JP6882911B2 - Developing device, image forming device, image processing device, and image forming method - Google Patents

Description

The present invention relates to a developing apparatus, an image forming apparatus and an image processing apparatus, and an image forming method for printing by changing the process speed according to the type of paper.

Conventionally, in an image forming apparatus, there is a technique of controlling a paper transport speed and a heating temperature at the time of fixing according to the type of paper used. For example, Patent Document 1 discloses that when the paper is thick paper (or OHP sheet), the paper transport speed is slower than that of normally used plain paper, that is, the process speed is slowed down.

Comparing the case where the toner is fixed on the plain paper and the case where the toner is fixed on the thick paper, it is necessary to heat the thick paper more. Therefore, when thick paper is used, the paper passing speed is slowed down so that the paper is sufficiently heated by the fixing device. In this case, since it is difficult to slow down the paper passing speed only by the fixing step, it is necessary to slow down the process speed in the entire process including other steps such as the developing step.

If the process speed is slowed down when using thick paper in this way, the fixing process can be performed well, but in the developing process, the amount of toner adhering to the photoconductor drum (on the primary transfer) changes, and the amount of toner adhering to thick paper becomes plain paper. It is more than the amount of toner attached to. Regarding this, it is generally considered to reduce the applied voltage (DC component) of the development bias when using thick paper to suppress the amount of toner adhered.

However, even if the applied voltage (DC component) of the development bias is changed between when plain paper is used and when thick paper is used to make the amount of toner adhered uniform, the print quality is not always the same. Patent Document 2 discloses that when the process speed is slowed down when using thick paper, fog is suppressed by increasing the frequency of the developing AC bias and further increasing the peak-to-peak of the developing AC bias. There is.

Japanese Unexamined Patent Publication No. 8-305218 JP-A-2007-121906 Japanese Unexamined Patent Publication No. 2016-161772

However, regarding print quality, there is a problem of fine line reproducibility. The conventional method of changing the applied voltage (DC component) of the development bias between when using plain paper and when using thick paper solves the problem of the amount of toner adhering, but the printing width of thin lines when using plain paper and when using thick paper. Rather than not solving the problem of fine line reproducibility, such as the difference in thin line reproducibility, the fine line reproducibility when using thick paper is further lowered as compared with when using plain paper.

The invention disclosed in Patent Document 2 has an effect of suppressing fog, but does not solve the problem of fine line reproducibility such that the print width of fine lines differs between when plain paper is used and when thick paper is used.

The present invention has been made in view of the above problems, and in an image forming apparatus that changes the process speed according to the type of paper, a developing apparatus that has the same print quality even if the process speeds are different. , An image forming apparatus, and an image forming method.

In order to solve the above problems, the present invention is an image forming apparatus having a first printing mode and a second printing mode having a process speed slower than that of the first printing mode, and the developing apparatus and photosensitivity. The development bias applied between the body drum and the body drum is a bias voltage formed by superimposing an AC component on the DC component, and the DC component of the development bias in the first print mode and the development in the second print mode. It is the same as the DC component of the bias, and the duty of the AC component of the development bias in the second print mode is set lower than the duty of the AC component of the development bias in the first print mode. It is supposed to be.

According to the above configuration, in the second print mode, an increase in image density due to slowing the process speed and a decrease in image density due to reducing the duty of the AC component are balanced. As a result, even in the second printing mode of the thick paper printing mode in which the process speed is slow, it is possible to obtain the same image density as in the first printing mode. Further, the thickness of the thin line in the second print mode can be set to the same thickness as in the first print mode, and the fine line reproducibility can be improved.

Further, in the image forming apparatus, the point of decrease in the "duty of the AC component in the second printing mode" with respect to the "duty of the AC component in the first printing mode" exceeds minus 0% and is minus. It is preferably set in the range of 20% or less, and more preferably set in the range of -5% or more and -15% or less.

Further, in the image forming apparatus, the first printing mode is a printing mode when plain paper is used as the recording paper, and the second printing mode is thick paper having a larger basis weight than plain paper as the recording paper. It is possible to configure the print mode when using.
Further, in the image forming apparatus, the same process speed can be applied to the same printing mode.

Further, in the image forming apparatus, since the density adjustment can be performed only by adjusting the duty, the development bias adjusted according to the process control of either the first printing mode or the second printing mode. It is also possible to have a configuration in which the DC component of is taken over as it is even after switching to the other print mode. Then, if there is no difference in the DC components of the development bias, it is possible to obtain the same level of print quality in the first print mode and the second print mode.

In the image forming apparatus, since the density adjustment can be performed only by adjusting the duty, the direct current of the development bias adjusted according to the process control of either the first printing mode or the second printing mode. It was explained that the components can be inherited as they are even after being switched to the other print mode, but the difference in direct current between the print modes due to the different duty applied to each print mode is used. You may try to compensate.

In the second printing mode, the image forming apparatus of the present invention balances an increase in image density by slowing down the process speed and a decrease in image density by reducing the duty of the AC component. As a result, it is possible to obtain the same level of print quality in the first print mode and the second print mode.

It is a conceptual sectional view of the multifunction device according to the 1st Embodiment of this invention. It is a functional block diagram of the multifunction device according to the 1st Embodiment of this invention. It is a figure explaining the image formation process in the image formation apparatus of FIG. 1 and FIG. It is a perspective view which shows the driving part of a part of the developing apparatus and a photoconductor drum in the image forming apparatus of FIG. 1 and FIG. It is a waveform diagram which shows the voltage waveform of the development bias by embodiment of this invention. It is a block diagram which shows the control system for performing the switching control between the plain paper printing mode and the thick paper printing mode according to the embodiment of this invention. It is a flowchart explaining the switching timing between the plain paper printing mode and the thick paper printing mode by the embodiment of this invention. It is a table which shows the experimental result about the toner adhesion amount measurement in the plain paper printing mode and the thick paper printing mode by embodiment of this invention. It is a table which shows the experimental result about the fine line reproducibility in a plain paper printing mode and a thick paper printing mode.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
The first embodiment relates to the multifunction device 800 including the image forming apparatus according to the second and subsequent embodiments. 1, FIG. 2 and FIG. 3 show the configuration of the multifunction device 800 and the like.

As shown in FIGS. 1 and 2, the multifunction device 800 includes a document reading device 820 that reads an image of a document, a multifunction device main body (image forming unit main body) 830 that forms an image on a sheet, and a document reading device 820 and a composite. It includes an operation panel unit 843 for operating the machine main body 830, and an arithmetic processing unit 841 that controls the document reading device 820 and the multifunction device main body 830 based on the operation by the operation panel unit 843.

In addition to using the document reading device 820 as a single unit for image reading and using the multifunction device main body 830 as a single unit for image formation, these can also be linked to copy an image. Further, the multifunction device 800 may include a storage device and a facsimile machine (not shown). The storage device can store the image read by the document reading device 820 and the image received by the facsimile machine. The facsimile machine can transmit the image read by the document reading device 820 and the image stored in the storage device, and can receive the image from the outside. Further, the multifunction device 800 may include an interface for connecting to a personal computer via a network. The personal computer connected to the multifunction device 800 can use the function of the multifunction device for the data that can be managed by the personal computer.

The document reading device 820 includes a document automatic feeding unit SPF (Single Pass Feeder) 824 for automatically feeding the document, and a scanning device main body 822 for reading the image of the document. In addition to the components shown in FIG. 2, the document reading device 820 also includes components not shown in FIG. 2 but shown in FIG. Further, as shown in FIG. 1, the reading device main body 822 is provided with a document base 826.

The multifunction device main body 830 includes a sheet feeding unit 10 that feeds the sheet, a manual feeding unit 20 that can manually feed the sheet, and a sheet that is fed by the sheet feeding unit 10 or the manual feeding unit 20. An image forming unit 30 for forming an image is provided.

The sheet feeding section 10 includes a sheet loading section 11 for loading sheets and a separate feeding section 12 for separately feeding the sheets loaded on the sheet loading section 11 one by one. The seat loading portion 11 includes a middle plate 14 that rotates about a rotation shaft 13, and the middle plate 14 rotates when feeding the seat to lift the seat upward. The separate feeding unit 12 includes a pickup roller 15 for feeding the sheet lifted by the middle plate 14, and a separation roller pair 16 for separating the sheets fed by the pickup roller 15 one by one. ..

The manual feed feeding unit 20 includes a manual feed tray 21 capable of loading sheets and a separate feeding unit 22 for separately feeding the sheets loaded on the manual feed tray 21 one by one. The manual feed tray 21 is rotatably supported by the main body 830 of the multifunction device, and when manually feeding and feeding, the sheet can be loaded by fixing the manual feed tray 21 at a predetermined angle. The separation feeding unit 22 includes a pickup roller 23 that feeds the sheets loaded on the manual feed tray 21, a separation roller 24 and a separation pad 25 that separate the sheets fed by the pickup roller 23 one by one. I have.

The image forming unit 30 includes four process cartridges 31Y to 31K for forming images of yellow (Y), magenta (M), cyan (C), and black (K), and photoconductor drums 213Y to 213K, which will be described later. 211, a transfer unit (transfer means) 216 for transferring the toner image formed on the surface of the photoconductor drums 213Y to 213K to the sheet, and a fixing unit 34 for fixing the transferred toner image to the sheet. And have. The alphabet (Y, M, C, K) attached to the end of the code indicates each color (yellow, magenta, cyan, black).

Each of the four process cartridges 31Y to 31K is configured to be removable from the multifunction device main body 830 and is replaceable. Since the four process cartridges 31Y to 31K have the same configuration except that the colors of the images to be formed are different, only the configuration of the process cartridge 31Y forming the yellow (Y) image will be described, and the process cartridge 31M will be described. The description of ~ 31K will be omitted.

The process cartridge 31Y includes a photoconductor drum 213Y as an image carrier, a charger 215Y for charging the photoconductor drum 213Y, a developing device 212Y for developing an electrostatic latent image formed on the photoconductor drum 213Y, and photosensitivity. A drum cleaner 214 for removing toner remaining on the surface of the body drum 213Y is provided. The developing device 212Y includes a developing device main body (not shown in detail) for developing the photoconductor drum 213Y, and a toner cartridge (not shown in detail) for supplying toner to the developing device main body. The toner cartridge is configured to be removable from the main body of the developing device, and when the stored toner is exhausted, the toner cartridge can be removed from the main body of the developing device and replaced.

The exposure apparatus 211 includes a light source for irradiating the laser beam (not shown), a plurality of mirrors (not shown) for guiding the laser beam to the photoconductor drums 213Y to 213K, and the like. The transfer unit 216 is a primary transfer roller that primarily transfers the toner images formed on the photoconductor drums 213Y to 213K to the intermediate transfer belt 221 and the intermediate transfer belt 221 that carries the toner images formed on the photoconductor drums 213Y to 213K. It includes 217Y to 217K, a secondary transfer roller 37 that secondarily transfers the toner image transferred to the intermediate transfer belt 221 to a sheet, and a belt cleaner 38 that removes the toner remaining on the intermediate transfer belt 221. The intermediate transfer belt 221 is hung on the driving roller 39a and the driven roller 39b, and is pressed against the photoconductor drums 213Y to 213K by the primary transfer rollers 217Y to 217K. The secondary transfer roller 37 nips (sandwiches) the intermediate transfer belt 221 with the drive roller 39a, and transfers the toner image carried by the intermediate transfer belt 221 to the sheet at the nip portion N. The fixing portion 34 includes a heating roller 34a that heats the sheet and a pressure roller 34b that presses against the heating roller 34a. The primary transfer rollers 217 (217Y to 217K) are supplied with power from the power supply 218.

The operation panel unit 843 includes a display unit 845 that displays predetermined information, and an input unit 847 that allows the user to input instructions to the document reading device 820 and the multifunction device main body 830. In the present embodiment, the operation panel unit 843 is arranged on the front side of the reading device main body 822. The front side corresponds to the front side of the paper surface of FIG. 1, and the back side corresponds to the back side of FIG.

As shown in FIG. 2, the arithmetic processing unit 841 includes a CPU 841a that drives and controls a sheet feeding unit 10, a manual feeding unit 20, an image forming unit 30, and a document reading device 820, and various programs for operating the CPU 841a. It includes a memory 841b for storing various information and the like used by the CPU 841a. The arithmetic processing unit 841 integrates and controls the operations of the sheet feeding unit 10, the manual feeding unit 20, the image forming unit 30, and the document reading device 820 based on the operation of the operation panel unit 843 by the user. Let the sheet form an image.

Next, an image forming operation (image forming control by the arithmetic processing unit 841) by the multifunction device 800 configured as described above will be described. In the present embodiment, the image forming unit 30 forms the image of the scanned document fed by the document automatic feeding unit 824 and read by the reading device main body 822 on the sheet fed by the sheet feeding unit 10. An image forming operation will be described as an example.

When the image formation start signal is transmitted by the input to the input unit 847 of the operation panel unit 843 by the user, the scanned document placed on the document automatic feeding unit 824 by the user is automatically directed toward the document reading position. The image is fed and the image is read by the reading device main body 822 at the document reading position.

When the image of the original document is read by the scanning apparatus main body 822, the exposure apparatus 211 irradiates the photoconductor drums 213Y to 213K with a plurality of corresponding laser beams based on the image information of the scanned document. At this time, the photoconductor drums 213Y to 213K are precharged by the chargers 215Y to 215K, respectively, and the corresponding electrostatic latent laser beams are irradiated on the photoconductor drums 213Y to 213K. An image is formed. After that, the electrostatic latent images formed on the photoconductor drums 213Y to 213K are developed by the developing devices 212Y to 212K, and yellow (Y), magenta (M), and cyan (C) are developed on the photoconductor drums 213Y to 213K. ) And black (K) toner images are formed. The toner images of each color formed on the photoconductor drums 213Y to 213K are superimposed and transferred to the intermediate transfer belt 221 by the primary transfer rollers 217Y to 217K, and the superimposed transferred toner image (full-color toner image) is the intermediate transfer belt. It is conveyed to the nip portion N while being carried on the 221.

In parallel with the image forming operation described above, the sheets loaded on the sheet loading section 11 are fed to the sheet transport path 26 by the pickup roller 15 while being separated one by one by the separate feeding section 12. Then, the resist roller pair 27 located upstream in the sheet transport direction of the nip portion N corrects the skew and transports the nip portion N to the nip portion N at a predetermined transport timing. A full-color toner image carried by the intermediate transfer belt 221 is transferred to the sheet conveyed to the nip portion N by the secondary transfer roller 37.

The sheet on which the toner image is transferred is heated and pressurized by the fixing portion 34 to melt and fix the toner image, and is discharged to the outside of the device by the discharge roller pair 18. The sheet discharged to the outside of the device is loaded on the discharge sheet loading unit 19.

When an image is formed on both sides (first surface and second surface) of the sheet, the discharge roller pair 18 is rotated in the reverse direction before the sheet on which the image is formed on the first surface is discharged to the outside of the apparatus. It is conveyed to the double-sided transport path 17, and is re-conveyed to the image forming unit 30 via the double-sided transport path 17. Then, as with the first surface, an image is formed on the second surface and discharged to the outside of the device. The sheet discharged to the outside of the device is loaded on the discharge sheet loading unit 19.

[Second Embodiment]
In the image forming apparatus 100, when thick paper is used as the recording paper, the process speed is slower than when plain paper is used (the paper transport speed in the printing process and the rotation speed of the intermediate transfer belt 21 are slower). It is set. This is because the amount of heat for fixing the toner image on the thick paper is required to be larger than the amount of heat for fixing the toner image on the plain paper, and the amount of heat for that purpose is secured in the fixing device 17. If the recording paper requires a larger amount of heat for fixing than plain paper, the process speed will be slowed down even if the paper is other than thick paper (for example, an OHP sheet).

That is, the image forming apparatus 100 according to the present embodiment has at least two printing modes in which the process speeds are different from each other. In the following description, the image forming apparatus 100 has a plain paper printing mode (first printing mode) and a thick paper printing mode (second printing mode) whose process speed is slower than that of the plain paper printing mode. It will be explained as a thing. Here, paper having a basis weight value of 105 g / m ² or less is defined as plain paper, and paper having a basis weight value ^{of more than 105 g / m 2} is defined as thick paper.

In the plain paper printing mode and the thick paper printing mode, the thick paper printing mode has a slower process speed in the developing process. The present embodiment is characterized in that the development bias is controlled according to the process speed, the change in development due to the difference in the process speed is suppressed, and the print quality in the plain paper printing mode and the thick paper printing mode is made uniform. Has. Hereinafter, this feature will be described in detail.

FIG. 4 is a perspective view showing a part of the developing device 212 (developing devices 212Y, 212M, 212C, 212K shown in FIG. 1) and a driving unit of the photoconductor drum 213. Here, the developing device 212 illustrates a developing device using a non-magnetic two-component developing agent, and FIG. 4 shows only the magnet roller 212A included in the developing device 212 (the developing agent tank and the like are not shown). ). Specifically, the magnet roller 212A is composed of a cylindrical developing sleeve arranged so as to face the photoconductor drum 213 at a predetermined interval, and a magnet fixedly arranged on the inner peripheral side of the developing sleeve. .. The developing sleeve and the photoconductor drum 213 are rotationally driven by the motors 251 and 252, respectively. Further, a development bias is applied between the development sleeve and the photoconductor drum 213 by the development bias power supply 219. As shown in FIG. 5, this development bias is a bias voltage formed by superimposing an alternating current (AC) component on a direct current (DC) component. In the example of FIG. 5, an AC bias having a duty Duty of t (−) / T is superimposed on a DC bias of minus Vdc volt.

The image forming apparatus 100 according to the present embodiment is characterized in that the duty of the AC component of the development bias is changed between the plain paper printing mode and the thick paper printing mode. Specifically, the duty of the AC component in the thick paper printing mode in which the process speed is slow is made smaller than the duty of the AC component in the plain paper printing mode. Further, the direct current component (Vdc) of the development bias is not changed.

By applying the development bias as shown in FIG. 5, the electrostatic latent image on the surface of the photoconductor drum 213 is developed by the toner while the toner reciprocates between the developing sleeve and the photoconductor drum 213. At this time, the smaller the duty of the AC component of the development bias, the smaller the amount of toner adhered to the photoconductor drum 213, and the lower the image density.

In the image forming apparatus 100 according to the present embodiment, in the thick paper printing mode, the process speed is slowed down (the development time per unit area is lengthened) to increase the image density and reduce the duty of the AC component. This is balanced with the decrease in image density. As a result, even in the thick paper printing mode in which the process speed is slow, the same image density as in the plain paper printing mode can be obtained. Further, the thickness of the thin line in the thick paper printing mode can be set to the same thickness as that in the plain paper printing mode, and the fine line reproducibility can be improved.

Further, in the image forming apparatus 100 according to the present embodiment, since the DC component of the development bias is the same in the plain paper printing mode and the thick paper printing mode, the process control can be executed in the same manner in both printing modes. it can. The process control here means a control for keeping the image density constant by appropriately adjusting the DC component of the development bias during continuous printing or the like. For example, if process control is performed while using in plain paper printing mode and then switched to thick paper printing mode in that state, the DC component of the development bias is not changed and the adjusted density by process control is inherited as it is. Printing becomes possible. That is, the DC component of the development bias changed by performing the process control in either the plain paper printing mode or the thick paper printing mode can be inherited as it is even after being switched to the other printing mode.

FIG. 6 is a block diagram showing a control system for performing switching control between a plain paper printing mode and a thick paper printing mode in the image forming apparatus 100 according to the present embodiment. As shown in FIG. 6, the control system includes a process speed control unit 61, a paper determination unit 62, a memory 63, a motor control unit 64, and a power supply control unit 65. In the switching between the plain paper printing mode and the thick paper printing mode, the process speed control unit 61 is used not only for the means related to development but also for all means related to the image forming process such as exposure / transfer / fixing / paper transport. Control process speed. However, here, only the control part of the means related to development is illustrated. Further, the process speed control unit 61 is composed of hardware, software, or a combination thereof.

The paper determination unit 62 determines the type of recording paper to be used, and notifies the process speed control unit 61 of the determination result. The determination here is performed by, for example, the following method (A) or (B).

(A) When the user selects a paper type, the paper type is determined based on this selection input signal.

(B) A thickness sensor for detecting the thickness of the recording paper is provided, and the paper type is determined based on the detection signal of the thickness sensor.

The process speed control unit 61 controls switching between the plain paper printing mode and the thick paper printing mode based on the paper determination result notified from the paper determination unit 62. Specifically, the rotation speeds of the motors 251 and 252 are controlled via the motor control unit 64, and the development bias is controlled by the development bias power supply 219 via the power supply control unit 65. As described above, the development bias control in this case is a control for changing the duty of the AC component of the development bias. The control value for performing the above control is stored in the memory 63 in advance, and is read from the memory 63 by the process speed control unit 61.

Next, in the image forming apparatus 100 according to the present embodiment, the switching timing between the plain paper printing mode and the thick paper printing mode will be described with reference to the flowchart of FIG.

First, when a print request for a copy or print job is issued (S1), it is determined whether the type of recording paper used in the job is plain paper or thick paper (S2). Then, it is determined whether or not the paper type determined in S2 is the same as the paper type in the immediately preceding job (S3). If they are the same (YES in S3), the job output is executed without changing the duty value from the setting as it is (S4). On the other hand, if they are not the same (NO in S3), the duty value is changed and the job output is executed (S5). That is, in S5, if the immediately preceding job is plain paper and the new job is thick paper, the duty corresponding to the plain paper printing mode is changed to the duty corresponding to the thick paper printing mode. If the immediately preceding job is thick paper and the new job is plain paper, the duty corresponding to the thick paper printing mode is changed to the duty corresponding to the plain paper printing mode. When the image forming apparatus 100 is started, the duty of the AC component of the development bias is first set to the duty corresponding to the plain paper printing mode.

In order to confirm the effect of the present invention, the toner adhesion amount measurement and the fine line reproducibility in the plain paper printing mode and the thick paper printing mode were tested and evaluated. In the experiment, the duty of the AC component of the development bias was made different between the plain paper printing mode and the thick paper printing mode. The experimental conditions are as follows.

(Measurement of toner adhesion)
Measuring method: Develop using a color multifunction device (trade name: MX-5140FN, manufactured by Sharp Corporation) as a developing device, measure the weight by sucking the toner on the primary transfer, and measure the toner per unit area. The weight was taken as the amount of toner adhered.

(Thin line reproducibility)
Measurement method: A one-line image in the main scanning direction created at 600 dpi was output, a detailed image was taken with a microscope, and the line width was measured from the image.

(Paper type)
For plain paper, a basis weight value of 90 g / m ² (trade name: Color Copy 90 g, manufactured by Mondi) was used, and for thick paper, a basis weight value of 250 g / m ² (trade name: Color Copy 250 g, manufactured by Mondi) was used.

The experimental results are shown in FIGS. 8 and 9. These figures show the effect on the image quality of the printed image by slowing down the process speed in the thick paper printing mode by changing the duty of the AC component of the development bias between the plain paper printing mode and the thick paper printing mode. Indicates that it is decreasing.

First, if the duty is the same, the toner adhesion amount in the thick paper mode is larger than the toner adhesion amount in the plain paper mode. For example, when the duty is 70%, the toner adhesion amount in the plain paper mode is 0.38 mg / cm ² , whereas the toner adhesion amount in the cardboard mode is 0.41 mg / cm ² .

Further, in the plain paper mode, the amount of toner adhered increases as the detail is increased. For example, for the plain paper mode, when the duty is 62%, the toner adhesion amount is 0.35 mg / cm ² , whereas when the duty is 70%, the toner adhesion amount is 0.38 mg / cm ^2. Is. Further, for the cardboard mode, when the duty is 62%, the toner adhesion amount is 0.38 mg / cm ² , whereas when the duty is 70%, the toner adhesion amount is 0.41 mg / cm ² . is there.

Therefore, in order to make the toner adhesion amount equal to 0.38 mg / cm ² in the plain paper mode and the thick paper mode, the duty is set to 70% for the plain paper mode, and more than this for the thick paper mode. The duty, which is 8 points less, may be set to 62%.

Here, as shown in FIG. 8, the relationship between the duty and the adhesion amount is a linear relationship in both the plain paper mode and the thick paper mode, and since both inclinations are almost equal, it is normal for an arbitrary adhesion amount. If the duty in the paper mode is determined, it can be seen that in the thick paper mode, the adhesion amount can be made uniform in both modes by setting the duty 8 points less than that. Therefore, in order to make the amount of adhesion uniform, it is sufficient to use the PWM signal in the thick paper mode in which the offset adjustment by 8 points is reduced to the PWM control signal reflecting the density in the plain paper mode.

Further, referring to FIG. 9 for comparing the thin line widths, the fine line widths in the thick paper printing mode are increased as compared with the plain paper printing mode. Further, as the duty is increased, the fine line width is increased. As a result, it can be seen that it is effective in reducing the change in the fine line width by reducing the duty of the AC component of the development bias in the thick paper printing mode and reducing the influence on the image quality of the printed image. ..

Next, the method of adjusting the line width will be described. First, design the image quality in plain paper mode. At that time, although it depends on the required image quality level and the toner consumption, the line width of about 80 to 100 μm is often the design target. As is clear from FIG. 9, the duty setting corresponding to 80 to 100 μm in the plain paper mode is designed to be approximately 50 to 80% (when it exceeds 80%, the effect of the AC bias diminishes and the line is reversed. The width becomes narrower.)
In the embodiment shown in FIG. 9, it is shown that the duty designed in the plain paper mode is 70%, and the same line width is reproduced in the thick paper mode by about 60%. However, in general, the optimum value of duty changes depending on the image quality formation conditions.

In addition, other methods for adjusting the duty will be described. Once the mode is determined, the table that holds the duty-to-adhesion correspondence in that mode and / or the table that holds the line width-to-duty correspondence is referred to. For example, once the target adhesion amount is determined, the duty corresponding to the adhesion amount is acquired from the table of the correspondence relationship between the adhesion amount and the duty, and this is set as the duty of the PWM signal. Further, when the target line width is determined, the duty corresponding to the line width is acquired from the table of the correspondence relationship between the line width and the duty, and the duty corresponding to the line width is set as the duty of the PWM signal.

Further, for example, the amplitude adjustment of the AC bias described in Patent Document 3 can be combined with the above-mentioned duty adjustment. For example, in order to realize the target line width and the amount of adhesion, not all corrections may be made only by the duty, but a part may be adjusted by the duty and the rest may be adjusted by the amplitude of the AC bias. By combining these, it is possible to make the thickness of the thin line thicker. Further, the line width may be adjusted on one side of the duty adjustment and the AC bias amplitude adjustment, and the adhesion amount may be adjusted on the other side. The line width may be adjusted mainly on one side of the duty adjustment and the AC bias amplitude adjustment, and the adhesion amount may be mainly adjusted on the other side.

An image processing device including only a part of the functions of the multifunction device shown as an example above, or an image processing device having functions added to the above-mentioned multifunction device, which includes an image forming device, is also an embodiment of the present invention. included.

The above image forming apparatus can be realized by hardware, software, or a combination thereof. Further, the image forming method performed by the above-mentioned image forming apparatus can also be realized by hardware, software, or a combination thereof. Here, what is realized by software means that it is realized by a computer reading and executing a program.

Programs can be stored and supplied to a computer using various types of non-transitory computer readable media. Non-transitory computer-readable media include various types of tangible storage media. Examples of non-temporary computer-readable media include magnetic recording media (eg, flexible disks, magnetic tapes, hard disk drives), magneto-optical recording media (eg, magneto-optical disks), CD-ROMs (Read Only Memory), CD- R, CD-R / W, semiconductor memory (for example, mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, RAM (random access memory)) are included. The program may also be supplied to the computer by various types of transient computer readable media. Examples of temporary computer-readable media include electrical, optical, and electromagnetic waves. The temporary computer-readable medium can supply the program to the computer via a wired communication path such as an electric wire and an optical fiber, or a wireless communication path.

The present invention can be practiced in various other ways without departing from its spirit or key features. Therefore, the above examples are merely exemplary in all respects and should not be construed in a limited way. The scope of the present invention is shown by the scope of claims, and is not bound by the text of the specification. Furthermore, all modifications and modifications that fall within the equivalent scope of the claims are within the scope of the present invention.

The present invention can be applied to an image forming apparatus or an image processing apparatus.

16 Transfer unit 17 Fixing device 21 Intermediate transfer belt 23 Secondary transfer device 24 Drum cleaner 61 Process speed control unit 62 Paper determination unit 63 Memory 64 Motor control unit 65 Power supply control unit 100 Image forming device 110 Main unit 120 Document reader 130 Document Conveyor device 211 Exposure device 212 Developer 212A Magnet roller 213 Photoreceptor drum 214 Drum cleaner 215 Charger 216 Transfer unit (transfer means)
217 Primary transfer roller 218 Power supply 219 Development bias power supply 251, 252 Motor

Claims (7)

A developing apparatus used in an image forming apparatus having a first printing mode and a second printing mode having a process speed slower than that of the first printing mode.
The development bias applied between the developing device and the photoconductor drum is a bias voltage formed by superimposing an AC component on a DC component.
The DC component of the development bias in the first print mode and the DC component of the development bias in the second print mode are the same.
The duty of the AC component of the development bias in the second print mode is set lower than the duty of the AC component of the development bias in the first print mode .
When switching from one print mode to the other print mode in the first print mode and the second print mode, the duty of the AC component in one print mode set at the time of switching is obtained in advance. By increasing or decreasing the value of the difference between the duty of the AC component in the first printing mode and the duty of the AC component in the second printing mode with respect to the same line width or the same amount of toner adhered, the other printing mode A developing apparatus characterized in that the duty of an AC component in the above is set. The developing apparatus according to claim 1.
In the image forming apparatus, the reduction point of the duty of the AC component in the second printing mode with respect to the duty of the AC component in the first printing mode is set in the range of more than 0% and 20% or less. A developing device characterized by being present. The developing apparatus according to claim 1 or 2.
The first print mode is a print mode when plain paper is used as the recording paper.
The second printing mode is a developing apparatus in which a thick paper having a basis weight larger than that of plain paper is used as the recording paper. The developing apparatus according to any one of claims 1 to 3.
A developing apparatus characterized in that printing is performed at the same process speed in each of the first printing mode and the second printing mode. The developing apparatus according to any one of claims 1 to 4.
Process control that changes the DC component of the development bias is possible,
The feature is that the DC component of the development bias determined by performing the process control in either the first print mode or the second print mode is inherited as it is even after switching to the other print mode. Development equipment. An image forming apparatus comprising the developing apparatus according to any one of claims 1 to 5. An image forming method used in an image forming apparatus having a first printing mode and a second printing mode having a process speed slower than that of the first printing mode.
The development bias applied between the developing device and the photoconductor drum is a bias voltage formed by superimposing an AC component on a DC component.
The DC component of the development bias in the first print mode and the DC component of the development bias in the second print mode are the same.
The duty of the AC component of the development bias in the second print mode is set lower than the duty of the AC component of the development bias in the first print mode .
When switching from one print mode to the other print mode in the first print mode and the second print mode, the duty of the AC component in one print mode set at the time of switching is obtained in advance. By increasing or decreasing the value of the difference between the duty of the AC component in the first printing mode and the duty of the AC component in the second printing mode with respect to the same line width or the same amount of toner adhered, the other printing mode An image forming method characterized in that the duty of an AC component in the above is set.

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