JP2023135065A - Image forming apparatus - Google Patents

Abstract

To adjust a secondary transfer linear velocity and a registration linear velocity to change an amount of secondary transfer nip, thereby reducing density unevenness without a side effect in an image pattern where density unevenness frequently becomes apparent.SOLUTION: A lamination processing apparatus of the present invention comprises: image carriers; an intermediate transfer belt to which toner images carried on the image carriers are primarily transferred; a secondary transfer roller that is in contact with the intermediate transfer belt to form a secondary transfer nip and secondarily transfers the toner images on the intermediate transfer belt to a recording material at the secondary transfer nip; and a registration roller that conveys the recording material to the secondary transfer nip. The secondary transfer linear velocity of the secondary transfer roller and the registration linear velocity of the registration roller can be changed. The lamination processing apparatus calculates an image area ratio in a predetermined area of each page, and changes one or both of the secondary transfer linear velocity and the registration linear velocity according to the image area ratio to change the amount of secondary transfer pre-nip where the recording material and the intermediate transfer belt are in contact with each other on the upstream part of the secondary transfer nip.SELECTED DRAWING: Figure 3

Description

The present invention relates to an image forming apparatus.

2. Description of the Related Art Copying machines, printers, facsimile machines, and the like that utilize electrophotography are well known as image forming apparatuses. In this type of image forming apparatus, after the toner image on the image carrier is primarily transferred to the intermediate transfer belt, the toner image on the intermediate transfer belt is transferred to the registration roller at the transfer nip portion where the transfer roller contacts the intermediate transfer belt. Secondary transfer is performed on the recording material fed out in pairs. The toner image secondarily transferred onto the recording material is then pressurized and heated by a fixing device, thereby fixing the desired image onto the recording material.

Here, in order to prevent image density unevenness and abnormal images due to discharge at the transfer nip portion and to obtain good image quality, techniques for controlling the transfer nip width have been studied and are already in use.

For example, Patent Document 1 discloses a configuration having a contact width changing means for widening the transfer nip width for the purpose of suppressing the occurrence of abnormal images due to electric discharge in the transfer nip. By widening the transfer nip width, a transfer bias can be applied while the image carrier and recording material are in close contact with each other, and abnormal images due to discharge can be prevented.

However, the conventional structure for controlling the transfer nip width, such as that disclosed in Patent Document 1, has a problem in that it increases costs because it includes a mechanism such as a contact width changing means.

Therefore, the present invention provides an image forming apparatus that reduces density unevenness without side effects for image patterns where density unevenness tends to become apparent by adjusting the secondary transfer linear speed and resist linear speed to change the secondary transfer nip amount. The purpose is to provide

This problem consists of an image carrier, an intermediate transfer belt to which the toner image carried on the image carrier is primarily transferred, and an intermediate transfer belt that contacts the intermediate transfer belt to form a secondary transfer nip. An image forming apparatus comprising: a secondary transfer roller that secondarily transfers the above toner image onto a recording material at the secondary transfer nip; and a registration roller that conveys the recording material to the secondary transfer nip; The secondary transfer linear speed of the secondary transfer roller and the registration linear speed of the registration roller can be changed, and the image area ratio in a predetermined area of each page is calculated based on the image data, and the image area ratio is adjusted to the image area ratio. Accordingly, the secondary transfer linear velocity, the resist linear velocity, or both are changed to increase the secondary transfer pre-nip amount at which the recording material and the intermediate transfer belt contact in the upstream portion of the secondary transfer nip. The problem is solved by an image forming apparatus characterized by changing the image forming apparatus.

The image forming apparatus of the present invention adjusts the secondary transfer line speed and resist line speed to change the secondary transfer prenip amount for image patterns (image area ratios) where density unevenness tends to become apparent, thereby eliminating side effects. Density unevenness can be reduced. Furthermore, since no separate complicated mechanism is provided, there is no increase in cost.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. 2 is a block diagram showing the configuration of a control section of the image forming apparatus shown in FIG. 1. FIG. FIG. 2 is a schematic configuration diagram showing an enlarged view of the secondary transfer section in FIG. 1. FIG. 7 is a graph showing the relationship between image area ratio and secondary transfer prenip amount. FIG. 3 is a schematic diagram showing a configuration for calculating an image area ratio during secondary transfer.

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. Further, FIG. 2 is a block diagram showing the configuration of a control section of the image forming apparatus.

As shown in these figures, the image forming apparatus 1 forms an image by fixing a toner image on a sheet of paper, which is an example of a recording material. As shown in FIG. 1, the image forming apparatus 1 includes a control section 10, an image reading section 11, an image forming section 12, a paper feeding section 13, a secondary transfer section 14, a fixing section 15, a paper discharging section 16, and a display/operation section. It has a section 17 and the like.

As shown in FIG. 2, the control unit 10 includes a CPU 1011, a main memory (MEM-P) 1012, a north bridge (NB) 1013, a south bridge (SB) 1014, an AGP bus 1015, an ASIC 1016, and a local memory (MEM-C) 1017. , HD 1018, HDD 1019, and network I/F 102.

The CPU 1011 processes and calculates data according to a program stored in the main memory 1012, and operates an image reading section 11, an image forming section 12, a paper feeding section 13, a secondary transfer section 14, a fixing section 15, and a paper discharging section 16. It is used to control the operation of. The main memory 1012 is a storage area of the control unit 10, and includes a ROM 1012a and a RAM 1012b. The ROM 1012a is a memory for storing programs and data that realize each function of the control unit 10.

The network I/F 102 transmits and receives information to and from external devices such as information processing devices via a communication network. MEM-C1017 is a local memory used as a copy image buffer and code buffer. The HD 1018 is a storage for storing image data, font data used during printing, and forms. The HDD 1019 controls data reading or writing to the HD 1018 under the control of the CPU 1011.

The image reading unit 11 generates image information by optically reading an image written on a sheet of paper. Specifically, image information is read by shining light onto the paper and receiving the reflected light with a reading sensor such as a CCD or CIS. Note that image information is information representing an image to be formed on a recording material such as paper, and is information that represents an image formed on a recording material such as paper, using electrical color separation image signals indicating each color of red (R), green (G), and blue (B). This is what was shown.

The image reading section 11 includes a contact glass 111, a reading sensor 112, and the like, as shown in FIG. The contact glass 111 is used to place a sheet of paper on which an image is written. The reading sensor 112 reads image information of an image written on a sheet of paper placed on the contact glass 111.

The image forming unit 12 attaches toner to the surface of the intermediate transfer belt 143 of the secondary transfer unit 14 based on the image information read by the image reading unit 11 or the image information received by the network I/F 102 to create an image. (toner image).

The image forming unit 12 includes image forming units 120C, 120M, and 120Y that form toner images using cyan (C), magenta (M), yellow (Y), black (K), and clear (T) toners, respectively. , 120K, and 120T.

The image forming unit 120C includes a toner supply section 121C, a photoreceptor drum 122C, a charging section 123C, an exposing section 124C, a developing section 125C, a static eliminating section 126C, and a cleaning section 127C.

The toner supply section 121C stores C color toner and supplies the C color toner to the developing section 125C. A predetermined amount of toner stored in the toner supply section 121C is supplied to the development section 125C by driving a conveying screw within the toner supply section 121C.

The surface of the photosensitive drum 122C, which is an image carrier, is uniformly charged by a charging section 123C, and an electrostatic latent image is formed on the surface by an exposing section 124C based on image information received from the control section 10. be. Further, a toner image is formed on the surface of the photoreceptor drum 122C on which the electrostatic latent image is formed by the developing section 125C attaching toner. Further, the photosensitive drum 122C is provided so as to be in contact with the intermediate transfer belt 143, and is provided so as to rotate in the same direction as the moving direction of the intermediate transfer belt 143 at the point of contact with the intermediate transfer belt 143.

The charging unit 123C uniformly charges the surface of the photoreceptor drum 122C. The exposure section 124C irradiates the surface of the photoreceptor drum 122C charged by the charging section 123C with light based on the dot area ratio of C color determined by the control section 10 to form an electrostatic latent image. The developing section 125C develops the electrostatic latent image formed on the surface of the photoreceptor drum 122C by the exposing section 124C by attaching C color toner stored in the toner supply section 121C, thereby forming a toner image. Form.

The static eliminator 126C removes static from the surface of the photosensitive drum 122C after the image has been transferred to the intermediate transfer belt 143. The cleaning section 127C removes transfer residual toner remaining on the surface of the photoreceptor drum 122C from which electricity has been removed by the electricity removal section 126C.

Note that the image forming units 120M, 120Y, 120K, and 120T have the same configuration as the image forming unit 120C except for the color of the toner, so a description thereof will be omitted.

The paper feed section 13 supplies paper to the secondary transfer section 14 . The paper feed section 13 includes a paper storage section 131 , a paper feed roller 132 , a paper feed belt 133 , and a registration roller 134 .

The paper storage section 131 stores paper, which is an example of a recording material. The paper feed roller 132 is provided to rotate in order to move the paper stored in the paper storage section 131 toward the paper feed belt. The paper feed roller 132 provided in this manner takes out the uppermost paper sheets one by one among the stored paper sheets and places them on the paper feed belt.

The paper feed belt 133 conveys the paper taken out by the paper feed roller 132 to the secondary transfer section 14 . The registration rollers 134 feed out the paper conveyed by the paper feed belt 133 at the timing when a portion of an intermediate transfer belt 143 (described later) on which a toner image is formed reaches the secondary transfer section 14.

The secondary transfer section 14 transfers the image formed on the photoreceptor drum 122 by the image forming section 12 onto the intermediate transfer belt 143 (primary transfer), and transfers the image transferred onto the intermediate transfer belt 143 onto paper (secondary transfer). (next transcription).

The secondary transfer unit 14 includes a drive roller 141, a driven roller 142, an intermediate transfer belt 143, primary transfer rollers 144C, 144M, 144Y, 144K, 144T, a secondary transfer opposing roller 145, and a secondary transfer roller 146.

The driving roller 141 and the driven roller 142 wrap around the intermediate transfer belt 143 . As the drive roller 141 is driven and rotated, the intermediate transfer belt 143 that is stretched around it moves. The driven roller 142 and the driving roller 141 wrap around the intermediate transfer belt 143 . The driven roller 142 rotates as the drive roller 141 rotates and the intermediate transfer belt 143 moves.

The intermediate transfer belt 143 is stretched around a drive roller 141 and a driven roller 142, and moves while contacting the photosensitive drum 122 as the drive roller 141 rotates. As the intermediate transfer belt 143 moves while contacting the photoreceptor drum 122, the image formed on the photoreceptor drum 122 is transferred to the surface of the intermediate transfer belt 143.

The primary transfer rollers 144C, 144M, 144Y, 144K, and 144T are provided to face the photoreceptor drums 122C, 122M, 122Y, 122K, and 122T, respectively, with the intermediate transfer belt 143 in between, and are configured to move the intermediate transfer belt 143. Rotate to . The secondary transfer roller 146 rotates with the intermediate transfer belt 143 and the paper sandwiched between it and the secondary transfer opposing roller 145.

The fixing section 15 fixes the toner transferred to the paper by the secondary transfer section 14. Fixing means welding the resin component of the toner to the paper by applying heat and pressure to the toner at the same time. By performing a fixing process on the toner transferred to the paper by the secondary transfer unit 14, the state of the toner on the paper becomes stable.

The fixing section 15 includes a conveyor belt 151 , a fixing belt 152 , a fixing roller 153 , a fixing belt conveying roller 154 , a fixing opposing roller 155 , and a heat generating section 156 . The conveyance belt 151 conveys the paper onto which the toner has been transferred by the secondary transfer unit 14 toward the fixing roller 153 and the fixing opposing roller 155 . The fixing belt 152 is wrapped around a fixing roller 153 and a fixing belt conveying roller 154, and is moved by rotation of these rollers.

The fixing roller 153 sandwiches the paper conveyed by the conveyor belt 151 with a fixing counter roller 155 installed to face the fixing roller 153, and heats and presses the paper. The fixing belt conveying roller 154 passes the fixing belt 152 together with the fixing roller 153, and as the fixing belt conveying roller 154 rotates, the fixing belt 152 is moved.

The fixing opposing roller 155 is installed to face the fixing roller 153, and sandwiches the conveyed paper between the fixing roller 155 and the fixing roller 153. The heat generating unit 156 is installed inside the fixing roller 153 and generates heat, and heats the paper via the fixing roller 153.

The paper ejection section 16 ejects the paper to which the toner has been fixed by the fixing section 15 from the image forming apparatus 1, and includes a paper ejection belt 161, a paper ejection roller 162, a paper ejection port 163, and a paper storage section 164. are doing.

The paper ejection belt 161 transports the paper that has been fixed by the fixing unit 15 toward the paper ejection port 163 . The paper discharge roller 162 discharges the paper conveyed by the paper discharge belt 161 from the paper discharge port 163 and stores it in the paper storage section 164 .

The display/operation section 17 includes a panel display section 171 and an operation section 172. The panel display section 171 displays setting values, a selection screen, and the like. Further, the panel display section 171 may be a touch panel that receives input from the user. The operation unit 172 is operated by the user for input, such as a numeric keypad for accepting conditions related to image formation and a start key for accepting instructions to start copying.

FIG. 3 is a schematic configuration diagram showing an enlarged view of the secondary transfer section in FIG. 1. As shown in FIG. An image forming apparatus using an intermediate indirect transfer method includes an intermediate transfer belt 143 to which a toner image is primarily transferred, and a secondary transfer nip formed by contacting the intermediate transfer belt 143 to perform secondary transfer of the toner image on the intermediate transfer belt. A secondary transfer roller 146 that performs secondary transfer onto the recording material P at a nip is provided.

Further, a registration roller 134 is provided that is disposed upstream in the conveyance direction of the recording material P with respect to the secondary transfer nip and conveys the recording material P to the secondary transfer nip. The registration rollers 134 convey the recording material P to the secondary transfer section 14 in a well-timed manner, thereby making it possible to secondary transfer the toner image onto the recording material P.

The secondary transfer roller 146 and the registration roller 134 are rotationally driven by a driving means such as a motor so that their linear speed can be changed. Each linear velocity is determined by the conveyance of the recording material P, the image magnification, the torque, etc.

The secondary transfer nip is a secondary transfer roller nip N formed by the secondary transfer roller 146 and the secondary transfer opposing roller 145, and the recording material P and the intermediate transfer belt 143 come into contact with each other at an upstream portion of the secondary transfer nip. It is formed by a secondary transfer prenip Np (secondary transfer nip=secondary transfer roller nip N+secondary transfer prenip Np).

Image density unevenness tends to occur at the secondary transfer prenip Np before entering the secondary transfer roller nip N, and is particularly likely to occur when the length of the secondary transfer prenip Np is short. This is because if the contact length between the intermediate transfer belt 143 and the recording material P is short, the state of close contact between the intermediate transfer belt 143 and the recording material P becomes unstable, and the dots (dot images) are likely to be misaligned.

Therefore, by changing the secondary transfer linear speed of the secondary transfer roller 146 and the registration linear speed of the registration roller 134, the amount of slack in the conveyed recording material P is increased, and the length of the secondary transfer prenip Np ( One possible method is to increase the secondary transfer prenip amount.

However, the linear speed of these rollers is determined by the conveyance performance of the recording material P, the image magnification, and/or the torque of the motor (driving means), etc., and if this condition is maintained constantly, the motor torque will increase, resulting in failure There is a risk of malfunction of the equipment due to malfunction, etc.

On the other hand, depending on the color or image pattern, density unevenness may be easy to become apparent or may be difficult to become obvious. Specifically, in terms of colors, black (K) is likely to be apparent, and yellow (Y) is difficult to be apparent. In image patterns, it is easy to become obvious in the case of halftones, and it is difficult to become obvious in the case of characters or solid images.

Therefore, in this embodiment, the image area ratio in a predetermined area within each page is calculated based on the image data at the time of writing. Then, when that area is secondary transferred, the resist linear speed and secondary transfer linear speed are adjusted for each area within the page so that an appropriate secondary transfer pre-nip amount is achieved according to the image area ratio of that area. control (change). Note that the control unit 10 of the image forming apparatus 1 is responsible for calculating the image area ratio.

Specifically, for image patterns where density unevenness becomes obvious (image area ratio), the secondary transfer linear speed and resist linear speed are adjusted to increase the secondary transfer pre-nip, and for image patterns where density unevenness is difficult to become apparent, the initial settings are left as is. shall be.

The larger the secondary transfer prenip amount is, the stronger the contact between the intermediate transfer belt 143 and the recording material P becomes, and the misalignment of dots (dot images) can be suppressed.

Further, each linear velocity is controlled as follows. The secondary transfer linear speed of the secondary transfer roller 146 is Vt, the resist linear speed of the registration roller 134 is Vr, and the linear speed difference between the secondary transfer linear speed and the resist linear speed is ΔV (=Vr−Vt).

Then, the linear speed difference ΔV at the time of change is made larger than the initially set linear speed difference ΔV, and the secondary transfer prenip amount is increased. Alternatively, the linear velocity difference ΔV at the time of change is made smaller with the initially set linear velocity difference ΔV as the lower limit, and the secondary transfer prenip amount is made smaller.

Note that each linear speed may be controlled by changing the secondary transfer linear speed, the resist linear speed, or both.

In this way, the secondary transfer prenip amount can be changed without providing a separate mechanism, which is advantageous without increasing costs.

FIG. 4 is a graph showing the amount of secondary transfer pre-nip relative to the image area ratio for reducing density unevenness. The horizontal axis of FIG. 4 is the image area ratio (%), and the vertical axis is the degree of the secondary transfer prenip amount (large, medium, small (initial setting value)). This correspondence relationship is plotted on a graph for each of the four toner colors (Y (yellow), M (magenta), C (cyan), and K (black)).

Here, the degree of secondary transfer prenip amount (large, medium, small) is understood to mean that the initial setting is "small" and the secondary transfer prenip amount increases as it becomes "medium" and "large". I want to be

As shown in FIG. 4, when the color of the image is yellow (yellow tone), density unevenness is difficult to become apparent, so the secondary transfer prenip amount is set to "small" (initial setting value). On the other hand, when the color of the image is black (black tone), density unevenness is likely to become apparent, so the secondary transfer prenip amount is set to be large, such as "large" or "medium".

In addition, when the image area ratio is less than 20% (assuming a character image) or greater than 80% (assuming a solid image), density unevenness is difficult to become apparent, so the secondary transfer prenip amount is reduced. Or set it to "small" (initial setting value). On the other hand, when the image area ratio is 20% or more and 80% or less (assuming halftone), density unevenness is likely to become apparent, so the secondary transfer prenip amount is increased.

FIG. 5 is a schematic diagram showing a configuration for calculating the image area ratio during secondary transfer. In FIG. 5, the same parts as those in FIGS. 1 and 3 are given the same reference numerals, and detailed explanation thereof will be omitted.

The area indicated by the broken line on the intermediate transfer belt 143 is a predetermined area S within each page, and the image area of this predetermined area S determines the secondary transfer prenip amount. In this embodiment, the dimensions of the predetermined area S are 330 mm x 25 mm. However, it is not limited to this.

In FIG. 5, the image area ratio of a predetermined area S on the intermediate transfer belt 143 is 30% for magenta (M), 50% for yellow (Y), and 50% for cyan (C) and black (K), respectively. It is 0%.

In this case, as shown in Figure 4, the secondary transfer prenip amount for each color is "medium" for magenta (M), "small (initial setting value)" for yellow (Y), and "small (initial setting value)" for cyan (C) and black. (K) is absent in both cases. Therefore, the "middle" secondary transfer prenip amount is selected in accordance with magenta (M), which has the largest prenip amount.

In this way, by changing the secondary transfer prenip amount depending on the image pattern when the recording material P is secondary transferred, density unevenness can be reduced without any side effects. Furthermore, since the linear velocity (secondary transfer linear velocity Vt, resist linear velocity Vr) is changed only when density unevenness becomes apparent, the load on the motor can be minimized.

The present invention has been described in detail using the embodiments above. This embodiment is an example, and various changes can be made without departing from the scope of the invention.

1 Image forming apparatus 10 Control section 11 Image reading section 12 Image forming section 13 Paper feeding section 14 Secondary transfer section 15 Fixing section 16 Paper discharge section 17 Operation section 111 Contact glass 112 Reading sensor 120 Image forming unit 121 Toner supply section 122 Photosensitive body drum 131 paper storage section 132 paper feed roller 133 paper feed belt 134 registration roller 141 drive roller 142 driven roller 143 intermediate transfer belt 144 primary transfer roller 145 secondary transfer opposing roller 146 secondary transfer roller 151 transport belt 152 fixing belt 153 fixing Roller 154 Fixing belt conveyance roller 155 Fixing opposing roller 156 Heat generating section 161 Paper ejection belt 162 Paper ejection roller 163 Paper ejection port 164 Paper storage section 171 Panel display section 172 Operation section N Secondary transfer roller nip Np Secondary transfer prenip P Recording material S Predetermined area Vt Secondary transfer linear speed Vr Resist linear speed ΔV Linear speed difference

Japanese Patent Application Publication No. 2015-165291

Claims (4)

an image carrier;
an intermediate transfer belt to which the toner image carried on the image carrier is primarily transferred;
a secondary transfer roller that contacts the intermediate transfer belt to form a secondary transfer nip and secondarily transfers the toner image on the intermediate transfer belt to a recording material at the secondary transfer nip;
a registration roller that conveys the recording material to the secondary transfer nip;
An image forming apparatus comprising:
The secondary transfer linear speed of the secondary transfer roller and the registration linear speed of the registration roller are each changeable,
Based on the image data, calculate the image area ratio in a predetermined area of each page,
The secondary transfer linear velocity, the resist linear velocity, or both are changed according to the image area ratio, and the secondary transfer linear velocity, the resist linear velocity, or both are changed so that the recording material and the intermediate transfer belt contact each other at the upstream portion of the secondary transfer nip. An image forming apparatus characterized by changing a next transfer prenip amount. The secondary transfer linear speed is Vt, the resist linear speed is Vr,
Assuming that the linear speed difference between the resist linear speed and the secondary transfer linear speed is ΔV (=Vr−Vt),
increasing the secondary transfer prenip amount by increasing the linear velocity difference ΔV at the time of change than the initial setting linear velocity difference ΔV;
2. The image forming apparatus according to claim 1, wherein the linear velocity difference ΔV at the time of change is made smaller with the initially set linear velocity difference ΔV as a lower limit, thereby reducing the secondary transfer prenip amount. When the image area ratio is less than 20% or greater than 80%,
The image forming apparatus according to claim 1 or 2, wherein the secondary transfer prenip amount is made small. When the image data has a yellow tone, reducing the secondary transfer prenip amount,
3. The image forming apparatus according to claim 1, wherein the secondary transfer prenip amount is increased when the image data has a black tone.

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