JP3905995B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, and a printer. More specifically, the present invention relates to an intermediate transfer member to which a toner image formed on an image carrier is transferred, and presses the intermediate transfer member at a predetermined timing. The present invention relates to an image forming apparatus having a pressing member such as a cleaning member that is driven and controlled.
[0002]
[Prior art]
Conventionally, as this type of image forming apparatus, a toner image is formed on an image carrier, and the toner image on the image carrier is superimposed on a transfer surface that moves in one direction along an endless path of an intermediate transfer member. Are known for primary transfer. A toner image composed of the toner image transferred and superimposed on the intermediate transfer member is secondarily transferred onto a recording medium. In such an image forming apparatus, by controlling the speed of the intermediate transfer member, the transfer surface of the intermediate transfer member is moved at a constant speed, and the toner image transferred onto the intermediate transfer member is not misaligned. It did not occur.
[0003]
In the image forming apparatus using the intermediate transfer member, there is a case where a pressing member that is driven and controlled to press the intermediate transfer member at a predetermined timing is provided. For example, the pressing member may be a blade-shaped cleaning member that contacts the transfer surface of the intermediate transfer member after the secondary transfer to the recording medium and removes the toner remaining on the transfer surface for cleaning. In some cases, a roller-shaped transfer member used for applying a transfer bias in a secondary transfer unit that secondary-transfers the toner image on the intermediate transfer member to the recording medium may be provided. When the pressing of the pressing member to the intermediate transfer member is started or the pressing is released, the driving load of the intermediate transfer member changes. Therefore, even if the speed control is performed, the transfer of the intermediate transfer member is performed. The moving speed of the surface changes instantaneously, and the transfer surface is displaced.
[0004]
If a displacement of the transfer surface of the intermediate transfer member occurs during the primary transfer operation, a displacement occurs in the middle of the toner image on the transfer surface. In addition, when transferring a plurality of toner images on the intermediate transfer member in a superimposed manner, if a positional deviation of the transfer surface of the intermediate transfer member occurs between successive primary transfer operations, the transfer surface is transferred to the transfer surface. A positional shift occurs in which the toner images transferred in a superimposed manner are shifted from each other in the transfer surface moving direction.
[0005]
FIG. 4 shows a case where a toner image composed of toner images of four colors of black (Bk), yellow (Y), cyan (C) and magenta (M) is continuously transferred to an intermediate transfer belt 11 as an intermediate transfer member. It is explanatory drawing which illustrated the said position shift in. When a cleaning member as a pressing member is pressed against the transfer surface of the intermediate transfer member at time t1, the moving speed of the transfer surface decreases instantaneously, and the tip of the transfer area on the transfer surface is delayed from a predetermined timing. Will be reached. For this reason, the Bk toner image is transferred to a position shifted from a predetermined position on the transfer surface. Further, when the pressing of the cleaning member is released at time t2, the moving speed of the transfer surface instantaneously increases, and the transfer area on the transfer surface reaches at a predetermined timing. Therefore, the subsequent Y toner image or the like is transferred to a predetermined position on the transfer surface. Accordingly, a positional deviation occurs between the Bk toner image transferred to the transfer surface and the other color toner images.
[0006]
[Problems to be solved by the invention]
In order to prevent the positional deviation of the toner image, it is conceivable that a pressing member such as a cleaning member is not pressed against the intermediate transfer member when the toner image is primarily transferred to the intermediate transfer member. However, in this case, the primary transfer to the intermediate transfer member is not performed unless the pressing (for example, the cleaning operation) of the pressing member is completed. For this reason, it is difficult to improve the image forming speed particularly when the image forming operation is continuously performed.
[0007]
In addition, after the previous toner image is transferred to the intermediate transfer member, until the cleaning member comes into contact with the intermediate transfer member, the registration mark on the intermediate transfer member is detected and the toner image is formed on the image carrier. There is known an image forming apparatus provided with a control unit that is not used as a reference for an operation such as primary transfer to an intermediate transfer member (see, for example, JP-A-9-185214). In this apparatus, the occurrence of positional deviation of the toner image can be prevented, and toner image formation and primary transfer operation can be performed even during a period in which the position of the transfer surface of the intermediate transfer member is displaced due to the pressing of the cleaning member. This is advantageous in terms of improving the image forming speed. However, it is necessary to arrange the cleaning member and the mark sensor for detecting the mark at predetermined positions, which restricts the degree of freedom in the apparatus layout.
[0008]
The problem that it is difficult to simultaneously achieve the prevention of positional deviation of the toner image in the primary transfer and the improvement of the image forming speed and the degree of freedom in the apparatus layout is that the cleaning member This can occur not only when the transfer member is provided, but also when a transfer member such as a transfer bias roller that is driven and controlled to press the transfer surface of the intermediate transfer member at a predetermined timing is provided.
[0009]
The present invention has been made in view of the above problems, and an object of the present invention is to prevent positional deviation of a toner image in primary transfer from an image carrier to an intermediate transfer member, as well as image formation speed and in-apparatus layout. An image forming apparatus capable of improving the degree of freedom is provided.
[0010]
[Means for Solving the Problems]
To achieve the above object, the invention of claim 1 is characterized in that a toner image forming means for forming a toner image on an image carrier and a transfer surface in contact with and opposite to the image carrier in one direction along an endless path. A transferable intermediate transfer member, intermediate transfer member driving means for driving the intermediate transfer member so as to move the transfer surface, and a toner image on the image carrier are sequentially superimposed and transferred onto the intermediate transfer member. A primary transfer unit, a secondary transfer unit that transfers a toner image composed of a toner image superimposed and transferred onto the intermediate transfer member to a recording medium, and a drive that presses the intermediate transfer member at a predetermined timing. In the image forming apparatus provided with the pressing member to be controlled, the intermediate transfer member driving unit drives the intermediate transfer member so as to suppress the displacement when the transfer surface of the intermediate transfer member is displaced. Temporarily change speed With which the position control of the drive of the transfer surface of the intermediate transfer member by a, the pressing Element Increases the drive speed of the intermediate transfer member when the pressing to the intermediate transfer member is started. Element However, when the pressure on the intermediate transfer member is released, the drive speed of the intermediate transfer member is reduced.
[0011]
In this image forming apparatus, the position of the drive of the transfer surface of the intermediate transfer member is controlled so that the transfer surface is driven when the pressing member starts to press or releases the press. Suppress misalignment. Thereby, it is possible to prevent the positional deviation of the toner image in the primary transfer to the intermediate transfer member due to the start and release of the pressing of the pressing member.
[0012]
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the pressing member is a cleaning member that is driven and controlled so as to press the transfer surface of the intermediate transfer member at a predetermined timing. Is.
[0013]
In this image forming apparatus, by controlling the position of the transfer surface of the intermediate transfer member, the transfer surface is moved when the pressing of the cleaning member to the intermediate transfer member is started or when the pressing is released. Suppresses drive misalignment. Thereby, it is possible to prevent the positional deviation of the toner image in the primary transfer to the intermediate transfer member due to the start and release of the pressing of the cleaning member.
[0014]
According to a third aspect of the present invention, in the image forming apparatus of the second aspect, the pressing position of the cleaning member, the transfer position of the primary transfer means, and one or a plurality of toner images that can be formed on the intermediate transfer member When the rear end of the toner image is at the transfer position, it is set between the front end position at which the front end of the portion where the toner image has been formed has reached. Here, in the case where a plurality of toner images are formed side by side on the transfer surface of the intermediate transfer member, the “front end” and “rear end” are the first toner images of the plurality of toner images, respectively. It refers to the leading edge of the projected portion and the trailing edge of the plurality of toner images.
[0015]
In this image forming apparatus, the pressing position of the cleaning member is set between the transfer position of the primary transfer unit and the tip position of the toner image, and the cleaning member is set to the transfer position of the primary transfer unit. Make it possible to place them close together. Therefore, the apparatus can be downsized.
When the cleaning member is brought close to the transfer position of the primary transfer unit in this way, pressing of the cleaning member to the intermediate transfer member is started or released during transfer of the toner image to the intermediate transfer member. However, as described above, it is possible to prevent the positional deviation of the toner image in the primary transfer because the positional deviation in driving the transfer surface of the intermediate transfer member is suppressed.
[0016]
According to a fourth aspect of the present invention, in the image forming apparatus of the first aspect, the pressing member is a transfer member used for the secondary transfer unit, and presses the transfer surface of the intermediate transfer member at a predetermined timing. The transfer member is driven and controlled.
[0017]
In this image forming apparatus, by controlling the position of the transfer surface of the intermediate transfer member, when the secondary transfer unit starts to press the transfer member against the intermediate transfer member or releases the press The positional deviation of the driving of the transfer surface is suppressed. Thereby, it is possible to prevent the positional deviation of the toner image in the primary transfer to the intermediate transfer member due to the start and release of pressing of the transfer member.
[0018]
According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect, the pressing position of the transfer member, the transfer position of the primary transfer means, and one or a plurality of toner images that can be formed on the intermediate transfer member When the rear end of the toner image is at the transfer position, the toner image is set between the front end position at which the front end of the toner image has reached. Here, in the case where a plurality of toner images are formed side by side on the transfer surface of the intermediate transfer member, the “front end” and “rear end” are the front end of the first toner image of the plurality of toner images, respectively. And the trailing edge of the plurality of toner images.
[0019]
In this image forming apparatus, the pressing position of the transfer member is set between the transfer position of the primary transfer unit and the tip position of the toner image, and the transfer member is set to the transfer position of the primary transfer unit. Make it possible to place them close together. Therefore, the apparatus can be downsized.
When the transfer member is brought close to the transfer position of the primary transfer unit in this way, pressing of the transfer member to the intermediate transfer member is started or released during transfer of the toner image to the intermediate transfer member. However, as described above, it is possible to prevent the positional deviation of the toner image in the primary transfer because the positional deviation in driving the transfer surface of the intermediate transfer member is suppressed.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which the present invention is applied to an electrophotographic copying machine (hereinafter referred to as “copying machine”) which is an image forming apparatus will be described.
First, the configuration and operation of the entire copying machine according to the present embodiment will be described. FIG. 1 is a schematic configuration diagram of a copying machine according to the present embodiment. This copier is composed of a color image reading apparatus (hereinafter referred to as “scanner section”) and a color image recording apparatus (hereinafter referred to as “printer section”) (not shown).
[0021]
In the scanner unit, an image of a document placed on a contact glass (not shown) is formed on a color sensor via an illumination / mirror optical system such as an illumination lamp, a mirror group, and a lens, and color image information of the document is obtained. For example, each color separation light of Blue (hereinafter referred to as B), Green (same as G), and Red (same as R) is read and converted into an electrical image signal. The color sensor includes B, G, and R color separation means and a photoelectric conversion element such as a CCD, and can perform simultaneous reading of three colors.
[0022]
The B, G, and R image signals obtained by the scanner unit are subjected to color conversion processing by an image processing unit (not shown) based on the intensity level. By this color conversion processing, color image data of Black (hereinafter referred to as Bk), Yellow (same as Y), Cyan (same as C), and Magenta (same as M) are obtained. Specifically, the illumination / mirror optical system scans a document in response to a start signal linked to the printer unit to obtain color image data. In the present embodiment, since one color image data is obtained for each original scan in the illumination / mirror optical system, four color image data of Bk, Y, C, and M are obtained. In order to obtain this, the above document scanning is repeated four times in total.
[0023]
The printer section is provided with a writing optical unit (not shown) as exposure means and a photosensitive drum 1 as an image carrier. The writing optical unit converts the color image data from the above-described scanner unit into an optical signal, and forms a negative latent image corresponding to the original image on the photosensitive drum 1 that is uniformly charged to a negative polarity. Examples of the writing optical unit include a semiconductor laser, a light emission drive control unit that controls light emission and drive thereof, a polygon mirror, a rotation drive motor that rotationally drives the semiconductor mirror, an f / θ lens, and a reflection mirror. Can be used. The photosensitive drum 1 is driven to rotate in the direction of arrow A in FIG. 1, that is, counterclockwise.
[0024]
Around the photosensitive drum 1, there are a photosensitive member cleaning device 2 as a photosensitive member cleaning unit, a neutralizing lamp (not shown) as a neutralizing unit, a charging charger 3 as a charging unit, and a rotary developing device as a developing unit. A revolver developing unit 4 and an intermediate transfer unit 10 are disposed. The writing optical unit, the charging charger 3, the revolver developing unit 4 and the like constitute toner image forming means for forming a toner image on the photosensitive drum 1.
[0025]
The photoconductor cleaning device 2 includes a fur brush 2a and a photoconductor cleaning blade 2b, and cleans the surface of the photoconductor drum 1 after the primary transfer.
[0026]
The revolver developing unit 4 includes a Bk developing unit 4a, a Y developing unit 4b, a C developing unit 4c, and an M developing unit 4d, and the revolver developing unit rotates so that the photosensitive unit in each color developing unit is rotated. The development position facing the body drum 1 can be positioned. Each of these developing devices includes a developing paddle as a stirring means (not shown) that pumps up and stirs the developer, a toner density detection sensor (not shown) that detects a toner density of the developer, and the developer And a developing sleeve (not shown) as a developer carrying member (not shown) that contacts the surface of the photosensitive drum 1. Note that the internal structures of these four developing units are exactly the same.
[0027]
The intermediate transfer unit 10 includes an intermediate transfer belt 11 serving as an intermediate transfer member, a primary transfer bias roller 12 constituting a primary transfer unit, a primary transfer power source 18 serving as a power source connected thereto, and 1 A ground roller 13 as a pre-transfer neutralization unit, a drive roller 14 constituting an intermediate transfer member drive unit, a tension roller 15, a secondary transfer counter roller 16 constituting a secondary transfer unit, and a cleaning counter roller 17 It has a configuration stretched around. All the rollers that stretch the intermediate transfer belt 11 are made of a conductive material, and the rollers other than the primary transfer bias roller 12 are grounded.
[0028]
FIG. 2 is a block diagram showing a schematic configuration of a motor drive control unit 19 that constitutes an intermediate transfer member driving means together with the driving roller 14. The motor drive control unit 19 includes a drive motor 191, a rotation sensor 192 that detects the rotation of the drive motor, and a position / speed detection that detects the drive position and speed of the intermediate transfer belt based on the output signal of the sensor 192. A circuit 193; a position / speed control circuit 194 that generates a position / speed control signal based on a detection signal from the position / speed detection circuit 193; and a motor drive that drives the drive motor 191 based on the control signal. The circuit 195 is used. In the present embodiment, a DC brushless motor is used as the drive motor 191. And the magnetic pole (S pole, N pole) of the magnet row | line | column attached to the rotation movable part of this motor is detected with the Hall sensor as said rotation sensor 192, and the rotation of this motor is detected. The drive motor and the rotation sensor are not limited to a DC brushless motor or the like as long as the drive position of the intermediate transfer belt 11 can be controlled, and other motors and sensors may be used. .
[0029]
The position / speed control circuit 194 is connected to the control unit 100 of the apparatus main body via an interface circuit 196 so that the moving speed and driving ON / OFF of the intermediate transfer belt 11 are controlled.
[0030]
The primary transfer bias roller 12 that stretches the intermediate transfer belt 11 has a primary transfer area formed by a nip formed by contact between the transfer surface of the intermediate transfer belt and the photosensitive drum 1. The intermediate transfer belt is disposed on the downstream side of the surface movement direction, that is, the belt rotation direction. The primary transfer bias roller 12 is applied with a DC or AC bias, or a DC and AC primary transfer bias that is constant current or constant voltage controlled by the primary transfer power source 18. A grounded earth roller 13 is disposed upstream of the primary transfer area in the belt rotation direction. The intermediate transfer belt 11 is pressed against the photosensitive drum 1 by the primary transfer bias roller 12 and the earth roller 13 to form the nip portion.
[0031]
Around the intermediate transfer belt 11, a cleaning blade 30 as a pressing member that is driven and controlled so as to press the belt 11 at a predetermined timing, and a transfer unit 40 as a secondary transfer unit are arranged. . The transfer unit 40 includes a paper transfer belt 41 as a transfer material carrier, a transfer cleaning blade 42 for cleaning the surface of the paper transfer belt, and the pressing member facing the secondary transfer counter roller 16 of the intermediate transfer unit 10. As a secondary transfer bias roller 43, a secondary transfer power source 47 connected thereto, a first support roller 44a located at an end of the paper feed unit (not shown), and an end of the fixing unit 60 It has a second support roller 44b positioned, a third support roller 44c facing the transfer cleaning blade 42, a transfer paper discharger 45, and a paper transfer belt discharger 46. The transfer unit 40 can be brought into and out of contact with the intermediate transfer belt 11 by a contact and separation mechanism (not shown). When the toner image on the intermediate transfer belt 11 is secondarily transferred to the transfer paper 70 as a recording medium, the first support roller 44a and the secondary transfer bias roller 43 move upward, and the secondary transfer bias is transferred. The roller 43 presses the intermediate transfer belt 11 backed up by the secondary transfer counter roller 16 via the transfer paper 70 and the paper transfer belt 41.
The transfer unit 40 is not limited to this configuration, and for example, a configuration in which a member having another shape such as a drum is used instead of the paper transfer belt 41 may be used.
[0032]
The cleaning blade 30 can be brought into and out of contact with the intermediate transfer belt 11 by a contact and separation mechanism 31. As this contact / separation mechanism, a known contact / separation mechanism using a solenoid or a cam mechanism can be applied. The contact / separation mechanism 31 is controlled by a control unit 100 that performs sequence control of the copying machine. Accordingly, the cleaning blade 30 can be brought into contact with or separated from the intermediate transfer belt 11 at a timing controlled by the control unit 100.
[0033]
Further, in the above-described printer unit, a transfer sheet 70 is further provided in a secondary transfer region formed between the secondary transfer bias roller 43 of the transfer unit 40 and the secondary transfer counter roller 16 of the intermediate transfer belt 11. A feeding unit (not shown) that feeds in, a paper transport unit 50 that transports the transfer paper 70 onto which the toner image has been secondarily transferred by the transfer unit 40, and a fixing that fixes the toner image on the transfer paper 70 transported by the paper transport unit. A fixing unit 60 as a means is also provided.
[0034]
In the copying machine according to the present embodiment, a belt mark used as a reference for an image forming operation such as alignment of a toner image on the intermediate transfer belt 11 is attached to the back surface of the intermediate transfer belt 11 and the mark is detected. A belt mark sensor 32 is provided between the primary transfer bias roller 12 and the driving roller 14. The rotational position information of the intermediate transfer belt 11 detected by the belt mark sensor 32 is input to the control unit 100. The control unit 100 recognizes the rotational position of the intermediate transfer belt 11, and sends a control signal (F) to the writing optical unit. (Gate signal) is output, and the toner image forming operation on the photosensitive drum 1 is started.
[0035]
Next, an example of the image forming operation of the copying machine when the order of development is Bk, Y, C, M will be described. The order of image formation is not limited to this.
[0036]
Before starting the image forming cycle, the photosensitive drum 1 is rotated in the direction of arrow A in FIG. 1, and the charging charger 3 starts corona discharge. Thereby, the surface of the photosensitive drum 1 is uniformly charged to a predetermined potential with a negative charge. The intermediate transfer belt 11 of the intermediate transfer unit 10 is driven at the same speed as the photosensitive drum 1, and rotates in the direction of arrow B in FIG.
[0037]
When the print key is input and the copy operation is started, the belt mark sensor 32 detects the belt mark on the back surface of the intermediate transfer belt 11 and then starts the Bk process. Information is read, and a Bk latent image is formed on the photosensitive drum 1 by the laser beam of the writing optical unit in the printer unit described above based on the Bk image data obtained from the image information. The writing timing by the writing optical unit is controlled by the control unit 100. When the revolver developing unit 4 rotates from the home position, the Bk developing unit 4a moves to the developing position. The negatively charged Bk toner of the Bk developing device 4a adheres to the Bk latent image and develops it to form a Bk toner image. At this time, in order to surely develop the Bk latent image, the developing sleeve of the Bk developing unit 4a is rotated in advance before the tip of the Bk latent image reaches the developing position of the Bk developing unit. As a result, when the leading edge of the Bk latent image reaches the development position, the developer is in a spiked state, so that the entire Bk latent image can be reliably developed.
[0038]
The Bk toner image formed on the photosensitive drum 1 by the Bk developing device 4a is primarily transferred to the surface of the intermediate transfer belt 11 that is driven at a constant speed with the photosensitive drum by the primary transfer electric field in the primary transfer region. . The surface of the photosensitive drum 1 after the primary transfer is cleaned by the photosensitive member cleaning device 2 and is uniformly discharged by the discharging lamp. This completes the Bk process.
[0039]
In parallel with the primary transfer of the Bk toner image, the next Y process is started on the photosensitive drum 1 side. That is, the color image information of the original is read again at a predetermined timing, and the Y latent image is formed on the photosensitive drum 1 by laser light under the control of the control unit 100 based on the Y image data obtained from the image information. Form. Then, the Y latent image is developed by the Y developing device 4b moved to the developing position by the rotation of the revolver developing unit 4 to form a Y toner image. The Y toner image formed on the photosensitive drum 1 by the Y developing unit 4b is aligned with the image surface on which the Bk toner image on the intermediate transfer belt 11 is transferred and is primarily transferred.
[0040]
Thereafter, in the C process and the M process, as in the Y process described above, latent image formation, development, and primary transfer are performed based on the respective image data. In this way, the Bk, Y, C, and M toner images sequentially formed on the photosensitive drum 1 are primarily transferred onto the same image surface on the intermediate transfer belt 11 to thereby perform the intermediate transfer. A toner image in which these four colors overlap is formed on the belt.
[0041]
Since the toner image formed by superimposing the toner images primarily transferred onto the intermediate transfer belt 11 as described above is secondarily transferred onto the transfer paper 70, the above-described 2 is accompanied with the rotation of the intermediate transfer belt. It is sent to the next transfer area. The transfer paper 70 is fed to the secondary transfer area by a registration roller (not shown) at the timing when the leading end of the toner image on the intermediate transfer belt 11 reaches the secondary transfer area. The secondary transfer bias roller 43 of the transfer unit 40 is pressed against the intermediate transfer belt 11 by a transfer contact / separation mechanism (not shown), and the secondary transfer bias roller 43 is pressed against the secondary transfer bias roller 43 by the secondary transfer power source 47. By applying a secondary transfer bias, the toner image on the intermediate transfer belt 11 is secondarily transferred onto the transfer paper 70.
[0042]
As described above, the transfer paper 70 on which the toner image formed by overlapping four colors on the intermediate transfer belt 11 is secondarily transferred is then placed at the portion of the transfer unit 40 that faces the transfer paper neutralization charger 45. Be transported. When passing through the facing portion, the transfer paper 70 is neutralized by the transfer paper neutralization charger 45 in the operating state, and is peeled off from the paper transfer belt 41. The peeled transfer paper 70 is sent by the paper transport unit 50 between the fixing roller pair 61 of the fixing unit 60. In the fixing roller pair 61, the toner image on the transfer paper 70 is melted and fixed in a fixing region including a nip portion formed between the rollers. Then, the transfer paper 70 is carried out and stacked on a copy tray (not shown).
[0043]
Further, after the transfer paper 70 is peeled off, the charge remaining on the surface of the paper transfer belt 41 is neutralized by the paper transfer belt neutralization charger 46. The surface of the paper transfer belt 41 is further cleaned by the transfer cleaning blade 42.
[0044]
When performing repeat copy in the copying machine, the scanner unit proceeds to the Bk process for the first color on the second sheet at a predetermined timing following the M process for the fourth color on the first sheet, and the photosensitive drum in the printer unit. 1 to form a latent image.
[0045]
FIG. 3 shows a change in the speed of the intermediate transfer belt 11 and a drive position shift of the intermediate transfer belt 11 from the M process to the second sheet process, which is the process of the final color of the first sheet in the case of performing the repeat copy. Yes.
In FIG. 3, when the cleaning blade 30 is pressed against the transfer surface of the intermediate transfer belt 11 at time t1 and the driving load increases momentarily, the moving speed of the transfer surface decreases instantaneously. Simultaneously with this decrease in speed, misalignment of the intermediate transfer belt drive tends to occur. However, the drive control unit 19 drives the intermediate transfer belt 11 at a speed faster than the speed Vo before the increase of the drive load. The position control of the belt drive is performed, and the positional deviation of the belt drive is suppressed to about 20 μm or less which does not affect the image quality. Thereafter, the moving speed of the intermediate transfer belt 11 is returned to the speed Vo before the increase of the driving load. By such belt drive position control, the leading end of the transfer area on the transfer surface of the intermediate transfer belt 11 reaches the primary transfer position at a predetermined timing. Accordingly, no positional deviation occurs in the Bk toner image transferred onto the transfer surface.
[0046]
In FIG. 3, when the pressing force of the cleaning blade 30 is released and the driving load is instantaneously reduced at time t2, the moving speed of the transfer surface is instantaneously increased. At the same time as this speed increase, misalignment of the intermediate transfer belt drive tends to occur, but the intermediate transfer belt 11 is driven by the drive control unit 19 at a speed slower than the speed Vo before the drive load increases. The transfer belt drive position control is performed, and the positional deviation of the belt drive is suppressed to about 20 μm or less which does not affect the image quality. Thereafter, the moving speed of the intermediate transfer belt 11 is returned to the speed Vo before the increase of the driving load. By such belt drive position control, even in the subsequent primary transfer of Y, C, and M toner images, the leading end of the transfer area on the transfer surface of the intermediate transfer belt 11 is moved to the primary transfer position at a predetermined timing. Will be reached. Therefore, no positional deviation occurs in each toner image transferred onto the transfer surface.
[0047]
As described above, according to the present exemplary embodiment, the positional shift of the toner image in the primary transfer due to the start and release of the pressing of the cleaning blade 30 is performed by controlling the position of driving of the intermediate transfer belt 11. Can be prevented. In addition, the timing of the primary transfer operation to the intermediate transfer belt 11 can be set regardless of the timing of starting and releasing the pressing of the cleaning blade 11. Therefore, since there is no need to set a waiting time for the primary transfer operation of the toner image for the cleaning operation by the cleaning blade, the image forming speed can be improved and the speed can be increased. In addition, since it is not necessary to define the layout of the belt mark sensor 32 and the cleaning blade 30 in order to prevent the positional deviation of the toner image, the degree of freedom in the apparatus layout can be improved and the apparatus can be easily downsized. become.
[0048]
Further, according to the present embodiment, the change in the moving speed of the intermediate transfer belt 11 accompanying the start of the pressing of the cleaning blade 30 and the release of the pressing is smaller than that in the prior art. Even if the primary transfer operation is performed during a certain period, the positional deviation in each toner image transferred to the transfer surface is reduced.
Further, as shown in FIG. 3, when the primary transfer operation is performed during the speed stabilization period in which the movement speed of the intermediate transfer belt 11 does not change with the start of the pressing of the cleaning blade 30 and the release of the pressing. Thus, it is possible to more reliably prevent the occurrence of positional deviation in each toner image transferred to the transfer surface.
[0049]
In the above-described embodiment, the pressing position of the cleaning blade 30 is determined when the primary transfer position and the trailing edge of the toner image that can be formed on the intermediate transfer belt 11 are in the primary transfer position. It can be set between the tip position where the tip of the formed part has reached. That is, the apparatus can be reduced in size by arranging the cleaning blade 30 closer to the primary transfer position. In such a configuration, the pressing of the cleaning blade 30 to the intermediate transfer belt 11 may be started or released during the transfer of the toner image to the intermediate transfer belt 11, but as described above, Since the positional deviation of the driving of the intermediate transfer belt 11 can be suppressed, the positional deviation of the toner image in the primary transfer can be prevented.
[0050]
Further, in the explanatory diagram of FIG. 3, the case where the driving load of the intermediate transfer belt 11 is changed due to the start of the pressing of the cleaning blade 11 and the release of the pressing has been described. In the secondary transfer operation from the belt 11 to the transfer paper 70, the drive load fluctuation of the intermediate transfer belt 11 also occurs when the secondary transfer bias roller 43 starts to press the intermediate transfer belt 11 and releases the press. . For example, the pressing of the secondary transfer bias roller 43 to the intermediate transfer belt 11 is started during the primary transfer of the M toner image performed prior to the start of the pressing of the cleaning blade 11 in FIG. The pressing of the transfer bias roller 43 is released during the primary transfer of the next Bk toner image.
[0051]
Even when a drive load fluctuation occurs during the secondary transfer operation in this way, the belt drive position shift does not occur due to the drive position control of the intermediate transfer belt 11, so that the secondary transfer bias roller 43 is not displaced. Misalignment of the toner image due to the start of pressing and the release of the pressing can also be prevented.
[0052]
In addition, the timing of the primary transfer operation to the intermediate transfer belt 11 can be set regardless of the timing at which the secondary transfer bias roller 43 is pressed and released. Therefore, since there is no need to set a waiting time for the primary transfer operation of the toner image for the secondary transfer operation by the secondary transfer bias roller 43, the image forming speed can be improved and the speed can be increased. it can. In addition, since it is not necessary to define the layout of the secondary transfer bias roller 43 in order to prevent the positional deviation of the toner image, the degree of freedom in the apparatus layout can be improved, and the apparatus can be easily downsized. .
[0053]
In the above embodiment, as shown in FIG. 3, the belt speed used when the cleaning blade 11 starts to detect the belt mark used as the reference for the second Bk toner image formation and the primary transfer operation is detected. This is done after the fluctuations have subsided. Then, detection of a belt mark used as a reference for the next Y toner image formation and the primary transfer operation is performed after the belt speed fluctuation accompanying the release of the pressing of the cleaning blade 11 is settled. However, in the apparatus of the present embodiment, the belt mark sensor 32 may be arranged so as to detect the belt mark without being influenced by the timing of starting and releasing the pressing of the cleaning blade 11.
[0054]
Further, in the above embodiment, the case where the toner image corresponding to one transfer sheet 70 is transferred and formed on the transfer surface over one circumference of the intermediate transfer belt 11 has been described. This is also applicable to the case where an operation mode (for example, a two-chamfering operation mode) in which toner images corresponding to a plurality of (for example, two) transfer sheets 70 are transferred and formed on the transfer surface over one circumference of the sheet is formed It can be done.
[0055]
In the above embodiment, the case of a copying machine has been described. However, the present invention can also be applied to other image forming apparatuses such as a color printer.
[0056]
【The invention's effect】
Claims 1 to 6 According to the invention, it is possible to prevent the positional deviation of the toner image in the primary transfer to the intermediate transfer member due to the start and release of the pressing of the pressing member to the intermediate transfer member. In addition, the timing of the primary transfer operation to the intermediate transfer member can be set regardless of the timing of the pressing start and release of the pressing member, thereby improving the image forming speed and the degree of freedom in the apparatus layout. There is an effect that can be.
[0057]
In particular, according to the second aspect of the present invention, it is possible to prevent the positional deviation of the toner image in the primary transfer to the intermediate transfer member due to the start and release of the pressing of the cleaning member to the intermediate transfer member. In addition, since the timing of the primary transfer operation to the intermediate transfer member can be set regardless of the timing of the pressing start and release of the cleaning member, the image forming speed and the degree of freedom in the apparatus layout are improved. There is an effect that can be.
[0058]
In particular, according to the invention of claim 3, the cleaning member can be disposed close to the transfer position of the primary transfer means, and the apparatus can be reduced in size.
[0059]
In particular, according to the fourth aspect of the present invention, it is possible to prevent displacement of the toner image in the primary transfer to the intermediate transfer member due to the start and release of the pressing of the transfer member of the secondary transfer unit to the intermediate transfer member. . In addition, the timing of the primary transfer operation to the intermediate transfer member can be set regardless of the timing of starting and releasing the pressing of the transfer member, thereby improving the image forming speed and the degree of freedom in the apparatus layout. There is an effect that can be.
[0060]
In particular, according to the invention of claim 5, the transfer member of the secondary transfer means can be disposed close to the transfer position of the primary transfer means, and there is an effect that the apparatus can be miniaturized.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a main part of a printer unit of a copying machine according to an embodiment of the present invention.
FIG. 2 is a block diagram of an intermediate transfer belt drive control unit in the copier.
FIG. 3 is an explanatory diagram showing a moving speed and a driving position shift of the intermediate transfer belt.
FIG. 4 is an explanatory diagram showing a moving speed and driving position deviation of an intermediate transfer belt in a conventional example.
[Explanation of symbols]
1 Photosensitive drum
2 Photoconductor cleaning device
3 Charger charger
4 Revolver development unit
10 Intermediate transfer unit
11 Intermediate transfer belt
12 Primary transfer bias roller
14 Drive roller
19 Drive control unit
30 Cleaning blade
31 Contact / separation mechanism
32 Belt mark detection sensor
40 Transfer unit
43 Secondary transfer bias roller
50 Paper transport unit
60 fixing unit
70 Transfer paper
100 Control unit
191 Drive motor
192 Rotation sensor
193 Position / speed detection circuit
194 Position / speed control circuit
195 Motor drive circuit
196 Interface circuit

Claims (6)

A toner image forming means for forming a toner image on the image carrier, an intermediate transfer member whose transfer surface in contact with and opposite to the image carrier is movable in one direction along an endless path, and moving the transfer surface An intermediate transfer body driving means for driving the intermediate transfer body, a primary transfer means for sequentially superimposing and transferring the toner image on the image carrier onto the intermediate transfer body, and an overlay on the intermediate transfer body. An image forming apparatus comprising: a secondary transfer unit that transfers a toner image composed of a transferred toner image to a recording medium; and a pressing member that is driven and controlled so as to press the intermediate transfer member at a predetermined timing.
As the intermediate transfer member driving means, when a displacement occurs on the transfer surface of the intermediate transfer member, the intermediate transfer member is driven by temporarily changing the driving speed of the intermediate transfer member so as to suppress the displacement. with which the position control of the drive of the transfer surface, the pressing member is accelerated the drive speed of the intermediate transfer member when starting the press to the intermediate transfer member, the pressing of the pressing pressure member to the intermediate transfer member An image forming apparatus characterized in that, when released, the driving speed of the intermediate transfer member is reduced. The image forming apparatus according to claim 1.
An image forming apparatus, wherein the pressing member is a cleaning member that is driven and controlled so as to press the transfer surface of the intermediate transfer member at a predetermined timing. The image forming apparatus according to claim 2.
The toner image is formed when the pressing position of the cleaning member, the transfer position of the primary transfer means, and the trailing edge of one or more toner images that can be formed on the intermediate transfer member are at the transfer position. An image forming apparatus characterized in that it is set between a tip position at which a tip of a portion that has been reached has reached. The image forming apparatus according to claim 1.
The image forming apparatus, wherein the pressing member is a transfer member used for the secondary transfer unit and is driven and controlled so as to press the transfer surface of the intermediate transfer member at a predetermined timing. . The image forming apparatus according to claim 4.
When the transfer member is pressed, the transfer position of the primary transfer means and the trailing edge of one or more toner images that can be formed on the intermediate transfer member are at the transfer position. An image forming apparatus characterized in that it is set between a leading end position and a reaching end position. The image forming apparatus according to claim 1,
Means for detecting the rotation of the intermediate transfer member, and means for detecting the position and speed of the transfer surface of the intermediate transfer member based on the detection result of the rotation, and based on the detection result of the position and speed. An image forming apparatus that performs the position control.

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