JP4659698B2 - Image reading apparatus and image forming apparatus having the same - Google Patents

Description

  The present invention relates to an image reading apparatus that scans an original with light and reads an image with a photoelectric conversion element, and an image forming apparatus such as a copying machine, a printer, and a facsimile equipped with the image reading apparatus.

  In an image forming apparatus such as a copying machine or a laser beam printer that employs an electrophotographic system, an image reading device that scans an original placed on a contact glass by optical scanning is provided. Based on the obtained image data, an image is formed on a recording material such as paper by an image forming means. Here, the image forming unit includes various process devices such as a photosensitive drum, a developing device, a transfer device, and a fixing device.

  By the way, the image reading apparatus includes a point light source that emits light toward the document surface, a light guide for guiding the light emitted from the point light source to the document surface, and the light emitted from the point light source. A reflection plate for guiding light that does not pass through the light guide to the document surface, and a photoelectric conversion element that reads the reflected light reflected on the document surface are included. An LED or the like is used as a point light source of this type of document reading apparatus.

  Thus, since a point light source such as an LED has a smaller light amount than a rod-like light source such as a fluorescent lamp, it has a drawback that it is likely to cause a shortage of light amount unless sufficient consideration is given to the irradiation direction.

Therefore, an LED which is a point light source is used by using an LED array formed by arranging a plurality of LEDs on a substantially straight line and a lens for condensing a light beam emitted from the LED array in a direction perpendicular to the LED arrangement direction. A proposal has been made to effectively use the amount of light (see Patent Document 1).
JP 2004-157213 A

  However, in the configuration described in Patent Document 1, as shown in FIG. 6, the LED light source 122 is disposed on the optical axis O of the lens 123 that is a light guide, and light is emitted from the LED light source 122. Since the direction coincides with the optical axis direction of the lens 123, indirect light L ′ that does not pass through the lens 123 out of the angle range of (α + β + γ) shown in the figure from the LED light source 122 is shown on both sides of the lens 123. It exists in the angle range of β and γ. Of the indirect light L ′, light in the angle range of β is reflected by the reflecting plate 124 and irradiated toward the image reading position X to be used for image reading. However, the indirect light L in the angle range of γ is used. Since 'is not effectively used for reading an image, all of the light amount of the LED light source 122 is not effectively used, and there is a problem that the image reading performance is deteriorated. The light in the angle range of α that is emitted from the LED light source 122 and passes through the lens 123 is referred to as direct light L. In FIG. 6, 121 is a contact glass, and 125 is a mirror.

  The present invention has been made in view of the above problems. An object of the present invention is to provide an image reading apparatus capable of effectively using the light quantity of a point light source to obtain high reading performance and an image forming apparatus including the image reading apparatus. It is to provide.

  In order to achieve the above object, a first aspect of the present invention is a point light source that emits light toward a document surface, a light guide for guiding light emitted from the point light source to the document surface, and the point. An image reading apparatus comprising: a reflector for guiding light that does not pass through the light guide from the light source to the document surface; and a photoelectric conversion element that reads reflected light reflected by the document surface. The light emitting direction from the point light source is arranged so as to be inclined toward the reflector side with respect to the central optical axis of the light guide.

  According to a second aspect of the present invention, in the first aspect of the present invention, the point light source is arranged on a central optical axis of the light guide.

  According to a third aspect of the present invention, in the first aspect of the invention, the point light source is disposed at a position offset from the central optical axis of the light guide to the reflector side.

  According to a fourth aspect of the present invention, there is provided a point light source that emits light toward the document surface, a light guide for guiding the light emitted from the point light source to the document surface, and the light emitted from the point light source. An image reading apparatus having a reflector for guiding light that does not pass through the light guide to the document surface and a photoelectric conversion element that reads the reflected light reflected on the document surface, wherein the point light source is the center of the light guide It is arranged at a position that is parallel to the optical axis and offset toward the reflecting plate.

  The invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein the light guide is a cylinder type.

  According to a sixth aspect of the present invention, there is provided the image reading device according to any one of the first to fifth aspects, and an image forming unit that forms an image on a recording material based on image data read by the image reading device. The image forming apparatus is configured to include the image forming apparatus.

  According to the first to fourth aspects of the invention, most of the light emitted from the point light source that does not pass through the light guide (indirect light) is directed to the reflecting plate and reflected by the reflecting plate to the document surface. Therefore, it is possible to ensure high reading performance by effectively using almost all of the light amount of the point light source. Further, by appropriately setting the inclination angle or offset amount of the point light source, the ratio of the amount of direct light that passes through the light guide and indirect light that does not pass through the light guide can be about 7: 3, It is possible to prevent the shadow of the stepped portion from being generated when the cut and pasted document is read.

  According to the invention described in claim 5, by making the light guide into a cylinder type, the light from the point light source can be condensed in the sub-scanning direction, and the assembly of the light guide can be improved. it can.

  According to the sixth aspect of the present invention, a high quality image can be stably obtained based on image data read with high accuracy by the image reading apparatus.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

[Image forming apparatus]
FIG. 1 is a front sectional view of a color copying machine as an embodiment of an image forming apparatus according to the present invention.

  The color copying machine shown in FIG. 1 includes an image reading device 20 according to the present invention at the top of a main body 100, and a magenta image forming unit 1M and a cyan image forming unit constituting image forming means at the inner central portion of the main body 100. 1C, a yellow image forming unit 1Y and a black image forming unit 1BK are arranged in a line at regular intervals.

  The image forming units 1M, 1C, 1Y, and 1BK, which are image forming units, have drum type electrophotographic photosensitive members (hereinafter referred to as “photosensitive drums”) 2a, 2b, 2c, and 2d as image carriers. is set up. Around the photosensitive drums 2a to 2d, there are primary chargers 3a, 3b, 3c, 3d, developing devices 4a, 4b, 4c, 4d, transfer rollers 5a, 5b, 5c, 5d as primary transfer means, and drums. Cleaning devices 6a, 6b, 6c and 6d are arranged, respectively.

  The photosensitive drums 2a to 2d are drum-shaped amorphous silicon (α-Si) photosensitive members, and are rotated at a predetermined process speed in a direction indicated by an arrow (counterclockwise in FIG. 1) by a driving device (not shown). The

  The primary chargers 3a to 3d uniformly charge the surfaces of the photosensitive drums 2a to 2d to a predetermined potential by a charging bias applied from a charging bias power source (not shown).

  Further, the developing devices 4a to 4d contain magenta (M) toner, cyan (C) toner, yellow (Y) toner, and black (BK) toner, respectively, and are formed on the photosensitive drums 2a to 2d. The toner of each color is attached to each electrostatic latent image to develop each electrostatic latent image as a toner image of each color (visualization), and the toner is consumed and the developing devices 4a to 4d When a toner replenishment signal is issued because the remaining amount of toner is less than a certain value, toner of each color is replenished from the toner replenishing devices 7a, 7b, 7c and 7d to the developing devices 4a to 4d. The toner replenishing devices 7 a to 7 d are configured as cartridges that can be attached to and detached from the copying machine main body 100.

  The transfer rollers 5a to 5d as primary transfer means are arranged so as to be in contact with the photosensitive drums 2a to 2d via an endless intermediate transfer belt 8 at each primary transfer portion (primary transfer nip portion). ing. Here, the intermediate transfer belt 8 constitutes a second image carrier, and is stretched between the secondary transfer counter roller 9 and the tension roller 10 and travels to the upper surface side of each of the photosensitive drums 2a to 2d. Arranged to be possible. The secondary transfer counter roller 9 is disposed so as to be in contact with the secondary transfer roller 11 via the intermediate transfer belt 8 in the secondary transfer portion (secondary transfer nip portion). As the material of the intermediate transfer belt 8, for example, a dielectric resin such as polycarbonate, polyethylene terephthalate (PET), polyvinylidene fluoride (PVdF), or the like is selected. Although not shown, a belt cleaning device for removing residual toner remaining on the surface of the intermediate transfer belt 8 is installed outside the intermediate transfer belt 8 and in the vicinity of the tension roller 10. Yes.

  On the other hand, a laser scanner unit 40 is arranged below each image forming unit 1M, 1C, 1Y, 1BK inside the copying machine main body 100, and a paper feed cassette 50 is detachably installed at the bottom of the main body 100 below the image forming units 1M, 1C, 1Y, 1BK. In this paper feed cassette 50, a plurality of recording materials P are stacked and stored. In the vicinity of the paper feed cassette 50, a pickup roller 13 for feeding the recording material P from the paper feed cassette 50 to the transport path 12 one by one is provided.

  Further, the conveyance path 12 arranged in the vertical direction on one side of the copying machine main body 100 extends to a paper discharge tray 14 provided on the upper surface of the main body 100, and in the middle thereof, a pair of paper feed rollers 15. A registration roller pair 16, a fixing device 17 having a fixing roller 17a and a pressure roller 17b, and a paper discharge roller pair 18 are provided.

  Next, an image forming operation by the color copying machine having the above configuration will be described.

  When an image formation start signal is issued, the photosensitive drums 2a to 2d are driven to rotate in the direction of the arrow in FIG. 1 at a predetermined process speed in each of the image forming units 1M, 1C, 1Y, and 1BK, and these photosensitive drums 2a to 2d. Are uniformly charged positively by the primary chargers 3a to 3d. The laser scanner unit 40 emits a laser beam modulated by a color image signal for each color of the original image read by the image reading device 20 from a laser output unit 41, and the laser beam is emitted from a lens 42 and a plurality of mirrors. 43 and the lens 44, and are projected onto the surfaces of the photosensitive drums 2a to 2d, and electrostatic latent images corresponding to the color image signals of the respective colors are formed on the photosensitive drums 2a to 2d, respectively.

  First, magenta toner is adhered to the electrostatic latent image formed on the photosensitive drum 2a of the magenta image forming unit 1M by the developing device 4a to which a developing bias having the same polarity as the charged polarity of the photosensitive drum 2a is applied. The electrostatic latent image is visualized as a magenta toner image. The magenta toner image is rotationally driven in the direction indicated by the arrow in the primary transfer portion between the photosensitive drum 2a and the transfer roller 5a by the action of the transfer roller 5a to which a primary transfer bias having a polarity opposite to that of the toner is applied. Primary transfer is performed on the intermediate transfer belt 8.

  The intermediate transfer belt 8 on which the magenta toner image has been primarily transferred as described above moves to the next cyan image forming unit 1C. In the cyan image forming unit 1C as well, the cyan toner image formed on the photosensitive drum 2b is transferred onto the magenta toner image on the intermediate transfer belt 8 at the primary transfer portion in the same manner as described above.

  Similarly, the yellow and black toner images formed on the photosensitive drums 2c and 2d of the yellow and black image forming units 1Y and 1BK are respectively formed on the magenta and cyan toner images superimposed and transferred on the intermediate transfer belt 8. In each primary transfer portion, the images are sequentially overlapped, and a full-color toner image is formed on the intermediate transfer belt 8. The transfer residual toner that is not transferred onto the intermediate transfer belt 8 and remains on the photosensitive drums 2a to 2d is removed by the drum cleaning devices 6a to 6d, and is transferred by a waste toner transfer means (not shown) to be transferred to each toner. The toner is collected as waste toner in a toner collecting container formed integrally with the supply devices 7a to 7d.

  On the other hand, one sheet of recording material P is fed from the sheet feeding cassette 50 to the transport path 12 by the pickup roller 13 and the pair of sheet feeding rollers 15, and this recording material P is the leading edge of the full color toner image on the intermediate transfer belt 8. Is conveyed to the secondary transfer portion by the registration roller pair 16 in accordance with the timing of reaching the secondary transfer portion between the secondary transfer counter roller 9 and the secondary transfer roller 11.

  Then, a full color toner image is transferred to the intermediate transfer belt by the action of the transfer electric field formed by the secondary transfer roller 11 to which the secondary transfer bias having the opposite polarity to the toner is applied to the recording material P conveyed to the secondary transfer unit. The secondary transfer is performed on the recording material P from 8 at the same time.

  Thus, the recording material P onto which the full-color toner image has been transferred is subjected to charge removal processing and electrostatically separated from the intermediate transfer belt 8, and then conveyed to the fixing device 17. In the fixing device 17, a full-color toner image is heated and pressed at the fixing nip portion between the fixing roller 17 a and the pressure roller 17 b to be thermally fixed on the surface of the recording material P, and the toner image is fixed. A series of image forming operations is completed when the recording material P is discharged onto the discharge tray 14 by the discharge roller pair 18. The secondary transfer residual toner that is not transferred onto the recording material P but remains on the intermediate transfer belt 8 is removed by a belt cleaning device (not shown), and is transported by a waste toner transport means (not shown) to be shown. It is collected as waste toner in a collection container.

[Image reading device]
Next, details of the configuration of the image reading apparatus 20 according to the present invention will be described with reference to the accompanying drawings.

<Embodiment 1>
FIG. 2 is a front sectional view of the image reading apparatus according to the present invention, and FIG. 3 is a front sectional view showing the configuration of the illumination system of the image reading apparatus (part A enlarged detail view of FIG. 2).

  As shown in FIG. 2, the image reading apparatus 20 according to the present invention includes a transparent contact glass 21 on which a document (not shown) is placed, and a document surface of the document (not shown) placed on the contact glass 21. An LED 22 light source that is a point light source that emits light toward the image reading position X, a cylinder-type light guide 23 for guiding the light emitted from the LED light source 22 to the image reading position X, and an LED light source A concave curved reflector 24 for condensing indirect light L ′ that does not pass through the light guide 24 out of the light guide 24 out of the light guide 22 and the reflected light L reflected at the image read position X. A plurality of mirrors 25, 26, and 27 that further reflect “" and change the direction thereof, a lens 28 that collects the reflected light L ″, and a photoelectric conversion element that reads the reflected light L ″ collected by the lens 28. (CCD) 29 included In is configured. Incidentally, it referred to as the direct light of the light L emitted from the LED light source 22 passes through the light guide body 23 with respect to the indirect light L '.

  Thus, in the present embodiment, as shown in FIG. 3, the LED light source 22 is disposed on the central optical axis O of the light guide 23, and the light emission direction from the LED light source 22 is guided. It is characterized in that it is inclined with respect to the central optical axis O of the body 23 so as to be inclined by the angle θ shown in the figure on the reflecting plate 24 side. Here, the central optical axis O of the light guide 23 is defined as a center line that goes to the image reading position X through the center of the light guide 23 in the width direction.

  In the present embodiment, as described above, the LED light source 22 is disposed so that the light emission direction is inclined by the angle θ toward the reflecting plate 24 with respect to the central optical axis O. Of the emitted light, most of the indirect light L ′ that does not pass through the light guide 23 is directed to the reflecting plate 24, reflected by the reflecting plate 24, and irradiated to the image reading position X to be effectively used for image reading. Is done. For this reason, almost all of the light amount of the LED light source 22 can be used effectively, and as a result, high reading performance can be ensured in the image reading apparatus 20.

  By the way, it is desirable that the light condensing state at the image reading position X is as uniform as possible and has high illuminance with a width of about 3 to 4 mm in consideration of variations in mechanical dimensions.

  Further, among the light emitted from the LED light source 22, the ratio of the light amount of the direct light L that passes through the light guide 23 and the indirect light L ′ that does not pass through the light guide 23 is preferably 5: 5, but at least 7: It is necessary to set to about 3.

  Thus, in the present embodiment, the direct light L that passes through the light guide 23 and the indirect light L ′ that does not pass through the light guide 23 are set by setting the inclination angle θ of the LED light source 22 to about 10 °. The ratio of the amount of light can be set to about 7: 3, which can prevent the occurrence of a shadow at the step portion when the cut and pasted document is read.

  In the present embodiment, since the cylindrical light guide 23 is used, the light emitted from the LED light source 22 can be condensed in the sub-scanning direction, and the assembly of the light guide 23 is improved. be able to.

<Embodiment 2>
Next, a second embodiment of the present invention will be described with reference to FIG.

  FIG. 4 is a front sectional view showing the configuration of the illumination system of the image reading apparatus according to the present embodiment. In this figure, the same elements as those shown in FIG. The re-explanation about them is omitted.

  The present embodiment is characterized in that the LED light source 22 is arranged at a position offset by e as shown in the figure on the reflection plate 24 side in parallel to the central optical axis O of the light guide 22.

  Thus, in the present embodiment, as described above, the LED light source 22 is arranged at a position offset by e as shown in the figure on the reflecting plate 24 side in parallel to the central optical axis O of the light guide 22. Of the light emitted from the light source 22, most of the indirect light L ′ that does not pass through the light guide 23 is directed to the reflecting plate 24, reflected by the reflecting plate 24, and irradiated to the image reading position X to read an image. It is used effectively. For this reason, almost all of the light amount of the LED light source 22 can be used effectively, and as a result, high reading performance can be ensured in the image reading apparatus 20. In this embodiment, by setting the offset amount e of the LED light source 22 to about 1.5 mm, the direct light L that passes through the light guide 23 and the indirect light L ′ that does not pass through the light guide 23 are obtained. The ratio of the amount of light can be set to about 7: 3, which can prevent the occurrence of a shadow at the step portion when the cut and pasted document is read.

<Embodiment 3>
Next, Embodiment 3 of the present invention will be described with reference to FIG.

  FIG. 5 is a front sectional view showing the configuration of the illumination system of the image reading apparatus according to the present embodiment. In FIG. 5, the same elements as those shown in FIGS. 3 and 4 are denoted by the same reference numerals. In the following, a repetitive description thereof will be omitted.

  The present embodiment is a combination of the first embodiment and the second embodiment, in which the LED light source 22 is offset from the central optical axis O of the light guide 23 to the reflector 24 side by e ′ shown in the figure. The light emission direction from the LED light source 22 is inclined at an angle θ ′ shown in the figure on the reflection plate 24 side with respect to the central optical axis O of the light guide 23. .

  Thus, also in the present embodiment, most of the indirect light L ′ that does not pass through the light guide 23 out of the light emitted from the LED light source 22 is directed to the reflecting plate 24 and reflected by the reflecting plate 24 to generate an image. Since it is irradiated to the reading position X and is effectively used for reading an image, almost all of the light amount of the LED light source 22 can be used effectively, and the same as in the first and second embodiments. An effect is obtained.

  Although the present invention has been described with respect to a mode in which the present invention is applied particularly to a color copying machine, the present invention can be applied not only to a color copying machine but also to a monochrome copying machine and other arbitrary image forming apparatuses.

1 is a front sectional view of an image forming apparatus (color copying machine) according to the present invention. 1 is a front sectional view of an image reading apparatus according to the present invention. FIG. 3 is a front sectional view of the illumination system of the image reading apparatus according to Embodiment 1 of the present invention (enlarged detailed view of a portion A in FIG. 2). It is a front sectional view of the illumination system of the image reading apparatus according to the second embodiment of the present invention. It is a front sectional view of the illumination system of the image reading apparatus according to Embodiment 3 of the present invention. It is a front sectional view of an illumination system of a conventional image reading apparatus.

Explanation of symbols

1M, 1C, 1Y, 1BK Image forming units 2a, 2b, 2c, 2d Photosensitive drum (image carrier)
3a, 3b, 3c, 3d Primary charger 4a, 4b, 4c, 4d Developing device 5a, 5b, 5c, 5d Transfer roller (transfer means)
6a, 6b, 6c, 6d Drum cleaning device 7a, 7b, 7c, 7d Toner supply device 8 Intermediate transfer belt (image carrier)
9 Secondary transfer counter roller 10 Tension roller 11 Secondary transfer roller (transfer means)
DESCRIPTION OF SYMBOLS 12 Conveyance path 13 Pickup roller 14 Paper discharge tray 15 Paper feed roller pair 16 Registration roller pair 17 Fixing device 17a Fixing roller 17b Pressure roller 18 Paper discharge roller pair 20 Image reading device 21 Contact glass 22 LED light source (point light source)
23 Light guide 24 Reflector 25-27 Mirror 28 Lens 29 Photoelectric conversion element (CCD)
40 Laser scanner unit 50 Paper feed cassette 100 Copier body e, e ′ Offset amount of LED light source L Direct light L ′ Indirect light L ”Reflected light O Center optical axis of light guide P Recording material X Image reading position θ, θ '' LED light source tilt angle

Claims (6)

A point light source that emits light toward the document surface, a light guide for guiding the light emitted from the point light source to the document surface, and light that does not pass through the light source from the point light source In an image reading apparatus having a reflector for guiding light to a document surface and a photoelectric conversion element that reads reflected light reflected on the document surface,
An image reading apparatus, wherein the point light source is disposed so as to be inclined such that a light emission direction from the point light source is inclined toward the reflector with respect to a central optical axis of the light guide.   The image reading apparatus according to claim 1, wherein the point light source is disposed on a central optical axis of the light guide.   The image reading apparatus according to claim 1, wherein the point light source is disposed at a position offset from a central optical axis of the light guide toward the reflecting plate. A point light source that emits light toward the document surface, a light guide for guiding the light emitted from the point light source to the document surface, and light that does not pass through the light source from the point light source In an image reading apparatus having a reflector for guiding light to a document surface and a photoelectric conversion element that reads reflected light reflected on the document surface,
An image reading apparatus, wherein the point light source is disposed at a position offset toward the reflecting plate side in parallel to a central optical axis of the light guide.   The image reading apparatus according to claim 1, wherein the light guide is a cylinder type.   6. An image forming apparatus comprising: the image reading apparatus according to claim 1; and image forming means for forming an image on a recording material based on image data read by the image reading apparatus. apparatus.

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