JP2006030738A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of suppressing noise to the minimum and always realizing sufficient cleaning performance. <P>SOLUTION: The image forming apparatus includes a stage in which a toner image is formed on a 1st image carrier by a developing device and is primarily transferred to a 2nd image carrier, and a stage in which the former stage is repeated further for a plurality of colors so as to secondarily transfer the superposed toner images to transfer material, and then it has a charging member abutting on the 2nd image carrier, a charging means comprising a power source for applying alternating voltage to the charging member on a more downstream side than the secondary transfer position of the 2nd image carrier and on a more upstream side than the primary transfer position thereof, and includes a stage in which toner coming from the secondary transfer position to the position of the charging member through the 2nd image carrier is charged to have a predetermined polarity by the charging means. In the apparatus, the amount of the charged toner is estimated or detected and the frequency of the alternating voltage is set to be higher as the amount of the toner becomes larger. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer.

  FIG. 1 is a diagram showing an example of a conventional intermediate transfer belt type color image forming apparatus.

  In FIG. 1, reference numeral 1 denotes a photosensitive drum as an electrostatic latent image carrier. An organic photoconductor (OPC) or a photoconductor made of A-Si, CdS, Se or the like is coated on the outer peripheral surface of a cored bar made of aluminum or the like. And is rotated in the direction of arrow C1 at an outer peripheral speed V1 (hereinafter referred to as a process speed).

  Reference numeral 3 denotes an exposure apparatus for forming a latent image on the surface of the photosensitive drum 1, and reference numeral 3a denotes an exposure position. Reference numeral 60 denotes an intermediate transfer belt as a second image carrier, which is made of rubber such as EPDM, NBR, urethane, and silicone rubber, or resin such as PI, PA, PC, PVDF, ETFE, PET, PC / PET, and ETFE / PC. It is stretched on two rollers, a driving roller 6b and a stretching roller 6c, which are secondary transfer counter rollers, and the driving roller 6b is rotated by driving means (not shown), thereby causing a process in the direction of arrow C3. Driven at speed V1.

  The intermediate transfer belt 60 is provided with a position detection member 5a that can be distinguished from the surface of the intermediate transfer belt 60 by the optical sensor 5 at one end in the circumferential direction and at an end in a direction perpendicular to the circumferential direction. Recognizes the rotational phase by detecting the position detection member 5a passing through the detection unit 5b by the optical sensor 5 (hereinafter referred to as TOP detection) and counting the time inside the main body based on the detection. it can. T1 is a contact portion between the photosensitive drum 1 and the intermediate transfer belt 60, that is, a primary transfer portion. Reference numeral 7 b denotes a primary transfer roller provided with a conductive sponge layer on the shaft, and is in contact with the photosensitive drum 1 through an intermediate transfer belt 60.

  Reference numerals 100 and 101 denote means for charging the toner on the intermediate transfer belt 60, and reference numerals 100b and 101b denote charging rollers as charging members that are driven by the intermediate transfer belt 60 and rotate at the same peripheral speed. It has an abutment / separation mechanism (not shown) and can abut at a desired time. Reference numerals 100a and 101a denote a DC voltage power source and an alternating voltage power source for applying a voltage to the charging rollers 100b and 101b, respectively. In addition, by using the driving roller 6b as a counter electrode, the charging efficiency when charging by these charging rollers is increased.

  The full color image forming process will be described below with reference to FIG.

  The photosensitive drum 1 is driven in the direction of the arrow C1 by a driving unit (not shown), and is uniformly charged to a predetermined potential by the charging roller 2. At the timing when the TOP of the intermediate transfer belt 60 is detected, exposure is started by the exposure device 3, and light by a signal according to the yellow image pattern is scanned onto the photosensitive drum 1 whose surface is uniformly charged to form a latent image. Is done.

  When the photosensitive drum 1 further rotates in the direction of the arrow C1 after the latent image formation is started, the developing device 4a containing yellow toner among the developing devices 4a, 4b, 4c, and 4d supported by the support 4 becomes the photosensitive drum 1. The support 4 rotates in the direction of the arrow C2 so as to face each other. The selected developing device 4a has a developing roller (not shown) that rotates at a predetermined rotational speed at a portion facing the photosensitive drum 1, and the negative electrode carried on the surface of the developing roller by being continuously supplied inside the developing device. The latent image is visualized by the toner. At this time, only the latent image forming portion on the surface of the photosensitive drum 1 is visualized by the toner because the negative polarity toner is developed in the non-latent image forming portion by the potential difference between the developing device and the photosensitive drum 1 (hereinafter, development bias). This is because the potential difference is changed only in the portion where the latent image is formed, and the toner is transferred to the photosensitive drum 1 while the toner is not transferred from the container to the photosensitive drum 1. Note that the normal development bias is applied by a high voltage power source.

  When the photosensitive drum 1 further rotates in the direction of the arrow C1 and reaches the primary transfer portion T1, the developed toner image is positively fed from the high-voltage power source 7a to the primary transfer roller 7b with the cored bar of the photosensitive drum 1 as a counter electrode. By being applied with a positive bias, primary transfer is performed on the intermediate transfer belt 60. The untransferred toner on the photosensitive drum 1 is cleaned by a cleaner (hereinafter referred to as a blade cleaner) 13 that scrapes off by bringing the blade into contact therewith.

  When the development of the yellow toner image is completed, the developing device is switched. The support 4 rotates counterclockwise, and the developing device 4b containing the next magenta toner is positioned at a position facing the photosensitive drum 1. Further, when the next TOP detection is performed, the same operation is repeated, and development and transfer are performed for magenta, cyan, and black, and a plurality of color toner images are formed on the intermediate transfer belt 60. At this time, since all the four color images are transferred to the same position on the intermediate transfer belt 60, the positions of the four color toner images coincide with each other.

  When the four color toner images are transferred onto the intermediate transfer belt 60, the transfer material P is conveyed from the registration roller R in synchronization with the movement of the intermediate transfer belt 60, and has the same configuration as the primary transfer roller 7b. The secondary transfer roller 9 comes into contact with the intermediate transfer belt 60 through the transfer material P, and a positive polarity bias is applied from a high voltage power source (not shown) using the driving roller 6b as a counter electrode. The toner images are secondarily transferred onto the transfer material P all at once.

  The transfer material P onto which the four color toner images have been transferred is melt-fixed by a conventionally known fixing device 11 that rotates a heating roller and a pressure roller using a driving means (not shown), and is discharged by a paper discharge device (not shown). By being papered, a color image is obtained.

  Next, FIG. 1 shows a cleaning process of toner that has not been transferred during the secondary transfer and remains on the intermediate transfer belt 60 (hereinafter referred to as secondary transfer residual toner).

  The secondary transfer residual toner is given a positive charge by a charging roller 100b to which a positive DC voltage is applied from a DC voltage power supply 100a. Although the charge amount of each toner particle after the charging is not uniform, charging can be performed while suppressing toner scattering.

  Subsequently, the secondary transfer residual toner is again given positive charge by the charging roller 101b to which an alternating voltage obtained by superimposing an alternating voltage of a predetermined frequency on a positive DC voltage having a predetermined value is applied from the alternating voltage power supply 101a. Is done. By this charging, the electric polarity of the toner particles maintains the positive polarity, and the charge amount of each particle is made uniform.

  Subsequently, the secondary transfer residual toner proceeds to the primary transfer portion T1, and is electrostatically transferred to the photosensitive drum simultaneously with the primary transfer of the first color of the next page by the primary transfer roller 7b to which the positive polarity bias is applied. It is removed from the intermediate transfer belt 60. Then, the secondary transfer residual toner transferred to the photosensitive drum 1 is collected by the photosensitive drum cleaner 13, and the removal of the secondary transfer residual toner on the intermediate transfer belt 60 is completed.

  For mono-color printing, in the case of full-color printing, four color images are sequentially primary transferred and superimposed, and then the process after secondary transfer is performed. Process after secondary transfer.

  Further, at the time of density control and registration control, a toner image having a dedicated pattern is sequentially transferred to the primary image and detected by density detection means (not shown), and then the toner image is cleaned. Unlike printing, untransferred toner remains on the intermediate transfer belt 60, but cleaning is performed in the same process as that after the secondary transfer of the printing sequence. Cleaning is also performed in the same way when jamming (hereinafter referred to as non-transfer time including density control and registration control). Note that the toner on the intermediate transfer belt 60 when not transferred is clearly more than the secondary transfer residual toner on average, and therefore the cleaning process is performed a plurality of times. In particular, in this apparatus, two or more colors of toner are not transferred in the registration detection and patch detection processes, whereas two or more colors of toner are transferred in the jam. The cleaning process is performed carefully.

  Specifically, the frequency setting of the charging bias applied to the charging roller 101b and the cleaning cycle in the intermediate transfer belt cleaning process during mono-color printing, full-color printing, density control / registration control, and jamming are shown in Table 1. It is done as shown in With this setting, it was possible to perform sufficient cleaning in each mode.

JP 2001-265095 A

  Unlike full color printing, different color toners are transferred in a superimposed manner, so that the amount of secondary transfer residual toner increases. That is, on average, the amount of toner that needs to be cleaned increases in the order of mono-color printing, full-color printing, and non-transfer.

  On the other hand, the frequency of the alternating voltage applied for charging is up to about 800 Hz. In this range, the higher the frequency, the worse the audible noise.

Therefore, in the above conventional example, in order to always ensure sufficient cleaning performance at all times of mono color printing, full color printing, and non-transferring, the frequency setting is set in accordance with the cleaning when the non-transferring is the most dirty When cleaning the secondary transfer residual toner during printing,
Noise is being wasted.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of suppressing noise to a minimum and always realizing sufficient cleaning performance. .

In order to solve the above-mentioned problems, the invention described in claim 1 includes a step of forming a toner image on the first image carrier by the developing device and primarily transferring the toner image to the second image carrier. Further, the process is repeated for a plurality of colors,
A charging means comprising a step of secondarily transferring the superimposed toner image onto the transfer material, and comprising a charging member contacting the second image carrier and a power source for applying an alternating voltage to the charging member; Toner that is downstream of the secondary transfer position of the second image carrier and upstream of the primary transfer position, and that is transferred by the charging means from the secondary transfer position to the charging member position via the second image carrier. In an image forming apparatus having a process of charging the toner to a predetermined polarity, the amount of toner to be charged is predicted or detected,
The higher the toner amount, the higher the frequency of the alternating voltage.

  The invention according to claim 2 is characterized in that, in the invention according to claim 1, the frequency of the alternating voltage in the charging process of the secondary transfer residual toner at the time of full color printing is made higher than the frequency at the time of mono color printing. To do.

  The invention according to claim 3 is the invention according to claim 1 or 2, wherein the frequency of the alternating voltage in the charging process of the density control toner image is higher than the frequency in the charging process of the secondary transfer residual toner at the time of printing. It is characterized by doing.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the frequency of the alternating voltage in the charging process of the registration control toner image is set in the charging process of the secondary transfer residual toner during printing. It is characterized by being higher than the frequency.

  According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the alternating voltage in the charging process of the toner image remaining on the second image carrier when a jam occurs during printing. The frequency is higher than the frequency in the charging process of the secondary transfer residual toner during printing.

  According to a sixth aspect of the present invention, in the invention according to any one of the first to fifth aspects, the frequency in the charging process of the toner image is adjusted according to the usage state of the second image carrier. .

  A seventh aspect of the invention is characterized in that, in the invention according to any one of the first to sixth aspects, the frequency in the charging process of the toner image is adjusted according to the use state of the developing device.

  The invention according to claim 8 is the invention according to any one of claims 1 to 7, wherein the frequency in the charging process of the toner image is adjusted according to the temperature and humidity environment when the charging process is performed. .

  According to the first aspect of the present invention, noise due to the AC component of the charging bias can be minimized and sufficient cleaning performance can be ensured according to the amount of toner to be cleaned.

  According to the second aspect of the invention, the effect of the first aspect of the invention can be obtained according to the difference in the amount of toner to be cleaned during full-color printing and mono-color printing.

  According to the third aspect of the present invention, the effects of the first and second aspects of the present invention can be obtained according to the difference in toner amount to be cleaned between density control and printing.

  According to the fourth aspect of the present invention, the effects of the first to third aspects of the present invention can be obtained according to the difference in the amount of toner to be cleaned during registration control and printing.

  According to the fifth aspect of the present invention, the effects of the first to fourth aspects of the present invention can be obtained according to the difference in the amount of toner to be cleaned between jamming and printing.

  According to the sixth aspect of the present invention, the effects of the first to fifth aspects of the present invention can be obtained according to the amount of toner to be cleaned depending on the usage status of the second image carrier.

  According to the seventh aspect of the present invention, the effects of the first to sixth aspects of the invention can be obtained according to the difference in the amount of toner to be cleaned depending on the usage status of the developing device.

  According to the eighth aspect of the invention, the effects of the first to seventh aspects of the invention can be obtained according to the difference in the amount of toner to be cleaned due to the temperature and humidity environment during the charging process.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

<Embodiment 1>
Also in this embodiment, the image forming apparatus shown in FIG. 1 can be used as in the conventional example. Table 2 shows an example of the frequency setting of the charging bias in each mode in the present invention.

  In the present invention, except for the frequency of the AC component of the bias applied to the charging roller 101b in the intermediate transfer belt cleaning process, it is the same as the conventional example.

  The feature of the present invention is that in order to improve the cleaning property in the intermediate transfer belt cleaning process as the toner to be cleaned increases during mono-color printing, full-color printing, registration detection / patch detection, jamming, etc. The bias frequency is increased. In consideration of the fact that the higher the frequency, the greater the noise, so that the frequency is not increased more than necessary to ensure the cleaning property. In particular, at the time of printing with a high effective frequency, it is desirable to make the frequency as low as possible while ensuring cleaning properties. On the contrary, when the jam is usually low in effective frequency, an extra cleaning property may be secured even if the frequency is slightly increased.

  Specifically, the frequency was set as shown in Table 2 in each mode.

本発明では、各モード毎のクリーニングするトナー量の違いに応じて、帯電バイアスの交流成分による騒音を最小限に抑制し、且つ、十分なクリーニング性を確保することができた。

In the present invention, noise due to the AC component of the charging bias can be minimized and sufficient cleaning performance can be ensured according to the amount of toner to be cleaned for each mode.

<Embodiment 2>
Also in this embodiment, the image forming apparatus shown in FIG. 1 can be used as in the conventional example. Table 3 shows an example of the relationship between the life of the intermediate transfer belt and the frequency setting of the charging bias in the present invention.

  In the present invention, except for the frequency of the AC component of the bias applied to the charging roller 101b in the intermediate transfer belt cleaning process, it is the same as the conventional example.

  The feature of the present invention is that as the life of the intermediate transfer belt 60 advances, the secondary transfer performance decreases, and the toner to be cleaned on the average increases, the charging is performed in order to improve the cleaning performance in the intermediate transfer belt cleaning process. The bias frequency is increased. In consideration of the fact that the higher the frequency, the greater the noise, so that the frequency is not increased more than necessary to ensure the cleaning property.

  Specifically, the frequency was set as shown in Table 3 for each life.

本発明では、中間転写ベルトの寿命が進むことによるクリーニングするトナー量の違いに応じて、帯電バイアスの交流成分による騒音を最小限に抑制し、且つ、十分なクリーニング性を確保することができた。

In the present invention, the noise due to the AC component of the charging bias can be minimized and sufficient cleaning performance can be ensured according to the difference in the amount of toner to be cleaned as the life of the intermediate transfer belt advances. .

  In this embodiment, the frequency is set in consideration of the fact that the secondary transfer property is lowered according to the life, but the secondary transfer property at high temperature and high humidity or low temperature and low humidity is also reduced in the environment. It is better to increase the frequency. That is, noise can be further suppressed by optimizing the frequency for each job, for example, so that the optimum frequency is set according to the environment and the life of the intermediate transfer belt.

It is a block diagram of the principal part of a color image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 3 Exposure apparatus 4a-4d Developing apparatus 5 Optical sensor 7b Primary transfer roller 9 Secondary transfer roller 11 Fixing apparatus 60 Intermediate transfer belt

Claims (8)

Forming a toner image on the first image carrier by the developing device, and performing a primary transfer of the toner image to the second image carrier, and further repeating the process for a plurality of colors;
A charging means comprising a step of secondarily transferring the superimposed toner image onto the transfer material, and comprising a charging member contacting the second image carrier and a power source for applying an alternating voltage to the charging member; Toner that is downstream of the secondary transfer position of the second image carrier and upstream of the primary transfer position, and that is transferred by the charging means from the secondary transfer position to the charging member position via the second image carrier. In an image forming apparatus having a process of charging to a predetermined polarity,
An image forming apparatus characterized by predicting or detecting the amount of toner to be charged, and increasing the frequency of the alternating voltage as the amount of toner increases.   2. The image forming apparatus according to claim 1, wherein the frequency of the alternating voltage in the charging process of the secondary transfer residual toner at the time of full color printing is made higher than the frequency at the time of mono color printing.   3. The image forming apparatus according to claim 1, wherein the frequency of the alternating voltage in the charging process of the density control toner image is higher than the frequency in the charging process of the secondary transfer residual toner during printing.   4. The image according to claim 1, wherein the frequency of the alternating voltage in the charging process of the registration control toner image is higher than the frequency in the charging process of the secondary transfer residual toner at the time of printing. Forming equipment.   When a jam occurs during printing, the frequency of the alternating voltage in the charging process of the toner image remaining on the second image carrier is set to be higher than the frequency in the charging process of the secondary transfer residual toner during printing. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   The image forming apparatus according to claim 1, wherein a frequency in a charging process of the toner image is adjusted according to a usage state of the second image carrier.   The image forming apparatus according to claim 1, wherein a frequency in a charging process of the toner image is adjusted according to a use state of the developing device.   The image forming apparatus according to claim 1, wherein the frequency in the charging process of the toner image is adjusted according to the temperature and humidity environment when performing the charging process.

Images