Optical sensor and image forming apparatus including the same

Abstract

To provide an optical sensor that can stabilize the position of a lens with respect to a light emitting element and a light receiving element to prevent variations of sensing performance.SOLUTION: An optical sensor comprises: a circuit board that has a first surface and a second surface on the opposite side of the first surface; a light emitting element and a light receiving element that are provided on the first surface of the circuit board; a lens unit including lens parts that are located on an optical path between the light emitting element and the light receiving element, and first columns and second columns that extend from the lens parts toward the circuit board; and electronic components that are mounted on the second surface of the circuit board. The circuit board has pore parts that are opened at least in the first surface and allow insertion of the first columns, and a contact target part with which the second columns are brought into contact on the first surface along a thickness direction of the circuit board. The electronic components are arranged in an area of the second surface corresponding to a rear face of the contact target part.SELECTED DRAWING: Figure 12

Description

[Technical Field]

[0001] The present disclosure relates to an optical sensor and an image forming apparatus including the same. [Background technology]

[0002] An optical sensor is known that includes a light-emitting element that emits measurement light to be irradiated onto a measurement object and a light-receiving element that receives reflected light from the measurement light. This optical sensor is used, for example, to detect patch images formed on an intermediate transfer belt of a tandem image forming apparatus for measuring toner concentration and color shift. Patent Document 1 discloses an optical sensor that includes a light-emitting element and a light-receiving element for detecting specularly reflected light from the patch image, and a lens unit that transfers light between these elements. The light-emitting element and the light-receiving element are mounted on a circuit board. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-128983 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above optical sensor, the position of the lens relative to the light emitting element and the light receiving element is not stable, which may cause variations in sensing performance.

[0005] An object of the present disclosure is to provide an optical sensor that can stabilize the position of a lens relative to a light-emitting element and a light-receiving element and suppress variations in sensing performance. [Means for solving the problem]

[0006] An optical sensor according to one aspect of the present disclosure comprises a circuit board having a first surface and a second surface opposite the first surface, a light-emitting element and a light-receiving element provided on the first surface of the circuit board, a lens unit including a lens portion located between the optical paths of the light-emitting element and the light-receiving element, and a first pillar and a second pillar extending from the lens portion toward the circuit board, and an electronic component mounted on the second surface of the circuit board, wherein the circuit board has at least a hole portion opened in the first surface through which the first pillar is inserted, and an abutment portion on the first surface against which the second pillar abuts along the thickness direction of the circuit board, and the electronic component is arranged in an area of ​​the second surface corresponding to the back surface of the abutment portion.

[0007] An image forming apparatus according to another aspect of the present disclosure includes an image forming unit that forms an image, and the optical sensor described above that irradiates light onto the image formed by the image forming unit and detects predetermined characteristics. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide an optical sensor that can stabilize the position of the lens relative to the light-emitting element and the light-receiving element and suppress variations in sensing performance. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view that schematically shows the internal structure of a color printer to which the optical sensor of the present disclosure is applied. [Figure 2] FIG. 2 is a perspective view showing an example of the arrangement of a concentration sensor, which is an example of an optical sensor. [Figure 3] 3A and 3B are schematic diagrams showing the principle of detecting black toner. [Figure 4] 4A and 4B are schematic diagrams showing the principle of color toner detection. [Figure 5] FIG. 5 is a cross-sectional view illustrating a portion of an optical sensor according to one embodiment of the present disclosure. [Figure 6]6(A) and (B) are perspective views showing the appearance of a portion of an optical sensor according to an embodiment of the present disclosure. [Figure 7] 7(A) is a top view of a portion of the optical sensor shown in FIG. 6, FIG. 7(B) is a bottom view, and FIG. 7(C) is a side view. [Figure 8] FIG. 8(A) is a perspective view of a bottom surface of a housing bottom plate of an optical sensor according to an embodiment of the present disclosure, and FIG. 8(B) is a perspective view of a top surface of the housing bottom plate. [Figure 9] FIG. 9 is a cross-sectional view taken along line IX-IX in FIG. 7(B). [Figure 10] FIG. 10 is a cross-sectional view taken along the line XX in FIG. 8(B), showing the state before the sensor substrate is mounted. [Figure 11] FIG. 11 is a plan view of a circuit board of an optical sensor according to one embodiment of the present disclosure. [Figure 12] FIG. 12 is a side view of a circuit board of an optical sensor according to one embodiment of the present disclosure. [Figure 13] FIG. 13 is a plan view of a circuit board of an optical sensor according to a modified embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] The optical sensor of the present disclosure will be described in detail below with reference to the drawings. The optical sensor of the present disclosure is a module that measures the physical properties of an object by irradiating the object with measurement light and receiving the reflected light. There are no particular limitations on the object to be measured, and it can be a solid, semi-solid, liquid, powder, etc. There are also no particular limitations on the physical properties to be measured, as long as they can be analyzed from the reflected light. For example, the optical sensor of the present disclosure is suitable for measuring the color and density of an object to be measured. In the embodiment described below, an optical sensor that is installed in a color printer to detect the density of toner used in image formation is exemplified.

[0011] [Color printer instructions] First, the configuration of a color printer to which the optical sensor of the present disclosure is applied will be described. FIG. 1 is a cross-sectional view that schematically shows the internal structure of a tandem color printer 1. The color printer 1 includes image forming units (image forming sections) 2Y, 2C, 2M, and 2Bk, an optical scanning device 23, an intermediate transfer unit 28, and a fixing unit 29, all housed in a main housing 10 (device main body). A paper output tray 11 is provided on the top surface of the main housing 10. A sheet output port 12 opens opposite the paper output tray 11. A manual paper feed tray 13 is provided on a side wall of the main housing 10, and a paper feed cassette 14 that stores sheets for automatic paper feeding, etc., is provided in the bottom of the main housing 10.

[0012] Image forming units 2Y, 2C, 2M, and 2Bk are units that form toner images of yellow, cyan, magenta, and black, respectively, and are arranged in tandem at a predetermined interval horizontally. Each image forming unit 2Y, 2C, 2M, and 2Bk includes a photosensitive drum 21 having a peripheral surface that supports an electrostatic latent image and a toner image, a charger 22 that charges the peripheral surface of the photosensitive drum 21, a developer 24 that applies developer to the electrostatic latent image to form a toner image, yellow, cyan, magenta, and black toner containers 25Y, 25C, 25M, and 25Bk, respectively, that supply toner of each color to the developer 24, a primary transfer roller 26 that performs primary transfer of the toner image formed on the photosensitive drum 21, and a cleaning device 27 that removes residual toner from the peripheral surface of the photosensitive drum 21. An optical scanning device 23 scans the peripheral surface of each photosensitive drum 21 with a beam in the main scanning direction as the scanned surface, forming an electrostatic latent image on the peripheral surface for forming a toner image.

[0013] The intermediate transfer unit 28 performs primary transfer of the toner images formed on the photosensitive drums 21. The intermediate transfer unit 28 includes a transfer belt 281 that rotates while contacting the circumferential surface of each photosensitive drum 21, and a drive roller 282 and a driven roller 283 around which the transfer belt 281 is wound. The toner images on the photosensitive drums 21 of each color are primarily transferred and superimposed onto the same location on the transfer belt 281. As a result, a full-color toner image is formed on the transfer belt 281. A secondary transfer roller 15 is disposed opposite the drive roller 282, sandwiching the transfer belt 281 between them to form a secondary transfer nip T. The full-color toner image on the transfer belt 281 is secondarily transferred onto a sheet at the secondary transfer nip T.

[0014] The fixing unit 29 includes a fixing roller 291 with a built-in heat source, and a pressure roller 292 that forms a fixing nip N together with the fixing roller 291. The fixing unit 29 applies heat and pressure to the sheet, onto which a toner image has been transferred in the secondary transfer nip T, in the fixing nip N, thereby performing a fixing process in which the toner is fused to the sheet. The sheet that has undergone the fixing process is discharged from the sheet discharge port 12 toward the paper discharge tray 11.

[0015] A density sensor 16 is disposed inside the main body housing 10. The density sensor 16 is an example of an optical sensor of the present disclosure. The density sensor 16 is disposed near the secondary transfer nip T, facing the outer circumferential surface of the transfer belt 281 on which the toner image is carried. The density sensor 16 optically detects the density of the toner image formed on the transfer belt 281 and converts it into an electrical signal.

[0016] FIG. 2 is a perspective view showing an example of the arrangement of the density sensor 16. In FIG. 2, the density sensor 16 is illustrated as a first density sensor 16A and a second density sensor 16B spaced apart from each other in the main scanning direction. The first density sensor 16A is disposed at a first density detection position DP1 on the toner carrying surface 28T of the transfer belt 281, and the second density sensor 16B is disposed at a second density detection position DP2, facing each other. The two density sensors 16A and 16B optically detect toner detection patches dp carried on the toner carrying surface 28T. The toner detection patches dp include, for example, density detection patches for detecting the toner concentration of each color and position detection patches for detecting the printing position of each color. The transfer belt 281 rotates in the direction indicated by the white arrow in FIG. 2. The first density sensor 16A detects the toner concentration along a first inspection line DL1 extending from the first density detection position DP1 in the sub-scanning direction. The second density sensor 16B detects the toner density along a second inspection line DL2 that extends in the sub-scanning direction from the second density detection position DP2. An embodiment in which only one of the first density sensor 16A and the second density sensor 16B is disposed opposite the transfer belt 281 may also be adopted.

[0017] [Toner detection principle] Next, the principle of optically detecting toner on transfer belt 281 will be described with reference to Figures 3 and 4. Figure 3 is a schematic diagram showing the detection principle of black toner BT, and Figure 4 is a schematic diagram showing the detection principle of color toner CT. A light-emitting element E1 and a light-receiving element E2 are arranged facing the toner carrying surface 28T of transfer belt 281. The light-emitting element E1 is, for example, an LED (Light Emitting Diode) that can emit light of a predetermined wavelength. The light-receiving element E2 is, for example, a PD (Photo Diode) that receives light, photoelectrically converts it, and outputs a current according to the amount of light.

[0018] FIG. 3A shows the light emission and reception state when there is no black toner BT on the transfer belt 281. The toner carrying surface 28T is a smooth surface that generates specular reflection when irradiated with light. Measurement light L1 is emitted from the light-emitting element E1. The measurement light L1 is irradiated at a predetermined emission angle θ1 toward the density detection position DP on the toner carrying surface 28T. The measurement light L1 is reflected by the toner carrying surface 28T, generating specularly reflected light L2. The specularly reflected light L2 is incident on the light-receiving element E2. The light-receiving element E2 outputs a current AM1 corresponding to the amount of light received.

[0019] FIG. 3B shows the light emission and reception state when black toner BT is present on the transfer belt 281. A portion of the measurement light L1 irradiated toward the toner carrying surface 28T is absorbed by the black toner BT. In other words, the specularly reflected light L2 is substantially not generated in the area of ​​the toner carrying surface 28T where black toner BT is present. As a result, the amount of specularly reflected light L2 incident on the light receiving element E2 decreases. The light receiving element E2 outputs a current AM2 corresponding to the reduced amount of light. Naturally, the relationship AM1>AM2 holds. Whether or not black toner BT is present is detected based on the fluctuation in the current output of the light emitting element E1 accompanying such a change in the amount of received specularly reflected light L2.

[0020] Figure 4(A) shows the light emission and reception state when no color toner CT is present on the transfer belt 281. Measurement light L1 is emitted from the light-emitting element E1. The emission optical system for measurement light L1 is adjusted so that measurement light L1 is irradiated onto the concentration detection position DP at an emission angle θ2 larger than the emission angle θ1 in Figure 3(A). Measurement light L1 is reflected by the toner carrying surface 28T, generating specularly reflected light L2. Light-receiving element E2 is positioned at a position where specularly reflected light L2 does not enter. Therefore, the output of light-receiving element E2 is essentially zero.

[0021] FIG. 4B shows the light emission and reception state when color toner CT is present on the transfer belt 281. A portion of the measurement light L1 irradiated toward the toner carrying surface 28T is irradiated onto the color toner CT and diffusely reflected. In other words, not all of the measurement light L1 becomes specularly reflected light L2, but a portion becomes diffusely reflected light L3. A portion of the generated diffusely reflected light L3 is incident on the light receiving element E2. The light receiving element E2 outputs a current AM3 corresponding to the amount of diffusely reflected light L3 received. The color toner CT is detected based on the change in output of the light receiving element E2 from 0 to AM3. The optical sensors described in the following embodiments use the above-described detection principle.

[0022] 5 is a cross-sectional view showing the concentration sensor 16 according to this embodiment. The concentration sensor 16 includes a sensor substrate 3, a lens unit 4, a first light-shielding wall 51, and a second light-shielding wall 52. The object to be measured by the optical sensor SM1 is a toner patch printed on the toner carrying surface 28T of the transfer belt 281.

[0023] The sensor substrate 3 includes a substrate 30 having a mounting surface 3M and an element group 3E arranged in a row on the mounting surface 3M. A circuit pattern for mounting the element group 3E is printed on the mounting surface 3M of the substrate 30. The sensor substrate 3 is arranged so that the mounting surface 3M faces the toner carrying surface 28T. A semiconductor substrate such as a silicon substrate may be used as the substrate 30, and the sensor substrate 3 may be mounted in such a manner that each element of the element group 3E is directly formed on the semiconductor substrate. Note that the substrate 30 may constitute the circuit board of the present disclosure, and the light receiving elements 34, 36 and the light emitting elements 33, 35 may be mounted on the circuit board. Alternatively, the element group may be formed on a silicon substrate. In this case, the sensor substrate 3 may be mounted on the substrate 30.

[0024] The element group 3E includes a first light-emitting / light-receiving pair 31 for detecting black toner BT and a second light-emitting / light-receiving pair 32 for detecting color toners CT. The first light-emitting / light-receiving pair 31 consists of a first light-emitting element 33 and a first light-receiving element 34 arranged at a predetermined interval on the mounting surface 3M. The second light-emitting / light-receiving pair 32 consists of a second light-emitting element 35 and a second light-receiving element 36 arranged at a predetermined interval on the mounting surface 3M at a position different from the first light-emitting / light-receiving pair 31.

[0025] The first light-emitting element 33 and the second light-emitting element 35 are LEDs that emit light of a predetermined wavelength. The first light-receiving element 34 and the second light-receiving element 36 are PDs that output a current corresponding to the amount of light received. The elements of the element group 3E are arranged in a line in the main scanning direction shown in FIG. 2. Specifically, the elements of the element group 3E are arranged in a line on the mounting surface 3M in the order of the first light-emitting element 33, the first light-receiving element 34, the second light-receiving element 36, and the second light-emitting element 35. The elements of the element group 3E do not necessarily have to be arranged in a strict line, and may be arranged in a line with an offset that is equivalent to a line. The arrangement direction of the element group 3E may also be the sub-scanning direction.

[0026] The lens unit 4 is disposed in front of the mounting surface 3M, i.e., between the sensor substrate 3 and the toner carrying surface 28T. The lens unit 4 includes a first lens portion 41, a second lens portion 42, a third lens portion 43, and a fourth lens portion 44 as lens portions for condensing light. These lens portions are located in the optical paths between the light-emitting element and the light-receiving element and transmit and receive light. On the optical path of the first light-emitting / receiving pair 31, the first lens portion 41 is disposed in front of the first light-emitting element 33, and the second lens portion 42 is disposed behind the first light-receiving element 34. On the optical path of the second light-emitting / receiving pair 32, the third lens portion 43 is disposed in front of the second light-emitting element 35, and the fourth lens portion 44 is disposed behind the second light-receiving element 36. The lens unit 4 further includes a holder portion 40 for holding each lens portion.

[0027] The first lens unit 41 collects light emitted by the first light-emitting element 33 to generate a first measurement light beam L11 that is irradiated as a spot at a predetermined position on the toner carrying surface 28T. The second lens unit 42 collects specularly reflected light L2 from the first measurement light beam L11 that is reflected by the toner carrying surface 28T and guides the light to the first light-receiving element 34. In other words, the first light-receiving element 34 is positioned to receive the specularly reflected light L2. The third lens unit 43 collects light emitted by the second light-emitting element 35 to generate a second measurement light beam L12 that is irradiated as a spot at a predetermined position on the toner carrying surface 28T. The fourth lens unit 44 collects diffusely reflected light L3 from the second measurement light beam L12 that is reflected by the toner carrying surface 28T and guides the light to the second light-receiving element 36. The second light-receiving element 36 is positioned to receive the optical image of the diffusely reflected light L3 generated by the fourth lens unit 44.

[0028] The first light-shielding wall 51 and the second light-shielding wall 52 are non-transparent members that do not allow light to pass through. The first light-shielding wall 51 is disposed in front of the mounting surface 3M, between the first light-emitting element 33 and the first light-receiving element 34. The first light-shielding wall 51 prevents light emitted from the first light-emitting element 33 from traveling directly toward the first light-receiving element 34 without passing through the toner carrying surface 28T. In other words, the first light-shielding wall 51 prevents light before being collected by the first lens unit 41 from being received by the first light-receiving element 34. The second light-shielding wall 52 is disposed in front of the mounting surface 3M, between the second light-emitting element 35 and the second light-receiving element 36. The second light-shielding wall 52 prevents light emitted from the second light-emitting element 35 from traveling directly toward the second light-receiving element 36. In other words, the second light-shielding wall 52 prevents light before being collected by the third lens unit 43 from being received by the second light-receiving element 36.

[0029] An open space OS is provided in front of the mounting surface 3M between the first light-emitting and light-receiving pair 31 and the second light-emitting and light-receiving pair 32, or in this embodiment, between the first light-receiving element 34 and the second light-receiving element 36. The open space OS is a non-light-shielding space in which there are essentially no light-shielding components. The open space OS is partitioned by the first light-shielding wall 51, the second light-shielding wall 52, and the lens unit 4. Note that the open space OS does not have to be a complete space, and small protrusions or structures that do not have an optical effect may be present.

[0030] If a light-blocking object (not shown) is present in the open space OS, in addition to the light that should be received and detected, reflected components from the light-blocking object may be incident on the first light-receiving element 34 and the second light-receiving element 36. In this case, stray light generated for some reason between the second lens unit 42 and the first light-receiving element 34 may be reflected by the light-blocking object and incident on the first light-receiving element 34. For example, stray light may be generated when a component of the first measurement light L11 that is diffusely reflected from the toner carrying surface 28T passes through the second lens unit 42, or when part of the specularly reflected light L2 is reflected by the light-receiving surface or mounting surface 3M of the first light-receiving element 34. Furthermore, stray light generated for some reason between the fourth lens unit 44 and the second light-receiving element 36 may be reflected by the light-blocking object and incident on the second light-receiving element 36.

[0031] In contrast, in the concentration sensor 16 of Figure 5, the area in front of the mounting surface 3M between the first light receiving element 34 and the second light receiving element 36 is an open space OS. Because there are no light-reflecting objects, such as light-blocking objects, in the open space OS, unnecessary reflected light is unlikely to occur. Therefore, stray light other than the specularly reflected light L2 or diffusely reflected light L3 that should be detected can be prevented from entering the first light receiving element 34 or the second light receiving element 36. Therefore, a concentration sensor 16 with improved sensing accuracy can be provided.

[0032] Fig. 6(A) is a bottom perspective view showing the appearance of a portion of concentration sensor 16 according to this embodiment, Fig. 6(B) is a top perspective view, Fig. 7(A) is a top view, Fig. 7(B) is a bottom view, and Fig. 7(C) is a side view of a portion of concentration sensor 16.

[0033] The concentration sensor 16 includes a housing 6 in addition to the sensor substrate 3 and lens unit 4 described above. As shown in FIG. 7(B), the sensor substrate 3 includes a substrate 30 and an element group 3E mounted on the substrate 30. As described above, the element group 3E includes a first light-emitting / light-receiving pair 31 for detecting black toner BT and a second light-emitting / light-receiving pair 32 for detecting color toner CT. The element group 3E is arranged in a row in the following order: a first light-emitting element 33, a first light-receiving element 34, a second light-receiving element 36, and a second light-emitting element 35.

[0034] The lens unit 4 includes a lens portion 4R that focuses light and a holder portion 40 that holds the lens portion 4R. As described above, the lens portion 4R includes a first lens portion 41, a second lens portion 42, a third lens portion 43, and a fourth lens portion 44. These four lens portions 41, 42, 43, and 44 are arranged in series in the arrangement direction of the element group 3E to form a lens block. The holder portion 40 has a rectangular parallelepiped shape that surrounds the lens block, and the top surface of the holder portion 40 is recessed in the area of ​​the lens block.

[0035] The lens unit 4 includes a pair of first support columns 45 and a pair of second support columns 46 for positioning the lens portion 4R. The pair of first support columns 45 and the pair of second support columns 46 protrude from the underside of the holder portion 40. Each of the first support columns 45 and each of the second support columns 46 extends from the lens portion 4R toward the circuit board 70 (described below). Each of the first support columns 45 protrudes from one diagonal corner of the rectangular lens unit 4. Each of the second support columns 46 is provided near the other diagonal corner of the lens unit 4 and is a convex portion that protrudes less from the underside of the holder portion 40 than the first support columns 45. The first support columns 45 are mainly positioning protrusions for the lens unit 4 in the horizontal direction (direction along the board). The second support columns 46 are positioning protrusions for the lens unit 4 in the height direction.

[0036] The housing 6 is a rectangular parallelepiped housing that includes a bottom plate 61 and side plates 62 and has a cavity capable of accommodating the lens unit 4. The lens unit 4 is fitted into the housing 6. The bottom plate 61 faces the underside of the lens unit 4. The side plates 62 stand upright from the periphery of the bottom plate 61 and cover the side surfaces of the lens unit 4. The bottom plate 61 and the side plates 62 are adhesively fixed at the outer periphery of the bottom plate 61 and are integrated together.

[0037] 8(A) is a perspective view of the bottom plate 61 of the housing 6 as seen from below, and FIG. 8(B) is a perspective view of the same as seen from above. The above-mentioned first light-shielding wall 51 and second light-shielding wall 52 are erected on the top surface 61A of the bottom plate 61. The side ends of the first light-shielding wall 51 and the second light-shielding wall 52 are connected by a pair of side walls 53. As a result, a rectangular cylindrical space is formed above the top surface 61A by the first light-shielding wall 51, the second light-shielding wall 52 and the pair of side walls 53. This rectangular cylindrical space is the open space OS in this embodiment.

[0038] A substrate accommodating portion 612 is provided on the lower surface 61B of the bottom plate 61. The substrate accommodating portion 612 is a recess that accommodates the sensor substrate 3. The bottom plate 61 has a plurality of holes formed therethrough in the thickness direction. The plurality of holes are a first opening 613, a second opening 614, a third opening 615, and four circular holes 616. When the sensor substrate 3 is accommodated in a predetermined position in the substrate accommodating portion 612, the first opening 613 is located opposite the first light-emitting element 33, the second opening 614 is located opposite the second light-emitting element 35, and the third opening 615 is located opposite the first light-receiving element 34 and the second light-receiving element 36.

[0039] Four circular holes 616 are formed near the four corners of the rectangular bottom plate 61. The first support column 45 and the second support column 46 of the lens unit 4 pass through the circular holes 616. The protruding portion of the first support column 45 that passes through the circular holes 616 is used to position the lens unit 4 in the horizontal direction. A substrate section 7 (FIG. 11), which will be described later, is attached to the underside of the bottom plate 61. The lower end surface of the second support column 46 abuts against the substrate section 7, which is in contact with the underside 61B of the bottom plate 61, thereby positioning the lens unit 4 in the vertical direction. A control IC, electronic components, connectors, etc. for operating each element of the sensor board 3 are mounted on the substrate section 7.

[0040] 9 is a cross-sectional view taken along line IX-IX in FIG. 7(B). FIG. 10 is a cross-sectional view taken along line XX in FIG. 8(B), illustrating a state before the sensor substrate 3 is attached to the substrate accommodating portion 612 of the bottom plate 61. The lens unit 4 is fitted into the housing 6 in such a manner that the lens portion 4R covers the bottom plate 61 on the sensor substrate 3. The first light-shielding wall 51 protrudes less from the bottom plate 61 than the second light-shielding wall 52. Therefore, the lens portion 4R, which is disposed so as to straddle the first light-shielding wall 51 and the second light-shielding wall 52, is inclined so that the side of the first light-shielding wall 51 is lower. The four lens portions 41, 42, 43, and 44 included in the lens portion 4R each have a convex lens surface on both the upper and lower surfaces of the lens unit 4.

[0041] 9 shows a state in which the first measurement light L11 and the second measurement light L12 are emitted from the density sensor 16 toward the density detection position DP where the measurement object TG is printed on the toner carrying surface 28T of the transfer belt 281. It also shows a state in which the specularly reflected light L2 and the diffusely reflected light L3 from the measurement object TG are incident on the density sensor 16. As described above, the measurement object TG is black toner BT and color toner CT.

[0042] The first lens unit 41 is disposed at a position facing the first opening 613 of the bottom plate 61. The first lens unit 41 collects light emitted from the first light-emitting element 33 and passing through the first opening 613, and irradiates the first measurement light L11 at the concentration detection position DP. The second lens unit 42 and the fourth lens unit 44 are disposed at a position facing the third opening 615 across the open space OS. The second lens unit 42 collects specularly reflected light L2 of the first measurement light L11 from the concentration detection position DP, and directs the light to the first light-receiving element 34. The first light-shielding wall 51 blocks light emitted from the first light-emitting element 33 that directly travels toward the first light-receiving element 34.

[0043] The third lens unit 43 is disposed at a position facing the second opening 614. The third lens unit 43 collects light emitted from the second light-emitting element 35 and passing through the second opening 614, and irradiates the concentration detection position DP with the second measurement light L12. The fourth lens unit 44 collects a portion of the diffusely reflected light of the second measurement light L12 generated at the concentration detection position DP, and causes the diffusely reflected light to be incident on the second light-receiving element 36 as diffusely reflected light L3. The second light-shielding wall 52 blocks light emitted from the second light-emitting element 35 that directly travels toward the second light-receiving element 36.

[0044] In this embodiment, the arrangement order of the element groups on the sensor substrate 3 is the arrangement order shown in FIG. 5 above. Therefore, the specularly reflected light L2 and the diffusely reflected light L3 pass through the open space OS. There are substantially no light-reflecting objects in the open space OS, i.e., between the first light-shielding wall 51 and the second light-shielding wall 52. Therefore, unnecessary reflected light is unlikely to occur between the first light-shielding wall 51 and the second light-shielding wall 52. Therefore, stray light other than the specularly reflected light L2 or the diffusely reflected light L3 that should be detected can be prevented from entering the first light-receiving element 34 or the second light-receiving element 36. Note that an arrangement order of the element groups 3E different from the above may also be applied to this embodiment.

[0045] The concentration sensor 16 further includes a substrate unit 7. Fig. 11 is a plan view of the substrate unit 7 of the concentration sensor 16 according to the present embodiment. Fig. 12 is a side view of the substrate unit 7 of the concentration sensor 16 according to an embodiment of the present disclosure.

[0046] The substrate unit 7 of the concentration sensor 16 supports the sensor board 3 and includes various electrical components. The substrate unit 7 is fixed to the main body housing 10 of the color printer 1. As shown in FIGS. 11 and 12, the substrate unit 7 has a circuit board 70, and an IC chip 71 and a connector 72 (all of which are electronic components) mounted on the circuit board 70. Note that other electronic components are also mounted on the circuit board 70, but their description will be omitted here.

[0047] The circuit board 70 is made of a rectangular plate-like member extending in a predetermined longitudinal direction. This direction is the same as the direction in which the first light-emitting element 33, the first light-receiving element 34, the second light-emitting element 35, and the second light-receiving element 36 are aligned (see FIG. 7). The circuit board 70 also has a dimension that extends outward beyond the aforementioned housing 6 (FIG. 12). The circuit board 70 has a first surface S1 and a second surface S2 opposite the first surface S1. These surfaces extend in the longitudinal and width directions of the circuit board 70. In other words, the first surface S1 and the second surface S2 are disposed on opposite sides of the thickness direction of the circuit board 70.

[0048] As an example, the circuit board 70 is made of epoxy glass (glass epoxy). The sensor board 3, which includes each light-emitting element and each light-receiving element, is mounted on a first surface S1 of the circuit board 70, approximately in the center in the longitudinal direction thereof. In FIG. 11, the first surface S1 is the back side of the paper. Wiring and circuits (not shown) are formed on the circuit board 70, and electrically connect each element of the sensor board 3, the IC chip 71, the connector 72, etc. to each other.

[0049] The circuit board 70 has a component mounting area M1 and a pair of component mounting prohibited areas M2. A pair of visual inspection patterns 70A are also formed on the circuit board 70. As an example, the circuit board 70 is made of a green base material, and the visual inspection patterns 70A are white linear portions formed on the board. In other words, the area sandwiched between the pair of visual inspection patterns 70A corresponds to the component mounting area M1. The areas longitudinally outward of each visual inspection pattern 70A correspond to the pair of component mounting prohibited areas M2. In this manner, in this embodiment, the component mounting area M1 and the component mounting prohibited areas M2 are separated by the visual inspection patterns 70A. In other embodiments, these areas may be separated by a groove or the like formed in the circuit board 70.

[0050] A first hole K1 and a second hole K2 are formed in the component mounting area M1. As an example, the first hole K1 is circular, and the second hole K2 is elongated along the longitudinal direction of the circuit board 70. The tips of the above-mentioned first support posts 45 are inserted into these holes (see the insertion portion 45T in FIG. 12). The inner diameter of the first hole K1 and the inner diameter in the lateral direction of the second hole K2 are set to correspond to the outer diameter of the insertion portion 45T. As a result, the first hole K1 and the second hole K2 restrain the pair of first support posts 45 in the direction along the surface (horizontal direction) of the circuit board 70 and are responsible for positioning the lens unit 4.

[0051] Furthermore, a pair of contact portions K3 are formed in the component mounting area M1. Each contact portion K3 is a part of the first surface S1 of the circuit board 70. The contact portions K3 may be positioned with a slight step relative to the first surface S1. Each contact portion K3 positions the lens unit 4 in the height direction by the tip surface of the second support 46 coming into contact with it (FIG. 12).

[0052] A first opening H1 and a second opening H2 are formed in the pair of component mounting prohibited areas M2. The first opening H1 is an elongated hole-shaped opening in the circuit board 70. The second opening H2 is a circular opening in the circuit board 70 on the opposite side from the first opening H1. Fixing bolts, screws, etc. (fixing members) are inserted through the first opening H1 and the second opening H2 when the density sensor 16 is attached to the main body housing 10 of the color printer 1. Note that the outer end of at least one of the first opening H1 and the second opening H2 may be shaped to open to the edge of the circuit board 70. In other words, these openings may be shaped like notches in the edge of the circuit board 70.

[0053] The IC chip 71 includes a core chip, which is an integrated circuit. The IC chip 71 is mounted on the circuit board 70 by COB (Chip On Board) and electrically connected by wire bonding. In this embodiment, the IC chip 71 is disposed in an area of ​​the component mounting area M1 adjacent to the component mounting prohibited area M2, as shown in FIGS. 11 and 12 .

[0054] The connector 72 is located near the visual inspection pattern 70A on the opposite side from the IC chip 71. As shown in Fig. 11, the IC chip 71 and the connector 72 are located on opposite sides of the width (short side) of the circuit board 70. The connector 72 receives a connector terminal (not shown) extending from the main body housing 10 of the color printer 1, and enables the transmission and reception of drive voltages and various signals between the main body housing 10 and the density sensor 16.

[0055] The IC chip 71 and the connector 72 are mounted on the second surface S2 of the circuit board 70 (FIG. 12). Note that the connector 72 is not shown in FIG.

[0056] A pair of first support posts 45 and a pair of second support posts 46 extend diagonally from the holder portion 40 (FIG. 6) of the lens unit 4. These support posts pass through four circular holes 616 formed in the bottom plate 61 (FIG. 8) of the housing 6. The pair of first support posts 45 are inserted into a first hole K1 and a second hole K2, respectively, formed in a circuit board 70 (FIG. 11) of the board portion 7 (FIG. 12). Meanwhile, the pair of second support posts 46 abut against a pair of abutment portions K3, respectively, formed in the circuit board 70 (FIG. 12).

[0057] As described above, in this embodiment, the circuit board 70 has the first hole portion K1 and the second hole portion K2 that are opened on the first surface S1 and through which the first support column 45 is inserted, and the contact portion K3 that receives the contact of the second support column 46 along the thickness direction of the circuit board 70 on the first surface S1. The IC chip 71 and the connector 72 are disposed in an area of ​​the second surface S2 that corresponds to the rear surface of the contact portion K3. Therefore, for example, as shown by the arrows in FIG. 12 , when heat from the heated IC chip 71 is transferred to the second support column 46 via the circuit board 70, the second support column 46 undergoes slight thermal expansion, thereby stabilizing the contact of the second support column 46 with the contact portion K3. This prevents the contact of the second support column 46 with the contact portion K3 from becoming unstable due to a slight tilt of the lens unit 4, and the height position of each lens portion of the lens unit 4 can be stably maintained. Furthermore, the positions of the lens portions relative to the light-emitting elements and light-receiving elements of the sensor substrate 3 can be stabilized, and variations in sensing performance can be suppressed.

[0058] The first hole K1 and the second hole K2 are not necessarily limited to holes that penetrate the circuit board 70, but may be recesses (holes) that open at least toward the first surface S1. The contacted portion K3 and the electronic component on its back surface do not necessarily need to completely overlap, but may overlap at least partially. The electronic components mounted on the second surface S2 of the circuit board 70 are not necessarily in close contact with the second surface S2, but may be mounted with a gap therebetween. Even in this case, heat can be transferred to the second support 46 side through slight heat transfer or conduction. The number of holes is not limited to two, but may be one, three, or more. The same applies to the contacted portion K3.

[0059] Furthermore, with the above configuration, it is possible to ensure sufficient space on the back surface of the circuit board 70 for mounting each electronic component.

[0060] Furthermore, in this embodiment, an IC chip 71 is disposed as an electronic component on the back surface of the contacted portion K3. With this configuration, heat generated by the IC chip 71 (driver IC) is transferred to the first surface S1 side of the circuit board 70, and unnecessary heat can be dissipated on the second surface S2 side.

[0061] In this embodiment, a connector 72 is disposed as an electronic component on the back surface of the contacted portion K3. With this configuration, heat generated by the connector 72 is transferred to the first surface S1 of the circuit board 70, and unnecessary heat can be dissipated on the second surface S2. Furthermore, the connector 72, which is a relatively large component, can be disposed on the opposite side of the sensor board 3, thereby making effective use of the space on the circuit board 70.

[0062] In this embodiment, the connector 72 has a plurality of legs (not shown) and is fixed to the circuit board 70 via the plurality of legs. In other words, there is a gap between the connector 72 and the second surface S2 of the circuit board 70. With this configuration, damage to the circuit board 70 is less likely to occur when the connector terminals on the main body housing 10 are fitted into the connector 72.

[0063] Furthermore, in this embodiment, the circuit board 70 has a first opening H1 and a second opening H2 (a pair of openings) through which screws (fixing members, not shown) that secure the circuit board 70 to the main body housing 10 are inserted, and the first hole K1 and the second hole K2 are disposed in an area (area R in FIG. 11 ) sandwiched between the first opening H1 and the second opening H2. With this configuration, the first hole K1 and the second hole K2 are disposed between the first opening H1 and the second opening H2, which can stably maintain their positions relative to the main body housing 10. This allows the positions of the lens units and elements relative to the main body housing 10, particularly in the direction parallel to the first surface S1 of the circuit board 70, to be maintained with high precision. Furthermore, with this configuration, the lenses of the lens unit 4 can be made smaller, allowing the concentration sensor 16 to be miniaturized.

[0064] Similarly, in this embodiment, each contact portion K3 is disposed in region R sandwiched between the first opening H1 and the second opening H2. With this configuration, each contact portion K3 is disposed between the first opening H1 and the second opening H2, where the position relative to the main body housing 10 can be stably maintained, thereby making it possible to maintain with high precision the position of each lens portion and each element relative to the main body housing 10, particularly the position in the direction perpendicular to the surface of the circuit board 70 (height direction). Furthermore, with this configuration, it is possible to make each lens of the lens unit 4 smaller, and thus to miniaturize the concentration sensor 16.

[0065] In this embodiment, the lens unit 4 has a pair of first support posts 45 and a pair of second support posts 46. The circuit board 70 has a pair of first hole portions K1 and second hole portions K2 through which the pair of first support posts 45 are inserted, and a pair of abutment portions K3 that receive the abutment of the pair of second support posts 46. Furthermore, when viewed from a direction perpendicular to the first surface S1, the line connecting the pair of first hole portions K1 and second hole portions K2 intersects with the line connecting the pair of abutment portions K3. This configuration makes it easy to position and adjust the height of each lens portion.

[0066] Furthermore, in this embodiment, the first support column 45 further has an abutment surface 45S that abuts against the first surface S1. With this configuration, mounted components such as a lens member are less likely to tilt, making it easier to mount them on the circuit board 70.

[0067] In the above, the first support 45 is disposed inside the abutment surface 45S and has an insertion portion 45T that is inserted into the first hole K1 and the second hole K2. That is, the outer diameter of the tip side of the first support 45 is set in two stages. With this configuration, it is possible to both insert the first support 45 into each hole and abut against the first surface S1.

[0068] In this embodiment, the color printer 1 also includes an image forming unit that forms an image, and a density sensor 16 (optical sensor) that irradiates light onto the image formed by the image forming unit and detects predetermined characteristics. This configuration prevents the second support column 46 from contacting the contact portion K3 of the lens unit 4 with instability due to a slight tilt of the lens unit 4, and the height position of each lens can be stably maintained. As a result, characteristics such as density and misalignment within the color printer 1 can be stably detected.

[0069] The density sensor 16 (optical sensor) according to the present disclosure and the color printer 1 including the same have been described above, but the present disclosure is not limited to this.

[0070] FIG. 13 is a plan view of the circuit board 70 of the substrate portion 7M of the concentration sensor 16 according to a modified embodiment of the present disclosure. As described above, FIG. 13 illustrates an example in which the first opening H1 has a notch structure. In this modified embodiment, another component mounting area M1 is disposed further outside the component mounting prohibited area M2, which includes the second opening H2, and a connector 72 is disposed in this other component mounting area M1. Furthermore, in this modified embodiment, the connector 72 is mounted on the first surface S1 of the circuit board 70. For example, if one of the multiple electronic components generates a large amount of heat, the one electronic component (connector 72) may be disposed in the other component mounting area M1 on the opposite side of the component mounting prohibited area M2 from the one component mounting area M1, as shown in FIG. 13. In this case, because the area (second opening H2) for fixing the concentration sensor 16 to the main body housing 10 of the color printer 1 is located between the two components, heat from the connector 72 can be dissipated toward the main body housing 10 via screws, bolts, or the like (not shown). In this case as well, by arranging the IC chip 71 on the rear surface side of the contact portion K3, the positioning of the lens unit 4 in the height direction by the second support column 46 can be stably achieved.

[0071] Furthermore, as an embodiment of the substrate according to the present disclosure, a semiconductor substrate such as a silicon substrate may be used as the element group 3E (FIG. 5), and a sensor substrate 3 may be used in which each element is directly formed on the semiconductor substrate. Here, when mounting a light receiving element or a light emitting element, the element group 3E may be mounted on a mounting surface 3M on a circuit board. The component configuration consists of a circuit board and the element group 3E, and a separate substrate for mounting the element group 3E is not necessarily required. Furthermore, when forming a light receiving element or a light emitting element on a semiconductor substrate, specifically when the element group 3E is directly formed using a semiconductor substrate such as a silicon substrate, the semiconductor substrate becomes the sensor substrate 3, and the sensor substrate 3 may be mounted on a circuit board. [Explanation of symbols]

[0072] 1 color printer 16 Density sensor (light sensor) 3 Sensor board 3E element group 3M mounting surface 30 boards 31, 32 First light-emitting / receiving pair, second light-emitting / receiving pair 33, 34 First light emitting element, first light receiving element 35, 36 Second light-emitting element, second light-receiving element 4 Lens unit 45 1st pillar 45S Contact surface 45T insertion part 46 Second pillar 6. Housing 61 Bottom plate 616 Circular hole 7. Circuit Board 70 Circuit Board 70A visual pattern 71 IC chips (electronic components) 72 Connectors (electronic components) H1 1st opening (opening) H2 2nd opening (opening) K1 1st hole (hole) K2 2nd hole (hole) K3 Abutted part S1 1st page S2 side 2

Claims

1. a circuit board having a first surface and a second surface opposite to the first surface; a light emitting element and a light receiving element provided on the first surface of the circuit board; a lens unit including a lens portion located between the light emitting element and the light receiving element and a first support and a second support extending from the lens portion toward the circuit board; an electronic component mounted on the second surface of the circuit board; Equipped with the circuit board has a hole through which the first support is inserted and a contact portion against which the second support is contacted on the first surface along a thickness direction of the circuit board, The electronic component is disposed in a region of the second surface corresponding to a rear surface of the contacted portion.

2. The optical sensor according to claim 1 , wherein the electronic component is an IC chip.

3. The optical sensor of claim 1 , wherein the electronic component is a connector.

4. The optical sensor of claim 3 , wherein there is a gap between the connector and the second surface of the circuit board.

5. the circuit board has a pair of openings through which fixing members for fixing the circuit board to the device body are inserted, The optical sensor according to claim 1 , wherein the hole is disposed in a region sandwiched between the pair of openings.

6. the circuit board has a pair of openings through which fixing members for fixing the circuit board to the device body are inserted, The optical sensor according to claim 1 , wherein the contact portion is disposed in a region sandwiched between the pair of openings.

7. the lens unit has a pair of the first support columns and a pair of the second support columns, the circuit board has a pair of the hole portions through which the pair of first support posts are inserted and a pair of the abutted portions against which the pair of second support posts abut, The optical sensor according to claim 1 , wherein, when viewed from a direction perpendicular to the first surface, a line connecting the pair of holes and a line connecting the pair of abutted portions intersect with each other.

8. The optical sensor according to claim 7 , wherein the first support has an abutment surface that abuts against the first surface.

9. The optical sensor according to claim 8 , wherein the first support post is disposed inside the contact surface and has an insertion portion that is inserted into the hole.

10. an image forming unit that forms an image; the optical sensor according to claim 1 , which irradiates the image formed by the image forming unit with light and detects a predetermined characteristic; An image forming apparatus comprising:

Images