JP2006276394A - Multicolor image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inline multicolor image forming apparatus of a low cost type that has no paper conveying belts, which is designed to achieve a reduction in time needed for color shift detection control and a reduction in the cost of a color shift detection sensor by exerting color shift correction control without printing a color shift detection pattern onto a recording material and by detecting a change in distance with time in a color shift causing area in the image forming apparatus, thereby providing an image with feedback. <P>SOLUTION: The multicolor image forming apparatus of an electrophotographic system includes: a plurality of photoreceptors; latent image forming means for forming electrostatic latent images on the photoreceptors; developing means for developing the electrostatic images into toner images; a conveying means for conveying a recording medium; a transfer means for transferring the toner images to the recording medium; and fixing means for fixing the toner images to the recording medium. The image forming apparatus is characterized by having a position detecting means for detecting the relative positions of the plurality of photoreceptors, an information processing means for converting an output from the distance measuring means into a physical quantity, and a means for correcting an image forming position according to the calculated physical quantity. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrophotographic multicolor image forming apparatus having a plurality of image forming units, such as a color printer and a color copying machine.

  Various types of electrophotographic color image forming apparatuses have been proposed which have a plurality of image forming units for speeding up and sequentially transfer images of different colors onto a recording material held on a conveying belt. Yes.

  By the way, as a problem of the apparatus having the plurality of image forming units as described above, due to mechanical accuracy and the like, the movement of the plurality of photosensitive drums and the conveyor belt, and the photosensitive drum at the transfer position of each image forming unit are included. For example, the relationship between the movement amount of the outer peripheral surface and the conveyance belt is different for each color and does not match when the images are superimposed, resulting in color misregistration. In particular, in an apparatus having a plurality of image forming units having a laser scanner and a photosensitive drum, there is an error in the distance between the laser scanner and the photosensitive drum in each image forming unit. A difference occurs in the scanning width of the laser on the drum, and color misregistration occurs.

  An example of color misregistration is shown in FIG. 22 indicates the original image position, and 21 indicates the image position when color misregistration occurs. Also, (a), (b), and (c) are cases where there is a color shift in the main scanning direction, but for the sake of explanation, two lines are drawn apart in the transport direction. (A) shows an inclination shift of the main scanning line, and occurs when there is an inclination between the optical unit and the photosensitive drum. For example, the position is corrected in the direction of the arrow by adjusting the position of the optical unit or the photosensitive drum or the position of the lens. (B) shows color misregistration due to variations in the main scanning line width, which occurs due to a difference in the distance between the optical unit and the photosensitive drum. It tends to occur when the optical unit is a laser scanner. For example, the image frequency is finely adjusted (if the scanning width is long, the frequency is increased) and the length of the scanning line is changed to correct in the arrow direction. (C) shows a writing position error in the main scanning direction. For example, if the optical unit is a laser scanner, it is corrected in the direction of the arrow by adjusting the writing start timing from the beam detection position. (D) shows the writing position error in the paper transport direction. For example, the correction is made in the direction of the arrow by adjusting the writing start timing of each color from the detection of the leading edge of the paper.

  In order to correct these color misregistrations, a color misregistration detection pattern is formed for each color on the conveyance belt, and detected by a pair of photosensors provided on both sides of the conveyance belt downstream portion. Various adjustments as described above are performed according to the amount.

FIG. 3 shows an example of a color misregistration detection pattern. Reference numerals 33 and 34 are patterns for detecting a color misregistration amount in the paper conveyance direction, and 35 and 36 are patterns for detecting a color misregistration amount in the main scanning direction orthogonal to the paper conveyance direction. In this example, the inclination is 45 degrees. , A to d represent black (hereinafter Bk), yellow (hereinafter Y), magenta (M) and cyan (C). Reference numerals tsf1 to 4, tmf1 to 4, tsr1 to 4, and tmr1 to 4 indicate detection timings of the respective patterns, and arrows indicate the moving direction of the conveyor belt 31. The moving speed of the conveyance belt 31 is vmm / s, Bk is a reference color, the theoretical distance between each color of the paper conveyance direction pattern and the Bk pattern is dsYmm, dsMmm, dsCmm, the pattern for the conveyance direction of each color and the main scanning direction. The measured distances between the patterns are dmfBkmm, dmfYmm, dmfMmm, dmfCmm, dmrBkmm, dmrYmm, dmrMmm, and dmrCmm, respectively. With Bk as a reference color, the positional deviation amount δes of each color in the transport direction is
δesY = v * {(tsf2−tsf1) + (tsr2−tsr1)} / 2−dsY [Formula 1]
δesM = v * {(tsf3−tsf1) + (tsr3−tsr1)} / 2−dsM [Formula 2]
δesC = v * {(tsf4-tsf1) + (tsr4-tsr1)} / 2-dsC [Formula 3]
It becomes. With respect to the main scanning direction, the positional deviation amounts δemf and δemr for each of the left and right colors are
dmfBk = v * (tmf1-tsf1) [Formula 4]
dmfY = v * (tmf2-tsf2) [Formula 5]
dmfM = v * (tmf3-tsf3) [Formula 6]
dmfC = v * (tmf4-tsf4) [Formula 7]
And dmrBk = v * (tmr1-tsr1) [Formula 8]
dmrY = v * (tmr2-tsr2) [Formula 9]
dmrM = v * (tmr3-tsr3) [Formula 10]
dmrC = v * (tmr4-tsr4) [Formula 11]
From
δemfY = dmfY−dmfBk [Formula 11]
δemfM = dmfM−dmfBk [Formula 12]
δemfC = dmfC−dmfBk [Formula 13]
And δemrY = dmrY−dmrBk [Formula 14]
δemrM = dmrM−dmrBk [Formula 15]
δemrC = dmrC−dmrBk [Formula 16]
Thus, the direction of deviation can be determined from the sign of the calculation result, the writing position is corrected from δemf, and the main scanning width is corrected from δemr-δemf. If there is an error in the main scanning width, the writing position is calculated not only by δemf but also by taking into account the amount of change in the image frequency that has changed with the main scanning width correction.

  FIG. 4 is a diagram for explaining the color misregistration detection means. 41 is a light emitting element, for example, LED. A light receiving element 52 is, for example, a photosensor. Reference numeral 31 denotes a conveyor belt, and 33, 34, 35, and 36 are patterns for color misregistration detection. 43 is light emitted from the light emitting element 41, and 44 is light received by the light receiving element 42 out of reflected light from the conveyor belt 31 or the color misregistration detection pattern 33, 34, 35, 36. The light emitting unit and the light receiving unit are configured by a regular reflection optical system with the conveyance belt 31 as a reflection surface, and color misregistration is caused by a difference in specular reflection reflectance between the conveyance belt 31 and the color misregistration detection pattern, that is, a difference in gloss The position of the detection pattern is detected.

FIG. 5 shows a circuit configuration of the light receiving portion of the detecting means in FIG. The color misregistration detection pattern detected by the light receiving element 42 is converted from current to voltage (I / V conversion), compared with the reference voltage by the comparison unit, and a positive pulse is output during a period when the signal level is lower than the reference voltage. The CPU obtains the center position of each pulse, and further obtains the time difference between the center positions. The amount of color misregistration is calculated from the difference between the obtained time difference and a preset time difference value.
JP 2001-312116 A

  However, in an electrophotographic color image forming apparatus, a model in which a conveyance belt is omitted has been introduced for cost reduction. In such a model, in order to perform conventional color misregistration detection, a color misregistration detection pattern is created on the recording material as an alternative to the conveyor belt. In that case, several problems occur.

  First, the recording material is consumed every time the color misregistration control process is performed. A recording material on which a color misregistration detection pattern that is meaningless to the user is printed is generated each time color misregistration detection processing is performed. It can be easily imagined that this will deteriorate the running cost of the recording material and will also have an adverse effect on the user's mind.

  Second, in order to read the toner image (color misregistration detection pattern) transferred onto the recording material, a color misregistration detection sensor with higher accuracy than before is required. A conventional color misregistration detection sensor detects a gloss difference between a conveyance belt whose surface gloss is controlled and a toner image, and a required detection performance has been clarified. Therefore, it is easy to configure a color misregistration detection sensor at a minimum cost for the required detection performance. However, there are various types of recording materials used by the user, and the surface color and surface gloss are various. As long as the recording material cannot be specified, it is necessary to consider the worst case. In order to be able to detect a color misregistration pattern even when the recording material used by the user and the toner have similar optical characteristics, the detection capability of the color misregistration detection sensor is inevitably required, resulting in a high cost. Will lead to a change.

  The present invention has been made in view of the above-described points, and its object is to provide a color misregistration detection method that is different from the conventional one, thereby eliminating the above-mentioned problems and suppressing the cost of the image forming apparatus. It is an issue.

  In order to solve the above problems, the present invention arranges a distance measuring sensor at a location that causes a color misregistration inside the engine, detects a change in distance in real time, and feeds it back to an image. That is, the present invention is characterized in that, instead of detecting the color misregistration state of the printed image, the variation of the factor causing the color misregistration is detected.

  Furthermore, if further explained, the present invention has solved the above-mentioned problems with the following configuration.

(1) A plurality of photosensitive members, a latent image forming unit that forms an electrostatic latent image on the photosensitive member, a developing unit that develops the electrostatic image into a toner image, and a conveying unit that conveys a recording medium In an electrophotographic multicolor image forming apparatus having transfer means for transferring a toner image to a recording medium and fixing means for fixing the toner image to the recording medium,
Having position detecting means for detecting the relative positions of a plurality of photoconductors;
Information processing means for converting the output from the position detection means into a physical quantity;
A multi-color image forming apparatus comprising means for correcting an image forming position in accordance with the calculated physical quantity.

  As described above, by adopting the configuration of the present invention, it is possible to contribute to resource saving without wasting the recording material. Furthermore, it is not necessary to perform conventional color misregistration correction control such as printing a test pattern and confirming the color misregistration amount, and the waiting time from power-on to first printing is shortened.

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

  FIG. 1 is a diagram illustrating the entire image forming apparatus according to an embodiment of the present invention. In this example, photoconductors 1a to 1d, laser scanner units 2a to 2d, developing devices 3a to 3d, transfer units 4a to 4d, a fixing device 5 and a recording paper cassette 6 are provided.

  The photoreceptors 1a to 1d, the laser scanner units 2a to 2d, and the developing units 3a to 3d correspond to yellow (Y), magenta (M), cyan (C), and black (Bk), respectively, and images from the controller. In accordance with the data, the scanner units 2a to 2d scan the photosensitive drums 1a to 1d to form electrostatic images, which are visualized and developed with toner stored in the developing machines 3a to 3d. The images formed on the respective photosensitive drums are superimposed and transferred onto the conveyed recording paper by the respective transfer units 4a to 4d. Thereafter, the recording paper is conveyed to the fixing device 5, and after the toner is melted by heat, the toner melted by the pressure roller is completely fixed on the recording paper.

  FIG. 6 is a layout view of the distance measuring sensors 7a to 7c in the present embodiment. A distance measuring sensor is installed in each of the developing machines 3a to 3c to measure a distance from an adjacent developing machine. The distance between adjacent developing machines affects the writing position in the sub-scanning direction. In other words, this configuration enables color misregistration correction in the sub-scanning direction.

  FIG. 7 is a diagram showing the configuration of the distance measuring sensor in the present embodiment. Reference numeral 71 denotes a light emitting element, for example, an LED. A light receiving element 72 is, for example, a PSD. The reflected light from the object to be measured is collected on the PSD 72 by the lens 73, and the position of the center of gravity of the collected reflected light changes corresponding to the distance to the object to be measured. Therefore, by processing the output signal from the PSD 72, it is possible to detect the distance to the measurement object.

FIG. 8 shows the relationship between the output signal from the PSD 72 and its position information. When the output from the PSD 72 is I1 and I2, the total length of the PSD 72 is L, and the distance from the center of the PSD 72 to the center of reflected light is x, the following equation is established.
(I1-I2) / (I1 + I2) = 2x / L
The above formula is expressed by a block diagram of an electronic circuit as shown in FIG. The CPU 96 can obtain distance measurement information by A / D converting the output voltage of the division circuit 95. If there is a margin in the A / D conversion port of the CPU 96, the output of the I / V conversion circuit 91/92 may be A / D converted and calculated in the CPU 96.

FIG. 10 shows a sequence diagram in the present embodiment. When processing is started, first, the distance between the developing machines is measured using a distance measuring sensor (S101). It is confirmed whether or not the measurement value at this time is normal (S102). If normal, the process proceeds to the calculation of the correction value. If it is an abnormal value, a measurement error is reported to the user and the process is terminated (S103). The calculation of the correction value uses the following formula. When the theoretical distance between the developing machines is dYM, dMC, dCBk, the actually measured values are dmYM, dmMC, dmCBk, Bk as reference colors, and the correction values for each color are δesY, δesM, δesC, the correction formula is
δesY = (dYM + dMC + dCBk) − (dmYM + dmCMC + dmCBk) [Equation 17]
δesM = (dMC + dCBk) − (dmCMC + dmCBk) [Formula 18]
δesC = (dCBk) − (dmCBk) Equation [19]
(S104). At this time, it is determined whether the calculated value is in an appropriate range (S105). If the value is abnormal, a calculation error report is sent to the user and the process is terminated (S106). If the value is normal, the correction value is used to change the writing position in the sub-scanning direction (S107).

  The description of the same part as in the first embodiment is given the same symbol and the description is omitted.

  FIG. 11 is a layout view of the distance measuring sensor in the main body in the present embodiment. Distance sensors 7a to 7d are installed on the main body frame, and the distances between the adjacent developing machines 3a to 3d are measured. Thereby, the mounting positions of the developing machines 3a to 3d in the main body are determined. After that, by calculating the relative distance between the developing machines, correction control can be performed in the same sequence as in the first embodiment.

  The merit of the configuration of the present embodiment is that it is not necessary to mount a distance measuring sensor on the developing machine, so that the cost of the developing machine as a replacement part can be reduced.

  In addition, the configuration of the distance measurement sensor, the distance measurement method, and the like are the same as in the first embodiment.

  The description of the same parts as those in the first and second embodiments will be given the same symbols, and the description thereof will be omitted.

  FIG. 12 is a diagram illustrating the entire image forming apparatus according to the embodiment of the present invention. In this example, the photosensitive members 1a to 1d, laser scanner units 2a to 2d, developing units 3a to 3d, transfer units 4a to 4d, fixing unit 5, recording paper cassette 6, distance measuring sensors 7a to 7d, laser beam folding mirror 8a. To 8d.

  By arranging the laser beam folding mirrors 8a to 8d between the photoconductors 1a to 1d and the laser scanner units 2a to 2d, it is possible to give flexibility to the arrangement locations of the laser scanner units 2a to 2d. However, in this case, the installation accuracy of the laser beam folding mirrors 8a to 8d becomes a problem. In addition, the position fluctuations of the laser beam folding mirrors 8a to 8d due to the temperature rise in the main body also cause a bad influence on the image.

  Therefore, in order to grasp the positional fluctuation of the laser beam folding mirrors 8a to 8d, distance measuring sensors 7a to 7d are installed on the main body frame, and the distances from the laser beam folding mirrors 8a to 8d are measured. If the position fluctuations of the laser beam folding mirrors 8a to 8d can be grasped, the laser irradiation positions on the photoconductors 1a to 1d can be estimated. Therefore, correction control can be performed in the same sequence as in the first embodiment.

  Other sensor configurations and distance measurement methods are the same as in the first embodiment.

1 is a configuration diagram of a multicolor image forming apparatus according to a first embodiment. FIG. FIG. 3 is an explanatory diagram of color misregistration that occurs in a multicolor image forming apparatus. Explanatory drawing of the color shift detection pattern of a prior art example. The block diagram of the color shift detection means of a prior art example. The block diagram of the light-receiving part circuit of the color shift detection means of a prior art example. FIG. 3 is a layout diagram of distance measuring sensors in the image forming apparatus according to the first embodiment. The block diagram of the ranging sensor of the 1st-3rd Example. Explanatory drawing of the light-receiving part of the ranging sensor of the 1st-3rd Example. The block diagram of the light-receiving part circuit of the ranging sensor of 1st-3rd Example. FIG. 3 is a flowchart of color misregistration correction control according to the first embodiment. FIG. 6 is a layout diagram of distance measuring sensors in the image forming apparatus according to the second embodiment. FIG. 10 is a layout diagram of distance measuring sensors in the image forming apparatus according to the third embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Scanner unit 3 Developing device 4 Transfer part 5 Fixing device 6 Recording paper cassette 7 Distance sensor 8 Folding mirror 71 Distance sensor LED
72 Ranging sensor PSD
73 Distance sensor lens 91 I / V conversion circuit 93 Subtraction circuit 94 Addition circuit 95 Division circuit 96 CPU

Claims (7)

A plurality of photosensitive members, a latent image forming unit that forms an electrostatic latent image on the photosensitive member, a developing unit that develops the electrostatic image into a toner image, a conveying unit that conveys a recording medium, and a recording medium In an electrophotographic multicolor image forming apparatus having a transfer means for transferring a toner image to a recording medium and a fixing means for fixing the toner image to a recording medium.
Having position detecting means for detecting the relative positions of a plurality of photoconductors;
Information processing means for converting the output from the position detection means into a physical quantity;
A multi-color image forming apparatus comprising means for correcting an image forming position in accordance with the calculated physical quantity.   The multicolor image forming apparatus according to claim 1, wherein the position detection unit includes a light emitting element and a position detection element.   The multicolor image forming apparatus according to claim 2, wherein the light emitting element is an LED.   The multicolor image forming apparatus according to claim 2, wherein the position detection element is a PSD.   2. The cartridge system in which the photosensitive member and the developing unit for each color are integrated, and the position detecting unit is built in the cartridge and measures a distance from an adjacent cartridge. 2. A multicolor image forming apparatus according to 1.   The multicolor image forming apparatus according to claim 1, wherein the position detecting unit is installed in a main body frame, and an attachment position can be specified when the cartridge is inserted into the main body. 2. The multicolor image forming apparatus according to claim 1, wherein the latent image forming unit is a laser scanner unit, and a folding mirror is disposed in a laser light path between the latent image forming unit and the photosensitive member.
The position detection means is installed in the main body frame,
Information processing means for measuring the position of the folding mirror and converting the output from the distance measuring means into a physical quantity;
A multi-color image forming apparatus comprising means for correcting an image forming position in accordance with the calculated physical quantity.

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