JP2008070786A - Optical deflector, optical scanning device, and image forming apparatus - Google Patents

Abstract

The present invention provides an optical deflector in which deformation at the time of processing and assembling of a polygonal mirror is suppressed to be small and the surface accuracy of a deflecting / reflecting surface is improved, an optical scanning device using the same, and an image forming apparatus.
Light in which polygon mirrors 104 and 105 each having deflecting and reflecting surfaces 104a and 104b and 105a and 105b are fixed to a bearing shaft 102 and a rotating body 101 supported by a bearing housing 111 is rotationally driven by a motor. The polygon mirrors 104 and 105, which are deflectors, have boss portions 104b and 105b formed integrally on one end face, and are stacked in the axial direction of the rotational drive.
[Selection] Figure 1

Description

  The present invention relates to an optical deflector used in a color image forming apparatus or the like.

In Patent Document 1, as an optical deflector used in a color image forming apparatus, a plurality of polygon mirrors are stacked in the rotation direction, and the deflection reflection surfaces of the polygon mirrors at each stage are fixed at a predetermined angular deviation in the rotation direction. An optical deflector is disclosed.
This color image forming apparatus can output images at high speed while reducing the number of light sources of the optical scanning device, and can save resources and cost as an image forming apparatus. Further, since the failure probability of the light source can be reduced by reducing the number of light sources, the reliability of the image forming apparatus can be improved.
JP 2005-92129 A

  However, the conventional optical deflector has a problem that the surface accuracy of the deflecting / reflecting surface deteriorates when two polygon mirrors each having a deflecting / reflecting surface are stacked and assembled.

  Moreover, since it is small in size, it easily deforms even when processing a single polygonal mirror, and there is a problem that it is difficult to obtain a desired surface accuracy.

  The present invention has been made in view of such a problem, and an optical deflector in which the deformation accuracy during processing and assembling of a polygon mirror is suppressed to be small and the surface accuracy of the deflecting reflecting surface is increased, an optical scanning device using the optical deflector, and an image An object is to provide a forming apparatus.

  In order to achieve the above object, the present invention provides, as a first aspect, an optical deflection in which a plurality of polygon mirrors having a deflecting reflecting surface are fixed to a shaft and a rotating body supported by a bearing is rotationally driven by a motor. Each of the polygonal mirrors is provided with an optical deflector in which a boss portion is integrally formed on at least one end surface, and each polygonal mirror is stacked in the axial direction of rotation drive. It is.

  In the first aspect of the present invention, it is preferable that the plurality of polygon mirrors are fixed so that the deflection reflection surface is shifted by a predetermined angle in the rotation direction for each stage.

  In any configuration of the first aspect of the present invention, it is preferable that each polygonal mirror is stacked while being in contact with another polygonal mirror via a boss portion.

In any of the above-described configurations of the first aspect of the present invention, the boss portion is preferably cylindrical.
Alternatively, the boss portion is preferably provided with a position reference surface serving as a reference position in the rotation direction with respect to the shaft, and in addition to this, the position reference surface may be formed substantially parallel to the deflection reflection surface. preferable. In these cases, it is preferable that a plurality of position reference planes are formed so that the mass distribution around the axis is uniform.

  In any of the above-described configurations of the first aspect of the present invention, the polygonal mirror is preferably formed by forging.

  In order to achieve the above object, the present invention provides, as a second aspect, an optical scanning device using the optical deflector according to any one of the first aspect of the present invention, comprising a semiconductor laser. The light beam is guided to the surface to be scanned through an optical system including a light deflector to form a light spot, and the light beam is deflected by the light deflector to optically scan the surface to be scanned. An optical scanning device is provided.

  In the second aspect of the present invention, it is preferable that there are a plurality of light beams from the semiconductor laser, and the surface to be scanned is optically scanned with the plurality of light beams.

  In order to achieve the above object, the present invention provides, as a third aspect, an image forming apparatus using the optical scanning device according to any one of the configurations of the second aspect of the present invention. Is a photosensitive surface of a photosensitive member, and provides an image forming apparatus characterized in that a latent image is formed on the photosensitive member by optical scanning, and the latent image is visualized to form an image.

  ADVANTAGE OF THE INVENTION According to this invention, the optical deflector which suppressed the deformation | transformation at the time of the process of a polygon mirror and an assembly small, and improved the surface precision of the deflection | deviation reflective surface, an optical scanning device using this, and an image forming apparatus can be provided.

[First Embodiment]
A first embodiment in which the present invention is suitably implemented will be described. FIG. 1 is a cross-sectional view of an optical deflector according to the present embodiment. FIG. 2 is a perspective view of the optical deflector according to the present embodiment.
The rotating body 101 of the optical deflector includes a flange 103 that is shrink-fitted on the outer periphery of the bearing shaft 102, two polygon mirrors 104 and 105 stacked on the flange 103, a mirror holder 106, a leaf spring 107, A retaining ring 108 and a rotor magnet 109 are provided.

  The radial bearing is an oil-impregnated bearing including a bearing shaft 102 and a fixed sleeve 110, and the bearing gap is set to 10 μm or less in diameter. In order to ensure the stability at high speed rotation, the radial bearing is provided with a dynamic pressure generating groove (not shown). The dynamic pressure groove is provided on the outer peripheral surface of the bearing shaft 102 or the inner peripheral surface of the fixed sleeve 110. However, it is preferable to apply the dynamic pressure groove on the inner peripheral surface of the fixed sleeve 110 made of a sintered member having good workability. The material of the bearing shaft 102 is preferably martensitic stainless steel (for example, SUS420J2) that can be quenched, can have high surface hardness, and has good wear resistance.

  The rotor magnet 109 is fixed to the lower inner surface of the flange 103 and constitutes an outer rotor type brushless motor together with a stator core 112 (winding coil 112a) fixed to the bearing housing 111. The rotor magnet 109 is a bonded magnet using a resin as a binder, and the outer diameter portion of the rotor magnet 109 is held by the flange 103 so as not to be broken by a centrifugal force during high-speed rotation. By press-fitting and fixing the rotor magnet 109, the fixed part does not move finely even in a higher-speed rotation and in a high-temperature environment, and the rotating body balance can be maintained with high accuracy.

  The axial bearing is a pivot bearing in which a convex curved surface 102 a formed on the lower end surface of the bearing shaft 102 and a thrust receiving member 113 are brought into contact with the opposing surface. The thrust receiving member 113 is made of martensite stainless steel, ceramics, or a metal member subjected to a hardening treatment such as a DLC (diamond-like carbon) treatment, or a resin material, etc., to improve lubricity, and wear powder Occurrence is suppressed.

  The sleeve 110 and the thrust receiving member 113 are accommodated in the bearing housing 111, and oil is prevented from flowing out by the fluid seal 114.

  When the rotating body 101 is rotated at a high speed of 25000 rpm or higher, the balance of the rotating body 101 must be corrected and maintained with high accuracy in order to reduce vibration. The rotating body 101 has two unbalance correction portions at the top and bottom, and the balance is corrected by applying adhesive to the circumferential recess 106a of the mirror retainer 106 on the upper side and the circumferential recess 103a of the flange 103 on the lower side. I do. The unbalance amount needs to be 10 mg · mm or less. For example, the correction amount at a position with a radius of 10 mm from the axial center is kept at 1 mg or less. In the case where it is difficult to manage with a deposit such as an adhesive when performing the minute correction as described above, or because the amount is small, the adhesive force is weak, and peeling or scattering occurs at a high speed of 40,000 rpm or more. It is preferable to implement a method for removing a part of the rotating body (cutting with a drill or laser processing).

  The motor system in this embodiment is a system called an outer rotor type in which a magnetic gap is provided in the radial direction and the rotor magnet 109 is laid out on the outer diameter portion of the stator core 112. In the rotation drive, a signal output from the Hall element 116 mounted on the circuit board 115 by the magnetic field of the rotor magnet 109 is referred to as a position signal, and the drive IC 117 performs excitation switching of the winding coil 112a to rotate. The rotor magnet 109 is magnetized in the radial direction, and rotates by generating rotational torque with the outer periphery of the stator core 112. The rotor magnet 109 has a magnetic path open in the outer diameter and height direction other than the inner diameter, and a Hall element 116 for switching excitation of the motor is disposed in the open magnetic path. The connector 118 is connected to a harness (not shown), receives power supply from the main body, and inputs and outputs control signals such as starting and stopping of the motor and the number of rotations.

  Four-sided polygon mirrors 104 and 105 are stacked and fixed on the flange 103 in two stages in the rotation axis direction. The flange 103 is shrink-fitted to the bearing shaft 102, and the surface on which the polygon mirror is mounted is processed with high accuracy in flatness and perpendicularity to the bearing shaft 102.

  The two polygonal mirrors 104 and 105 stacked are continuous with the deflecting / reflecting portion on which the deflecting / reflecting surfaces 104a and 105a are formed, and cylindrical boss portions 104b and 105b are respectively formed.

  The polygon mirrors 104 and 105 are parts having the same shape, and are stacked so that the bosses are in contact with each other, and the deflection reflection surfaces 104a and 105a are fixed with a 45 ° offset in the rotation direction. The respective deflecting / reflecting surfaces 104a and 105a are arranged at intervals in the rotation axis direction (thickness direction). That is, the lower polygon mirror 104 is configured to have a deflecting reflecting surface biased on the lower side and the upper polygon mirror 105 has an deflected reflecting surface on the upper side.

  In addition, if the polygonal mirrors 104 and 105 are formed by forging the basic shape integrated with the boss part, the cost for forming the part shape can be reduced compared to the case of cutting the polyhedral shape from the material by cutting. It is.

In the present embodiment, since the bosses 104b and 105b are provided between the polygon mirrors 104 and 105, the axial fixed compression force during the processing of the polygon mirror is relaxed, the deformation is suppressed, and the stacking is assembled. Therefore, it is possible to suppress the deformation at the time and to improve the surface accuracy of the deflecting / reflecting surface.
Further, by forming a deflecting / reflecting surface only in a necessary portion in the axial direction and using a portion not used for light deflection as a cylindrical boss portion, the windage loss of the mirror can be reduced.

In this example, the deflecting / reflecting surfaces 104a and 105a are fixed by being shifted by 45 ° in the rotation direction. However, the present invention can also be applied to an optical deflector in which the deflecting / reflecting surfaces 104a and 105a are not shifted in the rotating direction.
In this example, the boss portions 104b and 105b are formed only on one side of the polygon mirrors 104 and 105, but the boss portions may be provided on both sides of the polygon mirror.

[Second Embodiment]
A second embodiment in which the present invention is suitably implemented will be described. FIG. 3 shows an optical deflector according to this embodiment. Since this optical deflector is the same as the optical deflector according to the first embodiment except that the configuration of the polygonal mirror of the rotating body is different, common configurations are denoted by the same reference numerals and overlapped. Description is omitted.
The rotating body 121 of the optical deflector includes a flange 103 that is shrink-fitted on the outer periphery of the bearing shaft 102, two polygon mirrors 124 and 125 stacked on the flange 103, a mirror holder 106, a leaf spring 107, A retaining ring 108 and a rotor magnet 109 are provided.

  The two polygonal mirrors 124 and 125 that are stacked are connected to the deflecting / reflecting part on which the deflecting / reflecting surfaces 124a and 125a are formed, and are formed as planes parallel to the deflecting / reflecting surfaces 124a and 125a. 124c and 125c are formed to form a quadrangular prism-shaped boss portion.

  The polygon mirrors 124 and 125 are parts having the same shape, and are stacked so that the bosses are in contact with each other, and the deflecting reflection surfaces 124a and 125a are fixed with being shifted by 45 ° in the rotation direction. The fixed position adjustment reference surfaces 124c and 125c are used as reference surfaces during assembly as described later, and are not used for light deflection.

  The two polygonal mirrors 124 and 125 are configured such that a jig (not shown) is abutted against the fixed position adjustment reference surfaces 124c and 125c, and the positions of the polygonal mirrors in the rotational direction are adjusted and held. A retaining ring 108 is fixed to the upper portion of the bearing shaft 102 with the leaf spring 107 interposed therebetween. The leaf spring 107 is compressed in the rotational direction and fixed in an elastically deformed state, thereby serving as a pressing spring. The two polygon mirrors 124 and 125 and the mirror pressing 106 are simultaneously pressed and fixed between the flange 103. .

  By the above method, the optical deflector according to the present embodiment can accurately position and fix the two polygonal mirrors 124 and 125 at a predetermined angle.

The fixed position adjustment reference surfaces 124c and 125c are not necessarily formed in parallel with the deflecting and reflecting surfaces 124 and 125, but are preferably formed in parallel.
That is, the leaf spring 107 is compressed in the rotational direction and fixed in an elastically deformed state, so that a compressive force acts on the polygonal mirrors 124 and 125 in the rotational axis direction, but the fixed position adjusting reference surfaces 124c and 125c are provided. When formed parallel to the deflecting and reflecting surfaces 124a and 125a, the deformation of the deflecting and reflecting surfaces 124a and 125a in the optical scanning direction (longitudinal direction) is made substantially uniform, and it becomes easy to ensure the surface accuracy required for the deflecting and reflecting surfaces 124a and 125a.

  The fixed position adjustment reference surfaces 124c and 125c only need to be formed on at least one surface of each of the polygonal mirrors 124 and 125, but the mass distribution around the central axis of the rotating body is made uniform, and the initial imbalance is reduced and balanced. In order to facilitate the correction, it is preferable that the number of surfaces is two or more. In particular, the number of surfaces is preferably the same as the number of surfaces of the polygon mirror.

  As in the first embodiment, if the basic shape integrated with the boss part is formed by forging, the polygonal mirrors 124 and 125 are part formed as compared with the case of cutting the polyhedral shape from the material by cutting. The cost can be reduced.

  Further, as in the first embodiment, the deflecting and reflecting surfaces 124a and 125a are fixed by being shifted by 45 ° in the rotation direction, but they may not be shifted in the rotation direction.

[Third Embodiment]
A third embodiment in which the present invention is preferably implemented will be described. FIG. 4 shows a configuration of the optical scanning device according to the present embodiment. This optical scanning device is an optical scanning device using the optical deflector according to the first or second embodiment.
In FIG. 4, reference numerals 1 and 1 ′ denote semiconductor lasers. The semiconductor lasers 1, 1 ′ are “two light emission sources constituting one light source”, and each emits one light beam (in other words, the semiconductor lasers 1, 1 ′ constitute a multi-beam light source. ). These semiconductor lasers 1, 1 ′ are held by the holder 2 in a predetermined positional relationship.

  The respective light beams emitted from the semiconductor lasers 1 and 1 ′ are converted into light beam forms (parallel light beams or weakly divergent or weakly convergent light beams) suitable for the subsequent optical system by the coupling lenses 3 and 3 ′, respectively. The Here, it is assumed that the light beams coupled by the coupling lenses 3 and 3 ′ are parallel light beams.

  Each light beam emitted from the coupling lenses 3 and 3 ′ in a desired light beam shape passes through the opening of the aperture 12 that regulates the light beam width and is “beam shaped” and then enters the half mirror prism 4. To do. The light beam incident on the half mirror prism 4 is divided into two in the sub-scanning direction by the action of the half mirror prism 4, and each is divided into two light beams.

FIG. 5 shows how the light beam is split.
In order to avoid the complexity of the figure, the light beam L1 emitted from the semiconductor laser 1 is shown as a representative. Although the vertical direction in FIG. 5 is the sub-scanning direction, the half mirror prism 4 is incident on the semi-transparent mirror 4a, and a part of the half mirror prism 4a passes straight through the semi-transparent mirror 4a to become the light beam L11, and the rest is reflected on the semi-transparent mirror 4a Then, the light enters the reflecting surface 4b and is totally reflected by the reflecting surface 4b to become the light beam L12. The semi-transparent mirror 4a and the reflecting surface 4b are parallel to each other. Therefore, the light beams L11 and L12 emitted from the half mirror prism 4 are also Parallel. In this way, the light beam from the semiconductor laser 1 is divided into two in the sub-scanning direction as two light beams L11 and L12. The light beam from the semiconductor laser 1 ′ is also divided into two in the same manner.

  In this way, two light beams are emitted from one light source (m = 1), these two light beams are divided into two (q = 2) in the sub-scanning direction, and four light beams are obtained. can get.

These four light beams enter the cylindrical lenses 5a and 5b, and are condensed in the sub-scanning direction by these actions, and are formed in the vicinity of the polygon mirror optical deflector 7 as a “line image long in the main scanning direction”. Image.
Of the light beams emitted from the semiconductor lasers 1 and 1 ′ and divided by the half mirror prism 4, a light beam (light beam L 11 shown in FIG. 5) that passes straight through the half mirror 4 a of the half mirror prism 4 is cylindrical. A light beam (light beam L12 shown in FIG. 5) incident on the lens 5a, reflected by the semi-transparent mirror 4a, and further reflected by the reflecting mirror 4b is incident on the cylindrical lens 5b.

  The soundproof glass 6 is attached to the window of the soundproof housing of the polygon mirror type optical deflector. The four light beams from the light source side enter the polygon mirror optical deflector 7 through the soundproof glass 6, and the deflected light beams are emitted to the scanning imaging optical system side through the soundproof glass 6. .

As shown in FIG. 4, the polygon mirror optical deflector 7 has an upper polygon mirror 7a and a lower polygon mirror 7b stacked and integrated in two stages in the direction of the rotation axis, and is integrated by a drive motor (not shown). It can be rotated around.
Here, it is assumed that the upper polygon mirror 7a and the lower polygon mirror 7c have the same shape with four deflection reflection surfaces, but the deflection of the lower polygon mirror 7b with respect to the deflection reflection surface of the upper polygon mirror 7a. The reflection surface is shifted by a predetermined angle θ (= 45 °) in the rotation direction.

  The scanning imaging optical system includes first scanning lenses 8a and 8b, optical path bending mirrors 9a and 9b, second scanning lenses 10a and 10b, and photoconductive photoreceptors 11a and 11b.

The first scanning lens 8a, the second scanning lens 10a, and the optical path bending mirror 9a are emitted from two light beams (semiconductor lasers 1 and 1 ', which are deflected by the upper polygon mirror 7a of the polyhedral optical deflector 7. Two light beams transmitted through the semi-transparent mirror 4a of the half mirror prism 4) are guided onto the photoconductive photoreceptor 11a which is the corresponding optical scanning position, and two light spots separated in the sub scanning direction are obtained. A set of scanning imaging optical systems is formed.
The first scanning lens 8b, the second scanning lens 10b, and the optical path bending mirror 9b are two light beams (emitted from the semiconductor lasers 1 and 1 ′) deflected by the upper polygon mirror 7b of the polygon mirror optical deflector 7. The two light beams reflected by the half mirror 4a of the half mirror prism 4 are guided onto the photoconductive photosensitive member 11b which is the corresponding optical scanning position and separated in the sub scanning direction. A set of scanning imaging optical systems for forming a light spot is constructed.

The optical arrangement of the light beams emitted from the semiconductor lasers 1, 1 ′ is determined so that “the principal rays intersect in the vicinity of the position of the deflecting reflecting surface” when viewed from the rotational axis direction of the polygon mirror optical deflector 7. Therefore, each pair of two light beams incident on the deflecting / reflecting surface has a light beam mutual "open angle (when the light source side is viewed from the deflecting / reflecting surface side, the rotation axes of the two light beams are The angle formed by the projection onto the plane orthogonal to ”.
Due to this “open angle”, the two light spots formed on each of the photoconductive photoreceptors 11a and 11b are also separated in the main scanning direction, and thus two light beams for optically scanning each photoreceptor. Can be detected individually to synchronize the start of optical scanning for each light beam.

  In this way, the two-beam light beam deflected by the upper polygon mirror 7a of the polygon mirror optical deflector 7 is used to scan the photoconductive photosensitive member 11a by the two light beams, so that the polygon mirror light deflection is performed. By the two light beams deflected by the lower polygon mirror 7b of the device 7, the photoconductive photosensitive member 11b is subjected to multi-beam scanning by the two light beams.

  Since the deflecting and reflecting surfaces of the upper polygon mirror 7a and the lower polygon mirror 7b of the polygon mirror optical deflector 7 are shifted from each other by 45 ° in the rotational direction, the light deflected by the upper polygon mirror 7a of the optical deflector 7 by the upper polygon mirror 7a. When the beam optically scans the photoconductive photoreceptor 11a, the light beam deflected by the lower polygon mirror 7b is not guided to the photoconductive photoreceptor 11b. Conversely, when the light beam deflected by the lower polygon mirror 7b optically scans the photoconductive photoreceptor 11b, the light beam deflected by the upper polygon mirror 7a is not guided to the photoconductive photoreceptor 11a. That is, the optical scanning on the photoconductive photoreceptors 11a and 11b is alternately performed with a time shift.

FIG. 6 shows a state of optical scanning with respect to the photoconductive photoreceptors 11a and 11b. In order to avoid the complexity of the drawing, only one of the four light beams incident on the polygon mirror type optical deflector 7 is shown.
Here, the light beam incident on the polygon mirror optical deflector 7 is referred to as “incident light”, and the light beam deflected and emitted is referred to as “deflected light a, deflected light b”.

  FIG. 6A shows a situation when incident light enters the polygon mirror optical deflector 7 and the deflected deflected light a reflected and deflected by the upper polygon mirror 7a is guided to the optical scanning position. Yes. At this time, the deflected light b from the lower polygon mirror 7b does not go to the optical scanning position. FIG. 6B shows a situation when the deflected light b reflected and deflected by the lower polygon mirror 7b is guided to the optical scanning position. At this time, the deflected light a from the upper polygon mirror 7a does not go to the optical scanning position.

  In order to prevent the deflected light from the other polygon mirror from acting as ghost light while the deflected light from one of the polygon mirrors is guided to the optical scanning position, an appropriate light shielding means SD as shown in FIG. 6 is used. Thus, it is preferable to shield the deflected light that is not guided to the optical scanning position. In practice, this can be easily realized by making the inner wall of the soundproof housing non-reflective.

  As described above, in the present embodiment, the optical scanning of the photoconductive photoreceptors 11a and 11b (multi-beam type) is performed alternately. For example, when the optical scan of the photoconductive photoreceptor 11a is performed, a light source is used. If the light intensity of the light source is modulated by the image signal of the black image, and the light scanning of the photoconductive photoreceptor 11b is performed, the light intensity of the light source is modulated by the image signal of the magenta image. An electrostatic latent image of a black image can be written on the photoconductive photoconductor 11b.

  FIG. 7 shows a time chart in the case where the black image and the magenta image are written by the common light source (semiconductor lasers 1 and 1 ′) and all the light is turned on in the effective scanning area. A solid line indicates a portion corresponding to writing of a black image, and a wavy line indicates a portion corresponding to writing of a magenta image. As described above, the writing timing of the black image and the magenta image is determined by detecting the light beam toward the optical scanning start position by a not-shown synchronous light receiving means (usually a photodiode) provided outside the effective scanning area. The

  In the optical scanning device according to the present embodiment, the optical scanning of each deflection reflection surface of the polygon mirror is uniform and highly accurate, the number of parts and materials of the light source unit are reduced, the environmental load is reduced, and the failure of the light source Probability is also kept low.

[Fourth Embodiment]
A fourth embodiment in which the present invention is preferably implemented will be described. The image forming apparatus according to the present embodiment is an image forming apparatus using the optical scanning device according to the third embodiment of the present invention.
FIG. 8 shows the configuration of the optical system of the image forming apparatus according to the present embodiment. Here, a state seen from the sub-scanning direction, that is, the rotation axis direction of the polygon mirror type optical deflector 7 is shown. For simplification of explanation, illustration of a mirror for bending the optical path on the optical path from the polygon mirror type optical deflector 7 to the optical scanning position is omitted, and the optical path is shown as a straight line.
In this optical scanning device, m = q = 2, p = 1, and n = 4 (m: number of light sources, q: number of divisions, p: number of light beams, n: optical scanning device), and four light beams. Each scanning position is scanned with one light beam. Further, photoconductive photoreceptors 11Y, 11M, 11C, and 11K are disposed at the respective optical scanning positions, and electrostatic latent images formed on these four photoconductive photoreceptors are magenta, yellow, cyan, Visualized individually with black toner to form a color image.

  In FIG. 8, reference numerals 1YM and 1CK denote semiconductor lasers, respectively. Each of the semiconductor lasers 1YM and 1CK emits one light beam. The intensity of the semiconductor laser 1YM is alternately modulated with an image signal corresponding to a yellow image and an image signal corresponding to a magenta image. The intensity of the semiconductor laser 1CK is alternately modulated with an image signal corresponding to a cyan image and an image signal corresponding to a black image.

The light beam emitted from the semiconductor laser 1YM is converted into a parallel beam by the coupling lens 3YM, and after passing through the aperture 12YM, is shaped into a beam, and then enters the half mirror prism 4YM and is separated in the sub-scanning direction. Divided into light beams. The half mirror prism 4YM has the same configuration as the half mirror prism 4 shown in FIG.
One of the split light beams is used to write a yellow image and the other one is used to write a magenta image.

  The two light beams divided in the sub-scanning direction are respectively condensed in the sub-scanning direction by cylindrical lenses 5Y and 5M (arranged so as to overlap in the sub-scanning direction) arranged in the sub-scanning direction. The light enters the polygon mirror type optical deflector 7. The polygon mirror type optical deflector 7 has the same configuration as that shown in FIGS. 4 and 6, and polygon mirrors having four deflection reflecting surfaces are stacked in two stages in the rotation axis direction, and the polygon mirrors are mutually connected. Are integrated by shifting the deflection reflection surface in the rotation direction. A line image long in the main scanning direction by the cylindrical lenses 5Y and 5M is formed in the vicinity of the position of the deflection reflection surface of each polygon.

  The light beams deflected by the polygon mirror type optical deflector 7 are transmitted through the first scanning lenses 8Y and 8M and the second scanning lenses 10Y and 10M, respectively, and light spots at the optical scanning positions 11Y and 11M by the action of these lenses. Are formed, and these optical scanning positions are optically scanned.

Similarly, the light beam emitted from the semiconductor laser 1CK is converted into a parallel beam by the coupling lens 3CK, and after passing through the aperture 12CK, is shaped into a beam, and then enters the half mirror prism 4CK and is separated in the sub-scanning direction. Is divided into two light beams. The half mirror prism 4CK has the same configuration as the half mirror prism 4YM.
One of the split light beams is used to write a cyan image and the other one is used to write a black image.

  The two light beams divided in the sub-scanning direction are condensed in the sub-scanning direction by cylindrical lenses 5C and 5K (arranged so as to overlap in the sub-scanning direction) arranged in the sub-scanning direction, The light is incident on the polygon mirror type optical deflector 7 and deflected, and passes through the first scanning lenses 8C and 8K and the second scanning lenses 10C and 10K, respectively. By the action of these lenses, a light spot is formed at the optical scanning positions 11C and 11K. Then, these optical scanning positions are optically scanned.

  FIG. 9 shows the configuration of the image forming apparatus according to the present embodiment. As shown in the figure, one of the light beams deflected by the upper polygon mirror of the polygon mirror type optical deflector 7 constitutes the substance of the optical scanning position by the optical path bent by the optical path folding mirrors mM1, mM2, and mM3. The light is guided to the photoconductive photoconductor 11M, and the other light beam is guided to the photoconductive photoconductor 11C forming the substance of the optical scanning position by the optical path bent at the optical path bending mirrors mC1, mC2, and mC3.

  In addition, one of the light beams deflected by the lower polygon mirror of the polygon mirror type optical deflector 7 is guided to the photoconductive photosensitive member 11Y forming the substance of the optical scanning position by the optical path bent by the optical path folding mirror mY. The other light beam is guided to the photoconductive photosensitive member 11K that forms the substance of the optical scanning position by the optical path bent by the optical path bending mirror mK.

Accordingly, the light beams from the m = 2 semiconductor lasers 1YM and 1CK are divided into two light beams by the half mirror prisms 4YM and 4CK, respectively, so that four light beams are obtained. The photoconductive photoreceptors 11Y, 11M, 11C, and 11K are optically scanned. The photoconductive photoconductors 11Y and 11M are alternately scanned by the light beams obtained by dividing the light beam from the semiconductor laser 1YM into two as the polygonal optical deflector 7 rotates.
Each of the photoconductive photoconductors 11Y to 11M is rotated at a constant speed in the clockwise direction, and is uniformly charged by the charging rollers TY, TM, TC, and TK that form the charging means, and each receives light scanning of the corresponding light beam. Thus, each color image of yellow, magenta, cyan, and black is written, and a corresponding electrostatic latent image (negative image) is formed.

  These electrostatic latent images are reversed and developed by developing devices GY, GM, GC, and GK, respectively, and a yellow toner image, a magenta toner image, a cyan toner image, and a black toner are respectively formed on the photoconductive photoreceptors 11Y, 11M, 11C, and 11K. A toner image is formed.

  The toner images of these colors are transferred onto a transfer sheet (not shown). That is, the transfer sheet is conveyed by the conveyance belt 17, the yellow toner image is transferred from the photoconductive photoreceptor 11Y by the transfer machine 15Y, and the photoconductive photoreceptors 11M, 11C, and 15K are transferred by the transfer machines 15M, 15C, and 15K, respectively. A magenta toner image, a cyan toner image, and a black toner image are sequentially transferred from 11K.

  In this way, a yellow toner image to a black toner image are superimposed on the transfer sheet to form a color image. This color image is fixed on the transfer sheet by the fixing device 19.

As described above, the image forming apparatus according to the present embodiment is obtained by individually forming an electrostatic latent image on a plurality of photoconductive photosensitive members by optical scanning, and visualizing these electrostatic latent images as toner images. A tandem type image forming apparatus for forming a color image by superimposing and transferring a toner image on the same sheet-like recording medium, the number of photoconductive photoconductors is four, and as an optical scanning device, Using two light sources 1YM and 1CK, each light beam from each light source scans two photoconductive photoreceptors, and four photoconductive photoreceptors 11Y, 11M, 11C and 11K. The electrostatic latent images formed in the above are individually visualized with yellow, magenta, cyan, and black toners to form color images.
The polyhedral optical deflector 7 has uniform and high-precision optical scanning of each deflecting reflection surface, reduces the number of parts and materials of the light source unit, reduces the environmental load, and has a low light source failure probability.

  In this embodiment, the light scanning of each photoconductive photosensitive member is performed by a single beam method. However, each light source side is configured as shown in FIG. 4, and the light scanning of the photoconductive photosensitive member is performed by a multi-beam method. You can go there.

Each of the above embodiments is an example of a preferred embodiment of the present invention, and the present invention is not limited to this.
For example, the configurations of the optical deflector, the optical scanning device, and the image forming apparatus illustrated in the above embodiments are merely examples, and the present invention is not limited thereto.
As described above, the present invention can be variously modified.

It is a figure which shows the structure of the optical deflector concerning 1st Embodiment which implemented this invention suitably. It is a perspective view of the optical deflector concerning a 1st embodiment. It is a perspective view of the optical deflector concerning 2nd Embodiment which implemented this invention suitably. It is a figure which shows the structure of the optical scanning device concerning 3rd Embodiment which implemented this invention suitably. It is a figure which shows a mode that a light beam is divided | segmented. It is a figure which shows the state of the optical scanning with respect to a photoconductive photoconductor. It is a figure which shows the scanning timing of the light beam in an optical scanning device. It is a figure which shows the structure of the optical system of the image forming apparatus concerning 4th Embodiment which implemented this invention suitably. It is a figure which shows the structure of the image forming apparatus concerning 4th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 2 Holder 3 Coupling lens 4 Half mirror prism 5 Cylindrical lens 6 Soundproof glass 7 Optical deflector 8 First scanning lens 9 Optical path bending mirror 10 Second scanning lens 11 Photoconductive photoconductor 12 Aperture 15 Transfer machine 101 Rotating body DESCRIPTION OF SYMBOLS 102 Bearing shaft 103 Flange 103a, 106a Circumferential recessed part 104,105,124,125 Polyhedral mirror 104a, 104b, 105a, 105b, 124a, 124b, 125a, 125b Deflection reflective surface 106 Mirror holding | maintenance 107 Leaf spring 108 Retaining ring 109 Rotor magnet DESCRIPTION OF SYMBOLS 110 Fixed sleeve 111 Bearing housing 112 Stator core 112a Winding coil 113 Thrust receiving member 114 Fluid seal 115 Circuit board 116 Hall element 117 Drive IC
118 Connector 124c, 125c Reference plane for fixed position adjustment

Claims (11)

An optical deflector in which a plurality of polygon mirrors having a deflecting reflecting surface are fixed to a shaft and a rotating body supported by a bearing is driven to rotate by a motor,
Each of the polygonal mirrors has a boss formed integrally with at least one end surface thereof, and each of the polygonal mirrors is stacked in the axial direction of rotation drive.   2. The optical deflector according to claim 1, wherein the plurality of polygonal mirrors are fixed such that the deflecting reflecting surface is shifted by a predetermined angle in the rotation direction for each stage.   3. The optical deflector according to claim 1, wherein each of the polygon mirrors is stacked while being in contact with another polygon mirror via the boss portion.   The optical deflector according to claim 1, wherein the boss portion is cylindrical.   4. The optical deflector according to claim 1, wherein the boss portion is provided with a position reference surface serving as a reference position in a rotation direction with respect to the shaft. 5.   6. The optical deflector according to claim 5, wherein the position reference surface is formed substantially parallel to the deflecting / reflecting surface.   The optical deflector according to claim 5 or 6, wherein a plurality of the position reference planes are formed so that the mass distribution around the axis is uniform.   The optical deflector according to claim 1, wherein the polygonal mirror is formed by forging. An optical scanning device using the optical deflector according to any one of claims 1 to 8,
A light beam from a semiconductor laser is guided to a surface to be scanned through an optical system including the light deflector to form a light spot, and the light beam is deflected by the light deflector. An optical scanning device that performs optical scanning.   10. The optical scanning device according to claim 9, wherein there are a plurality of light beams from the semiconductor laser, and the surface to be scanned is optically scanned with a plurality of light beams. An image forming apparatus using the optical scanning device according to claim 9 or 10,
2. The image forming apparatus according to claim 1, wherein the optical scanning surface is a photosensitive surface of a photosensitive member, a latent image is formed on the photosensitive member by optical scanning, and the latent image is visualized to form an image.

Images