WO2021240977A1 - Polygon mirror, optical deflector, optical scanning device, image forming device, die, and method for manufacturing resin body - Google Patents

Abstract

A polygon mirror comprising: a prismatic resin body (30) including a first bottom surface (301), a second bottom surface (302), and a plurality of side surfaces (351, 352, 353, 354); and reflecting films provided to each of the plurality of side surfaces (351, 352, 353, 354), the first bottom surface (301) having a first flat surface (310) having a polygonal external form, and at least one first groove (311) which is recessed with respect to the first flat surface (310) and which extends along the first side surface (351) from among the plurality of side surfaces (351, 352, 353, 354), and the first groove (311) being positioned so as not to intersect with diagonals (L11, L12) of the first flat surface (310).

Description

Method for manufacturing polygon mirror, light deflector, light scanning device, image forming device, mold, and resin body

The present invention relates to a polygon mirror.

An optical scanning device used in an image forming apparatus such as a laser printer photomodulates a laser beam emitted from a light source in response to an image signal, and deflects and scans the photomodulated laser beam with an optical deflector having a polygon mirror. .. The laser beam scanned by the optical deflector is imaged on a photosensitive drum, which is an example of an image carrier, by a scanning lens such as an fθ lens. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum. The electrostatic latent image on the photosensitive drum is visualized into a toner image by a developing device, transferred to a sheet such as recording paper, and the toner on the sheet is heated and fixed to form an image on the sheet.

The polygon mirror used in this type of equipment is generally a metal such as aluminum machined into a predetermined shape by a precision processing machine such as a precision lathe.

On the other hand, Patent Document 1 proposes a polygon mirror substrate made of resin. The resin polygon mirror can reduce the cost as compared with the metal polygon mirror, and can give a degree of freedom to the shape.

Japanese Unexamined Patent Publication No. 2019-191335

The resin body, which is the resin substrate in the polygon mirror, is formed by injection molding using a mold. Specifically, the cavity in the mold is filled with the molten resin, the molten resin is cooled and solidified in the mold to form a resin body, and the resin body is separated from the mold. The resin body is formed in the shape of a prism having side surfaces. A reflective film for reflecting light is provided on the side surface of the resin body. Therefore, high shape accuracy is required on the side surface.

According to the first aspect of the present invention, the polygon mirror includes a prismatic resin body including a first bottom surface, a second bottom surface, and a plurality of side surfaces, and a reflective film provided on each of the plurality of side surfaces. The first bottom surface has a first plane having a polygonal outer shape, and at least one first groove that is recessed with respect to the first plane and is along the first side surface of the plurality of side surfaces. The first groove is arranged so as not to intersect the diagonal line of the first plane.

According to the second aspect of the present invention, the mold includes a first bottom surface forming surface, a second bottom surface forming surface, and a plurality of side surface forming surfaces, the first bottom surface forming surface, the second bottom surface forming surface, and the above. It is a mold that defines a prismatic cavity with a plurality of side surface forming surfaces, and the first bottom surface forming surface protrudes from the first plane forming surface having a polygonal outer shape and the first plane forming surface. It has at least one first protruding portion along the first side surface forming surface among the plurality of side surface forming surfaces, and the first protruding portion is arranged so as not to intersect the diagonal line of the first plane forming surface. Has been done.

According to the present invention, the shape accuracy of the side surface of the resin body is improved.
Other features and advantages of the invention will be apparent by the following description with reference to the accompanying drawings. In the attached drawings, the same or similar configurations are given the same reference numbers.

It is sectional drawing which shows the image forming apparatus which concerns on 1st Embodiment. It is a perspective view which shows typically the optical scanning apparatus which concerns on 1st Embodiment. It is sectional drawing of the scanner motor which concerns on 1st Embodiment. It is a perspective view of the resin body in the polygon mirror which concerns on 1st Embodiment. It is a perspective view of the resin body in the polygon mirror which concerns on 1st Embodiment. It is sectional drawing of the resin body which concerns on 1st Embodiment. It is an enlarged view of the main part of the resin body shown in FIG. 4A. It is sectional drawing of the mold which concerns on 1st Embodiment. It is a perspective view of the cavity in the mold which concerns on 1st Embodiment. It is a perspective view of the cavity in the mold which concerns on 1st Embodiment. It is explanatory drawing of the manufacturing method of the resin body in the polygon mirror which concerns on 1st Embodiment. It is explanatory drawing of the manufacturing method of the resin body in the polygon mirror which concerns on 1st Embodiment. It is explanatory drawing of the manufacturing method of the resin body in the polygon mirror which concerns on 1st Embodiment. It is explanatory drawing of the manufacturing method of the resin body in the polygon mirror which concerns on 1st Embodiment. It is explanatory drawing of the manufacturing method of the resin body in the polygon mirror which concerns on 1st Embodiment. It is explanatory drawing of the manufacturing method of the resin body in the polygon mirror which concerns on 1st Embodiment. It is a graph which shows the simulation result which concerns on 1st Embodiment. It is a graph which shows the simulation result which concerns on 1st Embodiment. It is a graph which shows the simulation result which concerns on 1st Embodiment. It is a graph which shows the simulation result which concerns on 1st Embodiment. It is a perspective view of the resin body in the polygon mirror which concerns on 2nd Embodiment. It is a perspective view of the resin body in the polygon mirror which concerns on 2nd Embodiment. It is sectional drawing of the resin body which concerns on 2nd Embodiment. It is an enlarged view of the main part of the resin body shown in FIG. 11A. It is a perspective view of the cavity in the mold which concerns on 2nd Embodiment. It is a perspective view of the cavity in the mold which concerns on 2nd Embodiment. It is a graph which shows the simulation result which concerns on 2nd Embodiment. It is a graph which shows the simulation result which concerns on 2nd Embodiment. It is a graph which shows the simulation result which concerns on 2nd Embodiment. It is a graph which shows the simulation result which concerns on 2nd Embodiment.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.
[First Embodiment]
FIG. 1 is a schematic cross-sectional view showing an image forming apparatus 100 according to the first embodiment. The image forming apparatus 100 is an electrophotographic type. The image forming apparatus 100 of FIG. 1 is a printer, but is not limited to this, and may be a copying machine, a facsimile, a multifunction device, or the like.

The image forming apparatus 100 includes an image forming unit 110 that forms an image on the sheet P which is a recording material. The image forming unit 110 includes an optical scanning device 101, a process cartridge 102, a transfer roller 107 which is an example of a transfer unit, and a fixing device 108. The process cartridge 102 has a photosensitive drum 103, a charging unit 111, and a developing unit 112, which are examples of an image carrier.

The optical scanning device 101 emits a laser beam L based on the obtained image information and irradiates the photosensitive drum 103 of the process cartridge 102 with the laser beam L to scan the surface of the photosensitive drum 103. As a result, a latent image is formed on the photosensitive drum 103, and this latent image is visualized as a toner image by the toner as a developer by the process cartridge 102.

On the other hand, the sheet P loaded on the sheet loading plate 104 is fed while being separated one by one by the feeding roller 105, and is conveyed to the nip portion between the photosensitive drum 103 and the transfer roller 107 by the conveying roller 106. The toner image formed on the photosensitive drum 103 is transferred by the transfer roller 107 onto the sheet P conveyed to the nip portion.

The sheet P to which the unfixed toner image is transferred is further conveyed to the fixing device 108 on the downstream side. The fuser 108 has a heating body inside, and by heating and pressurizing the sheet P, the toner image is fixed to the sheet P as an image. After that, the sheet P is discharged to the outside of the machine by the discharge roller 109.

FIG. 2A is a perspective view schematically showing the optical scanning device 101 according to the first embodiment. The optical scanning device 101 includes a housing 203, a light source 201 supported by the housing 203, a cylindrical lens 202, an fθ lens 205, and a scanner motor 1 which is an example of an optical deflector. An optical diaphragm 204 is formed on the housing 203. The laser beam L emitted from the light source 201 is focused by the cylindrical lens 202 and is limited to a predetermined beam diameter by the optical diaphragm 204.

The laser beam L that has passed through the optical diaphragm 204 is deflected by the scanner motor 1, passes through the fθ lens 205, and then is focused on the photosensitive drum 103 of FIG. 1 to form an electrostatic latent image.

The light source 201, the cylindrical lens 202, the scanner motor 1, etc. are housed in the housing 203. The opening of the housing 203 is closed by an optical lid (not shown) made of resin or metal.

FIG. 2B is a cross-sectional view of the scanner motor 1 according to the first embodiment. FIG. 2B schematically shows a cut surface of the scanner motor 1 obtained by cutting the scanner motor 1 at a surface including a center of rotation. The scanner motor 1 is rotatably supported by a substrate 4 made of sheet metal, a bearing sleeve 5 fixed to the substrate 4, a rotor 7 having a rotor magnet 6, and a bearing sleeve 5, and a rotating shaft 8 integrated with the rotor 7. To prepare for. Further, the scanner motor 1 includes a pedestal 2 integrated with the rotor 7, a stator coil 9 fixed to the substrate 4, and a polygon mirror 3 fixed to the rotating shaft 8 via the pedestal 2. The rotor 7 and the stator coil 9 constitute a motor 10 which is an example of a drive source for rotationally driving the polygon mirror 3. The polygon mirror 3 deflects the laser beam L shown in FIG. 2A by rotating. The polygon mirror 3 has a resin body 30 which is a substrate made of resin, and a reflective film 31 formed on each side surface of the resin body 30.

3A and 3B are perspective views of the resin body 30 in the polygon mirror 3 according to the first embodiment. 3A is a top perspective view of the resin body 30 in the polygon mirror 3, and FIG. 3B is a bottom perspective view of the resin body 30 in the polygon mirror 3. FIG. 4A is a cross-sectional view of the resin body 30 according to the first embodiment. FIG. 4A illustrates a cross section of the resin body 30 along the line IV-IV of FIG. 3A. FIG. 4B is an enlarged view of a main part of the resin body 30 shown in FIG. 4A.

The resin body 30 is a prismatic resin body, and in the first embodiment, it is a square columnar resin body. It is preferable to use a thermoplastic resin as the resin material of the resin body 30. Among the thermoplastic resins, cycloolefin polymers, cycloolefin copolymers, polycarbonates, or acrylics are preferably used. The resin body 30 has a top surface 301 which is a first bottom surface, a bottom surface 302 which is a second bottom surface, and a plurality of side surfaces 351 to 354 in the first embodiment. Each side surface 351 to 354 is a flat surface. Reflective films 31 shown in FIGS. 2A and 2B are provided on each of the side surfaces 351 to 354. One of the plurality of side surfaces 351 to 354, for example, the side surface 351 is the first side surface. In this case, the side surfaces 352 to 354 are any of the second side surface, the third side surface, and the fourth side surface, respectively.

The top surface 301 has a plane 310 which is a first plane. The plane 310 has a polygonal outer shape and has a plurality of sides. In the present embodiment, the plane 310 has a quadrangular outer shape and has four sides S11 to S14.

The bottom surface 302 has a plane 320 which is a second plane. The plane 320 has a polygonal outer shape and has a plurality of sides. In the present embodiment, the plane 320 has a quadrangular outer shape and has four sides S21 to S24 like the plane 310. That is, the outer shape of the plane 310 and the outer shape of the plane 320 are congruent.

The plurality of sides S11 to S14 and S21 to S24 have the same length. Therefore, the outer shape of each of the planes 310 and 320 is a square. The length direction of the sides S11 and S21 is defined as the direction X1. The length direction of the sides S12 and S22 is defined as the direction X2. The length direction of the sides S13 and S23 is defined as the direction X3. The length direction of the sides S14 and S24 is defined as the direction X4. The plane 310 and the plane 320 are parallel. The direction perpendicular to the plane 310 is defined as the direction Z1. Therefore, the direction Z1 is also a direction perpendicular to the plane 320. When viewed in the direction Z1, the side S11 and the side S21 are at the same position as the side surface 351. The side S12 and the side S22 are at the same position as the side surface 352 when viewed in the direction Z1. When viewed in the direction Z1, the side S13 and the side S23 are at the same position as the side surface 353. When viewed in the direction Z1, the side S14 and the side S24 are at the same position as the side surface 354.

Since the plane 310 is a quadrangle, there are two diagonal lines L11 and L12. Since the plane 320 is a quadrangle, there are two diagonal lines L21 and L22. The virtual line C0 passing through the intersection of the two diagonal lines L11 and L12 and the intersection of the two diagonal lines L21 and L22 is the rotation center line of the resin body 30. A columnar through hole 16 is formed at a position including the virtual line C0. That is, the center line of the through hole 16 is the virtual line C0. The rotation shaft 8 shown in FIG. 2B is inserted into the through hole 16.

The top surface 301 has at least one first groove along each side S11 to S14 of the plane 310, which is recessed with respect to the plane 310. At least one first groove along each side S11 to S14 is one first groove in this embodiment. That is, at least one first groove along the side S11 is one groove 311. Further, at least one first groove along the side S12 is one groove 312. Further, at least one first groove along the side S13 is one groove 313. Further, at least one first groove along the side S14 is one groove 314.

The groove 311 is arranged between the through hole 16, that is, the virtual line C0 and the side S11. The groove 312 is arranged between the through hole 16, that is, the virtual line C0 and the side S12. The groove 313 is arranged between the through hole 16, that is, the virtual line C0 and the side S13. The groove 314 is arranged between the through hole 16, that is, the virtual line C0 and the side S14.

The bottom surface 302 has at least one second groove along each side S21 to S24 of the plane 320, which is recessed with respect to the plane 320. At least one second groove along each side S21 to S24 is one second groove in this embodiment. That is, at least one second groove along the side S21 is one groove 321. Further, at least one second groove along the side S22 is one groove 322. Further, at least one second groove along the side S23 is one groove 323. Further, at least one second groove along the side S24 is one groove 324.

The groove 321 is arranged between the through hole 16, that is, the virtual line C0 and the side S21. The groove 322 is arranged between the through hole 16, that is, the virtual line C0 and the side S22. The groove 323 is arranged between the through hole 16, that is, the virtual line C0 and the side S23. The groove 324 is arranged between the through hole 16, that is, the virtual line C0 and the side S24.

The groove 311 is arranged in the vicinity of the side S11. The groove 312 is arranged in the vicinity of the side S12. The groove 313 is arranged in the vicinity of the side S13. The groove 314 is arranged in the vicinity of the side S14. The groove 321 is arranged in the vicinity of the side S21. The groove 322 is arranged in the vicinity of the side S22. The groove 323 is arranged in the vicinity of the side S23. The groove 324 is arranged in the vicinity of the side S24.

Each groove 311 to 314 is arranged at a position that does not intersect the diagonal lines L11 and L12. The grooves 321 to 324 are arranged at positions that do not intersect the diagonal lines L21 and L22. The top surface 301 has a shape that is rotationally symmetric with respect to the virtual line C0. Further, the top surface 301 has a shape symmetrical with respect to the diagonal lines L11 and L12. The bottom surface 302 has a shape that is rotationally symmetric with respect to the virtual line C0. Further, the bottom surface 302 has a shape that is line-symmetrical with respect to the diagonal lines L21 and L22. The top surface 301 and the bottom surface 302 have plane-symmetrical shapes with respect to the virtual surface orthogonal to the virtual line C0.

Next, the mold used for manufacturing the resin body 30 will be described. FIG. 5 is a schematic cross-sectional view of the mold 140 according to the first embodiment. FIG. 5 illustrates the mold 140 in a molded state. The mold 140 has a cavity 50 for forming the resin body 30. The cavity 50 is defined in a state where the mold 140 is molded. 6A and 6B are perspective views of the cavity 50 in the mold according to the first embodiment. 6A is a top perspective view of the cavity 50, and FIG. 6B is a bottom perspective view of the cavity 50.

The cavity 50 is a prismatic space, and in the first embodiment, it is a square columnar space. The mold 140 has a top surface forming surface 501 which is a first bottom surface forming surface which transfers the top surface 301 of the resin body 30, and a bottom surface forming surface which is a second bottom surface forming surface which transfers the bottom surface 302 of the resin body 30. 502 and. Further, the mold 140 has a plurality of side surface forming surfaces 551 to 554, which transfer a plurality of side surfaces 351 to 354 of the resin body 30, in the first embodiment. Any one of the plurality of side surface forming surfaces 551 to 554, for example, the side surface forming surface 551 is the first side surface forming surface. In this case, the side surface forming surfaces 552 to 554 are any of the second side surface forming surface, the third side surface forming surface, and the fourth side surface forming surface, respectively. The cavity 50 is defined by these plurality of surfaces 501, 502, 551 to 554. Each side surface forming surface 551 to 554 is a flat surface.

The mold 140 has a runner stencil plate 141, a fixed side stencil 142, and a movable side stencil 143. The runner 580 is defined by the runner stripper plate 141 and the fixed side template 142.

The fixed-side template 142 includes the above-mentioned top surface forming surface 501, a plurality of gates 571 to 574 for injecting molten resin into the cavity 50, a mold hole 1421, and an angular pin 1422. The mold hole 1421 is provided coaxially with the through hole 16 of the resin body 30. That is, the center line of the mold hole 1421 is the virtual line C0. The number of gates in this embodiment is preferably four, which is the same as the number of side surface forming surfaces 551 to 554. As a result, in the injection process described later, the symmetry of the pressure distribution of the resin body 30 becomes high, and the shape accuracy of the side surfaces 351 to 354 serving as the light reflecting surface is improved.

Further, it is preferable that the gates 571 to 574 and the side surface forming surfaces 551 to 554 have the same phase around the virtual line C0 which is the central axis of the mold hole 1421. As a result, in the injection step, the symmetry of the pressure distribution of the resin body 30 is further improved, and the shape accuracy of the side surfaces 351 to 354 serving as the light reflecting surface is further improved. Further, the weld generated between the gates 571 and 574 can be guided to the end of the side surface 351 to 354 which is outside the scanning range of the laser beam L in FIG. 2A.

The movable side template 143 has a movable side core 1431, a slide core 144, and an ejector plate 145. The movable side core 1431 includes the bottom surface forming surface 502 described above and the mold shaft 1432. The slide core 144 includes the side surface forming surfaces 551 to 554, and is guided by the angular pin 1422 and slides in a direction orthogonal to the virtual line C0 as the movable side template 143 opens and closes. The mold shaft 1432 is for forming the through hole 16 of the resin body 30.

The ejector plate 145 preferably has the same number of four ejector pins 1451 as the side surface forming surfaces 551 to 554. As a result, when the ejector pin 1451 is projected in the step of releasing the resin body 30 from the mold 140, the force can be evenly transmitted to the resin body 30, and the deformation of the resin body 30 due to the mold release is suppressed. be able to.

The top surface forming surface 501 has a plane forming surface 510 which is a first plane forming surface forming the plane 310. The plane forming surface 510 has a polygonal outer shape and has a plurality of sides. In the present embodiment, the plane forming surface 510 has a quadrangular outer shape and has four sides S51 to S54.

The bottom surface forming surface 502 has a plane forming surface 520 which is a second plane forming surface forming the plane 320. The plane forming surface 520 has a polygonal outer shape and has a plurality of sides. In the present embodiment, the plane forming surface 520 has a quadrangular outer shape and has four sides S61 to S64, like the plane forming surface 510. That is, the outer shape of the plane forming surface 510 and the outer shape of the plane forming surface 520 are congruent.

The plurality of sides S51 to S54 and S61 to S64 have the same length. Therefore, the outer shapes of the plane forming surfaces 510 and 520 are square. The length direction of the sides S51 and S61 is defined as the direction X51. The length direction of the sides S52 and S62 is defined as the direction X52. The length direction of the sides S53 and S63 is defined as the direction X53. The length direction of the sides S54 and S64 is defined as the direction X54. The plane forming surface 510 and the plane forming surface 520 are parallel to each other. The direction perpendicular to the plane forming surface 510 is defined as the direction Z5. Therefore, the direction Z5 is also a direction perpendicular to the plane forming surface 520. When viewed in the direction Z5, the sides S51 and S61 are at the same positions as the side surface forming surface 551. When viewed in the direction Z5, the sides S52 and S62 are at the same positions as the side surface forming surface 552. When viewed in the direction Z5, the sides S53 and S63 are at the same positions as the side surface forming surface 553. When viewed in the direction Z5, the sides S54 and S64 are at the same positions as the side surface forming surface 554.

Since the plane forming surface 510 is a quadrangle, there are two diagonal lines L51 and L52. Since the plane forming surface 520 is a quadrangle, there are two diagonal lines L61 and L62.

The top surface forming surface 501 has at least one first protruding portion along each side S51 to S54 of the plane forming surface 510, which protrudes from the plane forming surface 510. At least one first protrusion along each side S51 to S54 is one first protrusion in the present embodiment. That is, at least one first protrusion along the side S51 is one protrusion 511. Further, at least one first protruding portion along the side S52 is one protruding portion 512. Further, at least one first protruding portion along the side S53 is one protruding portion 513. Further, at least one first protruding portion along the side S54 is one protruding portion 514. Each of the projecting portions 511 to 514 is a projecting portion that forms the grooves 311 to 314 of the resin body 30.

The protrusion 511 is arranged between the mold shaft 1432, that is, the virtual line C0 and the side S51. The protrusion 512 is arranged between the mold shaft 1432, that is, the virtual line C0 and the side S52. The protrusion 513 is arranged between the mold shaft 1432, that is, the virtual line C0 and the side S53. The protrusion 514 is arranged between the mold shaft 1432, that is, the virtual line C0 and the side S54.

The bottom surface forming surface 502 has at least one second protruding portion along each side S61 to S64 of the plane forming surface 520, which protrudes with respect to the plane forming surface 520. At least one second protrusion along each side S61 to S64 is one second protrusion in the present embodiment. That is, at least one second protrusion along the side S61 is one protrusion 521. Further, at least one second protrusion along the side S62 is one protrusion 522. Further, at least one second protruding portion along the side S63 is one protruding portion 523. Further, at least one second protrusion along the side S64 is one protrusion 524. Each protrusion 521 to 524 is a protrusion that forms each groove 321 to 324 of the resin body 30.

The protrusion 521 is arranged between the mold shaft 1432, that is, the virtual line C0 and the side S61. The protrusion 522 is arranged between the mold shaft 1432, that is, the virtual line C0 and the side S62. The protrusion 523 is arranged between the mold shaft 1432, that is, the virtual line C0 and the side S63. The protrusion 524 is arranged between the mold shaft 1432, that is, the virtual line C0 and the side S64.

The protrusion 511 is arranged in the vicinity of the side S51. The protrusion 512 is arranged in the vicinity of the side S52. The protrusion 513 is arranged in the vicinity of the side S53. The protrusion 514 is arranged in the vicinity of the side S54. The protrusion 521 is arranged in the vicinity of the side S61. The protrusion 522 is arranged in the vicinity of the side S62. The protrusion 523 is arranged in the vicinity of the side S63. The protrusion 524 is arranged in the vicinity of the side S64. The protrusions 511 to 514 are arranged at positions that do not intersect the diagonal lines L51 and L52. The protrusions 521 to 524 are arranged at positions that do not intersect the diagonal lines L61 and L62.

Next, the manufacturing method of the polygon mirror 3 will be described. 7A to 7C and FIGS. 8A to 8C are explanatory views showing each step of the method for manufacturing the resin body 30 in the polygon mirror 3 according to the first embodiment. In the mold opening step shown in FIG. 7A, the mold 140 is opened. Next, in the mold clamping step shown in FIG. 7B, the mold 140 is molded. At this time, the mold shaft 1432 of the movable side mold plate 143 is fitted with the mold hole 1421 of the fixed side mold plate 142, so that the positions of the fixed side mold plate 142 and the movable side mold plate 143 are aligned. The cavity 50 is defined in the mold 140.

Next, in the injection process shown in FIG. 7C, the molten resin M1 is injected into the cavity 50 through the runner 580 and the gates 571 to 574 of FIG. 6A by an injection molding machine (not shown).

Next, in the cooling step shown in FIG. 8A, the molten resin M1 is cooled and solidified by setting the mold 140 to a predetermined temperature lower than the temperature of the molten resin M1 to form the resin body 30. The mold 140 is, for example, a water-cooled type, and is cooled to a predetermined temperature by water.

After the resin body 30 is sufficiently cooled, the mold 140 is opened in the mold opening step shown in FIG. 8B. At this time, the top surface forming surface 501 of the fixed side template 142 is separated from the top surface 301 of the resin body 30, and FIGS. 6A and 6A of the slide core 144 are separated from the side surfaces 351 to 354 shown in FIGS. 3A and 3B of the resin body 30. The side surface forming surfaces 551 to 554 shown in 6B are separated from each other. Further, the runner 32 connected to the resin body 30 is separated from the resin body 30 by the runner stripper plate 141.

Then, in the mold release step shown in FIG. 8C, the ejector plate 145 is advanced toward the movable core 1431 to project the ejector pin 1451 from the movable core 1431, and the resin body 30 is formed from the bottom surface forming surface 502 of the movable core 1431. Separate the bottom surface 302. As a result, the resin body 30 is released from the mold 140.

After that, in the vapor deposition step, by vapor-depositing a metal such as aluminum on the side surfaces 351 to 354 of the resin body 30 shown in FIGS. 3A and 3B, the side surfaces 351 to 354 serve as light reflecting surfaces of FIGS. 2A and 2B. The reflective film 31 is formed. As a result, the polygon mirror 3 is manufactured.

Here, a case will be described in which a resin body of a comparative example having no grooves 311 to 314, 321 to 324 is manufactured by using a mold having no protrusions 511 to 514, 521 to 524. In the cooling step, there is a difference in the solidification rate of the resin between the central portion and the end portion in the length direction on the side surface of the resin body. That is, the end portion in the length direction on the side surface solidifies relatively faster than the central portion. Therefore, the end portion in the length direction on the side surface has a higher resin density than the central portion, and when the resin body of the comparative example is released from the mold, the end portion on the side surface warps with respect to the central portion. In addition, the side surface of the resin body of the comparative example is deformed.

Therefore, in the first embodiment, the resin body 30 is molded using a mold 140 having protrusions 511 to 514, 521 to 524 in order to make the resin densities on the side surfaces 351 to 354 of the resin body 30 uniform. On the top surface 301 and the bottom surface 302 of the resin body 30, the grooves 311 to 314, 321 to 324 that do not intersect the diagonal lines L11, L12, L21, and L22 increase the surface area near the center of the directions X1 to X4 on the side surfaces 351 to 354. .. As a result, cooling solidification of the central portion of the directions X1 to X4 on the side surfaces 351 to 354 is promoted, and the difference in the solidification rate of the resin between the end portions and the central portion of the directions X1 to X4 on the side surfaces 351 to 354 becomes small. Thereby, the density difference of the resin between the end portion and the central portion of the directions X1 to X4 on the side surfaces 351 to 354 can be reduced, and the shape error of the directions X1 to X4 on the side surfaces 351 to 354 can be reduced. As a result, the shape accuracy of the side surfaces 351 to 354 of the resin body 30 is improved.

In the present embodiment, the grooves 311 to 314 of the resin body 30 are grooves extending linearly in parallel with the sides S11 to S14 along which the grooves 311 to 314 are aligned. Similarly, the grooves 321 to 324 of the resin body 30 are grooves extending linearly in parallel with the sides S21 to S24 along which the grooves 321 to 324 are aligned. That is, each of the protrusions 511 to 514 of the mold 140 is a protrusion that extends linearly in parallel with each side S51 to S54 along which the protrusions 511 to 514 are aligned. Similarly, each of the protrusions 521 to 524 of the mold 140 is a protrusion that extends linearly in parallel with each side S61 to S64 along which the protrusions 521 to 524 are aligned. As a result, the solidification speed of each direction X1 to X4 on each side surface 351 to 354 becomes uniform, and the shape accuracy of each side surface 351 to 354 is further improved.

Further, in the first embodiment, the groove 311 along the one side S11 and the groove 321 along the one side S21 overlap each other when the resin body 30 is viewed in the direction Z1. Further, when the resin body 30 is viewed in the direction Z1, the groove 312 along the one side S12 and the groove 322 along the one side S22 overlap each other. Further, when the resin body 30 is viewed in the direction Z1, the groove 313 along the side S13 and the groove 323 along the side S23 overlap each other. Further, when the resin body 30 is viewed in the direction Z1, the groove 314 along the side S14 and the groove 324 along the side S24 overlap each other. That is, when the molded mold 140 is viewed in the direction Z5, the protruding portion 511 along the one side S51 and the protruding portion 521 along the one side S61 overlap each other. Further, when the molded mold 140 is viewed in the direction Z5, the protruding portion 512 along the one side S52 and the protruding portion 522 along the one side S62 overlap each other. Further, when the molded mold 140 is viewed in the direction Z5, the protruding portion 513 along the one side S53 and the protruding portion 523 along the one side S63 overlap each other. Further, when the molded mold 140 is viewed in the direction Z5, the protruding portion 514 along the one side S54 and the protruding portion 524 along the one side S64 overlap each other. As a result, the solidification speed of each direction X1 to X4 on each side surface 351 to 354 becomes uniform, and the shape accuracy of each side surface 351 to 354 is further improved.

Further, in the first embodiment, the depths of the grooves 311 to 314 are the same, and the depth is D1. Further, the depths of the grooves 321 to 324 are the same, and the depth is D2. In the first embodiment, the depth D1 of the groove 311 and the depth D2 of the groove 321 are the same. Further, the depth D1 of the groove 312 and the depth D2 of the groove 322 are the same. Further, the depth D1 of the groove 313 and the depth D2 of the groove 323 are the same. Further, the depth D1 of the groove 314 and the depth D2 of the groove 324 are the same. The depths D1 and D2 are, for example, 0.4 mm. As a result, the solidification speed of each direction X1 to X4 on each side surface 351 to 354 becomes uniform, and the shape accuracy of each side surface 351 to 354 is further improved.

The length L of each side S11 to S14 and S21 to S24 of the resin body 30 is preferably 10 mm or more and 30 mm or less, for example, 14.1 mm, and the diameter of the circumscribed circle is preferably φ20 mm. The thickness Z of the resin body 30 is preferably 0.5 mm or more and 10 mm or less, and is preferably 2 mm, for example.

Further, between the through hole 16 and the grooves 311 to 314 on the top surface 301 side, there are gate marks 171 to 174 corresponding to the four gates 571 to 574 that are the resin injection ports. The distance between the gate marks 171 to 174 and the through hole 16 is the same. Further, the relative positions of the side surfaces 351 to 354 and the gate marks 171 to 174 are the same. Each side surface 351 to 354 and each gate mark 171 to 174 are rotationally symmetric with respect to the virtual line C0.

It is preferable that the side wall surfaces of the grooves 311 to 314 and the side wall surfaces of the grooves 321 to 324 are inclined at a predetermined angle θ so as to have a draft with respect to the side surfaces 351 to 354. Since the configurations of the grooves 311 to 314 and 321 to 324 are substantially the same, the grooves 311, 321 will be specifically described.

The groove 311 is formed so as to extend linearly along the side S11 in parallel with the side S11. The groove 311 has a pair of side wall surfaces 3111, 3112 along the side surface 351. It is preferable that the side wall surfaces 3111 and 3112 are inclined at a predetermined angle θ with respect to the side surface 351 so as to have a draft. Further, the groove 321 is formed so as to extend linearly along the side S21 in parallel with the side S21. The groove 321 has a pair of side wall surfaces 3211 and 3212 along the side surface 351. It is preferable that the side wall surfaces 3211 and 3212 are inclined at a predetermined angle θ with respect to the side surface 351 so as to have a draft.

Here, the fact that the groove 311 extends linearly along the side S11 in parallel with the side S11 means that at least the side wall surface 3111 of the pair of side wall surfaces 3111 and 3112 of the groove 311 is parallel to the side S11 along the side S11. It extends in a straight line. The same applies to the groove 321. When the groove 321 extends linearly along the side S21 in parallel with the side S21, at least the side wall surface 3111 of the pair of side wall surfaces 3211 and 3212 of the groove 321 is parallel to the side S21. It extends linearly along the side S21. The same applies to the other grooves 312 to 314 and 322 to 324.

The predetermined angle θ is preferably 5 degrees or more and 45 degrees or less in view of the cooling property of the resin body 30, the ease of mold release of the resin body 30, and the rigidity of the resin body 30. The predetermined angle θ is, for example, 30 degrees. If the predetermined angle θ is smaller than 5 degrees, there is a concern that the resin body 30 to be released from the mold will be deformed in the mold release step. Further, when the predetermined angle is larger than 45 degrees, the deepest portion of the grooves 311, 321 is moved away from the side surface 351 and therefore the cooling effect of the side surface 351 is low.

Let T be the thickness of the resin body 30 between the grooves 311 and the grooves 321 that overlap in the direction Z1, and W be the width of each of the grooves 311 and the grooves 321 that overlap in the direction Z1. Similarly, the thickness of the resin body 30 between the grooves 312 and the grooves 322 that overlap in the direction Z1 is T, and the groove widths of the grooves 312 and 322 that overlap in the direction Z1 are W. Similarly, the thickness of the resin body 30 between the grooves 313 and the grooves 323 that overlap in the direction Z1 is T, and the groove widths of the grooves 313 and the grooves 323 that overlap in the direction Z1 are W. Similarly, the thickness of the resin body 30 between the grooves 314 and the grooves 324 that overlap in the direction Z1 is T, and the groove widths of the grooves 314 and the grooves 324 that overlap in the direction Z1 are W. In view of the shape accuracy of each side surface 351 to 354 and the rigidity of the resin body 30, it is preferable that the thickness T and the groove width W satisfy the relationship of 1 ≦ W / T ≦ 2.5.

When the groove width W is narrow, that is, when W / T <1, the cooling effect at the central portion of each side surface 351 to 354 is small in the cooling step. On the contrary, when the groove width W is wide, that is, 2.5 <W / T, the rigidity of the resin body 30 is significantly reduced. Similarly, when the thickness T is thick, that is, when W / T <1, the cooling effect at the central portion of each side surface 351 to 354 is small in the cooling step. On the contrary, when the thickness T is thin, that is, 2.5 <W / T, the rigidity of the resin body 30 is significantly reduced.

If the thickness Z is 2.0 mm and the depth D1 of the groove 311 and the depth D2 of the groove 321 are 0.4 mm each, the thickness T is 1.2 mm. When the thickness T is 1.2 mm and the groove width W is 1.8 mm, the ratio W / T of the groove width W to the thickness T is 1.5 (= 1.8 / 1.2) mm, and 1 ≦ W. The relationship of / T ≦ 2.5 is satisfied.

Further, the distance between the groove 311 and the side S11, the distance between the groove 312 and the side S12, the distance between the groove 313 and the side S13, and the distance between the groove 314 and the side S14 are each set as D. Further, the distance between the groove 321 and the side S21, the distance between the groove 322 and the side S22, the distance between the groove 323 and the side S23, and the distance between the groove 324 and the side S24 are each set as D. In view of the shape accuracy of each side surface 351 to 354 and the rigidity of the resin body 30, it is preferable that the thickness T and the interval D satisfy the relationship of 0.3 ≦ D / T ≦ 1. When the interval D is wide, that is, 1 <D / T, the cooling effect at the central portion of each side surface 351 to 354 is small in the cooling step. On the contrary, when the interval D is narrow, that is, when D / T <0.3, the rigidity of the resin body 30 is significantly reduced.

When the thickness T is 1.2 mm and the interval D is 0.5 mm, the ratio D / T of the interval D to the thickness T is 0.42 (= 0.5 / 1.2) mm, and 0.3 ≦ D. The relationship of / T ≦ 1 is satisfied.

FIGS. 9A to 9D are graphs showing simulation results according to the first embodiment. FIG. 9A is a graph showing the relationship between the ratio W / T and the temperature difference of the side surface 351. FIG. 9B is a graph showing the relationship between the ratio W / T and the deformation of the side surface 351 when the resin body 30 is rotated. FIG. 9C is a graph showing the relationship between the ratio D / T and the temperature difference of the side surface 351. FIG. 9D is a graph showing the relationship between the ratio D / T and the deformation of the side surface 351 when the resin body 30 is rotated.

The vertical axis in the graphs shown in FIGS. 9A and 9C indicates the temperature difference between the central portion and the end portion of the direction X1 on the side surface 351. It is shown as a ratio with the difference as 1.

The vertical axis in the graphs shown in FIGS. 9B and 9D indicates the amount of displacement of the end portion of the side surface 351 with respect to the central portion of the direction X1, and the amount of displacement of the end portion of the side surface of the resin body of the comparative example without a groove with respect to the central portion. It is shown by the ratio of 1.

From the graph shown in FIG. 9A, it can be seen that the larger the ratio W / T, that is, the wider the groove width W with respect to the thickness T, the smaller the temperature difference in the cooling step. On the other hand, from the graph shown in FIG. 9B, the larger the ratio W / T, that is, the wider the groove width W, the larger the displacement amount when the resin body 30 is rotated.

From the above, in order to reduce the temperature difference on the side surface 351 and reduce the displacement amount on the side surface 351 it is preferable to satisfy 1 ≦ W / T ≦ 2.5, and 1.5 ≦ W / T ≦ 2. It is more preferable to meet.

From the graph shown in FIG. 9C, it can be seen that the smaller the ratio D / T, that is, the narrower the interval D with respect to the thickness T, the smaller the temperature difference in the cooling step. On the other hand, from the graph shown in FIG. 9D, the smaller the ratio D / T, that is, the narrower the interval D with respect to the thickness T, the larger the displacement amount.

From the above, in order to reduce the temperature difference on the side surface 351 and reduce the displacement amount on the side surface 351 it is preferable to satisfy 0.3 ≦ D / T ≦ 1, and 0.4 ≦ D / T ≦ 0. It is more preferable to satisfy 5.

[Second Embodiment]
The polygon mirror according to the second embodiment will be described. In the second embodiment, the description of the same configuration as that of the first embodiment will be omitted. 10A and 10B are perspective views of the resin body 30A in the polygon mirror according to the second embodiment. 10A is a top perspective view of the resin body 30A in the polygon mirror according to the second embodiment, and FIG. 10B is a bottom perspective view of the resin body 30A in the polygon mirror according to the second embodiment. FIG. 11A is a cross-sectional view of the resin body 30A according to the second embodiment. FIG. 11A illustrates a cross section of the resin body 30A along the XI-XI line of FIG. 11A. FIG. 11B is an enlarged view of a main part of the resin body 30A shown in FIG. 11A. In the second embodiment, the configuration of the resin body of the polygon mirror in the image forming apparatus is different from that of the first embodiment. That is, in the first embodiment, the case where the number of grooves along one side is one has been described, but in the second embodiment, the number of grooves along one side is a plurality.

The resin body 30A is a prismatic resin body, and in the second embodiment, it is a square columnar resin body. It is preferable to use a thermoplastic resin as the resin material of the resin body 30A. Among the thermoplastic resins, cycloolefin polymers, cycloolefin copolymers, polycarbonates, or acrylics are preferably used. The resin body 30A has a top surface 301A which is a first bottom surface, a bottom surface 302A which is a second bottom surface, and a plurality of side surfaces 351 to 354 in the second embodiment as in the first embodiment. Each side surface 351 to 354 is a flat surface. Reflective films 31 shown in FIGS. 2A and 2B are provided on each of the side surfaces 351 to 354.

The top surface 301A has a plane 310A which is the first plane. The plane 310A has a polygonal outer shape and has a plurality of sides. In the second embodiment, the plane 310A has a quadrangular outer shape and has four sides S11 to S14 as in the first embodiment.

The bottom surface 302A has a plane 320A which is a second plane. The plane 320A has a polygonal outer shape and has a plurality of sides. In the present embodiment, the plane 320A has a quadrangular outer shape like the plane 310A, and has four sides S21 to S24 as in the first embodiment. That is, the outer shape of the plane 310A and the outer shape of the plane 320A are congruent.

The plurality of sides S11 to S14 and S21 to S24 have the same length. Therefore, the outer shape of each of the planes 310A and 320A is a square. The length direction of the sides S11 and S21 is defined as the direction X1. The length direction of the sides S12 and S22 is defined as the direction X2. The length direction of the sides S13 and S23 is defined as the direction X3. The length direction of the sides S14 and S24 is defined as the direction X4. The plane 310A and the plane 320A are parallel to each other. The direction perpendicular to the plane 310A is defined as the direction Z1. Therefore, the direction Z1 is also a direction perpendicular to the plane 320A.

Since the plane 310A is a quadrangle, there are two diagonal lines L11 and L12 as in the first embodiment. Since the plane 320A is a quadrangle, there are two diagonal lines L21 and L22 as in the first embodiment. The virtual line C0 passing through the intersection of the two diagonal lines L11 and L12 and the intersection of the two diagonal lines L21 and L22 is the rotation center line of the resin body 30A. A columnar through hole 16 is formed at a position including the virtual line C0. That is, the center line of the through hole 16 is the virtual line C0. The rotation shaft 8 shown in FIG. 2B is inserted into the through hole 16.

The top surface 301A has at least one first groove along each side S11 to S14 of the plane 310A, which is recessed with respect to the plane 310A. At least one first groove along each side S11 to S14 is a plurality of first grooves, and in the second embodiment, three first grooves. That is, at least one first groove along the side S11 is three grooves 311 ₁ , 311 ₂ , 311 ₃ . Further, at least one first groove along the side S12 is three grooves 312 ₁ , 312 ₂ , 312 ₃ . Further, at least one first groove along the side S13 is three grooves 313 ₁ , 313 ₂ , 313 ₃ . Further, at least one first groove along the side S14 is three grooves 314 ₁ , 314 ₂ , 314 ₃ .

The three grooves 311 ₁ , 311 ₂ , 311 ₃ are arranged between the through hole 16, that is, the virtual line C0 and the side S11. The three grooves 312 ₁ , 312 ₂ , 312 ₃ are arranged between the through hole 16, that is, the virtual line C0 and the side S12. The three grooves 313 ₁ , 313 ₂ , 313 ₃ are arranged between the through hole 16, that is, the virtual line C0 and the side S13. The three grooves 314 ₁ , 314 ₂ , and 314 ₃ are arranged between the through hole 16, that is, the virtual line C0 and the side S14.

The bottom surface 302A has at least one second groove along each side S21 to S24 of the plane 320A, which is recessed with respect to the plane 320A. At least one second groove along each side S21 to S24 is a plurality of second grooves, and in the second embodiment, three second grooves. That is, at least one second groove along the side S21 is three grooves 321 ₁ , 321, ₂ and 321 ₃ . Further, at least one second groove along the side S22 is three grooves 322 ₁ , 322 ₂ , 322 ₃ . Further, at least one second groove along the side S23 is three grooves 323 ₁ , 323 ₂ , 323 ₃ . Further, at least one second groove along the side S24 is three grooves 324 ₁ , 324 ₂ , 324 ₃ .

The three grooves 321 ₁ , 321, ₂ and 321 ₃ are arranged between the through hole 16, that is, the virtual line C0 and the side S21. The three grooves 322 ₁ , 322 ₂ , and 322 ₃ are arranged between the through hole 16, that is, the virtual line C0 and the side S22. The three grooves 323 ₁ , 323 ₂ , 323 ₃ are arranged between the through hole 16, that is, the virtual line C0 and the side S23. The three grooves 324 ₁ , 324 ₂ , 324 ₃ are arranged between the through hole 16, that is, the virtual line C0 and the side S24.

Of the grooves 311 ₁ , 311 ₂ , and 311 ₃ , the groove 311 ₁ is arranged in the vicinity of the side S11. Of the grooves 312 ₁ , 312 ₂ , 312 ₃ , the groove 312 ₁ is arranged in the vicinity of the side S12. Of the grooves 313 ₁ , 313 ₂ , 313 ₃ , the groove 313 ₁ is arranged in the vicinity of the side S13. Of the grooves 314 ₁ , 314 ₂ , and 314 ₃ , the groove 314 ₁ is arranged in the vicinity of the side S14. Of the grooves 321 ₁ , 321, ₂ and 321 ₃ , the groove 321 ₁ is arranged in the vicinity of the side S21. Of the grooves 322 ₁ , 322 ₂ , and 322 ₃ , the groove 322 ₁ is arranged in the vicinity of the side S22. Of the grooves 323 ₁ , 323 ₂ , and 323 ₃ , the groove 323 ₁ is arranged in the vicinity of the side S23. Of the grooves 324 ₁ , 324 ₂ , and 324 ₃ , the groove 324 ₁ is arranged in the vicinity of the side S24.

The grooves 311 ₁ to 311 ₃ , 312 ₁ to 312 ₃ , 313 ₁ to 313 ₃ , 314 ₁ to 314 ₃ are arranged at positions that do not intersect the diagonal lines L11 and L12. The grooves 321 ₁ to 321 ₃ , 322 ₁ to 322 ₃ , 323 ₁ to 323 ₃ , 324 ₁ to 324 ₃ are arranged at positions that do not intersect the diagonal lines L21 and L22. The top surface 301A has a shape that is rotationally symmetric with respect to the virtual line C0. Further, the top surface 301A has a shape that is line-symmetrical with respect to the diagonal lines L11 and L12. The bottom surface 302A has a shape that is rotationally symmetric with respect to the virtual line C0. Further, the bottom surface 302A has a shape that is line-symmetrical with respect to the diagonal lines L21 and L22. The top surface 301A and the bottom surface 302A are plane-symmetrical with respect to the virtual surface orthogonal to the virtual line C0.

Next, the mold used for manufacturing the resin body 30A will be described. 12A and 12B are perspective views of the cavity 50A in the mold 140A according to the second embodiment. 12A is a top perspective view of the cavity 50A, and FIG. 12B is a bottom perspective view of the cavity 50A. The mold 140A has a cavity 50A for forming the resin body 30A. The cavity 50A is defined with the mold 140A clamped.

The cavity 50A is a prismatic space, and in the second embodiment, it is a square columnar space. The mold 140A has a top surface forming surface 501A which is a first bottom surface forming surface which transfers the top surface 301A of the resin body 30A and a bottom surface forming surface which is a second bottom surface forming surface which transfers the bottom surface 302A of the resin body 30A. It has 502A and. Further, the mold 140A has a plurality of side surfaces 351 to 354 for transferring the plurality of side surfaces 351 to 354 of the resin body 30A, and four side surface forming surfaces 551 to 554 in the second embodiment. The cavity 50A is defined by these plurality of surfaces 501A, 502A, 551 to 554. Each side surface forming surface 551 to 554 is a flat surface.

The mold 140A includes the above-mentioned top surface forming surface 501A and a plurality of gates 571 to 574 for injecting the molten resin into the cavity 50A. The number of gates is preferably four, which is the same as the number of side surface forming surfaces 551 to 554. As a result, in the injection step, the symmetry of the pressure distribution of the resin body 30A becomes high, and the shape accuracy of the side surfaces 351 to 354 serving as the light reflecting surface is improved.

Further, it is preferable that the phases of the gates 571 to 574 and the side surface forming surfaces 551 to 554 are the same around the virtual line C0. As a result, in the injection step, the symmetry of the pressure distribution of the resin body 30A is further increased, and the shape accuracy of the side surfaces 351 to 354 serving as the light reflecting surface is further improved. Further, the weld generated between the gates 571 and 574 can be guided to the end of the side surface 351 to 354 which is outside the scanning range of the laser beam L in FIG. 2A.

The top surface forming surface 501A has a plane forming surface 510A which is a first plane forming surface forming the plane 310A. The plane forming surface 510A has a polygonal outer shape and has a plurality of sides. In the second embodiment, the plane forming surface 510A has a quadrangular outer shape and has four sides S51 to S54.

The bottom surface forming surface 502A has a plane forming surface 520A which is a second plane forming surface forming the plane 320A. The plane forming surface 520A has a polygonal outer shape and has a plurality of sides. In the second embodiment, the plane forming surface 520A has a quadrangular outer shape and has four sides S61 to S64, like the plane forming surface 510A. That is, the outer shape of the plane forming surface 510A and the outer shape of the plane forming surface 520A are congruent.

The plurality of sides S51 to S54 and S61 to S64 have the same length. Therefore, the outer shapes of the plane forming surfaces 510A and 520A are square. The length direction of the sides S51 and S61 is defined as the direction X51. The length direction of the sides S52 and S62 is defined as the direction X52. The length direction of the sides S53 and S63 is defined as the direction X53. The length direction of the sides S54 and S64 is defined as the direction X54. The plane forming surface 510A and the plane forming surface 520A are parallel to each other. The direction perpendicular to the plane forming surface 510A is defined as the direction Z5. Therefore, the direction Z5 is also a direction perpendicular to the plane forming surface 520A.

Since the plane forming surface 510A is a quadrangle, there are two diagonal lines L51 and L52. Since the plane forming surface 520A is a quadrangle, there are two diagonal lines L61 and L62.

The top surface forming surface 501A has at least one first protruding portion along each side S51 to S54 of the plane forming surface 510A, which protrudes from the plane forming surface 510A. At least one first protrusion along each side S51 to S54 is a plurality of first protrusions, and in the second embodiment, three first protrusions. That is, at least one first protrusion along the side S51 is three protrusions 511 ₁ , 511 ₂ , 511 ₃ . Further, at least one first protrusion along the side S52 is one protrusion 512 ₁ , 512 ₂ , 512 ₃ . Further, at least one first protruding portion along the side S53 is one protruding portion 513 ₁ , 513 ₂ , 513 ₃ . Further, at least one first protruding portion along the side S54 is one protruding portion 514 ₁ , 514 ₂ , 514 ₃ . Each protrusion 511 ₁ to 511 ₃ , 512 ₁ to 512 ₃ , 513 ₁ to 513 ₃ , 514 ₁ to 514 ₃ is each groove of the resin body 30A, 311 ₁ to 311 ₃ , 312 ₁ to 312 ₃ , 313 ₁ to 313. It is a protrusion forming ₃ , 314 ₁ to 314 _3.

The protrusions 511 ₁ , 511 ₂ , 511 ₃ are arranged between the mold shaft 1432, that is, the virtual line C0 and the side S51. The protrusions 512 ₁ , 512 ₂ , 512 ₃ are arranged between the mold shaft 1432, that is, the virtual line C0 and the side S52. The protrusions 513 ₁ , 513 ₂ , 513 ₃ are arranged between the mold shaft 1432, that is, the virtual line C0 and the side S53. The protrusions 514 ₁ , 514 ₂ , 514 ₃ are arranged between the mold shaft 1432, that is, the virtual line C0 and the side S54.

The bottom surface forming surface 502A has at least one second protruding portion along each side S61 to S64 of the plane forming surface 520A, which protrudes with respect to the plane forming surface 520A. At least one second protrusion along each side S61 to S64 is a plurality of second protrusions, and in the second embodiment, three second protrusions. That is, at least one second protrusion along the side S61 is three protrusions 521 ₁ , 521 ₂ , 521 ₃ . Further, at least one second protrusion along the side S62 is three protrusions 522 ₁ , 522 ₂ , 522 ₃ . Further, at least one second protrusion along the side S63 is three protrusions 523 ₁ , 523 ₂ , 523 ₃ . Further, at least one second protrusion along the side S64 is three protrusions 524 ₁ , 524 ₂ , 524 ₃ . Each protrusion 521 ₁ to 521 ₃ , 522 ₁ to 522 ₃ , 523 ₁ to 523 ₃ , 524 ₁ to 524 ₃ is each groove of the resin body 30A, 321 ₁ to 321 ₃ , 322 ₁ to 322 ₃ , 323 ₁ to 323. _{3, 324} 1 to 324 ₃ a protrusion which forms a.

The protrusions 521 ₁ , 521 ₂ , 521 ₃ are arranged between the mold shaft 1432, that is, the virtual line C0 and the side S61. The protrusions 522 ₁ , 522 ₂ , and 522 ₃ are arranged between the mold shaft 1432, that is, the virtual line C0 and the side S62. The protrusions 523 ₁ , 523 ₂ , 523 ₃ are arranged between the mold shaft 1432, that is, the virtual line C0 and the side S63. The protrusions 524 ₁ , 524 ₂ , 524 ₃ are arranged between the mold shaft 1432, that is, the virtual line C0 and the side S64.

Of the protruding portions 511 ₁ , 511 ₂ , and 511 ₃ , the protruding portion 511 ₁ is arranged in the vicinity of the side S51. Of the protrusions 512 ₁ , 512 ₂ , 512 ₃ , the protrusions 512 ₁ are arranged in the vicinity of the side S52. Of the protruding portions 513 ₁ , 513 ₂ , 513 ₃ , the protruding portion 513 ₁ is arranged in the vicinity of the side S53. Of the protrusions 514 ₁ , 514 ₂ , 514 ₃ , the protrusion 514 ₁ is arranged in the vicinity of the side S54. Of the protruding portions 521 ₁ , 521 ₂ , 521 ₃ , the protruding portion 521 ₁ is arranged in the vicinity of the side S61. Of the protrusions 522 ₁ , 522 ₂ , 522 ₃ , the protrusion 522 ₁ is arranged in the vicinity of the side S62. Of the protrusions 523 ₁ , 523 ₂ , 523 ₃ , the protrusion 523 ₁ is arranged in the vicinity of the side S63. Of the protrusions 524 ₁ , 524 ₂ , 524 ₃ , the protrusion 524 ₁ is arranged in the vicinity of the side S64. The protrusions 511 ₁ to 511 ₃ , 512 ₁ to 512 ₃ , 513 ₁ to 513 ₃ , 514 ₁ to 514 ₃ are arranged at positions that do not intersect the diagonal lines L51 and L52. The protrusions 521 ₁ to 521 ₃ , 522 ₁ to 522 ₃ , 523 ₁ to 523 ₃ , 524 ₁ to 524 ₃ are arranged at positions that do not intersect the diagonal lines L61 and L62.

Since the method for manufacturing the polygon mirror of the second embodiment is the same as that of the first embodiment, it will be omitted. In the second embodiment, in order to make the resin density on the side surfaces 351 to 354 of the resin body 30A uniform, the resin body 30A is molded by using the mold 140A having the above-mentioned protrusion. On the top surface 301A and the bottom surface 302A of the resin body 30A, the groove that does not intersect the diagonal lines L11, L12, L21, and L22 increases the surface area near the central portion of the directions X1 to X4 on the side surfaces 351 to 354. As a result, cooling solidification of the central portion of the directions X1 to X4 on the side surfaces 351 to 354 is promoted, and the difference in the solidification rate of the resin between the end portions and the central portion of the directions X1 to X4 on the side surfaces 351 to 354 becomes small. Thereby, the density difference of the resin between the end portion and the central portion of the directions X1 to X4 on the side surfaces 351 to 354 can be reduced, and the shape error of the directions X1 to X4 on the side surfaces 351 to 354 can be reduced. As a result, the shape accuracy of the side surfaces 351 to 354 of the resin body 30A is improved.

In the second embodiment, each groove 311 ₁ to 311 ₃ , 312 ₁ to 312 ₃ , 313 ₁ to 313 ₃ , 314 ₁ to 314 ₃ of the resin body 30A is a straight line parallel to each side S11 to S14 along which each groove runs. It is a groove extending in a shape. Similarly, each groove 321 ₁ to 321 ₃ , 322 ₁ to 322 ₃ , 323 ₁ to 323 ₃ , 324 ₁ to 324 ₃ of the resin body 30A extends linearly in parallel with each side S21 to S24 along which each groove runs. It is a groove. That is, the protrusions 511 ₁ to 511 ₃ , 512 ₁ to 512 ₃ , 513 ₁ to 513 ₃ , 514 ₁ to 514 ₃ of the mold 140A are linearly parallel to each side S51 to S54 along which each protrusion is aligned. It is an extending protrusion. Similarly, each of the protrusions 521 ₁ to 521 ₃ , 522 ₁ to 522 ₃ , 523 ₁ to 523 ₃ , 524 ₁ to 524 ₃ of the mold 140A is linear in parallel with each side S61 to S64 along which each protrusion is along. It is a protrusion extending to. As a result, the solidification speed of each direction X1 to X4 on each side surface 351 to 354 becomes uniform, and the shape accuracy of each side surface 351 to 354 is further improved.

In the second embodiment, when the resin body 30A is viewed in the direction Z1, the grooves 311 ₁ to 311 _{4 along the side S11 and the grooves 321 1} to 321 ₄ along the side S21 overlap each other. Further, when the resin body 30A is viewed in the direction Z1, the grooves 312 ₁ to 312 _{4 along the side S12 and the grooves 322 1} to 322 ₄ along the side S22 overlap each other. Further, when the resin body 30A is viewed in the direction Z1, the grooves 313 ₁ to 313 _{4 along the side S13 and the grooves 323 1} to 323 ₄ along the side S23 overlap each other. Further, when the resin body 30A is viewed in the direction Z1, the grooves 314 ₁ to 314 _{4 along the side S14 and the grooves 324 1} to 324 ₄ along the side S24 overlap each other. That is, when the molded mold 140A is viewed in the direction Z5, the protrusions 511 ₁ to 511 _{4 along the side S51 and the protrusions 521 1} to 521 ₄ along the side S61 overlap each other. Further, when the molded mold 140A is viewed in the direction Z5, the protrusions 512 ₁ to 512 _{4 along the side S52 and the protrusions 522 1} to 522 ₄ along the side S62 overlap each other. Further, when the molded mold 140A is viewed in the direction Z5, the protruding portions 513 ₁ to 513 _{4 along the one side S53 and the protruding portions 523 1} to 523 ₄ along the one side S63 overlap each other. Further, when the molded mold 140A is viewed in the direction Z5, the protruding portions 514 ₁ to 514 _{4 along the one side S54 and the protruding portions 524 1} to 524 ₄ along the one side S64 overlap each other. As a result, the solidification speed of each direction X1 to X4 on each side surface 351 to 354 becomes uniform, and the shape accuracy of each side surface 351 to 354 is further improved.

Further, in the second embodiment, since the resin body 30A has a plurality of grooves along each of the plurality of sides, it is possible to suppress a decrease in the rigidity of the resin body 30A due to the formation of the grooves. As a result, it is possible to suppress deformation of each side surface 351 to 354 when the polygon mirror is incorporated in the scanner motor 1 and driven to rotate.

Further, in the second embodiment, _{the depths of the grooves 311 1} to 311 ₃ and 312 ₁ to 312 ₃ and 313 ₁ to 313 ₃ and 314 ₁ to 314 ₃ are the same, and the depth is D1. Further, _{the depths of the grooves 321 1} to 321 ₃ , 322 ₁ to 322 ₃ , 323 ₁ to 323 ₃ , 324 ₁ to 324 ₃ are the same, and the depth is D2. In the second embodiment, _{the depth D1 of the grooves 311 1} to 311 _{3 and} the depth D2 of the grooves 321 ₁ to 321 ₃ are the same. Further, the depth D1 of the grooves 312 ₁ to 312 _{3 and} the depth D2 of the grooves 322 ₁ to 322 ₃ are the same. Further, the depth D1 of the grooves 313 ₁ to 313 _{3 and} the depth D2 of the grooves 323 ₁ to 323 ₃ are the same. Further, the depth D1 of the grooves 314 ₁ to 314 _{3 and} the depth D2 of the grooves 324 ₁ to 324 ₃ are the same. The depths D1 and D2 are, for example, 0.4 mm. As a result, the solidification speed of each direction X1 to X4 on each side surface 351 to 354 becomes uniform, and the shape accuracy of each side surface 351 to 354 is further improved.

The length L of each side S11 to S14 and S21 to S24 of the resin body 30A is preferably 10 mm or more and 30 mm or less, for example, 14.1 mm, and the diameter of the circumscribed circle is preferably φ20 mm. The thickness Z of the resin body 30A is preferably 0.5 mm or more and 10 mm or less, and is preferably 2 mm, for example.

Further, between the through hole 16 and the grooves 3111 ₃ to 314 ₃ on the top surface 301A side, there are gate marks 171 to 174 corresponding to the four gates 571 to 574 that are the resin injection ports. The distance between the gate marks 171 to 174 and the through hole 16 is the same. Further, the relative positions of the side surfaces 351 to 354 and the gate marks 171 to 174 are the same. Each side surface 351 to 354 and each gate mark 171 to 174 are rotationally symmetric with respect to the virtual line C0.

The side wall surfaces of each groove 311 ₁ to 311 ₃ , ..., 314 ₁ to 314 _{3 and} the side wall surfaces of each groove 321 ₁ to 321 ₃ , ..., 324 ₁ to 324 ₃ have a draft with respect to each side surface 351 to 354. It is preferable to incline at a predetermined angle θ so as to be. Grooves 311 ₁ to 311 ₃ , 312 ₁ to 312 ₃ , 313 ₁ to 313 ₃ , 314 ₁ to 314 ₃ , 321 ₁ to 321 ₃ , 322 ₁ to 322 ₃ , 323 ₁ to 323 ₃ , 324 ₁ to 324 ₃ Since they are substantially the same, the grooves 311 ₁ and 321 ₁ will be specifically described.

The groove 311 ₁ is formed so as to extend linearly along the side S11 in parallel with the side S11. The groove _{3111 1} has a pair of side wall surfaces 3111, 3112 along the side surface 351. It is preferable that the side wall surfaces 3111 and 3112 are inclined at a predetermined angle θ with respect to the side surface 351 so as to have a draft. Further, the groove 321 ₁ is formed so as to extend linearly along the side S21 in parallel with the side S21. The groove 321 ₁ has a pair of side wall surfaces 3211 and 3212 along the side surface 351. It is preferable that the side wall surfaces 3211 and 3212 are inclined at a predetermined angle θ with respect to the side surface 351 so as to have a draft.

Here, the extending linearly along the parallel sides S11 grooves 311 ₁ and the sides S11, a pair of side wall surfaces 3111,3112 of grooves 311 _1, parallel at least the side wall surface 3111 and edge S11 sides S11 It extends linearly along. The same _{applies to the groove 321 1} , and the fact that the groove 321 extends linearly along the side S21 in parallel with the side S21 means that at least the side wall surface 3111 of the pair of side wall surfaces 3211 and 3212 of _{the groove 321 1 is the side S21.} It extends linearly along the side S21 in parallel with. The same applies to other grooves.

The predetermined angle θ is preferably 5 degrees or more and 45 degrees or less in view of the cooling property of the resin body 30A, the ease of mold release of the resin body 30A, and the rigidity of the resin body 30A. The predetermined angle θ is, for example, 30 degrees. If the predetermined angle θ is smaller than 5 degrees, there is a concern that the resin body 30A to be released from the mold will be deformed in the mold release step. Further, when the predetermined angle is larger than 45 degrees _{, the deepest portion of the grooves 311 1} and 321 ₁ is moved away from the side surface 351 so that the cooling effect of the side surface 351 is low.

Let T be the thickness of the resin body 30A between the _{grooves 311 1} to 311 ₃ , ..., 314 ₁ to 314 ₃ and the grooves 321 ₁ to 321 ₃ , ..., 324 ₁ to 324 ₃ , which overlap in the direction Z1. The widths of the grooves 311 ₁ , 311 ₂ , and 311 _{3 are W 1} , W ₂ , and W ₃ , respectively. Let W be the sum of the widths of the plurality of grooves 311 ₁ , 311 ₂ , and 311 _3. W = W ₁ + W ₂ + W ₃ . The same applies to the _{grooves 312 1 to 312 3} , 313 ₁ to 313 ₃ , 314 ₁ to 314 ₃ , 321 ₁ to 321 ₃ , 322 ₁ to 322 ₃ , 323 ₁ to 323 ₃ , 324 ₁ to 324 ₃ . In view of the shape accuracy of each side surface 351 to 354 and the rigidity of the resin body 30A, it is preferable that the total W of the thickness T and the groove width satisfies the relationship of 1 ≦ W / T ≦ 2.5.

When the total W of the groove widths is narrow, that is, when W / T <1, the cooling effect at the central portion of each side surface 351 to 354 is small in the cooling step. On the contrary, when the total W of the groove widths is wide, that is, 2.5 <W / T, the rigidity of the resin body 30A is significantly reduced. Similarly, when the thickness T is thick, that is, when W / T <1, the cooling effect at the central portion of each side surface 351 to 354 is small in the cooling step. On the contrary, when the thickness T is thin, that is, 2.5 <W / T, the rigidity of the resin body 30A is significantly reduced.

If the thickness Z is 2.0 mm and the depths D1 and D2 are 0.4 mm each, the thickness T is 1.2 mm. When the thickness T is 1.2 mm, the groove widths W ₁ , W ₂ , and W ₃ are 0.6 mm, that is, the total groove width W is 1.8 mm, the ratio of the total groove width W to the thickness T is W / T. Is 1.5 (= 1.8 / 1.2) mm, which satisfies the relationship of 1 ≦ W / T ≦ 2.5.

Of the grooves 311 ₁ to 3111 ₃ , the groove closest to the side S11 is the groove 3111 ₁ . Of the grooves 312 ₁ to 312 ₃ , the groove closest to the side S12 is the groove 312 ₁ . Of the grooves 313 ₁ to 313 ₃ , the groove closest to the side S13 is the groove 313 ₁ . Of the grooves 314 ₁ to 314 ₃ , the groove closest to the side S14 is the groove 314 ₁ . Of the grooves 321 ₁ to 321 ₃ , the groove closest to the side S21 is the groove 321 ₁ . Of the grooves 322 ₁ to 322 ₃ , the groove closest to the side S22 is the groove 322 ₁ . Of the grooves 323 ₁ to 323 ₃ , the groove closest to the side S23 is the groove 323 ₁ . Of the grooves 324 ₁ to 324 ₃ , the groove closest to the side S24 is the groove 324 ₁ .

Let D be the distance between the groove 311 ₁ and the side S11, the distance between the groove 312 ₁ and the side S12, the distance between the groove 313 ₁ and the side S13, and the distance between the groove 314 _{1 and the side S14.} Further, the distance between the groove 321 ₁ and the side S21, the distance between the groove 322 ₁ and the side S22, the distance between the groove 323 ₁ and the side S23, and the distance between the groove 324 ₁ and the side S24 are each set as D. In view of the shape accuracy of each side surface 351 to 354 and the rigidity of the resin body 30A, it is preferable that the thickness T and the interval D satisfy the relationship of 0.3 ≦ D / T ≦ 1. When the interval D is wide, that is, 1 <D / T, the cooling effect at the central portion of each side surface 351 to 354 is small in the cooling step. On the contrary, when the interval D is narrow, that is, when D / T <0.3, the rigidity of the resin body 30A is significantly reduced.

When the thickness T is 1.2 mm and the interval D is 0.5 mm, the ratio D / T of the interval D to the thickness T is 0.42 (= 0.5 / 1.2) mm, and 0.3 ≦ D. The relationship of / T ≦ 1 is satisfied.

FIGS. 13A to 13D are graphs showing simulation results according to the second embodiment. FIG. 13A is a graph showing the relationship between the ratio W / T and the temperature difference of the side surface 351. FIG. 13B is a graph showing the relationship between the ratio W / T and the deformation of the side surface 351 when the resin body 30A is rotated. FIG. 13C is a graph showing the relationship between the ratio D / T and the temperature difference of the side surface 351. FIG. 13D is a graph showing the relationship between the ratio D / T and the deformation of the side surface 351 when the resin body 30A is rotated.

The vertical axis in the graphs shown in FIGS. 13A and 13C indicates the temperature difference between the central portion and the end portion of the direction X1 on the side surface 351. It is shown as a ratio with the difference as 1.

The vertical axis in the graphs shown in FIGS. 13B and 13D indicates the amount of displacement of the end portion of the side surface 351 with respect to the central portion of the direction X1, and the amount of displacement of the end portion of the side surface of the resin body of the comparative example having no groove with respect to the central portion. It is shown by the ratio of 1.

From the graph shown in FIG. 13A, it can be seen that the larger the ratio W / T, that is, the wider the total W of the groove width with respect to the thickness T, the smaller the temperature difference in the cooling step. On the other hand, from the graph shown in FIG. 13B, the larger the ratio W / T, that is, the wider the total W of the groove widths, the larger the displacement amount when the resin body 30A is rotated.

From the above, in order to reduce the temperature difference on the side surface 351 and reduce the displacement amount on the side surface 351 it is preferable to satisfy 1 ≦ W / T ≦ 2.5, and 1.5 ≦ W / T ≦ 2. It is more preferable to meet. Further, when the graph shown in FIG. 9B of the first embodiment and the graph shown in FIG. 13B of the second embodiment are compared, the graph shown in FIG. 13B has a ratio W / T more than the graph shown in FIG. 9B. The change in the amount of displacement with respect to the change is small. That is, when the number of grooves along one side is one, it is possible to suppress the increase in the amount of deformation of the resin body during rotational drive due to the increase in the ratio W / T when there are a plurality of grooves. can.

From the graph shown in FIG. 13C, it can be seen that the smaller the ratio D / T, that is, the narrower the interval D with respect to the thickness T, the smaller the temperature difference in the cooling step. On the other hand, from the graph shown in FIG. 13D, the smaller the ratio D / T, that is, the narrower the interval D with respect to the thickness T, the larger the displacement amount.

From the above, in order to reduce the temperature difference on the side surface 351 and reduce the displacement amount on the side surface 351 it is preferable to satisfy 0.3 ≦ D / T ≦ 1, and 0.4 ≦ D / T ≦ 0. It is more preferable to satisfy 5.

The present invention is not limited to the embodiments described above, and many modifications can be made within the technical idea of the present invention. Moreover, the effects described in the embodiments are merely a list of the most suitable effects resulting from the present invention, and the effects according to the present invention are not limited to those described in the embodiments.

In the above-described embodiment, the case where the resin body of the polygon mirror is a quadrangular prism having four side surfaces has been described, but the present invention is not limited to this. The resin body may be a prism having four or more side surfaces. In particular, the resin body is preferably a quadrangular prism, a pentagonal prism, or a hexagonal prism.

Further, in the above-described embodiment, the case where the outer shapes of the top surface and the bottom surface of the resin body are regular quadrangles, that is, the lengths of the respective sides are the same has been described, but the present invention is not limited to this. The top and bottom surfaces may be polygons having a quadrangle or more, and the lengths of the sides may be different. However, in the image forming apparatus, a regular polygon is preferable.

Further, in the above-described embodiment, the case where both the top surface and the bottom surface have grooves has been described, but only one of the top surface and the bottom surface may have grooves. However, as described in the above embodiment, it is preferable that both the top surface and the bottom surface have grooves.

Further, in the above-described embodiment, the case where the groove along one side is parallel to the one side has been described, but the present invention is not limited to this. Further, the groove may not be linear over the entire surface, and only a part, for example, the central portion in the length direction may be linear. At that time, the end portion in the length direction of the groove may be curved.

Further, in the above-mentioned second embodiment, the case where the number of grooves along each side is three has been described as a suitable example, but the present invention is not limited to this, and the number of grooves along each side is two or more. All you need is.

The present invention is applicable to an image forming apparatus such as a printer, a copying machine, a facsimile, and a multifunction device having these functions.
The present invention is not limited to the above embodiments, and various modifications and modifications can be made without departing from the spirit and scope of the present invention. Therefore, in order to publicize the scope of the present invention, the following claims are attached.

3 ... Polygon mirror, 30 ... Resin body, 31 ... Reflective film, 301 ... Top surface (first bottom surface), 302 ... Bottom surface (second bottom surface), 310 ... Plane (first plane), 311 ... Groove (first groove) ), 312 ... groove (first groove), 313 ... groove (first groove), 314 ... groove (first groove), 320 ... plane (second plane), 321 ... groove (second groove), 322 ... groove (Second groove) 323 ... Groove (second groove) 324 ... Groove (second groove), 351 to 354 ... Side surface

Claims (20)

1. A prismatic resin body including a first bottom surface, a second bottom surface, and a plurality of side surfaces,
   A reflective film provided on each of the plurality of side surfaces is provided.
   The first bottom surface has a first plane having a polygonal outer shape and at least one first groove that is recessed with respect to the first plane and is along the first side surface of the plurality of side surfaces. One groove is a polygon mirror arranged so as not to intersect the diagonal line of the first plane.
2. The second bottom surface has a second plane having a polygonal outer shape and at least one second groove recessed with respect to the second plane and along the first side surface, and the second groove is the second groove. Arranged so as not to intersect the diagonal lines of the two planes,
   The polygon mirror according to claim 1.
3. The at least one first groove is one first groove.
   The at least one second groove is one second groove.
   The polygon mirror according to claim 2.
4. Each of the first groove and the second groove is a groove extending linearly in parallel with the first side surface.
   The polygon mirror according to claim 3.
5. The first groove and the second groove overlap each other when viewed in a direction perpendicular to the first plane.
   The polygon mirror according to claim 3 or 4.
6. The depth of the first groove and the depth of the second groove are the same.
   The polygon mirror according to claim 5.
7. When the thickness of the resin body between the first groove and the second groove is T, and the groove widths of the first groove and the second groove are W.
   1 ≦ W / T ≦ 2.5
   Meet, meet
   The polygon mirror according to claim 5 or 6.
8. The thickness of the resin body between the first groove and the second groove is T, the distance between the first groove and the first side surface, and the distance between the second groove and the first side surface are each set. When it is D,
   0.3 ≤ D / T ≤ 1
   Meet, meet
   The polygon mirror according to any one of claims 5 to 7.
9. The at least one first groove is a plurality of first grooves arranged side by side in a direction orthogonal to the first side surface.
   The at least one second groove is a plurality of second grooves arranged side by side in a direction orthogonal to the first side surface.
   The polygon mirror according to claim 2.
10. Each of the plurality of first grooves is a groove extending linearly in parallel with the first side surface.
    Each of the plurality of second grooves is a groove extending linearly in parallel with the first side surface.
    The polygon mirror according to claim 9.
11. When viewed in a direction perpendicular to the first plane, the plurality of first grooves and the plurality of second grooves overlap each other.
    The polygon mirror according to claim 9 or 10.
12. The depth of each of the plurality of first grooves is the same as the depth of each of the plurality of second grooves.
    The polygon mirror according to claim 11.
13. The thickness of the resin body between the plurality of first grooves and the plurality of second grooves is T, the total width of the plurality of first grooves, and the total width of the plurality of second grooves. When it is W
    1 ≦ W / T ≦ 2.5
    Meet, meet
    The polygon mirror according to claim 11 or 12.
14. The thickness of the resin body between the plurality of first grooves and the plurality of second grooves is T, the first side surface, and the first groove of the plurality of first grooves closest to the first side surface. And when each of the distance between the first side surface and the second groove closest to the first side surface among the plurality of second grooves is set to D.
    0.3 ≤ D / T ≤ 1
    Meet, meet
    The polygon mirror according to any one of claims 11 to 13.
15. The polygon mirror according to any one of claims 1 to 14,
    An optical deflector comprising a drive source for rotationally driving the polygon mirror.
16. Light source and
    An optical scanning device comprising the optical deflector according to claim 15, which deflects light emitted from the light source.
17. The sheet is equipped with an image forming unit that forms an image.
    The image forming part
    With the image carrier,
    The image forming apparatus according to claim 16, further comprising the optical scanning apparatus according to claim 16, wherein the surface of the image carrier is scanned with light.
18. A gold that includes a first bottom surface forming surface, a second bottom surface forming surface, and a plurality of side surface forming surfaces, and defines a prismatic cavity with the first bottom surface forming surface, the second bottom surface forming surface, and the plurality of side surface forming surfaces. It ’s a mold,
    The first bottom surface forming surface protrudes from the first plane forming surface having a polygonal outer shape and the first plane forming surface, and at least one along the first side surface forming surface among the plurality of side surface forming surfaces. A mold having one first protrusion, the first protrusion being arranged so as not to intersect the diagonal of the first plane forming surface.
19. The second bottom surface forming surface has a second plane forming surface having a polygonal outer shape, and at least one second protruding portion that protrudes from the second plane forming surface and is along the first side surface forming surface. , The first protrusion is arranged so as not to intersect the diagonal line of the second plane forming surface.
    The mold according to claim 18.
20. It is a manufacturing method for manufacturing a resin body used for a polygon mirror.
    The step of injecting the molten resin into the cavity of the mold according to claim 18 or 19.
    A step of forming the resin body by cooling and solidifying the molten resin injected into the mold inside the mold.
    A method for producing a resin body, comprising a step of releasing the resin body from the mold.

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