Scanning optical device and image forming apparatus

Abstract

To prevent an increase in the atmospheric temperature around a deflector and effectively perform dust proofing around the deflector.SOLUTION: A lid 102 has a plurality of openings H1, H2, H3, H4 for emitting laser beams to the outside of a scanning optical device 1, and comprises a protective wall 130 provided between the deflector 104 and the opening H3 arranged at a position closest to the deflector 104, of the openings H1, H2, H3, H4. The protective wall 130 stands up from the lid 102 and is extended in a scanning direction.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a scanning optical device and an image forming apparatus, and more particularly to a scanning optical device used in an image forming apparatus using an electrophotographic method, such as a laser printer or a digital copier. [Background technology]

[0002] Conventionally, for example, according to a scanning optical device described in Patent Document 1, a configuration including a semiconductor laser, a coupling lens, a condenser lens, a deflector, a scanning optical system, a frame, and a cover is known. The semiconductor laser emits laser light. The coupling lens converts light from the semiconductor laser into a beam. The condenser lens condenses the beam from the coupling lens in the sub-scanning direction. The deflector has a rotating polygonal mirror that deflects the beam from the condenser lens in the main scanning direction. The scanning optical system forms an image of the light from the deflector on an image plane. The deflector and scanning optical system are fixed to the frame. The cover covers at least the portion of the frame where the deflector is arranged.

[0003] In this technology, the frame has a first wall with a first opening through which a beam directed toward the rotating polygon mirror passes, and the condenser lens blocks the first opening. With this configuration, the condenser lens blocks the first opening through which a beam directed from the coupling lens toward the rotating polygon mirror passes. This prevents dust near the coupling lens from entering through the opening and suppresses dust from moving toward the rotating polygon mirror and adhering to it. The frame also has a second wall with a second opening through which a beam reflected by the rotating polygon mirror passes, and the scanning lens in the scanning optical system closest to the rotating polygon mirror is configured to block the second opening. With this configuration, it is possible to suppress dust near the scanning optical system from moving toward the rotating polygon mirror and adhering to it. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-083740 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the deflector that drives the rotating polygon mirror includes a driver IC mounted on a drive circuit board, which generates heat when the deflector is driven. In conventional configurations, the space around the deflector is sealed by covering it with a cover, a wall, or a condenser or scanning lens, creating a risk of an increase in the ambient temperature around the deflector. If the temperature around the deflector increases, for example, the resin frame may thermally deform, potentially causing the position of optical components such as lenses and folding mirrors housed within the frame to shift. If the position of the optical components shifts, the position of the light beam irradiated onto the photosensitive drum changes, resulting in misalignment of the light beam on multiple photosensitive drums. This leads to color shifts in color images, which are created by overlaying four color toner images, resulting in reduced image quality.

[0006] The present invention has been made under these circumstances, and has as its object to suppress an increase in the ambient temperature around the deflector and to effectively prevent dust from building up around the deflector. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the present invention has the following configuration.

[0008] (1) A scanning optical device comprising: a plurality of light sources; a deflector having a rotating polygonal mirror for deflecting and scanning laser light emitted from the plurality of light sources in a scanning direction; an optical box having a bottom surface on which the deflector is installed; and a lid member for covering the optical box, wherein the optical box or the lid member has a plurality of openings for emitting each of the plurality of laser light beams to the outside of the scanning optical device; and a wall portion provided between the deflector and one of the plurality of openings that is located closest to the deflector, and the wall portion stands up from the bottom surface or the lid member and extends in the scanning direction.

[0009] (2) A scanning optical device comprising: a plurality of light sources; a deflector having a rotating polygonal mirror for deflecting and scanning laser light emitted from the plurality of light sources in a scanning direction; an optical box having a bottom surface on which the deflector is installed; and a lid member covering the optical box, wherein the optical box or the lid member has a plurality of openings for emitting each of the plurality of laser light beams to the outside of the scanning optical device, and the plurality of openings include a first opening arranged at a position among the plurality of openings closest to the deflector, and a second opening arranged at a position next closest to the deflector after the first opening; a first wall portion standing from the bottom surface or the lid member and provided between the first opening and the deflector; and a second wall portion standing from the bottom surface or the lid member and provided between the second opening and the deflector, wherein the height of the first wall portion is greater than the height of the second wall portion.

[0010] (3) An image forming apparatus comprising: an image carrier that carries an electrostatic latent image; a scanning optical device described in (1) or (2) that forms the electrostatic latent image; a developing means that develops the electrostatic latent image to form a toner image; and a transfer means that transfers the toner image to a recording material. [Effects of the Invention]

[0011] According to the present invention, it is possible to suppress an increase in the ambient temperature around the deflector and to effectively prevent dust from building up around the deflector. [Brief explanation of the drawings]

[0012] [Figure 1] Schematic perspective view showing a scanning optical device according to Examples 1 to 3. [Figure 2] Schematic cross-sectional view showing the oblique incidence optical system of the scanning optical device according to the first to third embodiments. [Figure 3] 1A and 1B are schematic cross-sectional views showing the scanning optical system of the scanning optical device according to Examples 1 to 3, and a schematic cross-sectional view showing the air flow at the opening of the scanning optical device. [Figure 4] 1 is a schematic perspective view showing a simple scanning optical device for simulation of Example 1, and a schematic top view showing a simple lid for simulation. [Figure 5] Schematic top view showing a simple lid for simulation in Example 1. [Figure 6] 1 is a diagram showing the simulation results of Example 1. [Figure 7] 1A and 1B are a schematic perspective view and a schematic cross-sectional view showing a dustproof wall of a scanning optical device according to a first embodiment of the present invention; [Figure 8] FIG. 10 is a diagram showing the temperature rise results of the scanning optical device of Example 1. [Figure 9] 1A and 1B are schematic cross-sectional views showing a scanning optical device according to a modification of the first embodiment and a scanning optical device according to a second embodiment; [Figure 10] Schematic cross-sectional view showing an image forming apparatus according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] The following describes an embodiment of a scanning optical device according to the present invention with reference to the drawings. However, the dimensions, materials, shapes, and relative positions of the components described in the embodiment may be changed as appropriate depending on the configuration and various conditions of the device to which the invention is applied, and the scope of the invention is not limited to the following embodiment. [Example]

[0014] A first embodiment of the scanning optical device according to the present invention will be specifically described with reference to the drawings.

[0015] (scanning optical device) FIG. 1 is a schematic perspective view illustrating a scanning optical device 1. In the scanning optical device 1 of the first embodiment, laser beams L1, L2, L3, and L4 emitted from a plurality of semiconductor lasers 111, which are light sources, are scanned by a rotating polygon mirror 103 included in a deflector 104. The scanned laser beams L1, L2, L3, and L4 are irradiated onto a photosensitive drum of an image forming device (not shown) via optical members. The scanning optical device 1 includes the deflector 104 having the rotating polygon mirror 103. The scanning optical device 1 includes a first imaging lens 116, second imaging lenses 120a and 120b, a BD lens 126, and reflecting members (folding mirrors) including a first reflecting mirror 117, a second reflecting mirror 118, and a third reflecting mirror 119, which are laser beam imaging members. The scanning optical device 1 further includes an optical box 101 to mount these members. Laser beams L1, L2, L3, and L4 emitted from the semiconductor laser 111 are converged by an anamorphic lens 113, which is an integrally molded collimator lens and cylindrical lens. The beam widths of the laser beams L1, L2, L3, and L4 are then limited by a sub-scanning aperture stop and a main-scanning aperture stop (not shown), forming linear images with a constant width on the deflection-reflection surface of the rotating polygon mirror 103. Laser control boards 124 and 125 are equipped with chips that control the semiconductor laser 111. A beam detector (hereinafter referred to as BD) 127 is mounted on the laser control board 125. The deflector 104 rotates around a rotation axis CZ, reflects the laser beam L4 off the rotating polygon mirror 103, deflects it, and scans it. After passing through a BD lens 126, the beam detector 127 enters the BD lens 127. At this time, the writing of images for each color is controlled based on a signal (BD signal) output from the BD lens 127.

[0016] Unlike the laser beam that scans a photosensitive drum (not shown), a stray light prevention wall 132 is provided to prevent unwanted light generated by refraction or reflection of the laser beam by a lens or the like from reaching the photosensitive drum and causing image defects. The stray light prevention wall 132 is provided between the first imaging lens 116 and the deflector 104, and its length and height are minimized to a necessary and sufficient size to suppress an increase in ambient temperature due to the rotational drive of the deflector 104. Note that the direction parallel to the rotation axis CZ is the Z direction, the direction in which the laser beam is scanned by the rotating polygon mirror 103, in other words, the longitudinal direction of the lens or mirror, is the X direction, and the direction perpendicular to the X and Z directions is the Y direction. The dustproof wall 131 will be described later.

[0017] (Oblique incidence optical system) 2 is a schematic cross-sectional view illustrating the oblique incidence optical system of the scanning optical device 1. The oblique incidence optical system is an optical system that makes laser beams L1 and L2 incident obliquely onto face D of the rotating polygon mirror 103. Incident optical systems consisting of semiconductor lasers 111a and 111b and an anamorphic lens 113 are arranged symmetrically above and below with respect to axis B that is perpendicular to the rotation axis CZ. Of the multiple light sources, semiconductor laser 111a is a first light source that is tilted at a desired angle θ with respect to axis B. Laser beam L2 emitted from semiconductor laser 111a is incident on face D of the rotating polygon mirror 103 from above at an angle θ.

[0018] On the other hand, the semiconductor laser 111b is a second light source disposed at a desired angle θ with respect to the axis B. The laser beam L1 emitted from the semiconductor laser 111b is incident on the surface D of the rotating polygon mirror 103 from the obliquely lower side at the angle θ. In this way, by making the laser beams L2 and L1 from the upper and lower semiconductor lasers 111a and 111b incident on the surface D from the obliquely upper and lower sides, respectively, the laser beams L2 and L1 can be separated into upper and lower optical paths after being reflected by the rotating polygon mirror 103. In the first embodiment, the oblique incidence optical system has been described using the laser beams L1 and L2, but the incidence optical system including the light sources emitting the laser beams L3 and L4 shown in FIG. 1 has a similar configuration.

[0019] (scanning optical system) Next, with reference to Fig. 3(a), a description will be given of the scanning optical system after the laser beams L1, L2, L3, and L4 of Example 1 are reflected by the rotary polygon mirror 103. Fig. 3(a) is a sub-scanning cross-sectional view of the scanning optical system, showing the optical paths of the laser beams L1, L2, L3, and L4 deflected and scanned by the rotary polygon mirror 103 until they reach the photosensitive drums 11a, 11b, 11c, and 11d.

[0020] The scanning optical device 1 deflects and scans laser beams L1, L2, L3, and L4 emitted from multiple light sources (not shown) by using a rotating polygon mirror 103 to distribute the beams to a scanning area A1 and a scanning area A2 on the opposite side of the scanning area A1 from the center of a rotation axis CZ of the rotating polygon mirror 103. Because the scanning optical device 1 is an oblique incidence optical system, the laser beams L1 and L3 are reflected downward and the laser beams L2 and L4 are reflected upward by the rotating polygon mirror 103 in the Z direction. The laser beams L1, L2, L3, and L4 then enter a first imaging lens 116. The laser beams L2 and L3 are reflected by a first reflecting mirror 117. After passing through a second imaging lens 120a, they are reflected again by a second reflecting mirror 118 and pass through openings H2 and H3 provided in a cover 102 serving as a cover member to reach photosensitive drums 11b and 11c.

[0021] Furthermore, the laser beams L1 and L4 pass through the second imaging lens 120b, are reflected by the third reflecting mirror 119, and pass through openings H1 and H4 provided in the lid 102 before reaching the photosensitive drums 11a and 11d. The first imaging lens 116 is a common lens for the laser beams L1 and L2 and the laser beams L3 and L4, respectively, and the second imaging lens 120a is arranged as a common lens for the laser beams L2 and L3, and the second imaging lens 120b is arranged as a common lens for the laser beams L1 and L4, respectively. Each imaging lens is fixed to the optical box 101 by an ultraviolet-curing adhesive, and each reflecting mirror is fixed by a biasing member such as a leaf spring (not shown). The lid 102 is attached to the optical box 101 by screws (not shown).

[0022] The deflector 104 having the rotating polygon mirror 103 is disposed horizontally closer to the photosensitive drum 11c than the midpoint CH between the two photosensitive drums 11b and 11c. Here, the horizontal direction refers to the direction of a straight line Y1 connecting the rotation centers of the two farthest photosensitive drums, 11a and 11d, among the four photosensitive drums. The deflector 104 is disposed closer to the photosensitive drum 11c than the midpoint CH between the two photosensitive drums 11b and 11c, and the laser beams L1, L2, L3, and L4 are obliquely incident on the photosensitive drums 11a, 11b, 11c, and 11d. This allows for wide spaces T1, T2, T3, and T4 to be left of each photosensitive drum 11a, 11b, 11c, and 11d in the figure. As a result, the toner cartridge (not shown) can place the toner containers in the spaces T1, T2, T3, and T4, and fill the toner containers with a sufficient amount of toner.

[0023] (Airflow and volume at openings) Next, the airflow and air volume at the openings of the scanning optical device 1 will be described using FIG. 3(b). FIG. 3(b) is a sub-scanning cross-sectional view of the scanning optical device 1. The lid 102 has openings H1, H2, H3, and H4 through which the laser beams L1, L2, L3, and L4 pass. When the deflector 104 of the scanning optical device 1 rotates around the rotation axis CZ, the scanning optical device 1 draws outside air into the scanning optical device 1 through the openings H2 and H3, which are positioned relatively close to the deflector 104, and generates airflows K2 and K3 toward the rotating polygon mirror 103 of the deflector 104. In the Y direction, the opening H3 is positioned closer to the deflector 104 than the opening H2. Therefore, the opening H3 is more susceptible to the rotation of the deflector 104 and the rotating polygon mirror 103 than the opening H2, and the airflow K3 flowing in from the opening H3 has a larger air volume than the airflow K2 flowing in from the opening H2. Furthermore, at the openings H1 and H4, air is expelled from the inside of the scanning optical device 1 to the outside by the rotational drive of the deflector 104, generating airflows K1 and K4. When the image forming apparatus is used in an environment where the air contains a lot of dust, the dust flows into the scanning optical device 1 through the openings H2 and H3 of the scanning optical device 1.

[0024] (Regarding Simulation) Next, the research results (Research 1) of the inventors are shown. In the simulation, the following has been found. That is, when relatively comparing the opening close to the deflector 104 and the opening far from it in the scanning optical device 1, the air volume flowing into the opening close to the deflector 104 is larger, and the air volume flowing into the opening far from the deflector 104 is smaller.

[0025] Fig. 4(a) shows a simple scanning optical device used in the simulation. The simple scanning optical device 51 disposes a deflector 54 at approximately the center of a substantially square optical box 61 and seals the optical box 61 with a lid (not shown). In the simulation, in order to make the airflow visible, with no optical components such as lenses and folding mirrors, three types of lids were attached to the optical box, and the air volume of the airflow at the openings in each lid was analyzed.

[0026] Figs. 4(b) to 5(b) show top views of the simple lids used in the simulation as seen from above. Fig. 4(b) shows a state in which the opening of the optical box 61 is covered with a lid 65 having openings H61, H62, H63, and H64. Since the deflector 54 is actually not visible because the lid 65 is covering the optical box 61, it is shown by a dashed line in the figure, and the same applies in Fig. 5. Fig. 4(b) arranges the deflector 54 approximately at the center of the openings H62 and H63 in the X direction. Also, the openings H62 and H63 provided in the lid 65 are arranged at distances U1 and U2 from the rotation axis CZ1 of the deflector 54 in the Y direction respectively (Simulation 1), and U1 = U2.

[0027] Fig. 5(a) shows a state in which the opening of the optical box 61 is covered with a lid 75 having openings H71, H72, H73, and H74. Fig. 5(a) arranges the deflector 54 approximately at the center of the openings H72 and H73 in the X direction. Also, the openings H72 and H73 provided in the lid 75 are arranged at distances V1 and V2 from the rotation axis CZ1 of the deflector 54 in the Y direction respectively (Simulation 2), and V1 < V2. That is, the opening H72 is closer to the deflector 54 than the opening H73.

[0028] Figure 5(b) shows a state where the opening of the optical box 61 is covered with a lid 85 having openings H81, H82, H83, and H84. In Figure 5(b), in the X direction, the deflector 54 is arranged approximately at the center between the openings H82 and H83. Further, the openings H82 and H83 provided in the lid 85 are arranged at distances W1 and W2, respectively, from the rotation axis CZ1 of the deflector 54 in the Y direction (simulation 3), and W1 > W2. That is, the opening H83 is closer to the deflector 54 than the opening H82.

[0029] In simulations 1 to 3, all the openings are arranged so that the intervals between them are the same. In the Y direction, including the two openings H61, H64, H71, H74, H81, and H84 arranged away from the deflector 54, the intervals between all the openings are set such that U1 + U2 = V1 + V2 = W1 + W2.

[0030] (Results of simulation) The simulation results are shown in Figure 6. Figure 6 shows the air volume [m 3 / min] at the openings of the lid, and the + side of the vertical axis represents the air flow direction flowing from the outside to the inside of the scanning optical device. In Figure 6, the left graph shows the openings H62, H72, and H82 through which the laser beam L2 passes, and the distances from the rotation axis CZ1 in the Y direction are U1, V1, and W1, respectively. The right graph shows the openings H63, H73, and H83 through which the laser beam L3 passes, and the distances from the rotation axis CZ1 in the Y direction are U2, V2, and W2, respectively.

[0031] In simulation 1 (Figure 4(b)), since the distances U1 and U'2 of the openings H62 and H63 from the rotation axis CZ1 of the deflector 54 are arranged at the same distance U1 = U2, the air volumes at the openings H62 and H63 are the same. Also, in simulation 2 (Figure 5(a)), since the distances V1 and V2 of the openings H72 and H73 from the rotation axis CZ1 of the deflector 54 are arranged such that V1 < V2, the air volume of the opening H72 closer to the rotation axis CZ1 is larger than the air volume of the opening H73. In addition, in simulation 3 (Figure 5(b)), the openings H82 and H83 are positioned such that the distances W1 and W2 from the rotation axis CZ1 of the deflector 54 are W1 > W2, so the air volume at opening H82, which is far from the rotation axis CZ1, is smaller than the air volume at opening H83.

[0032] The results of the above simulation reveal the following: Of the four openings provided in the scanning optical device, the opening closer to deflector 104, and the two openings located near deflector 104, have a larger amount of airflow flowing into the scanning optical device than the opening farther away.

[0033] (Dustproof wall) FIG. 7(a) shows a perspective view of the lid illustrating the dustproof wall, and FIG. 7(b) shows a schematic cross-sectional view of the scanning optical device 1, in which the dustproof wall is viewed from the deflector 104 side. An airflow containing dust and other particles enters the scanning optical device 1 through openings H2 and H3 in the lid 102. As shown in FIG. 7(a), in the first embodiment, in order to effectively reduce the amount of dust reaching the rotating polygon mirror 103 of the deflector 104, the lid 102 has a dustproof wall 130 as a wall portion near the opening H3, which is closest to the deflector 104 in the Y direction. More specifically, the dustproof wall 130 is provided between the opening H3 and the deflector 104 in a direction perpendicular to the scanning direction and close to the opening H3. The dustproof wall 130 provided on the lid 102 is provided upright (standing) toward the optical box 101, parallel to the X direction, which is the longitudinal direction of the opening H3.

[0034] Here, opening H2 is farther from deflector 104 in the Y direction than opening H3, and the air volume of opening H2 is smaller than that of opening H3. For this reason, a dustproof wall may not be provided near opening H2, or a small standing wall that is smaller than dustproof wall 130 on the opening H3 side and does not affect the inflow and outflow of airflow at the opening may be provided.

[0035] 7(b), the dustproof wall 130 (second wall portion) of the lid 102 extends to a position where it does not interfere with the dustproof wall 131 (first wall portion) standing up from the bottom surface 101b of the optical box 101. The dustproof wall 131 provided on the optical box 101 is provided parallel to the X direction, and dustproof wall 131a and dustproof wall 131b are provided with different heights in the Z direction. Therefore, the dustproof wall is formed by the dustproof wall 130 provided on the lid 102 and the dustproof wall 131 provided on the optical box 101, and the combined length of the dustproof wall 130 and the dustproof wall 131 in the X direction is approximately the same as the length of the opening H3. Note that the combined length of the dustproof wall 130 and the dustproof wall 131 may be longer than the length of the opening H3.

[0036] However, there are areas where the dustproof wall is discontinued in the area through which the laser light (not shown) passes within the scanning optical device 1. For example, there are no dustproof walls at light ray passing section 140 through which the laser light is reflected by the rotating polygon mirror 103 of the deflector 104, scanned, and enters the first imaging lens, and at light ray passing section 141 through which the laser light enters the BD lens 126, because the laser light is not blocked. Note that light ray passing section 140 is an opening provided in dustproof wall 131a.

[0037] In the first embodiment, the dustproof wall between the opening and the rotating polygon mirror is described as being configured with two dustproof walls, one on the lid and one on the optical box. However, the dustproof wall may be configured only on the lid, or may be configured only on the optical box. That is, in FIG. 7, the dustproof wall 130 and the dustproof wall 131 are combined to form a single dustproof wall, but this is not limiting. The dustproof wall 130 alone may be configured as a dustproof wall having the same or longer length as the opening H3 in the scanning direction, or the dustproof wall 131 alone may be configured as a dustproof wall having the same or longer length as the opening H3 in the scanning direction. Furthermore, in FIG. 7, the dustproof wall 131 is configured as two dustproof walls 131a and 131b having different heights, but it may be configured as three or more dustproof walls. Furthermore, the dustproof wall 130 may also be configured as a plurality of dustproof walls having different heights. Furthermore, the dustproof wall provided on the lid and the dustproof wall provided on the optical box do not have to be disposed at the same position in the Y direction in FIG. 7(a), and may be disposed at different positions.

[0038] As described above, according to the first embodiment, there is a risk that the airflow flowing in from the opening H2 side in FIG. 7(a) may reach the rotating polygon mirror of the deflector (not shown). However, because the airflow volume is smaller on the opening H2 side than on the opening H3 side, the risk of the rotating polygon mirror becoming soiled by dust is lower than on the opening H3 side. Therefore, by providing a dustproof wall near the opening close to the deflector, where the risk is higher, it is possible to effectively prevent dust from entering.

[0039] (Temperature rise of scanning optical device) As shown in FIG. 7A and other figures, the dustproof wall 130 is provided only near the opening H3, which is closest to the deflector 104. The opening H2, which is farther away from the deflector 104 in the Y direction than the opening H3, may not be provided with a dustproof wall, or a small vertical wall smaller than the dustproof wall 130 on the opening H3 side and small enough not to affect the inflow and outflow of airflow through the opening may be provided. However, if a vertical wall is provided on the opening H2 side, the height and length of the vertical wall are set to any desired shape, taking into consideration the balance between the air volume through the opening and the increase in the ambient temperature around the deflector. Furthermore, a stray light prevention wall 132, as shown in FIG. 1, is provided on the opening H2 side. Unlike the laser light that scans the photosensitive drum 11, the scanning optical device 1 generates unwanted light due to the refraction or reflection of the laser light by a lens or the like, which may reach the photosensitive drum 11 and cause image defects. The stray light prevention wall 132 is configured to prevent unnecessary light from reaching the photosensitive drum 11, and its length and height are minimized, unlike the dustproof wall provided on the opening H2 side.

[0040] Next, the inventors' study results (Study 2) are presented. The deflector of the scanning optical device was continuously driven, and the ambient temperature around the deflector was measured. The results were compared between a configuration in which dustproof walls were placed only near the opening closest to the deflector and a configuration in which dustproof walls were placed near both of the two openings located across the deflector. It was found that the configuration in which dustproof walls were placed only near the opening closest to the deflector was more effective at reducing the ambient temperature around the deflector.

[0041] Figure 8 shows the results of measuring the ambient temperature around the deflector of the scanning optical device when the deflector was continuously driven. In Figure 8, the vertical axis represents temperature rise [°C], and the horizontal axis represents drive time [min]. In Figure 8, the thick solid line represents the temperature rise when a dustproof wall is provided only on the opening side close to the deflector, the thin solid line represents the temperature rise when no dustproof wall is provided, and the dashed line represents the temperature rise when dustproof walls similar to dustproof wall 131 are provided on both sides of the deflector.

[0042] When the deflector was operated continuously for 60 minutes, the ambient temperature around the deflector increased more in a configuration in which dustproof walls were installed on both sides of the two openings straddling the deflector than in a configuration in which dustproof walls were installed only near the opening closest to the deflector. Also, the ambient temperature increase in a configuration in which dustproof walls were installed only near the opening closest to the deflector was the same as in a configuration in which no dustproof walls were installed.

[0043] With this configuration, by providing a dustproof wall on only one side and minimizing the length and height of the stray light prevention wall on the other side, it is possible to suppress an increase in the ambient temperature around the deflector and effectively prevent dust from entering the scanning optical device from the outside air. This also makes it possible to provide a scanning optical device that can suppress temperature increases and has dustproof performance, preventing a decrease in image quality.

[0044] (Variation) In the above-described embodiment, an opening is provided in the lid, and a dustproof wall is used to prevent the airflow entering through the opening in the lid from reaching the rotating polygon mirror. However, the present invention is not limited to this, and an opening may be provided in the optical box. Figure 9(a) is a schematic sub-scanning sectional view illustrating a modification of the first embodiment.

[0045] The scanning optical device 30 distributes and deflects laser beams L21, L22, L23, and L24 emitted from a plurality of light sources (not shown) by a rotating polygon mirror 203 to a scanning area A21 and a scanning area A22 on the opposite side of the scanning area A21 from the center of a rotation axis CZ2 of the rotating polygon mirror 203. Because of the oblique incidence optical system, the laser beams L21 and L23 are reflected downward and the laser beams L22 and L24 are reflected upward by the rotating polygon mirror 203 in the Z direction.

[0046] The laser beams L21, L22, L23, and L24 then enter the first imaging lens 216. The laser beams L22 and L23 are reflected by the first reflecting mirror 217. After passing through the second imaging lens 220a, they are reflected again by the second reflecting mirror 218, pass through openings H22 and H23 provided in the optical box 201, and reach the photosensitive drums 21b and 21c. Furthermore, the laser beams L21 and L24 pass through the second imaging lens 220b, are reflected by the third reflecting mirror 219, and pass through openings H21 and H24 provided in the optical box 201, before reaching the photosensitive drums 21a and 21d.

[0047] The first imaging lens 216 is a common lens for the laser beams L21, L22, L23, and L24. The second imaging lens 220a is a common lens for the laser beams L22 and L23, and the second imaging lens 220b is a common lens for the laser beams L21 and L24. Each imaging lens is fixed to the optical box 201 with an ultraviolet-curing adhesive, and each reflecting mirror is fixed with a biasing member such as a leaf spring (not shown). The lid 202 is attached to the optical box 201 with screws (not shown). A deflector 204 having a rotating polygonal mirror 203 is disposed at a position closer to the photosensitive drum 21b than the midpoint CH2 between the two photosensitive drums 21b and 21c in the horizontal direction. Here, the horizontal direction refers to the direction of a straight line Y2 connecting the rotation centers of the two photosensitive drums, 21a and 21d, which are the farthest apart among the four photosensitive drums.

[0048] In this modification, in order to effectively reduce the amount of dust that reaches the rotating polygon mirror 203 of the deflector 204 due to the airflow containing dust and the like entering the scanning optical device 30 through the openings H22 and H23 of the optical box 201, the optical box 201 is configured as follows: That is, the optical box 201 is provided with a dustproof wall 230 in the vicinity of the opening H22, which is closest to the deflector 204 in the Y direction.

[0049] Dustproof wall 230 provided on optical box 201 is arranged parallel to the longitudinal direction of opening H22 and stands upright from bottom surface 201a of optical box 201 toward lid 202. Opening H23 is farther away from deflector 204 than opening H22, and therefore the air volume at opening H23 is smaller than opening H22. For this reason, a dustproof wall need not be provided near opening H23, or a small standing wall that is smaller than dustproof wall 230 on the opening H22 side and does not affect the flow of air in and out of opening H23 may be provided.

[0050] In the modified example, the dustproof wall 230 provided between the opening H22 and the rotating polygon mirror 203 is provided only on the optical box 201. However, the configuration may include two dustproof walls, one standing from the optical box 201 and the other standing from the lid, or the dustproof wall may be provided only on the lid side.

[0051] As described above, according to the modified example, although the airflow flowing in from the opening H23 side may reach the rotating polygon mirror 203 of the deflector 204, the airflow volume is smaller than that from the opening H22 side. Therefore, the risk of the rotating polygon mirror 203 becoming contaminated by dust is lower than that from the opening H22 side. Therefore, by providing a dustproof wall near the opening close to the deflector, where the risk is higher, it is possible to effectively prevent the inflow of dust from the outside air. Furthermore, without covering the periphery of the deflector of the scanning optical device with a dustproof wall, it is possible to prevent heat from being trapped in the space and suppress temperature rise. This makes it possible to provide a scanning optical device that can simultaneously suppress temperature rise and improve dustproof performance of the scanning optical device, thereby preventing degradation of image quality.

[0052] As described above, according to the first embodiment, it is possible to suppress an increase in the ambient temperature around the deflector and to effectively prevent dust from building up around the deflector. [Example]

[0053] Fig. 9(b) is a schematic sub-scanning cross-sectional view for explaining Example 2. Scanning optical device 31 is a scanning optical device in which the optical box is changed from that of scanning optical device 30 shown in Fig. 9(a). The deflector equipped with a rotating polygonal mirror, the imaging lens, and the folding mirror contained in optical box 301 have the same configuration as those of scanning optical device 30 of Example 1 explained using Fig. 9(a). Therefore, a description of the internal configuration of scanning optical device 31 will be omitted, and the same components as those in Fig. 9(a) will be denoted by the same reference numerals as in Fig. 9(a).

[0054] (Dustproof wall of Example 2) In the second embodiment, an airflow containing dust and the like enters the scanning optical device 31 through the openings H32 and H33 among the four openings H31, H32, H33, and H34 of the optical box 301, and the amount of dust that reaches the rotating polygon mirror 203 of the deflector 204 is effectively reduced. For this reason, the optical box 301 is provided with a first dustproof wall 330 (first wall portion) near the opening H32, which is the first opening that is closest to the deflector 204 in the Y direction. The first dustproof wall 330 provided on the optical box 301 is disposed parallel to the longitudinal direction of the opening H32 and stands upright from the bottom surface 301a of the optical box 301 toward the lid 202. The first dustproof wall 330 is provided between the opening H32 and the deflector 204 in the direction perpendicular to the scanning direction, and at a position closer to the opening H32.

[0055] A second dustproof wall 340 (second wall portion) is provided near an opening H33, which serves as a second opening and is located at a position next closest to the deflector 304 in the Y direction after the first dustproof wall 330. The second dustproof wall 340 provided in the optical box 301 is arranged parallel to the longitudinal direction of the opening H33 and stands upright from the bottom surface 301a of the optical box 301 toward the lid 302. The second dustproof wall 340 is provided between the opening H33 and the deflector 204 in the direction perpendicular to the scanning direction, and at a position closer to the opening H33.

[0056] Since the distance of the opening H33 from the deflector 304 is farther than that of the opening H32, the air volume of the opening H33 is smaller than that of the opening H32. Therefore, the height Ht2 of the second dust-proof wall 340 provided near the opening H33 is set lower than the height Ht1 of the first dust-proof wall 330 near the opening H32 (Ht2 < Ht1). Thus, on the side of the opening H33, the second dust-proof wall 340, which is a low vertical wall such that the temperature rise of the atmosphere around the deflector 304 generated by the rotational drive of the deflector 304 does not increase significantly, is provided.

[0057] In the second embodiment, although the dust-proof wall provided between the opening and the rotating polyhedron mirror has been described for the configuration provided only on the optical box, as shown in FIG. 7 of the first embodiment, it may also be a configuration of two dust-proof walls, namely, the wall provided on the optical box and the dust-proof wall provided on the lid. That is, the first dust-proof wall 330 may include a third wall portion extending from the optical box 301 toward the lid 202 and a fourth wall portion extending from the lid 202 toward the bottom surface 301a. And / or, the second dust-proof wall 340 may include a fifth wall portion extending from the optical box 301 toward the lid 202 and a sixth wall portion extending from the lid 202 toward the bottom surface 301a. When providing the fifth wall portion and the sixth wall portion, the temperature rise of the atmosphere is set to such an extent that it does not increase significantly. Further, each of the third wall portion, the fourth wall portion, the fifth wall portion, and the sixth wall portion may be composed of a plurality of wall portions like the dust-proof walls 131a and 131b in FIG. 7. Also, the dust-proof wall may be provided only on the lid side. Note that the length of the first dust-proof wall 330 in the scanning direction is the same as or longer than the length of the opening H32 in the scanning direction.

[0058] As described above, in the second embodiment, the airflow flowing in from the opening H33 side may reach the rotating polygon mirror 303 of the deflector 304. However, because the airflow volume is smaller on the opening H33 side than on the opening H32 side, the risk of the rotating polygon mirror 303 being contaminated by dust is lower than on the opening H32 side. Therefore, by providing a relatively large first dustproof wall 330 on the opening H32 side, which is closer to the deflector 304 and where the risk is higher, it is possible to effectively prevent the inflow of dust. Furthermore, the heights of the first dustproof wall 330 provided near the opening H33 and the second dustproof wall 340 provided near the opening H32 at a height lower than that of the first dustproof wall 330 are optimized. This allows for a balance between the amount of dust flowing into the scanning optical device 31 and the increase in the ambient temperature around the deflector caused by the deflector operating. For example, if the second dustproof wall 340 is made taller, dust can be further reduced, and if the second dustproof wall 340 is made shorter, it can prevent a large increase in the ambient temperature around the deflector 204 caused by driving the deflector 204. This makes it possible to provide a scanning optical device that can improve image quality while suppressing temperature increases and improving dustproofing performance of the scanning optical device, and thereby achieving a balance between temperature increases and dustproofing.

[0059] As described above, according to the second embodiment, it is possible to suppress an increase in the ambient temperature around the deflector and to effectively prevent dust from building up around the deflector. [Example]

[0060] (Image forming device overview) FIG. 1 is a schematic cross-sectional view of an image forming apparatus 2 according to a first embodiment. The image forming apparatus 2 according to the first embodiment is a color image forming apparatus that forms a full-color image by superimposing four colors: yellow, cyan, magenta, and black. Next, the image forming process will be described. The process cartridges PY, PM, PC, and PK, each corresponding to a different color, are equipped with photosensitive drums 11a, 11b, 11c, and 11d as image carriers, charging rollers 12a, 12b, 12c, and 12d as chargers, and developing rollers 13a, 13b, 13c, and 13d as developers. The process cartridges PY, PM, PC, and PK may also be collectively referred to as process cartridges P. Regarding the components of each process cartridge P, a represents yellow, b represents magenta, c represents cyan, and d represents black. Hereinafter, the components a to d within the process cartridge P will also be omitted unless a specific color is being described. The same applies to the primary transfer roller 22, which will be described later.

[0061] The photosensitive drum 11, which has been pre-charged by the charging roller 12, is irradiated with laser beams L1, L2, L3, and L4 emitted from the scanning optical device 1, which serves as an exposure device, to form an electrostatic latent image on its surface. The electrostatic latent image is converted into a toner image by the developing roller 13, which serves as a developing means, and the toner image on the photosensitive drum 11 is transferred onto the intermediate transfer belt 41 by the primary transfer roller 22 (primary transfer). Meanwhile, a recording sheet S, which serves as a recording material and is placed in a paper cassette 42 located below the intermediate transfer belt 41, is picked up by the pickup roller 32 in synchronization with the image formation process. The conveyed recording sheet S is then transferred with the four-color toner image on the intermediate transfer belt 41 by the secondary transfer roller 33, which serves as a transfer means (secondary transfer). Finally, the recording sheet S passes through a fixing device 34, where the unfixed toner image is fixed, and the recording sheet S is discharged by discharge rollers 35 and 36 to a discharge tray 37 outside the image forming apparatus 2.

[0062] As described above, according to the third embodiment, it is possible to suppress an increase in the ambient temperature around the deflector and to effectively prevent dust from building up around the deflector.

[0063] The disclosure of this embodiment includes the following configuration. (Configuration 1) Multiple light sources; a deflector having a rotary polygonal mirror for deflecting and scanning the laser beams emitted from the plurality of light sources in a scanning direction; an optical box having a bottom surface on which the deflector is installed; a cover member for covering the optical box; A scanning optical device comprising: the optical box or the cover member has a plurality of openings for emitting each of the plurality of laser beams to the outside of the scanning optical device, a wall portion provided between the deflector and an opening portion of the plurality of opening portions that is located closest to the deflector, The wall portion stands upright from the bottom surface or the cover member and extends in the scanning direction. (Configuration 2) The scanning optical device described in configuration 1, characterized in that the wall portion includes a first wall portion extending from the optical box toward the lid member and a second wall portion extending from the lid member toward the bottom surface. (Configuration 3) 3. The scanning optical device according to configuration 2, wherein the first wall portion and / or the second wall portion includes a plurality of wall portions having different heights in the standing direction. (Configuration 4) 4. The scanning optical device of any one of configurations 1 to 3, wherein the length of the wall portion in the scanning direction is the same as or longer than the length of the opening in the scanning direction. (Configuration 5) Multiple light sources; a deflector having a rotary polygonal mirror for deflecting and scanning the laser beams emitted from the plurality of light sources in a scanning direction; an optical box having a bottom surface on which the deflector is installed; a cover member for covering the optical box; A scanning optical device comprising: the optical box or the cover member has a plurality of openings for emitting each of the plurality of laser beams to the outside of the scanning optical device, the plurality of openings include a first opening arranged at a position closest to the deflector among the plurality of openings, and a second opening arranged at a position next closest to the deflector after the first opening, a first wall portion standing from the bottom surface or the lid member and provided between the first opening and the deflector; a second wall portion standing from the bottom surface or the lid member and provided between the second opening and the deflector; Equipped with A scanning optical device, wherein the height of the first wall portion is greater than the height of the second wall portion. (Configuration 6) the first wall portion includes a third wall portion extending from the optical box toward the lid member and a fourth wall portion extending from the lid member toward the bottom surface; and / or The scanning optical device described in configuration 5, wherein the second wall portion includes a fifth wall portion extending from the optical box toward the lid member and a sixth wall portion extending from the lid member toward the bottom surface. (Configuration 7) The scanning optical device of configuration 6, wherein the third wall portion, the fourth wall portion, the fifth wall portion and / or the sixth wall portion include a plurality of wall portions having different heights in the upright direction. (Configuration 8) 8. The scanning optical device of any one of configurations 5 to 7, wherein the length of the first wall portion in the scanning direction is the same as or longer than the length of the opening in the scanning direction. (Configuration 9) an image carrier that carries an electrostatic latent image; a scanning optical device according to any one of configurations 1 to 8 for forming the electrostatic latent image; a developing means for developing the electrostatic latent image to form a toner image; a transfer means for transferring the toner image onto a recording material; An image forming apparatus comprising: [Explanation of symbols]

[0064] 1. Scanning optical device 101 Optical box 102 Lid 103 Rotating polygonal mirror 104 Deflector 111 Semiconductor laser 130 Dustproof Wall H3 opening

Claims

1. Multiple light sources; a deflector having a rotary polygonal mirror for deflecting and scanning the laser beams emitted from the plurality of light sources in a scanning direction; an optical box having a bottom surface on which the deflector is installed; a cover member for covering the optical box; A scanning optical device comprising: the optical box or the cover member has a plurality of openings for emitting each of the plurality of laser beams to the outside of the scanning optical device, a wall portion provided between the deflector and an opening portion of the plurality of opening portions that is located closest to the deflector, The wall portion stands upright from the bottom surface or the cover member and extends in the scanning direction.

2. 2. The scanning optical device according to claim 1, wherein the wall portion includes a first wall portion extending from the optical box toward the lid member, and a second wall portion extending from the lid member toward the bottom surface.

3. 3. The scanning optical device according to claim 2, wherein the first wall portion and / or the second wall portion includes a plurality of wall portions having different heights in the standing direction.

4. 2. The scanning optical device according to claim 1, wherein the length of the wall portion in the scanning direction is the same as or longer than the length of the opening in the scanning direction.

5. Multiple light sources; a deflector having a rotary polygonal mirror for deflecting and scanning the laser beams emitted from the plurality of light sources in a scanning direction; an optical box having a bottom surface on which the deflector is installed; a cover member for covering the optical box; A scanning optical device comprising: the optical box or the cover member has a plurality of openings for emitting each of the plurality of laser beams to the outside of the scanning optical device, the plurality of openings include a first opening arranged at a position closest to the deflector among the plurality of openings, and a second opening arranged at a position next closest to the deflector after the first opening, a first wall portion standing from the bottom surface or the lid member and provided between the first opening and the deflector; a second wall portion standing from the bottom surface or the lid member and provided between the second opening and the deflector; Equipped with A scanning optical device, wherein the height of the first wall portion is greater than the height of the second wall portion.

6. the first wall portion includes a third wall portion extending from the optical box toward the lid member and a fourth wall portion extending from the lid member toward the bottom surface; and / or 6. The scanning optical device according to claim 5, wherein the second wall portion includes a fifth wall portion extending from the optical box toward the lid member, and a sixth wall portion extending from the lid member toward the bottom surface.

7. 7. The scanning optical device according to claim 6, wherein the third wall portion, the fourth wall portion, the fifth wall portion, and / or the sixth wall portion includes a plurality of wall portions having different heights in the upright direction.

8. 6. The scanning optical device according to claim 5, wherein the length of the first wall portion in the scanning direction is the same as or longer than the length of the opening in the scanning direction.

9. an image carrier that carries an electrostatic latent image; a scanning optical device according to any one of claims 1 to 8, which forms the electrostatic latent image; a developing means for developing the electrostatic latent image to form a toner image; a transfer means for transferring the toner image onto a recording material; An image forming apparatus comprising:

Images