JP2012058691A - Image position detector and image formation apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image position detector capable of accurately detecting a position of a toner image for image position detection at a low cost, and to provide an image formation device using the same.SOLUTION: The apparatus includes: light emitting means 41 for radiating light on a toner image for image position detection that is formed on a medium to be detected; a first aperture 44 for condensing a light flux emitted by the light emitting means 41 at a predetermined aperture diameter; light receiving means 42 for receiving specular reflection from the medium to be detected on which the toner image for image position detection is formed; and a second aperture 45 for condensing a light flux of the specular reflection received by the light receiving means 42 from the medium to be detected on which the toner image for image position detection is formed, at a predetermined aperture diameter; the aperture diameter of the first aperture 44 being set to be larger than that of the second aperture 45.

Description

  The present invention relates to an image position detection apparatus and an image forming apparatus using the same.

  Conventionally, as the image forming apparatus, for example, a register formed on an intermediate transfer belt or the like for correcting the image forming position of each color of yellow (Y), magenta (M), cyan (C), and black (K). There is a configuration in which a misregistration detection pattern is detected by a registration error detection sensor and an image forming position is corrected according to a detection result of the registration error detection sensor.

  In such an image forming apparatus, as a technique related to an image position detection apparatus that detects a registration shift detection pattern formed on an intermediate transfer belt or the like, for example, Japanese Patent Application Laid-Open No. 2002-055572 and Japanese Patent Application Laid-Open No. 2005-300918 are disclosed. Or what was disclosed by Unexamined-Japanese-Patent No. 09-043144, 2005-091252, etc. has already been proposed.

  The image detection apparatus according to Japanese Patent Application Laid-Open No. 2002-055572 includes a light source unit, an illumination unit including an irradiation lens that irradiates a recording member on which an image is formed with a light beam from the light source unit, and the recording member. In an image detection apparatus for detecting an image on the recording member based on a signal obtained by the light receiving means, the recording member is provided with an imaging means including an imaging lens for forming an image on the light receiving means surface. When a specular reflection surface is used, the diaphragm is configured to have a stop at or near a position conjugate with the light emitting point of the light source means.

In addition, the image forming apparatus according to Japanese Patent Application Laid-Open No. 2005-300918 includes at least an image carrier, a charging unit that charges the image carrier to a predetermined polarity, and an exposure unit that forms an electrostatic latent image on the image carrier. A process device including a developing unit that visualizes the electrostatic latent image formed on the image carrier, a detection pattern generating unit that controls the process device to form a predetermined detection pattern on a detection medium, In an image forming apparatus having a detection element in at least a specular reflection direction and having an optical detection means for detecting the detection pattern,
The ratio B / A between the reflected light amount A when only the detection medium is detected and the reflected light amount B when a predetermined correction pattern is detected is set to a predetermined value.

  Furthermore, the density sensor according to the above-mentioned Japanese Patent Application Laid-Open No. 09-043144 includes a light-emitting element, a first light-receiving element that measures the light amount of the light-emitting element, a second light-receiving element that receives reflected light from the measurement object, In the density sensor including a holder that supports the first light receiving element and the second light receiving element, a light flux regulating member is provided in the irradiation opening of the light emitting element.

In addition, the optical sensor according to the above Japanese Patent Application Laid-Open No. 2005-091252 includes at least one light emitting means
In an optical sensor having at least one light receiving means for receiving reflected light when the incident light emitted from the light emitting means is reflected by an irradiation object,
At least one of the light emitting means and the light receiving means is surface-mounted on a circuit board,
A hole forming member that forms a light passage hole smaller than the cross-sectional area of the optical path is provided on the optical path between the at least one means and the irradiation object.

JP 2002-055572 A JP-A-2005-300918 JP 09-043144 A Japanese Patent Laying-Open No. 2005-091252

  By the way, the problem to be solved by the present invention is to provide an image position detection device capable of accurately detecting the position of a toner image for image position detection at low cost and an image forming apparatus using the image position detection device. .

That is, the invention described in claim 1 is a light emitting means for irradiating light to a toner image for image position detection formed on a detected medium;
A first opening for narrowing a light beam emitted from the light emitting means with a predetermined opening diameter;
A light receiving means for receiving regular reflection light from a detection medium on which the toner image for image position detection is formed;
The light receiving means includes a second opening for narrowing a light beam for receiving specularly reflected light from the detected medium on which the toner image for image position detection is formed, with a predetermined opening diameter;
An image position detecting apparatus, wherein an opening diameter of the first opening is set larger than an opening diameter of the second opening.

  The invention described in claim 2 is characterized in that the opening diameter of the first opening is set to be 2.15 times larger than the opening diameter of the second opening. It is an image position detection apparatus as described in above.

  Furthermore, in the invention described in claim 3, the distance between the peak position in the output value of the regular reflection component of the light receiving element and the peak position in the output value of the diffuse reflection component is set to be larger than about 1.0 mm. The image position detection device according to claim 1, wherein the image position detection device is an image position detection device.

  According to a fourth aspect of the present invention, the image position detection device is arranged so that the output value of the regular reflection component reaches a peak when the distance between the light receiving element and the detected medium is 8 mm. The image position detecting device according to claim 1, wherein the image position detecting device is an image position detecting device.

  Further, in the invention described in claim 5, the image position detecting device is displaced ± 1 mm in a direction in which the image receiving device is in contact with or separated from the detected medium from the peak position in the output value of the regular reflection component of the light receiving element. 5. The image position detection device according to claim 1, wherein an output fluctuation of the light receiving element in a case is set to be within 10% of a peak value. 6.

According to a sixth aspect of the present invention, there is provided an image forming means for forming a toner image for detecting an image position on a detected medium using black and at least one color toner;
Image position detecting means for detecting the position of a toner image for image position detection formed on the detected medium by the image forming means,
6. An image forming apparatus according to claim 1, wherein the image position detecting means is the one described in any one of claims 1 to 5.

  According to the first aspect of the present invention, it is possible to accurately detect the position of the image position detecting toner image at a lower cost than in the case where the present configuration is not provided.

  According to the second aspect of the present invention, the position detection accuracy of the image position detection toner image can be improved as compared with the case where the present configuration is not provided.

  Further, according to the third aspect of the present invention, the position detection accuracy of the image position detection toner image can be improved as compared with the case where the present configuration is not provided.

  Further, according to the invention described in claim 4, it is possible to suppress the output value from fluctuating with respect to the mounting error of the image position detection device, as compared with the case where this configuration is not provided.

  Furthermore, according to the fifth aspect of the present invention, the position detection accuracy of the image position detection toner image can be improved as compared with the case where the present configuration is not provided.

  According to the sixth aspect of the present invention, the position detection accuracy of the image position detection toner image can be improved and the image quality can be improved as compared with the case where the present configuration is not provided. .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially broken cross-sectional configuration diagram illustrating an image detection device according to a first embodiment of the present invention. 1 is a configuration diagram showing a tandem type full-color printer as an image forming apparatus to which an image detection apparatus according to Embodiment 1 of the present invention is applied. FIG. 1 is a configuration diagram showing an image forming unit of a tandem type full-color printer as an image forming apparatus according to Embodiment 1 of the present invention; FIG. FIG. 6 is a schematic diagram illustrating a toner patch and a registration error detection pattern. It is a block diagram which shows the attachment state of a toner detection sensor. 1 is a block diagram illustrating an image detection apparatus according to Embodiment 1 of the present invention. FIG. 6 is a waveform diagram showing an output signal of a toner detection sensor. It is a graph which shows the detection accuracy error of the toner detection sensor made as an experiment. FIG. 6 is a schematic diagram illustrating reflected light from a toner image. It is a graph which shows the relationship between the light emission / emission window ratio of the toner detection sensor made as a prototype, and a detection accuracy error. It is a graph which shows the relationship between the focal distance of the toner detection sensor made as an experiment, and sensor output ratio. It is a graph which shows the relationship between the focal distance of the toner detection sensor made as an experiment, and a sensor output. It is a graph which shows the relationship between the focal distance of the toner detection sensor made as an experiment, and a sensor output. It is a graph which shows the relationship between the regular reflection / diffuse reflection peak difference of a prototype toner detection sensor, and a detection accuracy error.

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

Embodiment 1
FIG. 2 is a block diagram showing a tandem type color printer as an image forming apparatus to which the image position detecting apparatus according to the first embodiment of the present invention is applied. FIG. 3 is a configuration diagram showing an image forming unit of the color printer.

  As shown in FIG. 2, the image forming apparatus is configured to display full color or image data according to image data output from a personal computer, an image reading device (not shown), or the like, or image data sent via a telephone line or a LAN. A monochrome image is output.

  As shown in FIG. 2, the image forming apparatus main body 1 has shading correction, if necessary, for image data sent from a personal computer (PC) 2 or an image reading device (not shown). An image processing unit 3 for performing predetermined image processing such as positional deviation correction, lightness / color space conversion, gamma correction, frame erasing, color / moving editing, and the like is disposed, and control for controlling the operation of the entire color printer. Part 4 is arranged.

  The image data that has been subjected to predetermined image processing by the image processing apparatus 3 as described above is processed by the image processing unit 3 in the same manner as yellow (Y), magenta (M), cyan (C), and black (K). And output as a full-color image or a monochrome image by the image output unit 5 provided inside the color printer main body 1 as described below.

  As shown in FIG. 2, the image forming apparatus main body 1 includes four image forming units (image forming means) 6Y of yellow (Y), magenta (M), cyan (C), and black (K). 6M, 6C, and 6K are horizontal with respect to the horizontal direction so that the yellow (Y) image forming unit 6Y of the first color is relatively high and the black (K) image forming unit 7K is relatively low. They are arranged in parallel at a predetermined interval in a state where they are inclined by a predetermined angle (for example, about 10 degrees). Note that the inclination angles of the image forming units 6Y, 6M, 6C, and 6K are not limited to about 10 degrees, and it is a matter of course that they may be larger or smaller.

  In this way, the four image forming units 6Y, 6M, 6C, and 6K of yellow (Y), magenta (M), cyan (C), and black (K) are arranged in an inclined state by a predetermined angle. As a result, the distance between the image forming units 6Y, 6M, 6C, and 6K can be set shorter than in the case where these four image forming units 6Y, 6M, 6C, and 6K are horizontally arranged, and the color printer. It is possible to reduce the size by reducing the width along the arrangement direction of the main bodies 1.

  These four image forming units 6Y, 6M, 6C, and 6K are basically configured similarly except for the color of the image to be formed. As shown in FIG. 2 and FIG. The photosensitive drum 8 as an image holding member that is rotationally driven at a predetermined speed along the direction of the arrow A, a charging roll 9 for primary charging that charges the surface of the photosensitive drum 8, and the photosensitive member. An image exposure device 7 including an LED print head that exposes an image corresponding to a predetermined color on the surface of the drum 8 to form an electrostatic latent image, and an electrostatic latent image formed on the photosensitive drum 8. The developing device 10 is configured to develop with the corresponding color toner, and the cleaning device 11 is configured to clean the surface of the photosensitive drum 8.

  As the photosensitive drum 8, for example, a drum having a diameter of about 30 mm and having a surface coated with a photosensitive layer made of an organic photoconductor (OPC) or the like is used. It is rotationally driven at a predetermined speed along the A direction.

  Further, as the charging roll 9, for example, a roll-shaped charger in which the surface of the core metal is covered with a conductive layer made of synthetic resin or synthetic rubber and having an adjusted electric resistance is used. Is applied with a predetermined charging bias.

  As shown in FIG. 2, the image exposure device 7 is individually arranged for each of the four image forming units 6Y, 6M, 6C, and 6K, and the image provided in each of the image forming units 6Y, 6M, 6C, and 6K. The exposure apparatus 7 includes an LED light emitting element array in which LED light emitting elements are linearly arranged along the axial direction of the photosensitive drum 8 at a predetermined pitch (for example, 600 dpi to 1200 dpi), and the LED light emitting element array. What is provided with the rod lens array which images the light radiate | emitted from each LED light emitting element on the photosensitive drum 8 in spot shape is used. Further, as shown in FIGS. 2 and 3, the image exposure device 7 is arranged so as to scan and expose an image on the photosensitive drum 8 from below.

  When the image exposure device 7 is composed of an LED light emitting element array, it is desirable because the image exposure device 7 can be significantly reduced in size. However, the laser beam may be deflected and scanned along the axial direction of each photosensitive drum 8. In this case, for example, one image exposure apparatus is arranged for four image forming units 6Y, 6M, 6C, and 6K.

  From the image processing unit 3, as described above, the image forming units 6Y, 6M, 6C, and 6K for each color of yellow (Y), magenta (M), cyan (C), and black (K) are individually provided. The image data corresponding to each color is sequentially output to the image exposure devices 7Y, 7M, 7C, and 7K, and the light beams emitted from these image exposure devices 7Y, 7M, 7C, and 7K according to the image data correspond to the image data. The surfaces of the photosensitive drums 8Y, 8M, 8C, and 8K are scanned and exposed, and electrostatic latent images corresponding to the image data are formed on the surfaces of the photosensitive drums 8Y, 8M, 8C, and 8K. The electrostatic latent images formed on the photosensitive drums 8Y, 8M, 8C, and 8K are yellow (Y), magenta (M), cyan (C), and black by the developing devices 10Y, 10M, 10C, and 10K, respectively. It is developed as a toner image of each color of (K).

  Yellow (Y), magenta (M), cyan (C), and black (K) sequentially formed on the photosensitive drums 8Y, 8M, 8C, and 8K of the image forming units 6Y, 6M, 6C, and 6K. The toner images of the respective colors are transferred to four primary transfer rolls 13Y on an endless belt-shaped intermediate transfer belt 12 serving as a detection medium disposed in an inclined state over the image forming units 6Y, 6M, 6C, and 6K. Multiplexed primary transfer is sequentially performed by 13M, 13C, and 13K.

  In this embodiment, the intermediate transfer belt 12 is used as the medium to be detected. However, as the medium to be detected, it is needless to say that a conveyance belt that conveys the recording medium may be used. .

  The intermediate transfer belt 12 is an endless belt-like member stretched by a plurality of rolls, and the lower side running region of the belt-like member is relatively low on the downstream side along the running direction and relatively upstream on the upstream side. The image forming units 6Y, 6M, 6C, and 6K are disposed so as to be inclined at an angle equal to the inclination angle of the horizontal direction.

  That is, as shown in FIG. 2, the intermediate transfer belt 12 is wound around with a predetermined tension between a drive roll 15 having a function as a back support roll of the secondary transfer portion and a driven roll 14. It is circulated and driven at a predetermined speed along the direction of arrow B by a drive roll 15 that is rotated by a drive motor that is excellent in constant speed (not shown). As the intermediate transfer belt 12, for example, a belt formed of an endless belt with a synthetic resin film such as flexible polyimide or polyamideimide is used. The intermediate transfer belt 12 is disposed so as to be in contact with the photosensitive drums 8Y, 8M, 8C, and 8K of the image forming units 6Y, 6M, 6C, and 6K in the lower side running region.

  Further, as shown in FIG. 2, the intermediate transfer belt 12 is arranged at the lower end portion of the traveling area of the intermediate transfer belt 12 and records the toner images that have been primary-transferred on the intermediate transfer belt 12 in a multiple manner. A secondary transfer roll 17 as a secondary transfer unit that performs secondary transfer collectively on the medium 16 is disposed so as to contact the surface of the intermediate transfer belt 12 stretched by the drive roll 15.

  The yellow (Y), magenta (M), cyan (C), and black (K) toner images transferred onto the intermediate transfer belt 12 in a multiple manner are transferred to the drive roll 15 as shown in FIG. The secondary transfer roll 17 that is in contact with the transfer belt 12 collectively transfers the secondary transfer roll 17 onto the recording paper 16 as a recording medium. It is conveyed to the fixing device 18 positioned above. The secondary transfer roll 17 is in pressure contact with the side of the drive roll 15 via the intermediate transfer belt 12, and a toner image of each color is transferred onto the recording paper 16 conveyed from the lower side to the upper side in the vertical direction. It is configured to perform secondary transfer all at once.

  As the secondary transfer roll 17, for example, an elastic body layer made of a conductive elastic body such as a synthetic rubber material to which a conductive agent is added is formed in a predetermined thickness on the outer periphery of a metal core made of metal such as stainless steel. A coated one is used.

  The recording paper 16 on which the toner images of the respective colors are transferred is subjected to a fixing process with heat and pressure by a heating roll 19 and a pressure belt (or pressure roll) 20 of a fixing device 18 as a fixing unit. The paper is discharged by a discharge roll 21 on a discharge tray 22 provided at the upper end of the printer body 1 with the image surface facing down.

  As shown in FIG. 2, the recording paper 16 having a predetermined size and material from the paper feed tray 23 arranged at the bottom of the printer main body 1 is unified by the paper feed roll 24 and the paper separation roll 25. The paper is fed in a state of being separated one by one, and is once transported to the registration roll 26 and stopped. The recording paper 16 supplied from the paper feed tray 23 is sent out to the secondary transfer position of the intermediate transfer belt 12 by a registration roll 26 that rotates at a predetermined timing. As the recording paper 16, in addition to plain paper, a thick paper such as a coated paper whose front surface or both surfaces are coated, an OHP sheet, and the like can be supplied. Will also output photographic images.

  At that time, for example, the recording paper 16 is fed and transported with reference to a central portion in a direction intersecting the paper feeding direction, and a toner image is transferred and fixed from the intermediate transfer belt 12. The paper is discharged onto the discharge tray 22 with the central portion in the direction intersecting the paper feeding direction as a reference. However, the present invention is not necessarily limited to this. For example, the recording paper 16 may be configured to be fed and conveyed with reference to one end portion in a direction crossing the feeding direction.

  As shown in FIGS. 2 and 3, residual toner is removed from the surface of the photosensitive drum 8 after the primary transfer process of the toner image by the cleaning device 11 to prepare for the next image forming process. Further, as shown in FIG. 2, residual toner and the like are removed from the surface of the intermediate transfer belt 12 after the secondary transfer process of the toner image by a belt cleaning device 27 provided in the vicinity of the downstream side of the drive roll 15. In preparation for the next image forming step.

  By the way, the image forming apparatus has one color or a color corresponding to the image to be formed in each of the image forming units 6Y, 6M, 6C, and 6K of yellow (Y), magenta (M), cyan (C), and black (K). The toner images of the four colors are formed, and the toner images of the respective colors are primarily transferred in a state where they are superimposed on the intermediate transfer belt 12, thereby forming an image of a desired color. For this reason, in this image forming apparatus, if the toner images of the respective colors formed by the image forming units 6Y, 6M, 6C, and 6K have image density unevenness or image positional deviation, the color tone of the color image may fluctuate. Color misregistration or the like may occur, and image quality may be degraded.

  Therefore, in the image forming apparatus, a toner cartridge (not shown) that supplies toner to the developing device is replaced every time an image is formed on a recording sheet for a predetermined number of sheets when the apparatus is turned on, or when returning from a pause operation. At a predetermined timing such as when the image is formed, the yellow (Y), magenta (M), cyan (C), and black (K) image forming units 6Y, 6M, 6C, and 6K are placed on the intermediate transfer belt 12. By forming a toner image for image density detection and a toner image for image position detection, and detecting both the toner image for image density detection and the toner image for image position detection by a regular reflection type toner detection means. The control unit 4 is configured to control the image density and image position in each of the image forming units 6Y, 6M, 6C, and 6K.

  The image density detection toner image and the image position detection toner image are formed using, for example, black and at least one color toner. In this embodiment, yellow (Y), magenta ( M), cyan (C), and black (K) toners are used to form the toner.

  As the toner image for image density detection, for example, as shown in FIG. 4, at least one kind such as a halftone density with an image density Cin of about 30% or 70%, and a maximum density of 100% as necessary. Toner patches 31Y, 31M, 31C, and 31K of each color of yellow (Y), magenta (M), cyan (C), and black (K) formed in a flat rectangular shape such as a square are used. Further, as the toner image for detecting the image position, for example, as shown in FIG. 4, the image density Cin has a high density of about 80 to 100% and is along the sub-scanning direction that is the axial direction of the photosensitive drum 8. A registration error detection pattern 32Y for each color of yellow (Y), magenta (M), cyan (C), and black (K), which is formed in a relatively thin straight line having a predetermined width and length. 32M, 32C, 32K are used.

  As shown in FIG. 4, the toner image for image position detection is relatively thin so as to have a predetermined width and length along the sub-scanning direction that is the axial direction of the photosensitive drum 8. The linear first toner image 33a and a predetermined angle (for example, 45) from the one end of the first toner image 33a in the sub-scanning direction along the main scanning direction that is the circumferential direction of the photosensitive drum 8. Yellow (Y), magenta (M), cyan (C), and black, which are formed of a relatively thin linear second toner image 33b so as to have a predetermined width and length in a state inclined by (degree). The registration deviation detection patterns 33Y, 33M, 33C, and 33K for each color of (K) may be used. When these registration error detection patterns 33Y, 33M, 33C, and 33K are used, it is possible to detect the positions of both the image in the sub-scanning direction and the main scanning direction, and the image formation position is determined in the sub-scanning direction and It is possible to control both in the main scanning direction, and the image quality can be further improved.

  The toner patches 31Y, 31M, 31C, and 31K and the registration error detection patterns 32Y, 32M, 32C, and 32K are, for example, in a direction that intersects with the moving direction of the intermediate transfer belt 12 as shown in FIG. It is formed at one end portion in the direction along the surface of the transfer belt 12, but is not limited to this, and the toner patches 31Y, 31M, 31C, 31K and the registration error detection patterns 32Y, 32M, 32C, 32K The formation position only needs to correspond to the position of the toner image detection means 40, and is a direction intersecting the moving direction of the intermediate transfer belt 12 and in the center along the surface of the intermediate transfer belt 12 or the other. It may be set at the end, or a plurality of such as a central portion and at least one end in the direction along the surface of the intermediate transfer belt 12 may be provided.

  The toner image detection means 40 for detecting the toner patches 31Y, 31M, 31C, 31K and the registration error detection patterns 32Y, 32M, 32C, 32K, for example, as shown in FIG. The intermediate transfer belt 12 is arranged on the downstream side in the moving direction of the intermediate transfer belt 12 and on the surface of the intermediate transfer belt 12 held by the drive roll 15 or in the vicinity thereof.

  FIG. 1 is a block diagram showing toner image detection means of an image position detection apparatus according to Embodiment 1 of the present invention.

  As described above, the toner image detection sensor 40 serving as the toner image detection unit is a dual-use sensor that detects both the toner patches 31Y, 31M, 31C, and 31K and the registration error detection patterns 32Y, 32M, 32C, and 32K. As shown in FIG. 1, it is composed of a regular reflection type sensor including an LED 41 that emits light having a wavelength in the infrared region or red region as a light emitting element and a phototransistor 42 as a light receiving element. ing. The LED 41 and the phototransistor 42 are set so that the incident angle θ1 and the reflection angle θ2 are both 10 degrees with respect to the perpendicular H set at the detection position on the surface of the intermediate transfer belt 12 as the detected medium. Yes. However, it goes without saying that the incident angle θ1 and the reflection angle θ2 of the LED 41 and the phototransistor 42 are not limited to 10 degrees.

  Further, as shown in FIG. 1, the housing 43 of the toner image detection sensor 40 has a first opening 44 for irradiating the surface of the intermediate transfer belt 12 as a detected medium with a light beam emitted from the LED 41; A second opening 45 is provided for receiving reflected light from the surface of the intermediate transfer belt 12 as a detected medium. In this embodiment, for example, the opening (aperture) diameter of the first opening 44 is set to φ2.8 mm, and the opening (aperture) diameter of the second opening 45 is set to φ1.3 mm. The opening diameter of one opening 44 is set to be twice or more larger than the opening diameter of the second opening 45.

  As shown in FIG. 1, the first opening 44 is configured to irradiate the surface of the intermediate transfer belt 12 with a light beam emitted from the LED 41 with a predetermined opening diameter. Thus, the opening diameter of the emission end of the first opening 44 is set to φ2.8 mm.

  On the other hand, as shown in FIG. 1, the second opening 45 determines in advance the light flux of the reflected light from the registration deviation detection patterns 32Y, 32M, 32C, 32K, etc. formed on the surface of the intermediate transfer belt 12. The aperture diameter is narrowed down to be incident on the light receiving element 42. As described above, the aperture diameter of the incident end of the second aperture 45 is set to φ1.3 mm, for example. Further, the front end portion of the light receiving element 42 is approximately 4.2 mm from the end surface of the housing 43 of the toner image detection sensor 40 in order to effectively restrict the light flux of the reflected light from the surface of the intermediate transfer belt 12 by the second opening 45. It is arranged so as to be located on the far side.

  Further, as shown in FIG. 1, the toner image detection sensor 40 has a first irradiation region 46 set in a circular shape by blocking the light beam emitted from the light emitting portion of the LED 41 by the first opening 44. Is irradiated with a predetermined brightness. On the other hand, in the toner image detection sensor 40, the reflected light from the surface of the intermediate transfer belt 12 is blocked by the second opening 45 in the first irradiation region 46 irradiated with the light beam emitted from the light emitting portion of the LED 41. Thus, only the light reflected from the second irradiation region 47 set in a circular shape is incident on the phototransistor 42 and is received by the phototransistor 42. In FIG. 5, reference numeral 48 indicates an attachment hole for attaching the toner image detection sensor 40.

  At that time, as shown in FIGS. 1 and 5, the toner image detection sensor 40 is connected to the surface of the intermediate transfer belt 12 as a medium to be detected from first and second openings 44 and 45 which are ends of the housing 43. (Hereinafter referred to as “focal length” for the sake of convenience) up to 8 mm. Further, as shown in FIG. 1, the toner image detection sensor 40 is set so that the distance from the end of the housing 43 to the position where the center lines of the LED 41 and the light receiving element 42 intersect each other is 11.5 mm. Yes.

  FIG. 6 is a block diagram showing a configuration of a detection circuit of the image position detection apparatus.

  In FIG. 6, reference numeral 41 denotes an LED, and reference numeral 42 denotes a light receiving element. A signal output from the light receiving element 42 is converted into a voltage value by a current-voltage converter 51, and then an amplifier (op-amp). 52 is amplified at a predetermined amplification factor (gain).

  As shown in FIG. 7, the signal amplified by the amplifier 52 is compared with a predetermined threshold value by a comparator 53 as a comparison unit, and the signal amplified by the amplifier 52 is predetermined by the comparator 53. For example, an “H” level output signal is output while the threshold value is below the threshold value. The timing discriminating circuit 54 discriminates the timing when the signal amplified by the amplifier 52 falls below a predetermined threshold, that is, when the output of the comparator 53 changes from the “L” level to the “H” level. In the counter 55, the count value of the reference pulse output from the reference pulse generator (not shown) at the timing when the signal amplified by the amplifier 52 becomes equal to or lower than a predetermined threshold value and the amplifier 52 amplified A reference pulse count value output from a reference pulse generator (not shown) at a timing when the signal exceeds a predetermined threshold, that is, when the output of the comparator 53 changes from the “H” level to the “L” level, Is counted.

  As shown in FIG. 6, the count value from the counter 55 is input to a microcomputer 56 of a color printer provided in the control unit 4, and in this microcomputer 56, for example, by an amplifier 52 output from the counter 55. By calculating the median value of the count value when the amplified signal is equal to or lower than a predetermined threshold and the count value when the signal amplified by the amplifier 52 exceeds the predetermined threshold, The positions of the registration error detection patterns 32Y, 32M, 32C, and 32K are detected. Then, for example, the microcomputer 56 uses the position of the black (K) color registration error detection pattern 32K as a reference, and the registration error detection pattern 33Y for each color of yellow (Y), magenta (M), and cyan (C). , 33M, 33C so that the distance in the sub-scanning direction is equal to a predetermined value or an error from a predetermined value is within a predetermined range. An operation of correcting the image position by calculating the correction value of the image position in each of the magenta (M) and cyan (C) image forming units 6Y, 6M, and 6C is executed. Similarly, the microcomputer 56 uses the yellow (Y), magenta (M), cyan (C), and black (K) color toner patches 31Y, 31M, 31C, and 31K based on the detected densities of the yellow (Y), magenta (M), cyan (C), and black (K) colors. The operation of correcting the image density by calculating the correction value of the image density in each of the image forming units 6Y, 6M, 6C, and 6K of Y), magenta (M), cyan (C), and black (K) is executed.

  By the way, when the position of the registration error detection patterns 32Y, 32M, 32C, and 32K is detected using the conventional image density sensor as the toner image detection sensor 40 as it is, as shown in FIG. The distance (Y-M) between the registration error detection pattern 32Y and the black registration error detection pattern 32K, and the distance between the magenta registration error detection pattern 32M and the black registration error detection pattern 32K ( M−K), and the detection error when the distance (C−K) between the cyan color registration error detection pattern 32C and the black color registration error detection pattern 32K is detected. As shown as the work (TR1), it was found that a detection error of about −100.0 μm to −120.0 μm occurred.

  The present inventor has earnestly studied the cause of a large detection error of about −100.0 μm to −120.0 μm as shown in FIG. 8 when the conventional image density sensor is used as a registration deviation detection sensor as it is. As a result, the registration error detection patterns 32Y, 32M, 32C, 32K and the distribution of the regular reflection light and the diffuse reflection light on the surface of the intermediate transfer belt 12 on which the registration error detection patterns 32Y, 32M, 32C, 32K are formed. Clarified that it depends on.

  As described above, the toner image detection sensor 40 detects both the toner patch and the registration error detection pattern. When the toner image detection sensor 40 detects the toner patch, the density of the toner patch is detected. The magnitude of the output of the toner image detection sensor 40 depending on the size is important.

  On the other hand, when the registration error detection patterns 32Y, 32M, 32C, and 32K are detected by the toner image detection sensor 40, the output of the toner image detection sensor 40 depends on the density of the toner image. Position information of the output of the toner image detection sensor 40 depending on the positions of the registration error detection patterns 32Y, 32M, 32C, and 32K is important.

  In the area where the toner image on the surface of the intermediate transfer belt 12 is formed, when the toner image is made of black toner, the light beam emitted from the LED 41 is irradiated with the black toner as shown in FIG. Is absorbed almost completely, and is reflected by the black toner image and received by the phototransistor 42 of the toner image detection sensor 40.

  On the other hand, when the registration error detection pattern is made of yellow, magenta, or cyan color toner, the luminous flux emitted from the LED 41 is a small amount of the irradiated light as shown in FIG. 9B. Is diffused and reflected, and the diffusely reflected light from the color toner is received by the phototransistor 42 of the toner image detection sensor 40, and the registration error detection pattern is formed of yellow, magenta, and cyan color toners. The regular reflection light from the registration error detection pattern has a relatively narrow and large peak value corresponding to the position of the pattern, whereas the diffuse reflection light from the registration error detection pattern The width is relatively wide corresponding to the position, and a relatively small peak value is shown.

  Therefore, in order to improve the detection accuracy of the position of the registration error detection pattern composed of black, yellow, magenta, and cyan color toners using the regular reflection type toner image detection sensor 40, regular reflection by the light receiving element is performed. It is important how to reduce the influence of diffuse reflected light from the registration deviation detection pattern without reducing the amount of received light as much as possible.

  Therefore, the inventor of the present invention uses the regular reflection type toner image detection sensor 40 shown in FIG. 1 to reduce the influence of diffuse reflection light from the registration deviation detection patterns 32Y, 32M, 32C, and 32K. A configuration in which the opening diameter of the opening 45 is set small is adopted. However, in the regular reflection type toner image detection sensor 40 used as a conventional image density sensor, the opening diameter of the opening 45 of the light receiving element 42 and the opening diameter of the opening 44 of the light emitting element 41 are considered from the viewpoint of balance of the light amount. Therefore, if the opening diameter of the light emitting element 41 is reduced as the opening diameter of the light receiving element 42 is reduced, the registration error detection patterns 32Y and 32M are used unless the light quantity of the light emitting element 41 is increased. , 32C, and 32K are reduced, and the amount of received regular reflection light incident on the light receiving element is also reduced.

  Therefore, the toner image detection sensor 40 according to this embodiment employs an asymmetric optical system, and the opening diameter of the first opening 44 on the light emitting side is set to the opening diameter of the second opening 45 on the light receiving side. It is set larger than.

  Next, the present inventor changed the opening diameter of the first opening 44 and the opening diameter of the second opening 45 on the light receiving side as shown in FIG. An experiment was conducted to confirm how the detection errors at the positions of the registration error detection patterns 32Y, 32M, 32C, and 32K change.

  FIG. 8A shows the toner image detection sensor 40 in which the opening diameter of the first opening 44 and the opening diameter of the second opening 45 are 1.35 mm, 2.40 mm, 1.00 mm, and 1.50 mm, respectively. FIG. 6 is a graph showing a result of confirming how a detection error of a pattern for detecting misregistration changes by experimentally producing sensors (TR1 to TR4) set to 1.30 mm and 2.80 mm, respectively.

  As a result, as shown in the prototype (TR2) of FIG. 8 (a), the aperture diameter of the light receiving element 42 is changed to 1.35 mm, which is about ½ smaller than the conventional 2.40 mm. As a result, it has been found that the detection error can be reduced to about −80.0 μm for any of the registration error detection patterns of yellow, magenta, and cyan.

  Similarly, as shown in the prototype (TR3) of FIG. 8A, by changing the aperture diameter of the light receiving element to 1.00 mm and changing the aperture diameter of the light emitting element to 1.50 mm, yellow, It can be seen that the detection error can be greatly reduced to about −40.0 μm for both the magenta and cyan registration error detection patterns.

  This is presumably because the influence of diffusely reflected light could be greatly reduced by reducing the aperture diameter of the light receiving element 42 to 1.00 mm.

  However, when the aperture diameter of the light receiving element 42 is reduced to 1.00 mm, the yellow, magenta, and cyan colors have a significant improvement effect, but the detection error of the magenta color registration error detection pattern is −40. It exceeds 0 μm, and it can be seen that the target detection error cannot be suppressed to −40.0 μm or less.

  The reason for this is that if the aperture diameter of the light receiving element 42 is reduced to 1.00 mm, the robustness indicating stability against uncertain element fluctuations such as disturbances and mounting errors is reduced, and the output fluctuations are increased. It is considered that this appears as a decrease in the detection error of the magenta color registration error detection pattern.

  Therefore, in this embodiment, in order to significantly reduce the influence of diffusely reflected light, the aperture diameter of the light receiving element 42 is secured to some extent in order to ensure robustness while reducing the aperture diameter of the light receiving element 42. In addition, even if the opening diameter of the light emitting element 41 is set to be somewhat large in order to stabilize the output value of the light receiving element 42, the influence of the diffuse reflected light is greatly reduced by reducing the opening diameter of the light receiving element 42. From the above-mentioned knowledge that the light emitting element 41 can be obtained, the opening diameter of the opening 44 on the light emitting element 41 side is set to be larger than the opening diameter of the opening 45 on the light receiving element 42 side. Is set to be larger than the opening diameter of the opening 45 on the light receiving element 42 side by 2.15 times or more. When the opening diameter of the opening 44 on the light emitting element 41 side is used as a reference, the opening diameter of the opening 45 on the light receiving element 42 side is about 1 / 2.15 than the opening diameter of the opening 44 on the light emitting element 41 side. It is configured to be set small.

  Next, the inventor calculates the ratio of the opening diameter of the opening 44 on the light emitting element 41 side and the opening diameter of the opening 45 on the light receiving element 42 side in the toner image detection sensor 40 shown in FIG. An experiment was conducted to confirm how the approximate value of the color for black of the registration error detection pattern changes when various changes are made as shown in FIG.

  FIG. 10A is a graph showing the results of the experiment.

  As is apparent from FIG. 10A, detection is performed by setting the ratio of the opening diameter of the opening 44 on the light emitting element 41 side and the opening diameter of the opening 45 on the light receiving element 42 side to 2.15 or more. It was found that the error value can be suppressed to 40.0 μm or less.

  Furthermore, in order to confirm the robustness of the toner image detection sensor 40, the present inventor, as shown in FIG. 11B, the opening diameter of the first opening 44 and the opening diameter of the second opening 45 When the sensor is made differently, and the sensor is moved in a minus direction from a predetermined focal length, that is, a direction closer to the detected medium, and a plus direction, that is, a direction away from the detected medium, the toner An experiment was conducted to check how much the output value of the regular reflection component of the image detection sensor 40 changes when the peak value is 100%.

  FIG. 11A is a graph showing the results of the experiment.

  As is clear from the graph shown in FIG. 11A, when any prototype deviates from the focal length in the positive and negative directions, the sensor output voltage tends to decrease from the peak position. If the sensor output voltage deviates by 1.0 mm or more in the direction, the sensor output voltage deviates by 10% or more from the peak value. However, only one prototype was determined to be impossible. Good results were obtained.

  As is clear from FIG. 11A, when the aperture diameter of the light receiving element 42 is reduced to 1.00 mm or 1.15 mm, the output value of the regular reflection component of the toner image detection sensor 40 changes by about 10%. It turns out that it is undesirable.

  Further, as apparent from FIG. 11A, the opening diameter of the light receiving element 42 is 1.30 mm, the opening diameter of the light emitting element 41 is 2.40 mm, and the opening diameter of the light receiving element is 1.30 mm. The sensor with the aperture of 2.80 mm has a small variation in the output value of the regular reflection component with respect to the variation in the focal length, and good results have been obtained.

  Next, the inventor changes the value of the focal length of the toner image detection sensor 40 to about 4.2 mm to 10.2 mm by changing the installation angles of the light emitting element and the light receiving element of the toner image detection sensor 40, respectively. An experiment was conducted to confirm how the output value profiles of the regular reflection component and the diffuse reflection component of the toner image detection sensor 40 change when the toner image detection sensor 40 is changed.

  FIG. 12 is a graph showing an output value profile of the regular reflection component of the toner image detection sensor 40.

  As apparent from FIG. 12, the output value profile of the regular reflection component of the toner image detection sensor 40 is roughly divided into two groups, and the first group has a range of about 5.4 mm to 6.0 mm. The second group is a group having a peak at about 8.0 mm. It can also be seen that even in the first group, the focal length shifts as the ratio between the opening of the light emitting element and the opening of the light receiving element increases.

  On the other hand, the second group shows substantially the same characteristics, but the peak of the output value of the specular reflection component increases slightly as the ratio of the opening of the light emitting element to the opening of the light receiving element increases. It seems to show.

  On the other hand, FIG. 13 is a graph showing an output value profile of the diffuse reflection component of the toner image detection sensor 40.

  As apparent from FIG. 13, the output value profile of the diffuse reflection component of the toner image detection sensor 40 is significantly different from the output value profile of the regular reflection component. In almost all cases, the focal length is about 5.4 mm to 6 mm. There is a peak at a position of .9 mm, and the peak value tends to gradually decrease as the focal length increases.

  As is apparent from the results shown in FIGS. 13 and 14, in order to improve the detection accuracy of the positions of the yellow, magenta, cyan, and black registration error detection patterns by the toner image detection sensor 40, the regular reflection component The peak value of the output value profile is set as high as possible, the peak value of the output value profile of the diffuse reflection component is set as low as possible, and the peak of the output value profile of the regular reflection component and the diffuse reflection are set. It is desirable to set a large distance between the peak of the component output value profile and to set a large difference between the two output values.

  Therefore, based on the results shown in FIGS. 12 and 13, the detection error of the toner image detection sensor 40 is determined using the distance between the peak of the output value profile of the regular reflection component and the peak of the output value profile of the diffuse reflection component as a parameter. As shown in FIG. 14, when the change is confirmed, the distance between the peak of the output value profile of the regular reflection component and the peak of the output value profile of the diffuse reflection component is increased by about 1.0 mm or more. It was found that if set, the detection error of the registration error detection pattern can be set to 40 μm or less. In this embodiment, the peak position of the output value profile of the regular reflection component is located at a focal length of 8.0 mm, the peak position of the output value profile of the diffuse reflection component is located at a focal length of 6.0 mm, The distance between the peak of the output value profile of the regular reflection component and the peak of the output value profile of the diffuse reflection component is set to 2.0 mm.

  With the above configuration, the image forming apparatus according to this embodiment can accurately detect the position of the image position detection toner image at low cost as follows.

  That is, in this image forming apparatus, as shown in FIG. 4, the image of each color of yellow (Y), magenta (M), cyan (C), and black (K) at a predetermined timing at the time of non-image formation. By the forming units 6Y, 6M, 6C, and 6K, the toner patches 31Y, 31M, 31C, and 31K, and the registration error detection patterns with yellow (Y), magenta (M), cyan (C), and black (K) toners. Both 32Y, 32M, 32C, and 32K are formed on the intermediate transfer belt 12.

  The yellow (Y), magenta (M), cyan (C), and black (K) toner patches 31Y, 31M, 31C, and 31K and the registration error detection patterns 32Y and 32M formed on the intermediate transfer belt 12 are described. 32C and 32K are detected by a toner image detection sensor 40 disposed on the downstream side in the moving direction of the intermediate transfer belt 12 of the black (K) image forming unit 6K, as shown in FIGS. Is done.

  As shown in FIG. 1, the toner image detection sensor 40 irradiates the surface of the intermediate transfer belt 12 with a light beam emitted from the LED 41, and a toner patch formed on the surface of the intermediate transfer belt 12 and the intermediate transfer belt 12. Reflected light from 31Y, 31M, 31C, and 31K and the registration error detection patterns 32Y, 32M, 32C, and 32K is received by the phototransistor 42 as a light receiving element.

  The reflected light from the toner patches 31Y, 31M, 31C, 31K and the registration error detection patterns 32Y, 32M, 32C, 32K received by the phototransistor 42 is subjected to photoelectric conversion by the phototransistor 42 as shown in FIG. Is converted into a current value corresponding to the amount of received light, and then converted into a voltage value by the current-voltage converter 51 and amplified by the amplifier 52 with a predetermined gain.

  The signal amplified by the amplifier 52 is compared with a predetermined threshold value by a comparator 53 as a comparison means. From the comparator 53, for example, the signal amplified by the amplifier 52 becomes equal to or lower than a predetermined threshold value. During this period, an “H” level output signal is output.

  In this embodiment, as shown in FIG. 1, in the toner image detection sensor 40, the opening diameter of the opening 44 on the light emitting element 41 side is set larger than the opening diameter of the opening 45 on the light receiving element 42 side. Moreover, the ratio of the opening diameter of the opening 44 on the light emitting element 41 side to the opening diameter of the opening 45 on the light receiving element 42 side is set to be 2.15 or more.

  Therefore, in the toner image detection sensor 40, as shown in FIG. 10A, the registration of each color of yellow (Y), magenta (M), and cyan (C) is based on the black registration displacement detection pattern 32K. The detection error when detecting the misalignment detection patterns 32Y, 32M, and 32C can be suppressed to 40 μm or less, and the registration misalignment detection patterns 32Y, 32M, 32C, and 32K can be accurately detected. Can do.

  Further, in this embodiment, as shown in FIG. 14, the distance between the peak of the output value profile of the regular reflection component and the peak of the output value profile of the diffuse reflection component is set to be larger by about 1.0 mm or more. Therefore, from this point as well, the detection error of the registration error detection pattern can be set to 40 μm or less.

  32Y, 32M, 32C, 32K: registration displacement detection pattern, 40: toner image detection sensor, 41: light emitting element, 42: light receiving element, 44: first opening, 45: second opening.

Claims (6)

A light emitting means for irradiating light to a toner image for image position detection formed on the detected medium;
A first opening for narrowing a light beam emitted from the light emitting means with a predetermined opening diameter;
A light receiving means for receiving regular reflection light from a detection medium on which the toner image for image position detection is formed;
The light receiving means includes a second opening for narrowing a light beam for receiving specularly reflected light from the detected medium on which the toner image for image position detection is formed, with a predetermined opening diameter;
An image position detecting apparatus, wherein an opening diameter of the first opening is set larger than an opening diameter of the second opening.   The image position detection apparatus according to claim 1, wherein an opening diameter of the first opening is set to be 2.15 times larger than an opening diameter of the second opening.   The distance between the peak position in the output value of the regular reflection component of the light receiving element and the peak position in the output value of the diffuse reflection component is set to be larger by about 1.0 mm or more. Image position detection device.   4. The image position detection device according to claim 1, wherein the image position detection device is arranged so that an output value of a regular reflection component reaches a peak when a distance between the light receiving element and the detected medium is 8 mm. The image position detection apparatus described in 1.   In the image position detection device, the output fluctuation of the light receiving element when the output value of the regular reflection component of the light receiving element is displaced ± 1 mm from the peak position toward and away from the detected medium has a peak value. The image position detection device according to claim 1, wherein the image position detection device is set to be within 10%. Image forming means for forming a toner image for image position detection on a detection medium using black and at least one color toner;
Image position detecting means for detecting the position of a toner image for image position detection formed on the detected medium by the image forming means,
6. An image forming apparatus according to claim 1, wherein the image position detecting means is the one described in any one of claims 1 to 5.

Images