JP2012150137A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of transfer failure even when rapid deterioration in toner occurs.SOLUTION: An image forming device comprises a density detection part for detecting the density of a developer image transferred to a transfer material by a transfer unit and a correction part for correcting a transfer voltage based on the density detected by the density detection part. The correction part corrects the transfer voltage by a correction value derived based on the ratio between the density of the developer image detected by the density detection part after generating the transfer voltage between an image carrier and the transfer unit to transfer the developer image to the transfer material and the density of the developer image detected by the density detection part after generating the transfer voltage having reverse polarity to the transfer voltage to transfer the developer image to the transfer material.

Description

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

  Conventional image forming apparatuses acquire information corresponding to the number of printed sheets printed at a predetermined time and information corresponding to the number of printed dots printed at a predetermined time in order to prevent transfer failure of toner onto the printing medium. Obtains the print duty from the information corresponding to the obtained number of prints and the information corresponding to the number of print dots, and corrects the transfer voltage applied to the transfer means by predicting the degree of toner deterioration based on the derived print duty. (For example, refer to Patent Document 1).

JP 2010-32950 A (paragraph “0054” to paragraph “0072”, FIGS. 9 and 11)

However, in the above-described conventional technology, although the degree of toner deterioration can be predicted based on the number of printed sheets and the number of printed dots in a predetermined time, friction with a member such as a photosensitive drum or a developing device, etc. If the toner deteriorates rapidly due to the toner, the deterioration cannot be predicted, and a transfer failure occurs.
An object of the present invention is to solve such a problem, and an object of the present invention is to suppress the occurrence of transfer failure even when abrupt toner deterioration occurs.

  Therefore, the present invention generates an image carrier that carries a developer, a transfer device that transfers the developer carried on the image carrier, and a transfer voltage between the image carrier and the transfer device. In the image forming apparatus having the transfer voltage control unit to be controlled, the density detection unit that detects the density of the developer image transferred onto the transfer material by the transfer unit, and the density detection unit based on the density detected by the density detection unit A correction unit that corrects a transfer voltage, and the correction unit generates the transfer voltage between the image carrier and the transfer unit to transfer the developer image onto the transfer material, and detects the density. A density of the developer image detected by a portion, and a transfer voltage having a polarity opposite to the transfer voltage is generated between the image carrier and the transfer device to transfer the developer image to the transfer material, The density of the developer image detected by the density detector And correcting the transfer voltage correction value derived based on.

  According to the present invention as described above, it is possible to suppress the occurrence of transfer failure even when abrupt toner deterioration occurs.

1 is a block diagram showing a control configuration of an image forming apparatus according to a first embodiment. 1 is a schematic side sectional view showing a configuration of an image forming apparatus in a first embodiment. The block diagram which shows the structure of the transfer voltage correction process part in a 1st Example. The block diagram which shows the structure of the memory | storage part in 1st Example. Flowchart showing toner image density measurement processing in the first embodiment Flowchart showing transfer rate calculation processing in the first embodiment The flowchart which shows the correction voltage determination process in a 1st Example. Graph showing the ratio of positively charged toner in the first embodiment Graph showing the transition of the transfer voltage in the first embodiment FIG. 3 is a block diagram illustrating a control configuration of an image forming apparatus according to a second embodiment. The block diagram which shows the structure of the memory | storage part in 2nd Example. The block diagram which shows the structure of the transfer voltage correction process part in 2nd Example. Flowchart showing toner image density measurement processing in the second embodiment. Flowchart showing transfer rate calculation processing in the second embodiment The flowchart which shows the correction voltage determination process in a 2nd Example. Graph showing transfer rate in the second embodiment Graph showing transfer rate in the second embodiment The graph which shows transition of the transfer voltage in 2nd Example

  Embodiments of an image forming apparatus according to the present invention will be described below with reference to the drawings.

FIG. 2 is a schematic sectional side view showing the configuration of the image forming apparatus in the first embodiment.
In FIG. 2, the image forming apparatus 1 is an electronic device that obtains a color image by superimposing and printing toners of four colors of black (K), yellow (Y), magenta (M), and cyan (C). This is a photographic color printer. Note that configurations not directly related to the present invention are omitted for convenience of description.

  The image forming apparatus 1 negatively charges the photosensitive drums 5K, 5Y, 5M, and 5C (hereinafter referred to as “photosensitive drum 5”) and the photosensitive drum 5 as image carriers that carry an electrostatic latent image and a developer image. Charging rollers 2K, 2Y, 2M, and 2C (hereinafter referred to as “charging roller 2”), and exposure units 3K, 3Y, 3M, and 3C (hereinafter referred to as “exposure unit 3”) that write an electrostatic latent image on the photosensitive drum 5. The developing devices 4K, 4Y, 4M, and 4C (hereinafter referred to as “developing device 4”) that visualize the electrostatic latent image on the photosensitive drum 5 with a negatively charged toner that is a developer are respectively black. (K), yellow (Y), magenta (M), and cyan (C) are provided for four colors.

  Transfer rollers 6K, 6Y, 6M, and 6C (hereinafter referred to as “transfer rollers 6”) as transfer devices are disposed in an endless belt-like transfer belt 7 as a transfer material. It is sandwiched and pressed against the photosensitive drum 5. The transfer roller 6 is connected to a transfer power source (not shown), and a voltage is applied from the transfer power source. The transfer power source is a power source capable of outputting a high voltage from the positive electrode to the negative electrode.

  A transfer belt 7 as a transfer material is stretched between a drive roller 8 and an idle roller 9 and supported by tension, and a surface where the photosensitive drum 5 and the transfer belt 7 are in contact with each other is disposed flat. In the vicinity of the transfer belt 7, a density sensor 21 that detects the density of the toner image transferred to the transfer belt 7 and a transfer belt temperature sensor 23 that serves as a transfer material temperature detection unit that detects the temperature of the transfer belt 7 are disposed. Has been. The toner image transferred to the transfer belt 7 is removed by a cleaning blade (not shown) after the density is detected by the density sensor 21.

  The recording medium 17 is placed on a support plate member 18, and the support plate member 18 is pushed up by a spring 19 and pressed against the outer peripheral surface of the hopping roller 14. Further, in the vicinity of the hopping roller 14, a temperature / humidity sensor 22 is disposed as a temperature / humidity detection unit that detects the temperature and humidity in the image forming apparatus 1.

  A broken line in FIG. 2 is a conveyance path of the recording medium 17 fed out by the hopping roller 14, and the first conveyance roller pair 11, the second conveyance roller pair 12, and the writing sensor 15 are arranged along the conveyance path. Has been placed. Further, the fixing device 10, the discharge sensor 16, and the discharge roller pair 13 are disposed downstream of the transfer belt 7 in the medium conveyance direction along the conveyance path.

FIG. 1 is a block diagram showing a control configuration of the image forming apparatus in the first embodiment.
In FIG. 1, the control configuration of the image forming apparatus 1 includes a print control unit 100, an image processing unit 101, a video processing unit 102, a charging voltage control unit 103, a development voltage control unit 104, and a transfer voltage control unit 105. A transfer voltage correction processing unit 106, a transfer rate calculation unit 107, a storage unit 108, and a drum counter 109.

  The print control unit 100 includes a microprocessor, a ROM (Read Only Memory), a RAM (Random Access Memory), an input / output port, a timer, and the like, and is based on a control program (software) stored in the ROM or the like. 1. Control the overall operation. Each sensor such as the writing sensor 15, the discharge sensor 16, the density sensor 21, the temperature / humidity sensor 22, and the transfer belt temperature sensor 23 shown in FIG. The unit 100 judges the analysis, calculation, conditions, etc. based on the input signals and information from each sensor and each unit, and outputs the operation instruction signal to each unit to control the control of each mechanism and the control of the applied voltage. Do.

The image processing unit 101 takes in image data sent from a host computer (not shown) as a host device and converts it into a printable data format. The video processing unit 102 outputs the image data converted by the image processing unit 101 to the exposure device (LED head) 3.
2, the driving devices (not shown) of the hopping roller 14, the first transport roller pair 11, the second transport roller pair 12, the drive roller 8, the photosensitive drum 5, and the fixing device 10 receive signals from the print control unit 100. Upon receipt, it is driven at a predetermined timing and speed.

The charging voltage control unit 103, the development voltage control unit 104, and the transfer voltage control unit 105 receive control values from the print control unit 100 and control voltages applied to the charging roller 2, the developing device 4, and the transfer roller 6, respectively. Do.
The transfer voltage controller 105 is formed on the surface of the photosensitive drum 5 by applying a predetermined transfer voltage to the transfer roller 6 by a transfer power source (not shown) to generate a transfer voltage between the photosensitive drum 5 and the transfer roller 6. The toner image is transferred to the recording medium 17 and the transfer belt 7.

  The transfer voltage correction processing unit 106 serving as a correction unit detects the state of toner deteriorated from the density detected by the density sensor 21 serving as a density detection unit, and the state of the deteriorated toner is detected by the temperature / humidity sensor 22. The transfer voltage correction value is determined based on the temperature and humidity of the toner and the temperature of the transfer belt 7 detected by the transfer belt temperature sensor 23, and the transfer voltage is corrected.

  The storage unit 108 detects, as a density value, a value detected by the density sensor 21 serving as a density detection unit that detects the density of the toner image transferred to the transfer belt 7 serving as a transfer material in order to detect a deteriorated toner state. Remember.

The transfer rate calculation unit 107 obtains the transfer rate from the density value stored in the storage unit 108.
As shown in FIG. 3, the transfer voltage correction processing unit 106 stores a transfer voltage correction table for storing a transfer voltage correction table for determining a correction value of the transfer voltage from the transfer rate obtained by the transfer rate calculating unit 107. 1061 is provided.

  The drum counter 109 is a counter that counts and stores the number of rotations of the photosensitive drum 5 every time the photosensitive drum 5 rotates once. When the counted rotation number of the photosensitive drum 5 exceeds a predetermined value, the drum counter 109 notifies the print control unit 100 to that effect. Receiving the notification that the rotational speed of the photosensitive drum 5 has exceeded the predetermined value, the print control unit 100 corrects the transfer voltage by the transfer voltage correction processing unit 106.

The configuration of the transfer voltage correction processing unit 106 will be described with reference to FIG. 1 based on the block diagram showing the configuration of the transfer voltage correction processing unit in the first embodiment of FIG.
In FIG. 3, the transfer voltage correction processing unit 106 includes a transfer voltage correction table storage unit 1061, a value representing a transfer rate derived from the measured value of the density sensor 21, a measured value of the temperature / humidity sensor 22, and a transfer From the measured value of the belt temperature sensor 23, a correction value of the transfer voltage is determined. The density sensor 21 measures the density of the toner image transferred to the transfer belt 7 shown in FIG. 2 from two transfer voltage conditions. The measurement result is stored in the storage unit 108 by the print control unit 100.

The measurement result of the density sensor 21 stored in the storage unit 108 will be described with reference to FIG. 1 based on the block diagram showing the configuration of the storage unit in the first embodiment of FIG.
In FIG. 4, the storage unit 108 uses the detected values of the density of the toner image transferred to the transfer belt 7 shown in FIG. 2 based on two transfer voltage conditions as a first detected value 1081 and a second detected value 1082. It has a memory area. The transfer rate calculation unit 107 derives the transfer rate from the detection values stored in the first detection value 1081 and the second detection value 1082.

The operation of the above configuration will be described.
First, the operation of the image forming apparatus will be described with reference to FIGS.
The print control unit 100 of the image forming apparatus 1 generates image data instructed for printing, transport control of the recording medium 17, in accordance with a print instruction received from a host device such as a personal computer connected to the image forming apparatus 1, for example. The charging control of the photosensitive drum 5 by the charging roller 2, the exposure control by the exposure device 3, the development control by the developing device 4, the transfer control by the transfer roller 6, and the fixing control by the fixing device 10 are performed, and an image is printed on the recording medium 17. .

More specifically, when receiving a print instruction from a host device such as a personal computer connected to the image forming apparatus 1, the print control unit 100 starts control of the fixing device 10 and heats the fixing device 10 to a usable temperature. Control.
When the fixing device 10 reaches a usable temperature, the print control unit 100 controls a driving device (not shown) to rotate the photosensitive drum 5 so that the linear speed of the photosensitive drum 5 becomes the transport speed of the storage medium 17 during printing. Accelerate to.

  At the same time, the printing control unit 100 controls a driving device (not shown) to start the rotation of the drive roller 8, and rotates the transfer belt 7 by the rotation of the drive roller 8. The linear velocity of the transfer belt 7 is recorded during printing. Accelerate until the conveyance speed of the medium 17 is reached.

In response to an instruction from the printing control unit 100, the charging voltage control unit 103 controls the charging roller 2 at a timing when the photosensitive drum 5 starts to rotate, and applies a negative voltage to the photosensitive drum 5, so that the outer peripheral surface of the photosensitive drum 5 is applied. For example, it is charged to minus 600V. (Charge control)
In response to an instruction from the printing control unit 100, the development voltage control unit 104 becomes ready to develop the developer at a timing when the photosensitive drum 5 portion charged to −600 V passes through the development area of the developer due to the rotation of the photosensitive drum 5. To control. For example, in the case of the contact development method using a developing roller, the developing can be performed by applying a voltage of −200 V to the developing roller to which the negatively charged toner is attached.

  When the portion of the photosensitive drum 5 charged to −600 V reaches the transfer nip portion as the contact portion with the transfer roller 6 via the transfer belt 7 by the rotation of the photosensitive drum 5, the printing process is in a printable state. Become.

Next, the printing control unit 100 rotates the hopping roller 14 by a driving device (not shown), and separates and conveys the recording medium 17 one by one. The separated recording medium 17 is transported to the second transport roller pair 12 via the first transport roller pair 11 by the print control unit 100 controlling a driving device (not shown), and is transferred to the second transport roller pair 12 and the transfer. The leading edge is detected by the writing sensor 15 disposed between the belt 7 and the belt 7. The writing sensor 15 that has detected the leading edge of the recording medium 17 notifies the print controller 100 of the position of the writing sensor 15 as a signal indicating the timing at which the leading edge of the recording medium 17 passes. (Conveyance control of recording medium 17)
The print control unit 100 separates the image to be printed on the recording medium 17 into the respective colors of black, yellow, magenta, and cyan by the video processing unit 102 based on the print instruction signal received from the host device, and further exposes the exposure unit ( The LED head 3 converts the image data into writable image data (image data generation processing).

The recording medium 17 is transported onto the transfer belt 7 after passing through the writing sensor 15.
In response to an instruction from the print control unit 100, the video processing unit 102 detects when the writing sensor 15 detects the leading edge of the recording medium 17, the distance between the writing sensor 15 and the transfer nip portion of each color, and the exposure on the photosensitive drum 5. The exposure unit (LED head) 3 is controlled and electrostatically controlled at a timing at which an image to be printed is transferred to a desired position on the recording medium 17 according to the distance from the portion to the transfer nip and the conveyance speed of the recording medium 17. The latent image is written on the photosensitive drum 5.

  The exposure device (LED head) 3 is a photosensitive drum charged to −600 V by irradiating a spot light of, for example, 600 dpi (dots per inch) pitch to a portion of the surface of the photosensitive drum 5 where a toner image is to be obtained. 5 is set to a potential of about −50 V, and an electrostatic latent image is formed on the surface of the photosensitive drum 5 (exposure control).

  The surface of the photosensitive drum 5 on which the electrostatic latent image is formed by the exposure device (LED head) 3 is moved to the position of the developing device 4 by the rotation operation, and the photosensitive drum 5 is exposed to a small absolute value of the surface potential. The toner image, which is a negatively charged developer carried by the developing device 4, adheres to the surface portion by the Coulomb force, whereby a visible toner image is developed (development control). The surface of the photosensitive drum 5 to which the developed toner image adheres is conveyed to the transfer nip portion by a rotating operation.

  Under the control of the transfer voltage control unit 105 according to an instruction from the print control unit 100, a transfer voltage (for example, +1500 V to +1500 V) is used as a reference transfer voltage for printing while the recording medium 17 is present on the transfer roller 6. + 3000V), a positive voltage having a polarity opposite to that of the toner is applied.

  The toner on the photosensitive drum 5 receives a Coulomb force by a positive voltage applied to the transfer roller 6 at the transfer nip portion, and is transferred onto the recording medium 17 (or the transfer belt 7) (transfer control).

The operation described above is sequentially performed for each color of black, yellow, magenta, and cyan, and the recording medium 17 on which the toner of each color is developed and transferred is conveyed to the fixing device 10.
The recording medium 17 conveyed to the fixing device 10 melts the toner transferred onto the recording medium 17 by the heat and pressure of the fixing device 10 under the control of the print control unit 100 and fixes the toner onto the recording medium 17 (fixing control). ).

  The recording medium 17 that has passed through the fixing device 10 is detected at the rear end by the carry-out sensor 16 and is discharged out of the image forming apparatus 1 by the discharge roller 13. When the recording medium 17 is discharged, the print control unit 100 stops the rotation operation of each roller, the operation of the charging roller 2, the developing roller, and a transfer power source (not shown), and ends the printing operation.

  In the printing operation described above, printing with a small amount of toner consumption per recording medium (for example, the ratio of the number of dots contributing to printing out of the total number of dots is 5%) is large in a predetermined period (for example, one day). When the printing is performed on the number of print media 17 (for example, 2500), the damage received by the toner becomes large, and deteriorated toner is generated. In addition, toner deteriorated due to variations in members may be generated.

Such deteriorated toner is liable to cause transfer failure due to electric discharge. Conventionally, when a large number of printing operations are performed, the consumption of toner is calculated from the number of printing dots and the number of rotations of the photosensitive drum 5, and an environmental sensor is used. As a result, the transfer voltage is corrected under the condition that the deteriorated toner is most likely to be generated.
However, abrupt generation of deteriorated toner due to variations in the quality of the developing device 4 and the photosensitive drum 5 and dimensional variations in the mechanism has not been considered.

  Therefore, in this embodiment, the state of the deteriorated toner is detected, and a correction value for the transfer voltage is determined based on a numerical value representing the detected state.

  As a method of correcting the transfer voltage, a method of correcting the transfer voltage from a menu displayed on the operation unit of the image forming apparatus 1 and the number of rotations of the photosensitive drum 5 after the power of the image forming apparatus 1 is turned on. Several methods such as a method of correcting a transfer voltage when a predetermined value is exceeded are conceivable. In this embodiment, the rotational speed of the photosensitive drum 5 after the power of the image forming apparatus 1 is turned on is considered. A method for automatically correcting the transfer voltage when a predetermined value (for example, 500 times) is exceeded will be described.

  Further, in this embodiment, in order to detect the deterioration state of the toner, the transfer condition is measured as a transfer rate value when a transfer electric field opposite to the normal one is generated. At this time, the toner to be transferred is a positively charged toner having a reverse polarity to that of the normal toner. An increase in the deteriorated toner can be detected by increasing the positively charged toner. When the deteriorated toner increases, the deteriorated toner is discharged at a normal transfer voltage, and a transfer defect is generated. Therefore, in this embodiment, the transfer rate of positively charged toner that is positively charged is derived, and the deterioration state of the toner is detected.

  Here, the reason why the transfer rate of the positively charged toner is derived is to know the ratio of the positively charged toner to the whole toner. This is because if the total amount of toner increases, the amount of positively charged toner increases, and if the total amount of toner decreases, the amount of positively charged toner also decreases. This is because it is impossible to correctly grasp the deterioration state.

First, the toner image density measurement process will be described with reference to FIG. 1 in accordance with a step indicated by S in the flowchart showing the toner image density measurement process in the first embodiment of FIG.
S1: The print control unit 100 in a standby state in which a printing operation is not performed according to a print instruction or the like from the host device, the toner image of a solid image having a print density of 100% on the photosensitive drum so that the toner adheres to all the print dots. Form. The reason why a solid toner image having a printing density of 100% is formed on the photosensitive drum in this way is to measure the transfer rate with high accuracy because only a few percent of all the positively charged toner is present.

  S2: The printing control unit 100 and the transfer voltage control unit 105 rotate (transfer) the photosensitive drum by a predetermined amount, and transfer (print) the toner image formed on the photosensitive drum onto the transfer belt with a reference plus transfer voltage. Originally, the transfer rate can be accurately measured by measuring the toner image before transfer in terms of density and weight. However, it is necessary to arrange a sensor or the like in the vicinity of the photosensitive drum in order to measure the toner image before transfer by density or weight, which increases the manufacturing cost of the apparatus. Therefore, in this embodiment, the density of the toner image transferred to the transfer belt is measured with a reference transfer voltage having the highest transfer rate. This is because a value approximate to the measurement of the density of the toner image before being transferred to the transfer belt can be obtained.

S3: The printing control unit 100 and the transfer voltage control unit 105 further rotate the photosensitive drum by a predetermined amount to transfer the positively charged toner out of the toner image formed on the photosensitive drum with a polarity opposite to the reference positive transfer voltage. Transfer (print) to the transfer belt with a negative transfer voltage (for example, −1000 V).
S4: The print control unit 100 measures the density of the toner image on the transfer belt transferred with the reference plus transfer voltage by the density sensor 21.

S5: The print control unit 100 stores the density value measured by the density sensor 21 as the first detection value in the first detection value 1081 of the storage unit 108 shown in FIG. Accordingly, the first detection value 1081 stores the density value of the toner image on the transfer belt transferred at the reference plus transfer voltage.
S6: The print control unit 100 measures the density of the toner image on the transfer belt transferred with the negative transfer voltage by the density sensor 21.

S7: The print control unit 100 stores the density value measured by the density sensor 21 as the second detection value in the second detection value 1082 of the storage unit 108 shown in FIG. Therefore, the second detection value 1082 stores the density value of the toner image on the transfer belt transferred with the minus transfer voltage.
In this way, the density values of the toner image transferred (printed) on the transfer belt under two different transfer voltage conditions are obtained by performing the processing of S1 to S7. Then, the process proceeds to S8 in FIG. 6, and the transfer rate of the positively charged toner is derived from the two acquired density values.

Next, the transfer rate calculation process will be described with reference to FIG. 1 according to the step represented by S in the flowchart of the transfer rate calculation process in the first embodiment of FIG.
S8: In response to an instruction from the print control unit 100, the transfer rate calculation unit 107 performs positive charging from the density value stored in the first detection value 1081 and the density value stored in the second detection value 1082 shown in FIG. The toner transfer rate (ratio) Te is derived. This transfer rate Te is obtained by the following calculation formula.

Transfer rate Te = (1−density value transferred with reverse polarity transfer voltage (density value stored in second detection value 1082)) / (density value transferred with reference transfer voltage (first detection value) Concentration value stored in 1081))
The transfer rate calculation unit 107 derives the transfer rate Te from the above formula. Then, the process proceeds to S9 in FIG.

Next, the correction voltage determination process will be described with reference to FIG. 1 according to the step represented by S in the flowchart showing the correction voltage determination process in the first embodiment of FIG.
The transfer voltage correction processing unit 106 determines the correction value of the transfer voltage from the derived transfer rate Te of the positively charged toner and the measured values of the temperature / humidity sensor 22 and the transfer belt temperature sensor 23 in response to an instruction from the print control unit 100. .

S9: First, the transfer voltage correction processing unit 106 reads the temperature and humidity values detected by the temperature / humidity sensor 22.
S10: The transfer voltage correction processing unit 106 reads the value of the transfer belt temperature detected by the transfer belt temperature sensor 23.

  S11: The transfer voltage correction processing unit 106 calculates a correction value of the transfer voltage from the transfer rate Te of the positively charged toner calculated in S8 of FIG. 6 and the measured values of the temperature / humidity sensor 22 and the transfer belt temperature sensor 23. decide. In order to make this determination, the transfer voltage correction values shown in Table 1 are stored in advance in the storage unit 1061 (FIG. 3) of the transfer voltage correction table. Incidentally, the deteriorated toner that is liable to cause a transfer failure is generated when the adhesion force of the toner increases due to the high temperature and humidity and the temperature in the apparatus increases.

Table 1 shows the transfer voltage correction based on the relationship between the transfer rate value Te of the positively charged toner, the temperature T as the measurement value of the transfer belt temperature sensor 23, and the temperature Tm and the humidity He as the measurement values of the temperature / humidity sensor 22. The transfer correction voltage (V) as a value is determined. The transfer voltage correction value is a value determined based on the result obtained through experiments.
The transfer voltage correction processing unit 106 corrects the transfer voltage by adding the obtained transfer voltage correction value and the reference transfer voltage, and the print control unit 100 performs printing that does not cause a transfer failure with the corrected transfer voltage. Perform the action.

  As described above, the transfer voltage correction processing unit 106 generates a reference transfer voltage between the photosensitive drum as the image carrier and the transfer roller as the transfer device according to an instruction from the print control unit 100, and serves as a transfer material. A toner image is transferred to the transfer belt, and a transfer voltage having a polarity opposite to the reference transfer voltage is generated between the density of the toner image detected by the density sensor 21 and the photosensitive drum and the transfer roller. The toner image is transferred, and the transfer voltage is corrected with a correction value derived based on the ratio with the density of the toner image detected by the density sensor 21.

Although the above-described processing of S1 to S11 has been described as being performed for one color toner, the same processing is performed for other color toners, and is performed for all color toners.
Next, a description will be given of an experimental result in which a printing result by a conventional image forming apparatus (printer) is compared with a printing result by the image forming apparatus in which the transfer voltage is corrected according to this embodiment.

  The positively charged deteriorated toner increases when continuous printing is performed in an environment of a temperature of 28 degrees and a humidity of 80%. Here, the continuous printing means that a large number of sheets (for example, 2500 sheets) are printed per day, and the amount of toner consumption per recording medium is small (for example, the number of dots contributing to printing out of the total number of dots) The ratio is 5%). As shown in FIG. 8, the positively charged toner increases as the rotational speed (drum count) of the photosensitive drum increases. The positively charged toner may be easily generated in a state of a member of the photosensitive drum or the developing device.

  Table 2 shows experimental results comparing the printing result obtained by the conventional image forming apparatus (printer) with the printing result obtained by the image forming apparatus in which the transfer voltage is corrected according to this embodiment. In Table 2, “◯” indicates good transfer, “Δ” indicates some transfer failure, and “x” indicates transfer failure.

  A conventional image forming apparatus (printer) performs transfer voltage correction control that lowers the transfer voltage when the drum count, which is the rotational speed of the photosensitive drum, increases. However, a transfer failure occurs at 2000 drum counts. This is transfer voltage correction control that predicts toner deterioration and lowers the transfer voltage. Therefore, when deteriorated toner is suddenly generated depending on the state of the photosensitive drum or the developing device, the transfer voltage is not sufficiently corrected, and transfer failure is caused. It has occurred.

  However, the transfer voltage correction control of this embodiment, that is, the transfer voltage correction control for determining the correction value of the transfer voltage from the transfer rate of the positively charged toner and the measured values of the temperature / humidity sensor 22 and the transfer belt temperature sensor 23 is applied. In the image forming apparatus, the transfer was good up to a drum count of 1000, and even if the drum count was 3000, a slight transfer failure was observed, and no transfer failure occurred.

  When the drum count is 2000, as shown in FIG. 8, the proportion of the positively charged toner is 9%, and the amount of deteriorated toner is increased. In this embodiment, for example, as shown in FIG. 9, when the reference transfer voltage is 3000 V, the transfer voltage correction value is −400 V when the drum count is 2000, which is 200 V lower than the conventional correction value. In this case, transfer failure does not occur.

  As described above, in this embodiment, the state of occurrence of the deteriorated toner is quantitatively detected as the transfer rate of the positively charged toner, and the transfer voltage is determined from the transfer rate of the positively charged toner. The occurrence of transfer failure can be suppressed following the toner generation state.

  In addition, since the conditions under which transfer defects are likely to occur vary depending on the installation environment of the image forming apparatus and the temperature rise inside the image forming apparatus, a temperature / humidity sensor and a temperature sensor for the transfer belt are provided. By correcting the transfer voltage based on the temperature and humidity values detected by the temperature sensor, it becomes possible to perform transfer voltage correction with good followability, and to suppress transfer defects.

As described above, in the first embodiment, the transfer voltage is determined based on the transfer rate of the positively charged toner, thereby suppressing the occurrence of transfer failure following the quantitatively detected state of the deteriorated toner. The effect of being able to be obtained.
Further, by determining the transfer voltage based on the temperature of the temperature and humidity sensor and the transfer belt in addition to the transfer rate of the positively charged toner, it becomes possible to perform a transfer voltage correction with a better follow-up property, thereby preventing a transfer failure. The effect that generation | occurrence | production can be suppressed is acquired.

The configuration of the second embodiment is an area in which the temperature sensor of the transfer belt provided in the configuration of the first embodiment is removed from the configuration of the first embodiment, and the third detection value is stored in the storage unit. It is supposed to be equipped with.
FIG. 10 is a block diagram showing the control configuration of the image forming apparatus in the second embodiment, FIG. 11 is a block diagram showing the configuration of the storage unit in the second embodiment, and FIG. 12 is a transfer voltage correction in the second embodiment. It is a block diagram which shows the structure of a process part. Note that parts similar to those of the first embodiment described above are denoted by the same reference numerals and description thereof is omitted.

In FIG. 10, the transfer belt temperature sensor provided in the configuration of the first embodiment is removed.
The transfer voltage correction processing unit 106 detects the deteriorated toner state by the density sensor 21 and corrects the transfer voltage in accordance with the deteriorated toner state and the temperature and humidity in the apparatus detected by the temperature / humidity sensor 22. Determine the value. Other configurations are the same as those of the first embodiment shown in FIG.

  11, in addition to the first detection value 1081 and the second detection value 1082, the storage unit 108 detects the density of the toner image transferred to the transfer belt shown in FIG. 2 at a transfer voltage lower than the reference transfer voltage. A third detection value 1083 is provided as an area for storing values. The transfer rate calculation unit 107 derives the transfer rate from the detection values stored in the first detection value 1081, the second detection value 1082, and the third detection value 1083.

  As the toner deteriorates, the proportion of the reversely charged toner (positively charged toner in this embodiment) charged to a polarity opposite to the normal polarity increases, so the average charge amount of the toner decreases. As a result, the potential difference between the transfer voltage and the charged toner gradually decreases, so that the toner adhering to the surface of the photosensitive drum 5 does not easily move to the transfer belt 7. This corresponds to the fact that the force that the toner adheres to the photosensitive drum 5 is greater than the force that is attracted to the transfer belt 7 side by the transfer electric field. That is, under a constant transfer voltage, as the toner deteriorates, the amount of toner transferred to the transfer belt 7 decreases and the density of the toner image decreases.

  Here, by using a transfer voltage lower than the reference transfer voltage, the potential difference between the transfer voltage and the charged toner is further reduced, and the toner image density reduction is further remarkable. It is possible to accurately detect the degree of adhesion with the photosensitive drum.

12, the transfer voltage correction processing unit 106 includes a storage unit 1062 for a deteriorated toner state value Q1 calculation table and a storage unit 1063 for a deteriorated toner state value Q2 calculation table in addition to a storage unit 1061 for a transfer voltage correction table. .
In the storage unit 1062 of the deteriorated toner state value Q1 calculation table, in order to derive the deteriorated toner state value Q1 from the transfer rate obtained when the transfer is performed with a transfer voltage having a polarity opposite to the reference transfer voltage, Table 3 The deteriorated toner state value Q1 calculation table shown in FIG.

また、劣化トナー状態値Ｑ２算出テーブルの記憶部１０６３には、基準の転写電圧より低い転写電圧で転写したときに得られた転写率から劣化トナーの状態値Ｑ２を導出するために、表４に示す劣化トナー状態値Ｑ２算出テーブルが記憶される。

Further, in the storage unit 1063 of the deteriorated toner state value Q2 calculation table, in order to derive the deteriorated toner state value Q2 from the transfer rate obtained when the transfer is performed at a transfer voltage lower than the reference transfer voltage, Table 4 is used. A deteriorated toner state value Q2 calculation table is stored.

  Further, the storage unit 1061 of the transfer voltage correction table includes the deteriorated toner state value Q3 derived from the deteriorated toner state value Q1 and the deteriorated toner state value Q2, and the measured values of the temperature and humidity sensor 22 shown in FIG. A transfer voltage correction table shown in Table 5 for determining a transfer voltage correction value is stored.

  The transfer voltage correction processing unit 106 derives the state value Q1 of the deteriorated toner from the transfer rate obtained when the transfer is performed with a transfer voltage having a reverse polarity to the reference transfer voltage, and the transfer voltage is corrected with a transfer voltage lower than the reference transfer voltage. The state value Q2 of the deteriorated toner is derived from the transfer rate obtained at the time, the state value Q3 of the deteriorated toner derived from the state value Q1 of the deteriorated toner and the state value Q2 of the deteriorated toner, and the temperature and humidity shown in FIG. The correction value of the transfer voltage is determined from the temperature Tm and the humidity He as measured values of the sensor 22.

The operation of the above configuration will be described. Since the printing operation of the image forming apparatus is the same as that of the first embodiment, the description thereof is omitted.
As a method of correcting the transfer voltage, a method of correcting the transfer voltage from a menu displayed on the operation unit of the image forming apparatus 1 and the number of rotations of the photosensitive drum 5 after the power of the image forming apparatus 1 is turned on. Several methods such as a method of correcting a transfer voltage when a predetermined value is exceeded are conceivable. In this embodiment, the rotational speed of the photosensitive drum 5 after the power of the image forming apparatus 1 is turned on is considered. A method for automatically correcting the transfer voltage when a predetermined value (for example, 500 times) is exceeded will be described.

First, the toner image density measurement process will be described with reference to FIG. 10 according to the step indicated by S in the flowchart of the toner image density measurement process in the second embodiment of FIG.
S101-S103: Since it is the same process as S1-S3 in FIG. 5, description is abbreviate | omitted.

S104: The printing control unit 100 and the transfer voltage control unit 105 further rotate the photosensitive drum by a predetermined amount to transfer the positively charged toner in the toner image formed on the photosensitive drum to a transfer voltage lower than the reference transfer voltage (for example, 1000V) to transfer (print) to the transfer belt.
S105 to S108: The processing is the same as S4 to S7 in FIG.

S109: The print control unit 100 measures the density of the toner image on the transfer belt transferred at a transfer voltage lower than the reference transfer voltage by the density sensor 21.
S110: The print control unit 100 stores the density value measured by the density sensor 21 as the third detection value in the third detection value 1083 of the storage unit 108 shown in FIG. Therefore, the third detection value 1083 stores the density value of the toner image on the transfer belt transferred at a transfer voltage lower than the reference transfer voltage.

  Here, since the average charge amount of the normal toner is lowered, when the toner is transferred at a transfer voltage lower than the reference transfer voltage, the density value of the transferred toner becomes a high value. However, when the deteriorated toner is increased, the density value of the transferred toner becomes a low value when the transfer is performed at a transfer voltage lower than the reference transfer voltage even though the average charge amount of the toner is decreased. This is presumably because the adhesion between the deteriorated toner and the photosensitive drum increases.

As described above, the density values of the toner image transferred (printed) on the transfer belt under three different transfer voltage conditions are obtained by performing the processing of S101 to S110. Then, the process proceeds to S111 in FIG. 14, and the transfer rate of the positively charged toner is derived from the obtained three density values.
Next, the transfer rate calculation process will be described with reference to FIG. 10 according to the step indicated by S in the flowchart showing the transfer rate calculation process in the second embodiment of FIG.

  S111: In response to an instruction from the print control unit 100, the transfer rate calculation unit 107 performs positive charging from the density value stored in the first detection value 1081 and the density value stored in the second detection value 1082 shown in FIG. The toner transfer rate (first ratio) Te1 is derived. This transfer rate Te1 is obtained by the following calculation formula.

Transfer rate Te1 = (1−density value transferred with transfer voltage of reverse polarity (density value stored in second detection value 1082)) / (density value transferred with reference transfer voltage (first detection value) Concentration value stored in 1081))
S112: In response to an instruction from the print control unit 100, the transfer rate calculation unit 107 uses the density value stored in the first detection value 1081 and the density value stored in the third detection value 1083 shown in FIG. A transfer rate (second ratio) Te2 at a transfer voltage lower than the transfer voltage is derived. This transfer rate Te2 is obtained by the following calculation formula.

Transfer rate Te2 = (1−density value transferred with transfer voltage lower than reference transfer voltage (density value stored in third detection value 1083)) / (density value transferred with reference transfer voltage (first Concentration value stored in the detected value 1081)))
The transfer rate calculation unit 107 derives the transfer rate Te1 and the transfer rate Te2 from the above formula. Then, the process proceeds to S113 in FIG.

Next, the correction voltage determination process will be described with reference to FIG. 10 in accordance with the step represented by S in the flowchart showing the correction voltage determination process in the second embodiment of FIG.
In response to an instruction from the print control unit 100, the transfer voltage correction processing unit 106 determines the transfer voltage based on the transfer rate Te1 of the positively charged toner, the transfer rate Te2 at a transfer voltage lower than the reference transfer voltage, and the measured value of the temperature / humidity sensor 22. Determine the correction value.

  S113: First, the transfer voltage correction processing unit 106 derives the state value Q1 of the deteriorated toner from the transfer rate Te1 of the positively charged toner. The deteriorated toner state value Q1 is stored in the storage unit 1062 of the deteriorated toner state value Q1 calculation table in association with the transfer rate Te1 as the deteriorated toner state value Q1 calculation table shown in Table 3. The processing unit 106 searches the deteriorated toner state value Q1 calculation table based on the transfer rate Te1 to derive the deteriorated toner state value Q1.

  S114: The transfer voltage correction processing unit 106 derives the state value Q2 of the deteriorated toner from the transfer rate Te2 at a transfer voltage lower than the reference transfer voltage. The state value Q2 of the deteriorated toner is stored in the storage unit 1063 of the deteriorated toner state value Q2 calculation table in association with the transfer rate Te2 as the deteriorated toner state value Q2 calculation table shown in Table 4. The processing unit 106 searches the deteriorated toner state value Q2 calculation table based on the transfer rate Te2 to derive the deteriorated toner state value Q2.

S115: The transfer voltage correction processing unit 106 derives the deteriorated toner state value Q3 from the deteriorated toner state value Q1 and the deteriorated toner state value Q2. The state value Q3 of the deteriorated toner is derived based on the following calculation formula.
State value Q3 of deteriorated toner = State value Q1 of deteriorated toner + State value Q2 of deteriorated toner
S116: The transfer voltage correction processing unit 106 reads the temperature and humidity values detected by the temperature / humidity sensor 22.

S117: The transfer voltage correction processing unit 106 determines a correction value for the transfer voltage from the derived deteriorated toner state value Q3 and the temperature T and humidity He detected by the temperature / humidity sensor 22.
In order to make this determination, the transfer voltage correction values shown in Table 5 described above are stored in advance in the storage unit 1061 (FIG. 12) of the transfer voltage correction table. The transfer voltage correction value in the transfer voltage correction table is a value determined based on a result obtained through experiments.

The transfer voltage correction processing unit 106 corrects the transfer voltage by adding the obtained transfer voltage correction value and the reference transfer voltage, and the print control unit 100 performs a printing operation in which a transfer failure does not occur with the corrected transfer voltage. I do.
As described above, the transfer voltage correction processing unit 106 corrects the transfer voltage with the correction value derived based on the transfer rate (first ratio) Te1 and the transfer rate (second ratio) Te2.

Although the above-described processing of S101 to S117 has been described as being performed for one color toner, the same processing is performed for other color toners, and is performed for all color toners.
Next, a description will be given of an experimental result in which a printing result by a conventional image forming apparatus (printer) is compared with a printing result by the image forming apparatus in which the transfer voltage is corrected according to this embodiment.

  The positively charged deteriorated toner increases when continuous printing is performed in an environment of a temperature of 28 degrees and a humidity of 80%. The positively charged toner transfer rate Te1 increases as the rotational speed (drum count) of the photosensitive drum increases as shown in FIG. In addition, the transfer rate Te2 of the deteriorated toner at a transfer voltage lower than the reference transfer voltage decreases as the rotational speed (drum count) of the photosensitive drum increases as shown in FIG.

  Table 6 shows experimental results comparing the printing result obtained by the conventional image forming apparatus (printer) with the printing result obtained by the image forming apparatus in which the transfer voltage is corrected according to this embodiment. In Table 6, “◯” indicates good transfer, “Δ” indicates some transfer failure, and “x” indicates transfer failure.

  A conventional image forming apparatus (printer) performs transfer voltage correction control that lowers the transfer voltage when the drum count, which is the rotational speed of the photosensitive drum, increases. However, a transfer failure occurs at 2000 drum counts. This is transfer voltage correction control that predicts toner deterioration and lowers the transfer voltage. Therefore, when deteriorated toner is suddenly generated depending on the state of the photosensitive drum or the developing device, the transfer voltage is not sufficiently corrected, and transfer failure is caused. It has occurred.

  However, the transfer voltage correction control of this embodiment, that is, the transfer rate of the positively charged toner, the transfer rate of the deteriorated toner at a transfer voltage lower than the reference transfer voltage, and the measured value of the temperature / humidity sensor 22 are used to correct the transfer voltage. In the image forming apparatus to which the transfer voltage correction control for determining the value is applied, the transfer is good until the drum count is 1000, and even if the drum count is 3000, there is a slight transfer failure, and the transfer failure occurs. I never did.

  When the drum count is 2000, the transfer rate Te1 is 6% as shown in FIG. 16, and the state value Q1 of the deteriorated toner is “2” from Table 3. When the drum count is 2000, the transfer rate Te2 is 15% as shown in FIG. 17, and the state value Q2 of the deteriorated toner is “3” from Table 4.

  In this embodiment, for example, as shown in FIG. 18, when the reference transfer voltage is 3000 V, the transfer voltage correction value is −300 V when the drum count is 2000, and the voltage is 100 V lower than the conventional correction value. In this case, transfer failure does not occur.

In the first embodiment, the state of the deteriorated toner is detected from the transfer rate of the positively charged toner (the ratio of the positively charged toner), and the transfer voltage is corrected. The toner transfer rate alone was insufficient.
Therefore, in this embodiment, in addition to the transfer rate of the positively charged toner, the state of the deteriorated toner is accurately detected by considering the adhesion force between the toner and the photosensitive drum due to the transfer rate of the transfer voltage lower than the reference transfer voltage. can do.

As described above, the transfer voltage is corrected based on the transfer rate of the positively charged toner and the adhesion force between the toner and the photosensitive drum due to the transfer rate of the transfer voltage lower than the reference transfer voltage, thereby suppressing the occurrence of transfer failure. Can do.
As described above, in the second embodiment, the transfer voltage is determined from the transfer rate of the positively charged toner and the transfer rate of the transfer voltage lower than the reference transfer voltage, so that the detection is performed with high accuracy and quantitatively. The effect of suppressing the occurrence of transfer failure by following the state of occurrence of the deteriorated toner can be obtained.

  In addition to the transfer rate of positively charged toner and the transfer rate of transfer voltage lower than the reference transfer voltage, the transfer voltage is determined based on the temperature of the temperature / humidity sensor and the transfer belt, so that transfer with better followability is possible. Voltage correction can be performed, and the effect of suppressing the occurrence of transfer defects can be obtained.

  In the first and second embodiments, the image forming apparatus has been described as a direct transfer type printer. However, the present invention is not limited to this, and an intermediate transfer type printer using an intermediate transfer belt or the like, an electrophotography, or the like. A facsimile machine, a copying machine, a multi-function machine, or the like may be used.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Charging roller 3 Exposure device (LED head)
DESCRIPTION OF SYMBOLS 4 Developing device 5 Photosensitive drum 6 Transfer roller 7 Transfer belt 8 Drive roller 9 Idle roller 10 Fixing device 11 First conveyance roller pair 12 Second conveyance roller pair 13 Discharge roller pair 14 Hopping roller 21 Concentration sensor 22 Temperature / humidity sensor 23 Transfer belt Temperature sensor 100 Print control unit 101 Image processing unit 102 Video processing unit 103 Charging voltage control unit 104 Development voltage control unit 105 Transfer voltage control unit 106 Transfer voltage correction processing unit 107 Transfer rate calculation unit 108 Storage unit 109 Drum counter

Claims (4)

An image carrier that carries the developer, a transfer device that transfers the developer carried on the image carrier, and a transfer voltage controller that generates a transfer voltage between the image carrier and the transfer device; In an image forming apparatus having
A density detector that detects the density of the developer image transferred to the transfer material by the transfer device;
A correction unit that corrects the transfer voltage based on the density detected by the density detection unit,
The correction unit is
A density of the developer image detected by the density detection unit, wherein the transfer voltage is generated between the image carrier and the transfer unit to transfer the developer image to the transfer material;
A density of the developer image detected by the density detection unit is generated between the image carrier and the transfer device by generating a transfer voltage having a polarity opposite to the transfer voltage to transfer the developer image to the transfer material. An image forming apparatus, wherein the transfer voltage is corrected with a correction value derived based on a ratio of The image forming apparatus according to claim 1.
A temperature / humidity detector that detects the temperature and humidity inside the device
The image forming apparatus, wherein the correction unit corrects the transfer voltage with a correction value derived based on the temperature and humidity detected by the temperature and humidity detection unit and the ratio. The image forming apparatus according to claim 2.
A transfer material temperature detector for detecting the temperature of the transfer material;
The correction unit corrects the transfer voltage with a correction value derived based on the temperature detected by the transfer material temperature detection unit, the temperature and humidity detected by the temperature / humidity detection unit, and the ratio. Forming equipment. The image forming apparatus according to claim 1 or 2,
The correction unit is
A density of the developer image detected by the density detection unit, wherein the transfer voltage is generated between the image carrier and the transfer unit to transfer the developer image to the transfer material;
A density of the developer image detected by the density detection unit is generated between the image carrier and the transfer device by generating a transfer voltage having a polarity opposite to the transfer voltage to transfer the developer image to the transfer material. And the first ratio,
A density of the developer image detected by the density detection unit, wherein the transfer voltage is generated between the image carrier and the transfer unit to transfer the developer image to the transfer material;
A transfer voltage lower than the transfer voltage is generated between the image carrier and the transfer device to transfer the developer image to the transfer material, and the density of the developer image detected by the density detection unit Let the ratio be the second ratio,
An image forming apparatus, wherein the transfer voltage is corrected with a correction value derived based on the first ratio and the second ratio.

Images