JP2008107398A - Remaining toner deposition amount detection method, transfer output control method, and image forming method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of detecting transfer property changes caused by the variations in the transfer roller resistance at a low cost, and also provide a transfer output control method to obtain the optimal transfer output by using the information obtained by the above method and an image forming device using it. <P>SOLUTION: This remaining adhered toner amount detection method transfers a test toner image formed on the intermediate transfer component 501 serving as an image carrier (not shown) to the secondary transfer roller 510 working as a transfer component, and checks the amount of the toner not used for transferring and remaining on the intermediate transfer component 501 by using a sensor S. It controls the transfer output (transfer current, transfer voltage, etc.) to the transfer component (secondary transfer roller 510) based on the detected remaining toner deposition amount to make it optimal. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to transfer control in an image forming apparatus such as a copying machine, a printer, or a facsimile.

Japanese Patent No. 2704277 JP-A-5-181373 JP-A-10-301408 JP-A-2005-242170 JP 2006-145950 A

  In image forming apparatuses such as copiers, printers, and facsimiles, the transfer output applied when transferring a toner image from an image carrier onto a recording material has an optimum value depending on the temperature and humidity environment, the type and width of the recording material, etc. to differ greatly. Therefore, conventionally, control is performed by using a table, a function, or the like so as to obtain an optimal transfer output for each image forming condition.

  However, both the table and the function are derived from the experiment by the designer in advance, so if the resistance value of the part related to the transfer part is out of the expected range, the bias that must be output is large. A different bias is applied, which may cause transfer failure or abnormal discharge.

  In particular, the transfer roller used in the roller transfer system has a resistance value such as dispersion of inorganic conductive particles such as carbon in rubber or sponge, or use of ion conductive rubber kneaded with a surfactant or the like. It is a roller having an appropriately adjusted elastic layer, and it is well known that the resistance value of this transfer roller fluctuates by an order of magnitude or more due to variations in manufacturing, temperature and humidity, resistance change due to long-term use, and the like. The table control method and function control method described above are designed in consideration of their fluctuations, so that even if the optimum value cannot be pinpointed, the occurrence of an abnormal image is rare.

  However, when continuous paper passing (especially double-sided continuous paper passing), the heat from the fixing device propagates around the transfer roller, and the temperature of the transfer roller rises and the roller resistance decreases. It can be seen. Furthermore, in the case of continuous double-sided paper passing, once the recording material that has passed through the fixing device repeatedly contacts the roller, heat is transferred from the recording material to the transfer roller, and the roller is heated, resulting in a decrease in roller resistance. The phenomenon of end up being seen. On the other hand, the temperature / humidity sensor is usually attached at a position that is not easily affected by exhaust heat of the apparatus in order to measure the environment (outside air) around the apparatus. For this reason, when the device is on standby or when passing paper between job intervals (non-continuous paper passing), the temperature and humidity detected by the sensor and the temperature and humidity of the transfer roller itself are almost the same, but continuous As the paper is carried out, the temperature and humidity detected by the sensor does not change, but the temperature and humidity of the transfer roller changes greatly. In both the table control method and the function control method, the control value is determined based on the temperature and humidity detected by the sensor, so that an insufficient bias is applied even though the actual roller resistance is greatly reduced. It will be.

  As countermeasures, a temperature / humidity sensor may be provided near the transfer roller, or the temperature may be detected by a thermistor that contacts the transfer roller. However, it is difficult to use a thermistor with a sponge roller, etc. However, there is a problem that the temperature and humidity of the transfer roller itself cannot be quickly followed, and the cost is increased by adding a sensor.

  As another countermeasure, a bias is applied to the transfer roller separately from the time of image formation, the transfer roller resistance data is obtained from the current and voltage values at that time, and the transfer output is feedback-controlled, so it is always optimal. A method of applying an appropriate bias is widely known (Patent Documents 1 to 4). In this method, the actual transfer roller resistance is measured, so the transfer output value is unlikely to deviate significantly from the optimum value, but it is necessary to prepare a dedicated circuit and power pack, which also increases costs. There is a problem of end up.

Further, Patent Document 5 proposes a method for controlling transfer output by forming a density detection patch and detecting a transfer residual toner density when the patch is transferred from an image carrier to a recording material. Yes. However, this method has the following drawbacks.
1) Since the image is unnecessary for the user, the output recording material is wasted.
2) The recording materials used by the user are diverse, and the thickness, resistance, etc. are different for each type. In addition, the recording material used in one image forming apparatus is not limited to one type. Therefore, even when the transfer output is controlled by performing the method described in Patent Document 5 using a certain type of recording material, an appropriate transfer output can be applied to a recording material having a thickness or resistance value different from that of the recording material. It cannot be guaranteed whether it is. Even if the manufacturer specifies and provides a specific recording material with characteristics suitable for control for transfer output control, the resistance of the recording material varies greatly depending on the humidity control condition. There are cases where the transfer output cannot be controlled.
3) With the optimum transfer output and the output in the vicinity thereof, the amount of residual toner is naturally low, the toner density is very low, and the toner amount is at most 0.05 mg / cm ^ 2 or less (that is If the above toner amount remains, the transfer system itself is not sufficiently optimized). In order to detect the toner density in such a low adhesion amount region, a detectable range is not sufficient with a general density sensor. For this reason, it is necessary to prepare a concentration sensor having sufficient resolution even in a low concentration region, resulting in an increase in cost.

  The present invention has been made in view of the above problems, and its object is to detect a change in transferability due to a change in transfer roller resistance at a low cost without requiring a new member or a high-performance / high-cost member. A transfer output control method capable of obtaining an optimal transfer output even when the temperature and humidity of the transfer roller fluctuate by providing a method and correcting and controlling the transfer output based on the obtained detection information, and using the same An image forming apparatus is provided.

  According to the present invention, the above-described problem is that the detection toner image carried on the image carrier is transferred to a transfer member for transferring the toner image carried on the image carrier to a recording medium, and transferred to the transfer member. The problem is solved by detecting the amount of remaining toner remaining on the image carrier without being detected.

It is also preferable to clean the toner transferred to the transfer member after detecting the amount of residual toner remaining on the image carrier.
The cleaning is preferably performed by alternately applying a bias having the same polarity and a reverse polarity to the toner to the transfer member.

  In the case where the image carrier is an intermediate transfer member and the transfer member is a secondary transfer member, the cleaning is a counter member disposed to face the secondary transfer member with the intermediate transfer member interposed therebetween. Preferably, the bias is applied to the secondary transfer member, and the secondary transfer member is grounded.

The cleaning is preferably performed by a cleaning member that contacts the transfer member.
Further, according to the present invention, the above-described problem is applied to the transfer member based on the residual toner adhesion amount of the image carrier detected by the residual toner adhesion amount detection method according to claim 1. This is solved by a transfer output control method for controlling the transfer output.

The transfer output is preferably a transfer current.
The transfer output is preferably a transfer voltage.
Further, according to the present invention, there is provided an image forming method using an electrophotographic method, wherein the residual toner adhesion amount detection method according to any one of claims 1 to 5 or any one of claims 6 to 8. This is solved by an image forming method using the transfer output control method described in item 1.

  Also, a predetermined transfer condition is determined based on the residual toner adhesion amount of the image carrier detected before entering the image forming operation and the residual toner adhesion amount of the image carrier detected during or after the image forming operation. Is preferably corrected.

Further, it is preferable that the image forming operation is an image forming operation at the time of duplex printing.
Further, when the image forming operation is performed again within a fixed time after the image forming operation is completed, it is preferable to correct the transfer condition.

Moreover, the said subject is solved by the image forming apparatus using the image forming method of any one of Claims 9-12 by this invention.
Preferably, the image carrier is an intermediate transfer member, and the transfer member is a secondary transfer member.

  According to the remaining toner adhesion amount detection method of the first aspect, since the recording medium is not used for the detection, the recording medium is not wasted and is not affected by the type of the recording medium. Detection can be performed. Further, it is not necessary to use a highly accurate and expensive sensor for detection, and the cost can be suppressed. Further, since the detection with excellent S / N ratio reflecting the transfer rate of the transfer member itself without a recording medium can be performed, the remaining toner adhesion amount can be detected with high accuracy.

According to the method of the second aspect, since the transfer member is cleaned after detection, it is possible to prevent the toner from adhering to the recording medium from the transfer member during the next image forming operation.
According to the third aspect of the present invention, the transfer member can be cleaned without adding a cleaning member or the like by cleaning the transfer member by bias cleaning. In addition, since the bias having the same polarity as that of the toner and the bias having the opposite polarity are alternately applied, not only the normal toner but also the reversely charged toner and the weakly charged toner can be cleaned.

According to the method of claim 4, the secondary transfer member in the intermediate transfer system can be efficiently cleaned.
By providing the cleaning member for cleaning the transfer member according to the method of claim 5, the cleaning can be performed immediately (before the transfer roller makes one revolution), so that the time required for detection can be shortened and the productivity is improved. Is not reduced.

  According to the transfer output control method of the sixth aspect, the change in the resistance of the transfer member can be detected with high accuracy by the residual toner adhesion amount detection method in which the resistance of the transfer member is reflected with a good S / N ratio. In the transfer output control based on this, the optimum transfer output suitable for the transfer member resistance can be obtained. That is, even when the resistance of the transfer member changes due to environmental conditions, aging, continuous printing, or the like, it is possible to obtain an optimal transfer output and to exhibit excellent transfer performance.

According to the method of claim 7 or claim 8, excellent transfer performance can be exhibited by a transfer current value or transfer voltage value suitable for transfer member resistance.
According to the image forming method of claim 9, it is possible to obtain an appropriate transfer output even when the resistance of the transfer member changes due to environmental conditions, aging or continuous printing, and a high-quality output image with excellent transfer performance. Can be obtained.

  According to the method of the tenth aspect, since the transfer condition is corrected based on the detection results before the image forming operation and during or after the image forming operation, it is more suitable for the actual resistance value of the transfer member. Therefore, it is possible to control the transfer output and obtain a higher quality output image.

  According to the method of the eleventh aspect, it is possible to obtain an optimal transfer output even when there is an influence of heat from the fixing device in double-sided printing, and a high-quality double-sided printed matter can be obtained.

  According to the method of claim 12, when the image forming operation is performed again within a predetermined time after the image forming operation is completed, the transfer condition is corrected. Can be obtained.

  According to the image forming apparatus of the thirteenth aspect, it is possible to obtain an appropriate transfer output even when the resistance of the transfer member changes due to environmental conditions, aging or continuous printing, and a high-quality output image with excellent transfer performance. Can be obtained.

  According to the structure of the fourteenth aspect, an accurate secondary transfer output can be obtained in the intermediate transfer type image forming apparatus, and a high-quality output image can be obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description, specific member names are used to facilitate understanding of the invention, but it should be clearly stated that the scope to which the present invention can be applied is not limited thereby. In particular, as an application example, an image forming apparatus using a tandem type intermediate transfer system is taken up and secondary transfer from an intermediate transfer body to a secondary transfer roller is described. However, the present invention is limited to an intermediate transfer system. It is not done. For example, the same operation and effect can be obtained even in a mode in which a direct transfer method is employed in which the image carrier is a photoconductor.

  FIG. 1 is a cross-sectional view showing a schematic configuration of a color printer which is an example of an image forming apparatus according to the present invention. The color printer shown in this figure is a tandem type intermediate transfer type electrophotographic apparatus, and includes an image forming unit 100, a writing optical unit 600, a paper feeding unit 700, a fixing unit 800, a double-sided unit 900, and the like.

  As shown in FIG. 1 and FIG. 2 in an enlarged manner, in this example employing the tandem type intermediate transfer system, along the lower running side of the intermediate transfer belt 501 that is driven to rotate in the direction of arrow A in the figure. Four image forming process units corresponding to the respective color toners of yellow (Y), cyan (C), magenta (M), and black (K) are arranged.

  An intermediate transfer member 501 made of rubber or resin having a single layer or a multilayer structure is stretched by a secondary transfer counter bias application roller 502 and support rollers 503, 508, and 509, and rotates counterclockwise in the illustrated example. Driven. In addition, the secondary transfer roller 510 is disposed on the opposite side of the intermediate transfer body 501 with respect to the secondary transfer counter bias application roller 502 so as to face the secondary transfer counter bias application roller 502.

  The secondary transfer counter bias applying roller 502 can form an electric field having the same polarity as that of toner by a secondary transfer electric field forming unit (not shown), and the electrostatic repulsive force generated thereby can be used for transfer. The toner can be secondarily transferred to the material.

An intermediate transfer member cleaning device 520 that removes residual toner remaining on the intermediate transfer member 501 after image transfer is provided on the left side of the support roller 509.
FIG. 3 is an enlarged view of the intermediate transfer member cleaning device 520. The intermediate transfer member cleaning device 520 includes a blade member 521 for removing a toner image, a coil member 524 for conveying the removed toner image to a waste toner tank of the main body, a lubricant 523, and a lubricant application brush 522. Has been. The contact angle, position, pressure, and the like of the blade member 521 are appropriately set depending on the toner used, the image forming speed of the apparatus, and the like. The lubricant 523 is pressed against the lubricant application brush 522 by means such as a spring or a weight, and the lubricant application brush 522 scrapes the lubricant 523 while rotating and applies the lubricant to the intermediate transfer member 501. I do.

  Further, primary transfer bias rollers 504, 505, 506, and 507 that form an electric field at the time of primary transfer are arranged inside the intermediate transfer member 501 of the support roller 503 and the support roller 508 so as to be in contact with the intermediate transfer member 501. Has been.

  Then, on the opposite side of the primary transfer bias rollers 504, 505, 506, and 507 across the intermediate transfer member 501, four photosensitive members 101, 102, 103, yellow, cyan, magenta, and black are arranged along the transport direction. A tandem image forming apparatus is configured by arranging image forming process units centered on 104.

  Around each of the photoconductors 101 to 104, photoconductor charging units 201 to 204, photoconductor cleaning units 301 to 304, and developing units 401 to 404 are arranged, respectively.

  FIG. 4 shows the details of the photoconductor cleaning means 301 to 304. The photosensitive member cleaning units 301 to 304 include a blade member 311 for removing a toner image, a coil member 314 for conveying the removed toner image to a waste toner tank of the main body, a lubricant 313, and a lubricant application brush 312. It is configured. The contact angle, position, pressure, and the like of the blade member 311 are appropriately set depending on the toner used, the image forming speed of the apparatus, and the like. The lubricant 313 is pressed against the lubricant application brush 312 by means such as a spring or a weight, and the lubricant application brush 312 scrapes the lubricant 313 while rotating to apply the lubricant to the photoconductors 101 to 104. Perform the action.

  Writing exposure to the photosensitive member is performed by laser irradiation from a writing optical unit (exposure device) 600 shown in FIG. 1 at a position between the photosensitive member charging units 201 to 204 and the developing units 401 to 404.

  A registration roller 703 that feeds the recording medium to the secondary transfer unit is installed under the secondary transfer roller 510, and a fixing device 800 that fixes the toner image on the recording medium is installed above the registration roller 703.

A printing operation in the color printer configured as described above will be briefly described.
First, an image signal is input from an external device such as a personal computer or a scanner (not shown). After inputting the signal, the photosensitive members 101 to 104 and the intermediate transfer member 501 are rotated by a drive motor (not shown) at a predetermined timing.

  Simultaneously with the photoconductors 101 to 104, a preliminary cleaning operation by the photoconductor cleaning units 301 to 304 is performed, and thereafter, a charging operation by the photoconductor charging units 201 to 204, an exposure operation by the writing optical unit 600, and a developing unit 401 to 404. Development operation is performed. The toner images formed on the photoreceptors 101 to 104 in this way are primarily transferred onto the intermediate transfer member 501 by forming an electric field having a polarity opposite to that of the toner on the primary transfer bias rollers 504 to 507 at predetermined timings, respectively. A monochromatic or multicolored visible image is formed. At that time, the toner images remaining on the photoconductors 101 to 104 without being completely transferred onto the intermediate transfer body 501 are cleaned by the photoconductor cleaning units 301 to 304, respectively.

  On the other hand, after the input of the image signal, the recording medium is fed out from the paper feeding unit 700 at a predetermined timing, and is abutted against the registration roller 703 and temporarily stopped. Then, the registration roller 703 is rotated in synchronization with the visible image on the intermediate transfer member 501, and the recording medium is fed between the intermediate transfer member 501 and the secondary transfer roller 510.

  At the same time, an electric field having the same polarity as the toner is formed on the secondary transfer counter bias applying roller 502 by the secondary transfer electric field forming means, and the visible image on the intermediate transfer member 501 is secondarily transferred onto the recording medium.

Thereafter, the recording medium passes through the fixing device 800, and heat and pressure are applied to fix the visible image on the transfer material. The sheet after fixing is discharged and stacked on a discharge tray 40 on the upper surface of the apparatus.
On the other hand, the toner image remaining on the intermediate transfer member 501 without being completely transferred onto the recording medium during the secondary transfer is removed by the intermediate transfer member cleaning device 520 to prepare for the image formation again.

  Further, a reflection type photosensor S as an image density detection unit is disposed above the secondary transfer counter bias application roller 502 so as to output a signal corresponding to the light reflectance on the intermediate transfer body 501. It is configured. In this reflection type photosensor S, either a diffuse light detection type or a regular reflection light detection type, the difference between the amount of reflected light on the surface of the intermediate transfer body 501 and the amount of reflected light of a reference pattern image to be described later can be made a sufficient value Is used.

Next, a toner adhesion amount detection method using the reflective photosensor S and a normal image density control method using the toner adhesion amount detection method will be described.
In the color printer of this embodiment, the image in each image forming process unit is at a predetermined timing, such as when the main power is turned on, when waiting after a predetermined time has elapsed, or when waiting after a predetermined number of prints have been output. It is configured to test imaging performance such as formation performance.

  Specifically, when the predetermined timing comes, first, the photosensor S is calibrated. In a state where no image is formed, the amount of light emitted from the photosensor is sequentially changed to obtain the amount of light emitted so that the detection voltage is 4.0 V ± 0.2 V. This emitted light quantity is used when detecting the toner adhesion amount of the patch pattern. Next, the photoreceptors 101 to 104 are uniformly charged while rotating. With respect to this charging, unlike the uniform charging (for example, −700 V) during normal printing, the potential is gradually increased. Then, developing is performed by the developing means 401 to 404 while forming an electrostatic latent image for a reference pattern image by scanning with the laser light. By this development, bias development pattern images of the respective colors are formed on the photoreceptors 101 to 104. During development, a control unit (not shown) of the printer controls so that the value of the developing bias applied to the developing roller of each developing unit 401 to 404 is gradually increased. In this way, an image is formed from a pattern having a low image density, and a gradually dark pattern is formed. Details of this pattern image forming method will be described later. Conversely, if both the charging and developing biases are gradually lowered, an image is formed from a pattern with a high image density, and a thin pattern is gradually created. In general, however, the voltage of a high-voltage power supply is lower than the voltage is increased. However, since it takes time, there is a disadvantage that the pattern image forming time becomes long.

  The bias development pattern images P of these colors are transferred so as to be arranged on the intermediate transfer body 501 without overlapping. When each of the pattern images passes through a position facing the reflective photosensor S as the intermediate transfer member 501 moves endlessly, the amount of reflected light is detected and output as an electric signal to the control unit. The control unit calculates the light reflectance of each reference image based on the output signal sequentially sent from the reflection type photosensor S, and stores it in the storage means (RAM) as density pattern data. The pattern that has passed through the position facing the reflective photosensor S is cleaned by the intermediate transfer member cleaning device 520.

  FIG. 5 is a schematic diagram showing the reference pattern image P (Py (not shown), Pm (not shown), Pc, Pk). In FIG. 5, the reference pattern image P is composed of ten reference images arranged at intervals of 13 mm. In this color printer, each reference image P is 13 mm long × 15 mm wide and is formed through a 13 mm gap. Therefore, the lengths of the reference pattern images Pk, Pm, Pc, and Py on the intermediate transfer member 501 are L2 = 247 mm, respectively. The reference pattern images Pk, Pm, Pc, and Py are different from the toner images of the respective colors formed during the printing process, and are arranged so that they are arranged in the order of Py, Pm, Pc, and Pk without overlapping on the intermediate transfer member 501. Are formed and transferred to the intermediate transfer member 501.

  The reflective photosensor S detects the amount of reflected light from each reference image constituting the reference pattern images Pk, Pc, Pm, Py in the following order. That is, detection is performed in the order of 10 reference images of the reference pattern image Pk, 10 reference images of the reference image Pc, 10 reference images of the reference image Pm, and 10 reference images of the reference image Py. At this time, a voltage signal corresponding to the light reflection amount of each reference image is detected by a method described later, and sequentially output to the control unit. The control unit sequentially calculates the image density of each reference image based on the voltage signals sequentially sent from the reflective photosensor S and stores them in the RAM. The image density of each reference image is converted into a toner adhesion amount by the following method. FIG. 6 is a graph showing the relationship between the toner adhesion amount and the sensor detection output. The detection output of 10 reference pattern images for each color is converted into the toner adhesion amount of the reference image from the relationship between the detection output (voltage) and the toner adhesion amount shown in FIG. 6 and stored in the RAM. Here, the toner adhesion amount is stored in the RAM, and at the same time, the development potential of the reference pattern is estimated from the image forming conditions of the reference pattern for each color, and the reference pattern information is also stored in the RAM.

  The above steps are sequentially performed in the order of Pk1, Pc1, Pm1, and Py1. FIG. 7 is a plot of the relationship between the development potential of each reference pattern and the toner adhesion amount obtained here on the XY plane.

In FIG. 7, potential potential (difference between development bias and pattern image potential: VB−VD) [unit V] is assigned to the X axis, and toner adhesion amount M / A [mg / cm ² ] per unit area is assigned to the Y axis. Yes. A straight line area is selected from the plotted data, and a linear equation (A) obtained by performing a straight line approximation by applying the least square method to the data in the section is calculated for each color. Image density control, so-called process control (process control) is performed by calculating a potential at which a target adhesion amount can be obtained by this linear equation and feeding back to the image forming conditions.

Next, the gist of the present invention will be described.
In the color printer of this embodiment, the detection toner image carried on the intermediate transfer member 501 as the image carrier is transferred to the secondary transfer roller 510 as the transfer member, and the intermediate transfer member 501 is not transferred. The amount of residual toner remaining on the surface is detected by the sensor S, and the transfer output (transfer current value, transfer voltage value, etc.) to the transfer member (secondary transfer roller 510) is controlled based on the detected residual toner adhesion amount. By doing so, the optimum transfer output can be obtained.

  As described above, an image forming apparatus using a tandem type intermediate transfer system is taken up as an application example of the present invention, and secondary transfer from an intermediate transfer body to a secondary transfer roller is described. It is not limited to the intermediate transfer type. For example, the same operation and effect can be obtained even in a form using a direct transfer system in which the image carrier is a photoconductor.

  Now, when detecting the secondary transfer residual toner adhesion amount, the secondary transfer roller 510 is kept in contact with the intermediate transfer member 501. One or more types of detection pattern images may be selected from a plurality of pattern images used during normal image density control. However, since the detection target is the transfer residual toner adhesion amount, among the plurality of pattern images used during normal image density control, the low transfer pattern image has too little transfer residual toner adhesion amount, and the detection accuracy is lowered. It is desirable to use a high density image pattern because there is a risk.

  The pattern image can be created by any of the four image forming process units. However, if the most downstream photoconductor 104 is used, the detection operation time is shortened compared to the case of using another photoconductor. can do. Further, when black is placed on the most downstream side, the reflection type photosensor S may be a regular reflection light detection type. When detecting the toner adhesion amount, the reflection type photosensor S is preliminarily based on the gradation pattern acquired during normal image density control. There is also an advantage that there is no need to perform complicated calculations. In addition, if the device is equipped with a black single-color mode that separates the photoconductor other than black from the intermediate transfer member, it is possible to extend the unit life because it is not necessary to rotate the developer and photoconductor other than black. it can. A part of the pattern image transferred to the intermediate transfer member 501 is transferred to the secondary transfer roller 510 by the negative constant current output bias applied by the secondary transfer counter bias applying roller 502. However, since there is no recording material existing between the intermediate transfer member and the secondary transfer roller 510 in the secondary transfer at the time of normal image formation, the transfer rate is lower than that at the time of normal image formation. Therefore, it is possible to leave a toner adhesion amount necessary and sufficient for the reflection type photosensor S to detect as the transfer residual toner on the intermediate transfer body 501. In the reflection type photosensor S used in the experiment, accurate detection was possible if the toner adhesion amount was between 0.10 and 0.60 mg / cm 2.

  On the other hand, if a part of the pattern image is transferred to the secondary transfer roller 510 as described above, the toner will be transferred to the back surface of the recording material in the next normal printing, which is called back stain. Will occur. Therefore, in order to clean the toner transferred to the secondary transfer roller 510, a bias is applied to the secondary transfer counter bias application roller 502, and the toner is transferred from the secondary transfer roller 510 to the intermediate transfer member 501 again. , Prevents the occurrence of back dirt. However, although the toner is normally negatively charged, there are also reversely charged and weakly charged toners, so it is necessary to apply a positive bias and a negative bias, respectively. Table 1 shows the results of an experiment on how many roller rotations should be applied with each polarity bias set to ± 1 kV. As the secondary transfer roller 510, a sponge roller made of urethane material was used. As a result, it was found that the plus bias should be applied for two or more rollers and the minus bias should be applied for one or more rollers.

  Further, as a cleaning method, the secondary transfer roller 510 is made of solid rubber instead of sponge, or the surface layer of the sponge roller is coated with, for example, fluorine resin, and the same as the intermediate transfer member cleaning device 520 as shown in FIG. It is also possible to provide the cleaning device 530 having the configuration with respect to the secondary transfer roller 510. In the bias cleaning, normal printing cannot be performed during cleaning. However, when the cleaning mechanism as shown in FIG. 8 is provided, the toner is cleaned before the secondary transfer roller 510 makes one round. It is possible to detect the amount of toner remaining after transfer between the recording materials (between sheets). As a result, it is possible to detect the amount of toner remaining after transfer without downtime.

  The transfer output during normal image formation can be controlled using the transfer residual toner adhesion amount thus detected. For example, the amount of toner remaining after transfer at the reference detection current in the standard state is obtained as described above in an experiment, and in the transfer output control, a detection current is used so that the amount of toner remaining after transfer is always constant. Ask. Then, the post-control imaging current is determined so that the ratio between the reference detection current and the detection current is the same as the ratio between the imaging reference current and the post-control imaging current.

A specific example is given.
When an experiment was performed using a pattern image in which the toner adhesion amount before secondary transfer was 0.50 mg / cm ^ 2 in an environment of a temperature of 22 ° C. and a humidity of 55%, the transfer was performed at a detection current of 60 μA. The residual adhesion amount was 0.21 mg / cm ^ 2. The secondary transfer roller resistance was 7.1 LogΩ. Further, it is assumed that the transfer current at the time of image formation, which is determined in advance by experiment, is 20 μA. Now, the transfer residual toner adhesion amount is measured by the above method while changing the transfer current, and a detection current is obtained such that the toner adhesion amount is 0.21 mg / cm 2. If the obtained detection current is 75 μA, the ratio is obtained such that 60: 75 = 20: x, where “x” μA is the transfer current during image formation after control. In this case, x = 25 μA.

  As described above, the transfer residual toner adhesion amount of the intermediate transfer member 501 detected by the above method reflects the resistance of the secondary transfer roller 510 with a favorable S / N ratio as will be described later. As a result, the transfer output control based on this change can provide an optimum transfer output suitable for the transfer member resistance. That is, even when the resistance of the transfer member changes due to environmental conditions, aging, continuous printing, or the like, it is possible to obtain an optimal transfer output, and it is possible to obtain a high-quality output image by preventing transfer failure.

  Further, since the recording material is not used in the detection of the transfer residual toner adhesion amount according to the present invention, 1) the recording material is wasted, and 2) the characteristic value such as the resistance value differs depending on the type of the recording material. The point can be avoided. Further, when only the transfer roller is used, the overall resistance of the transfer system is lower than when the recording material is included. Therefore, as shown in FIG. 9 comparing the conventional example (Patent Document 5) with the present invention, the transfer to the transfer roller is performed at the rising portion before the transfer rate curve is saturated in the detection method according to the present invention. The change in the residual toner amount with respect to the change in the transfer roller resistance is sensitive (S / N is good). Further, since density detection is performed in an area where there is a large amount of residual toner, a general density detection sensor used for a process controller or the like can be used as it is. Therefore, it does not increase the cost by adding new members or high-performance / high-cost members.

  By the way, it is possible to control the transfer current optimally for the device more accurately by using the current / attachment amount that is detected before image formation as the control reference (because individual differences exist in the device, In the above-described method obtained by experiments, the accuracy of control is reduced by the variation of component resistance and the like).

  Therefore, the transfer residual toner adhesion amount detected before image formation is compared with the transfer residual toner adhesion amount detected during or after the image forming operation, and the transfer output is controlled (corrected) based on the comparison. Furthermore, an optimum transfer output suitable for the actual transfer member resistance can be obtained. Hereinafter, the control will be described.

  For simplification of explanation, it is assumed that the detection information before image formation is the same as the above condition (the toner adhesion amount before secondary transfer is 0.50 mg / cm ^ in a temperature 22 ° C., humidity 55% environment). 2. At a detection current of 60 μA, the transfer residual adhesion amount is 0.21 mg / cm ^ 2, and the secondary transfer roller resistance is 7.1 LogΩ. Next, after image formation, after full-size (A3 for A3 machine, A4 for A4 machine) double-sided continuous 20 sheets, the secondary transfer current is shaken around 60 μA, and the secondary at that time The amount of toner remaining after transfer was detected. The relationship between the secondary transfer current and the transfer residual toner adhesion amount is shown in the graph of FIG. Since the temperature rises due to continuous paper passing and the resistance of the secondary transfer roller decreases, the transferability is insufficient at 60 μA, which is the same as before double-sided paper passing, so the amount of toner remaining after transfer increases. When the detection current was increased in order to improve the transferability that was lowered due to the decrease in resistance, a transfer residual toner adhesion amount of 0.23 mg / cm 2 was obtained at 75 μA. From the information before and after the image formation, the transfer current can be determined using the ratio of the detection current as described above.

  As another method, a control method that gently reflects the detection result on the transfer current may be used. For example, when the control table is used as the environmental correction control, in the normal case, it is determined which environmental classification of the control table is applied and output from the temperature and humidity information of the outside air. When the transfer roller temperature rises regardless of the outside air temperature, control may be performed so that the environmental classification is shifted to the high temperature and high humidity side and the transfer current is output. In this case, the transfer current after the control may become a value around the optimum value, but it is considered that the transfer current is improved as compared with the case where the control is not performed.

  During double-sided printing, the recording material heated by passing through the fixing device after the first surface transfer comes into contact with the transfer roller during the second surface transfer, so the amount of heat is transferred from the recording material to the transfer roller, and the temperature of the transfer roller Rises. Thereby, the resistance drop due to the temperature increase of the transfer roller becomes more remarkable than that during single-sided printing. However, the transfer residual toner adhesion amount detected before image formation described above during duplex printing is compared with the transfer residual toner adhesion amount detected during or after the image forming operation, and the transfer output is controlled (corrected) based on that comparison. ), An optimal transfer output can be obtained.

  Further, not only during printing or immediately after printing, but also the transfer roller whose temperature has once increased has low resistance until the temperature decreases. Therefore, an appropriate secondary transfer current can always be obtained by performing correction control based on the detection information before and after the image forming operation within a certain time after the end of printing. In the experiment conducted by the present inventor, as shown in the graph of FIG. 11 showing the relationship between the elapsed time after double-sided printing and the necessary transfer output (secondary transfer voltage), the lowered secondary transfer roller resistance is increased. The necessary transfer output (calculated as a control value) increases (returns to the original value), and the secondary transfer roller resistance almost returns to the original level when 4 hours or more have elapsed after double-sided printing. Therefore, for example, in the case of within 4 hours after double-sided continuous printing, it is preferable to perform correction control based on the detection information before and after the image forming operation.

Although the present invention has been described above with reference to the illustrated examples, the present invention is not limited thereto.
As a sensor for detecting the adhesion amount of the remaining toner, a sensor having an appropriate configuration and form can be used, and a detection pattern having an appropriate shape and number can be adopted. An appropriate configuration for cleaning the transfer member may be employed.

  The image forming apparatus is not limited to a printer, but may be a facsimile, a copying machine, or a multifunction machine having a plurality of functions. The number of colors in the image forming apparatus is not limited to four, and any number of colors may be used.

  The present invention can also be applied to a monochrome machine using a single image carrier, a color machine having a plurality of developing devices arranged around one image carrier, or a color machine using a revolver type developing device. is there. Further, the present invention is not limited to the intermediate transfer method described in the embodiment, but can be applied to an apparatus of a direct transfer method. The transfer member is not limited to the transfer roller, and a transfer belt or the like is also possible.

1 is a cross-sectional view illustrating a schematic configuration of a color printer which is an example of an image forming apparatus according to the present invention. It is an enlarged view of an image formation part. FIG. 3 is an enlarged view of an intermediate transfer body cleaning device. It is an enlarged view of a photoconductor cleaning means. FIG. 6 is a schematic diagram illustrating a reference pattern image used for detection of toner adhesion amount. 6 is a graph showing a relationship between toner adhesion amount and sensor detection output. 6 is a graph in which a relationship between a development potential of a reference pattern and a toner adhesion amount is plotted on an XY plane. It is a cross-sectional block diagram which shows the cleaning apparatus of a transfer member. It is a graph which compares the detection accuracy in the detection method of a prior art example and this invention. 6 is a graph showing a relationship between a secondary transfer current and a transfer residual toner adhesion amount. It is a graph which shows the relationship between the elapsed time after double-sided printing, and required transfer output.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Image forming part 101 Photoconductor 501 Intermediate transfer body (image carrier)
502 Secondary transfer counter bias application roller 510 Secondary transfer roller (transfer member)
520 Intermediate transfer member cleaning device 600 Writing optical unit 700 Paper feeding unit 800 Fixing unit 900 Double-sided unit 703 Registration roller Pk, Pc Reference pattern image S Reflection type photo sensor (image density detection means)

Claims (14)

The toner image for detection carried on the image carrier is transferred to a transfer member for transferring the toner image carried on the image carrier to a recording medium, and is not transferred onto the transfer member but on the image carrier. A method for detecting a residual toner adhesion amount, comprising: detecting an adhesion amount of a remaining residual toner. 2. The residual toner adhesion amount detection method according to claim 1, wherein the toner transferred to the transfer member is cleaned after detecting the adhesion amount of the residual toner remaining on the image carrier. The residual toner adhesion amount detection method according to claim 2, wherein the cleaning is performed by alternately applying a bias having the same polarity and a reverse polarity to the toner to the transfer member. In the case where the image carrier is an intermediate transfer member and the transfer member is a secondary transfer member, the cleaning is performed with respect to a counter member disposed to face the secondary transfer member with the intermediate transfer member interposed therebetween. 4. The residual toner adhesion amount detection method according to claim 3, wherein the bias is applied to ground the secondary transfer member. The residual toner adhesion amount detection method according to claim 2, wherein the cleaning is performed by a cleaning member in contact with the transfer member. A transfer output to the transfer member is controlled based on a residual toner adhesion amount of the image carrier detected by the residual toner adhesion amount detection method according to claim 1. Output control method. The transfer output control method according to claim 6, wherein the transfer output is a transfer current. The transfer output control method according to claim 6, wherein the transfer output is a transfer voltage. An electrophotographic image forming method using the residual toner adhesion amount detection method according to any one of claims 1 to 5 or the transfer output control method according to any one of claims 6 to 8. An image forming method characterized by comprising: Predetermined transfer conditions are corrected based on the residual toner adhesion amount of the image carrier detected before entering the image forming operation and the residual toner adhesion amount of the image carrier detected during or after the image forming operation. The image forming method according to claim 9, wherein: The image forming method according to claim 10, wherein the image forming operation is an image forming operation during double-sided printing. 12. The image forming method according to claim 10, wherein when the image forming operation is performed again within a predetermined time after the image forming operation is completed, the transfer condition is corrected. An image forming apparatus using the image forming method according to claim 9. The image forming apparatus according to claim 13, wherein the image carrier is an intermediate transfer member, and the transfer member is a secondary transfer member.

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