JP5495095B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile machine. More specifically, an image formed on the surface of an image carrier is transferred onto a recording material conveyed by the surface movement of a transfer member in a transfer region. The present invention relates to an image forming apparatus.

  In this type of image forming apparatus, an image carrier that moves on the surface and a transfer member that moves on the surface facing the surface of the image carrier, and an image formed on the surface of the image carrier, In the transfer area, there is known a transfer region that is transferred onto a recording material conveyed by the surface movement of a transfer member facing the image carrier. Specifically, for example, a direct transfer type in which an image formed on a latent image carrier (image carrier) such as a photoconductor is directly transferred to a recording material such as recording paper to form an image, or a latent image There are intermediate transfer types that transfer the image formed on the carrier once to an image carrier such as an intermediate transfer member, and finally transfer the image transferred to the image carrier to a recording material to form an image. is there.

In such an image forming apparatus, an image that extends in the recording material conveyance direction (or the image carrier surface movement direction) or a contracted image than the original image may be formed due to various factors. Such expansion / contraction of the image is called a sub-scanning magnification error.
Patent Document 1 discloses an intermediate transfer type image forming apparatus that shifts to a correction operation mode based on the accumulated use time of the image forming means and the number of image formations. In this correction operation mode, a pattern image capable of measuring image expansion / contraction (sub-scanning magnification error) in the intermediate transfer belt surface movement direction is formed on the intermediate transfer belt, and this is read by the sensor on the intermediate transfer belt. Based on the sub-scanning magnification error, an adjustment value for the surface movement speed of the intermediate transfer belt and the rotation speed of the registration roller is calculated. By using this adjustment value to control the surface transfer speed of the intermediate transfer belt and the rotation speed of the registration roller, it is possible to suppress the expansion and contraction of the image that occurs on the intermediate transfer belt. Is suppressed.
Further, Patent Document 2 discloses that one latent image (one page) composed of a plurality of latent image components is formed by sequentially forming a plurality of latent image components on the surface of the rotating photoconductor in the moving direction of the photoconductor. An intermediate transfer type image forming apparatus is disclosed. The image forming apparatus sequentially forms images of a plurality of colors on a single rotating photoconductor, and forms a color image by transferring the images so as to overlap each other on an intermediate transfer belt. In this image forming apparatus, when the rotation load of the intermediate transfer belt at the time of image formation of a certain color is different from the rotation load of the intermediate transfer belt at the time of image formation of another color, The interval (writing magnification) in the photosensitive member surface moving direction is changed according to the difference in rotational load. According to this image forming apparatus, the expansion / contraction of the image generated on the intermediate transfer belt due to the difference between the load when the intermediate transfer belt cleaner is in contact with the intermediate transfer belt and the load when not in contact with the intermediate transfer belt is suppressed. As a result, the sub-scanning magnification error on the recording material is suppressed.

However, as a result of the inventor's research, it has been found that a sub-scanning magnification error that cannot be suppressed by the image forming apparatuses described in Patent Document 1 and Patent Document 2 described above occurs.
Specifically, in the image forming apparatuses described in Patent Document 1 and Patent Document 2 described above, the factors until the image is formed on the intermediate transfer belt (image carrier) (the surface of the intermediate transfer belt) It is possible to suppress the expansion and contraction of the image due to the movement speed fluctuation and the surface movement speed fluctuation of the latent image carrier. However, the expansion and contraction of the image due to the factor that occurs between the time when the image is formed on the intermediate transfer belt (image carrier) and the time when the image is transferred onto the recording material cannot be suppressed. Then, the present inventor found that the difference in speed between the moving speed of the image carried on the surface of the image carrier and the conveying speed of the recording material in the transfer region where the image is transferred from the image carrier to the recording material. I found out that it was a factor.

  That is, in an ordinary image forming apparatus, image formation is performed in a state where there is no speed difference between the moving speed of the image and the conveying speed of the recording material. However, if for some reason the moving speed of the image in the transfer area becomes faster than the transport speed of the recording material, the entire image is moved in the recording material transport direction (or the image carrier surface moving direction) than in the normal state. ) Is formed. Conversely, if for some reason the recording material transport speed in the transfer area is faster than the image movement speed, the image is contracted in the recording material transport direction more than the normal image. It is formed. The following can be considered as this cause. In the transfer area where the image is transferred from the image carrier to the recording material, if the surface movement speed of the transfer member facing the image carrier fluctuates, the conveyance speed of the recording material conveyed by the surface movement of the transfer member also fluctuates. . Therefore, when the surface moving speed of the transfer member varies, a speed difference is generated between the moving speed of the image on the surface of the image carrier in the transfer region and the conveying speed of the recording material. Therefore, the fluctuation in the surface moving speed of the transfer member can cause the above.

  Factors that cause the surface movement speed of the transfer member to fluctuate include, for example, when the transfer member is a transfer roller, fluctuations in the roller length, and when the transfer member is a transfer belt, the roller that stretches the transfer belt The variation of roller warp is mentioned. Such fluctuations in the roller diameter can be caused by environmental fluctuations such as temperature and humidity. Specifically, the case where the transfer member is a transfer roller will be described as an example. When the transfer roller expands due to environmental fluctuations and the roller diameter increases, the surface movement speed of the transfer roller increases, thereby recording. The material transport speed also increases. Conversely, when the transfer roller contracts due to environmental fluctuations and the roller diameter becomes smaller, the surface movement speed of the transfer roller decreases, thereby reducing the conveyance speed of the recording material.

  In the image forming apparatus described in Patent Document 1, not only the surface movement speed of the intermediate transfer belt (image carrier) but also the rotation speed of the registration roller is corrected, but the recording paper conveyance speed in the transfer area is corrected. The surface movement speed of the transfer member is more dominant than the rotation speed of the registration roller. Therefore, if the surface movement speed of the transfer member varies, even if the rotation speed of the registration roller is corrected, the conveyance speed of the recording paper varies, and the movement speed of the image carried on the surface of the intermediate transfer belt in the transfer area And the speed difference between the recording paper transport speed cannot be reduced. Therefore, even the image forming apparatus described in Patent Document 1 cannot suppress the sub-scanning magnification error caused by the change in the surface moving speed of the transfer member.

  The present invention has been made in view of the above problems, and an object thereof is to suppress a sub-scanning magnification error in which the entire image expands or contracts due to fluctuations in the surface movement speed of the transfer member. It is an object to provide a possible image forming apparatus.

In order to achieve the above object, the invention of claim 1 is directed to an image carrier that moves on the surface, a transfer member that moves opposite to the surface of the image carrier, and a drive for moving the surface of the transfer member. Driving force applying means for applying a force to the transfer member, and an image formed on the surface of the image carrier is transferred to a transfer region where the surface of the image carrier and the surface of the transfer member face each other. In the image forming apparatus for transferring onto the recording material conveyed by the surface movement of the transfer member, the surface of the image carrier at a predetermined timing corresponding to the non-image area between the two images during the continuous image forming operation. A pattern image for measuring the amount of expansion and contraction of the image in the recording material conveyance direction is formed, and the image carrier and the transfer member are driven at the same surface moving speed as in the image forming step. Transfer the pattern image to the transfer section A pattern image creating means for creating a pattern image on the surface of the transfer member by transferring to the surface of the transfer member; and a detecting means for detecting the pattern image on the surface of the transfer member created by the pattern image creating means; , The length of the pattern image in the recording material conveyance direction calculated from the detection result of the detection means, and the ideal length of the recording material conveyance direction in an environment assuming that there is no expansion / contraction in the recording material conveyance direction of the pattern image. calculates an error, if the calculated correction range of error is defined in advance, the amount of expansion and contraction in the recording material conveyance direction of the image is small, which is formed by the image forming process in the subsequent times based on the calculated error There line correction processing of the image forming conditions so that, if the calculated error at the correctable range and a correcting means not to perform the correction processing, is the correction processing means Cormorant the correction process are those characterized by comprising a process for changing the surface moving speed of the transfer member.
According to a second aspect of the present invention, in the image forming apparatus of the first aspect, a plurality of single-color images having different colors are superimposed on each other to form a color image on the surface of the image carrier. The pattern image creating means creates a pattern image composed of any one single color image on the surface of the transfer member.
The invention according to claim 3 is the image forming apparatus according to claim 1 or 2, wherein the latent image carrier that moves on the surface, and latent image forming means that forms a latent image on the surface of the latent image carrier that moves on the surface, A developing unit that develops the latent image formed by the latent image forming unit with toner; and a transfer unit that transfers an image obtained by the development by the developing unit to the surface of the image carrier. It is.
According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, the latent image forming means includes a plurality of latent images in the surface moving direction of the latent image carrier with respect to the surface of the latent image carrier. By sequentially forming the image constituent parts, one latent image composed of the plurality of latent image constituent parts is formed, and the correction processing performed by the correction processing means is formed by the latent image forming means. The method includes a process of changing the interval in the moving direction of the surface of the latent image carrier of the plurality of latent image forming units.
According to a fifth aspect of the present invention, in the image forming apparatus of the first aspect, a plurality of latent image constituting portions are sequentially formed in the surface moving direction of the image carrier on the surface of the image carrier that moves on the surface. The latent image forming means for forming one latent image composed of the plurality of latent image forming portions, the developing means for developing the latent image formed by the latent image forming means with toner, and the development by the developing means. Transfer means for transferring the image formed on the recording material, and the correction processing performed by the correction processing means is performed on the surface of the image carrier of the plurality of latent image forming portions formed by the latent image forming means. It includes a process of changing the interval in the moving direction.
According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, the correction processing means is based on a detection result of the detection means before performing the correction processing. When it is determined whether the amount of expansion / contraction in the recording material conveyance direction of the image is within the correctable range, and when it is determined that it is within the correction range, the correction processing is performed, and when it is determined that it is outside the correction range Is characterized in that the correction processing is not performed.
According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the first to sixth aspects of the present invention, the image forming apparatus further includes a temperature detection unit that detects a temperature in the apparatus, and the predetermined timing is determined by the temperature detection. Based on the detection result of the means, it is a timing when the temperature change amount from the initial time during the continuous image formation exceeds a specified amount.

  In the present invention, the image forming condition correction processing for reducing the amount of expansion / contraction in the recording material conveyance direction of the image is based on the detection result of the pattern image obtained by transferring from the surface of the image carrier to the surface of the transfer member. Done. The detection result of the pattern image reflects the expansion and contraction of the image according to the speed difference between the moving speed of the image carried on the surface of the image carrier in the transfer region and the conveyance speed of the recording material. Therefore, the detection result of the pattern image also reflects the expansion / contraction of the entire image (sub-scanning magnification error) caused by the change in the surface moving speed of the transfer member. Therefore, by performing the correction process based on the detection result of the pattern image, it is possible to suppress a sub-scanning magnification error that causes the entire image to expand or contract due to fluctuations in the surface moving speed of the transfer member. .

  As described above, according to the present invention, it is possible to obtain an excellent effect that it is possible to suppress a sub-scanning magnification error in which the entire image is stretched or contracted due to fluctuations in the surface moving speed of the transfer member.

1 is a schematic configuration diagram illustrating a main part of a printer according to an embodiment. 3 is a flowchart showing a flow of a sub-scanning magnification error correction operation in the printer. (A) And (b) is explanatory drawing which shows an example of the pattern for subscanning magnification measurement. It is explanatory drawing which shows an example of the pattern detection sensor for detecting the pattern for the same subscanning magnification measurement. It is explanatory drawing for demonstrating the content of the correction process which correct | amends the surface moving speed of a secondary transfer roller directly. It is explanatory drawing for demonstrating the content of the correction process which correct | amends the writing frequency of an optical writing unit.

Hereinafter, an embodiment in which the present invention is applied to a printer as an image forming apparatus will be described.
Note that the printer according to the present embodiment is a so-called tandem color printer in which four photoconductors that are latent image carriers are arranged along the surface movement direction of an intermediate transfer belt that is an intermediate transfer member as an image carrier. Although it is an image forming apparatus, the present invention is not limited to such an image forming apparatus.

FIG. 1 is a schematic configuration diagram illustrating a main part of the printer according to the present embodiment.
In this printer, four-color single-color images (single-color toner images) respectively formed on the surfaces of the four photoconductors 5, 6, 7, and 8 are superposed on each other on the surface of the intermediate transfer belt 21, thereby forming one page. An image is formed. Electrostatic latent images are formed on the surfaces of the four photoconductors 5, 6, 7, and 8 by optical writing units 1, 2, 3, and 4 as latent image forming means, respectively. The formed electrostatic latent image is conveyed to a developing area facing the developing devices 9, 10, 11 and 12 as developing means as the photosensitive member rotated in the direction of arrow B in the drawing rotates. The electrostatic latent images on the photoconductors 5, 6, 7, and 8 are supplied with toner of each color by the developing devices 9, 10, 11, and 12, and the electrostatic latent images are converted into toner images.

  The four photoconductors 5, 6, 7 and 8 are in contact with the belt flat portion of the intermediate transfer belt 21 stretched around a plurality of support rollers in the surface movement direction (direction of arrow A in the figure). They are arranged side by side. The primary transfer rollers 13, 14, 15, and 16 are opposed to the back side of the intermediate transfer belt at the portion that contacts each photoconductor. Primary transfer high-voltage power supplies 17, 18, 19, and 20 for primary transfer of toner images on 6, 7 and 8 onto the surface of the intermediate transfer belt 21 are connected. Each color toner image formed on the surface of each photoconductor 5, 6, 7, 8 is overlapped with each other on the surface of the intermediate transfer belt 21 by each primary transfer roller 13, 14, 15, 16 so that the intermediate transfer belt can be overlapped. First transferred onto the surface of 21.

  The toner image primarily transferred onto the surface of the intermediate transfer belt 21 is conveyed to the secondary transfer area as the surface of the intermediate transfer belt 21 moves. In the secondary transfer area, a secondary transfer counter roller 22 as a support roller is provided on the back side of the intermediate transfer belt 21, and a secondary transfer roller 23 as a transfer member is provided on the front side of the intermediate transfer belt 21. ing. The secondary transfer roller 23 is rotationally driven by a drive motor M as drive force applying means. Further, the secondary transfer roller 23 is configured to be able to contact and separate from the surface of the intermediate transfer belt 21. As shown in FIG. 1, during the image forming process, the intermediate transfer belt 21 and the secondary transfer roller 23 are in contact with each other, and as a recording material conveyed to the secondary transfer area as indicated by an arrow C in the figure. The sheet 25 passes through the secondary transfer region while being sandwiched between the intermediate transfer belt 21 and the secondary transfer roller 23. At this time, the toner image formed on the surface of the intermediate transfer belt 21 is moved on the surface of the secondary transfer roller 23 by the secondary transfer roller 23 to which a secondary transfer bias is applied by the secondary transfer high-voltage power supply 24. Is secondarily transferred onto the sheet 25 conveyed by the above. The toner image transferred onto the paper 25 is fixed on the paper in a fixing device (not shown) and discharged outside the apparatus.

  In the present embodiment, due to the eccentricity of each of the photoconductors 5, 6, 7, and 8, the surface movement speed of the photoconductor at each latent image writing position varies, thereby generating a sub-scanning magnification error. obtain. Further, due to fluctuations in the surface movement speed of the respective photoconductors 5, 6, 7, 8, fluctuations in the surface movement speed of the intermediate transfer belt 21, etc. Sub-scanning magnification errors can also occur when there is a speed difference between the photosensitive member surface moving speed and the intermediate transfer belt surface moving speed in each primary transfer region. In the present embodiment, the surface moving speed of each of the photoconductors 5, 6, 7, and 8 and the surface moving speed of the intermediate transfer belt 21 are controlled to be constant by a known method. Therefore, in this embodiment, the image on the intermediate transfer belt 21 does not cause image expansion / contraction (sub-scanning magnification error) exceeding the allowable range.

  However, if a speed difference between the moving speed of the toner image (image) carried on the surface of the intermediate transfer belt 21 in the secondary transfer area and the transport speed of the paper 25 occurs, the image on the paper 25 is within an allowable range. A sub-scanning magnification error exceeding 1 can occur. Therefore, in the present embodiment, as will be described later, a pattern image for measuring the sub-scanning magnification error (hereinafter referred to as “sub-scanning magnification error measurement pattern”) is formed on the intermediate transfer belt 21, and two of them are formed. A pattern detection sensor 26 as detection means for detecting a sub-scanning magnification error measurement pattern when transferred onto the surface of the secondary transfer roller 23 is provided on the surface portion of the secondary transfer roller 23 opposite to the secondary transfer region. Oppositely arranged. Then, in order to suppress a sub-scanning magnification error caused by the speed difference between the image moving speed on the surface of the intermediate transfer belt 21 and the paper transport speed in the secondary transfer area, the detection result of the pattern detection sensor 26 is used to Such a correction operation is performed at a predetermined timing.

FIG. 2 is a flowchart showing the flow of the sub-scanning magnification error correction operation in this embodiment.
As described above, the sub-scanning magnification error as described above is caused by an increase in the temperature inside the apparatus, and the secondary transfer roller 23 is expanded and the roller diameter is increased accordingly. That is, when the roller path of the secondary transfer roller 23 increases as the temperature rises, the surface movement speed of the secondary transfer roller 23 increases, thereby increasing the conveyance speed of the paper 25, and therefore the intermediate transfer belt 21 is moved. The transport speed of the paper 25 is relatively increased with respect to the moving speed of the toner image, and an image contracted in the paper transport direction is formed. Therefore, a temperature sensor may be provided as temperature detecting means for detecting the temperature in the apparatus, and the correction operation may be performed at a timing when the temperature detected by the temperature sensor is in a temperature range equal to or higher than a specified value. However, in the present embodiment, in view of the fact that the in-machine temperature greatly increases when image formation is continuously performed, when the amount of temperature change from the initial time during continuous image formation exceeds a specified amount. The correction operation is performed at this timing.

  In the correction operation in the present embodiment, first, a sub-scanning magnification measurement pattern using toner is created on the surface of the intermediate transfer belt 21 by a predetermined process using a configuration used for image formation in a normal image forming process. (S101). Then, a secondary transfer bias is applied to the secondary transfer roller 23 by the secondary transfer high-voltage power supply 24, and the sub-scanning magnification measuring pattern formed on the surface of the intermediate transfer belt 21 is formed on the surface of the secondary transfer roller 23. The pattern is transferred (S102), and the sub-scanning magnification measurement pattern on the surface of the secondary transfer roller 23 is detected by the pattern detection sensor 26 (S103). Thereafter, the secondary transfer roller surface moving direction length (sub-scanning length) of the sub-scan magnification measurement pattern is calculated from the detection result of the pattern detection sensor 26 (S104), and the sub-scan length and the sub-scan magnification error are calculated. The current sub-scanning magnification error is calculated by comparing with the ideal sub-scanning length in the assumed environment (S105). Here, if the sub-scanning magnification error calculated in this way is outside the preliminarily correctable range (No in S106), the correction operation is terminated without performing the correction process. On the other hand, if the calculated sub-scanning magnification error is within a preliminarily correctable range (Yes in S106), correction processing described later is performed (S107).

Details of processing and control executed in each step will be described below.
FIGS. 3A and 3B are explanatory diagrams showing an example of a sub-scanning magnification measurement pattern created in S101.
In S101, as shown in FIG. 3A, the radius of the secondary transfer roller 23 is R, and the effective writing range (image formable range) in the secondary transfer roller axial direction (main scanning direction) is D. 3B, the length in the main scanning direction is D [mm] and the length in the sub scanning direction is L0 = πR [mm] (that is, half the circumference of the secondary transfer roller 23). A scanning magnification measurement pattern 27 is created. The sub-scanning magnification measurement pattern 27 may be created with any one color toner. The sub-scanning magnification measuring pattern 27 is preferably formed on the surface portion of the intermediate transfer belt 21 corresponding to the area between two images during continuous image formation. In this case, it is not necessary to interrupt the continuous image formation to form the sub-scanning magnification measurement pattern 27.

  Even when the surface movement speeds of the intermediate transfer belt 21 and the secondary transfer roller 23 when executing S101 and S102 are the same as those in the normal image forming process, they are individually used for correcting the sub-scanning magnification error. It may be a set speed. In the latter case, speed changing means for changing the surface moving speed of the intermediate transfer belt 21 and the secondary transfer roller 23 is provided, and when performing the correction operation, the intermediate transfer belt 21 and the secondary transfer roller 23 are moved during the image forming process. A pattern for measuring the sub-scanning magnification is created on the surface of the secondary transfer roller 23 while being driven at a surface moving speed different from the above.

FIG. 4 is an explanatory diagram showing an example of the pattern detection sensor 26 used in S103.
As the pattern detection sensor 26 used in S103, an optical sensor or the like that can detect the presence or absence of a toner image on the surface of the secondary transfer roller 23 can be used. When such a sensor is used, the relationship between the output signal of the pattern detection sensor 26 and the sub-scanning magnification measuring pattern 27 transferred onto the surface of the secondary transfer roller 23 is as shown in FIG. At this time, the sub-scanning magnification measurement pattern 27 passes through the detection area of the pattern detection sensor 26 as the surface of the secondary transfer roller 23 moves, so that it is the same as the surface movement speed V of the secondary transfer roller 23. Move at speed. When the leading edge of the sub-scanning magnification measurement pattern 27 reaches the detection area of the pattern detection sensor 26, the output signal of the pattern detection sensor 26 is turned on, and when the trailing edge of the sub-scanning magnification measurement pattern 27 falls off, the pattern detection sensor The output signal 26 is turned off. Therefore, if the time when the output signal of the pattern detection sensor 26 is turned on is T0, and the time when the output signal of the pattern detection sensor 26 is turned off is T1, the sub-transferred onto the secondary transfer roller 23 is performed. The sub-scanning length (measurement sub-scanning length) L1 of the scanning magnification measurement pattern 27 is expressed by the following equation (1).
L1 = (T1-T0) × V (1)

Here, the measurement sub-scanning length L1 of the sub-scanning magnification measurement pattern 27 detected by the pattern detection sensor 26 is the value of the toner image transferred from the surface of the intermediate transfer belt 21 onto the surface of the secondary transfer roller 23. Sub-scan length. For this reason, if there is a difference in surface movement speed between the intermediate transfer belt 21 and the secondary transfer roller 23 in the secondary transfer region, the image is transferred to the secondary transfer roller 23, thereby performing sub-scanning before the secondary transfer. An error occurs in the length (sub-scanning length of the sub-scanning magnification measuring pattern 27 on the surface of the intermediate transfer belt 21). As described above, the diameter of the secondary transfer roller 23 may expand and contract depending on the environment such as temperature and humidity. The surface moving speed V of the secondary transfer roller 23 is expressed by the following equation (2), where ω is the rotational angular speed of the secondary transfer roller 23. Accordingly, the surface moving speed V of the secondary transfer roller 23 increases or decreases depending on the roller diameter of the secondary transfer roller 23. Therefore, fluctuations in the roller diameter cause a difference in surface movement speed between the intermediate transfer belt 21 and the secondary transfer roller 23 in the secondary transfer region.
V = ω × R (2)

The sub-scanning magnification error C calculated in S105 is calculated by sub-scanning length (ideal sub-scanning length) of the sub-scanning magnification measurement pattern in an ideal environment assuming that there is no sub-scanning magnification error, that is, L0 shown in FIG. And the measurement sub-scanning length of the sub-scanning magnification error measurement pattern calculated in S104, that is, L1 shown in FIG. 4, is calculated using the following equation (3).
C = {(L1 / L0) × 100} −100% (3)

  In S106, it is determined whether or not the sub-scanning magnification error C calculated in S105 is a value within the correction range. Here, as an example of determining the correction range of the sub-scanning magnification error, it may be determined in consideration of the speed variable range of the motor that drives the secondary transfer roller 23.

  As the correction process of the sub-scanning magnification error performed in S107, for example, a method of directly correcting the surface moving speed of the secondary transfer roller 23 that causes the sub-scanning magnification to be changed, and the changed sub-scanning magnification are matched. And a method of correcting the writing frequency of the optical writing units 1, 2, 3, and 4 so as to expand and contract the toner image to be formed.

First, the correction process using the former correction method will be described.
FIG. 5 is an explanatory diagram for explaining the contents of the correction processing.
In the description here, an example in which the measured sub-scanning length L1 is longer than the ideal sub-scanning length L0 and a sub-scanning magnification error of + C [%] has occurred will be described. That is, an example in which the roller diameter of the secondary transfer roller 23 expands and the surface movement speed of the secondary transfer roller 23 is faster than the surface movement speed of the intermediate transfer belt 21 will be described. In this example, the surface moving speed of the secondary transfer roller 23 is corrected so that the surface moving speed of the secondary transfer roller 23 is decelerated by an amount corresponding to the sub-scanning magnification error of + C [%]. Specifically, the correction is made so that the surface movement speed of the corrected secondary transfer roller 23 becomes VR1 calculated from the following equation (4). Note that VR0 in the following equation (4) is the surface moving speed of the secondary transfer roller 23 before correction.
VR1 = VR0 + {VR0 × (−C)} (4)
As a result of driving the secondary transfer roller 23 at the corrected surface movement speed VR1, there is no speed difference between the surface movement speed of the secondary transfer roller 23 and the surface movement speed of the intermediate transfer belt 21, and the sub-scanning magnification error C is eliminated. It becomes possible to do.

Next, the correction process using the latter correction method will be described.
FIG. 6 is an explanatory diagram for explaining the contents of the correction processing.
In the description here, the measured sub-scanning length L1 is longer than the ideal sub-scanning length L0, and the sub-scanning magnification error calculated from the sub-scanning magnification error pattern formed at the writing frequency W _f0 [Hz] is + C. An example of [%] will be described. In this example, when the sub-scanning line interval of the toner image formed on the surface of the intermediate transfer belt 21 at the writing frequency W _f0 [Hz] is compared with the sub-scanning line interval after the secondary transfer, The sub-scan line interval is larger. That is, in order to satisfy the target sub-scanning magnification, the writing frequency is low in forming the sub-scanning line interval at the writing frequency W _f0 [Hz]. Therefore, the writing frequency is corrected so that the sub-scanning line interval after the secondary transfer becomes the target interval. Specifically, assuming that one line of sub-scanning is formed in one writing cycle, the corrected writing frequency is corrected to be W _f1 [Hz] calculated by the following equation (5). To do.
W _f1 = W _f0 + (W _f0 × C) (5)
When the sub-scanning magnification error measurement pattern is formed at the corrected writing frequency W _f1 [Hz], the sub-scanning length before the secondary transfer is L0 ′, which is reduced compared to the sub-scanning length L0 before the correction. Since the sub-scanning magnification error before and after the secondary transfer is C%, the sub-scanning length after the secondary transfer is increased by C%. As a result, the sub-scanning length L1 ′ after the secondary transfer of the sub-scanning magnification error measurement pattern formed at the corrected writing frequency W _f1 [Hz] is the second formed at the writing frequency W _f0 [Hz] before the correction. This becomes equal to the sub-scanning length L0 of the sub-scanning magnification measurement pattern before the next transfer, and the sub-scanning magnification error C can be eliminated.

The correction process may be a combination of the former correction method and the latter correction method described above.
In the present embodiment, the case where the timing of performing the correction operation is the timing when the temperature change amount from the initial time during continuous image formation exceeds the specified amount has been described. However, the timing is limited to such timing. Absent. For example, it may be the timing when the user gives an instruction to execute the correction operation to the operation panel as the instruction receiving means.

As described above, the printer according to the present embodiment includes the intermediate transfer belt 21 as the image carrier that moves on the surface, the secondary transfer roller 23 as the transfer member that moves opposite to the surface of the intermediate transfer belt 21, An image (toner image) formed on the surface of the intermediate transfer belt 21, and a drive motor M as drive force applying means for applying a drive force for moving the surface of the secondary transfer roller 23 to the secondary transfer roller 23. Is transferred onto a sheet 25 as a recording material conveyed by the surface movement of the secondary transfer roller 23 in a secondary transfer region where the surface of the intermediate transfer belt 21 and the surface of the secondary transfer roller 23 face each other. Forming device. The printer forms a sub-scanning magnification measuring pattern as a pattern image on the surface of the intermediate transfer belt 21 at a predetermined timing, and transfers the sub-scanning magnification measuring pattern onto the surface of the secondary transfer roller 23. As a pattern image creating means for creating a sub-scanning magnification measuring pattern on the surface of the secondary transfer roller 23, an optical writing device or a developing device used for forming a toner image in a normal image forming process is used. In addition, the printer performs the next time based on the pattern detection sensor 26 as a detection unit for detecting the sub-scanning magnification measurement pattern on the surface of the created secondary transfer roller 23, and the detection result of the pattern detection sensor 26. Correction of image forming conditions such as the surface moving speed of the secondary transfer roller 23 and the sub-scanning line interval so that the amount of expansion / contraction in the paper transport direction (sub-scanning direction) of the image formed in the subsequent image forming process is reduced. A control unit (not shown) is provided as correction processing means for performing processing. With such a configuration, it is possible to suppress the sub-scanning magnification error caused by the conveyance speed variation of the paper 25 due to the roller variation of the secondary transfer roller 23, and the roller variation of the secondary transfer roller 23 varies. It is possible to maintain a constant image quality even in an environment.
Further, according to the present embodiment, the sub-scanning magnification measurement pattern is formed on the surface of the secondary transfer roller 23 while the intermediate transfer belt 21 and the secondary transfer roller 23 are driven at the same surface moving speed as that in the image forming process. Create This eliminates the need for speed changing means for setting the intermediate transfer belt 21 and the secondary transfer roller 23 to surface movement speeds different from those during the image forming process.
On the other hand, speed changing means for changing the surface moving speed of the intermediate transfer belt 21 and the secondary transfer roller 23 is provided, and the intermediate transfer belt 21 and the secondary transfer roller 23 are driven at a surface moving speed different from that in the image forming process. In this state, a sub-scanning magnification measuring pattern may be created on the surface of the secondary transfer roller 23. In this case, since the surface movement speed suitable for detecting the sub-scanning magnification error can be adopted as the surface movement speed of the intermediate transfer belt 21 and the secondary transfer roller 23 during the correction operation, a more accurate sub-scanning magnification error can be obtained. It becomes possible to detect.
The printer according to this embodiment is an image forming apparatus that forms a color image on the surface of the intermediate transfer belt 21 by superimposing a plurality of single-color images having different colors. In this embodiment, a sub-scanning magnification measurement pattern including any one single color image is created on the surface of the secondary transfer roller 23 during the correction operation. As a result, wasteful consumption of toner can be suppressed as compared to the case of creating a sub-scanning magnification measurement pattern composed of images of a plurality of colors.
In the present embodiment, as the correction process, a process of changing the surface moving speed of the secondary transfer roller 23 is performed. Thereby, it is possible to directly correct the secondary transfer roller 23 which is a factor of the sub-scanning magnification error.
The printer according to this embodiment forms latent images on the surfaces of the photosensitive members 5, 6, 7, and 8 serving as latent image carriers that move on the surface and the photosensitive members 5, 6, 7, and 8 that move on the surface. Optical writing units 1, 2, 3, and 4 as latent image forming means, and developing devices 9, 10, and as developing means for developing the latent image formed by the optical writing units 1, 2, 3, and 4 with toner. 11 and 12 and primary transfer rollers 13, 14, 15, and 16 as transfer means for transferring an image obtained by development by the developing devices 9, 10, 11, and 12 to the surface of the intermediate transfer belt 21. Yes. The optical writing units 1, 2, 3, and 4 have a plurality of latent image forming units (sub-scanning lines) in the direction of movement of the photoreceptor surface with respect to the surfaces of the photoreceptors 5, 6, 7, and 8 that move on the surface. By forming sequentially, a latent image composed of the plurality of latent image components is formed, and the correction processing is performed by the plurality of latent images formed by the optical writing units 1, 2, 3, and 4. A process of changing the interval (sub-scan line interval) in the moving direction of the photosensitive member surface of the component is performed. In the correction process for changing the surface moving speed of the secondary transfer roller 23, the correctable range may be limited to the changeable range of the surface moving speed of the secondary transfer roller 23. If the correction process changes the sub-scanning line interval, the correction can be performed without being limited to the changeable range of the surface moving speed of the secondary transfer roller 23.
In this embodiment, the intermediate transfer type image forming apparatus has been described. However, the same applies to the direct transfer type image forming apparatus. Specifically, a latent image composed of a plurality of latent image components is formed by sequentially forming a plurality of latent image components (sub-scanning lines) in the direction of movement of the surface of the photoconductor on the surface of the photoconductor that moves. Image forming means, a developing means for developing the latent image formed by the latent image forming means with toner, and a transfer means for transferring an image obtained by development by the developing means onto a recording material Device. Also in such an image forming apparatus, as the correction process, a process of changing the interval (sub-scanning line interval) in the moving direction of the photosensitive member surface of the plurality of latent image forming units formed by the latent image forming unit can be adopted.
In the present embodiment, before performing the correction process, it is possible to determine whether or not the amount of expansion / contraction of the image in the paper conveyance direction is within the correctable range based on the detection result of the pattern detection sensor 26. If it is determined that the value is within the range, the correction process is performed. If it is determined that the value is outside the correctable range, the correction process is not performed. As a result, when it is determined that it is out of the correctable range, it is possible to perform a processing operation such as a maintenance process assuming that the secondary transfer roller 23 has reached the end of its life without performing a correction process.
In the present embodiment, a temperature sensor is provided as a temperature detecting means for detecting the temperature in the apparatus. Based on the detection result of the temperature sensor, the amount of temperature change from the initial stage during continuous image formation is a predetermined amount. The correction operation is performed at the timing when the time is exceeded. This makes it possible to maintain the quality of all images formed during continuous image formation.
In this embodiment, when the timing for executing the correction operation during continuous image formation comes, the sub-scanning magnification is applied to the surface portion of the intermediate transfer belt 21 corresponding to the area between the two images during the continuous image formation. By forming a measurement pattern and transferring the sub-scan magnification measurement pattern onto the surface of the secondary transfer roller 23, a sub-scan magnification measurement pattern is created on the surface of the secondary transfer roller 23. Thereby, it is not necessary to interrupt the continuous image formation in order to form the sub-scanning magnification measurement pattern 27.
As described above, an operation panel serving as an instruction receiving unit that receives an instruction to execute a correction operation by a user may be provided, and the correction operation may be performed at a timing when the operation panel receives the execution instruction. In this case, the correction operation can be performed at a time according to the user's desire.

1, 2, 3, 4 Optical writing unit 5, 6, 7, 8 Photoconductor 9, 10, 11, 12 Developing device 13, 14, 15, 16 Primary transfer roller 21 Intermediate transfer belt 23 Secondary transfer roller 25 Paper 26 Pattern detection sensor 27 Sub-scanning magnification measurement pattern

JP 2004-294514 A JP 2006-039268 A

Claims (7)

An image carrier that moves on the surface, a transfer member that moves on the surface opposite to the surface of the image carrier, and a driving force applying unit that applies a driving force for moving the surface of the transfer member to the transfer member. ,
The image formed on the surface of the image carrier is transferred onto a recording material conveyed by the surface movement of the transfer member in a transfer region where the surface of the image carrier and the surface of the transfer member face each other. In the image forming apparatus to
Formed at a predetermined timing corresponding to the non-image area between the two images during continuous image forming operation, on the surface of the image carrier, the pattern image for measuring the expansion and contraction amount in the recording material conveyance direction of the image Then, the pattern image is transferred onto the surface of the transfer member while the image carrier and the transfer member are driven at the same surface moving speed as in the image forming step, whereby a pattern is formed on the surface of the transfer member. Pattern image creating means for creating an image;
Detecting means for detecting a pattern image on the surface of the transfer member created by the pattern image creating means;
An error between the recording material conveyance direction length of the pattern image calculated from the detection result of the detection means and the ideal recording material conveyance direction length in an environment assuming that the pattern image does not expand or contract in the recording material conveyance direction. calculates, if the calculated correction range of error is defined in advance, the amount of expansion and contraction in the recording material conveyance direction of the image formed by the image forming process in the subsequent time is reduced on the basis of the calculated error the stomach line correction processing of the image forming conditions, the calculated error and a correction processing unit does not perform the correction processing if the correctable range as,
The image forming apparatus according to claim 1, wherein the correction processing performed by the correction processing unit includes a process of changing a surface moving speed of the transfer member. The image forming apparatus according to claim 1.
A plurality of monochrome images having different colors are superimposed on each other to form a color image on the surface of the image carrier,
The image forming apparatus, wherein the pattern image creating means creates a pattern image composed of any one single color image on the surface of the transfer member. The image forming apparatus according to claim 1 or 2,
A latent image carrier that moves on the surface;
Latent image forming means for forming a latent image on the surface of the latent image carrier that moves on the surface;
Developing means for developing the latent image formed by the latent image forming means with toner;
An image forming apparatus comprising: transfer means for transferring an image obtained by development by the developing means to the surface of the image carrier. The image forming apparatus according to claim 3.
The latent image forming means sequentially forms a plurality of latent image constituting portions in the surface moving direction of the latent image carrying body on the surface of the latent image carrying body moving on the surface, thereby from the plurality of latent image constituting portions. A latent image is formed,
The correction processing performed by the correction processing unit includes a process of changing intervals in the moving direction of the latent image carrier surface of the plurality of latent image forming units formed by the latent image forming unit. apparatus. The image forming apparatus according to claim 1.
A plurality of latent image constituent portions are sequentially formed in the surface moving direction of the image carrier on the surface of the image carrier that moves on the surface, thereby forming one latent image composed of the plurality of latent image constituent portions. Latent image forming means;
Developing means for developing the latent image formed by the latent image forming means with toner;
Transfer means for transferring an image obtained by development by the developing means onto the recording material,
The correction process performed by the correction processing unit includes a process of changing intervals in the moving direction of the image carrier surface of the plurality of latent image forming units formed by the latent image forming unit. . The image forming apparatus according to any one of claims 1 to 5,
Before performing the correction process, the correction processing unit determines whether the amount of expansion / contraction in the recording material conveyance direction of the image is within a correctable range based on the detection result of the detection unit, and is within the correction range. An image forming apparatus that performs the correction process when it is determined that the image is out of the correction range, and does not perform the correction process when it is determined that the image is out of the correction range. The image forming apparatus according to any one of claims 1 to 6,
Having temperature detection means for detecting the temperature inside the device,
2. The image forming apparatus according to claim 1, wherein the predetermined timing is a timing when a temperature change amount from an initial time during continuous image formation exceeds a specified amount based on a detection result of the temperature detecting means.

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