JP2007140133A - Color image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately correct the misalignment of a plurality of color images. <P>SOLUTION: A pair of electrodes 36a and 36b are disposed so that the pair of the electrodes 36a and 36b can hold an optical path formed between a light emitting means 22 and a light receiving means 23 in a space between an endless carrier 12 and a pattern detection means 14. Predetermined voltage is applied between the electrodes 36a and 36b so as to generate an electric field. Before toner suspended in the space between the endless carrier 12 and the pattern detection means 14 adheres to the light emitting means 22 and the light receiving means 23, the suspended toner is forced to adhere to either of the pair of electrodes. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrophotographic color image forming apparatus having a plurality of photoconductors, and more particularly to a technique for preventing toner contamination of a detecting means such as a sensor for detecting a positional deviation of toner images of respective colors.

  2. Description of the Related Art Conventionally, in an image forming apparatus employing an electrophotographic method, a photosensitive member as an image carrier is charged by a charger, and a light is applied to the charged photosensitive member according to image information to form a latent image. At the same time, the latent image is developed by a developing device, and the developed toner image is transferred to a transfer material such as a sheet material to form an image. That is, in the electrophotographic system, an image forming process such as a charging process, an exposure process, a development process, and a transfer process is performed.

  In addition, with the colorization of the image, a plurality of image forming stations (each of the above processes) corresponding to cyan, magenta, yellow, and preferably black are provided, and a cyan image and a magenta image are provided. A tandem method in which each color image of a yellow image, preferably a black image, is formed on each image carrier, and a full color image is formed by transferring each color image on a sheet material at the transfer position of each image carrier. A color image forming apparatus has also been proposed. Such a tandem color image forming apparatus has an image forming unit for each color, which is advantageous in terms of speeding up the image forming process.

  However, the tandem color image forming apparatus has a problem in how well the registration (registration) of images formed by different image forming units is performed. This is because a shift in image formation position of four-color transfer images (toner images) transferred to a transfer material such as a sheet material finally appears as a positional shift or a change in color tone.

  FIG. 16 is a diagram illustrating the types of misalignment of the transferred image. In FIGS. 16A to 16E, a line segment indicated by a solid line indicates a state of a transfer image to be transferred at a predetermined transfer position, and a line segment indicated by a dotted line is transferred in a misaligned state. The state of the transferred image is shown.

  As shown in FIG. 16A, the transfer image is displaced in the transfer material movement direction (the direction of arrow A in the drawing) (hereinafter referred to as “sub-scanning position displacement”), and FIG. ) As shown in FIG. 16C, and a displacement in the oblique direction as shown in FIG. 16C (hereinafter referred to as “main scanning position deviation”). Hereinafter, it is referred to as “skew error”), a magnification error shift as shown in FIG. 16D, a bending error shift as shown in FIG. In actuality, a combination of two or more types of positional deviations among these five types appears.

  By the way, in the case of the sub-scanning position shift as shown in FIG. 16A, the main causes of the above-described positional shifts are the mounting shift of each image forming station and the scanning optical system, and the lenses and mirrors in the scanning optical system. The main scanning position shift as shown in FIG. 16B is the same as the sub-scanning position shift as shown in FIG. 16B. In the case of the skew error shown in FIG. The deviation of the rotation axis of the photosensitive member and the deviation of the mounting angle of the scanning optical system. In the case of the deviation due to the magnification error as shown in FIG. 16D, each scanning optical system to the photosensitive member of the image forming station. This is due to the deviation of the scanning line length due to the error in the optical path length, and the deviation due to the bending error as shown in FIG. 16 (e) is due to the assembly deviation of the lenses in each scanning optical system. .

  Therefore, a pattern (hereinafter referred to as “resist pattern”) based on the above-mentioned five types of positional deviation is drawn on an endless carrier such as an intermediate transfer belt, and the resist pattern is detected (positional deviation) by a plurality of sensors. It is proposed that a “deviation amount” is calculated based on the result, and that each image is aligned (misalignment correction) according to the deviation amount.

  Next, conventional resist pattern detection and misregistration correction operations will be described with reference to FIGS.

  17 is a block diagram showing the configuration of a conventional resist pattern detection unit (hereinafter referred to as “pattern detection unit”), and FIG. 18 shows a conventional resist pattern and pattern detection unit on an endless carrier such as an intermediate transfer belt. FIG. 19 and FIG. 20 are diagrams for explaining the conventional positional relationship between the resist pattern on the intermediate transfer belt and the pattern detection unit and the output signal of the pattern detection unit.

  17 to 20, 33k, 33y, 33m, and 33c are a black resist pattern, a yellow resist pattern, a magenta resist pattern, and a cyan resist pattern, respectively.

  As shown in FIG. 17, the pattern detection unit 50 disposed facing the endless carrier 12 includes an image sensor (hereinafter referred to as “CCD”) 51, a light source 52 such as a lamp, and reflected light to the CCD. A SELFOC lens array 53 for imaging is provided.

  In addition, as shown in FIG. 18, the pattern detection unit 50 includes a plurality of pixels in the CCD 51 arranged on a line that intersects the conveyance direction A of the endless carrier 12 at right angles, and the left and right of the endless carrier 12 in the main scanning direction. It is arrange | positioned in the edge part vicinity, respectively. Here, the pattern detection unit 50 disposed on the left side in the transport direction A is referred to as a pattern detection unit 50a, and the pattern detection unit 50 disposed on the right side in the transport direction A is referred to as a pattern detection unit 50b. Reference numerals 51a and 51b denote CCDs provided in the respective pattern detection units 50.

  Here, as is well known, the same direction as the transport direction A is the sub-scanning direction, and the direction perpendicular to the transport direction A is the main scanning direction.

  For detection of the resist pattern, as shown in FIG. 19, a resist pattern such as a predetermined straight line or figure on a line perpendicular to the conveying direction A of the endless carrier 12, for example, black at predetermined intervals. The toner images 33k, 33y, 33m, and 33c corresponding to the respective colors of yellow, magenta, and cyan are transferred, and the toner images (resist patterns) of these colors are detected by the pattern detection unit 50a and the pattern detection unit 50b. That is, the positional deviation (registration deviation) of each color is measured by the two pattern detection units 50a and 50b.

  Next, the misregistration correction operation based on the detection results detected by the two pattern detection units 50a and 50b in this way will be described.

  With respect to the sub-scanning position shift (see FIG. 16A), as shown in FIG. 19A, the time (T1) during which the resist patterns of the respective colors on the endless carrier 12 pass through the CCD 51a in the pattern detection unit 50a. ) And a predetermined design value (T) as a time difference (ΔT1 = T−T1) and the transport speed v of the endless carrier 12 (ΔY1 = ΔT1, v) Is calculated.

  Regarding the main scanning position shift (see FIG. 16B), as shown in FIG. 20A, the scanning start position of each color resist pattern on the endless carrier 12 passes through the CCD 51a in the pattern detection unit 50a. Based on the pixel position difference in the CCD 51a, that is, the pixel position difference (ΔX1), the position shift of the resist pattern of each color is calculated.

  As for the skew error (see FIG. 16C), as shown in FIG. 19B, the time required for the resist pattern of a predetermined color on the endless carrier 12 to pass through the CCD 51a of the pattern detection unit 50a and the predetermined color. On the basis of the difference between the resist pattern passing through the CCD 51b of the pattern detection unit 50b, that is, the time difference (ΔT2), and the transport speed v of the endless carrier 12 (ΔY2 = ΔT2, v) is calculated. That is, based on the difference in time (ΔT2) passing through the CCDs of the two pattern detection units for the resist pattern of the same color and the transport speed v, the skew error (ΔY2 = ΔT2) of the resist pattern of each color , V) is calculated.

  Regarding the magnification error (see FIG. 16D), as shown in FIG. 20A, the scanning start position of each color resist pattern on the endless carrier 12 passes through the CCD 51a in the pattern detection unit 50a. The difference in pixel position in the CCD 51a, that is, the pixel position difference (ΔX1) and the scanning end position of each color resist pattern on the endless carrier 12 as shown in FIG. The magnification error (ΔX3 = ΔX2−ΔX1) of the resist pattern of each color is calculated based on the difference in pixel position in the CCD 51b passing through the CCD 51b, that is, the pixel position difference (ΔX2). That is, with respect to the same resist pattern, the difference in the position of the pixel in the CCD 51a where the scan start position of the resist pattern passes through the CCD 51a of the pattern detection unit 50a (ΔX1) and the scan end position of the resist pattern are pattern detection. The magnification error (ΔX3 = ΔX2−ΔX1) of the resist pattern of the same color is calculated based on the difference (ΔX2) of the pixel position in the CCD 51b passing through the CCD 51b of the unit 50b.

  Based on the four types of positional shift amounts calculated in this way, a positional shift correction operation is performed by a positional shift correction unit (not shown).

As a tandem type color image forming apparatus, one disclosed in (Patent Document 1) or (Patent Document 2) is known.
JP 2002-40735 A Japanese Patent Laid-Open No. 2002-131997

  By the way, in the above-described conventional color image forming apparatus of the electrophotographic system using toner, since the toner is powder, the powder may float in the apparatus during the operation of the color image forming apparatus. Many.

  For this reason, powders such as floating toner come to adhere to the optical path portion of the pattern detection unit (such as Selfoc lens array) after many years of use, and this allows the powder adhered to the optical path portion to pass light. Shield (shield).

  As a result, in some cases, the resist pattern cannot be detected due to the powder adhering to the light emitting surface and the light receiving surface of the pattern detection unit. That is, the amount of light irradiated from the pattern detection unit and incident on the resist pattern due to being shielded by the powder or the amount of light (reflected light) from the resist pattern received by the pattern detection unit is reduced. The pattern cannot be detected.

  As a countermeasure against such a problem, a transparent plate (transparent plate) such as glass is disposed between the pattern detection unit and the endless carrier, and the toner is removed when the transparent plate becomes dirty due to adhesion of toner. A structure that cleans a transparent plate that has become dirty due to adhesion of toner, such as a structure that allows the toner to adhere to the transparent plate in conjunction with opening and closing of the cover of the main body device, is adopted.

  Moreover, the structure which cleans a transparent plate is employ | adopted also in the said (patent document 1) and the said (patent document 2) thing.

  However, along with the downsizing of the apparatus, it has become difficult to clean the transparent plate provided between the pattern detection unit and the endless carrier due to the structure of the pattern detection unit and the structure of the apparatus.

  Therefore, the above-described conventional color image forming apparatus has a problem that it is impossible to accurately correct the positional deviation of each color image based on the result of detection by the pattern detection unit.

  SUMMARY An advantage of some aspects of the invention is that it provides a color image forming apparatus capable of accurately correcting misregistration of images of a plurality of colors.

  In order to solve this problem, a color image forming apparatus of the present invention is formed on an endless carrier on which a plurality of color toner images are transferred and a predetermined pattern is formed, and on the endless carrier. A color image forming apparatus that corrects misalignment of the toner images of the plurality of colors based on the detection result by the pattern detection unit, the pattern detection unit detecting a predetermined pattern, and the endless carrier And a pair of electrodes disposed between the pair of electrodes and a predetermined voltage is applied between the pair of electrodes to generate an electric field between the electrodes.

  In a preferred embodiment of the present invention, the pattern detection means comprises: a light emitting means for emitting light toward the endless carrier; and a light receiving means for receiving the light reflected by the unsupported carrier, The pair of electrodes are arranged between the endless carrier and the pattern detection unit and so that the pair of electrodes sandwich an optical path formed between the light emitting unit and the light receiving unit. It is what.

  In a further preferred aspect of the present invention, the pair of electrodes are configured to be conductive plates.

  In a further preferred aspect of the present invention, the pair of electrodes are configured to be conductive wires.

  In a further preferred aspect of the present invention, the toner relating to the plurality of color toner images floating in the space between the endless carrier and the pattern detection means by the electric field generated between the pair of electrodes is supplied to the pair of electrodes. It is set as the structure attached to any one electrode among these electrodes.

  According to the present invention, it is possible to obtain an effective effect that it is possible to accurately correct misregistration of images of a plurality of colors based on the result of detection by the pattern detection unit.

  Further, according to the present invention, an electric field is generated between the pair of electrodes disposed between the endless carrier and the pattern detection means, so that a space between the endless carrier and the pattern detection means is formed. The floating toner can be forcibly attached to any one of the pair of electrodes, and an effective effect of preventing the toner from adhering to the pattern detection unit can be obtained.

  Furthermore, according to the present invention, since the pair of electrodes are disposed so as to sandwich the optical path formed between the light emitting means and the light receiving means, the endless carrier and the pattern detection are provided on the light emitting means and the light receiving means. The floating toner can be forcibly attached to any one of the pair of electrodes before the floating toner adheres to the space between the light emitting means and the light emitting surface of the light emitting means and the light receiving means. An effective effect is obtained that toner can be prevented from adhering to the light receiving surface.

  Furthermore, according to the present invention, the toner floating in the space between the endless carrier and the pattern detecting means can be forcibly attached to any one of the pair of electrodes having a simple structure. An effective effect is obtained.

  The invention according to claim 1 of the present invention detects an endless carrier on which a plurality of color toner images are transferred and a predetermined pattern is formed, and a predetermined pattern formed on the endless carrier. A color image forming apparatus that corrects misregistration of toner images of a plurality of colors based on a result of detection by the pattern detection means, and is arranged between the endless carrier and the pattern detection means. A color image forming apparatus having a pair of electrodes provided, applying a predetermined voltage between the pair of electrodes, and generating an electric field between the electrodes, an endless carrier and a pattern detection unit Since an electric field is generated between a pair of electrodes disposed between the endless carrier and the pattern detection means, the toner floating in the space between the endless carrier and the pattern detection means is applied to one of the pair of electrodes. Forcing to adhere Can have the effect of being able to prevent the toner from adhering to the pattern detection means. Accordingly, there is an effect that it is possible to correct the positional deviation of the images of a plurality of colors accurately based on the detection result by the pattern detection means.

  According to a second aspect of the present invention, in the invention according to the first aspect, the pattern detection means includes a light emitting means for emitting light toward the endless carrier, and light reflected by the unsupported carrier. A pair of electrodes arranged between the endless carrier and the pattern detecting unit and sandwiching an optical path formed between the light emitting unit and the light receiving unit. The color image forming apparatus is characterized in that a pair of electrodes are arranged so as to sandwich an optical path formed between the light emitting means and the light receiving means. Before the floating toner adheres to the space between the endless carrier and the pattern detecting means, the floating toner can be forcibly attached to one of the pair of electrodes, and the light emission Of light emitting surface and light receiving means It has an effect of toner to the light plane can be prevented from adhering.

  According to a third aspect of the present invention, there is provided a color image forming apparatus according to the first or second aspect, wherein the pair of electrodes are conductive plates, and the endless carrier and The toner floating in the space between the pattern detection means can be forcibly adhered to any one of the pair of electrodes having a simple structure, that is, the conductive plate.

  According to a fourth aspect of the present invention, there is provided a color image forming apparatus according to the first or second aspect, wherein the pair of electrodes are conductive lines, and the endless carrier and The toner floating in the space between the pattern detection means can be forcibly attached to any one of a pair of electrodes having a simple structure, that is, a conductive line.

  According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the electric field generated between the pair of electrodes causes a gap between the endless carrier and the pattern detection means. A color image forming apparatus characterized in that a toner floating in a space and relating to a toner image of a plurality of colors is attached to one of a pair of electrodes, between an endless carrier and a pattern detecting means The toner floating in the space can be forcibly attached to any one of the pair of electrodes, and the toner can be prevented from adhering to the pattern detecting means.

  Hereinafter, the best mode for carrying out the present invention will be described more specifically with reference to the drawings. Here, in the accompanying drawings, the same reference numerals are given to the same members, and duplicate descriptions are omitted. In addition, since description here is the best form by which this invention is implemented, this invention is not limited to the said form.

(Embodiment 1)
FIG. 1 is a configuration diagram showing the configuration of a color image forming apparatus according to Embodiment 1 of the present invention, FIG. 2 is a diagram for explaining the configuration of a pattern detection means and the path of light, and FIG. 3 is a circuit section of a positional deviation detection means. 4 is a block diagram showing a block configuration, FIG. 4 is a diagram for explaining adjustment of light emission current to the light emitting means of the pattern detecting means, and FIG. 5 is an arrangement relationship between the endless carrier, the pattern detecting means, and the resist pattern on the endless carrier. FIG. 6 is a diagram for explaining the path of light emitted from the light emitting means during detection of the resist pattern by the pattern detecting means, and FIG. 7 is a diagram showing the positional deviation detecting means when the pattern detecting means detects the resist pattern. FIG. 8 is a diagram for explaining the operation of the circuit unit, FIG. 8 is a diagram showing information on the pulse on time and off time stored in the storage means, and FIG. 9 is a diagram between the endless carrier and the pattern detection unit. FIG. 10 is a diagram illustrating a state in which a pair of electrodes is disposed, FIG. 10 is a diagram for explaining the arrangement relationship between the pattern detection means and the coincident electrode viewed from the direction of arrow B in FIG. 9, and FIG. FIG. 12 is a diagram for explaining a state of an electric field generated when a voltage from a power source is applied. FIG. 12 shows a pair of electrodes arranged between the endless carrier and the pattern detecting means, and a predetermined voltage is applied between the electrodes. FIG. 13 is a diagram showing the state of the floating toner when the toner image is detected by the pattern detection unit in the state where the pattern is detected, and FIG. 13 is a state where the toner is floating between the endless carrier and the pattern detection unit FIG. 14 is a diagram showing a state where toner is attached to the light emitting surface of the light emitting means and the light receiving surface of the light receiving means of the pattern detecting means, and FIG. 15 is a diagram showing the amount of light emitted from the light emitting means of the pattern detecting means due to the adhesion of toner. Signal amplification even if the maximum The voltage output from a view showing a state that can not be adjusted to the voltage V0.

  The configuration of the color image forming apparatus according to the embodiment of the present invention will be described with reference to FIG.

  As shown in FIG. 1, the color image forming apparatus includes four image forming stations 1a, 1b, 1c, and 1d. The image forming stations 1a, 1b, 1c, and 1d are photoconductors 2a and 2a as image carriers. 2b, 2c, 2d. Around each of these photoreceptors 2a, 2b, 2c, 2d, dedicated charging means 3a, 3b, 3c, 3d, developing means 4a, 4b, 4c, 4d, cleaning means 5a, 5b, 5c, 5d, images Exposure means 6a, 6b, 6c, 6d of a scanning optical system for irradiating each photoconductor with light according to information, and transfer devices 8a, 8b, 8c, 8d in the transfer means 7 are arranged.

  The image forming stations 1a, 1b, 1c and 1d are means for forming a yellow image, a magenta image, a cyan image and a black image, respectively. Lights 9a, 9b, 9c and 9d corresponding to the yellow image, magenta image, cyan image and black image are output from the exposure means 6a, 6b, 6c and 6d. An endless carrier in the form of an unsupported belt supported by a pair of support rollers 10 and 11 below the photoreceptors 2a, 2b, 2c, and 2d in a mode of passing through the image forming stations 1a, 1b, 1c, and 1d. 12 is arranged. The endless carrier 12 moves in the direction of arrow A in FIG.

  The pattern detecting means 14 arranged facing the endless carrier 12 detects a resist pattern from a resist pattern generating means (not shown). The misregistration detection unit 15 calculates the misregistration amount based on the misregistration information detected by the pattern detection unit 14.

  A sheet material 17 such as paper stored in a paper feed cassette 16 is fed by a paper feed roller 18 and is discharged to a paper discharge tray (not shown) through a sheet material transfer roller 19 and a fixing unit 20.

  In the color image forming apparatus described above, a latent image of the black component color of the image information is formed on the photoreceptor 2d by known electrophotographic process means such as the charging means 3d and the exposure means 6d of the image forming station 1d. Thereafter, the developing unit 4d visualizes the latent image on the photoreceptor 2d as a black toner image with a developer having black toner. Further, the black toner image on the photoreceptor 2d is transferred to the endless carrier 12 by the transfer device 8d.

  While the black toner image is being transferred to the endless carrier 12, the image forming station 1c is subjected to the known electrophotographic process means such as the charging means 3c and the exposure means 6c of the image forming station 1c on the photoreceptor 2c. A cyan component color latent image is formed, and then a cyan toner image is obtained on the photoreceptor 2c by the developing means 4c using a developer having cyan toner. Further, the cyan toner image on the photoreceptor 2c is transferred to the endless carrier 12 by the transfer device 8c, so that the cyan toner image is superimposed on the black toner image previously transferred onto the endless carrier 12. Is done.

  Thereafter, the magenta toner image and the yellow toner image are formed in the same manner, and when the four color toner images are superimposed on the endless carrier 12, the sheet material transfer roller 19 and the support roller 11 The four color toner images on the endless carrier 12 are batch-transferred onto the sheet material 17 fed from the paper feed cassette 16 by the paper feed roller 18, and the four color toner images are further transferred. The batch-transferred sheet material 17 is conveyed toward the fixing unit 20. Then, the four-color toner images transferred to the sheet material 17 by the fixing unit 20 are heated and fixed, whereby a full-color image is obtained on the sheet material 17.

  The photosensitive members 2a, 2b, 2c, and 2d that have been transferred have their residual toner removed by the cleaning means 5a, 5b, 5c, and 5d, and are ready for the next subsequent image formation, thus completing the printing operation. .

  Next, the position shift detection operation will be described. Here, only the positional deviation detection operation in the traveling direction of the endless carrier 12 will be described, and the positional deviation detection operation in the direction perpendicular to the traveling direction of the endless carrier 12 will be omitted.

  FIG. 2 shows a configuration diagram of a resist pattern detection means (hereinafter referred to as “pattern detection means”) 14 disposed facing the endless carrier 12. Here, the configuration of one pattern detection means 14 of a pair of pattern detection means 14 disposed at both ends of the endless carrier 12 in the main scanning direction is shown. In FIG. 2, the arrow indicated by reference numeral 140 indicates the pattern detection position.

  As shown in FIG. 2, the pattern detection means 14 has a light emitting means 22 and a light receiving means 23 that face the endless carrier 12 at an angle θ. The light emitted from the light emitting means 22 travels straight and is reflected by the endless carrier 12 (the pattern detection position 140). However, since the endless carrier 12 has high smoothness, most of the light is directed to the endless carrier 12. On the other hand, the light is reflected at an angle θ (regular reflection) and enters the light receiving means 23.

  As shown in FIG. 3, the misregistration detection means 15 includes a light emission current control means 24, a light emission current detection means 25, a current-voltage conversion means 26, a signal amplifier 27, a comparator 28, a reference power supply 29, a CPU 30, and a count means 31. And storage means 32.

  In FIG. 3, when the endless carrier 12 starts to travel, the CPU 30 controls the light emission current detection means 25 while monitoring the light emission current control means 24 to adjust the constant current to flow through the light emission means 22.

  A current photoelectrically converted according to the amount of received light flows through the light receiving means 23, and this current also flows through the current-voltage converting means 26. The current-voltage conversion means 26 converts the input current into a voltage. Since the voltage converted by the current-voltage conversion means 26 is minute, it is amplified by the signal amplifier 27 and then input to one input terminal of the A / D converter (not shown) of the CPU 30 and the comparator 28.

  The output voltage (reference voltage) of the reference power supply 29 is input (applied) to the other input terminal of the comparator 28 where the output voltage of the signal amplifier 27 is input (applied) to one input terminal. Further, from the output terminal of the comparator 28, the voltage input to one input terminal is compared with the voltage level of the reference voltage input to the other input terminal, and a binarized signal is output. This binarized signal is input to the counting means 31.

  The CPU 30 adjusts the light emission current so that the input voltage becomes a predetermined voltage V0 shown in FIG. Specifically, when the input voltage is lower than the voltage V0, the CPU 30 controls the light emission current control means 24 to increase the current flowing through the light emission means 22, whereas the input voltage is higher than the voltage V0. In some cases, the light emission current control means 24 is controlled to reduce the current flowing through the light emission means 22, and finally the light emission current is adjusted so that the input voltage becomes a value in the vicinity of the voltage V0.

  The CPU 30 having adjusted the input voltage to the voltage V0 instructs a pattern generation means (not shown) to print a resist pattern (predetermined pattern) as shown in FIG. 5 on the endless carrier 12. In FIG. 5, reference numerals 14a and 14b denote pattern detecting means disposed on the upper ends of both ends of the endless carrier 12 in the main scanning direction, and 33k, 33y, 33m and 33c denote black, yellow, magenta, A pattern set (resist pattern) of four colors of cyan is shown. Here, the resist patterns 33k, 33y, 33m, and 33c are patterns (pattern arrangement) extending in a direction parallel to the traveling direction of the endless carrier 12 (the direction of arrow A in FIG. 5). This is to detect only the positional deviation of the endless carrier 12 in the traveling direction.

  In FIG. 6, in the pattern detecting means 14, most of the light emitted from the light emitting means 22 is positively transmitted by the endless carrier 12 until just before detecting the resist pattern (predetermined pattern). Reflected and incident on the light receiving means 23. On the other hand, during the detection of the resist pattern (predetermined pattern), the resist patterns 33k, 33y, 33m, and 33c are toner images formed of powder and have low smoothness. Therefore, as shown in FIG. Most of the light cannot reach the light receiving means 23 because it is diffusely reflected on the black resist pattern 33k. The same can be said for the light for the other resist patterns 33y, 33m, and 33c.

  FIG. 7 is a diagram for explaining the operation of the circuit unit of the positional deviation detection unit 14 when the pattern detection unit 14 detects the resist patterns 33k, 33y, 33m, and 33c.

  7A shows the output signal (output voltage signal) of the signal amplifier 27, FIG. 7B shows the output voltage (reference voltage) signal of the reference power supply 29, and FIG. 7C shows the output signal of the comparator 28. (C-1) shows waveforms explaining the off time and on time of the output signal of the comparator 28, and (d) shows a clock signal generated in the counting means 31.

  As shown in FIG. 7A, the output voltage signal amplified by the signal amplifier 27 is maintained at the adjusted voltage V0 (see FIG. 4) immediately before detecting the resist pattern, that is, until reaching the time point t1. .

  However, when the pattern detection unit 14 starts to detect the black resist pattern 33k that has reached the pattern detection position 140 (see FIG. 2) at time t1, the light that has reached the black resist pattern 33k is black as described above. Light is diffused and reflected by the resist pattern 33k, and light does not enter the light receiving means 23. Therefore, the voltage (output voltage signal) amplified by the signal amplifier 27 gradually decreases.

  At time t2, when the black resist pattern 33k passes the pattern detection position 140, the voltage (output voltage signal) amplified by the signal amplifier 27 returns to the voltage V0 again. The output voltage signal of the signal amplifier 27 that has returned to the voltage V0 is maintained until time t3 when the next yellow resist pattern 33y reaches the pattern detection position 140.

  Thereafter, every time the resist patterns 33y, 33m, and 33c pass the pattern detection position 140, the same waveform as in the case of pattern detection for the black resist pattern 33k is repeated.

  The output voltage signal (see FIG. 7A) output from the signal amplifier 27 is input to one input terminal of the comparator 28. The output voltage signal input to one input terminal of the comparator 28 is compared at the reference voltage input to the other input terminal, for example, the voltage level of the reference voltage V1 shown in FIG. Is done.

  In this case, the output voltage signal is binarized to a value of 0 (low level) if it is less than the voltage level of the reference voltage V1, and to a value of 1 (high level) if it is greater than or equal to the voltage level of the reference voltage V1, The pulse waveform (pulse signal) is as shown in FIG. For example, in FIG. 7C, a pulse signal having a low level during the period from the time point ta to the time point tb and a high level during the period from the time point tb to the time point tc is generated. The time series of the time points t1 to t3 and the time points ta to tc are in the order of the time point t1, the time point ta, the time point tb, the time point t2, the time point t3, and the time point tc.

  The signal binarized in this way (see FIG. 7C), that is, the pulse signal is input to the counting means 31, and the counter (not shown) in the counting means 31 causes the signal in FIG. In synchronization with the clock signal as shown, the pulse off time (time tw0 shown in FIG. 7 (c-1)) and the pulse on time (time tw1 shown in FIG. 7 (c-1)) are respectively It is counted as the number of clock signals (see FIG. 7 (d)), that is, the number of clock signals (see FIG. 7 (d)) generated during the off time or on time of the pulse. The count values corresponding to the off time and on time of these pulses are stored in the storage means 32.

  FIG. 8 shows information on the on time and off time of the pulses stored in the storage means 32. In FIG. 8, the on time is time tw1, time tw3, and time tw5, while the off time is time tw0, time tw2, time tw4, and time tw6.

  The position shift is detected by measuring the shift amount of other toner images (yellow, magenta, and cyan images) with respect to the black toner image.

  Therefore, first, the CPU 30 uses the time information of tw0 to tw6 to time T1-y, T1-m, T1 from the center of the black resist pattern 33k to the center of the other resist patterns (resist patterns 33y, 33m, 33c). -C is obtained by calculating the following (Equations 1 to 3).

T1-y = (1/2) * tw0 + tw1 + (1/2) * tw2 (Equation 1)
T1-m = (1/2) × tw0 + tw1 + tw2 + tw3 + (1/2) × tw4 (Equation 2)
T1-c = (1/2) * tw0 + tw1 + tw2 + tw3 + tw4 + tw5 + (1/2) * tw6 (Equation 3)
However, the time T1-y indicates the time from the center of the black resist pattern 33k to the center of the yellow resist pattern 33y, and the time T1-m is from the center of the black resist pattern 33k to the center of the magenta resist pattern 33m. The time T1-c indicates the time from the center of the black resist pattern 33k to the center of the cyan resist pattern 33c.

  Then, the CPU 30 calculates times T0-y and T0 obtained in advance from the center of the black resist pattern 33k to the center of the other resist patterns (resist patterns 33y, 33m, 33c) when there is no positional deviation. The difference Δty, Δtm, Δtc between −m, T0-c and the time T1-y, T1-m, T1-c obtained by calculating the above (Equation 1) is expressed by the following (Equation 4 -6) is calculated and obtained.

Δty = (T1-y)-(T0-y) (Equation 4)
Δtm = (T1-m)-(T0-m) (Equation 5)
Δtc = (T1-c)-(T0-c) (Equation 6)
However, time T0-y indicates a time obtained by pre-calculation from the center of the black resist pattern 33k to the center of the yellow resist pattern 33y, and time T0-m is from the center of the black resist pattern 33k to magenta. The time obtained by pre-calculating to the center of the resist pattern 33m is shown, and the time T0-c is the time obtained by pre-calculating from the center of the black resist pattern 33k to the center of the cyan resist pattern 33c. .

  The positional deviation amounts Δdy, Δdm, and Δdc are obtained by calculating the following (Equations 7 to 9) when the speed of the endless carrier 12 is Vx (calculated by the CPU 30).

Δdy = Δty × Vx (Expression 7)
Δbdm = Δtm × Vx (Equation 8)
Δdc = Δtc × Vx (Equation 9)
Here, Δdy represents the amount of positional deviation of the yellow toner image, Δdm represents the amount of positional deviation of the magenta toner image, and Δdc represents the amount of positional deviation of the cyan toner image.

  A misregistration correction unit (not shown) corrects misregistration based on the misregistration amounts Δdy, Δdm, and Δdc obtained by the misregistration detection unit 15.

  Next, a pair of electrodes according to the present invention will be described.

  As shown in FIG. 9, the pair of electrodes 36 a and 36 b is a space between the endless carrier 12 and the pattern detection means 14, and the pair of electrodes 36 a and 36 b is between the light emitting means 22 and the light receiving means 23. Are arranged so as to sandwich the optical path formed by The pair of electrodes 36a and 36b have conductivity, and are formed in a plate shape, for example.

  In this specification, the optical path formed between the light emitting means 22 and the light receiving means 23 is the angle θ with respect to the endless carrier 12 when the light emitted from the light emitting means 22 is irradiated as shown in FIG. , And the light path reflected from the endless carrier 12 at an angle θ (regular reflection) until it enters the light receiving means 23. That is, in FIG. 2, the light radiated from the light emitting surface of the light emitting means 22 reaches the endless carrier 12 corresponding to the pattern detection position 140 in FIG. 2 is an optical path including an optical axis indicated by a one-dot chain line in FIG. 2 until the reflected light) enters the light receiving surface of the light receiving means 23.

  In FIG. 10, the pattern detection means 14 a is arranged on the left side of both end portions in the main scanning direction of the endless carrier 12 in the transport direction of the endless carrier 12 (direction of arrow A in FIG. 9). The pattern detection means 14 is a pattern detection means 14 disposed on the right side of both end portions in the main scanning direction of the endless carrier 12 in the transport direction of the endless carrier 12. .

  Electrodes 36a and 36b are disposed so as to sandwich the optical paths of the two pattern detection means 14a and 14b, that is, the optical paths formed between the light emitting means 22 and the light receiving means 23, respectively.

  As shown in FIG. 11, the electrode 36a is connected to the negative electrode of the DC power supply 36E and grounded, while the electrode 36b is connected to the positive electrode of the DC power supply 36E. That is, the voltage V2 is applied between the electrode 36a and the electrode 36b.

  When the voltage V2 is applied between the electrode 36a and the electrode 36b, an electric field is generated between the electrode 36a and the electrode 36b. The direction of the electric field at this time is in the direction of arrow C in FIG. 11 (from the electrode 36b toward the electrode 36a).

  When the black toner image 33K, the yellow toner image Y, the magenta toner image M, and the cyan toner image C are transferred onto the endless carrier 12, the pattern detection unit 14 detects the black toner image 33K. FIG. 12 shows a state in which the voltage V2 is applied between the electrodes 36a and 36b in a state where the electrodes are in the closed state.

  As shown in FIG. 12, the plurality of toners 34 floating in the space between the pattern detecting means 14 and the endless carrier 12 are light emitting means 22 (light emitting surface thereof) and light receiving means 23 (light receiving surface thereof). Before adhering to the electrode 36b, the electric field generated between the electrode 36a and the electrode 36b is attracted in the direction of the electrode 36b, and finally adheres to the electrode 36b. Therefore, the floating toner 34 does not adhere to the light emitting means 22 (the light emitting surface) and the light receiving means 23 (the light receiving surface).

  The toner 34 adheres to the positive electrode 36b because the toner 34 is originally charged to the negative electrode. When the toner 34 is charged to the positive electrode, the toner 34 adheres to the electrode 36a.

  By the way, since the magnitude of the electric field is proportional to the magnitude of the voltage and inversely proportional to the distance between the electrodes, the voltage V2 is preferably a high voltage such as the charging means 3a, 3b, 3c, 3d, Further, it is desirable to make the distance between the electrode 36a and the electrode 36b as short as possible.

  As described above, in the present embodiment, since the pair of electrodes 36 a and 36 are disposed so as to sandwich the optical path formed between the light emitting means 22 and the light receiving means 23, the light emitting means 22 and the light receiving means 23. Before the floating toner adheres to the space between the endless carrier 12 and the pattern detection means 14, the floating toner is applied to one of the pair of electrodes (in this example, the electrode 36b). The toner can be forcibly adhered, and toner can be prevented from adhering to the light emitting surface of the light emitting means 22 and the light receiving surface of the light receiving means 23.

  Here, pattern detection when a pair of electrodes is not disposed in the space between the pattern detection means 14 and the endless carrier 12 will be described with reference to FIGS.

  In FIG. 13, since the black toner image 33K, the yellow toner image 33Y, the magenta toner image 33M, and the cyan toner image 33C are composed of powder, the photoreceptors 2a, 2b, 2c, and 2d corresponding to the respective colors. In some cases, the toner image of these colors is not transferred but floats in the air on the endless carrier 12.

  When the plurality of toners 34 floating in the air reach the space between the pattern detection means 14 and the endless carrier 12 as shown in FIG. 13, any toner 34 in the plurality of toners 34 is The case where it adheres to the light emission means 22 or the light reception means 23 occurs, and the case where it adheres to the light emission surface of the light emission means 22 or the light reception surface of the light reception means 23 as shown in FIG.

  When a large amount of toner 34 adheres to the light emitting surface of the light emitting means 22, the light emitted from the light emitting means 22 (the light emitting surface thereof) decreases, and a large amount of toner 34 adheres to the light receiving surface of the light receiving means 23. In this case, the light (incident light) incident on the light receiving means 23 decreases. In either case, the amount of light received by the light receiving means 23 is reduced as compared with the case where the toner 34 does not adhere to the light emitting means 22 or the light receiving means 23.

  Therefore, the output voltage obtained by amplifying the voltage corresponding to the current corresponding to the amount of light received by the light receiving unit 23 by the signal amplifier 27 is adhered to the light emitting surface of the light emitting unit 22 or the light receiving surface of the light receiving unit 23. Compared with the case where it did not, the amount of light decreases.

  Therefore, as shown in FIG. 15, even when the CPU 30 adjusts the input voltage (the output voltage of the signal amplifier 27) to the voltage V0, the current flowing through the light emitting means 22 is controlled to increase to the maximum. In some cases, the input voltage does not rise to the voltage V0 and cannot be detected.

  On the other hand, in the present embodiment, as described with reference to FIGS. 9 to 12, a pair (two sheets) of facing each other in the space between the pattern detection means 14 and the endless carrier 12. Electrodes 36a and 36b are disposed, and a charged toner 34 is forcibly attached to one electrode by applying a voltage between the pair of electrodes to generate an electric field, and is suspended in the air. The toner 34 is prevented from adhering to the light emitting means 22 (the light emitting surface thereof) and the light receiving means 23 (the light receiving surface thereof).

  In the present embodiment, the pair of electrodes are conductive plates (plate-like), but the present invention is not limited to this, and the pair of electrodes may be conductive wires (linear). .

  As described above, according to the present embodiment, the pair of electrodes 36a and 36b are disposed so as to sandwich the optical path formed between the light emitting means 22 and the light receiving means 23, and between these electrodes 36a and 36b. Since an electric field is generated by applying a predetermined voltage to the light emitting means 22 (the light emitting surface thereof) and the light receiving means 23 (the light receiving surface thereof), the endless carrier 12 and the pattern detecting means 14 are disposed between them. The floating toner can be forcibly attached to one of the pair of electrodes before the floating toner adheres to the space, and the toner is applied to the light emitting surface of the light emitting means and the light receiving surface of the light receiving means. Can be prevented from adhering.

  As described above, in the pattern detecting unit 14 having the light emitting unit 22 and the light receiving unit 23, the toner floating in the air does not adhere. Therefore, accurate positional deviation information can be obtained, and the positional deviation detecting unit 15 can obtain the accurate positional information. It is possible to calculate an accurate positional deviation amount based on the deviation information. As a result, it is possible to accurately correct the misalignment of images of a plurality of colors based on the exact misalignment amount.

  By correcting the misregistration of images of a plurality of colors in this way, it is possible to print a high-quality color image with no misregistration of color images.

  The present invention can be applied not only to an electrophotographic color image forming apparatus but also to a thermal transfer type ink jet type color image forming apparatus.

1 is a configuration diagram showing the configuration of a color image forming apparatus according to Embodiment 1 of the present invention. The figure explaining the structure of a pattern detection means, and the course of light The block diagram which shows the block configuration of the circuit part of a position shift detection means The figure explaining adjustment of the light emission current with respect to the light emission means of a pattern detection means The figure explaining the arrangement | positioning relationship between an endless carrier, a pattern detection means, and the resist pattern on an endless carrier The figure explaining the course of the light emitted from the light emission means during the resist pattern detection by the pattern detection means The figure explaining operation | movement of the circuit part of a position shift detection means when a pattern detection means detects a resist pattern The figure which shows the information of the ON time and OFF time of the pulse memorize | stored in the memory | storage means The figure which shows the state which has arrange | positioned a pair of electrode between an endless carrier and a pattern detection part. The figure explaining the arrangement | positioning relationship between the pattern detection means seen from the direction of arrow B of FIG. The figure explaining the state of the electric field which generate | occur | produces when the voltage from DC power supply is applied between a pair of electrodes A floating toner when a toner image is detected by the pattern detection means in a state where a pair of electrodes are arranged between the endless carrier and the pattern detection means and a predetermined voltage is applied between the electrodes. Diagram showing the state of The figure which shows the state which the toner is floating between an endless carrier and a pattern detection means The figure which shows the state which the toner adhered to the light emission surface of the light emission means of a pattern detection means, and the light reception surface of a light reception means. The figure which shows a mode that the voltage output from a signal amplifier cannot be adjusted to voltage V0 even if the light emission means of a pattern detection means maximizes the light emission amount by having adhered toner. The figure explaining the kind of position shift of a transfer image The block diagram which shows the structure of the conventional pattern detection part The figure explaining the arrangement | positioning relationship between the resist pattern of a conventional intermediate transfer belt, and a pattern detection part The figure explaining the arrangement relationship between the resist pattern on the intermediate transfer belt and the pattern detection unit and the output signal of the pattern detection unit in the past The figure explaining the arrangement relationship between the resist pattern on the intermediate transfer belt and the pattern detection unit and the output signal of the pattern detection unit in the past

Explanation of symbols

1a, 1b, 1c, 1d Image forming stations 2a, 2b, 2c, 2d Photoconductors 3a, 3b, 3c, 3d Charging means 4a, 4b, 4c, 4d Developing means 5a, 5b, 5c, 5d Cleaning means 6a, 6b, 6c, 6d Exposure means 7 Transfer means 8a, 8b, 8c, 8d Transfer device 9a, 9b, 9c, 9d Light 10, 11 Support roller 12 Endless carrier 14, 14a, 14b Pattern detection means 15 Position shift detection means 16 Supply Paper cassette 17 Sheet material 18 Paper feed roller 19 Sheet material transfer roller 20 Fixing means 21 Home sensor 22 Light emitting means 23 Light receiving means 24 Light emission current control means 25 Light emission current detection means 26 Current-voltage conversion means 27 Signal amplifier 28 Comparator 29 Reference Power supply 30 CPU
31 Count means 32 Storage means 33K Black toner image 33Y Yellow toner image 33M Magenta toner image 33C Cyan toner image 33k Black resist pattern 33y Yellow resist pattern 33m Magenta resist pattern 33c Cyan resist pattern 34 Toner 36a, 36b Electrode 36E DC power supply 140 Pattern detection position

Claims (5)

An endless carrier on which a plurality of color toner images are transferred and a predetermined pattern is formed; and pattern detection means for detecting the predetermined pattern formed on the endless carrier, the pattern detection A color image forming apparatus that corrects misalignment of the toner images of the plurality of colors based on a result of detection by a means;
Having a pair of electrodes disposed between the endless carrier and the pattern detecting means;
A color image forming apparatus, wherein a predetermined voltage is applied between the pair of electrodes to generate an electric field between the electrodes. The pattern detecting means includes
A light emitting means for emitting light toward the endless carrier;
A light receiving means for receiving the light reflected by the unsupported carrier,
The pair of electrodes includes:
The pair of electrodes are disposed between the endless carrier and the pattern detection means so as to sandwich an optical path formed between the light emitting means and the light receiving means. Item 2. A color image forming apparatus according to Item 1. The color image forming apparatus according to claim 1, wherein the pair of electrodes are conductive plates. The color image forming apparatus according to claim 1, wherein the pair of electrodes are conductive lines. Due to the electric field generated between the pair of electrodes, the toner associated with the plurality of color toner images floating in the space between the endless carrier and the pattern detection means is removed from either one of the pair of electrodes. The color image forming apparatus according to claim 1, wherein the color image forming apparatus is attached to an electrode.

Images