JP4537672B2 - Image forming apparatus - Google Patents

Description

[0001]
[Technical field to which the invention belongs]
The present invention relates to an image forming method and an image forming apparatus, and more particularly to a transfer material separating method and structure at a transfer position.
[0002]
[Prior art]
In an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a printing machine, an image formed in an image forming processing unit can be transferred to a transfer material such as a transfer sheet to obtain a recording output.
[0003]
The image subjected to the visible image processing in the image forming processing unit is subjected to a transfer process for transferring from an image carrier such as a photoconductor to a transfer material.
The transfer device used in the transfer process has a structure having a function of separating a transfer material after transfer in addition to electrostatic transfer of a visible image, and one of the structures is a corona transfer separation system.
In the above system, the toner on the image carrier is electrostatically transferred from the back side of the transfer material in close contact with the image carrier to the transfer agent by a transfer corona discharger, and the transfer material after transfer is separated by a claw, etc. It is known that the image carrier is separated from the image carrier by mechanical forced separation using AC or AC neutralization separation (for example, Non-Patent Document 1).
[0004]
On the other hand, instead of bringing the transfer material into close contact with the image carrier, a contact type transfer system in which the toner on the image carrier is transferred to the transfer material while the transfer material is electrostatically conveyed by a belt to which a transfer bias is applied by a bias power source. Is also known (for example, Patent Document 1).
[0005]
Further, instead of bringing the transfer material into contact with or in close contact with the image carrier, the visible image formed on the image carrier itself is temporarily transferred to an intermediate transfer means such as a belt, and then the primary transfer position in the intermediate transfer means. There is a method in which a visible image from an image carrier transferred to an intermediate transfer unit is transferred to a transfer material at a secondary transfer position corresponding to a position different from the secondary transfer position (for example, Patent Document 2).
[0006]
By the way, when performing electrostatic transfer, the resistance characteristic of the transfer material becomes a problem. In other words, when a material that easily contains moisture, such as paper, is used as the transfer material, the resistance characteristics change due to the moisture content of the transfer material changing depending on the humidity at the transfer position atmosphere or at the storage position of the transfer material, The action of electrostatic force (electrostatic polarization action) may not be exhibited effectively, and separation from the photoreceptor by electrostatic transfer or electrostatic adsorption may not be performed satisfactorily.
[0007]
Conventionally, by changing the setting timing of the transfer bias to the transfer material according to the environmental humidity, it is possible to prevent charge leakage from the transfer material at high humidity and to use the belt curvature by electrostatic adsorption. The structure which improved the separability which has been proposed is proposed (for example, patent document 1, 2, 3, 4).
[0008]
[Non-Patent Document 1]
The Electrophotographic Society of Japan "Basics and Applications of Electrophotographic Technology" P229-230 (1997.6.20 issued by Corona Co., Ltd.)
[Patent Document 1]
JP-A-5-94099 (paragraph "0022" column)
[Patent Document 2]
JP-A-6-167896 (paragraph “0068” column)
[Patent Document 3]
JP 2002-196596 A ("Claim 1")
[Patent Document 4]
JP 2000-227745 A ("Claim 1")
[0009]
[Problems to be solved by the invention]
As disclosed in each of the above-mentioned patent documents, the electrostatic characteristics are different from the initial stage due to the change in charging conditions due to the change in the resistance characteristics of the transfer material due to humidity, and the separation characteristics of the transfer material are deteriorated. The method of switching the transfer bias timing to the transfer material is effective when the transfer material is relatively thick.
However, in the case of a transfer material with low stiffness, for example, a thin transfer material with low bending rigidity, the electrostatic property of the transfer material can be improved by changing the timing alone because the capacitance affected by the thickness is small. Since the same conditions as in the thick case cannot be obtained, the separation characteristics may not be improved. Further, such a weak transfer material may affect not only the thickness but also the material.
[0010]
An object of the present invention, the conventional image forming method, in particular, transfer and in view of the problems in the separation step, the paper quality, in particular the bending images formed that can so as not to exacerbate the separation characteristics independent of humidity even if the stiffness is different To provide an apparatus.
[0011]
[Means for Solving the Problems]
The invention according to claim 1 includes an image carrier on which a toner image is formed on the surface, a transfer belt that abuts on the image carrier, a contact condition changing unit, and an environmental sensor that detects humidity. The contact condition changing means is provided at a position where the transfer belt and the image carrier are not opposed to each other and at a position outside the transfer belt, and when the humidity detected by the environmental sensor is equal to or higher than a threshold value, The width of the transfer nip portion corresponding to the region in contact with the belt is widened , and the transfer nip width for the front end portion of the transfer material is made smaller than the transfer nip width for the region other than the front end portion. It is characterized by that.
The invention according to claim 2 comprises an image carrier on which a toner image is formed on the surface, a transfer belt that abuts on the image carrier, a contact condition changing means, and an environmental sensor that detects humidity, The contact condition changing means is provided at a position where the transfer belt and the image carrier are not opposed to each other and at a position outside the transfer belt, and when the humidity detected by the environmental sensor is equal to or higher than a threshold value, The width of the transfer nip portion corresponding to the area where the belt is in contact with is widened, and the width of the transfer nip portion is equivalent to the area where the image carrier and the transfer belt are in contact with each other. In the first period until the center position is reached, the second period after the period is changed to be smaller .
[0012]
The invention according to claim 3 is characterized in that the transfer belt can be brought into contact with and separated from the image carrier by swinging the transfer belt by the contact condition changing means.
[0013]
According to a fourth aspect of the present invention, the transfer belt is wound around the drive roller and the driven roller, and the contact condition changing means is on the opposite side of the transfer nip portion across the driven roller on the transfer belt. It is characterized by that.
[0014]
The invention according to claim 5 is characterized in that the contact condition changing means swings the driven roller side with the driving roller side as a fulcrum.
[0015]
According to a sixth aspect of the present invention, the environmental sensor is provided for each storage position when a plurality of storage positions for the transfer material are provided.
[0016]
The invention described in claim 7 is characterized in that the environmental sensor is provided between the transfer material storage position and the transfer position.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram illustrating a configuration of an image forming apparatus to which an image forming method according to an embodiment of the present invention is applied. FIG. 1 illustrates a configuration related to image transfer onto a transfer material in the image forming apparatus. It is shown.
At the transfer position, there is provided a transfer device 101 for transferring the transfer material S in contact with the photosensitive member 100 which is one of the image carriers.
[0018]
The transfer device 101 includes a transfer belt 104 wound around a driving roller 102 and a driven roller 103.
In the transfer device 101, a transfer belt 104 is disposed in a housing 101A, and a belt cleaning device 105 and a belt contact / separation device 106 are provided in the housing 101A.
[0019]
The belt cleaning device 105 is provided to remove toner, paper dust, and the like adhering to the transfer belt 104. The cleaning blade 105A that contacts the transfer belt 104, and the transfer belt 104 at a position before contacting the cleaning blade 105A. A cleaning bias roller 105B for removing electricity, a bias roller cleaning blade 105C, and a toner collecting coil 105D for recycling and collecting the collected toner are provided.
[0020]
In FIG. 1, a charging device, a writing device, a developing device, and a cleaning device that performs cleaning after transfer are arranged on the periphery of the photoconductor, although not shown. In the image forming apparatus, except for the writing device, the devices arranged around the photoconductor 100 are collected and housed in a process cartridge and detachably mounted on the image forming apparatus. In FIG. 1, reference numeral 107 denotes a transfer bias roller connected to a power source (not shown).
[0021]
The transfer belt 104 in the transfer device 101 is provided so as to be able to come into contact with and separate from the photoreceptor 100, and includes a belt contact / separation device 106 described below as a configuration for that purpose.
The belt contact / separation device 106 can change the contact state while bringing the driven side of the transfer belt 104 into contact with and separating from the photosensitive member 100 with the drive roller 102 side as a fulcrum. as a direction swingable a push lever 106A for contacting and separating the photosensitive member 100 by lifting the driven roller 10 3 side of the transfer belt 104, the swing amount in contact with one swinging end of the push-up lever 106A Is provided with a transfer contact / separation cam 106B.
The transfer contact / separation cam 106B is set by a stepping motor whose rotation is controlled by a main control unit 107 that executes control related to image forming processing, which will be described later.
[0022]
FIG. 2 is a block diagram for explaining the control configuration. In FIG. 2, the main control unit 107 includes a CPU 107A, a ROM 107B, a RAM 107C input circuit 108, a load driver 109, and an interface 110. A motor 112 and a humidity sensor 113 are connected.
The stepping motor 112 is a drive source of the transfer contact / separation cam 106B shown in FIG. 1, and the humidity sensor 113 is disposed at the transfer material storage position and is one of the environmental conditions in the storage unit or the feeding unit. It is a sensor that detects a certain humidity, and humidity data is output to the input circuit 108.
The humidity data is used to set contact / separation conditions of the transfer belt 104 with respect to the photosensitive member 100, that is, contact conditions. That is, in the present embodiment, the humidity data is compared based on the relative humidity of 70% corresponding to a preset threshold value in the CPU 107A, and if the comparison result is 70% or more which is the threshold value, the load driver 109 is used. By driving the stepping motor 112, the contact condition of the transfer belt 104 with respect to the photoreceptor 100 is changed. That is, when the stepping motor 112 is driven, the push-up lever 106 is pushed up by the transfer contact / separation cam 106B to enlarge the region where the transfer belt 104 contacts the photosensitive member 100 side. In other words, the width of the transfer nip portion corresponding to the region where the transfer belt 104 contacts the photoconductor 100 is changed.
[0023]
In the present embodiment, the following setting is used as the rotation amount of the transfer contact / separation cam 106B by the stepping motor 112, in other words, the contact amount of the transfer belt 104 on the transfer material entrance side with respect to the photoreceptor 100.
A region where the transfer material is nipped and conveyed by the photoreceptor 100 and the transfer belt 104 is configured as a transfer nip portion, and the width of the transfer nip portion reaches the center position of the transfer nip portion. Until the trailing edge of the transfer material passes through the center of the transfer nip after the leading edge of the transfer material passes through the center of the transfer nip (meaning the center in the transfer material passage direction) The transfer nip width is made different in this period, and the former, that is, the period until the leading edge of the transfer material reaches the center of the transfer nip is set to be smaller than the subsequent period. . Actually, the transfer nip width in the period until the leading edge of the transfer material passes through the transfer nip is 6 mm, and the transfer nip width in the subsequent period is 8 mm. The subsequent period corresponds to a transfer area where the image is transferred to the transfer material.
[0024]
In the present embodiment, the following operation can be obtained by using the above configuration.
When the humidity, which is an environmental condition detected by the humidity sensor 113, is higher than the relative humidity of 70%, which is a threshold set in the CPU 106A, the stepping motor 112 is driven to rotate so that the transfer belt 104 contacts the photoconductor 100. The contact condition is changed, and the transfer nip width until the leading edge of the transfer material reaches the center of the transfer nip portion with respect to the transfer nip width is made smaller than the period after this. For this reason, the front end side of the transfer material is reduced when the period during which the transfer bias acts is shortened, so that the electrostatic attraction force to the photoconductor 100 is lowered, and is generated when the electroadhesion is performed on the photoconductor 100 side. Separation defects are easily suppressed.
[0025]
On the other hand, the transfer nip width is increased in the period after the leading edge of the transfer material passes through the center of the transfer nip portion, so that a decrease in transfer efficiency is suppressed. In short, since it is poor separation that the front end of the transfer material moves with the photoconductor 100 while adhering to the photoconductor 100, it is important to prevent the front end of the transfer material from adhering to the photoconductor 100. Therefore, the transfer nip width that affects the charged state at the leading edge of the transfer material is controlled. Since it is important to define the transfer nip width with respect to the front end of the transfer material, it is possible to make the transfer width the same as the front end portion in the region after the front end passes through the center of the transfer nip portion.
[0026]
According to the present embodiment, even when a transfer material having a low waist and having a property of being easily attached to the photoconductor 100 is used, the tip can be easily separated from the photoconductor 100 without being affected by humidity, in other words, By setting the state where it is difficult to adhere to the photoreceptor, it is possible to prevent the separation characteristics from deteriorating.
The inventor conducted an experiment on the separation characteristics based on the relationship between the waist strength of the transfer material and the transfer nip width in a high-temperature and high-humidity environment where the relative humidity corresponding to the threshold is 70% or more, and obtained the results shown in FIG. It was.
The result of this experiment is that the transfer nip width that is set when the leading edge of the transfer material passes through the center of the transfer nip is small and the separation characteristics deteriorate without being affected by the strength of the transfer material. It can be seen that the conditions are not allowed. Note that when the humidity, which is one of the photosensitive conditions, is 70% or less of the threshold value, there is almost no moisture absorption to the transfer material, so that there is little influence on the separation characteristics, and therefore separation conveyance is performed stably. . Moreover, in this embodiment, although relative humidity was made into the detection object, it is also possible to make absolute humidity into the detection object, without limiting to this. Furthermore, both temperature and humidity can be set as detection targets, and each of these detection targets is an environmental condition referred to in the present invention.
[0027]
Next, another example relating to an image forming apparatus in which the image forming method according to the embodiment of the present invention is used will be described.
FIG. 4 includes a configuration capable of forming a multicolor image including a full color, and the configuration is as follows.
[0028]
An image forming apparatus 1 (referred to as a full color image forming apparatus for convenience) 1 shown in FIG. 4 includes an image reading unit 1A and an image forming unit 1B.
[0029]
The image reading unit 1 </ b> A includes a housing 2 provided with a document placing table 2 </ b> A on the upper surface, and an exposure scanning system disposed in the housing 2.
The exposure scanning system includes a light source 2B that illuminates the document on the document table 2A, a mirror group 2C that forms one of the imaging optical systems, an imaging lens 2D, and a photoelectric conversion element 2E such as a CCD. ing. The light source 2B and the mirror group 2C are configured to be reciprocally movable. When the light source 2B and the mirror group 2C are moved in the direction of the arrow in the drawing, the document on the document table 2A is exposed and scanned, and an image forming control unit (not shown) is connected via the photoelectric conversion element 2E. On the other hand, an image information signal is output.
[0030]
The image forming unit 1B is provided with a drum-shaped photosensitive member (hereinafter referred to as a photosensitive drum) drum 3 that can rotate in the direction of the arrow as a latent image carrier. A charging device 4, a writing device 5, a developing device 6, a transfer device 7, and a cleaning device 8 for performing image forming processing along the direction are arranged.
The writing device 5 includes a semiconductor laser that is driven by an output signal from the image formation control unit, and a polygon mirror 5A that scans a laser beam emitted from the semiconductor laser toward the photosensitive drum 3, f / A writing scanning system including a θ lens 5B and a reflecting mirror 5C is provided.
[0031]
The configuration capable of forming a full-color image in the full-color image forming apparatus 1 shown in the present embodiment is as follows.
That is, the developing device 6 includes developing units 6A, 6B capable of forming images of cyan, magenta, and yellow, which are complementary colors of the color separation color based on the subtractive color mixing method, and black for gradation and black and white image formation. 6C and 6D are provided. Each developing unit is provided with a density sensor indicated by reference numeral 6E (in the figure, for convenience, the reference numeral is assigned only to one developing unit 6D), and toner density management within the developing unit is performed. To be done.
[0032]
The transfer device 7 is provided with an intermediate transfer belt 7A for primary transfer that can superimpose and transfer images of each color. Further, the intermediate transfer belt 7A collectively collects images overlaid on a transfer material such as recording paper. A transfer device 7B for secondary transfer for transferring is provided.
A primary transfer roller 7A1 for applying a transfer bias is provided at a position facing the photosensitive drum 3 with the intermediate transfer belt 7A interposed therebetween, and the visible images held on the photosensitive drum 3 are sequentially displayed. The image can be superimposed and transferred onto the intermediate transfer belt 7A.
[0033]
The transfer device 7B for secondary transfer is provided with an eccentric cam 7B1 having the same function as the belt contact / separation device 106 shown in FIG. 1, and is in contact with the intermediate transfer belt 7A by the eccentric cam 7B1. A transfer roller 7B2 as a transfer member that can be separated is provided, and electrostatic transfer is performed while pressing a recording material against the intermediate transfer belt 7A during batch transfer. The transfer roller 7B2 has a different configuration from the transfer belt 104, which is the transfer member shown in FIG. 1, but the contact conditions are the same, and the transfer nip width is changed by changing the contact pressure. The hardness of the roller surface is set so that it is possible.
[0034]
In the vicinity of the transfer device 7B for secondary transfer, a paper feeding device 9 for feeding recording paper as a transfer material is provided.
The sheet feeding device 9 includes sheet feeding cassettes 9A to 9C that store recording sheets for a plurality of different sizes and a sheet feeding tray 9D for large-volume feeding, and is in a feeding path from each sheet feeding cassette. Is provided with a paper feed roller 9E, and a registration roller 9F is disposed in front of the secondary transfer device 7B.
[0035]
When the recording paper of the selected size is fed out from any of the paper feed cassettes, the registration timing is set by the registration roller 7F at the secondary transfer position where the transfer device 7B for secondary transfer is arranged. Sent above. In FIG. 1, reference numeral 9G denotes a manual paper feed tray that can be turned upside down. This manual paper feed tray 9G feeds recording paper of a size or type that is not stored in the paper feed cassette. Used when sending.
[0036]
The recording paper that has been transferred at the secondary transfer position is conveyed toward the fixing device 11 via the conveying belt 10 and conveyed while being pressed and clamped by the heating roller 11A and the pressure roller 11B provided in the fixing device 10. In the process, the transferred image is fixed. The recording sheet after fixing is discharged toward the discharge tray 13 via the discharge roller 12.
The recording paper onto which the image has been transferred at the secondary transfer position is separated from the intermediate transfer belt 7A by the separation device 14 disposed in the vicinity of the transfer device 7B for secondary transfer.
[0037]
In the full-color image forming apparatus 1 having the configuration shown in FIG. 4, a humidity sensor as an environmental sensor for detecting environmental conditions is provided between the transfer material storage position and the transfer position. It is provided on the transfer material feed side of the paper feed cassette (position indicated by reference numeral 113A in FIG. 4).
In the configuration shown in FIG. 4, a plurality of paper feed cassettes corresponding to the transfer material storage positions are provided, and accordingly, humidity sensors are provided in the peripheral portions of the respective paper feed cassettes corresponding to this number (FIG. 4). 4, positions indicated by reference numerals 113B to 113E).
[0038]
In this way, when a humidity sensor is provided between the transfer material storage position and the transfer position, the humidity at each installation location is different, and there is a significant difference between the humidity at the outside and the external humidity. The results are as shown in FIG. Since FIG. 5 shows the result of continuous operation, the relative humidity is lowered due to the temperature rise due to continuous movement. However, a humidity sensor is provided for each transfer material storage position that reaches the transfer position. Thus, the contact relationship at the transfer position can be set so as not to deteriorate the separation characteristics of the transfer material fed out.
[0039]
【The invention's effect】
According to the onset bright, by allowing change contact conditions between the transfer material and the image bearing member in accordance with the environmental conditions at the feed position and the transfer position at least the transfer material, in particular the invention of claim 2, wherein In, the size of the nip region can be changed according to the humidity by using the nip forming conditions. For this reason, when the humidity that affects the resistance characteristics of the transfer material is targeted as an environmental condition, the nip width for the leading end of the transfer material is made smaller than other regions when the humidity is above a predetermined humidity. It is possible to reduce the charged state at the front end portion to easily prevent the front end from being adsorbed to the image carrier side and to facilitate separation. In particular, when the transfer material has low bending rigidity and is easily attracted to the image carrier and easily moves together, the tip of the transfer material is difficult to be attracted to the image carrier. It becomes possible to improve the separation characteristics from the image carrier by being easily attracted to the transfer member side. In addition, since the abutting condition changing means swings the entire transfer belt from another position independent of the position where the image carrier and the belt face each other, the transfer at the transfer nip position is changed when the transfer nip width is changed. The trouble that the belt deforms along the image carrier can be reduced.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an image forming apparatus used in an image forming method according to an embodiment of the present invention.
2 is a block diagram for explaining a configuration of a control unit used when executing the image forming method shown in FIG. 1; FIG.
FIG. 3 is a diagram showing experimental results for explaining the operation of the image forming method according to the embodiment of the present invention.
FIG. 4 is a diagram illustrating another example of an image forming apparatus used in an image forming method according to an embodiment of the present invention.
5 is a diagram showing environmental data from an environmental sensor in the image forming apparatus shown in FIG.
[Explanation of symbols]
1,100 Image forming apparatus 7B Secondary transfer apparatus 101 Transfer apparatus 106 Belt contact / separation apparatus 107 Main control unit 113 Humidity sensor as environmental sensor

Claims (7)

An image carrier on which a toner image is formed, a transfer belt that abuts on the image carrier, a contact condition changing unit, and an environmental sensor that detects humidity,
The contact condition changing means is provided at a position where the transfer belt and the image carrier do not face each other and at a position outside the transfer belt,
When the humidity detected by the environmental sensor is equal to or higher than the threshold value, the width of the transfer nip corresponding to the area where the image carrier and the transfer belt are in contact with each other is widened , and the transfer nip for the front end of the transfer material is targeted. An image forming apparatus, wherein the width is smaller than a transfer nip width for a region other than the tip . An image carrier on which a toner image is formed, a transfer belt that abuts on the image carrier, a contact condition changing unit, and an environmental sensor that detects humidity,
The contact condition changing means is provided at a position where the transfer belt and the image carrier do not face each other and at a position outside the transfer belt,
When the humidity detected by the environmental sensor is equal to or higher than the threshold, the width of the transfer nip corresponding to the area where the image carrier and the transfer belt are in contact with each other and the area where the image carrier and the transfer belt are in contact with each other The width of the transfer nip portion corresponding to is changed so as to be smaller than the second period after the first period until the leading edge of the transfer material reaches the center position of the transfer nip part. An image forming apparatus. 3. The image forming apparatus according to claim 1, wherein the transfer belt can be brought into contact with and separated from the image carrier by swinging the transfer belt by the contact condition changing means . The transfer belt is wound around the drive roller and the driven roller,
3. The image forming apparatus according to claim 1, wherein the contact condition changing means is located on the transfer belt at a position opposite to the transfer nip portion with the driven roller interposed therebetween . Abutment condition changing means as a fulcrum the driving roller side, the image forming equipment according to claim 4, characterized in that swinging the driven roller side. 6. The image forming apparatus according to claim 1, wherein the environment sensor is provided for each storage position when a plurality of storage positions for the transfer material are provided . The image forming apparatus according to claim 1, wherein the environmental sensor is provided between the transfer material storage position and the transfer position .

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