JP2006084512A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem wherein stable transferability can not be maintained against the change of environment and the change in the toner concentration of developer in a method to control a condition for actuating a charge imparting means for performing pretransfer electrification, based on the detected value of the potential of a toner image in terms of technique for improving the transferability by the pretransfer electrification. <P>SOLUTION: The condition for actuating the charge imparting means is set, based on a result obtained by detecting the potential of the toner image before charging by the charge imparting means, and a condition for actuating a secondary transfer means is set, based on the result obtained by detecting the potential of the toner image after charging. Then, the condition for actuating the charge-imparting means is set based on the potential of the toner image and the density of the toner image. Furthermore, the toner image having toner adhesive amount set in a plurality of steps is formed, its potential is detected, and then the condition for actuating the charge imparting means is set from the detected potential in a plurality of steps. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multifunction machine having these functions, and more particularly to an electrophotographic image forming apparatus, and more particularly to secondary transfer in an image forming apparatus having an intermediate transfer member. Related to technology.

  In an electrophotographic image forming apparatus, a toner image is formed on an image carrier such as a photoreceptor by charging, exposure and development, and the formed toner image is primarily transferred to an intermediate transfer member, and then the toner image on the intermediate transfer member In addition, there is a method of performing secondary transfer onto a transfer material. Such an image forming apparatus is often used in a color image forming apparatus, and forms a single color toner image on a plurality of photoconductors and transfers the image onto the intermediate transfer body, thereby superimposing the single color toner images on the intermediate transfer body. In addition, a multicolor toner image is formed, and the formed multicolor toner image is transferred to a transfer material.

  In an image forming process in which an intermediate transfer member is used for secondary transfer, the transferability in secondary transfer may change due to environmental influences, developer toner concentration, primary transfer conditions, etc., and image quality may deteriorate. . That is, the toner charge amount of the toner image on the intermediate transfer member changes due to changes in the environmental temperature, environmental humidity, developer toner image degree, etc., or the toner charge amount varies depending on the number of primary transfers. Changes in image quality and causes deterioration in image quality.

  In order to prevent such deterioration in image quality, in Patent Documents 1 and 2, the toner image on the intermediate transfer member is charged before the secondary transfer, thereby uniformizing the charge amount of the toner and performing a uniform secondary transfer. Has been proposed to do.

Japanese Patent Application Laid-Open No. 2004-228620 proposes detecting the potential of a toner image on an intermediate transfer member and controlling charging before secondary transfer based on the detected value.
JP-A-10-274892 Japanese Patent Laid-Open No. 11-143255

  The charge amount of the toner constituting the toner image on the intermediate transfer member varies depending on the environment, the toner concentration of the developer, the usage history of the developer, and the like. Accordingly, appropriate transfer conditions in the secondary transfer also change in accordance with the change in the toner charge amount. Therefore, pre-transfer charging for adjusting the transfer conditions in the secondary transfer disclosed in Patent Documents 1 and 2 is performed. This is an effective means for improving and stabilizing transferability in secondary transfer.

  In addition, the means used in Patent Document 2, that is, detecting the potential of the toner image on the intermediate transfer member and controlling the pre-transfer charging conditions according to the detected potential, makes the secondary transfer appropriate. This is a more effective means for performing under conditions.

  However, the control based solely on the potential of the toner image on the intermediate transfer member has the following problems, and good secondary transfer may not be performed.

  That is, firstly, the transfer conditions in the secondary transfer change due to the charging by the pre-transfer charging means. Therefore, when the charging by the pre-transfer charging means is changed variously, the appropriate conditions in the transfer change accordingly. However, when transfer is performed under certain conditions, transfer failure occurs.

  Second, an accurate charge amount of toner cannot be obtained from the detection result of the surface potential of the toner image. On the other hand, since the transfer condition depends on the charge amount of the toner, the appropriate transfer condition is not always set when the control based on the detection result of the surface potential is performed.

  Third, if the charge control is performed based on the detection result obtained by detecting the potential of a single pattern toner image having a constant density, an appropriate transfer condition is not always set.

  When controlling the pre-transfer charging, control is performed to form a toner image of a predetermined pattern on the intermediate transfer member, detect the potential of the formed toner image, and set the operating conditions of the pre-transfer charging means. However, when the density of the toner image changes due to a change in environment or a change in the toner density of the developer, the charge by the pre-transfer charging means may deviate from an appropriate value.

  For this reason, in the control of pre-transfer charging disclosed in Patent Document 2, it is not guaranteed that proper transfer is always performed, and deterioration in image quality due to transfer unevenness cannot be avoided.

  An object of the present invention is to solve such problems in conventional pre-transfer charging.

The object is achieved by the following invention.
(Claim 1)
Image carrier,
Image forming means for forming a toner image on the image carrier;
Intermediate transfer member,
Primary transfer means for transferring a toner image on the image carrier to the intermediate transfer member;
Secondary transfer means for transferring a toner image onto a transfer material on the intermediate transfer member;
An intermediate transfer member cleaning means for cleaning the intermediate transfer member after the secondary transfer; and
In the image forming apparatus having a charge applying unit for applying a charge to the intermediate transfer body between the primary transfer unit and the secondary transfer unit,
Having a potential detection means and a control means for detecting the surface potential of the intermediate transfer member;
The control unit sets the operating condition of the charge applying unit based on the potential of the toner image on the intermediate transfer body before the charge applying by the charge applying unit detected by the potential detecting unit,
An operation condition of the secondary transfer unit is set based on the potential of the toner image on the intermediate transfer body after the charge is applied by the charge application unit detected by the potential detection unit. .
(Claim 2)
The image forming apparatus according to claim 1, wherein the potential detection unit is disposed downstream of the charge applying unit and upstream of the secondary transfer unit with respect to a moving direction of the intermediate transfer unit.
(Claim 3)
Image carrier,
Image forming means for forming a toner image on the image carrier;
Intermediate transfer member,
Primary transfer means for transferring a toner image on the image carrier to the intermediate transfer member;
Secondary transfer means for transferring a toner image onto a transfer material on the intermediate transfer member;
An intermediate transfer member cleaning means for cleaning the intermediate transfer member after the secondary transfer; and
In the image forming apparatus having a charge applying unit for applying a charge to the intermediate transfer body between the primary transfer unit and the secondary transfer unit,
A potential detection means for detecting the surface potential of the intermediate transfer member, a density detection means for detecting the density of the toner image on the intermediate transfer member, and a control means;
The control means is based on the potential of the toner image of the predetermined pattern formed on the intermediate transfer member detected by the potential detection means and the density of the toner image of the predetermined pattern detected by the density detection means. An image forming apparatus characterized in that an operating condition of a charge applying unit is set.
(Claim 4)
The image forming apparatus according to claim 1, wherein the control unit controls the charge applying unit to apply a charge only when the potential detected by the potential detecting unit is equal to or higher than a predetermined reference value.
(Claim 5)
Image carrier,
Image forming means for forming a toner image on the image carrier;
Intermediate transfer member,
Primary transfer means for transferring a toner image on the image carrier to the intermediate transfer member;
Secondary transfer means for transferring a toner image onto a transfer material on the intermediate transfer member;
Intermediate transfer member cleaning means for cleaning the intermediate transfer member after secondary transfer, and
In an image forming apparatus having a charging electrode and a grid, and having a charge applying unit that applies a charge to the intermediate transfer body between the primary transfer unit and the secondary transfer unit.
Having a potential detection means and a control means for detecting the surface potential of the intermediate transfer member;
The control unit controls the potential of the grid from a plurality of surface potentials of toner images formed on the intermediate transfer body and having different toner adhesion amounts detected by the potential detection unit. apparatus.
(Claim 6)
6. The control unit according to claim 5, wherein the control unit sets the grid potential based on the surface potential having a lowest value that exceeds a predetermined reference value among the plurality of surface potentials. Image forming apparatus.

  According to the invention of any one of claims 1 to 6, high transferability in secondary transfer is stably maintained, and a high-quality image is stably formed.

  According to the first or second aspect of the invention, even when the charging potential of the toner image by the charge applying unit changes, the transferability of the secondary transfer is stable, and a high-quality image is stably formed.

  According to the invention of any one of claims 3 to 6, stable secondary transfer is performed even when the charge amount of the toner in development changes due to a change in environment or a change in toner density of the developer, and a high-quality image is obtained. Is formed.

  According to the invention of claim 4, stable secondary transfer can be performed by simple control.

The present invention will be described below with reference to embodiments, but the present invention is not limited to the embodiments. In the following description, the charge amount of toner refers to the charge per unit mass of toner, for example, μC / g.
<Embodiment 1>
FIG. 1 is a diagram showing a color image forming apparatus according to an embodiment of the present invention.

  This color image forming apparatus is called a tandem type color image forming apparatus, and includes a plurality of sets of image forming units 20Y, 20M, 20C, and 20K, an intermediate transfer unit, a sheet feeding and conveying apparatus, and a fixing apparatus 8.

  The image forming unit 20Y that forms a yellow image includes a charging device 2Y, an exposure device 3Y, a developing device 4Y, a primary transfer unit 5Y, and a cleaning unit 6Y disposed around a photoreceptor 1Y as an image carrier. The image forming unit 20M that forms a magenta image includes a charging device 2M, an exposure device 3M, a developing device 4M, a primary transfer unit 5M, and a cleaning unit 6M arranged around a photoconductor 1M as an image carrier. The image forming unit 20C that forms a cyan image includes a charging device 2C, an exposure device 3C, a developing device 4C, a primary transfer unit 5C, and a cleaning unit 6C, which are arranged around a photoconductor 1C as an image carrier. The image forming unit 20K that forms a black image includes a charging device 2K, an exposure device 3K, a developing device 4K, a primary transfer unit 5K, and a cleaning unit 6K arranged around a photoconductor 1K as an image carrier.

  The belt-like intermediate transfer member 7 is semiconductive and is wound around a plurality of rollers and supported so as to be able to circulate.

  The image forming means including the charging device 2Y, the exposure device 3Y, and the developing device 4Y charges, exposes, and develops the photoconductor 1Y, thereby forming a yellow toner image on the photoconductor. Similarly, a magenta toner image is formed on the photosensitive member 1M by the image forming unit including the charging device 2M, the exposure device 3M, and the developing device 4M, and the image forming unit including the charging device 2C, the exposure device 3C, and the developing device 4C. A cyan toner image is formed on the photoreceptor 1C, and a black toner image is formed on the photoreceptor 1K by image forming means including the charging device 2K, the exposure device 3K, and the developing device 4K. These single color toner images are transferred to the intermediate transfer body 7 by the transfer rollers 5Y, 5M, 5C, and 5K, and are superimposed to form a multicolor toner image.

  As the photosensitive member 1, a well-known one such as an OPC photosensitive member or an aSi photosensitive member is used. An OPC photosensitive member is preferable, and a negatively charging OPC photosensitive member is particularly preferable. OPC is used.

  As the charging device 2, a corona discharge device such as a scorotron or a corotron is used, and a scorotron discharge device is preferably used.

  As the exposure apparatus, a light emitting element that emits light according to image data, such as a laser or an LED array, is used.

  As the developing device 4, a developing device using a two-component developer mainly composed of a carrier and a toner or a developing device using a one-component developer mainly composed of a toner without using a carrier is used. A two-component developing device using a diameter toner is preferable. In addition, a developing device that performs development by regular development or a device that performs reversal development can be used in the developing device. However, a developing bias having the same polarity as the charging of the photosensitive member 1 is applied to the developing sleeve 4a, and the charging of the photosensitive member is the same. Reversal development in which development is performed with toner charged to polarity is preferable. In this embodiment, development is performed by reversal development using negatively charged toner.

  As the toner having a small particle diameter, a toner having a volume average particle diameter of 3 to 6 μm is preferable.

  The volume average particle diameter is an average particle diameter based on volume, and is a value measured by “Coulter Counter TA-II” or “Coulter Multisizer” (both manufactured by Coulter, Inc.) equipped with a wet disperser.

  A high-quality image having a high resolving power can be formed by such a small particle size toner. A toner having a volume average particle diameter larger than 6 μm weakens the characteristics of high image quality.

  When a toner having a volume average particle size of less than 3 μm is used, the image quality is likely to deteriorate due to fogging.

  In the present invention, spherical toner is desirable, and the degree of spheroidization is desirably 0.94 or more and 0.98 or less.

Degree of spheroidization = (perimeter of a circle with the same area as the particle projection image) / (perimeter of the particle projection image)
The degree of spheroidization is obtained by taking a photograph of resin particles enlarged 500 times with a scanning electron microscope or laser microscope for 500 resin particles, and using an image analysis apparatus “SCANNING IMAGE ANALYSER” (manufactured by JEOL Ltd.) Then, the photographic image is analyzed, the circularity is measured, and the arithmetic average value can be obtained. Moreover, as a simple measuring method, it can measure with "FPIA-1000" (made by Toa Medical Electronics Co., Ltd.).

  When the spheroidization degree is less than 0.94, it is crushed as a result of being subjected to strong stress in the developing device, and fog and toner scattering are likely to occur. If the sphericity is greater than 0.98, it may be difficult to maintain high cleaning performance.

  For the toner having a small particle diameter and a high sphericity as described above, it is desirable to use a polymerized toner.

  The polymerized toner means a toner obtained by forming a binder resin for toner and forming the toner shape by polymerization of a raw material monomer or prepolymer of the binder resin and subsequent chemical treatment. More specifically, it means a toner obtained through a polymerization reaction such as suspension polymerization or emulsion polymerization and, if necessary, a step of fusing particles between them. In a polymerized toner, a raw material monomer or prepolymer is uniformly dispersed in an aqueous system and then polymerized to produce a toner, so that a toner having a uniform toner particle size distribution and shape can be obtained.

  Specifically, a polymer is produced by emulsion polymerization of a monomer in a liquid of an aqueous medium to which an emulsion is added or a suspension polymerization method, and then an organic solvent, agglomeration is produced. It can manufacture by the method of adding an agent etc. and making it associate. A method of preparing by mixing with a dispersion liquid of a release agent or a colorant necessary for the constitution of the toner at the time of association, or a toner component such as a release agent or a colorant dispersed in a monomer Examples thereof include emulsion polymerization. Here, the association means that a plurality of resin particles and colorant particles are fused.

  Reference numeral 5A denotes secondary transfer means, which includes a transfer roller 5AR made of a conductive rubber roller and a power source 5AE.

  6A is an intermediate transfer member cleaning means for cleaning the intermediate transfer member 7, and 8 is a fixing device for fixing the toner image to the transfer material P.

  On the other hand, after the secondary transfer to the transfer material P by the transfer roller 5A, the intermediate transfer body 7 passes through the intermediate transfer body cleaning means 6A and is cleaned.

  Reference numeral 9 denotes a charge applying means comprising a scorotron charger, which has a charging electrode 91 and a grid 92.

  Reference numeral 10 denotes a density sensor as density detection means for detecting the density of the toner image on the intermediate transfer body, and 11 denotes a potential sensor as potential detection means for detecting the surface potential of the intermediate transfer body 7.

  A condition setting process for setting the image forming process, the operating condition of the charge applying unit 9, and the operating condition of the secondary transfer unit 5A will be described with reference to FIGS. FIG. 2 is a block diagram of the control system, and FIG. 3 is a flowchart of the condition setting process.

  The control means CR for controlling the entire apparatus forms a toner image in the image forming portions 20Y, 20M, 20C, and 20K in the image forming process for forming an image on the transfer material P, transfers the toner image to the intermediate transfer member 7, and transfers the intermediate transfer member. 7 forms a multi-color toner image in which the single-color toner images overlap.

  The multicolor toner image on the intermediate transfer body 7 is transferred to the transfer material P by the secondary transfer means 5A and fixed by the fixing device 8.

  In the condition setting step, the control unit CR forms a first reference toner image having a predetermined shape and a predetermined density in one or more of the image forming units 20Y, 20M, 20C, and 20K in STEP 1 of FIG. Transfer to body 7.

  The first reference toner image having a predetermined shape and a predetermined density has a predetermined shape such as a rectangle or a circle, and causes the light source of the exposure apparatus to emit light with exposure data having a certain pixel value that forms a uniform density pattern. Is formed.

  It may be a yellow toner image, a magenta toner image, a cyan toner image, or a black toner image, or may be a superimposed image of two or more colors.

  The first reference toner image transferred onto the intermediate transfer member 7 passes through the potential sensor 11 due to the circular movement of the intermediate transfer member 7, and the potential of the toner image is detected by the potential sensor 11 (STEP 2).

  Based on the detected potential, the operating condition of the charge applying means 9 is set (STEP 3).

  The memory MR in FIG. 2 stores an operating condition of the charge applying unit 9 with respect to the potential of the toner image, that is, a look-up table of applied voltages to the charging electrode 91 and the grid 92, and the control unit CR stores the look-up table. See table. Select and set the appropriate charging electrode voltage and grid potential for the detected value.

  Next, the second reference toner image having the predetermined shape and the predetermined density is further formed in one or more of the image forming portions 20Y, 20M, 20C, and 20K, and formed on the intermediate transfer body 7 (STEP 4). The second reference toner image is charged by the charge applying means 9 that operates under the conditions set in STEP 3 (STEP 5).

  The potential sensor 11 detects the potential of the charged second reference toner image (STEP 6), and based on the detection result, the operating condition of the secondary transfer means 51, that is, the voltage applied by the power source 5AE is set. The applied voltage of the power source 5AE of the secondary transfer means 5A is stored in the memory MR as a lookup table of the appropriate voltage for the detected voltage, and the control means CR selects the applied voltage with reference to the lookup table. And set.

  In the image forming step, the charge applying unit 9 and the secondary transfer unit 5A operate under the operating conditions set in the condition setting step, and charge and secondary transfer the toner image.

  Note that the first reference toner image and the second reference toner image may be a single reference toner image.

  That is, the intermediate transfer member 1 is circulated one or more times, and the potential is detected by the potential sensor 11 without first charging the reference toner image by the charge applying means 9 and the reference toner image is not cleaned without intermediate cleaning. The body is circulated once and then charged when passing through the charge applying means 9, and the potential of the charged reference toner image is detected. Based on the first detected value, the operating condition of the charge applying unit 9 is set, and based on the next detected value, the operating condition of the secondary transfer unit 5A is set.

By setting the operating conditions of the charge applying means 9 and the secondary transfer means 5A described above, both the charge applying means and the secondary transfer means 5A are set optimally, and high transferability in the secondary transfer is stably maintained. High-quality images are stably formed.
<Embodiment 2>
FIG. 4 is a block diagram of a control system according to the second embodiment of the present invention, and FIG. 5 is a flowchart of a process for setting the operating condition of the charge applying unit 9.

  In the condition setting step of setting the operating condition of the charge applying unit 9, the control unit CR causes the light source of the exposure apparatus to emit light with exposure data of a certain pixel value forming a uniform density pattern, as in the first embodiment. As a result, a reference toner image is formed on the intermediate transfer member 7 (STEP 10).

  In STEP 11, the potential of the formed toner image is detected by the potential sensor 11, and in STEP 12, the density of the formed reference toner image is detected by the density sensor 10. Next, based on the detected potential and density of the reference toner image, in STEP 13, the operating condition of the charge applying unit 9, that is, the output voltages of the power supplies 91E and 92E are set. The output voltages of the power supplies 91E and 92E are selected from a lookup table having appropriate values for the density and potential of the reference toner image. Such a lookup table is stored in the memory MR.

  The potential of the toner image detected by the potential sensor 11 depends on the toner charge amount and the toner adhesion amount. In this embodiment, the toner density is detected by the density sensor 10 to detect the toner adhesion amount, and the toner adhesion is detected from the detected toner adhesion amount and the potential of the toner image detected by the potential sensor 11. The principle is that the charge amount is obtained and the operating condition of the charge applying means 9 is set on the basis of the obtained toner charge amount. By such control, the charge amount of the toner image to be secondarily transferred is determined. It becomes almost constant, and uniform and high transferability is maintained.

  Transferability in transfer depends on the charge amount of the toner, but when the charge amount of the toner is not more than a predetermined threshold value, that is, when the electrostatic force for attracting the toner to the intermediate transfer body 7 is not more than the predetermined value, an appropriate transfer property can be obtained. When the toner having a charge amount exceeding the threshold is on the intermediate transfer member 7, a phenomenon that the toner does not move from the intermediate transfer member 7 to the transfer material P occurs.

  Accordingly, a reference value of the potential of the toner image corresponding to the density of the toner image is set, and when the potential detected by the potential sensor 11 exceeds the reference value, charging is performed by the charge applying means 9 and the intermediate transfer member 7 is charged. By reducing the potential of the toner image, proper transfer can be performed.

Therefore, by setting a reference value of the potential of the toner image with respect to the image density and controlling the charge applying unit 9 based on the reference value, it is possible to maintain good transferability with simple control. .
<Embodiment 3>
The configuration of the image forming apparatus according to this embodiment is shown in FIGS. FIG. 6 is a flowchart of an operation condition setting process of the charge applying means 9 in the present embodiment.

In STEP 20, a reference toner image having patterns with different densities is formed on the intermediate transfer member 7. Such a toner image is formed by so-called wedge exposure in which a light emitting element of an exposure apparatus emits light with image data whose pixel value changes stepwise.
In STEP 21, the potential sensor 11 detects the density of the reference toner image of the intermediate transfer member 7, and in STEP 22, the voltage applied to the grid 92 of the charge applying unit 9 is set using the detected plurality of potentials.

  In the image forming process, the charge applying means 9 charges the intermediate transfer body 7 before the secondary transfer under the operating conditions set in the condition setting process, and the transfer by the secondary transfer means 5A is performed after the charging.

  Specific examples of settings in STEP 22 include the following.

  A reference potential is set, and the lowest potential that is equal to or higher than the reference potential among a plurality of potentials detected by the potential sensor 11 is selected. Then, the toner adhesion amount corresponding to the selected potential is determined.

  For example, when 10 levels of wedge exposure are performed, the toner adhesion amount from the first level with the highest density to the 10th level with the lowest density is measured in advance by experiments. Therefore, if it is known what pattern is selected, the toner adhesion amount is determined.

  If the toner adhesion amount is determined in this way, the corresponding potential is the reference potential, and therefore the toner charge amount is calculated from the toner adhesion amount and the reference potential.

  The optimum grid potential corresponding to the calculated toner charge amount is obtained in advance by experiments and stored in the memory MR as a lookup table.

  In this way, the control means CR sets the potential of the grid 92 in STEP22.

<Example 1 (Example of Embodiment 1)>
Using the image forming apparatus shown in FIG. 1, a yellow image and a magenta image are formed in the image forming unit 20Y, transferred to the intermediate transfer body 7, and a toner image having a uniform density formed by superimposing the toner image Was measured.

  The potential of the toner image was -170V.

  The output -110V of the power source 92E was set from a previously prepared lookup table of the potential of the toner image versus the grid potential. The applied voltage to the charging electrode 91 was fixed at +5 kV.

  Subsequently, the same two-color toner image as described above is formed on the intermediate transfer pair 7, and the intermediate transfer member 7 is charged under the set conditions of the charge applying unit 9, that is, the charging voltage +5 kV and the grid potential −110 V, The potential of the toner image after charging was detected to obtain -130V.

  From the look-up table of toner image potential versus secondary transfer voltage, the output voltage of the power source 5AE was set to +5 kV.

The image forming process was performed under the conditions set in this way, that is, the output of the power supply 91E + 5 kV, the output voltage of the power supply 92E−110V, and the output voltage of the power supply 5AE + 5 kV. Images were obtained stably.
<Example 2 (Example of Embodiment 2)>
Using the image forming apparatus shown in FIG. 1, a yellow image and a magenta image are formed in the image forming unit 20Y, transferred to the intermediate transfer member 7, and overlapped to form a toner image having a uniform density. Image potential and image density were measured.

  The potential of the toner image was −160 V and the image density was 1.4.

  The output −80 V of the power source 92E was set from a toner image potential and image density vs. grid potential lookup table prepared in advance. The applied voltage to the charging electrode 91 was fixed at +5 kV.

The image forming process was performed under the conditions set in this manner, that is, the output of the power supply 91E + 5 kV and the output voltage of the power supply 92E−80V. However, the secondary transfer rate is high, and a high-quality image is stably obtained. It was. Note that the output voltage of the power source 5AE in the secondary transfer in the image forming process was 4/5 kV.
<Example 3 (Example of Embodiment 3)>
Exposure was performed based on image data of 10-level pixel values, and a reference image was formed on the intermediate transfer member 7.

  As a result of setting the reference voltage to −100 V and comparing it with the detected potential of the toner image, the sixth pattern was the lowest potential exceeding the reference potential (toner potential −103 V).

  A step-to-grid potential lookup table from the highest density (toner adhesion amount) to the lowest density (toner adhesion amount) is prepared, and the grid potential for the sixth pattern from the lookup table is set to -70V.

  The image forming process was performed under the conditions set in this manner, that is, the output of the power source 91E + 5 kV and the output voltage of the power source 92E−70 V. However, the secondary transfer rate is high, and high-quality images can be stably obtained. It was. The output voltage of the power source 5AE in the secondary transfer in the image forming process was 5 kV.

1 is a diagram showing a color image forming apparatus according to an embodiment of the present invention. It is a block diagram of the control system of Embodiment 1, 3 of this invention. It is a flowchart of the condition setting process in Embodiment 1 of this invention. It is a flowchart of the control system of Embodiment 2 of this invention. It is a flowchart of the condition setting process in Embodiment 2 of this invention. It is a flowchart of the condition setting process in Embodiment 3 of this invention.

Explanation of symbols

1Y, 1M, 1C, 1K Photoconductor 5A Secondary transfer means 9 Charge applying means 10 Density sensor 11 Potential sensor 91 Charging electrode 92 Grid 5AE, 91E, 92E Power supply CR control means

Claims (6)

Image carrier,
Image forming means for forming a toner image on the image carrier;
Intermediate transfer member,
Primary transfer means for transferring a toner image on the image carrier to the intermediate transfer member;
Secondary transfer means for transferring a toner image onto a transfer material on the intermediate transfer member;
An intermediate transfer member cleaning means for cleaning the intermediate transfer member after the secondary transfer; and
In the image forming apparatus having a charge applying unit for applying a charge to the intermediate transfer body between the primary transfer unit and the secondary transfer unit,
Having a potential detection means and a control means for detecting the surface potential of the intermediate transfer member;
The control unit sets the operating condition of the charge applying unit based on the potential of the toner image on the intermediate transfer body before the charge applying by the charge applying unit detected by the potential detecting unit,
An operation condition of the secondary transfer unit is set based on the potential of the toner image on the intermediate transfer body after the charge is applied by the charge application unit detected by the potential detection unit. . The image forming apparatus according to claim 1, wherein the potential detection unit is disposed downstream of the charge applying unit and upstream of the secondary transfer unit with respect to a moving direction of the intermediate transfer unit. Image carrier,
Image forming means for forming a toner image on the image carrier;
Intermediate transfer member,
Primary transfer means for transferring a toner image on the image carrier to the intermediate transfer member;
Secondary transfer means for transferring a toner image onto a transfer material on the intermediate transfer member;
An intermediate transfer member cleaning means for cleaning the intermediate transfer member after the secondary transfer; and
In the image forming apparatus having a charge applying unit for applying a charge to the intermediate transfer body between the primary transfer unit and the secondary transfer unit,
A potential detection means for detecting the surface potential of the intermediate transfer member, a density detection means for detecting the density of the toner image on the intermediate transfer member, and a control means;
The control means is based on the potential of the toner image of the predetermined pattern formed on the intermediate transfer member detected by the potential detection means and the density of the toner image of the predetermined pattern detected by the density detection means. An image forming apparatus characterized in that an operating condition of a charge applying unit is set. The image forming apparatus according to claim 1, wherein the control unit controls the charge applying unit to apply a charge only when the potential detected by the potential detecting unit is equal to or higher than a predetermined reference value. Image carrier,
Image forming means for forming a toner image on the image carrier;
Intermediate transfer member,
Primary transfer means for transferring a toner image on the image carrier to the intermediate transfer member;
Secondary transfer means for transferring a toner image onto a transfer material on the intermediate transfer member;
Intermediate transfer member cleaning means for cleaning the intermediate transfer member after secondary transfer, and
In an image forming apparatus having a charging electrode and a grid, and having a charge applying unit that applies a charge to the intermediate transfer body between the primary transfer unit and the secondary transfer unit.
Having a potential detection means and a control means for detecting the surface potential of the intermediate transfer member;
The control unit controls the potential of the grid from a plurality of surface potentials of toner images formed on the intermediate transfer body and having different toner adhesion amounts detected by the potential detection unit. apparatus.   6. The control unit according to claim 5, wherein the control unit sets the grid potential based on the surface potential of a lowest value that exceeds a predetermined reference value among the plurality of surface potentials. Image forming apparatus.

Images