JP3605783B2 - Image forming device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus that forms an image based on an image signal, a so-called digital image forming apparatus, and more particularly, to an image forming apparatus in which a pixel density can be switched. Such an image forming apparatus can be used for a copying machine, a printer, a facsimile, and the like.
[0002]
[Prior art]
Multifunctional machines having functions such as copiers, printers, and facsimile machines, so-called multifunction machines, have been developed and widely used by so-called digital image forming techniques. Multifunction devices have functions that can respond to various needs. One of these functions is pixel density switching.
[0003]
Pixel density switching function is a function that can switch the number of pixels per unit area, when used as a copier, when used as a printer, when used as a facsimile, the pixel density is switched according to the purpose of use, Further, when used as a printer, the function is a function of switching the pixel density in accordance with the designation of the pixel density from the computer. In the image recording apparatus, the pixel density in the main scanning direction is switched by switching the frequency of the recording signal, and the pixel density in the sub-scanning direction is switched by switching the rotation speed of the photosensitive drum.
[0004]
As described above, in the conventional image forming apparatus, the rotation speed of the photosensitive drum is switched mainly corresponding to the pixel density switching.
[0005]
[Problems to be solved by the invention]
When the rotation speed of the photosensitive drum is changed, the developing property of the developing device needs to be changed accordingly. The applicant has proposed in Japanese Patent Application No. 7-309182 a method of setting the developability of a developing device to an optimum point. This developing property adjusting method develops a reference latent image formed on a photoreceptor by changing a rotation speed of a developing sleeve of a developing device to form a plurality of toner images, and a toner having a density reaching a target density. This is a method of selecting the rotation speed of the developing sleeve corresponding to the image.
[0006]
This method is an extremely excellent method for adjusting the developing property in that the developing property can be adjusted with high accuracy and there is no undesired phenomenon such as fogging. However, this developing property adjustment method has a problem that the adjustment takes time. For example, if this developing property adjustment method is executed during a printing operation or between one printing operation and a subsequent printing operation, the printing efficiency is reduced.
[0007]
SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of performing a developing property adjustment in a short time and having a developing property adjusting function capable of performing a high-precision developing property adjustment. It is intended to provide a device.
[0008]
[Means for Solving the Problems]
The above object is achieved in an image forming apparatus provided with a plurality of image forming modes in which image formation is performed at different pixel densities, at warm-up when power is turned on, at all pixel densities different for the plurality of image forming modes. Is executed, an electrostatic latent image is formed on the photoreceptor, and a test patch image is formed by developing the formed electrostatic latent image while changing the rotation speed of the developing sleeve in various ways. A density detection is performed by a density detection sensor, and when the patch density data actually measured by the detection exceeds a preset threshold value, the rotation number of the development sleeve is detected, and the detected rotation number is used in the image forming mode. A first developing property setting program for the maximum density maintenance control determined as the number of rotations of the plurality of prints, and the program is executed when the number of prints reaches a predetermined number of prints. In one of the image forming modes, a test patch image is formed by forming an electrostatic latent image on the photoconductor and developing the formed electrostatic latent image while changing the rotation speed of the developing sleeve in various ways. The density of the test patch image is detected by a density detection sensor, and when the patch density data actually measured by the detection exceeds a preset threshold, the number of rotations of the developing sleeve is detected. And the plurality of images determined by the first developing property setting program are determined as the number of rotations of a new developing sleeve used for one of the image forming modes. By calculating based on each developing sleeve rotation speed in the forming mode, an image forming mode in which one new developing sleeve rotation speed among the plurality of image forming modes is determined. Thus it is achieved in the image forming equipment characterized by having a maximum concentration maintenance control second developability configuration program to determine a new developing sleeve speed for other image forming mode other than mode.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
<Embodiment 1>
FIG. 1 is a schematic configuration diagram showing Embodiment 1 of the image forming apparatus of the present invention.
[0010]
First, a normal copying operation of the image forming apparatus will be described. This image forming apparatus includes an image reading unit 10, a writing unit 20, which is a digital writing system, an image forming unit 30, a paper feeding unit 40, a document placing unit 50, and the like.
[0011]
At the top of the image forming apparatus, there is a document table 51 made of a transparent glass plate or the like, and a document table 50 including a document cover 52 covering the document D placed on the document table 51. Below, an image reading unit 10 including a first mirror unit 12, a second mirror unit 13, an imaging lens 14, a CCD imaging device 15, and the like is provided in the apparatus main body.
[0012]
The image of the document D on the document table 51 is translated from the solid line of the first mirror unit 12 including the illumination lamp 12A of the image reading unit 10 and the first mirror 12B to the position shown by the broken line, and the second mirror 13A The entire surface is illuminated and scanned by the following movement of the second mirror unit 13, which integrally includes the third mirror 13 </ b> B opposed to the first mirror unit 12, at a half speed, and the image is first scanned by the imaging lens 14. An image is formed on the image sensor 15 via the mirror 12B, the second mirror 13A, and the third mirror 13B. When the scanning is completed, the first mirror unit 12 and the second mirror unit 13 return to their original positions, and wait for the next image formation.
[0013]
The image data obtained by the photoelectric conversion by the image pickup device 15 is converted into a digital signal, then subjected to processing such as MTF correction and γ correction, and is temporarily stored in a memory as an image signal. Next, the image signal is read from the memory under the control of the CPU 60, pulse-width modulated, and then input to the writing unit 20.
[0014]
The image signal is input to the image forming unit 30 to the writing unit 20 including the drive motor 21, the polygon mirror 22, the fθ lens 23, the mirrors 24, 25, 26, and the semiconductor laser, the correction lens, and the like (not shown) under the control of the CPU 60. Then, the image recording operation is started. That is, the photosensitive drum 31 serving as an image carrier rotates clockwise as indicated by an arrow, and is discharged by a charge remover 36 that removes electricity by exposure, and then is charged by a charger 32. An electrostatic latent image corresponding to the image of the document D is formed on the photosensitive drum 31 by the laser beam L by 20. Thereafter, the electrostatic latent image on the photosensitive drum 31 is subjected to reversal development by a developer carried on a developing sleeve 33A, which is a developer carrying member to which a bias voltage of a developing unit 33 is applied, and a visible toner image is formed. It becomes. The developing sleeve 33A is driven to rotate by a drive motor M.
[0015]
On the other hand, the transfer paper P of the designated size is unloaded one by one from the paper feeding cassette 41A or 41B loaded in the paper feeding unit 40 by the unloading roller 42A, and transferred to the image transfer unit via the unloading roller 43 and the guide member 42. Feed paper toward. The fed transfer paper P is sent out onto the photosensitive drum 31 by a registration roller 44 that operates in synchronization with the toner image on the photosensitive drum 31. The toner image on the photoconductor drum 31 is transferred to the transfer paper P by the operation of the transfer device 34, separated from the surface of the photoconductor drum 31 by the discharging operation of the separator 35, and then fixed via the transport belt 45. After being fed to the container 37 and fused and fixed by the upper roller 37A and the lower roller 37B, it is discharged to the tray 54 outside the apparatus by the paper discharge rollers 38 and 46. Reference numeral 53 denotes a manual paper feed tray.
[0016]
The photosensitive drum 31 further continues to rotate, and the toner remaining on the surface thereof without being transferred is removed and cleaned by a cleaning blade 39A that is pressed against the surface of the cleaning device 39, and the charge is removed by the charge remover 36 again. After receiving the charge uniformly, the next image forming process is started.
[0017]
The magnetic permeability sensor TS provided at the bottom of the stirring screw 33C of the developing device 33 monitors the toner concentration of the developer in the developing device 33 by utilizing the fact that the magnetic permeability changes when the toner concentration of the developer changes. A sensor that sends toner concentration information of the developer to the CPU 60. When the toner density is reduced to a certain value or less based on the information from the magnetic permeability sensor TS, the CPU 60 sends a toner replenishment instruction to a toner replenishment unit (not shown) to perform toner replenishment, so that the toner density of the developer is always kept constant. can do.
[0018]
37A and 37B of the fixing device 37 are an upper roller and a lower roller which are a pair of rotating members for fixing.
[0019]
A heater 37D (upper roller 100W, lower roller 200W) composed of a halogen lamp or the like is provided at the inner core of the upper roller 37A and the lower roller 37B. The ambient temperature of the upper roller 37A and the lower roller 37B is detected by a temperature sensor 37C composed of a thermistor or the like and sent to the CPU 60. The CPU 60 controls the heater 37D by this detection signal to allow a predetermined temperature Tc which is a fixing control temperature. Keep within range.
[0020]
The lower roller 37B is pressed against the upper roller 37A at a constant pressure, for example, a linear pressure of 3.7 kg / cm by an urging member such as a spring (not shown). The upper roller 37A rotates clockwise, and the lower roller 37B comes into pressure contact with the upper roller 37A and rotates in a driven manner.
[0021]
The density detection sensor DS is provided between the developing device 33 and the transfer device 34 so as to face the photosensitive drum 31. Note that the density detection sensor DS may be provided between the transfer device 34 and the cleaning device 39.
[0022]
The density detection sensor DS is composed of a light emitting diode and a phototransistor.
[0023]
FIG. 2 shows a developing property setting process in the above image forming apparatus.
[0024]
When the power of the image forming apparatus is turned on, the warming-up of the fixing device is started. The developing property setting program is executed at the time of the warming-up and every time a predetermined number of sheets (for example, 1000 sheets) of the image forming apparatus are printed. The image forming apparatus according to this embodiment can set the pixel density to 400 dpi and 600 dpi as the image forming mode . As shown in FIG. 3, at the time of the first warm-up in the morning, a test patch image is created with all pixel densities in all image forming modes , and developability is set.
[0025]
The basic setting of the developing property is executed when the power is first turned on in the morning. First, it can be seen whether the power- on is the first power- on in the morning. In the developing property adjustment, a latent image for a test patch image, which is a reference electrostatic latent image, is formed on a photoconductor, and the latent image is developed by rotating a developing sleeve at various rotational speeds. A test patch image in which the density changes periodically is formed. The density of the test patch image is detected by the density detection sensor DS, the number of revolutions of the developing sleeve that gives a desired density is detected, and the number of revolutions of the developing sleeve is set. The reference electrostatic latent image is formed such that the test patch image corresponds to a so-called black solid image. That is, in the present embodiment, control for maintaining the maximum density is performed. Hereinafter, this developing property adjustment is referred to as maximum density maintenance control.
[0026]
To perform the maximum density maintenance control, first, as shown in FIG. 2A, a latent image of a test patch for the maximum density maintenance control is placed on the image carrier (photosensitive drum) 31 by several mm in the sub-scanning direction. Written at intervals. At this time, the exposure level is constant. For example, in the case of an 8-bit digital signal by pulse width modulation (PWM), patch exposure is performed at solid black, that is, at a level 255 corresponding to the maximum density. This test patch is subjected to reversal development by changing the rotation speed of the developing sleeve 33A of the developing unit for each test patch latent image, and becomes a plurality of test patch images having different densities as shown in FIG. The switching of the rotation speed of the developing sleeve 33A is performed by switching the rotation speed of the motor M. The density of the test patch image for the maximum density maintenance control is detected by the density detection sensor DS, and when the density exceeds a preset threshold value of the patch density data, that is, _R0 in FIG. The number (linear speed) is detected, and the number of rotations (linear speed) of the developing sleeve is fixed so as to use the number of rotations (linear speed) during image formation. Here, the above specified density is set to 1.4. This is because if the density is 1.35 or more, the quality of the copied image is sufficient. By such control, it is guaranteed that the image density of 1.4 or more is ensured in all environments. This maximum density maintenance control can also be performed by changing the toner concentration (mixing ratio) of the developer or by changing the transport amount of the developer on the developing sleeve. Is excellent in not generating any.
[0027]
As shown in FIG. 3, at the time of the first warm-up in the morning, the developability setting is performed for each of the image forming modes with the pixel density of 400 dpi and 600 dpi.
[0028]
Next, as shown in FIG. 4A, maximum density maintenance control is performed every 1000 copies. This operation is performed after the completion of the copy job to which the copy whose counter count has reached 1000 belongs.
[0029]
First, the image forming apparatus is set to the 400 dpi image forming mode. Then, through the steps of forming the test patch latent image as described above, developing with changing the number of rotations of the developing sleeve, and measuring the density of the developed test patch image, rotating the new developing sleeve in the image forming mode of 400 dpi The number is set.
[0030]
Next, based on the number of rotations of the developing sleeve in each of the image forming modes of 400 dpi, 600 dpi set at the time of the first warm-up in the morning, and 400 dpi at the time of printing 1000 sheets, a new one at the time of printing 1000 sheets in the image forming mode of 600 dpi. The rotation speed of the developing sleeve is calculated and set. The reason why the setting of the developing sleeve rotation speed at the time of printing 1000 sheets is 400 dpi is performed based on the actual measurement, and 600 dpi is performed by calculation because the 400 dpi image forming mode is the most frequently used image forming mode. In the developing sleeve rotation speed setting step in the 400 dpi image forming mode, the linear speed of the developing sleeve was set to 370 mm / sec (this linear speed is set to a coefficient of 25), and in the 600 dpi image forming mode, the linear speed was set to 296 mm / sec and the coefficient was set to 20. . For the 1000th sheet, the coefficient is set to 27 in the 400 dpi image forming mode. Based on these rotational speed coefficients 25, 20, and 27, the rotational speed coefficient of the developing sleeve in the 600 dpi image forming mode on the 1000th sheet was set to 22.
[0031]
<Embodiment 2>
FIG. 4B is a diagram illustrating a program according to the second embodiment. The same image forming apparatus as in Embodiment 1 was used. In this embodiment, the maximum concentration maintenance control at the beginning of the morning is performed in the same manner as in the first embodiment. In the maximum density maintenance control at the time of copying 1000 sheets, in this embodiment, the image forming mode of the pixel density is not set. The maximum density maintenance control is performed in the image forming mode of the pixel density in the copy job to which the copy of the 1000th copy belongs. That is, if the 1000th copy is performed in the 600 dpi image forming mode, formation of a test patch latent image, development, density measurement of the test patch image, and rotation number setting of the developing sleeve are performed in this image forming mode. .
[0032]
The rotation speed of the developing sleeve in the image forming mode of 400dpi is developing in the rotational speed and the 1,000th 600dpi image formation mode of the developing sleeve for an image formation and 600dpi image formation 400dpi set during most of the warm-up in the morning It is determined and set by calculation from the rotational speed of the sleeve.
[0033]
【The invention's effect】
According to the present invention, a maximum density maintenance control for forming a test patch image and determining the number of rotations of the developing sleeve by detecting the density is performed for a part of the operation mode of the image forming apparatus. Since the maximum density maintenance control is performed by calculating data stored in the apparatus, the time required for the maximum density maintenance control is saved, and a decrease in print efficiency is prevented.
[Brief description of the drawings]
FIG. 1 is a diagram schematically illustrating a configuration of an image forming apparatus according to an embodiment of the invention.
FIG. 2 is a diagram showing a test patch image.
FIG. 3 is a flowchart showing an outline of an operation program of the embodiment.
FIG. 4 is a flowchart showing an outline of an operation program according to another embodiment of the present invention.
[Explanation of symbols]
Reference Signs List 10 Image reading unit 20 Writing unit 30 Image forming section 31 Photoconductor drum 32 Charging device 33 Developing device 60 CPU
DS Concentration detection sensor M Drive motor

Claims (3)

In an image forming apparatus provided with a plurality of image forming modes in which images are formed at different pixel densities,
At the time of warm-up at the time of power-on, it is executed at all pixel densities different for each of the plurality of image forming modes,
Forming a test patch image by forming an electrostatic latent image on the photoreceptor and developing the formed electrostatic latent image by changing the rotational speed of the developing sleeve in various ways; The number of rotations of the developing sleeve that exceeds a preset threshold value among the patch density data actually measured by the detection is detected, and the detected number of rotations is used in the image forming mode. A first developing property setting program for maximum density maintenance control determined as a number;
Executed when the number of prints reaches a predetermined number,
In one of the plurality of image forming modes, a test patch is formed by forming an electrostatic latent image on a photoreceptor and developing the formed electrostatic latent image while variously changing the rotation speed of a developing sleeve. An image is formed, the density of the test patch image is detected by a density detection sensor, and the number of rotations of the developing sleeve is detected when the density exceeds a preset threshold value among the patch density data actually measured by the detection. Is determined as the number of revolutions of a new developing sleeve used for one of the plurality of image forming modes, and the number of revolutions of the determined new developing sleeve and the number of revolutions determined by the first developability setting program are determined. By calculating based on each developing sleeve rotation speed of the plurality of image forming modes, one new developing sleeve rotation speed of the plurality of image forming modes is determined. An image forming apparatus wherein a maximum concentration maintenance control second developability configuration program to determine a new developing sleeve speed for other image forming mode other than the imaging mode. The step of determining the rotation speed of the developing sleeve from the density data performed in the second developability setting program is performed for the most frequently used image forming mode among the plurality of image forming modes. The image forming apparatus according to claim 1. The step of determining the rotation speed of the developing sleeve from the density data performed in the second developing property setting program is performed at the pixel density of the image forming mode set when the number of prints reaches a predetermined number. The image forming apparatus according to claim 1, wherein:

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