JP2004078030A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent automatically an abnormal flying phenomenon of toner with an image forming apparatus itself. <P>SOLUTION: A CIS device (contact image sensor) 50 having a resolution in a paper feeding direction equivalent to or higher than a resolution in a subscanning direction of an exposure device is disposed between a pair of carrier rollers 37 and 38 positioned downstream of a fixing device along a paper passing direction (carrying direction) of transfer material P. The transfer material P after fixing of a toner image is passed through a gap G by an opposing plate 51 arranged in the lower part. The abnormal flying phenomenon of the toner image after the fixing is detected with the CIS device 50 by changing suitably potential of a light portion, a developing bias and peripheral velocity of a development sleeve during an exposure, and by changing an amount of mounted toner. A setting condition of the fewest abnormal flying phenomenon is adopted based on the detection result. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus such as a printer, a copying machine, and a facsimile.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in an image forming apparatus such as a printer or a copying machine, a mode has been proposed in which a test print is output and a user or a service person checks the quality of an image. An image signal or an image creation program is operated in advance in an image forming apparatus to output a necessary image as a test print image, and an output result is fed back to an appropriate state or a desired state. .
[0003]
Further, there is an image forming apparatus in which a dedicated image reading unit is provided downstream of a fixing unit to read a test print image to grasp the current state of the image forming apparatus. Note that, as the image reading unit, a reader scanner used to read an image of a document may be used instead of providing a dedicated unit downstream of the fixing unit. The output test print image is manually or automatically conveyed to the reader scanner side, and the image of the test print is read by the reader scanner. Further, an unfixed image on the upstream side of the fixing unit may be read, or a toner image on the image carrier may be read.
[0004]
On the other hand, when the user or the service person notices that the image is abnormal, it is common practice to operate various parameters of the image forming apparatus so as to obtain the optimum condition from the normal output image or the test print image. That is.
[0005]
[Problems to be solved by the invention]
By the way, when the digital image signal and the image forming conditions of the hardware of the image forming apparatus are changed to operate so as to obtain an optimal image, for example, if the image density is to be optimized, the conditions to be operated are as follows. Since it is relatively simple and easy to visually confirm, the user or service person can easily change the conditions.
[0006]
However, the abnormal flying phenomenon of the toner that occurs downstream of characters and lines with respect to the paper passing direction (conveying direction) of the transfer material (for example, paper or transparent film) has a plurality of causes, and a plurality of phenomena are observed. In spite of the fact that it is difficult to confirm the determination with the naked eye, it is necessary to change a condition that is extremely difficult to operate because it gives an impression of deterioration as a whole image.
[0007]
The abnormal flying phenomenon referred to here is a so-called "development tail" or a so-called "development splatter" generated in the developing unit, a so-called "transfer splatter" generated in the transfer separation unit, and a so-called "transfer splatter" generated in the fixing unit. "Fixation splashes".
[0008]
In the “development tailing”, it is considered that the spikes of the toner of the developing means are transferred as they are onto the image and onto the transfer material, and the quality of a ruled line image or the like is extremely reduced. “Development scattering” and “transfer scattering” are those in which toner flies around the image in a single unit or in cluster units, and makes the image ambiguous and extremely degrades character quality and the like. "Fixing scattering" is a phenomenon that occurs when the transfer material enters the fixing means due to wind pressure, electric repulsion, water vapor pressure in the transfer material, etc., and toner is blown to the downstream portion of the image. Extremely lower.
[0009]
Although “transfer scattering” occurs in the transfer unit, the phenomenon varies depending on the latent image condition and the development condition which are the main body conditions upstream of the transfer unit. Similarly, although "fixing scattering" occurs in the fixing unit, the phenomenon varies depending on the latent image condition, the developing condition, and the transfer separation condition which are the main body conditions upstream of the fixing unit.
[0010]
As described above, since the abnormal flying phenomenon of the toner generated on the downstream side of the character or the line is complicated with various causes, it is very complicated and difficult to adjust the user and the service person.
[0011]
Accordingly, an object of the present invention is to provide an image forming apparatus which detects an abnormal flying phenomenon of toner and suppresses the abnormal flying phenomenon by the image forming apparatus itself, thereby eliminating the need for adjustment of a user or a service person. Things.
[0012]
[Means for Solving the Problems]
According to a first aspect of the present invention, a uniformly charged image carrier surface is exposed by digital exposure means to form an electrostatic latent image, and toner is adhered to the electrostatic latent image by developing means to form a toner image. In an image forming apparatus in which development is performed, the toner image is transferred to a transfer material by a transfer separation unit, and the toner image is fixed on the transfer material by a fixing unit, the amount of toner applied on the transfer material before fixing is changed. Toner applied amount changing means, control means for controlling the applied toner amount changing means, and image reading means for reading an output pattern of the fixed toner image at a resolution equal to or higher than the resolution in the sub-scanning direction of the digital exposure means Wherein the control means controls the applied toner amount changing means to fix test pattern images having different applied toner amounts on one or a plurality of transfer materials, At this time, the difference in the abnormal flying phenomenon of the toner occurring on the downstream side in the transfer material passing direction in the plurality of test pattern images is detected by the image reading means, and based on the detection result, the control means determines the optimum condition for the amount of applied toner. Is determined.
[0013]
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the applied toner amount changing unit includes a unit configured to change a surface potential of the image carrier, and a developing bias applied to the developing unit during development. And at least one of means for changing the peripheral speed of the developing sleeve of the developing means.
[0014]
According to a third aspect of the present invention, a uniformly charged surface of the image carrier is exposed by a digital exposure unit to form an electrostatic latent image, and toner is adhered to the electrostatic latent image by a developing unit. In an image forming apparatus in which development is performed, the toner image is transferred to a transfer material by a transfer separation unit, and the toner image is fixed on the transfer material by a fixing unit, the charge amount of the toner on the transfer material before fixing is changed. Toner charge amount changing means, control means for controlling the toner charge amount change means, and image reading means for reading an output pattern of the toner image after fixing at a resolution equal to or higher than the resolution in the sub-scanning direction of the digital exposure means And controlling the toner charge amount changing means by the control means to fix test pattern images having different toner charge amounts on one or a plurality of transfer materials, At this time, the image reading means detects a difference in the abnormal flying phenomenon of the toner occurring on the downstream side in the transfer material passing direction in the plurality of test pattern images, and based on the detection result, the control means determines the optimal condition for the toner charge amount. Is determined.
[0015]
According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, the toner charge amount changing unit is a transfer separation unit, and the transfer separation unit changes a discharge current. .
[0016]
The invention according to claim 5, wherein a uniformly charged image carrier surface is exposed by digital exposure means to form an electrostatic latent image, and toner is adhered to the electrostatic latent image by developing means to form a toner image. Developing, transferring the toner image to a transfer material by transfer separation means, and fixing the toner image on the transfer material by the fixing means, when the toner image is fixed by the fixing means, A heat transfer mode changing unit for changing a heat transfer mode of the fixing unit; a control unit for controlling the heat transfer mode changing unit; and a resolution in a sub-scanning direction of the digital exposure unit for outputting an output pattern of the toner image after fixing. Image reading means for reading at a resolution equal to or higher than the above, wherein the control means controls the heat transfer mode changing means to control one or more test pattern images having different heat transfer modes. The image reading unit detects the difference in the abnormal flying phenomenon of the toner that occurs on the downstream side of the transfer material passing direction in the plurality of test pattern images when the image is fixed on several transfer materials, and the image reading unit detects the difference based on the detection result. An optimal condition for the heat transfer mode is determined by the control means.
[0017]
According to a sixth aspect of the present invention, in the image forming apparatus according to the fifth aspect, the heat transfer mode changing unit sets a fixing temperature of the fixing unit, a unit that changes a nip width of a fixing nip portion, At least one of means for changing a position of a fixing entrance guide for guiding the transfer material to the fixing nip portion of the means.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
First, the outline of the present invention will be described. It has image reading means for reading the output pattern of the toner image after fixing at a resolution equal to or higher than the resolution in the sub-scanning direction of the digital exposure means, while changing the setting conditions of the image forming apparatus when forming a test pattern image ( Form multiple test pattern images (while shaking). At this time, the image reading means detects the abnormal flying phenomenon of the toner which occurs on the downstream side of the characters or lines in the test pattern in the transfer material passing direction. This makes it possible to automatically find the optimum conditions for minimizing the abnormal flying phenomenon.
[0019]
Conditions for changing the abnormal flying phenomenon of the toner include the following.
[0020]
First, the abnormal flying phenomenon changes depending on the difference in the amount of applied toner on the transfer material. Means for changing the amount of applied toner include means for changing the surface potential of the image carrier, means for changing the developing bias, and means for changing the peripheral speed of the developing sleeve. By changing at least one of these, the abnormal flying phenomenon can be suppressed. This will be described in detail in Embodiment 1.
[0021]
Second, the abnormal flying phenomenon also changes depending on the difference in the charge amount of the toner on the transfer material. As a means for changing the charge amount of the toner, there is a transfer separation means. That is, the discharge current in the transfer separation means is changed. This will be described in detail in Embodiment 2.
[0022]
Third, the abnormal flying phenomenon also changes depending on the difference in the heat transfer mode applied to the transfer material of the fixing unit. As means for changing the heat transfer mode, there are means for adjusting the constant temperature of the fixing means, means for adjusting the nip width of the fixing nip portion, means for changing the position of the fixing entrance guide for guiding the transfer material to the fixing means, and the like. . By changing at least one of these, the abnormal flying phenomenon can be suppressed. This will be described in detail in Embodiment 3.
[0023]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the components denoted by the same reference numerals have the same configuration or operation, and a repeated description thereof will be omitted as appropriate.
[0024]
<Embodiment 1>
FIG. 1 shows an image forming apparatus according to Embodiment 1 as an example of an image forming apparatus according to the present invention. The image forming apparatus shown in FIG. 1 is an electrophotographic / digital printer, and FIG. 1 is a longitudinal sectional view showing a schematic configuration thereof.
[0025]
The printer shown in FIG. 1 (hereinafter referred to as “image forming apparatus”) includes a reader / scanner unit 1 and a printer unit 20. The reader scanner unit 1 presses the original placed on the original platen glass 2 with the pressure plate 3, and scans the original with the fluorescent lamp 4 and the reflection mirror 5. The reflected light from the original at this time is reflected by the reflection mirrors 6, 7, and 8 and passes through the lens 9, and is converted into a digital image signal by the CCD 10.
[0026]
On the other hand, the digital image signal converted by the CCD 10 is subjected to image processing such as filtering, density conversion, and γ conversion by an image processing unit (not shown), and then drives the semiconductor laser 21 in the printer unit 20. Is converted to an image signal. A laser beam generated from the semiconductor laser 21 is reflected by a polygon mirror 23 rotated by a polygon motor 22, further passes through a lens 24 and a reflection mirror 25, and is a drum-type photoconductor (hereinafter, "photosensitive drum") as an image carrier. 26). In the present image forming apparatus, the resolution in the sub-scanning direction is 600 dpi (dots / inch), and the basic resolution in the main scanning direction is also 600 dpi. The resolution of the main scanning direction can be changed as long as the lighting cycle is changed, but the main scanning direction and the sub-scanning direction are the same in terms of a toner image of one pixel. An exposure device (digital exposure means) 42 is constituted by the reflection mirror 25 from the semiconductor laser 21 described above.
[0027]
Prior to the above-described laser beam irradiation (exposure), the photosensitive drum 26 is uniformly (uniformly) charged to a predetermined polarity and potential by the primary charger 27. After the charging, the surface of the photosensitive drum 26 is irradiated with the laser beam to remove the charge of the irradiated portion, and an electrostatic latent image corresponding to the image information is formed. The potential of the electrostatic latent image is detected by the potential sensor 28. The potential of this electrostatic latent image can be changed by adjusting the discharge current value in the primary charger 27 and the intensity of the laser beam.
[0028]
The latent image potential on the photosensitive drum 26 is developed (developed) as a toner image by attaching toner by a developing sleeve 29a of a developing device (developing means) 29. After the toner image is subjected to corona discharge from the post charger 30 on the photosensitive drum 26 and the charge amount is adjusted, the transfer material supplied from the sheet feeding deck 33 by the transfer charger 31 and the separation charger 32 is used. Transferred to P.
[0029]
The transfer material P after the transfer of the toner image is conveyed to a fixing device (fixing means) 36 by a conveyance belt 35, where it is heated and pressed to fix the toner image on the surface.
[0030]
A pair of transport rollers 37 and 38 are disposed downstream of the fixing device 36, and the transfer material P after the toner image is fixed is discharged onto the discharge tray 34 by the pair of transport rollers 37 and 38. A contact image sensor (hereinafter, referred to as a “CIS device”) 50 as image reading means is disposed between the pair of transport rollers 37 and 38, and an image (toner) fixed on the transfer material P is provided. Image) can be confirmed.
[0031]
The toner remaining on the surface of the photosensitive drum 26 after the transfer of the toner image without being transferred onto the transfer material P at the transfer charger position is scraped off from the surface of the photosensitive drum 26 by the cleaning device 39. In addition, the residual charges remaining on the surface of the photosensitive drum 26 are removed by the static eliminator 40 (the pre-potential is leveled), and the image is provided for the next image formation.
[0032]
FIG. 2 is a diagram illustrating an electrical configuration of the control board 41 inside the image forming apparatus and an external input / output device. In the figure, in a control board 41, a ROM 41f in which a control program is described, and a RAM 41g which is a temporary storage element of necessary data on the program and also develops an image signal are connected to a CPU 41a which is a central element of processing. I have. An I / O 41b as an interface and an A / D converter 41d and a D / A converter 41e as data conversion elements 41c are connected to an external input / output device, and information is transmitted between the control board 41 and the input / output device. Input and output.
[0033]
Then, an image signal from the reader scanner unit 1 and an image signal from the CIS device 50 are input to the control board 41 as input sources in the present embodiment. As an output destination, a semiconductor laser 21 for writing an image, a high-voltage power supply unit 70 (see FIG. 5) for applying a developing bias to a developing sleeve 29a of a developing device 29 for performing development, and a device for changing a charge amount of toner. A high-voltage power supply unit 80 (see FIG. 10; described later in a second embodiment) for passing a post current to the post-charger 30 and a high-voltage power supply for passing a transfer current for transferring toner onto a transfer material to the transfer charger 31 A unit 90 (see FIG. 10; described in a second embodiment described later), a heater 100 whose fixing temperature is adjusted for fixing (fixing) the toner, and a fixing entrance guide 105 (see FIG. 12: The position changing unit 106 for changing the position described in the third embodiment) is connected. That is, the semiconductor laser, the developing bias, the transfer current, the post current, the fixing temperature, and the fixing entrance guide position can be changed based on the image signals from the reader scanner unit 1 and the CIS device 50.
[0034]
FIG. 3 is a cross-sectional view illustrating the CIS device 50. The CIS device 50 is provided between the pair of conveying rollers 37 and 38, that is, on the downstream side of the pair of conveying rollers 37 and the upstream side of the pair of conveying rollers 38 along the sheet passing direction of the transfer material P (the direction of arrow K in the figure). Are arranged. An opposing plate 51 is provided below the CIS device 5 so as to oppose it. A gap G is formed between the CIS device 50 and the opposing plate 51. When the transfer material discharged from the fixing roller passes through the gap G, the CIS device 50 detects the toner image on the transfer material.
[0035]
Inside the CIS device 50, an LED array 60 that illuminates the toner image on the transfer material, a contact glass 61 that protects the inside of the transfer material P from rubbing, paper dust, and the like, and a cell that guides a projected light beam from the transfer material P A Fock glass 62 and a photodiode 63 to be read as a projection image are incorporated. The CIS device 50 according to the present embodiment is a high-definition sensor having a longitudinal direction (paper passing width direction) of about 300 mm and a longitudinal resolution of 2400 dpi. The sampling frequency is improved, and the paper passing direction resolution inside the image forming apparatus is 4800 dpi. It has become. Since the resolution in the sub-scanning direction of the laser beam is 600 dpi, the resolution in the paper passing direction, which is the same as that in the sub-scanning direction, is 4800 dpi, which indicates a sufficiently high resolution for reading an image on the transfer material. In addition, since the CIS device 50 is obtained as luminance signal information of 8 bits and 256 gradations, it is possible to make a precise judgment on gradation.
[0036]
FIG. 4 is a diagram of the CIS device 50 as viewed from above. This shows that the CIS device 50 is arranged on the opposing plate 51 in a region surrounded by the pair of conveying rollers 37 and 38.
[0037]
FIG. 5 is a diagram illustrating the configuration of the exposure device 42 and the developing device 29 inside the image forming apparatus shown in FIG. The laser beam generated from the semiconductor laser 21 is applied to the surface of the photosensitive drum 26 via the lens 24 and the reflection mirror 25 by the rotation of the polygon mirror 23 by the polygon motor 22. Since the photosensitive drum 26 is previously charged with a uniform potential by the primary charger 27, the electric charge of the laser beam irradiated portion is removed, and a latent image potential corresponding to the image information is formed.
[0038]
The adjustment of the latent image potential is detected by the potential sensor 28. The adjustment of the latent image potential can be changed by adjusting the discharge current value in the primary charger 27 and the intensity of the laser beam. The electrostatic latent image on the photosensitive drum 26 is applied with a developing bias from the high-voltage power supply unit 70 to the developing sleeve 29a of the developing device 29, so that the toner is attached to the electrostatic latent image and developed (developed) as a toner image. The waveform generated by the high-voltage power supply unit 70 is produced by superimposing a DC component on an AC waveform having a frequency of 2 kHz, an amplitude of 1.3 kV, and a duty (Duty) of 40%. The DC component can be changed from 0 to 500V. The developing sleeve 29a of the developing device 29 is rotated such that the moving direction of the surface thereof (the direction of the arrow R29) is forward with respect to the moving direction of the surface of the photosensitive drum 26 (the direction of the arrow R26). Further, the developing sleeve 29a can be switched to a peripheral speed ratio of two stages of 130% and 180% with respect to the peripheral speed of the photosensitive drum 26 by a transmission mechanism (not shown).
[0039]
FIG. 6 shows the amount of applied toner of the solid black image output from the image forming apparatus and the abnormal flying of toner generated downstream of the horizontal line in the paper passing direction when a horizontal line image of 8 lines and 16 spaces is output. The phenomenon is graphed by a numerical method described later. The amount of applied toner can be directly measured as a weight using an electronic balance or the like, or indirectly measured using a transmission densitometer or the like. The horizontal line image having 8 lines and 16 spaces is an image in which an abnormal flying phenomenon easily occurs due to an appropriate line width and space at a resolution of 600 dpi in the sub-scanning direction.
[0040]
As an abnormal toner flying phenomenon, there are a plurality of phenomena affected by the amount of applied toner. For example, the so-called “development tailing” that is generated in the form of an icicle on the downstream side of the horizontal line under the influence of the spikes of the toner on the developing sleeve 29a, the so-called “development splatter” in which the toner on the line scatters in white characters, Commonly known as "transfer splatter", which is not transferred properly at the transfer position and scatters in white characters, or a common name generated when wind enters the fixing device 36 due to wind pressure, electric repulsion, water vapor pressure in the transfer material, etc. For example, "fixation scattering". Each of these phenomena is highly relevant to the amount of applied toner on the transfer material. As shown in FIG. 6, when the amount of applied toner increases, the abnormal flying phenomenon sharply increases.
[0041]
FIG. 18 is a change table of the exposure device 42 and the developing device 29 for changing the amount of applied toner on the transfer material. Eight types of setting conditions S are provided, and the latent image conditions described with reference to FIG. 5 are changed to change the bright portion potential VL on the photosensitive drum 26, the DC component of the developing bias is changed, and the circumference of the photosensitive drum 26 is changed. The ratio of the peripheral speed of the developing sleeve 29a to the speed is switched. As a result, assuming that the applied amount of toner in the case of the setting condition S = 1 is 100, the applied amount of the toner in the setting condition S = 8 having the smallest applied amount can be changed so as to be halved to about 50. ing. In this embodiment, as the applied toner amount changing means, the exposure device 42 or the developing device 29 is used, or a means for changing the peripheral speed ratio of the developing sleeve 29a is used. Although the dark portion potential VD of the photosensitive drum 26 is fixed at 400 V in FIG. 3, it goes without saying that the dark portion potential VD may be changed. In this case, the primary charger 27 also serves as a toner application amount changing unit.
[0042]
FIG. 7 is a flowchart illustrating a sequence performed in the present embodiment, that is, a sequence for minimizing an abnormal flying phenomenon. First, initialization is performed with the setting condition S set to 0 (S1). Next, at the same time as the setting condition S is incremented, the setting condition in FIG. 18 is set so as to be output (S2). Next, a test print subroutine for forming a test pattern image is executed (S3: described later with reference to FIG. 8), and a subroutine for detecting an abnormal flying phenomenon is called (S4: described later with reference to FIG. 9). ), The abnormal flight under each setting condition is grasped as a numerical value. It is checked whether there are any more setting conditions (S5), a timer is executed (S6), and the test print is repeated. When the setting condition is S = 8 as in the case of the present embodiment, the best setting condition is determined from a total of eight abnormal flight data (S7), and simultaneously displayed on the operation panel of the image forming apparatus. (S8) Test printing is performed under the best setting conditions. The user or the service person sees the display on the operation panel and the test print determined to be the best, executes a sequence that provides room for input by a new user designation (S10), and terminates this sequence. The execution of this sequence is basically performed by a user or a serviceman, but may be performed after a predetermined number of image formations is completed or when the image forming apparatus is started up.
[0043]
FIG. 8 is a flowchart of a subroutine for test print executed in the sequence described in FIG. First, an image signal is created, and an 8-line 16-space horizontal line image of the entire screen of the transfer material size is developed on the RAM (S11). The test print is executed by driving the semiconductor laser 21 according to the image signal (S12). Note that the transfer material size is the size of the transfer material P currently mounted on the paper feed deck 33 (see FIG. 1). A paper feed deck may be selected from the paper deck.
[0044]
FIG. 9 is a flowchart of a subroutine for detecting an abnormal flying phenomenon executed in the sequence described in FIG. First, the image signal from the CIS device 50 is stored in the RAM 41g (see FIG. 2) (S21). However, in the present embodiment, 4800 dpi in the paper passing direction, 2400 dpi in the longitudinal direction of the CIS device 50, and a maximum transfer material size of about 290 mm of A4 width is read by an 8-bit signal, so an extremely large RAM area is required. Therefore, as for the size to be actually stored on the RAM, nine locations in a range of about 5 mm in length and width are read. As initialization for executing each of the nine locations, the location A is set to 0 (S22), and when the location A is incremented, the processing is started from the first location (S23).
[0045]
First, binarization processing is performed on the image of the location A using a dynamic threshold (S24). Further, the line B is set to 0 as initialization for executing all the lines at the point A (S25), and the processing is started from the first line when the line B is incremented (S26). Thereby, the standard deviation σ0 of the profile is obtained from the line width profile of the point A and the line B of interest at present (S27).
[0046]
Further, the toner scattered around the current point A and around the line B is obtained as a scattering index T0. This scattering index T0 is calculated as a function of the size of the scattered toner, the number of scattered toner, and the distance from the line (S28).
[0047]
Thereafter, it is confirmed whether all the lines at the point A have been calculated (S29), and this is repeated. Then, the average standard deviation σA and the average scattering index TA at the point A are obtained (S30), and it is confirmed whether all the points have been calculated (S31), and this is repeated.
[0048]
When all parts have been completed, the standard deviation σ having the largest value and the index T having the largest value are obtained (S32). The standard deviation σ becomes an appropriate numerical criterion when the “development tailing” or the like occurs, because the fluctuation of the line width increases and the value of σ increases. On the other hand, when a scattering phenomenon such as “developing scattering”, “transfer scattering”, or “fixing scattering” occurs, the scattering coefficient T is an appropriate determination criterion quantified by increasing the value of T.
[0049]
Finally, the abnormal flight coefficient C is obtained by summing the above-mentioned standard deviation σ and the scattering coefficient T, and this coefficient is defined as the abnormal flying coefficient (S33).
[0050]
As described above, since both the tailing phenomenon and the scattering phenomenon increase the abnormal flight coefficient C, the abnormal flight coefficient C, which is the sum of the two, is effective as an appropriate determination criterion that quantifies image quality. In the present embodiment, a one-to-one sum is used. However, a weight may be provided or a product may be calculated, and this is a calculation formula that also needs to consider the actual visual transfer function (VTF) characteristics and the like. Here, the VTF characteristic is a characteristic of the visual transfer function. The visual transfer function is used to represent human visual characteristics, and the lightness axis is 4 cycles / deg. A characteristic having a peak to a large extent is mainly used. In other words, the visual characteristics of the eye with respect to the spatial frequency are expressed as a function similar to the MTF of an optical system or the like. The place with the upper peak is the most sensitive, and humans can understand whether it is too fine or too coarse. It shows that it is difficult. In this embodiment, the VTF will not be described in detail. However, since a phenomenon that is unpleasant for the eyes cannot generally ignore the characteristics of the eyes, the VTF may be taken into consideration. In fact, it has been known as an experience that the tailing phenomenon is more conspicuous in appearance than the toner scattering phenomenon.
[0051]
By executing the above sequence by the designation of a user or a serviceman or automatically, it is possible to select an image having the lowest abnormal flight coefficient C due to a latent image and a development factor, in other words, an image having less abnormal flight phenomenon. And the optimum conditions can be obtained in a short time.
[0052]
In the present embodiment, the sequence is such that the setting conditions are changed for each test print, but a plurality of setting conditions may be changed within one print.
[0053]
<Embodiment 2>
FIG. 10 is an explanatory diagram of the transfer / separation unit (the transfer charger 31 and the separation charger 32) inside the image forming apparatus shown in FIG. The electrostatic latent image on the photosensitive drum 26 is developed (developed) as a toner image by attaching toner to the developing unit 29. After that, the toner image on the photosensitive drum 26 is subjected to corona discharge by the post-charger 30 to which a voltage is applied by the high-voltage power supply unit 80 on the photosensitive drum 26, and the charge amount is adjusted. The generated waveform of the high-voltage power supply unit 80 is produced by superimposing a DC component on an AC waveform having a frequency of 1 kHz, an amplitude of 11 kV, and a duty (Duty) of 50%. The constant current control from 0 to +300 μA can be performed by changing the DC component.
[0054]
The toner image on the photosensitive drum 26 whose charge amount has been adjusted in this way is transferred to the transfer material S supplied from the sheet feeding deck 33 by the transfer charger 31 and the separation charger 32. The transfer charger 31 is also applied with a voltage of about -5 to -9 kV by the high-voltage power supply unit 90, so that constant current control from 0 to -600 μA is possible. The separation charger 32 is connected to a high-voltage power supply unit (not shown), and is applied to the photosensitive drum 26 by applying a voltage in which a DC component is superimposed on an AC waveform by the high-voltage power supply unit. The transfer material P is separated.
[0055]
In this embodiment, the post charger 30 and the transfer charger 31 are used as a toner charge amount changing unit.
[0056]
FIG. 11 shows the charge amount of the toner of the solid black image output from the image forming apparatus and the abnormal flying of the toner generated on the downstream side in the sheet passing direction of the horizontal line when the horizontal line image of 8 lines and 16 spaces is output. This is a graph of the phenomenon. The actual charge amount of the toner is measured by a Q meter or the like. The horizontal line image having 8 lines and 16 spaces is an image in which an abnormal flying phenomenon easily occurs due to an appropriate line width and space at a resolution of 600 dpi in the sub-scanning direction.
[0057]
As the abnormal flying phenomenon of the toner, there are a plurality of phenomena affected by the charge amount of the toner. For example, a so-called “transfer scattering” which is scattered in a white portion without being properly transferred at a transfer position, or is generated due to wind pressure, electric repulsive force, pressure of water vapor in a transfer material, etc. when entering the fixing device 36. Commonly known as "fixation scatter". Each of these phenomena is highly relevant to the charge amount of the toner on the transfer material, and as shown in the figure, when the charge amount of the toner decreases, the abnormal flying phenomenon sharply increases.
[0058]
FIG. 19 is a change table of the transfer separation unit for changing the charge amount of the toner on the transfer material. The transfer current (discharge current) and the post current (discharge current) are changed by changing the transfer separation condition described in FIG. 10 with four types of setting conditions S. As a result, assuming that the charge amount of the toner in the case of the setting condition S = 1 is 100, the charge amount of the toner in the setting condition S = 4 having the smallest charge amount can be modulated so as to double to about 230. ing.
[0059]
The sequence according to the flowchart of FIG. 7 is changed by the user or serviceman or automatically executed while changing the above-described transfer separation condition, so that the abnormal flight coefficient C due to the transfer separation factor is the lowest. For example, it is possible to select an image with less occurrence of the abnormal flying phenomenon, and it is possible to obtain the optimum condition in a short time.
[0060]
<Embodiment 3>
FIG. 12 is an explanatory diagram of the fixing device 36 inside the image forming apparatus shown in FIG. The fixing roller 101 incorporating the 1200 W heater 100 is configured by covering an aluminum core with a rubber layer of 300 μm and a PTFE layer of 10 μm. In the present embodiment, the heater 100 (means for setting the fixing temperature of the fixing unit) is used as one of the heat transfer mode changing units. On the other hand, the pressure roller 102 is configured by coating a 5 mm rubber layer and a 100 μm PFA layer on an iron core. A pressure roller 102 is brought into contact with the above-described fixing roller 101 from below to form a fixing nip portion N therebetween. When the fixing roller 101 and the pressure roller 102 rotate in the directions indicated by the arrows, the transfer material P is nipped and conveyed by the fixing nip N. Thus, the transfer material P is heated and pressed to fix the toner image on the surface.
[0061]
Further, a separation claw 103 abuts on the fixing roller 101 for the purpose of preventing the transfer material P from wrapping around, so that the transfer material P after fixing the toner image is smoothly conveyed to the conveying roller pair 37. Further, in order to keep the surface of the fixing roller 101 at a predetermined temperature, the thermistor 104 constantly monitors the surface temperature of the fixing roller, and the power supplied to the heater 100 is adjusted.
[0062]
A fixing entrance guide 105 is arranged on the upstream side of the fixing roller 101 along the paper passing direction (the direction of the arrow K) of the transfer material P. The fixing inlet guide 105 is supported so as to be movable in the vertical direction, and is adjusted to an appropriate height by a position changing unit 106 (for example, a cam or a solenoid). Thus, the transfer material P can be inserted at an arbitrary height into the fixing nip N between the fixing roller 101 and the pressure roller 102.
[0063]
FIG. 13 shows a heat transfer form of the fixing by the fixing unit 36 shown in the fixing unit 36 shown in FIG. 12 and the heat generated at the downstream side of the horizontal line in the paper passing direction when a horizontal line image of 8 lines and 16 spaces is output. The abnormal flying phenomenon of the toner is graphed by a numerical method described later.
[0064]
The heat transfer form is a characteristic of a calorific state of transmission to the toner on the transfer material. In this case, the fixing temperature is low, and the heating to the transfer material P is slow. The heating is applied to the material P instantaneously (for a short time). The fixing temperature can be changed by adjusting the power supplied to the heater 100 based on the surface temperature of the fixing roller 101 monitored by the thermistor 104 shown in FIG. It is empirically known that the heating speed of the transfer material P depends on the height of the fixing entrance guide shown in FIG. When the fixing entrance guide is high, the transfer material P is heated in contact with or near the fixing roller 101 before entering the fixing nip N, and when entering the fixing nip N, wind pressure, electric repulsion, and transfer It is considered that the so-called “fixation scattering” generated by the pressure of water vapor in the material can be reduced. This phenomenon has a high relevance to the heat transfer form in the fixing device 36. As shown in FIG. 20 described below, when the heat transfer form changes, the abnormal flying phenomenon rapidly changes.
[0065]
FIG. 20 is a change table for changing the heat transfer mode of the fixing device 36. There are eight types of setting conditions S, and the fixing conditions described with reference to FIG. 12 are changed to change the fixing temperature and the height of the fixing entrance guide 105. As a result, when the setting condition S = 1, the heating is performed instantaneously with the heat transfer mode being higher, and when the setting condition S = 8, the heating is changed so that the heating mode is lower and the heating is performed slowly. It is possible to make it.
[0066]
By changing the above fixing condition and executing the sequence according to the flowchart of FIG. 7 by the designation of the user or the service person or automatically, the abnormal flight coefficient C due to the fixing factor is the lowest, in other words, the abnormal It is possible to select an image with less occurrence of a flying phenomenon, and it is possible to obtain the optimum condition in a short time.
[0067]
In the present embodiment, since the fixing temperature is changed, it is necessary to set the timer shown in FIG. 7 to a time of about several tens of seconds.
[0068]
FIG. 14 is a flowchart of a subroutine for detecting an abnormal flying phenomenon used in the present embodiment. In the present embodiment, the method of detecting this by the reader scanner unit 1 attached to the image forming apparatus shown in FIG.
[0069]
First, the user or service person places the output test print on the platen glass 2 of the reader / scanner unit 1 (see FIG. 1) to use the reader / scanner unit for an ordinary copy image. Then, the transfer material P that has been test-printed at the same resolution as the method of reading the original image is read to obtain two-dimensional luminance information (S41). The size here is 101.6 mm square, which corresponds to 2400 pixels in a 600 dpi reader scanner.
[0070]
Next, the oblique arrangement according to the mounting state of the test print image in the reader scanner unit 1 is converted by a rotation process to correct the perpendicularity by reading (S42). Then, averaging is performed in the horizontal line direction, and converted into one-dimensional luminance information in the vertical direction (S43). Further, the one-dimensional luminance information in the vertical direction is averaged for every 24 pixels to obtain a line profile (S44). The one-dimensional luminance information is for repeating shading every 24 pixels for an image of 8 lines and 16 spaces. In this line profile, luminance information at six pixel positions from the center of the line density is defined as an abnormal flight coefficient D in the present embodiment (S45). The six pixels are originally white characters at a position shifted by four pixels from the center of the eight lines by four pixels, but are not a luminance signal indicated by the white characters due to an abnormal flight occurring at the trailing edge of the image, but a halftone. Will be shown.
[0071]
FIG. 15 is a view for explaining an image of 101.6 mm, 2400 pixels square read by the reader / scanner section 1, and as shown in FIG. Convert to luminance information. In the figure, a part of the luminance information is shown. Then, as shown in FIG. 17, averaging is performed for every 24 pixels to obtain a line profile. The line profile causes a clear difference in the inflection of the luminance signal due to the abnormal flight of the image forming apparatus. When the degree of the abnormal flight is good, the line profile approaches a rectangular shape. It becomes gentle. For this reason, the luminance information of the pixels separated by 6 pixels from the center of the line provides a luminance signal that is not a white character, and the abnormal flying phenomenon is faithfully converted into a numerical value and becomes an appropriate determination criterion.
[0072]
In addition, if the heat transfer mode of the fixing device 36 is used, the effects of the present embodiment can be achieved even when the nip width of the fixing nip portion N between the fixing roller 101 and the pressure roller 102 is changed. In this case, an urging member (for example, a compression spring) that presses the pressure roller 102 against the fixing roller 101 serves as a heat transfer mode changing unit.
[0073]
【The invention's effect】
As described above, according to the present invention, an image reading unit that reads an output pattern of a toner image after fixing at a resolution equal to or higher than the resolution in the sub-scanning direction of a digital exposure unit is provided. A plurality of test pattern images are formed while changing (shaking) the setting conditions of the image forming apparatus, and an abnormal flying phenomenon of toner occurring at the downstream side of the characters or lines in the test pattern in the transfer material passing direction. Is detected by the image reading means, and the optimum condition for minimizing the abnormal flying phenomenon can be automatically found.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view illustrating a schematic configuration of an image forming apparatus according to the present invention.
FIG. 2 is a diagram illustrating an electrical configuration of a control board provided in an image forming apparatus main body and an external input / output device.
FIG. 3 is a longitudinal sectional view illustrating a configuration of a contact image sensor (CIS device).
FIG. 4 is a top view illustrating a configuration of a contact image sensor (CIS device).
FIG. 5 is a longitudinal sectional view showing the configuration of an exposure apparatus (digital exposure means) and a developing device (developing means).
FIG. 6 is a diagram illustrating the relationship between the amount of applied toner on a transfer material and an abnormal flying phenomenon.
FIG. 7 is a flowchart illustrating a sequence for minimizing an abnormal flying phenomenon.
FIG. 8 is a flowchart of a subroutine for test printing.
FIG. 9 is a flowchart of a subroutine for detecting an abnormal flying phenomenon.
FIG. 10 is a longitudinal sectional view showing a configuration of a post charger and a transfer separation charger in the second embodiment.
FIG. 11 is a diagram illustrating a relationship between a charge amount of toner on a transfer material and an abnormal flying phenomenon.
FIG. 12 is a longitudinal sectional view illustrating a configuration of a fixing device and an entrance guide according to a third embodiment.
FIG. 13 is a diagram illustrating a relationship between a heat transfer form of fixing and an abnormal flying phenomenon.
FIG. 14 is a flowchart of a subroutine for detecting an abnormal flying phenomenon in the third embodiment.
FIG. 15 is a view for explaining an image of 101.6 mm and 2400 pixels square read by the reader scanner unit in the third embodiment.
16 is a diagram illustrating one-dimensional luminance information in a vertical direction according to Embodiment 3. FIG.
FIG. 17 is a diagram illustrating a line profile according to the third embodiment.
FIG. 18 is a diagram illustrating a change in the amount of applied toner when the bright portion potential on the photosensitive drum, the DC component of the developing bias of the developing device, and the peripheral speed ratio of the developing sleeve are changed.
FIG. 19 is a diagram illustrating a change in the charge amount of the toner when the transfer current of the transfer charger and the post current of the post charger are changed.
FIG. 20 is a diagram illustrating a change in the heat transfer form of fixing when the fixing temperature of the fixing unit and the height of the fixing entrance guide are changed.
[Explanation of symbols]
1 Image reading means (reader scanner unit)
26 Image carrier (photosensitive drum)
29 Developing means (toner applied amount changing means, developing device)
29a Developing sleeve
30 Post charger (toner charge amount changing means)
31 Transfer separation unit (toner charge amount changing unit, transfer charger)
32 Transfer separation means (separation charger)
32 Transfer separation means
36 Fixing means (fixer)
41a control means (CPU)
42 Digital exposure means (toner application amount changing means, exposure apparatus)
50 Image reading means (CIS device)
100 Heat transfer mode changing means (heater)
105 Fixing entrance guide
106 heat transfer mode changing means (position changing means)
K Sub-scanning direction (paper passing direction)
P transfer material

Claims (6)

The uniformly charged surface of the image carrier is exposed by digital exposure means to form an electrostatic latent image, and toner is adhered to the electrostatic latent image by developing means to be developed as a toner image, and transferred and separated by transfer and separation means. An image forming apparatus that transfers the toner image to a transfer material and fixes the toner image on the transfer material by a fixing unit.
A toner applied amount changing unit for changing an applied amount of toner on the transfer material before fixing,
Control means for controlling the applied toner amount changing means;
Image reading means for reading the output pattern of the toner image after fixing at a resolution equal to or higher than the resolution in the sub-scanning direction of the digital exposure means,
The control means controls the applied toner amount changing means to fix test pattern images having different applied toner amounts on one or a plurality of transfer materials. At this time, the transfer material passing direction in the plurality of test pattern images is used. A difference in the abnormal flying phenomenon of the toner occurring on the downstream side is detected by the image reading unit, and an optimal condition for the amount of applied toner is determined by the control unit based on the detection result;
An image forming apparatus comprising: The toner application amount changing unit includes a unit that changes a surface potential of the image carrier, a unit that changes a developing bias applied to the developing unit during development, and a unit that changes a peripheral speed of a developing sleeve of the developing unit. At least one of
The image forming apparatus according to claim 1, wherein: The uniformly charged surface of the image carrier is exposed by digital exposure means to form an electrostatic latent image, and toner is adhered to the electrostatic latent image by developing means to be developed as a toner image, and transferred and separated by transfer and separation means. An image forming apparatus that transfers the toner image to a transfer material and fixes the toner image on the transfer material by a fixing unit.
Toner charge amount changing means for changing the charge amount of the toner on the transfer material before fixing,
Control means for controlling the toner charge amount changing means,
Image reading means for reading the output pattern of the toner image after fixing at a resolution equal to or higher than the resolution in the sub-scanning direction of the digital exposure means,
The control means controls the toner charge amount changing means to fix test pattern images having different toner charge amounts on one or a plurality of transfer materials, and at this time, the transfer material passing direction in the plurality of test pattern images A difference in the abnormal flying phenomenon of the toner occurring on the downstream side is detected by the image reading unit, and an optimal condition for the toner charge amount is determined by the control unit based on the detection result.
An image forming apparatus comprising: The toner charge amount changing unit is a transfer separation unit, and the transfer separation unit changes a discharge current;
The image forming apparatus according to claim 3, wherein: The uniformly charged surface of the image carrier is exposed by digital exposure means to form an electrostatic latent image, and toner is adhered to the electrostatic latent image by developing means to be developed as a toner image, and transferred and separated by transfer and separation means. In an image forming apparatus that transfers the toner image to a transfer material and fixes the toner image on the transfer material by a fixing unit, when the toner image is fixed by the fixing unit, a heat transfer form of the fixing unit to the transfer material is changed. Heat transfer mode changing means for changing;
Control means for controlling the heat transfer mode changing means,
Image reading means for reading the output pattern of the toner image after fixing at a resolution equal to or higher than the resolution in the sub-scanning direction of the digital exposure means,
The control means controls the heat transfer form changing means to fix test pattern images having different heat transfer forms on one or a plurality of transfer materials. At this time, in the plurality of test pattern images, downstream of the transfer material passing direction. A difference in the abnormal flying phenomenon of the toner occurring on the side is detected by the image reading unit, and an optimal condition for the heat transfer mode is determined by the control unit based on the detection result.
An image forming apparatus comprising: The heat transfer mode changing unit includes a unit that sets a fixing temperature of the fixing unit, a unit that changes a nip width of a fixing nip, and a position of a fixing entrance guide that guides the transfer material to the fixing nip of the unit. At least one of the means for
The image forming apparatus according to claim 5, wherein:

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