JP2004093770A - Color image forming apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a curling of a cleaning blade abutting on a photoreceptor. <P>SOLUTION: This color image forming apparatus 2 includes: a photoreceptor drum 6; latent image forming means 8 and 10 which form electrostatic latent images on the photoreceptor drum; a development unit 12 which forms toner images of respective colors in order by developing the electrostatic latent images with toners of respective colors, being one-component developers; a primary transfer roller 14 which primarily transfers the toner images by superimposing the toner images in order on an intermediate transfer belt 18; a secondary transfer roller 34 which secondarily transfers the superimposed toner images to a sheet S; and a cleaning blade 20 which is in contact with the surface of the photoreceptor drum in order to remove toner remaining on the transfer drum after the primary transfer of the toner images to the intermediate transfer belt. During idle rotation of the photoreceptor drum, a patch image is formed on the photoreceptor drum, and voltage application to the primary transfer roller is set to be off. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a color image forming apparatus and method, and more particularly, to an electrophotographic color image forming apparatus and method using a one-component developer.
[0002]
[Prior art]
Conventionally, a rotary-type developing rack is provided with a rotary-type developing unit in which a plurality of developing units respectively containing yellow, magenta, cyan, and black toners are mounted. The photoreceptor is opposed to the photoreceptor, and the electrostatic latent images of each color formed on the photoreceptor are developed. Then, the yellow, magenta, cyan, and black toner images formed on the photoreceptor are transferred by the primary transfer roller. After the primary transfer, the color toner image is secondarily transferred to a sheet passing between the intermediate transfer belt and a secondary transfer roller pressed against the intermediate transfer belt, after being sequentially superimposed on the intermediate transfer belt pressed against the photoreceptor. 2. Description of the Related Art A color image forming apparatus configured to obtain an image is known.
[0003]
The above-described image forming apparatus generally includes a cleaning device that removes, from the photoconductor, residual toner that has not been primarily transferred to the intermediate transfer belt. Among such cleaning devices, there has been known a cleaning device having a configuration in which a cleaning blade is brought into contact with a photoconductor and scrapes residual toner from the rotating photoconductor. In this case, it has been found that by adding a lubricant to the toner, "turning up" or "chattering" of the blade can be prevented by the action of the toner that is not scraped off by the blade and accumulated at the tip of the blade.
[0004]
[Problems to be solved by the invention]
In the color image forming apparatus having the above-described configuration, the photoconductor is pressed against the intermediate transfer belt, and therefore, before the primary transfer of the toner image of the color to be first developed from the photoconductor to the intermediate transfer belt, and finally, the development is performed. During the driving of the intermediate transfer belt, for example, after the primary transfer of the toner image of the desired color, the photoreceptor idles at the same peripheral speed as the intermediate transfer belt. When such idle rotation of the photoconductor is repeated, the amount of toner accumulated at the tip of the blade gradually decreases, and as a result, problems such as “turning” may occur.
[0005]
Therefore, an object of the present invention is to solve the above-mentioned problem.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a first aspect of the color image forming apparatus according to the present invention includes:
An image carrier rotatable in a predetermined direction,
Latent image forming means for forming an electrostatic latent image on the image carrier,
Developing means for developing the electrostatic latent image with toner of each color as a one-component developer to sequentially form toner images of each color;
Primary transfer means for sequentially superimposing the toner image on the intermediate transfer body and performing primary transfer,
Secondary transfer means for secondary transferring the superimposed toner image to a recording medium,
A color image forming apparatus comprising: a cleaning blade that abuts on the image carrier surface to remove toner remaining on the image carrier after primary transfer of the toner image to the intermediate transfer body.
When the image carrier is idle, a patch image is formed on the image carrier, and the application of voltage to the primary transfer unit is stopped.
[0007]
Preferably, the cleaning blade is in contact with substantially the entire effective image area in the longitudinal direction of the image carrier, and the patch image is a band-shaped image formed substantially over the entire effective image area.
[0008]
A second aspect of the color image forming apparatus according to the present invention includes:
A plurality of image carriers rotatable in a predetermined direction,
Latent image forming means for forming an electrostatic latent image on each image carrier,
Developing means for developing an electrostatic latent image on each image carrier with a toner of each color as a one-component developer to form a toner image of each color;
A plurality of primary transfer means provided for each image carrier to sequentially superimpose the toner image on each image carrier on the intermediate transfer body and perform primary transfer;
Secondary transfer means for secondary transferring the superimposed toner image to a recording medium,
A color image forming apparatus comprising: a cleaning blade that abuts on the surface of the image carrier to remove toner remaining on each image carrier after primary transfer of the toner image to an intermediate transfer body.
During idle rotation of each image carrier, the latent image forming unit and the developing unit are driven to form a patch image on the image carrier, and the voltage application to the primary transfer unit corresponding to the image carrier is stopped. It is characterized by the following.
[0009]
A third aspect of the color image forming apparatus according to the present invention includes:
A plurality of image carriers rotatable in a predetermined direction,
Latent image forming means for forming an electrostatic latent image on each image carrier,
Developing means for developing an electrostatic latent image on each image carrier with a toner of each color as a one-component developer to form a toner image of each color;
In order to sequentially transfer the toner images on each image carrier onto a recording medium, a plurality of transfer units provided corresponding to each image carrier,
A color image forming apparatus comprising: a cleaning blade that abuts on the image carrier surface to remove toner remaining on each image carrier after transferring the toner image to a recording medium.
Driving the latent image forming means and the developing means to form a patch image on the image carrier when the respective image carriers are idle; and stopping the application of voltage to the transfer means corresponding to the image carrier. It is characterized by.
[0010]
The color image forming method according to the present invention,
A toner image of each color is formed on the image carrier using a toner of each color, which is a one-component developer, and these toner images are sequentially superimposed on an intermediate transfer body by a primary transfer unit, and primary-transferred. In a color image forming method for secondary transferring a toner image to a recording medium,
At a predetermined timing, a patch image is formed on the image carrier, and the application of voltage to the primary transfer unit is stopped.
[0011]
The predetermined timing is when the image carrier is idling.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of an image forming apparatus according to the present invention will be described with reference to the accompanying drawings. Hereinafter, an example in which the present invention is applied to a full-color laser printer (hereinafter, referred to as a printer) will be described.
[0013]
In FIG. 1, the printer denoted by reference numeral 2 is provided with a photosensitive drum 6 as an image carrier, which is driven in a direction indicated by an arrow A by a motor (not shown) at a substantially central portion inside the printer. A charging device (corona charger in the illustrated example) 8 for uniformly charging the surface of the photosensitive drum 6 along the rotation direction A around the photosensitive drum 6, and a static electricity for each color on the photosensitive drum 6. A print head unit 10 for sequentially forming an electrostatic latent image, a developing unit 12 for sequentially supplying toner of each color to the photosensitive drum 6 to thereby visualize the electrostatic latent image, a primary transfer roller 14, Cleaners 16 are sequentially arranged.
[0014]
The primary transfer roller 14 is for transferring the toner adhered to the photosensitive drum 6 to the endless intermediate transfer belt 18, and a predetermined bias voltage is appropriately applied from a bias power source (not shown). The primary transfer roller 14 is in pressure contact with the photosensitive drum 6 via the intermediate transfer belt 18.
[0015]
The cleaner 16 includes a blade 20 that contacts the surface of the photosensitive drum 6 over substantially the entire effective image area in the longitudinal direction of the photosensitive drum 6 so as to scrape off toner remaining on the photosensitive drum 6 after transfer. It has become.
[0016]
The print head unit 10 selectively irradiates the photosensitive drum 6 with laser light according to image information. Specifically, when an image signal is input from an external device (for example, a personal computer) to an image signal processing unit (not shown) of the printer 2, the image signal processing unit converts the color of the image signal into yellow, cyan, magenta, and black. A digital image signal is created and transmitted to a printhead LED drive circuit (not shown). The drive circuit controls the print head unit 10 based on the input digital signal to perform exposure of the photosensitive drum 6.
[0017]
The developing unit 12 includes four developing devices 21 (21Y, 21M, 21C, and 21K) containing toners of yellow (Y), magenta (M), cyan (C), and black (K), which are one-component developers. The components are sequentially attached to the developing rack 22 by being shifted by 90 ° in the counterclockwise direction in the figure, and are rotatable counterclockwise about the shaft 24. The toner contains, for example, calcium stearate, zinc stearate, strontium stearate and the like as a lubricant. Each time an electrostatic latent image of each color is formed on the photosensitive drum 6, the developing unit 12 moves the developing roller 26 of the corresponding developing unit 21 to a developing position where the developing roller 26 approaches or contacts the photosensitive drum 6. Rotate. A predetermined bias voltage is appropriately applied to the developing roller 26 from a bias power supply (not shown).
[0018]
The intermediate transfer belt 18 is supported by the outer peripheral portions of three rollers 28, 30, and 32 and is driven to rotate in the direction of arrow B. The roller 28 is a tension roller that applies tension to the intermediate transfer belt 18. The roller 32 is connected to a drive motor (not shown), and the rollers 28 and 30 are driven to rotate as the roller 32 rotates. The roller 33 located immediately upstream of the primary transfer roller 14 with respect to the rotation direction B of the intermediate transfer belt 18 presses the intermediate transfer belt 18 toward the photosensitive drum 6, whereby the intermediate transfer belt 18 This is to ensure that the sheet is conveyed between the photosensitive drum 6 and the primary transfer roller 14 in a state of being in close contact with the photosensitive drum 6.
[0019]
A secondary transfer roller 34 is pressed against a portion of the intermediate transfer belt 18 supported by the roller 32. A predetermined bias voltage is applied to the secondary transfer roller 34 from a bias power supply (not shown), and a nip portion between the secondary transfer roller 34 and the intermediate transfer belt 18 is a secondary transfer area 36. .
[0020]
A blade 37 for scraping residual toner on the intermediate transfer belt 18 is pressed against a portion of the intermediate transfer belt 18 supported by the rollers 30. The blade 37 and the secondary transfer roller 34 are configured to be able to contact and separate from the intermediate transfer belt 18.
[0021]
A paper feed cassette 38 is detachably disposed below the printer 2. The sheets S stacked and stored in the sheet cassette 38 are sent out one by one from the uppermost one to the transport path 42 by the rotation of the sheet feeding roller 40.
[0022]
The transport path 42 passes from the paper feed cassette 38 through the nip portion of the transport roller pair 44, the nip portion of the timing roller pair 46, the secondary transfer area 36, the nip portion of the fixing roller 47 and the nip portion of the paper discharge roller pair 48, 2 extends to a paper discharge unit 50 provided on the upper surface of the sheet 2.
[0023]
Next, a printing operation (image forming operation) of the printer 2 will be described.
[0024]
At the start of the printing operation, the secondary transfer roller 34 and the cleaning blade 37 are separated from the intermediate transfer belt 18. When the printing operation is started, the photosensitive drum 6 is driven to rotate at the same peripheral speed in the direction of arrow A and the intermediate transfer belt 18 in the direction of arrow B, and the surface of the photosensitive drum 6 is uniformly charged by the charging device 8. .
[0025]
Subsequently, after the developing unit 12 is rotated and the developing unit 21Y is moved to the developing position, exposure is performed by the printer head unit 10, and an electrostatic latent image of a yellow toner image is formed on the photosensitive drum 6. The electrostatic latent image is developed by the developing device 21Y, and the developed yellow toner image is primarily transferred onto the intermediate transfer belt 18 by the operation of the primary transfer roller 14. Next, the developing device 21M moves to the developing position, and exposure, development, and primary transfer for the magenta toner image are performed. Subsequently, the developing device 21C moves to the developing position, and exposure, development, and primary transfer for the cyan toner image are performed. Thereafter, the developing device 21K moves to the developing position, and exposure, development, and primary transfer for the black toner image are performed. In this way, the toner images of each color are primary-transferred sequentially onto the intermediate transfer belt 18 moving in the direction of arrow B.
[0026]
At the same time when the primary transfer of black is completed, the secondary transfer roller 34 and the cleaning blade 37 are pressed against the intermediate transfer belt 18. Subsequently, the superimposed toner image formed on the intermediate transfer belt 18 reaches the secondary transfer area 36 as the intermediate transfer belt 18 moves. In the secondary transfer area 36, the superimposed toner image is sent out from the paper feed cassette 38 to the transport path 42 by the action of the secondary transfer roller 34, and collectively onto the sheet S supplied by the timing roller pair 46. Next is transferred. When the secondary transfer is completed, the secondary transfer roller 34 is separated from the intermediate transfer belt 18. Further, the toner remaining on the intermediate transfer belt 18 after the secondary transfer is removed by the blade 37.
[0027]
The sheet S on which the toner image has been secondarily transferred is sent to the fixing roller 47 through the transport path 42, where the toner image is fixed on the sheet S. Then, the paper S is discharged to the paper discharge unit 50 via the paper discharge rollers 48.
[0028]
In the present embodiment, when the photoconductor drum 6 idles, the charging device 8, the print head unit 10 (these components constitute an electrostatic latent image forming unit), and the developing unit 12 as in the printing operation. By driving, a toner image (hereinafter, referred to as a patch image) is formed on the photosensitive drum 6. At this time, the application of the voltage to the primary transfer roller 14 is stopped. As a result, the patch image on the photosensitive drum 6 can reach the contact position with the cleaning blade 20 through the primary transfer area. Therefore, even if the idle rotation of the photosensitive drum 6 is repeated, a sufficient amount of toner is accumulated between the tip of the cleaning blade 20 and the surface of the photosensitive drum 6, and the action of the lubricant contained in the toner causes the blade 20 to rotate. Problems such as “turning over” can be prevented. Preferably, the patch image is a band-shaped image that covers substantially the entire effective image area in the longitudinal direction of the photosensitive drum 6 (that is, the area that contacts the blade 20). It is preferable that the band patch image has a width (length in the rotation direction A of the photosensitive drum 6) of at least 1 mm and is formed at least at least two in each idle rotation period at substantially equal time intervals.
[0029]
During the idle rotation of the photoconductor drum 6, after the printing operation is started, before the yellow toner image is primarily transferred from the photoconductor drum 6 to the intermediate transfer belt 18, after the black toner image is primarily transferred, the intermediate transfer belt During the idle rotation of the intermediate transfer belt 18 to superimpose another toner image on the toner image already primary-transferred on the photosensitive drum 18, the photosensitive drum 6 starts to rotate after the power of the printer 2 is turned on, and the warm-up operation starts. During the period from the end of the previous print to the start of the next print when printing is continuously performed, after the end of the print operation, the printer 2 performs a predetermined post-operation. This includes a period during which the driving of the main motor is continued for a while and the photosensitive drum 6 is post-rotated.
[0030]
2 to 4 show examples of ON / OFF timing of each device of the printer 2. FIG. 2 shows a case where a color image is formed, FIG. 3 shows a case where a monochrome image is formed, and FIG. Is formed.
[0031]
2, starts driving the intermediate transfer belt 18 and the photosensitive drum 6 at time T _1. In the pre-rotation period of the period T _{1 to} T ₂ , in order to form a band patch image, the drive of the print head unit 10 and the application of the bias voltage to the developing roller 26 with the developing unit 21K arranged at the developing position are appropriately performed. Turn on / off. In the period _T 1 through T _2, the bias voltage application of the primary transfer roller 14 is turned off. In the period _T 2 through T _3, for the primary transfer, the driving of the print head unit 10, and the developing devices 21Y, 21M, 21C, in a state arranged sequentially developing position 21K bias of the developing roller 26 of the developing devices The voltage application is turned on / off as appropriate. In the period _T 2 through T _3, the bias voltage application of the primary transfer roller 14 to turn. In the rotation period after a period T ₃ through T _4, in order to form a band patch image, the driving of the print head unit 10, and a bias voltage application of the developing roller 26 in the state in which the developing device 21Y to the developing position appropriately Turn on / off. In the period _T 3 through T _4, the bias voltage application of the primary transfer roller 14 is turned off. It terminates the driving of the intermediate transfer belt 18 and the photosensitive drum 6 at time T _4.
[0032]
In the example of FIG. 2, the patch image is formed using the black and yellow toners in the pre-rotation period and the post-rotation period, respectively. However, the color of the patch image to be formed depends on the configuration of the developing unit 12. May be determined appropriately. Since the toner in the developing unit 21 is reduced by forming the patch image, the four types of toner may be consumed as uniformly as possible for forming the patch image.
[0033]
In FIG. 3, on / off control of each device is performed at the same timing as in the example of FIG. However, since a monochrome image is formed, the primary transfer period (T ₂ through T _3), is used only the developing unit 21K is in the state in which the developing device at the developing position, the developing device 21K of the developing roller 26 The bias voltage application is turned on / off as appropriate. Furthermore, the pre-rotation period _(T 1 through T ₂₎ and the post-rotation period _(T 3 through T _4), only the developing unit 21K is used to form a patch image using black toner.
[0034]
4, the pre-rotation period in (period T ₁ through T ₂₎ and the first transfer period for forming an image on a sheet surface (period T ₂ through T _3), of each device at the same timing as the example of FIG. 3 On / off control is performed. Referring to FIG. 1, the periods T _{3 to} T ₄ are periods during which the sheet S is transported via a reverse path (not shown) so that the back surface of the sheet S faces the roller 32 of the secondary transfer area 36. The intermediate transfer belt 18 and the photosensitive drum 6 are idle. In this period, in order to form a patch image, the drive of the print head unit 10 and the application of the bias voltage to the developing roller 26 of the developing unit 21K are appropriately turned on / off. In the period _T 3 through T _4, the bias voltage application of the primary transfer roller 14 is turned off. In the period T ₄ through T _5, performs on-off control of each device at the same timing as the time period T ₂ through T _3, thereby performing primary transfer for forming an image on a sheet back surface. The rotation period after the period T ₅ through T _6, on-off control of each device at the same timing as the example of FIG. 3 is performed.
[0035]
The above description relates to one embodiment of the present invention, and the present invention is not limited to this and can be variously modified. For example, in the above embodiment, the photosensitive drum 6 is used as the image carrier, but a photosensitive belt may be used. Although the roller 14 is used as the primary transfer unit, a belt, a brush, a corona charger, a film, or the like may be used.
[0036]
According to the present invention, a plurality of photoconductors and an intermediate transfer belt are opposed to each other, and toner images of respective colors formed on the respective photoconductors are sequentially superimposed on the intermediate transfer belt and primary-transferred, and then pressed against the intermediate transfer belt and the intermediate transfer belt. The present invention can be applied to a tandem-type color image forming apparatus that performs a secondary transfer of a color toner image to a sheet passing between the secondary transfer rollers. That is, a patch image is formed on each of the photoconductors when the photoconductors idle, and the voltage application to the primary transfer unit located on the opposite side of each of the photoconductors with the intermediate transfer belt therebetween is set to off. As a result, it is possible to prevent problems such as “turning” of the cleaning blade that comes into contact with each photoconductor.
[0037]
The present invention is further applicable to a tandem-type color image forming apparatus for sequentially transferring a color toner image directly to a sheet conveyed on a sheet conveying belt having the same configuration as the intermediate transfer belt. That is, in a color image forming apparatus in which a plurality of photoconductors and a paper transport belt are opposed to each other and a toner image of each color formed on each photoconductor is sequentially superimposed and transferred onto a paper transported on the paper transport belt, A patch image is formed on the photoreceptor during idle rotation of the body, and voltage application to a transfer unit located on the opposite side of each photoreceptor across the paper transport belt is turned off.
[0038]
In addition, the intermediate transfer member onto which the toner image is transferred from the photosensitive member is not limited to the belt.
[0039]
【The invention's effect】
According to the present invention, by forming a patch image on the surface of the photoconductor during idling of the photoconductor, it is possible to prevent problems such as “turning” and “chatter” of the cleaning blade that comes into contact with the photoconductor.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram illustrating an embodiment of a color image forming apparatus according to the present invention.
FIG. 2 is a timing chart during full color printing.
FIG. 3 is a timing chart for single-sided monochrome printing.
FIG. 4 is a timing chart during double-sided monochrome printing.
[Explanation of symbols]
2: color image forming apparatus, 8: charging device, 10: print head unit, 12: developing unit, 14: primary transfer roller, 18: intermediate transfer belt, 21: developing device, 26: developing roller, 34: secondary transfer roller.

Claims (5)

An image carrier rotatable in a predetermined direction,
Latent image forming means for forming an electrostatic latent image on the image carrier,
Developing means for developing the electrostatic latent image with a toner of each color as a one-component developer to sequentially form a toner image of each color;
Primary transfer means for sequentially superimposing the toner image on the intermediate transfer body and performing primary transfer,
Secondary transfer means for secondary transferring the superimposed toner image to a recording medium,
A color image forming apparatus comprising: a cleaning blade that abuts on the image carrier surface to remove toner remaining on the image carrier after primary transfer of the toner image to the intermediate transfer body.
A color image forming apparatus which forms a patch image on an image carrier when the image carrier is idle, and stops applying voltage to a primary transfer unit. The cleaning blade abuts on substantially the entire effective image area in the longitudinal direction of the image carrier, and the patch image is a band-shaped image formed on substantially the entire effective image area. Item 1. The color image forming apparatus according to Item 1. A plurality of image carriers rotatable in a predetermined direction,
Latent image forming means for forming an electrostatic latent image on each image carrier,
Developing means for developing an electrostatic latent image on each image carrier with a toner of each color as a one-component developer to form a toner image of each color;
A plurality of primary transfer means provided for each image carrier to sequentially superimpose the toner image on each image carrier on the intermediate transfer body and perform primary transfer;
Secondary transfer means for secondary transferring the superimposed toner image to a recording medium,
A color image forming apparatus comprising: a cleaning blade that abuts on the surface of the image carrier to remove toner remaining on each image carrier after primary transfer of the toner image to an intermediate transfer body.
During idle rotation of each image carrier, the latent image forming unit and the developing unit are driven to form a patch image on the image carrier, and the voltage application to the primary transfer unit corresponding to the image carrier is stopped. A color image forming apparatus comprising: A plurality of image carriers rotatable in a predetermined direction,
Latent image forming means for forming an electrostatic latent image on each image carrier,
Developing means for developing an electrostatic latent image on each image carrier with a toner of each color as a one-component developer to form a toner image of each color;
In order to sequentially transfer the toner images on each image carrier onto a recording medium, a plurality of transfer units provided corresponding to each image carrier,
A color image forming apparatus comprising: a cleaning blade that abuts on the image carrier surface to remove toner remaining on each image carrier after transferring the toner image to a recording medium.
Driving the latent image forming means and the developing means to form a patch image on the image carrier when the respective image carriers are idle; and stopping the application of voltage to the transfer means corresponding to the image carrier. A color image forming apparatus. A toner image of each color is formed on the image carrier using a toner of each color, which is a one-component developer, and these toner images are sequentially superimposed on an intermediate transfer body by a primary transfer unit, and primary-transferred. In a color image forming method for secondary transferring a toner image to a recording medium,
A color image forming method, wherein a patch image is formed on an image carrier at a predetermined timing, and a voltage application to a primary transfer unit is stopped.

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