JP2012145650A - Vibration element and optical scanner, and image forming apparatus and image projection device using these - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vibration element that solves a problem in which: a torsion bar to which a rocking body is fixed having poor straightness cannot rock the rocking body efficiently.SOLUTION: A vibration element 17 according to the present invention includes: a torsion bar 23 with one end thereof fixed to a base 20; a rocking body 22 having a light reflection surface 21 that is separated from the one end of the torsion bar 23 projecting from the base 20 and fixed to the torsion bar 23; and an element drive part 18 that rocks the rocking body 22 with the axial line in the longitudinal direction A of the torsion bar 23 as the center. The light reflection surface 21 of the rocking body 22 is orthogonal to a virtual plane that passes the attachment center O of the one end of the torsion bar 23 to the base 20, and includes an ideal rocking axial line AR extending in a straight line along the longitudinal direction of the torsion bar 23 and a center of gravity G of the rocking body. A member for correcting the position of the center of gravity 24, which is fixed to the torsion bar 23 and/or the rocking body 22, has the center of gravity thereof on the virtual plane and located closer to the ideal rocking axial line AR side than the center of gravity G of the rocking body 22.

Description

  The present invention relates to a vibration element using resonance and an optical scanning device, and an image forming apparatus and an image projection device incorporating the optical scanning device.

  Patent Document 1 discloses an optical scanning device that scans light by swinging a reflecting mirror at high speed using resonance of a vibration system instead of a rotating reflecting mirror such as a polygon mirror used in an optical scanner. Proposed in An oscillator device and a potential sensor having the same principle are also proposed in Patent Document 2.

  The vibration element that constitutes such an optical scanning device or a potential sensor includes a plate-like rocking body, a torsion bar to which the rocking body is fixed, and a drive that rocks the rocking body about the longitudinal axis of the torsion bar. Means generally. Further, the driving means has a magnet that is integrally attached to the oscillator and a coil that is opposed to the magnet and through which an alternating current is passed, and the torsion bar is elastically twisted by passing the alternating current through the coil. Along with this, the swinging body swings. For this reason, it is possible to oscillate the oscillating body with a large sway angle with relatively little electric power by utilizing the resonance phenomenon caused by the elastic torsion of the torsion bar.

  The “swing angle” described in this specification is an angle formed by two swinging ends at which the swinging direction of the swinging member is switched when the swinging member swings about the longitudinal axis of the torsion bar. Means.

JP-A-11-231251 JP 2004-301555 A

  In the optical scanning device disclosed in Patent Document 1, the resonance of the torsion bar is suppressed when the common center of gravity of the reflector and the electromagnetic coil attached back to back with the torsion bar interposed therebetween is away from the central axis of the torsion bar. End up. For this reason, a weight balancing member is attached so that the common center of gravity coincides with the central axis of the torsion bar.

  However, this weight balancing member needs to be mounted so as not to interfere with the laser beam in consideration of the incident angle and the reflection angle of the laser beam with respect to the reflecting mirror. It can be difficult. Also, when the straightness of the torsion bar is poor due to warpage or the like, even if the weight balance of the reflector or electromagnetic coil attached to the torsion bar is appropriate, the expected resonance does not occur and the deflection angle of the reflector There is also a possibility that becomes smaller than the design value.

  An object of the present invention is to provide an oscillating element and an optical scanning device capable of efficiently oscillating an oscillating body even when the straightness of a torsion bar is poor.

  Another object of the present invention is to provide a compact and high-performance image forming apparatus and an image projection apparatus incorporating such an optical scanning device.

  Another object of the present invention is to provide an oscillating element that can effectively prevent the occurrence of abnormal vibration in an oscillating body provided in a torsion bar, and an optical scanning device using the optical scanning element.

  An object of the present invention is to provide a vibrating element, an optical scanning apparatus, an image forming apparatus using the same, and an image projecting apparatus capable of widening a deflection angle range while ensuring the straightness of a desired torsion bar. is there.

  The objective of this invention is providing the vibration element which can improve the positioning accuracy of components while simplifying the assembly of a vibration element. It is also an object of the present invention to provide an optical scanning apparatus that realizes stable optical scanning, an image forming apparatus using the same, and an image projection apparatus.

  According to a first aspect of the present invention, a base, a torsion bar protruding from the base, an oscillating body provided on a side of the torsion bar opposite to the base side, and a gravity center position of the torsion bar and the oscillating body And a center of gravity position correction member for correcting the vibration element.

  According to a second aspect of the present invention, there is provided a base, a torsion bar protruding from the base, an oscillating body provided on a side of the torsion bar opposite to the base side, and a gravity center position of the torsion bar and the oscillating body An ideal oscillating axis that passes through the center of attachment of one end of the torsion bar to the base and extends in a straight line along the longitudinal direction of the torsion bar, and the torsion bar The oscillating body has a plane portion orthogonal to a virtual plane including the centroid of the oscillating body fixed to the oscillating body, and the centroid of the centroid position correcting member is within the imaginary plane and is greater than the centroid of the oscillating body. The vibration element is located on the ideal swing axis side.

  In the vibration element of the present invention, the rocking body is rocked about the longitudinal axis of the torsion bar, and the elastic torsional deformation is repeatedly given to the torsion bar. The plane portion of the oscillating body is arranged orthogonal to a virtual plane including the ideal oscillation axis of the torsion bar and the center of gravity of the oscillating body. Moreover, since the center of gravity of the center-of-gravity position correction member is within the virtual plane and is disposed closer to the ideal swing axis than the center of gravity of the swing body, the swing body swings extremely stably.

  In the resonator element according to the first aspect of the invention, it is preferable that the center-of-gravity position correcting member is attached to the surface of the torsion bar facing the ideal swing axis.

  The rocking body includes two plate members having the same size and shape that are joined to each other with the torsion bar interposed therebetween, and the center of gravity position correcting member is one plate member arranged closer to the ideal rocking axis, or one of them It may be arranged between the plate member and the torsion bar.

  The center-of-gravity position correcting member can be formed of metal, glass, resin, or a composite material thereof.

  The center-of-gravity position correction member may have a wedge shape in which the thickness dimension along the virtual plane gradually decreases toward one end of the torsion bar along the axis of the torsion bar.

  Both ends of the torsion bar may be fixed to the base, and the rocking body may be fixed to the center in the longitudinal direction of the torsion bar. Alternatively, one end of the torsion bar may be fixed to the base in a cantilever state, and the swinging body may be fixed to the other end of the torsion bar.

  According to a second aspect of the present invention, there is provided a base, a torsion bar protruding from the base, a rocking body having a light reflecting surface provided on a side opposite to the base side of the torsion bar, the torsion bar and the A center-of-gravity position correcting member that corrects the center-of-gravity position of the rocking body, a driving unit that rocks the rocking body, and a light source that irradiates light toward the light reflecting surface of the rocking body. It is in the optical scanning device.

  In the present invention, the oscillating body oscillates about the longitudinal axis of the torsion bar by the operation of the driving means, and the torsion bar undergoes repeated elastic torsional deformation. Thereby, the light from the light source is reflected and scanned by the light reflecting surface of the oscillator.

  In the optical scanning device according to the second aspect of the present invention, the driving means may have a magnet attached integrally with the oscillator, and a coil facing the magnet and through which an alternating current is passed.

  According to a third aspect of the present invention, there is provided an optical scanning device according to the second aspect of the present invention, and light from the light source of the optical scanning device is irradiated through the light reflecting surface of the oscillator of the vibration element of the optical scanning device. And an image forming medium.

  In the present invention, the light from the light source is irradiated onto the image forming medium through the light reflecting surface of the oscillating body of the oscillating element.

  According to a fourth aspect of the present invention, there is provided an optical scanning device according to the second aspect of the present invention, an optical deflection device for deflecting light from a light source reflected by the light reflecting surface of the oscillator of the optical scanning device, An image projection apparatus comprising: a screen irradiated with light deflected by the light deflection apparatus.

  In the present invention, the light from the light source is reflected by the light reflecting surface of the oscillating body of the vibrating element, and the reflected light that is in the scanning state by the oscillation of the oscillating body is reflected by the light deflector in a direction crossing the scanning direction. It is deflected and irradiated to the screen.

  According to the resonator element of the first aspect of the present invention, since the gravity center position correcting member is provided, the oscillator can be efficiently resonated.

  According to the vibration element of the second aspect of the present invention, the plane portion of the rocking body is orthogonal to the virtual plane including the ideal rocking axis and the center of gravity of the rocking body, and the center of gravity of the center of gravity position correction member is set to the center of gravity of the rocking body. Since it is positioned closer to the ideal swing axis side, the swing body can resonate efficiently.

  When the center-of-gravity position correction member is attached to the surface of the torsion bar that faces the ideal swing axis, the swing body can resonate more efficiently. The rocking body includes two plate members having the same size and shape that are joined to each other with the torsion bar interposed therebetween, and the center of gravity position correcting member is arranged as one plate member closer to the ideal rocking axis, or one of them The same applies to the case where it is disposed between the plate member and the torsion bar. Even when the thickness dimension along the imaginary plane of the gravity center position correcting member has a wedge shape in which the thickness dimension gradually decreases toward one end of the torsion bar along the axis of the torsion bar, the oscillator can resonate more efficiently.

  According to the optical scanning device of the present invention, the light reflecting surface of the oscillating body is orthogonal to the virtual plane including the ideal oscillating axis and the centroid of the oscillating body, and the centroid of the centroid position correcting member is more ideal than the centroid of the oscillating body. Since it is located on the rocking axis side, the rocking body can resonate efficiently.

  According to the image forming apparatus of the present invention, since the optical scanning apparatus according to the present invention and the image forming medium on which the light from the light source is irradiated through the light reflecting surface of the oscillating body of the vibration element, the image forming apparatus is small and high in size. A high-performance image forming apparatus can be realized.

  According to the image projection device of the present invention, the optical scanning device according to the present invention, the light deflecting device for deflecting the light from the light source along the direction parallel to the ideal swing axis, and the screen irradiated with the light deflected thereby Therefore, a small and high-performance image projector can be realized.

1 is a principle diagram of an embodiment in which an image forming apparatus according to the present invention is applied to LBP. It is a top view of one Embodiment of the vibration element in the optical scanning device by this invention integrated in LBP of FIG. It is sectional drawing along the III-III arrow in FIG. It is an expanded sectional view along the IV-IV arrow in FIG. FIG. 3 is a three-dimensional projection view showing a part of an oscillating body in the vibration element shown in FIG. It is a conceptual diagram which shows typically the relationship between the ideal rocking | fluctuation axis line of the torsion bar with a curvature, and the gravity center of a rocking body. It is a graph which represents typically the relationship between the mass of a gravity center position correction member, and the deflection angle of a rocking body. It is a partially broken front view showing the structure of the principal part in one Embodiment of the vibration element by this invention. It is sectional drawing along the IX-IX arrow in FIG. It is sectional drawing along the XX arrow in FIG. It is a partially broken front view showing the structure of the principal part in other embodiment of the vibration element by this invention. It is sectional drawing along the XII-XII arrow in FIG. It is a partially broken front view showing the structure of the principal part in other embodiment of a vibration element. It is sectional drawing along the XIV-XIV arrow in FIG. FIG. 15 is a stereoscopic projection diagram showing the embodiment shown in FIGS. 13 and 14 in an exploded state. It is a partially broken front view showing the structure of the principal part in another embodiment of a vibration element. FIG. 17 is a stereoscopic projection diagram showing the embodiment shown in FIG. 16 in an exploded state. It is a graph showing the relationship between the maximum amplitude of the rocking | swiveling body which comprises a vibration element, and the curvature amount of the torsion bar which comprises this vibration element. It is a top view of the principal part in other embodiment of a vibration element. FIG. 20 is a right side view of the embodiment shown in FIG. 19. It is a top view of the principal part in another embodiment of a vibration element. It is a right view of embodiment shown in FIG. FIG. 27 is a three-dimensional projection diagram schematically illustrating a manufacturing procedure of the vibration element illustrated in FIGS. 19 and 20 together with FIGS. 24 to 26. FIG. 27 is a three-dimensional projection diagram schematically illustrating a manufacturing procedure of the vibration element illustrated in FIGS. 19 and 20 together with FIGS. 23, 25, and 26. FIG. 27 is a three-dimensional projection diagram schematically illustrating a manufacturing procedure of the resonator element illustrated in FIGS. 19 and 20 together with FIGS. 23, 24, and 26. FIG. 26 is a three-dimensional projection diagram schematically illustrating a manufacturing procedure of the vibration element illustrated in FIGS. 19 and 20 together with FIGS. 23 to 25. It is a partially broken front view showing the structure of the principal part in different embodiment of a vibration element. It is a partially broken front view showing the structure of the principal part in other embodiment from which a vibration element differs. It is a partially broken front view showing the structure of the principal part in another embodiment from which a vibration element differs. 1 is a principle diagram of an embodiment of an image projection apparatus according to the present invention.

  An embodiment in which an image forming apparatus according to the present invention is applied to a laser beam printer (hereinafter referred to as LBP) will be described in detail below with reference to FIGS. However, the present invention is not limited to such an embodiment, and the configurations of different embodiments may be further combined as necessary, or any other configuration belonging to the spirit of the present invention described in the claims. Note that it can be adopted as appropriate.

  The exposure part of LBP in this embodiment is schematically shown in FIG. 1, the main part of the vibration element in the optical scanning device is extracted and shown in FIG. 2, and the cross-sectional shape along the line III-III is shown in FIG. FIG. 4 shows an enlarged cross-sectional shape along the line IV-IV in FIG. That is, the LBP 10 of this embodiment includes a photosensitive drum 11 as an image forming medium in the present invention, and an exposure unit 12 for forming an electrostatic latent image corresponding to image information on the photosensitive drum 11. In addition to the photosensitive drum 11 and the exposure unit 12, the LBP 10 of the present embodiment includes a well-known paper feeding unit, charging unit, toner supply unit, transfer unit, fixing unit, and paper transport unit (none of which are shown). I have.

  The exposure unit 12 includes an optical scanning device 14 including a laser light source 13 for oscillating a pulsed laser beam L corresponding to image information, a known collimating optical system 15 and an fθ lens 16.

  The optical scanning device 14 includes the previous laser light source 13, a vibrating element 17 for scanning the laser light L from the laser light source 13, an element driving unit 18 that drives the vibrating element 17, and the element driving unit 18. And a control device 19 for controlling the operation of.

  The vibration element 17 includes a base 20, a rocking body 22 on which a light reflecting surface 21 on which the laser light L from the laser light source 13 is incident, a torsion bar 23 that holds the rocking body 22, and a gravity center position correction member 24. And a cover member 25. The base 20 in the present embodiment is mounted with a substrate 27 provided with a spirally formed sheet coil 26 that constitutes a part of the element driving unit 18 as the driving means in the present invention. A frame body 28 constituting the outer peripheral edge portion of the base 20 is overlapped with the peripheral edge portion of the substrate 27, and these are integrally joined. An optically transparent cover member 25 is superimposed on the frame body 28, and the internal space S formed by integrally joining them is kept airtight in a reduced pressure state. In the internal space S surrounded by the base 20 and the cover member 25, a torsion bar 23 having a round bar shape, an oscillating body 22, a center-of-gravity position correcting member 24, and a previous sheet which is a part of the element driving unit 18. A substrate 27 on which the coil 26 is formed is accommodated. Thus, by holding the internal space S airtight in a reduced pressure state by the cover member 25, the characteristics of the vibration system mainly composed of the oscillating body 22 can be further enhanced as compared with that under normal pressure. In particular, as a result of reducing the influence of air resistance, the vibration characteristics can be further improved.

The torsion bar 23 that holds the oscillating body 22 is an axis orthogonal to the rotational axis of the photosensitive drum 11 (hereinafter referred to as an ideal oscillating axis, but in the illustrated example, an axis perpendicular to the paper surface of FIG. in a) extending along the a _R. The base end of the torsion bar 23 is fixed between the frame body 28 and the cover member 25 of the base 20 in a cantilever state, and the distal end is a central portion of the sheet coil 26 formed on the substrate 27 from the frame body 28. It protrudes to the nearest. The oscillating body 22 fixed to the end of the torsion bar 23 can oscillate with the torsion bar 23 being elastically twisted around the longitudinal axis of the torsion bar 23.

The oscillating body 22 in the present embodiment includes two rectangular plate members 29 and 30 having the same size and shape that are joined to each other with the torsion bar 23 interposed therebetween. The joint surfaces 29a, 30a of the two plate members 29, 30 are set in parallel to the longitudinal axis A of the torsion bar 23, and are torsionally parallel to the surface of the sheet coil 26 formed on the substrate 27. It is joined to the bar 23. Accordingly, the surface of one plate member 29 facing the cover member 25 side is a light reflecting surface 21, and this light reflecting surface 21 is formed by vapor-depositing aluminum, gold or the like on the surface of one plate member 29. be able to. Alternatively, a plate-like member that has been mirror-finished in advance may be attached to the surface of one plate member 29 and used as the light reflecting surface 21. The light reflecting surface 21, with respect to a virtual plane including the ideal pivot axis A _R extending in a straight line along the longitudinal direction of the torsion bar 23, the center of gravity G of the fixed to the torsion bar 23 the oscillator 22 In an orthogonal state. In this case, the ideal pivot axis A _R passes through the mounting center O of the proximal end of the torsion bar 23 relative to the base 20, the previous virtual plane becomes a plane parallel to the plane of FIG. 3 and FIG.

  Further, a magnet 31 having a round bar shape constituting a part of the element driving unit 18 is embedded in the oscillator 22. In the present embodiment, a hole 32 into which a round bar-like magnet 31 is inserted is formed along the direction orthogonal to the longitudinal direction of the torsion bar 23 at the end portion of the torsion bar 23, and the magnet 31 is inserted therein. It is in the state. The direction of the magnet 31 is defined so that the pair of magnetic poles of the magnet 31 are arranged in a direction orthogonal to the longitudinal axis A of the torsion bar 23.

  Torsion bar housing grooves 29b and 30b for inserting the torsion bar 23 in advance and magnet housing for housing the magnet 31 on the joint surfaces 29a and 30a of the two plate members 29 and 30 constituting the rocking body 22 are provided. Grooves 29c and 30c are formed. These two grooves 29b, 30b, 29c, and 30c each have a semicircular cross section, and are orthogonal to each other at the center of the joint surfaces 29a and 30a.

By the way, in the elongated torsion bar 23 as described above, it is general that a slight amount of essential warp due to processing alteration occurs. Such two-dimensional warping of the torsion bar 23 is accompanied by abnormal vibration of the oscillating body 22 and results in the effect that the deflection angle α of the light reflecting surface 21 becomes small with respect to the input energy. That is, when the center of gravity G of the fixed to the torsion bar 23 with a warped oscillator 22 does not match with respect to the previous ideal pivot axis A _R, occurs abnormal vibration of the oscillator 22. As a result, since the light reflecting surface 21 of the oscillating body 22 is oscillated at a desired deflection angle α, it is necessary to supply more current to the sheet coil 26.

  FIG. 5 exaggerates the degree of warping of such a torsion bar 23. The base end of the torsion bar 23 is pressed against the surface of the glass surface plate 33, the torsion bar 23 is rolled on the glass surface plate 33 around this portion, and the height from the surface of the glass surface plate 33 to the center of gravity G of the oscillator 22 is increased. Find the position where h is the maximum. It is also possible to obtain the height from the surface of the glass surface plate 33 to the end of the torsion bar 23 instead of the height h. In this state, the surface of one plate member 29 serving as the light reflecting surface 21 faces upward, and the surface of the other plate member 30 faces the surface of the glass surface plate 33 so as to face the torsion bar 23. A moving body 22 is attached. In this state, the direction of the magnetic pole of the magnet 31 is parallel to the surface of the glass surface plate 33 and perpendicular to the longitudinal axis A of the torsion bar 23. The direction of is also defined.

In the present invention, as the center of gravity of the vibration system is matched with respect to the ideal pivot axis A _R of the torsion bar 23, the center-of-gravity position correcting member 24 is mounted on the oscillator 22 and / or the torsion bar 23. More specifically, so that the center of gravity of the center of gravity position correcting member 24 is positioned in the ideal pivot axis A _R side than the center of gravity G of the be in the above imaginary plane rocking body 22, 27 side substrate in the present embodiment The center-of-gravity position correcting member 24 is joined to the surface of the other plate member 30 facing the direction. That is, the center-of-gravity position correcting member 24 is attached to the surface of the torsion bar 23 warped to the convex side, that is, the surface of the other plate member 30 in this embodiment. The center-of-gravity position correcting member 24, rocking body 22, magnet 31, the common center of gravity of the vibration system including the center of gravity position correcting member 24 has a mass such that the final match the ideal pivot axis A _R Is desirable. Thus, the light reflecting surface 21 of the oscillator 22, so that the swings about efficiently ideal pivot axis A _R with respect to the input energy. It is also possible to arrange between the one plate member 29, 30 and the torsion bar 23 which is arranged a center of gravity position correcting member 24 closer to the ideal pivot axis A _R.

The element driving unit 18 in the present embodiment includes a magnet 31 fixed to the oscillator 22 and / or the torsion bar 23, a sheet coil 26 provided on the base 20 side so as to face the magnet 31 with a gap therebetween, And a power supply (not shown). An alternating current corresponding to the resonance frequency of the vibration system composed of the torsion bar 23, the rocking body 22, the magnet 31, and the gravity center position correcting member 24 is applied to the sheet coil 26 from the power source of the element driving unit 18. Thus, swinging the ideal pivot axis A _R around the light reflecting surface 21 of the oscillator 22 at the resonance frequency of the vibration system, i.e. it can be whirling in a resonant state. Therefore, the amplitude of this vibration system, that is, the magnitude of the deflection angle α of the light reflecting surface 21 of the oscillator 22 can be adjusted by the amount of current applied to the sheet coil 26. The waveform of the alternating current may be a triangular wave or a pulse output in addition to the sine wave. It is also possible to use a coil containing a soft magnetic material serving as a yoke instead of the sheet coil 26 as described above. It is also possible to provide a pair of magnetic field applying means arranged so as to sandwich the oscillating body 22 within a range that does not interfere with the light reflecting surface 21 of the oscillating body 22.

  Here, FIG. 7 shows the relationship between the mass of the center-of-gravity position correcting member 24 and the deflection angle α of the light reflecting surface 21 of the oscillator 22. This is a rocking body when a constant alternating current is passed through the sheet coil 26 with respect to the torsion bar 23 having a length of 32 mm and a rectangular cross section of 0.35 × 0.15 mm and having a warp of 50 μm in FIG. 22 shows a change in the deflection angle α of the 22 light reflecting surfaces 21. The two plate members 29 and 30 used here each have a thickness of 0.1 mm, have a rectangular surface of 2.8 × 1.4 mm, and incorporate a magnet 31 having a length of 3 ·. The center of gravity position correcting member 24 having a different weight is joined to the surface of the other plate member 30. As is apparent from FIG. 7, in this case, it can be confirmed that the deflection angle α is maximized when the gravity center position correcting member 24 having a weight of about 3 mg is joined. Therefore, even if the position of the center of gravity G of the oscillating body 22 is unknown, as long as the direction of warping of the torsion bar 23 can be recognized, the optimum center of gravity position correcting member 24 that maximizes the deflection angle α of the oscillating body 22 is selected. Is possible. That is, the center-of-gravity position correcting member 24 having a different mass may be attached to the warped convex surface of the torsion bar 23 to measure the deflection angle α of the oscillator 22. The cross-sectional shape orthogonal to the longitudinal axis A of the torsion bar 23 is not limited to a circle, and any cross-sectional shape such as a rectangular cross-section as described with reference to FIG. 7 can be adopted.

  The control device 19 controls the output of the element drive unit 18 by receiving a pair of BD sensors 34 arranged close to both ends in the longitudinal direction of the photosensitive drum 11 and detection signals from the pair of BD sensors 34. Part 35. The control unit 35 is based on detection signals from the pair of BD sensors 34 so that the deflection angle α of the light reflecting surface 21 due to the swinging of the swinging body 22 of the vibrating element 17 is within a predetermined range on the surface of the photosensitive drum 11. The output of the element driving unit 18 is feedback controlled.

Accordingly, the pulsed laser light L emitted from the laser light source 13 according to the image signal is incident on the light reflecting surface 21 of the oscillating body 22 of the vibrating element 17 through the collimating optical system 15. The light is reflected and applied to the surface of the photosensitive drum 11 through the fθ lens 16. In this case, by the light reflecting surface 21 of the oscillator 22 of the resonator element 17 oscillates to the ideal pivot axis A _R direction by the resonance of the torsion bar 23, the laser beam L is rotated parallel to the axis direction of the photosensitive drum 11 Scanned. Further, image information, that is, an electrostatic latent image is formed on the surface of the photosensitive drum 11 along the rotation direction of the photosensitive drum 11 by the rotation of the photosensitive drum 11.

  As a material constituting the torsion bar 23, for example, work-hardening and age-hardening type cobalt (Co) -nickel (Ni) based alloys subjected to work hardening and age hardening are suitable. The Co—Ni based alloy referred to here is an alloy containing Co and Ni. Preferably, chromium (Cr), which lowers stacking fault energy, and molybdenum (Mo), iron (Fe) as solute elements that contribute to improvement of aging and work hardening ability by fixing dislocations by solid solution strengthening of the matrix and segregation. ) Etc. More specifically, a Co—Ni—Cr—Mo alloy, a Co—Ni—Fe—Cr alloy, and the like can be exemplified. These alloys can further include niobium (Nb), manganese (Mn), tungsten (W), titanium (Ti), boron (B), magnesium (Mg), carbon (C), and the like. Nb functions like Mo and iron as solute elements, Mn has the function of stabilizing the face-centered cubic lattice phase and lowering stacking fault energy, and W strengthens the matrix and lowers stacking fault energy. Contribute to. Ti contributes to refinement of the ingot structure and strength improvement, B and Mg improve thermal workability, C dissolves in the matrix and forms carbides with Cr, Mo, Nb, etc. Demonstrate the function to strengthen the world. When the above Co—Ni—Cr—Mo alloy is used, the weight ratio of the main composition is Co: 20.0 to 50.0%, Ni: 20.0 to 45.0%, Cr / Mo: 20. It is preferably 0 to 40.0% (Cr: 18 to 26%, Mo: 3 to 11%). In particular, Co: 31.0 to 37.3%, Ni: 31.4 to 33.4%, Cr: 19.5 to 20.5%, Mo: 9.5 to 10.5% preferable.

  More specifically, work hardening by cold rolling is performed from a starting material containing a substitutional solute element in a matrix containing at least Co and Ni obtained through processes such as hot forging and homogenization heat treatment after melting. Through the treatment, a Co—Ni—Cr—Mo alloy material is obtained. This alloy material usually has a <100> texture in the rolling direction and a <110> texture in a direction perpendicular to the rolling direction. For this reason, when using as the torsion bar 23 of this embodiment, it cuts out so that the direction orthogonal to a rolling direction may become the longitudinal direction of the torsion bar 23 by press processing, laser processing, wire cutting processing, etc. Alternatively, a desired torsion bar 23 is formed by processing into a product shape by superplastic processing, applying a curing process along with these processes to give an internal residual strain, and then performing an age hardening process in a vacuum or in a reducing atmosphere. Can be obtained. The age hardening treatment is optimally performed at a temperature of 400 ° C. to 700 ° C. for several tens of minutes to several hours (for example, 550 ° C. for 2 hours). In order to shorten the processing time, for example, in a strong magnetic field. It is also effective to use heat treatment.

  As a result, it is possible to obtain a torsion bar 23 having good vibration characteristics with high strength, low vibration damping capability, and high elastic limit. As an example of such a non-magnetic, work-hardening and age-hardening type Co—Ni—Cr—Mo alloy, there can be mentioned SPRON 510 (trade name: SPRON is a registered trademark) of Seiko Instruments Inc. This SPRON 510 has a composition of Co: 35%, Ni: 32%, Cr: 20%, Mo: 10%.

  In this way, the torsion bar 23 having a sharp resonance frequency and a characteristic in which the vibration is line symmetric with respect to the resonance frequency, that is, a high Q value (for example, 1000 or more) and a very small non-linearity of the spring characteristic is obtained. be able to. Such a torsion bar 23 does not become unstable even when the maximum strain due to vibration deformation increases to about 3 × 10 −3 mm, and the vibration element 17 with low power consumption can be realized. Therefore, the LBP 10 according to the present embodiment can be reduced in size while ensuring desired fatigue characteristics and vibration characteristics, and can be stably scanned with the laser beam L while reducing instabilities such as jitter. High-precision control is possible.

  In the present embodiment, the torsion bar 23 is formed of a non-magnetic Co—Ni-based alloy, but this uses a magnet 31 and an alternating magnetic field as means for swinging the rocking body 22 together with the torsion bar 23. This is because stable driving can be realized. Therefore, when a means other than an alternating magnetic field, such as a piezoelectric element, is used as the element driving unit 18, a general spring material other than a nonmagnetic metal can be used as the material of the torsion bar 23. More specifically, stainless steel such as SUS301, 302, 304, 316, 631, 632, spring steel (SUP), piano wire (SWP), oil tempered wire (SWO) of spring carbon steel can be employed. . In addition, silicon chrome steel oil tempered wire (SWOSC), spring beryllium copper alloys (C1700, C1720), spring titanium copper alloys (C1990), spring phosphor bronze (C5210), spring white (C7701) ) Etc. can also be adopted.

  Further, the magnet 31 attached to the torsion bar 23 together with the oscillator 22 is preferably as small and light as possible and has a high coercive force, and an Nd—Fe—B or Sm—Co rare earth magnet is suitable. . However, Alnico magnet, Fe-Co-V alloy magnet, Cu-Ni-Fe alloy magnet, Cu-Ni-Co alloy magnet, Fe-Cr-Co magnet, Pt-Co magnet, hard ferrite (Ba ferrite and Sr ferrite) A sintered magnet such as can be employed. In addition, it may be a thin film magnet formed by a bond magnet or a sputtering method, and is not particularly limited by a material, a manufacturing method or a shape.

  Non-magnetic materials such as alumina, zirconia, beryllium, silicon nitride, aluminum nitride, sapphire, silicon carbide, silicon dioxide, glass, and resin are used as materials for the two plate members 29 and 30 constituting the oscillator 22. Can be used. Further, these surfaces can be used as the light reflecting surface 21 by making them into mirror surfaces.

  Further, the material constituting the barycentric position correcting member 24 may be the same as the material constituting the oscillator 22, but it is naturally possible to use a different material.

  The configuration of the main part of the vibration element 17 shown in FIGS. 2 to 5 can be changed as shown in FIGS. 8 to 12 as necessary. That is, the front shape of the main part of another embodiment of the vibration element 17 of the present invention is partly broken and shown in FIG. 8, the cross-sectional shape along the IX-IX arrow is shown in FIG. FIG. 10 shows an enlarged cross-sectional shape along the arrow XX. Moreover, the front shape of the principal part of another embodiment of the vibration element 17 of the present invention is partly broken and shown in FIG. 11, and the cross-sectional shape along the XII-XII arrow is shown in FIG.

  In the embodiment shown in FIG. 8 to FIG. 10, a truncated cone-shaped stopper portion 36 is formed at the tip of the torsion bar 23, which serves as both prevention of detachment and positioning. The magnet 31 is formed integrally with the oscillating body 22 so as to face the stopper portion 36, and one end face thereof facing the stopper portion 36 is exposed to the outside from the oscillating body 22. Although the magnet 31 in this embodiment has a split structure so as to sandwich the torsion bar 23, it can be a single magnet 31 in which a hole 32 through which the torsion bar 23 passes is formed in advance. The center-of-gravity position correcting member 24 has a wedge shape in which the thickness gradually decreases toward the proximal end along the longitudinal axis A of the torsion bar 23.

  In the embodiment shown in FIGS. 11 and 12, the stopper portion 36 in the above embodiment is embedded in the rocking body 22, and the relative position of the rocking body 22 with respect to the torsion bar 23 can be reliably defined. . In the present embodiment, the magnet 31 is also used as the gravity center position correcting member 24. That is, a notch portion 37 is formed on the surface along the convex side of the torsion bar 23, the magnet 31 is inserted therein, and in this state, the two plate members 29 and 30 are overlapped to form the stopper portion 36 and the magnet 31. Is sandwiched between the plate members 29 and 30. This structure is particularly suitable when the oscillating body 22 is injection-molded with resin, and the magnet 31 and the tip of the torsion bar 23 can be integrally joined.

  The configuration of the main part of the vibration element 17 shown in FIGS. 2 to 5 can be further changed as shown in FIGS. 13 to 17 as necessary. That is, the front shape of the main part of another embodiment of the vibration element 17 of the present invention is partly broken and shown in FIG. 13, the cross-sectional shape along the XIV-XIV arrow is shown in FIG. Is shown in a disassembled state in FIG. Further, the front shape of the main part of another embodiment of the vibration element 17 of the present invention is partly broken and shown in FIG. 16, and its appearance is shown in an exploded state in FIG.

  In the embodiment shown in FIG. 13 to FIG. 15, a truncated cone-shaped stopper portion 36 that serves both for preventing slipping and positioning is formed at the tip of the torsion bar 23. The magnet 31 having a rectangular bar shape is formed integrally with the rocking body 22 so as to face the stopper portion 36, and one end face thereof facing the stopper portion 36 is exposed to the outside from the rocking body 22. Although the magnet 31 in the present embodiment has a split structure so as to sandwich the torsion bar 23, a single magnet 31 in which a hole 31a through which the torsion bar 23 penetrates may be formed in advance.

  The oscillating body 22 in this embodiment includes two rectangular plate members 29 and 30 having the same shape (specifically, the same size and shape) that are joined to each other with the torsion bar 23 interposed therebetween. The members 29 and 30 have a symmetrical shape with the longitudinal axis A of the torsion bar 23 as the axis of symmetry. The joint surfaces 29a, 30a of the two plate members 29, 30 are set in parallel to the longitudinal axis A of the torsion bar 23, and are torsionally parallel to the surface of the sheet coil 26 formed on the substrate 27. It is joined to the bar 23. Therefore, for example, the surface of one plate member 29 facing the cover member 25 side is a light reflecting surface 21, and this light reflecting surface 21 is formed by depositing aluminum, gold or the like on the surface of one plate member 29. Can be formed. Alternatively, a plate-like member that has been mirror-finished in advance may be attached to the surface of one plate member 29 and used as the light reflecting surface 21. The surface of the other plate member 30 is also subjected to the same processing as the surface of the one plate member 29, so that the weight balance between the two plate members 29 and 30 can be matched. More stable vibration can be brought about with respect to the vibration system. In addition, by performing the same processing on the surfaces of both plate members 29 and 30, one of the two plate members 29 and 30 having better flatness can be selected as the light reflecting surface 21. . Alternatively, the surfaces of the two plate members 29 and 30 can be used as independent light reflecting surfaces. The light reflecting surface 21 is relative to a virtual plane including a longitudinal axis A of the torsion bar extending in a straight line along the longitudinal direction of the torsion bar 23 and the center of gravity G of the rocking body 22 fixed to the torsion bar 23. In an orthogonal state. Therefore, this virtual plane is a plane parallel to the paper surface of FIG.

  Next, a SPRON 510 wire rod having a diameter of 240 μm is used as the torsion bar 23, and a Si wafer having a thickness of 300 μm is cut into a 1 mm × 3 mm rectangle with a dicer as the plate members 29 and 30. The vibration characteristics were evaluated as follows. The flatness of the surfaces of the plate members 29 and 30 is 20 to 30 nm. The flatness of the plate members 29 and 30 is determined by the PV value (maximum measured value−minimum) obtained using a surface roughness meter manufactured by ZYGO. (Measurement value).

  Torsion bar housing grooves 29b and 30b and magnet housing grooves 29c and 30c are formed on the joining surfaces 29a and 30a of the plate members 29 and 30 thus obtained, respectively. The width and depth of the torsion bar receiving grooves 29b and 30b are 120 μm because the diameter of the torsion bar 23 is 240 μm, but the grooves 29b and 30b do not have to be semicircular, but have a rectangular cross section. It may be a groove. By applying such groove processing to the joining surfaces 29a and 30a of the plate members 29 and 30, the surfaces of the plate members 29 and 30, that is, the surfaces opposite to the joining surfaces 29a and 30a are deformed into a concave shape. As a result, the PV value becomes 70 to 80 nm. However, when the torsion bar 23 is accommodated in the torsion bar accommodating grooves 29b and 30b, the joining surfaces 29a and 30a of the two plate members 29 and 30 are overlapped and joined with an adhesive or the like, thereby deforming due to the groove processing. Will be corrected. As a result, the flatness of the light reflecting surface 21 is improved to 50 to 60 nm. In this state, the two plate members 29 and 30 have a symmetrical shape with the longitudinal axis A of the torsion bar 23 as the axis of symmetry, and their center of gravity G is located on the longitudinal axis A of the torsion bar 23. For this reason, the rocking body 22 can be stably resonated around the longitudinal axis A of the torsion bar 23.

  As a comparison, Si wafers with thicknesses of 200 μm and 525 μm were cut into 1 mm × 3 mm rectangles with a dicer to prepare two plate members having different thicknesses. The flatness of these two plate members is 20 to 30 nm. Next, a rectangular torsion bar accommodating groove having a width and a depth of 240 μm was formed only on the joint surface of the plate member having a thickness of 525 μm. As a result, it was confirmed that the surface opposite to the joint surface of the plate member having a thickness of 525 μm was deformed into a concave shape, and the flatness was reduced to 70 to 80 nm. And the result of having measured the flatness of the light reflection surface of the obtained rocking | swiveling body in the state which accommodated the torsion bar 23 in the torsion bar accommodation groove, and joined the bonding surface of the two plate members with an adhesive. It was found that the PV value decreased to 70 to 80 nm. The flatness of the surface of the plate member having a wall thickness of 525 μm was hardly improved even by bonding the plate member having a wall thickness of 200 μm, and the PV value remained approximately 70 to 80 nm before bonding. . The reason is considered that the plate member having a thickness of 525 μm has higher absolute rigidity than the plate member having a thickness of 200 μm.

  The scanning locus of the laser beam L formed on the surface of the photosensitive drum 11 should originally draw a single straight line parallel to the rotational axis of the photosensitive drum 11. However, due to the warpage of the torsion bar 23 and the displacement of the center of gravity G of the oscillator 22 with respect to the longitudinal axis A thereof, high-order complex vibration modes are generated, and abnormal scanning such as waveform waviness, figure 8 or circle is detected. There is a case where a locus is drawn. Therefore, the length of the torsion bar 23 was first adjusted so that the resonance frequency of the oscillator 22 was 2 kHz. Furthermore, the supply value of the alternating current was adjusted so that the deflection angle α would be ± 10 degrees, ± 17 degrees, ± 25 degrees, ± 32 degrees, ± 38 degrees, ± 45 degrees, and ± 50 degrees. Then, as a result of obtaining the scanning trajectory of the laser beam L formed on the surface of the photosensitive drum 11 in this case, it can be confirmed that no abnormal vibration occurs at all the deflection angles α and a stable scanning trajectory is drawn. did it.

  In the embodiment shown in FIGS. 16 and 17, the stopper portion 36 in the above embodiment is embedded in the rocking body 22, and the relative position of the rocking body 22 with respect to the torsion bar 23 can be more reliably defined. it can. In the present embodiment, the notch 37 that communicates with the magnet receiving grooves 29c, 30c formed in the two plate members 29, 30 is provided as a stopper so that the magnet 31 can cross the stopper 36 of the torsion bar 23. A portion 36 is formed. Therefore, it becomes possible to join the tip of the magnet 31 and the torsion bar 23 and the rocking body 22 more firmly.

  According to the vibration element of the present invention, the oscillating body has two plate members having the same shape, and these two plate members are joined to each other with the torsion bar interposed therebetween, so that abnormal oscillation occurs in the oscillating body. Can be effectively prevented.

  In addition, when the rocking body includes two plate members in which a receiving groove for receiving the torsion bar is formed on the joint surface, and these have a symmetrical shape with the longitudinal axis of the torsion bar as an axis of symmetry, On the other hand, the oscillator can be fixed accurately. Further, it is possible to improve the flatness of the light reflecting surface which is lowered by processing of the housing groove formed on the joining surface of the two plate members. Furthermore, the rocking body can be efficiently rocked without causing abnormal vibration.

  When the light reflecting surface of the oscillating body is formed on the surface opposite to the joint surface of at least one plate member of the two plate members, the one having better flatness can be used as the light reflecting surface.

  According to the optical scanning device of the present invention, since the optical scanning element according to the present invention is provided, the oscillator can be efficiently resonated.

  In addition, when the groove for accommodating or holding the magnet of the driving means is formed symmetrically with the longitudinal axis of the torsion bar as the symmetry axis on the joint surface of the two plate members, the position of the center of gravity of the oscillator including the magnet is determined. It can be located on the longitudinal axis of the torsion bar. Moreover, the positioning of the magnet can be performed accurately, and deterioration caused by exposing the magnet to the atmosphere can be suppressed. In particular, when the magnetic pole of the magnet extends in a direction perpendicular to the longitudinal axis of the torsion bar and parallel to the light reflecting surface of the rocking body, the amount of vibration from the unloaded state to one side of the rocking body and the other The amount of deflection to the side can be made uniform.

  According to the image forming apparatus of the present invention, the optical scanning apparatus of the present invention and the image formation in which the light from the light source of the optical scanning apparatus is irradiated through the light reflecting surface of the oscillator of the optical scanning element of the optical scanning apparatus. Therefore, a small and high-performance image forming apparatus can be realized.

  According to the image projection device of the present invention, the optical scanning device of the present invention and the light deflection device for deflecting the light from the light source along the direction parallel to the longitudinal axis of the torsion bar and irradiating the screen are provided. Therefore, a small and high-performance image projector can be realized.

  Here, the influence of the warpage in the torsion bar 23 on the deflection angle α of the light reflecting surface 21 of the rocking body 22 supported by the torsion bar 23 will be considered.

  As shown in FIG. 6, the base end of the torsion bar 23 is pressed against the surface of the glass surface plate 33, and the torsion bar 23 is rolled on the glass surface plate 33 around this portion. At this time, the amount of warpage at the position where the height h from the glass surface plate 33 of the end of the torsion bar 23, more precisely, the center of gravity of the rocking body 22 is maximized is measured as straightness. A torsion bar 23 having a warp amount of 0 μm, 50 μm, and 100 μm was prepared as a sample, and a rocking body 22 attached to the end was rocked at a resonance frequency of 2 kHz.

  The method of measuring the swing angle of the swinging body 22 is to change the value of the current flowing through the sheet coil 26 so that the light reflecting surface 21 of the swinging body 22, that is, the swing angle α of the reflected laser light L is stepped. Changed to be larger. The laser beam L reflected from the light reflecting surface 21 should draw a scanning line as one straight line that scans on the photosensitive drum 11, but when the deflection angle increases, an abnormality such as a curve, a figure of 8 or a circle is formed. A state of drawing a simple scanning line. When such a state occurs while the deflection angle α is gradually increased, it is determined that abnormal vibration has occurred. In this case, the swing angle is changed by further dividing the swing angle at the stage where the abnormal vibration has occurred and the swing angle at the previous stage, and the largest swing angle at which the abnormal vibration does not occur is set as the maximum swing angle. Stipulated.

  The measurement results are shown in FIG. As is apparent from FIG. 18, the maximum deflection angle in the case of the torsion bar 23 having a warp amount of 0 μm is ± 45 to ± 50 degrees, in the case of 50 μm is ± 25 to ± 39 degrees, and in the case of 100 μm is ± 17. It was ~ ± 25 degrees. From this, it is understood that the maximum deflection angle when the warp is 50 μm and when the warp is 100 μm is reduced by about 30% and 60%, respectively, compared with the case of 0 μm where there is no warp of the torsion bar 23. That is, it is confirmed that the warp of the torsion bar 23, in other words, the straightness greatly affects the swing angle of the swing body 22 of the vibration element 30.

  Therefore, in the present invention, in order to improve the straightness of the torsion bar 23, the following method is proposed.

When forming the torsion bar 23 from a plate-like material, the torsion bar 23 is processed into a predetermined shape by press processing, laser processing, wire cutting, etching, superplastic processing, or the like. In this case, the variation in the amount of warpage of the torsion bar 23 obtained is large, and is in the range of 100 μm to 200 μm. In particular, in the case of processing from a roll-shaped material, the RD direction, which is the rolling direction, generally has a larger initial warp than the TD direction, which is a direction orthogonal to the rolling direction. Therefore, when used as the torsion bar 23, it is effective as a countermeasure against warping of the torsion bar 23 to set the TD direction as the longitudinal direction of the torsion bar 23. That is, by forming the torsion bar 23 by a tensile process, a processing mark by the tensile process is formed on the outer peripheral surface of the torsion bar 23. The identification, as schematically shown in FIGS. 19 and 20, processing marks the material surface, i.e. can be determined in the direction of the kerf C _S. That is, longitudinal kerf C _S extends is rolling direction.

  Further, for example, heat treatment is performed as an age hardening treatment in order to improve the vibration characteristics of the material. However, when the torsion bar 23 is processed and formed with SUS304 or the like, in addition to this heat treatment, the material is subjected to the necessary prescribed tension in the furnace. By performing so-called tension annealing, it is possible to almost eliminate the warpage. Further, if the torsion bar 23 is slightly warped even after such age hardening treatment, two torsion bars having the same warpage amount, in other words, straightness are prepared. As schematically shown in FIG. 20, the two torsion bar pieces 23 a and 23 b are back-to-back so as to be warped against each other and bonded together with an adhesive or the like, and assembled as one torsion bar 23. . The amount of warpage of the torsion bar 23 formed in this way is 10 μm or less, and the maximum deflection angle is ± 45 degrees as shown in FIG. 18, and the vibration element 17 capable of optical scanning at a wide angle is stably supplied. be able to.

Next, when the torsion bar 23 is processed from a linear material such as a round bar or a square bar, or processed from a raw material into a linear shape, the torsion bar 23 is processed into a predetermined shape by dicing. In this case as well, the amount of warpage of the torsion bar 23 obtained is large as in the case of forming from a plate-like material. In order to reduce the amount of warpage of the torsion bar 23, that is, to improve the straightness, it is effective to iron the linear material at the time of dicing, that is, to iron while applying tension. The identification in this case, it is possible to determine the direction of kerf C _S a which is formed on the surface of the material. That is, FIG. 21, as schematically shown in FIG. 22, kerf C _S a spiral with respect to the longitudinal direction of the torsion bar 23 is formed. In the die machining, the machining rate determined by the ratio of the cross-sectional area of the torsion bar 23 before and after the machining is the most important factor, and the optimum value is 70 to 80%. The amount of warpage of the torsion bar 23 formed in this way is also 10 μm or less, and the vibration element 30 capable of optical scanning at a wide angle can be stably supplied.

By applying the processing as described above to the plate-like material or the linear material, the straightness is improved so that the longitudinal axis A of the torsion bar 23 and the ideal swing axis A _R coincide with each other, and the light is emitted at a wide angle. Can be realized. In this way, the straightness of the torsion bar 23 is improved in this embodiment, but the straightness is further improved by adding the gravity center position correction member 24 to the oscillator 22 as in the previous embodiment. Can be made. Specifically, the center of gravity position of the oscillator 22 shown in FIG. 6 is brought closer to the surface of the glass surface plate 33 by joining the center of gravity position correcting member 24 to the surface of the second plate member 30 of the oscillator 22. Thereby, the warp of the torsion bar 23 can be reduced, and as a result, the longitudinal axis A of the torsion bar 23 and the ideal swing axis A _R can be made to coincide.

  The present invention is configured as described above to ensure a desired straightness of the torsion bar and to make the vibration element advantageous for widening the design range of the deflection angle, an optical scanning device, and an image using the same. A forming apparatus and an image projection apparatus can be realized.

  23 to 26 schematically show a method for assembling the vibration element according to the present invention schematically shown in FIG. Note that FIG. 23 shows a torsion bar, a rocking body (first and second plate members), and a magnet in a disassembled state as components constituting the vibration element. The original coordinate axes (x, y, z) are shown. The main part of the vibration element is assembled in the order of FIGS. 27 to 29 schematically show examples of arrangement positions of magnets arranged inside the oscillating body constituting the vibration element.

  In the embodiment shown in FIGS. 23 to 26, the material of the torsion bar 23 constituting the vibration element 17 is formed from a linear material made of a work-hardening and age-hardening type Co—Ni-based alloy as described later. ing. More specifically, the SPRON 510 wire having a diameter of 300 μm is used as the material of the torsion bar 23. The torsion bar 23 is not limited to a linear material, and can be formed of a plate material.

  The magnet 31 has a cylindrical shape with a diameter of 200 μm and a length of 2 mm, but is not limited to a cylindrical shape, and may be a prism.

  The oscillating body 22 constituting the vibration element 17 is composed of first and second plate members 29 and 30 having the same size and shape as in the above-described embodiment. The first and second plate members 29 and 30 are Si wafers each having a thickness of 300 μm. The first and second plate members 29 and 30 have a rectangular shape of 1 mm in the x direction and 3 mm in the y direction. The joint surfaces 29a, 30a of the first and second plate members 29, 30 constituting the oscillating body 22 are respectively provided with torsion bar housing grooves 29b, 30b and magnet housing grooves 29c, 30c (one magnet housing groove 30c). Only shown). The torsion bar housing grooves 29b, 30b are formed so as to extend in the longitudinal direction along the x axis at the substantially central portion of the joint surface 29a of the first plate member 29. The magnet housing groove 30c is formed so as to extend in the lateral direction along the y-axis at the front portion (x-axis direction in FIG. 23) of the joint surface 30a of the second plate member 30. The length of the magnet housing groove 30 c along the coordinate axis y direction is the same as the length of the magnet 31. The widths of the torsion bar housing grooves 29 b and 30 b are the same as the diameter of the torsion bar 23, and their depth is ½ of the diameter of the torsion bar 23. Similarly, the width of the magnet housing groove 30 c is the same as the diameter of the magnet 31, and the depth is ½ of the diameter of the magnet 31. Further, the length of the magnet housing groove 30 c in this embodiment is the same as the length of the magnet 31. In the present embodiment, both ends of the magnet housing groove 30c are closed, but the present invention is not limited to this, and both ends may be open as shown in other embodiments. Further, the cross-sectional shape of the torsion bar housing grooves 29b and 30b may be a rectangular shape as shown in FIG. 23 or a semicircular shape. Similarly, the semicircular shape as shown in FIG. 23 may be sufficient as the cross-sectional shape of the magnet accommodation groove | channel 30c, and a rectangular shape may be sufficient as it.

  As understood from the above structure, the torsion bar housing grooves 29b and 30b and the magnet housing groove 30c intersect with each other on the respective joint surfaces 29a and 30a in the present embodiment. Note that a magnet accommodation groove 29c (not shown) having the same size and shape as the magnet accommodation groove 30c formed in the second plate member 30 is also formed on the joint surface 29a of the first plate member 29. Needless to say, it is formed.

  Next, a method for assembling the vibration element 17 will be described. First and second plate members 29 and 34a and a magnet 31 constituting the torsion bar 23, the rocking body 22 are prepared. At this time, the torsion bar accommodating grooves 29b and 30b and the magnet accommodating grooves 29c and 30c orthogonal to each other are formed on the joint surfaces 29a and 30a of the first and second plate members 29 and 34a, respectively.

  Subsequently, the magnet 31 is positioned at a predetermined position with respect to the oscillating body 22 by incorporating the magnet 31 into the magnet housing groove 30 c of the second plate member 30 constituting a part of the oscillating body 22. Subsequently, with the positioned magnet 31 as a reference, the tip of the torsion bar 23 abuts against the side surface of the magnet 31, and the torsion bar 23 is incorporated into the torsion bar accommodating groove 30 b of the second plate member 30. Thereby, the tip of the torsion bar 23 is positioned at a predetermined position with respect to the rocking body 22. As a result, the torsion bar 23 is arranged such that the longitudinal axis A of the torsion bar 23 is orthogonal to the longitudinal direction of the rocking body 22. Finally, the bonding surface 29a of the first plate member 29 is opposed to the bonding surface 30a of the second plate member 30, and the first plate member 29 is moved in such a manner that the torsion bar 23 and the magnet 31 are sandwiched therebetween. The second plate member 30 is joined. At this time, the exposed upper half of the torsion bar 23 is incorporated into the torsion bar accommodating groove 29b formed in the first plate member 29, and the exposed upper half of the magnet 31 is the second plate. The member 30 is incorporated in the magnet housing groove 30b.

  In this way, the torsion bar 23, the rocking body 22 and the magnet 31 are accurately positioned at relative predetermined positions, and the magnet 31 is embedded in the rocking body 22. The magnet 31 can be disposed at any position along the x-axis direction with respect to the oscillator 22 as shown in FIGS. For example, the magnet 31 is disposed at the front end in FIG. 27, the center in FIG. 28, and the rear end in FIG. As shown in FIG. 28, when the magnet 31 is disposed at the center of the oscillator 22, for example, the same configuration as that of the embodiment shown in FIGS. Further, when the magnet 31 is disposed at the rear end portion of the oscillating body 22, the same configuration as that of the embodiment shown in FIGS. 27 to 29, it will be understood that the torsion bar 23 is disposed in a state orthogonal to the magnet 31, that is, in a state orthogonal to the longitudinal direction of the oscillator 22.

  By the way, since the torsion bar 23 can be present with a small amount of warpage, the straightness of the torsion bar 23 is lowered. When such a warp exists in the torsion bar 23, the smooth rocking motion of the rocking body 22 supported by the torsion bar 23 is lost, and as a result, the deflection angle α of the light reflecting surface 21 becomes small with respect to the input energy. Act on. In other words, when the oscillating body 22 is fixed to the warped torsion bar 23, the longitudinal axis A of the torsion bar 23 does not coincide with the ideal oscillating axis, and the oscillating body 22 is likely to generate abnormal vibration. . As a result, in order to cause the light reflecting surface 21 of the oscillating body 22 to oscillate at a desired deflection angle α, more electrical energy must be input to the sheet coil 26.

  As a countermeasure against such warping of the torsion bar 23, it is conceivable to add a gravity center position correcting member 24 to the rocking body 22 as shown in FIGS. Specifically, the center of gravity position of the oscillator 22 is changed as shown in FIG. 3 by joining the center of gravity correction member 24 having a different weight to the surface of the second plate member 30 of the oscillator 22. Thereby, the curvature of the torsion bar 23 can be reduced, and as a result, the longitudinal axis A of the torsion bar 23 can be configured to coincide with the ideal swing axis.

  The present invention can simplify the assembly of the vibration element and can improve the positioning system of components such as a torsion bar, a rocking body, and a magnet constituting the vibration element. Further, since the magnet is disposed inside the rocking body, it is possible to suppress and further prevent the floating substance such as dust from directly adhering. Furthermore, by improving the positioning accuracy, the center-of-gravity shift of the entire vibration element is also reduced. Therefore, it is possible to provide an optical scanning apparatus capable of realizing stable optical scanning, and an image forming apparatus or an image projection apparatus using the same. it can.

  In the above-described embodiments, the torsion bar 23 having a cantilever structure has been described. However, both ends in the longitudinal direction of the torsion bar 23 are fixed between the frame body 28 and the cover member 25, and the rocking body 22 is provided at the center thereof. May be fixed.

  The present invention can also be applied to an image projector such as an overhead projector, and the concept of such another embodiment of the present invention is shown in FIG. The same reference numerals are used, and duplicate descriptions are omitted. That is, the image projection apparatus 40 in the present embodiment includes an optical scanning apparatus 14 having the same basic configuration as that of the previous embodiment, an optical deflection apparatus 42 that deflects light from the light source 41 in a predetermined direction, and the optical deflection apparatus. And a screen 43 on which the light deflected by 42 is irradiated.

Optical deflecting device 42 is intended to deflect in a direction parallel to the ideal pivot axis A _R of the light from the light source 41 reflected by the light reflecting surface 21 of the oscillator 22 of the vibrating element 17 of the optical scanning device 14 is there. Since the light deflection speed of the light deflecting device 42 can be made relatively slower than the vibration period of the oscillating body (not shown) of the vibration element 17, a known galvanometer mirror is used in this embodiment.

  Light emitted from the light source 41 including the three primary colors of RGB is two-dimensionally scanned by the vibration element 17 and the light deflecting device 42 and projected as an image on the screen 43.

The deflection angle α of the light reflecting surface 21 of the oscillating body 22 constituting the main part of the oscillating element 17 is adjusted by the element driving unit 18 based on a control signal output from the control device 19. Further, similarly the optical deflecting device 42, based on the output from the controller 19, the deflection angle about the axis of the galvanometer mirror that is orthogonal to the ideal pivot axis A _R of the oscillator 22 is controlled. Image information projected on the screen 43 is transmitted from the input unit 44 to the control device 19, and information regarding the distance of the optical path from the light source 41 to the screen 43 is input from the distance measuring unit 45. The control device 19 sets the projection angle of view and magnification according to the information from the input unit 44 and the distance measuring unit 45 and the scanning angle of the vibration element 17 and the light deflection device 42 based on the image size and the aspect ratio. Change each. Note that the enlargement ratio of the image can also be achieved by on / off control of energization to the light source 41 without changing the scanning angle. However, by reducing the off time of the light source 41 by changing the scanning angle, a high-luminance image can be projected on the screen 43.

  Also in the image projection apparatus 40 of this embodiment, since the oscillator 22 is fixed to the torsion bar 23 made of a work-hardening and age-hardening type Co—Ni-based alloy, instability such as jitter in addition to downsizing is achieved. It can be reduced, and stable operation is possible even when the scanning angle is changed. Moreover, since the distortion amplitude dependency of the vibration attenuation rate is small, there is no sudden increase in power consumption when the scanning angle is increased. Furthermore, the driving power of the light source 41 can be reduced by the effective use of light. As a result, in addition to downsizing, the capacity of the element driving unit 18 and the power source can be reduced, and a high-performance image projection apparatus 40 that is small and has a large projection angle of view can be realized.

  The vibration element 17 according to the present invention can be applied to, for example, the potential sensor disclosed in Patent Document 2 in addition to the optical scanning device 14 described above. In the image forming apparatus such as the LBP 10 described above, it is necessary to uniformly charge the potential of the photosensitive drum 11 in order to obtain a stable quality image. For this reason, the charged potential of the photosensitive drum 11 is measured using a potential sensor, and the result is used to perform feedback control of the voltage applied to the charging unit so as to keep the potential of the photosensitive drum 11 uniform. In this potential sensor, a pair of detection electrodes are arranged on the plane portion of the oscillating body 22, and the potential measurement target surface, that is, the surface of the photosensitive drum 11, which is arranged in a state of being opposed to the pair of detection electrodes. The distance from the surface is changed by the vibration of the oscillator 22. Then, by changing the electrostatic capacitance between the detection electrode and the surface of the photosensitive drum 11, an output signal appearing as detection power is detected. In this potential sensor, by appropriately designing the torsional rigidity of the torsion bar 23, the form of the rocking body 22, and the like, the rocking body 22 can be easily rocked at a large frequency. In addition, even if the oscillator 22 is downsized, it is easy to appropriately process signals from the respective detection electrodes by providing a plurality of pairs of detection electrodes on the plane portion of the oscillator 22. For this reason, even if the apparatus is downsized, the potential of the surface of the photosensitive drum 11 can be measured with high reliability and high sensitivity and relatively high measurement accuracy.

  As described above, the present invention should be construed only from the matters described in the scope of the claims, and in the above-described embodiments, the matters described in all the changes and modifications included in the concept of the present invention are described. Other than possible. That is, all matters in the above-described embodiment are not intended to limit the present invention, and include any configuration not directly related to the present invention. To get.

10 LBP (Laser Beam Printer)
DESCRIPTION OF SYMBOLS 11 Photosensitive drum 12 Exposure part 13 Laser light source 14 Optical scanning device 15 Collimating optical system 16 f (theta) lens 17 Vibrating element 18 Element drive part 19 Control apparatus 20 Base 21 Light reflection surface 22 Oscillator 23 Torsion bar 23a, 23b Torsion bar piece 24 Center of gravity Position correction member 25 Cover member 26 Sheet coil 27 Substrate 28 Frame body 29, 30 Plate member 29a, 30a Joint surface 29b, 30b Torsion bar housing groove 29c, 30c Magnet housing groove 31 Magnet 31a Hole 32 Hole 33 Glass surface plate 34 BD sensor 35 Control unit 36 Stopper unit 37 Notch unit 40 Image projection device 41 Light source 42 Light deflection device 43 Screen 44 Input unit 45 Distance measuring unit A Longitudinal axis of torsion bar A _R Ideal swing axis α Deflection angle C _S line G Center of gravity of rocking body h Glass Height from the surface of the surface plate to the center of gravity of the oscillator L Laser light O Center of attachment of the base of the torsion bar to the base S Internal space

Claims (8)

Base and
A torsion bar protruding from this base,
An oscillating body provided on the side opposite to the base side of the torsion bar;
A vibration element comprising: a torsion bar and a center of gravity position correction member for correcting a center of gravity position of the rocking body. Base and
A torsion bar protruding from this base,
An oscillating body provided on the side opposite to the base side of the torsion bar;
A center-of-gravity position correcting member that corrects the center-of-gravity position of the torsion bar and the rocking body, passes through the attachment center of the one end side of the torsion bar with respect to the base, and extends in a straight line along the longitudinal direction of the torsion bar The plane portion of the rocking body is in an orthogonal state with respect to a virtual plane including an ideal rocking axis that is fixed and the center of gravity of the rocking body fixed to the torsion bar.
A vibrating element, wherein a center of gravity of the center of gravity position correcting member is in the virtual plane and is located closer to the ideal swing axis than the center of gravity of the swing body.   The vibration element according to claim 2, wherein the center-of-gravity position correction member is attached to a surface of the torsion bar that faces the ideal swing axis.   The rocking body includes two plate members having the same size and shape that are joined to each other with the torsion bar interposed therebetween, and the center-of-gravity position correction member is disposed on the side closer to the ideal rocking axis. The vibration element according to any one of claims 1 to 3, wherein the vibration element is disposed between the plate member or the one plate member and the torsion bar.   3. The center-of-gravity position correcting member has a wedge shape in which a thickness dimension along the virtual plane gradually decreases toward the one end of the torsion bar along the axis of the torsion bar. The vibration element according to any one of 4. Base and
A torsion bar protruding from this base,
An oscillating body having a light reflecting surface provided on a side opposite to the base side of the torsion bar;
A center-of-gravity position correcting member that corrects the position of the center of gravity of the torsion bar and the rocking body;
Drive means for swinging the swing body;
An optical scanning device comprising: a light source that emits light toward the light reflecting surface of the rocking body. An optical scanning device according to claim 6;
An image forming apparatus comprising: an image forming medium on which light from a light source of the optical scanning device is irradiated through a light reflecting surface of an oscillating body of the optical scanning device. An optical scanning device according to claim 6;
An optical deflecting device for deflecting light from a light source reflected by the light reflecting surface of the oscillator of the optical scanning device;
An image projection apparatus comprising: a screen irradiated with light deflected by the light deflection apparatus.

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