JP6428035B2 - Image reading apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an image reading apparatus, and more particularly to a heat dissipation structure of a light source in the image reading apparatus.

An “image reading device” is a device that optically reads an image from a document and converts it into an electrical signal, and is also called an “image scanner”. An image reading apparatus is mainly used in an image forming apparatus as means for converting an image displayed on a document into data.
Some image reading apparatuses include a cover member or a housing (hereinafter abbreviated as “housing or the like”) that separates a built-in optical system from the outside (see, for example, Patent Document 1). This housing or the like prevents dust / dust from entering from the outside, and reduces image noise caused by dust / dust adhesion to the surface of the lens or mirror of the optical system.

However, on the other hand, heat tends to be trapped in a space separated from the outside by a housing or the like. As the heat accumulates, the temperature of the housing excessively increases, causing distortion due to thermal expansion in the lens or mirror of the optical system held by the housing, or the electrical characteristics of the photodetector. There is a risk that the image quality will be deteriorated if there is a deviation due to high temperature such as thermal noise.
As a device for preventing heat from entering a space separated from the outside by a housing or the like, for example, as in the image reading device disclosed in Patent Document 1, a space between the space and a line light source such as a xenon tube is transparent. A structure of partitioning with members is known. The transparent member transmits reflected light from the original toward the space, while blocking radiation heat directly from the line light source toward the space. This prevents the radiant heat from being trapped in the space.

JP 2003-344955 A

  As in the image reading device disclosed in Patent Document 1, in an image reading device that irradiates light on a document placed on the transparent glass from below, an optical system, a photodetector, a housing, and the like Are arranged in the region below the light source. Therefore, since the air heated by the heat of the light source does not enter the surroundings of the housing or the like and the space separated from the outside by the air, the risk of image quality deterioration due to the heat of the air is low. On the other hand, however, dust / dust such as paper dust easily falls from the original onto the glass and accumulates. Therefore, there is a high risk of noise occurring in the image due to the dust / dust blocking the light transmitted through the glass. .

  On the other hand, in recent image reading apparatuses, efforts have been made to reduce the size, such as using LEDs as light sources. This downsizing increases the degree of layout freedom when incorporating an image reading apparatus into a system such as an image forming apparatus. Therefore, the entire system can be made smaller, and a double-sided simultaneous reading function can be implemented in the system to increase the processing speed. It is advantageous in various respects, such as improving the reliability or improving the reliability by using the image forming apparatus as an image inspection means.

In particular, the downsized image reading apparatus can be mounted on the system in a posture in which light is irradiated onto a document located below, unlike the one disclosed in Patent Document 1. In this case, since the optical system and the light detector are located in the region above the document, the risk of noise occurring in the image due to dust / dust scattered from the document blocking the light from the light source is low.
However, in this image reading apparatus, unlike the one disclosed in Patent Document 1, in addition to the optical system and the photodetector, the housing and the like are located in the region above the light source. Therefore, the air heated by the heat of the light source rises by convection and tends to stay directly under the housing or the like. During the stay, a large amount of heat from the air enters the inside of the housing etc. by heat conduction through the surface of the housing etc. or by convection through the gap of the housing etc. and the housing etc. When the temperature with the internal space is raised, the temperature of the optical system or the photodetector held by the housing or the like can also rise. If this temperature rise causes distortion due to thermal expansion in the lens or mirror of the optical system, or if the electrical characteristics of the photodetector cause a deviation due to high temperature such as thermal noise, the image quality may deteriorate. Absent.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems, and in particular, an image reading that can prevent deterioration in image quality due to heat of a light source even if it is installed so as to irradiate light on a document located below. To provide an apparatus.

An image reading apparatus according to an aspect of the present invention is an apparatus that irradiates light on a sheet positioned below, detects light reflected by the sheet, and reads an image of the sheet from the light. A light guide member that has a long shape, guides light of a light emitting element incident from an end face in the longitudinal direction, and emits the light toward a sheet positioned below from a side surface extending in the longitudinal direction, and is reflected by the sheet An optical system including at least one mirror that reflects the emitted light, and at least one lens that focuses the light, a light detection unit that detects the light focused through the optical system, a light guide member, and an optical system , And a housing for holding the light detection unit . The light emitting element is disposed outside the outer wall of the housing. The position of the light emitting element may be outside the outer wall of the housing in the longitudinal direction of the light guide member. The mirror has an elongated plate shape, and the light guide member and the longitudinal direction of the mirror are arranged in parallel. The outer wall of the housing holds both ends of the mirror in the longitudinal direction, and separates the optical system and the photodetector from the heat radiation space extending above the light emitting element. In the heat dissipation space, air heated by the heat of the light emitting element is raised by convection and diffused.

  The bottom surface of the housing may include an opening for taking light reflected by the sheet into the housing. The at least one mirror may include a first mirror that first reflects the light that has passed through the opening, and a second mirror that reflects the light after the first mirror. Good. In this case, the vertical distance from the opening to the second mirror may be shorter than the vertical distance from the opening to the first mirror. Moreover, the length of the reflective surface of the first mirror in the longitudinal direction of the light guide member may be shorter than the length of the light guide member in the longitudinal direction.

The image reading apparatus may further include a cover member that covers the housing and the light emitting element from above. In this case, a vent hole may be formed in the portion of the cover member facing the space above the light emitting element.
The image reading apparatus may further include a heat insulating connecting member that covers an optical path from the light emitting element to the end surface in the longitudinal direction of the light guide member. Further, the outer wall of the housing may include an opening for securing an optical path from the light emitting element to the end face in the longitudinal direction of the light guide member. In this case, the connecting member may have a structure that closes the opening.

  The image reading apparatus may be provided in the image forming apparatus. The image forming apparatus includes: an image forming unit that forms an image on a sheet based on image data; and an image forming unit that is based on a comparison between data representing an image read by the image reading device and original image data. The image reading apparatus is arranged so that the sheet processed by the image forming unit passes below.

  In the image reading apparatus described above, the light emitting element is located on the outer side of the outer wall of the housing, particularly on the outer side of the optical system and the light detection unit. Therefore, even if the air heated by the heat of the light emitting element rises by convection, the heat of the air is not transmitted to either the optical system or the light detection unit. As a result, even if the image reading apparatus is installed so as to irradiate light on the document located below, it is possible to prevent the image quality from being deteriorated due to the heat of the light source.

(A) is a perspective view showing an appearance of the image forming apparatus according to the first embodiment of the present invention, and (b) is a straight line (b) between the automatic document feeder and the scanner shown in (a). -It is sectional drawing along (b). It is a perspective view which shows the external appearance of the image reading part by Embodiment 1 of this invention. FIG. 3 is a partial sectional view taken along a line III-III shown in FIG. 2. (A) is a perspective view which shows the external appearance of the illumination part shown by FIG. 2, (b) is the bottom view. FIG. 3 is a schematic side view of the image reading unit illustrated in FIG. 2. It is a perspective view of one modification of the image reading unit according to the first embodiment of the present invention. (A) is the partial disassembled perspective view of another modification of the image reading part by Embodiment 1 of this invention, (b) is the external appearance after assembling the components shown by (a). FIG. (A) is a partial exploded perspective view of still another modified example of the image reading unit according to the first embodiment of the present invention, and (b) is a diagram after assembling the components shown in (a). It is a perspective view which shows an external appearance. It is a front view which shows typically the structure of the image forming apparatus by Embodiment 2 of this invention. FIG. 10 is a block diagram illustrating a control system of the image forming apparatus illustrated in FIG. 9.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Embodiment 1
[Appearance of image forming apparatus]
FIG. 1A is a perspective view showing an appearance of an image forming apparatus according to Embodiment 1 of the present invention. The image forming apparatus 100 is a multi-function peripheral (MFP), and includes a scanner 120 at the top of the casing and a printer 130 at the bottom. Using these, MFP 100 realizes image reading, copying, and printing functions.

  Referring to FIG. 1A, an automatic document feeder (ADF) 110 is mounted on the upper surface of the MFP 100 so as to be openable and closable. A scanner 120 is built in a housing portion directly below the ADF 110, and an operation panel 101 is embedded in the front surface thereof. A gap 102 is opened directly below the scanner 120, and a paper discharge port 131 is installed behind the gap 102. That is, the MFP 100 is an in-body discharge type, and this gap 102 is used as a discharge space. A printer 130 is built in a housing portion between the periphery and the lower side of the gap 102, and a paper feed cassette 133 is attached to the bottom of the printer 130 so that it can be pulled out.

[ADF / scanner structure]
FIG. 1B is a cross-sectional view of the ADF 110 and the scanner 120 shown in FIG. 1A taken along line (b)-(b). Referring to FIG. 1B, the ADF 110 includes an image reading unit 200. The image reading unit 200 cooperates with the scanner 120 to simultaneously read images on both sides of the document while the ADF 110 passes the document once (one pass).

-ADF-
Referring to FIG. 1B, the ADF 110 includes a paper feed tray 111, a plurality of rollers 11A-11J, and a paper discharge tray 112. When the document DC0 is placed on the sheet feed tray 111, the end 114 facing the sheet feed port 113 is raised to bring the document DC0 into contact with the roller 11A of the sheet feed port 113. The plurality of rollers 11A,..., 11I sequentially convey the document DC0 on the paper feed tray 111 one by one toward the next roller 11B,. The last roller 11J discharges the document DC1 delivered from the previous roller 11I to the outside from the discharge port 115. The paper discharge tray 111 stacks the documents DC1 discharged from the paper discharge port 115.

  A path along which each document is conveyed by the plurality of rollers 11 </ b> A- 11 </ b> J is exposed at the bottom surface of the ADF 110 to face the top surface of the scanner 120, and passes directly below the image reading unit 200 inside the ADF 110. That is, the image reading unit 200 is located on the opposite side of the scanner 120 across this path. Accordingly, each document passes through the vicinity of the scanner 120 and the image reading unit 200 while being conveyed along this path, with the surfaces on different sides facing each other.

-Scanner-
Referring to FIG. 1B, the scanner 120 includes a contact glass 121, a platen glass 122, a slider 123, optical systems 124 and 125, a line sensor 126, and an image processing unit 127. Using these, the scanner 120 reads an image from an original conveyed by the ADF 110 or an original placed on the platen glass 122.

  The contact glass 121 blocks a slit opened on the upper surface of the scanner 120, and faces a part of the document conveyance path exposed on the bottom surface of the ADF 110 directly above the contact glass 121. The contact glass 121 has a long and narrow plate shape, the surface of which is parallel to the surface of the document passing through a part of the conveying path that faces the surface, and the longitudinal direction of the contact glass 121 is perpendicular to the part of the conveying path (see FIG. 1B is a direction perpendicular to the paper surface (hereinafter referred to as “main scanning direction”). The contact glass 121 is made of transparent glass or translucent resin.

The platen glass 122 closes an opening formed on the upper surface of the scanner 120 at a location different from the position of the contact glass 121. Since the platen glass 122 is exposed when the ADF 110 is opened, a document can be placed thereon. The platen glass 122 has a rectangular plate shape and is made of transparent glass or translucent resin.
The slider 123 is installed inside the scanner 120 and can reciprocate along the ceiling surface from directly below the contact glass 121 to the end of the platen glass 122 opposite to the contact glass 121. . The slider 123 includes a light source 128 and a mirror 129. The light source 128 is a linear light source parallel to the main scanning direction, and irradiates light from the upper surface of the slider 123 through the contact glass 121 or the platen glass 122 to the surface of the document placed thereon. The mirror 129 reflects the light reflected from the surface of the original and incident from above the slider 123 toward the optical systems 124 and 125.

  The optical system includes a pair of mirrors 124 and a lens 125, and uses them to focus the light sent from the slider 123. The pair of mirrors 124 can reciprocate in the same direction as the slider 123 at half speed in the same direction. Thereby, even when the slider 123 irradiates any part of the document placed on the platen glass 122, the optical path length of the reflected light from the document is kept constant.

The line sensor 126 includes an assembly of a plurality of photoelectric conversion elements juxtaposed in parallel with the main scanning direction, and detects the light focused by the optical systems 124 and 125 and converts it into an electrical signal.
The image processing unit 127 processes the electrical signal output from the line sensor 126, converts it into digital image data, and outputs it to the printer 130 or an external electronic device.
-Image reading unit-
The image reading unit 200 irradiates the surface of the document DC1 conveyed by the roller group 11A-11J of the ADF 110 with light, reads an image from the light reflected by the surface, and outputs an electrical signal. Convert to The image reading unit 200 further transmits an electric signal representing the read image to the image processing unit 127 of the scanner 120, and converts the electric signal into digital image data. This image data is also output to the printer 130 or an external electronic device.

The surface of the document DC1 conveyed by the ADF 110 that faces the image reading unit 200 is the back side of the surface that faces the contact glass 230 of the scanner 120. Therefore, while the original DC1 is conveyed once by the ADF 110, the images on both the front and back sides are read by the scanner 120 and the image reading unit 200.
[printer]
The printer 130 is an electrophotographic or ink-jet color printer, and prints an image on a sheet with toner or ink based on image data. Specifically, the printer 130 first transfers image data to be printed in response to an instruction from the user through the operation panel 101 or a request from a PC through the LAN, to the scanner 120, a USB memory, or a hard disk drive (HDD). ) Etc., or an electronic device such as a PC connected via a LAN. In particular, data representing an image read by the scanner 120 or the image reading unit 200 is captured from the image processing unit 127 of the scanner 120. Next, the printer 130 extracts a sheet of a desired size from the paper feed cassette 133 in accordance with a printing condition indicated by a user instruction or a PC request, and applies a desired color toner or ink to a desired area on the sheet. Distribution is performed at a density corresponding to the color coordinate value of each pixel indicated by the data. The image represented by the image data is reproduced on the sheet by the toner or ink distribution. In this way, the printer 130 discharges the sheet on which the image is printed from the discharge outlet 131 to the gap 102.

[Image reading unit structure]
FIG. 2 is a perspective view illustrating an appearance of the image reading unit 200. FIG. 3 is a partial cross-sectional view taken along the line III-III shown in FIG. Referring to FIGS. 2 and 3, the image reading unit 200 includes a housing 210, an illumination unit 260, an optical system 270, and a light detection unit 280.
-Case-
The entire housing 210 has a substantially rectangular parallelepiped shape that is long in the depth direction (X-axis direction in FIGS. 2 and 3). When the image reading unit 200 is installed inside the ADF 110, the depth direction of the housing 210 is parallel to the main scanning direction, and the bottom surface 211 of the housing 210 is parallel to the surface of the document that passes immediately below.

  The housing 210 is a member that holds the illumination unit 260, the optical system 270, and the light detection unit 280. Specifically, the bottom surface 211 of the housing 210 includes a protrusion 212 extending in parallel with the depth direction, that is, the main scanning direction, and holds the illumination unit 260 therein. The outer wall 213 of the housing 210 surrounds a space SPC (hereinafter referred to as “internal space”) as shown in FIG. 3. The inner surface of the outer wall 213 and the upper surface 214 hold the optical system 270. The upper surface 214 further holds the light detection unit 280.

−Lighting section−
4A is a perspective view showing the appearance of the illumination unit 260, and FIG. 4B is a bottom view of the illumination unit 260. FIG. Referring to FIG. 4, the illumination unit 260 includes a light emitting element 261, a light guide member 262, and a holding member 263. The light emitting element 261 is a point light source such as an LED. The light guide member 262 has an elongated rectangular parallelepiped shape and is made of a material that is transparent or translucent to the light of the light emitting element 261 such as glass or acrylic resin. The holding member 263 has a substantially flat rectangular parallelepiped shape and is made of a material that does not transmit light of the light emitting element 261. The length of the holding member 263 is substantially equal to the length of the light guide member 262. Of the rectangular bottom surface of the holding member 263, a recess 264 is formed at the center in the short side direction (vertical direction in FIG. 4B). The recess 264 extends from end to end in the longitudinal direction of the holding member 263 (lateral direction in FIG. 4B). One light guide member 262 is fitted into both edges of the recess 264 parallel to the longitudinal direction. A slit 265 in the longitudinal direction is opened in the middle between the two light guide members 262. The slit 265 passes through the holding member 263 from the bottom surface to the top surface (in a direction perpendicular to the paper surface in FIG. 4B). As shown in FIG. 4A, the longitudinal end face 266 of the holding member 263 is exposed at the longitudinal end face 267 of the light guide member 262, as shown in FIG. 4B. Further, the side surface 268 of the light guide member 262 is exposed in the recess 264. A light emitting element 261 is disposed just outside the end face 267 in the longitudinal direction of the light guide member 262. Thereby, the light of the light emitting element 261 enters the end surface 267 of the light guide member 262 and exits downward from the side surface 268 of the light guide member 262 exposed in the recess 264. The light emitted from the side surface 268 is uniform throughout the side surface 268. Thus, the illumination unit 260 functions as a line light source.

  2 and 3 again, the light guide member 262 and the holding member 263 (shown by broken lines in FIG. 2) are each in the horizontal direction, that is, the main scanning direction (FIG. 2, FIG. 2). In FIG. 3, it is installed in parallel with the X-axis direction). An opening 219 is provided in the lower part of the outer wall 213 of the housing 210 facing the installation location. As shown in FIG. 3, the longitudinal ends of the light guide member 262 and the holding member 263 extend outside the outer wall 213 through the opening 219, and the respective longitudinal end surfaces 266 and 267 are formed. It is close to the light emitting element 261. In this way, an optical path from the light emitting element 261 to the end face 267 in the longitudinal direction of the light guide member 262 is secured by the opening 219 of the outer wall 213.

  The bottom surface 211 of the housing 210 includes an opening 215 at a portion facing the recess 264 of the holding member 263. The opening 215 is closed with a contact glass 269. When the image reading unit 200 is incorporated in the ADF 110, the contact glass 269 faces a part of the document conveyance path that passes directly below the contact glass 269. The contact glass 269 has an elongated plate shape whose longitudinal direction is parallel to the main scanning direction (X-axis direction), and the surface thereof is parallel to the surface of the document that passes immediately below. Since the contact glass 269 is formed of glass or resin that is transparent to the light of the light emitting element 261, the light emitted downward from the side surface 268 of the light guide member 262 exposed in the concave portion 264 of the holding member 263 is used. Light that is transmitted toward the document immediately below and reflected upward by the document is transmitted toward the slit 265 of the holding member 263.

-Optical system and light detector-
2 and 3, the optical system 270 is a reduction optical system, and includes five mirrors 271-275 and an imaging lens array 276. Each of these mirrors 271-275 has an elongated plate shape. The first to fourth mirrors 271-274 are held by the outer walls 213 of the casing 210 at both ends in the longitudinal direction, and the fifth mirror 275 is held by the protrusions 216 of the upper surface 214 of the casing 210 at both ends in the longitudinal direction. ing. The first to fourth mirrors 271-274 have a reflecting surface accommodated in the internal space SPC of the housing 210, and the fifth mirror 275 has a reflecting surface accommodated inside the protrusion 216 of the housing 210. Each of the five mirrors 271-275 has a longitudinal direction parallel to the main scanning direction (X-axis direction). The imaging lens array 276 is held on the upper surface 214 of the housing 210, and the side on which light is incident is directed to the inside of the protruding portion 216 of the housing 210. As described above, the elements 271 to 276 of the optical system 270 are all disposed above the light guide member 262, and pass through the contact glass 269 and the slit 265 of the holding member 263 from the surface of the document located below the light guide member 262. Light incident on the internal space SPC of the housing 210 is focused.

  The light detection unit 280 is held on the upper surface 214 of the housing 210 and is connected to the end of the imaging lens array 276. The imaging lens array 276 emits the focused light through the optical system 270 from the end thereof to the light detection unit 280. The light detection unit 280 incorporates a solid-state image sensor such as a CCD or a CMOS, and uses it to detect light emitted from the imaging lens array 276 and convert it into an electrical signal. The light detection unit 280 further includes a signal output terminal 281 through which an electric signal converted from the detected light is output.

  FIG. 5 is a schematic side view of the image reading unit 200. This side view schematically represents the appearance of the image reading unit 200 installed in the ADF 110 when viewed from the main scanning direction (X-axis direction in FIG. 5). A dashed-dotted line LPT shown in FIG. 5 represents an optical path when the light irradiated downward by the illumination unit 260 is reflected by the original DCM. However, as understood from FIG. 2, the actual optical path LPT is located in the inner space SPC of the casing 210, that is, on the back side of the outer wall 213 of the casing in FIG.

  Referring to the optical path LPT shown in FIG. 5, the light emitted downward from the side surface 268 of the light guide member 262 exposed on the bottom surface of the holding member 263 of the illumination unit 260 passes through the contact glass 269, Reflected upward by the original DCM passing directly under the illumination unit 260. The reflected light passes through the contact glass 269 and enters the internal space SPC of the housing 210 through the slit 265 of the holding member 263. Since the first mirror 271 is disposed directly above the slit 265, the light that has entered the internal space SPC is first reflected by the first mirror 271. Thereafter, the light is reflected in the order of the second mirror 272, the third mirror 273, and the fourth mirror 274 to escape from the internal space SPC of the housing 210 to the inside of the protruding portion 216 of the upper surface 214, and is reflected by the fifth mirror 275. The light is reflected and enters the imaging lens array 276. The light is further focused by the imaging lens array 276 and imaged on the light receiving surface 282 of the light detection unit 280.

  As described above, the five mirrors 271-275 have a sufficient portion of the optical path LPT from the original DCM to the imaging lens row 276 than the portion from the imaging lens row 276 to the light receiving surface 282 of the light detection unit 280. Make it long. As a result, the image in which the reflected light from the area is connected to the light receiving surface 282 of the light detection unit 280 is sufficiently longer in the main scanning direction than the area of the original DCM that is simultaneously irradiated with light from the illumination unit 260. short. Thus, the five mirrors 271-275 and the imaging lens array 276 function as a reduction optical system.

  In a reduction optical system, generally, the shorter the optical path length from a mirror to an imaging lens, the smaller the size of the reflecting surface required for the mirror. Accordingly, the five mirrors 271-275 have a short required length of the reflecting surface in the main scanning direction in the order in which the light traveling along the optical path LPT is reflected. Further, as shown in FIG. 5, the first mirror 271 is held as close as possible to the upper surface 214 of the casing 210 and is separated from the original DCM as much as possible. On the other hand, the distance in the vertical direction (Z-axis direction in FIG. 5) from the opening 215 of the bottom surface 211 of the housing 210 to the second mirror 272 is larger than the distance in the vertical direction from the opening 215 to the first mirror 271. short. The same applies to the third mirror 273 and the fourth mirror 274. That is, the Z coordinates of the second to fourth mirrors 272-274 represent the middle between the Z coordinate of the opening 215 and the Z coordinate of the first mirror 271. Thereby, all of the five mirrors 271-275 can sufficiently shorten the length in the main scanning direction (X-axis direction) than the length of the light guide member 262 in that direction. For example, as shown in FIG. 3, the length LR1 of the reflective surface required for the first mirror 271 and the length LR4 of the reflective surface required for the fourth mirror 274 are both the length of the light guide member 262. It is sufficiently shorter than LLL.

[Light source heat dissipation structure]
2 and 3, the bottom surface 211 of the casing 210 includes a portion 217 that protrudes outward in the horizontal direction, that is, the main scanning direction (X-axis direction in FIGS. 2 and 3) from the outer wall 213. The light emitting element 261 is held by the portion 217. As a result, the light emitting element 261 is disposed outside the outer wall 213, particularly the inner space SPC, and the region adjacent to the vertical direction (Z-axis direction in FIGS. 2 and 3). (To be more precise, the horizontal coordinate (X coordinate) of the light emitting element 261 represents a position outside the horizontal coordinate of the outer wall 213.) The outer wall 213 is also an optical system from the space HPT extending above the light emitting element 261. 270 and the light detection unit 280 are separated from each other.

  This space HPT is used as a “heat dissipating space” in which air heated by the heat of the light emitting element 261 rises by convection. Here, since the optical system 270 is a reduction optical system, the lengths of the component mirrors 271-275 in the main scanning direction (X-axis direction) are sufficiently larger than the length of the light guide member 262 in that direction. It can be shortened. Therefore, it is easy to expand the heat radiation space HPT in the main scanning direction by reducing the length of the overhanging portion 217 in that direction while keeping the entire length of the casing 210 in the main scanning direction constant. . Further, since the volume of the heat radiation space HPT increases with this expansion, the housing 210 has the ability to release the heat of the light emitting element 261 to the outside air (hereinafter referred to as “heat radiation capacity” while maintaining the entire length in the main scanning direction. It is easy to make it high enough.

  As shown in FIGS. 2 and 3, the heat dissipation space HPT is located outside the outer wall 213 of the housing 210 and is separated from the internal space SPC of the housing 210 by the outer wall 213. As a result, even if the air flow HTF heated by the heat of the light emitting element 261 rises and diffuses into the heat dissipation space HPT, it does not enter the periphery of the light guide member 262 and the internal space SPC. Thus, heat propagation from the air flow HTF to the internal space SPC is suppressed.

  In the ADF 110 shown in FIG. 1B, the depth direction of the image reading unit 200, that is, the main scanning direction (X-axis direction in FIG. 2) is the horizontal direction, and the vertical direction (Z in FIG. 2). (Axial direction) is slightly inclined from the vertical direction. As is clear from FIG. 3, unless this inclination (in FIG. 3, the inclination of the Z axis with respect to the vertical direction) is excessive, the air flow HTF warmed by the heat of the light emitting element 261 flows from the heat radiation space HPT to the outer wall 213 of the housing 210. The internal space SPC does not escape through the opening 219. Therefore, since the heat of the light emitting element 261 does not stay in the internal space SPC, there is no danger that the temperature of either the optical system 270 or the light detection unit 280 will rise excessively.

[Advantages of Embodiment 1]
In order to realize the double-sided simultaneous reading function, an image reading device of a type that reads an image by irradiating light to a document passing immediately below is necessary. The image forming apparatus 100 according to the first embodiment of the present invention includes an image reading unit 200 as this type of image reading apparatus. In the image reading unit 200, the light emitting element 261 is disposed outside the outer wall 213 of the housing 210. Therefore, the air flow HTF warmed by the heat of the light emitting element 261 rises and diffuses into the heat dissipation space HPT, and therefore, from the flow HTF to the internal space SPC of the housing 210, particularly the optical system 270 and the light detection unit 280. An excessive amount of heat is not transmitted to Thereby, since the heat of the light emitting element 261 is not trapped in the internal space SPC, there is no risk that the temperature of either the optical system 270 or the light detection unit 280 excessively increases. In this way, even if the image reading unit 200 is installed so as to irradiate light on a document that passes directly below, the image reading unit 200 can prevent deterioration in image quality due to heat of the light emitting element 261. As a result, the image forming apparatus 100 has high reliability for the image reading function.

[Modification]
(A) The image forming apparatus 100 according to the first embodiment is an MFP. In addition, the image forming apparatus according to the present invention may be an apparatus specialized for any function of a printer, a copier, a scanner, or a FAX.
(B) The image read by the image reading unit 200 is converted into digital image data by the image processing unit 127 of the scanner 120. In addition, the image reading unit 200 may include a dedicated image processing unit, and the read image may be converted into data by the image processing unit.

(C) The light emitting element 261 of the illumination unit 260 may be a light source using another light emitting method such as a halogen lamp, a fluorescent lamp, or an organic EL instead of the LED. Further, the light emitting element 261 may be disposed only at one end instead of being disposed at both ends of the light guide member 262.
The elongated shape of the light guide member 262 of the illumination unit 260 may be a circle or other polygonal cross section instead of an elongated rectangular parallelepiped, or may be a thin plate. Further, the number of the light guide members 262 may be other than “2”.

In any case, the portion of the light source of the illumination unit 260 that emits heat due to light emission is outside the outer wall 213 of the housing 210, particularly outside the optical system 270 and the light detection unit 280. It only has to be arranged. More precisely, it is only necessary that the horizontal coordinate of the heat radiation portion of the light source represents a position outside the horizontal coordinate of the outer wall 213.
(D) In the example shown in FIGS. 2 and 3, both longitudinal ends of the first to fourth mirrors 271-274 pass through the slits 218 formed in the outer wall 213 of the casing 210, and the heat dissipation space HPT. Protruding to These projecting portions and the portion that contacts the outer wall 213 may be formed or covered with a member having particularly high heat insulation. As a result, even if these protruding portions and the outer wall 213 are exposed to the air flow HTF warmed by the heat of the light emitting element 261, the inner space SPC of the casing 210, particularly, the inside thereof is positioned through these portions. The amount of heat that propagates to the reflecting surface of the mirrors 271 to 275 can be further reduced.

  In addition, unlike FIGS. 2 and 3, the gap between the slit 218 of the outer wall 213 and the mirrors 271 to 274 may be closed by a heat insulating member. In addition, the structure for holding the mirrors 271-274 is provided inside the outer wall 213 without opening any through holes such as slits 218 in the outer wall 213, so that the inner space SPC is completely formed on the outer wall 213 from the heat radiation space HPT. May be blocked.

  (E) The optical system 270 may be a reduction optical system, and the combination of the mirrors 271-275 and the imaging lens array 276 shown in FIGS. 2 and 5 is merely an example. A mirror that first reflects light incident from the original DCM into the opening 215 of the bottom surface 211 of the casing 210 is called a “first mirror”, and a mirror that reflects the light after the first mirror is referred to as a “second mirror”. Called the mirror. In this case, at least one of the second mirrors is arranged such that the vertical distance from the opening 215 to the mirror is shorter than the vertical distance from the opening 215 to the first mirror. Just do it. More precisely, at least one of the second mirrors only needs to have coordinates in the vertical direction between the coordinates of the opening 215 and the coordinates of the first mirror in that direction. With such an arrangement, as in the arrangement shown in FIG. 5, the first mirror is sufficiently separated from the original DCM, so that the length of each mirror in the main scanning direction is the length of the light guide member 262. This can be sufficiently shortened. Accordingly, the casing 210 can easily obtain a sufficiently high heat dissipation capability by expanding the heat dissipation space HPT in that direction while maintaining the entire length of the casing 210 in the main scanning direction constant. . That is, it is possible to ensure a sufficient heat dissipation space HPT without enlarging the entire housing 210.

If the size of the casing 210 is loose, such as when there is a margin in the main scanning direction, the arrangement of the optical system elements can be freely changed from that shown in FIG. is there. For example, the vertical distance from the opening 215 to any second mirror may be longer than the vertical distance from the opening 215 to the first mirror.
(F) As shown in FIG. 2, the elements 275 and 276 of the optical system 270 and the light detection unit 280 are exposed on the upper surface 214 of the housing 210, and the optical system 270 is outside the outer wall 213. The ends of the elements 271 to 274 and the light emitting element 261 are exposed. The image reading unit may further include a cover member for covering and protecting the entire exposed elements.

  FIG. 6 is an exploded perspective view showing an appearance of an example 201 of an image reading unit provided with such a cover member 501. Referring to FIG. 6, the cover member 501 covers the casing 210 and the light emitting element 261 from above. Thereby, it is possible to prevent the light emitting element 261, the optical system 270, and the light detection unit 280 from being adversely affected by dust and adhesion of dust, and from being inadvertently interfered by the user.

  With further reference to FIG. 6, a plurality of vent holes 503 are formed in the upper surface 502 of the cover member 501 at the portion facing the heat radiation space HPT in both ends in the main scanning direction (X-axis direction in FIG. 6). Yes. Since these vent holes 503 communicate the heat radiation space HPT to the space outside the cover member 501, the air flow HTF heated by the heat of the light emitting element 261 rises to the heat radiation space HPT and then further rises through the vent holes 503. Continue to diffuse into the open air. Therefore, even if the heat dissipation space HPT is covered with the cover member 501, the heat dissipation capability of the housing 210 is not impaired.

  If the thermal conductivity of the portion of the cover member 501 facing the heat radiation space HPT is sufficiently high, the vent hole 503 may not be formed in that portion. In addition, the portion may include a heat radiating portion having high thermal conductivity instead of the vent hole 503. The heat rising from the light emitting element 261 to the heat radiation space HPT by convection is dissipated to the outside air through the portion of the cover member 501 itself or the heat radiation portion included in the portion. Therefore, even if the heat dissipation space HPT is covered with the cover member 501, the heat dissipation capability of the housing 210 is not impaired.

(G) In the image reading unit 200, as shown in FIG. 4, the light emitting element 261 is disposed with a gap from the longitudinal end surface 267 of the light guide member 262 exposed on the longitudinal end surface 266 of the holding member 263. Has been. In addition, the gap between the end surface 267 of the light guide member 262 and the light emitting element 261 may be covered with a connecting member.
FIG. 7A is a partial exploded perspective view showing the vicinity of the connecting member 601 in an example 202 of such an image reading unit. FIG. 7B is a perspective view showing an appearance after the components shown in FIG. 7A are assembled. Referring to FIG. 7, the connecting member 601 fixes the light emitting element 261 to the bottom surface 211 of the casing 210, and covers the optical path from the light emitting element 261 to the end surface of the light guide member 262 to prevent leakage of light to the outside. prevent. The connecting member 601 is further made of a material such as a highly heat-insulating resin or ceramic, and blocks heat from the light emitting element 261 from the light guide member 262. Thereby, the heat of the light emitting element 261 can be prevented from being transmitted to the internal space SPC of the housing 210 through either the light guide member 262 or the holding member 263.

  FIG. 8A is a partial exploded perspective view showing the vicinity of the connecting member 701 in another example 203. FIG. FIG. 8B is a perspective view showing an appearance after the components shown in FIG. 8A are assembled. Referring to FIG. 8, the connecting member 701 has a structure that closes the opening 219 at the bottom of the outer wall 213. As a result, the connecting member 701 has a function of fixing the light emitting element 261 and preventing light leakage to the outside, and dust and dust from the space SP1 around the light emitting element 261 to the space SP2 around the light guide member 262. It has a function to prevent intrusion. The connecting member 701 is made of a material such as resin or ceramic having higher heat insulation properties, and shields the space SP2 around the light guide member 262 from the space SP1 around the light emitting element 261. Thereby, the heat of the light emitting element 261 can be prevented from being transmitted to the internal space SPC of the housing 210 through the surrounding air and other members arranged in the opening 219 at the lower part of the outer wall 213.

The connecting members 601 and 701 shown in FIGS. 7 and 8 leave the optical path from the light emitting element 261 to the end face 267 of the light guide member 262 in a space. In addition, the space may be closed with a member that is transparent or translucent to the light of the light emitting element 261. Further, the entire opening 219 under the outer wall 213 may be closed by a similar transparent or translucent member.
(H) In the example shown in FIG. 3, the end surface 267 in the longitudinal direction of the light guide member 262 is located outside the outer wall 213. In addition, when the optical path from the light emitting element 261 to the end surface 267 of the light guide member 262 is covered with the connecting member 601 or 701 as shown in FIG. 7 or FIG. 8, the light emitting element 261 is positioned outside the outer wall 213. As long as it does, the end surface 267 of the light guide member 262 may be located inside the outer wall 213.

<< Embodiment 2 >>
The image forming apparatus according to the second embodiment of the present invention is a color printer, and includes an image reading unit as an inline sensor in a paper discharge unit.
[Structure of image forming apparatus]
FIG. 9 is a schematic front view showing the structure of the printer 800 according to the second embodiment of the present invention. In FIG. 9, elements inside the printer 800 are depicted as if the front surface of the housing is seen through. Referring to FIG. 9, the printer 800 is a color laser printer, for example, and includes an image forming unit, an operation unit 50, and a control unit 60. The image forming unit is a core mechanism for forming an image on a sheet based on image data, and includes a feeding unit 10, an image forming unit 20, a fixing unit 30, and a paper discharge unit 40. The feeding unit 10 feeds the sheets SHT one by one to the image forming unit 20. The image forming unit 20 forms a toner image on the sheet SH2 sent from the feeding unit 10. The fixing unit 30 thermally fixes the toner image. The paper discharge unit 40 discharges the sheet SH3 on which the toner image is fixed out of the housing. The operation unit 50 receives a print request and image data to be printed through a user operation or communication with an external electronic device, and transmits them to the control unit 60. The control unit 60 controls operations of other elements in the printer 800 based on information from the operation unit 50.

-Feeding section-
Referring to FIG. 9, in the feeding unit 10, the paper feed cassette 11 can accommodate a plurality of sheets SHT. The material of these sheets SHT is paper or resin. The roller groups 12, 13, and 14 send out the uppermost sheet SH 1 among the sheets SHT in the sheet feeding cassette 11 to the image forming unit 20.

-Image forming part-
Referring to FIG. 9, in the image creating unit 20, the image creating unit 21 first exposes the surface of the photosensitive drum 25 based on the image data, and creates an electrostatic latent image on the surface. Next, the image forming unit 21 develops the electrostatic latent image with toner of each color of yellow (Y), magenta (M), cyan (C), and black (K). The obtained toner image is transferred from the surface of the photosensitive drum 25 to the surface of the intermediate transfer belt 23 by an electric field between the primary transfer roller 22 and the photosensitive drum 25. Since the image forming timing is shifted between the image forming units 21 in accordance with the rotation of the intermediate transfer belt 23, the four color toner images are transferred from the photosensitive drum 25 to the same position on the surface of the intermediate transfer belt 23. Thus, one color toner image is formed. This color toner image is transferred by the electric field between the intermediate transfer belt 23 and the secondary transfer roller 24 to the surface of the sheet SH <b> 2 that has been fed from the feeding unit 10 to the nip between the both 23 and 24. Thereafter, the secondary transfer roller 24 sends the sheet SH <b> 2 to the fixing unit 30.

-Fixing part-
Referring to FIG. 9, in the fixing unit 30, the sheet SH <b> 2 is passed from the image forming unit 20 to the nip between the fixing roller 31 and the pressure roller 32. The fixing roller 31 applies heat from a built-in heater to the surface of the sheet SH2. The pressure roller 32 applies pressure to the heated portion of the sheet SH2 and presses it against the fixing roller 31. The toner image transferred to the sheet SH2 is fixed on the surface of the sheet SH2 by the heat from the fixing roller 31 and the pressure from the pressure roller 32.

-Output section-
Referring to FIG. 9, the paper discharge unit 40 includes an inline sensor 400 in addition to the guide plate 41, the paper discharge port 42, and the paper discharge roller 43. The guide plate 41 forms a passage for guiding the sheet SH2 discharged from the upper part of the fixing unit 30 to the paper discharge port 42. The paper discharge port 42 is a horizontal slit that opens in the housing of the printer 800. The paper discharge roller 43 is disposed inside the paper discharge port 42, and discharges the sheet SH3 that has moved along the guide plate 41 on its side surface while rotating, from the paper discharge port 42 to the outside of the housing. The inline sensor 400 irradiates light on the surface of the sheet SH3 conveyed along the guide plate 41 from the fixing unit 30 and directly reads the image from the light reflected by the surface. The inline sensor 400 further determines the color coordinate value or density of each pixel from the image and notifies the control unit 60 of it.

The internal structure of the inline sensor 400 is the same as that of the image reading unit 200 shown in FIG. In particular, the light emitting element is located outside the outer wall of the housing, that is, outside the optical system, the light detection unit, and the electronic circuit for image processing. The optical system, the light detection unit, and the electronic circuit are all separated from the space above the light emitting element by the outer wall of the housing.
[Electronic control system of image forming apparatus]
FIG. 10 is a block diagram illustrating a configuration of an electronic control system of the printer 800. Referring to FIG. 10, in this electronic control system, in addition to the image forming unit 70, that is, the feeding unit 10, the image forming unit 20, the fixing unit 30, and the paper discharge unit 40, the operation unit 50 and the control unit 60 are connected by a bus. 90 are communicably connected to each other.

-Operation part-
Referring to FIG. 10, in the operation unit 50, the operation panel 51 displays a GUI screen such as an operation screen and an input screen for various parameters on the display, and identifies the position of the push button or touch panel operated by the user. Tell 60. In the operation unit 50, the external I / F 52 also includes a memory interface such as a USB port or a memory card slot, or a network interface connected to an external network by wire or wirelessly, through which an external device such as a USB memory or HDD is externally connected. The image data to be printed is directly taken in from the storage device, or the image data to be printed is received from these electronic devices by communicating with other electronic devices connected to the network.

-Control unit-
The control unit 60 is an electronic circuit mounted on a single board installed in the printer 800. Referring to FIG. 10, in the control unit 60, the CPU 61 controls the other elements 50 and 70 connected to the bus 90 according to the firmware. The RAM 62 provides a work area for the CPU 61 to execute the firmware to the CPU 61 and stores image data to be printed received by the operation unit 50. The ROM 63 includes a non-writable semiconductor memory device and a rewritable semiconductor memory device such as an EEPROM or an HDD. The former stores firmware, and the latter provides the CPU 61 with a storage area for environment variables and the like.

  When the CPU 61 executes various types of firmware, the control unit 60 first controls the operation of other elements in the printer 800 based on information from the operation unit 50. Specifically, the control unit 60 displays an operation screen on the operation unit 50 to accept an operation by the user. In response to this operation, the control unit 60 determines an operation mode such as an operation mode, a standby mode, and a sleep mode, notifies the operation mode to other elements with a drive signal, and performs processing according to the operation mode. Let the element execute.

[Role of inline sensor]
The inline sensor 400 is used by the control unit 60 for automatic image quality stabilization control. Specifically, the control unit 60 first causes the in-line sensor 400 to measure the color coordinate value or the image density of each pixel constituting the toner image from the sheet processed by the fixing unit 30, and uses these measurement values. Notify me. Even if the toner image is formed according to predetermined image data stored in the control unit 60 in advance for image quality correction, such as a color patch, the operation unit 50 accepts the toner image from the outside in response to a normal print request. It may be formed according to image data to be printed. Next, the control unit 60 compares the measured value notified from the inline sensor 400 with the color coordinate value or image density of each pixel indicated by the image data used for forming the toner image to be measured, From these differences, image quality disturbances such as image gradation shifts, unevenness, or color coordinate shifts are detected. The controller 60 further performs a correction process so that the detected image quality disturbance is suppressed in the newly formed toner image after the detection. This correction processing includes control of image forming conditions for the image forming unit 70 in addition to image processing such as γ correction. For example, the control unit 60 instructs the image forming unit 20 to correct the development bias, that is, to correct the bias voltage applied to the photosensitive drum 25 during development, or to correct the exposure amount to the photosensitive drum 25. The fixing unit 30 is instructed to correct the surface temperature of the fixing roller 31. By these correction processes, the density of the toner image newly formed on the sheet or the balance of the toner density between the four colors is appropriately corrected, and the detected image quality disturbance is suppressed.

As described above, the inline sensor 400 plays an important role in automatically stabilizing the image quality by using the measured value for feedback control of the image quality of the toner image by the control unit 60.
[Advantages of Embodiment 2]
As described above, the image forming apparatus 800 according to the second embodiment of the present invention uses the inline sensor 400 for the automatic stabilization control of the image quality of the toner image. Inside the inline sensor 400, the light emitting element 261 is disposed outside the outer wall 213 of the housing 210, as in the image reading unit 200 according to the first embodiment. Therefore, since the air flow HTF heated by the heat of the light emitting element 261 rises and diffuses into the heat dissipation space HPT, the optical system 270 and the light detection unit 280 are particularly connected from the flow HTF to the internal space SPC of the housing 210. An excessive amount of heat is not transmitted to and from. Thereby, since the heat of the light emitting element 261 is not trapped in the internal space SPC, there is no risk that the temperature of either the optical system 270 or the light detection unit 280 excessively increases. In this way, even if the inline sensor 400 is installed so as to irradiate light to a sheet that passes directly below, the inline sensor 400 can prevent deterioration in image quality and image processing accuracy due to heat of the light emitting element 261. As a result, the image forming apparatus 800 can maintain high image quality stability of the toner image.

  In addition, since the reliability of the inline sensor 400 is maintained high regardless of the posture at the time of installation, the inline sensor 400 has few restrictions on the relative positional relationship with the measurement target sheet. Therefore, the inline sensor 400 has high design flexibility when mounted on the image forming apparatus 800.

  The present invention relates to a heat dissipation structure for a light source of an image reading apparatus, and arranges the light source outside the outer wall of the housing as described above. Thus, the present invention is clearly industrially applicable.

200 Image reading unit 210 Housing 211 Bottom surface of housing 212 Projecting portion on bottom surface of housing 213 Exterior wall of housing 214 Upper surface of housing 215 Opening on bottom surface of housing 216 Projecting portion on top surface of housing 217 Overhanging portion of bottom surface 218 Slit of outer wall of casing 219 Opening of outer wall of casing SPC Internal space of casing HPT Heat radiation space HTF Flow of air warmed by heat of light emitting element 260 Illuminating section 261 Light emitting element 262 Light guide member 263 Holding member 264 Holding member recess 265 Holding member recess slit 266 Holding member longitudinal end surface 267 Light guiding member longitudinal end surface 268 Light guiding member side surface 269 Contact glass 270 Optical system 271 First mirror 272 First 2 mirrors 273 3rd mirror 274 4th mirror 275 5th mirror 276 Imaging lens array 2 0 photodetection unit 281 signal output terminal

Claims (9)

An image reading device that irradiates a sheet positioned below, detects light reflected by the sheet, and reads an image of the sheet from the light,
A light emitting element;
A light guide member that has a long shape, guides the light of the light emitting element that has entered from the end face in the longitudinal direction, and emits the light toward the sheet positioned below from the side surface that extends in the longitudinal direction;
An optical system including at least one mirror that reflects light reflected by the sheet, and at least one lens that focuses the light;
A light detection unit for detecting light focused through the optical system;
A housing for holding the light guide member, the optical system, and the light detection unit;
With
The light emitting element is disposed outside the outer wall of the housing,
The mirror has an elongated plate shape, and the longitudinal direction of the light guide member and each other are arranged in parallel.
The outer wall of the housing holds both ends of the mirror in the longitudinal direction, and separates the optical system and the photodetector from a heat dissipation space extending above the light emitting element,
The image reading apparatus , wherein the heat radiation space raises air heated by heat of the light emitting element to be diffused by convection .   The image reading apparatus according to claim 1, wherein the position of the light emitting element is outside the outer wall of the housing in the longitudinal direction of the light guide member. The bottom surface of the housing includes an opening for taking light reflected by the sheet into the housing,
The at least one mirror is
A first mirror that first reflects light that has passed through the opening;
A second mirror that reflects the light after the first mirror;
Including
The distance in the up-down direction from the said opening part to the said 2nd mirror is shorter than the distance in the up-down direction from the said opening part to the said 1st mirror, The Claim 1 or Claim 2 characterized by the above-mentioned. Image reading device. Of the at least one mirror, the first mirror that reflects the light that has passed through the opening has a length of the reflecting surface in the longitudinal direction of the light guide member that is longer than the length of the light guide member in the longitudinal direction. The image reading apparatus according to claim 1, wherein the image reading apparatus is short. The image reading apparatus according to any one of claims 1 to 4, further comprising a cover member that covers the housing and the light emitting element from above. 6. The image reading apparatus according to claim 5, wherein a vent hole is formed in a portion of the cover member facing a space above the light emitting element. The image reading apparatus according to claim 1, further comprising a heat insulating connecting member that covers an optical path from the light emitting element to an end face in a longitudinal direction of the light guide member. The outer wall of the housing includes an opening for securing an optical path from the light emitting element to the end face in the longitudinal direction of the light guide member,
The image reading apparatus according to claim 7, wherein the connecting member has a structure that closes the opening. An image forming unit that forms an image on a sheet based on image data;
The image reading apparatus according to any one of claims 1 to 8, wherein a sheet processed by the image forming unit is arranged to pass below.
A control unit that controls image forming conditions for the image forming unit based on a comparison between the image data and data representing an image read by the image reading device;
An image forming apparatus.

Images