing portion 49b that reinforces the second beam portion 48b, and a first beam reinforcing portion 49a that reinforces the first beam portion 48a. You may further provide the 3rd beam reinforcement part 49c which reinforces the three beam part 48c. In the example of FIG. 10, the second beam reinforcing portion 49b is disposed so as to cover substantially the entire second beam portion 48b in a plan view, and the third beam reinforcing portion 49c is formed on the third beam portion 48c in a plan view. It arrange | positions so that substantially the whole may be covered.

  In the above embodiment, the oscillating mirror portion 41 is formed in a rectangular shape in plan view. For example, as shown in FIG. 11, each edge of the oscillating mirror portion 41 in the main scanning direction is formed in an arc shape. May be. Further, as shown in the figure, the outer edges in the main scanning direction of the second beam part 48b and the third beam part 48c of the connecting beam part 48 are used as the edges on both sides of the vibration mirror part 41 in the main scanning direction. It may be formed in a continuous arc shape. By doing so, it is possible to smooth the air flow generated around the oscillating mirror portion 41 and to suppress the separation thereof. As a result, the air resistance during vibration of the vibration mirror unit 41 can be suppressed, and the swinging amplitude of the vibration mirror unit 41 can be stabilized.

  In the above embodiment, a laser printer has been described as an example of an image forming apparatus. However, the present invention is not limited to this, and the image forming apparatus may be, for example, a copier, a multifunction peripheral (MFP), or a facsimile. Good.

  As described above, the present invention is useful for an optical deflector and an image forming apparatus including the optical deflector.

1 Laser printer (image forming device)
40 Optical deflector 41 Vibration mirror part 42 First torsion bar part (torsion bar part)
43 Second torsion bar (torsion bar)
47 Piezoelectric element (drive unit)
48 connecting beam portion 48a first beam portion 48b second beam portion 48c third beam portion 49 reinforcing rib portion

Claims (2)

A plate-like oscillating mirror part having a reflecting surface part for reflecting light, and a pair of plate-like torsion members connected to both ends of the oscillating mirror part in the sub-scanning direction perpendicular to the main scanning direction via connecting beam parts, respectively. An optical deflector comprising: a bar portion; and a drive portion that swings and vibrates the vibrating mirror portion around the pair of torsion bar portions,
The vibrating mirror part, the pair of torsion bar parts and the connecting beam part have the same thickness and are connected to each other so as to form a single plate when viewed from the side,
The reflection surface portion is provided on both side surfaces in the thickness direction of the vibration mirror portion,
The connecting beam portion includes a first beam portion extending in the main scanning direction, a second beam portion connecting one end portion of the first beam portion in the main scanning direction to the vibrating mirror portion, and the first beam portion. A third beam portion that connects the other side end of the main scanning direction to the vibrating mirror portion,
The torsion bar portion is connected to the central portion of the first beam portion in the main scanning direction,
The second and three beam portions are connected to predetermined connection positions that are located on the inner side of both end positions in the main scanning direction on the end surface in the sub-scanning direction of the vibrating mirror portion and are spaced apart from each other in the main scanning direction. When viewed from the vertical direction, the inner edge in the main scanning direction is connected at right angles to the end surface in the sub-scanning direction of the vibrating mirror section, and the outer edge in the main scanning direction is connected to the end surface in an inclined manner. It has a right triangle shape,
The dimension in the main scanning direction of each of the predetermined connection locations is set longer than the width dimension that is the dimension in the sub-scanning direction of the first beam portion,
A reinforcing rib portion extending across the first beam portion, the second beam portion, and the third beam portion is provided on one side surface in the thickness direction of the connecting beam portion,
The reinforcing rib portion includes a first rib portion extending in the main scanning direction along the first beam portion, and second and third rib portions covering substantially the entire second and third beam portions. ,
The reinforcing rib portion is an optical deflector made of a piezoelectric element .   An image forming apparatus comprising the optical deflector according to claim 1.

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