JP2002323801A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of adjusting a transfer condition in accordance with the using condition of an individual user. SOLUTION: The electrophotographic image forming device is provided with a control means making a sensor for detecting a developed image on a photoreceptor detect the density of a developed image before transfer and that of a developed image left after transfer, measuring a transfer rate based on the detected density of both of them, and controlling to select and decide the proper transfer condition based on the measured transfer rate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and more particularly, to an image forming apparatus for forming an image by an electrophotographic method.

[0002]

2. Description of the Related Art Conventionally, an electrophotographic image forming apparatus has been provided. In the electrophotographic image forming apparatus, an image is formed on recording paper through processes such as exposure, development, transfer, and fixing.

In the exposure step, a latent image is formed on the photoreceptor by, for example, a laser beam. In the development step, a visible image is created by attaching toner to the latent image formed on the photoreceptor. Then, the visible image on the photosensitive member is transferred to transfer paper, that is, recording paper, and in the fixing step, the image transferred to the recording paper is fixed to the recording paper by heat.

In such an image forming apparatus, the transfer result in the above-described transfer step varies depending on the environment such as temperature and humidity, and the external factors such as the type and state of the recording paper to be used. For this reason, in the conventional image forming apparatus, the condition is set according to the transfer condition that is evaluated and adjusted in the greatest common divisor using a predetermined designated sheet as a recording sheet, and each user uses under this condition. .

[0005]

However, the actual use conditions of the image forming apparatus differ from user to user, and recording paper of a different paper quality from the designated paper is used, and environmental temperature and humidity are various.

[0006] For this reason, in the conventional image forming apparatus, in some cases, an image cannot be formed well in some cases.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide an image forming apparatus capable of adjusting transfer conditions according to use conditions of individual users.

[0008]

According to the present invention, there is provided an electrophotographic image forming apparatus, comprising:
A sensor for detecting a visible image on the photoreceptor detects the visible image density before transfer and the visible image density of the transfer residue, and measures the transfer rate based on the detected densities. It is characterized by having control means for controlling so as to select and determine an appropriate transfer condition based on the condition.

[0009]

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

In this embodiment, a case where the image forming apparatus is an electrophotographic digital copying machine will be described.

FIG. 1 is a schematic configuration diagram showing a digital copying machine according to an embodiment of the present invention.

In FIG. 1, a digital copying machine 2 includes a scanner section 20 for reading an image of a document, a control section 22 for controlling the overall operation, an image forming section 24 for forming an image on recording paper, and an image forming section. Paper supply unit 2 for supplying recording paper to 24
6, a fixing unit 28 for fixing toner on the recording paper, a paper discharging unit 30 for discharging the recording paper on which an image has been formed, and a display with an input mechanism provided on the upper surface of the digital copying machine 2 and having various input switches. It has a display unit (not shown) which is a device.

The scanner section 20 has a glass plate on its upper surface. When an original is placed on the glass plate and an operation switch is turned on from a display section, a reading lamp or the like moves to read an image of the original. The image of the original is read as a digital signal,
The read image signal is sent to the control unit 22. In the case of copying, an image signal is sent from the control unit 22 to the image forming unit 24, and an image forming process is immediately performed.

The image forming section 24 includes a charger 41 for charging a photosensitive drum 42, a photosensitive drum 42 as a photosensitive member,
An exposure section 46 provided with a laser; a developing device 48 for developing a latent image drawn on the photosensitive drum 42 into a visible image;
Transfer charger 49 for transferring the visible image of No. 2 onto recording paper
And a separation charger 51 for separating the recording paper from the photosensitive drum 42, and a cleaning unit 50 for cleaning the toner remaining on the photosensitive drum 42 after the transfer process. To form an image on the recording paper from the paper supply unit 26.

The paper supply unit 26 stores recording paper of various sizes, and supplies recording paper of a predetermined size to the image forming unit 24 in accordance with an instruction from the control unit 22.

The charger 41 is, for example, a scorotron charger.
Is uniformly charged to a predetermined voltage, for example, 600 V.

Further, in the image forming section 24, the photosensitive drum 42 is formed by coating a photosensitive layer on the surface of a cylindrical substrate made of, for example, aluminum having a diameter of 80 mm.
A drive motor for driving the photosensitive drum 42 and an encoder (not shown) for detecting the rotation phase of the photosensitive drum 42 are provided. The photosensitive layer of the photosensitive drum 42 has a thickness of 15 to 30.
μm, dielectric constant 2.0 to 5.0, and the substrate is grounded. The photosensitive drum 42 rotates at a speed of, for example, 280 mm / sec, and the rotation phase of the photosensitive drum 42 is measured by an encoder. The photosensitive drum 42 is uniformly charged by the charger 41 while rotating, and then is exposed to laser light to form an electrostatic latent image on the surface.

The laser beam emitted from the laser is reflected by a polygon mirror and is irradiated on the surface of the photosensitive drum 42 via an optical system such as an f-θ lens. The polygon mirror is rotating, and the main scanning of the laser beam is performed by the rotation, and the sub-scanning is performed by the rotation of the photosensitive drum 42. The formed electrostatic latent image is visualized by the developer of the developing device 48.

The developing device 48 has a developer having a toner therein, and the toner is transferred from the photosensitive drum 42 onto the recording paper by the transfer charger 49. The recording paper on which the toner has been transferred is transferred to the separation charger 51. And is fixed by the fixing device 53.

The transfer charger 49 is provided so as to face the photosensitive drum 42, and discharges electric charge from the back side of the recording paper superposed on the photosensitive drum 42 electrostatically carrying a toner image, thereby performing recording. Transfer toner to paper. The transfer charger 49 is preferably a scorotron discharger, but may be a corotron charger, a charging roller or the like.

The separation charger 51 includes a scorotron discharger,
Alternatively, the recording paper is composed of a corotron charger, a charging roller, and the like. The recording paper adsorbed on the photosensitive drum 42 is discharged, and the recording paper is separated from the photosensitive drum 42.

The toner remaining on the surface of the photosensitive drum 42 without being transferred is collected by the cleaning unit 50. The cleaning unit 50 includes a blade that comes into contact with the photosensitive drum 42, and scrapes off toner, dust, and the like attached to the surface of the photosensitive drum 42 and stores the scraped toner and toner in the toner box.

The fixing unit 28 includes a fixing device 53, and applies pressure and heat to the recording paper on which the toner image is adhered by the fixing device 53 to fix the toner on the recording paper.

The paper discharge section 30 is a discharge mechanism for discharging the printed recording paper in a predetermined state.

The display unit is provided on the upper surface of the digital copier 2 and is a liquid crystal display device having an input mechanism. Various operation buttons such as enlargement / reduction of a print image, designation of print paper, designation of the number of prints, and the like are provided. Is displayed, and when a finger or the like is pressed on a portion corresponding to the position of the button, for example, a pressure-sensitive pressure-sensitive sensor made of a transparent electrode senses and recognizes that the button is pressed.

In the present embodiment, a density sensor is provided which can detect the density of the visible image formed on the photosensitive drum 42 before and after the transfer process. As this density sensor, for example, a reflection type sensor can be used. This density sensor is, for example, for detecting the density of a patch (image pattern for adjustment) to be drawn for adjustment, and is hereinafter referred to as a patch detection sensor.

Next, the operation of this embodiment will be described.

In the present embodiment, when the apparatus is installed at the place of use of the user, the transfer rate is measured in the user environment, and based on the result, the optimum transfer conditions are set for the user environment. Thereby, a transfer condition with higher accuracy is set.

In this method, the relationship between the transfer current and the transfer rate is obtained by changing the transfer current, and the following steps are carried out. From the result, the optimum transfer current is selected, and the separation according to the transfer current is performed. Determine the current. A visible image is formed on the photosensitive drum 42, and the visible image is read by the patch detection sensor. The visible image is transferred to a transfer sheet, and the remaining toner on the photosensitive drum 42 after the transfer is read by a patch detection sensor. The transfer rate is calculated by comparing the visible image density before transfer and the transfer residual image density. While changing the transfer condition, the above steps are repeated to obtain and select the transfer condition with the best transfer rate.

As the transfer rate, for example, the difference between the output of the patch detection sensor before transfer and the output of the patch detection sensor after transfer may be used as the transfer rate. The ratio between the output of the detection sensor and the output of the remaining patch detection sensor may be used as the transfer rate.

The reflection density is converted from the output of the patch detection sensor and the log value of the amount of light reflected on the photosensitive member, that is, the photosensitive drum 42, and the difference between the image density before transfer and the image density after transfer is used as the transfer rate. Alternatively, the ratio between the image density before transfer and the image density after transfer may be used as the transfer rate.

Before the image density is read by the patch detection sensor, it is desirable to adjust the amount of emitted light so that the surface reflectance of the photosensitive member, that is, the photosensitive drum 42, becomes constant.

The visible image used for adjusting the transfer conditions may be a maximum image density pattern,
It may be an intermediate density pattern, a resolution pattern, an area gradation pattern,
There may be a plurality of visible images or a plurality of visible images having gradation.

One or more patch detection sensors may be provided for reading an image before transfer and for reading an image after transfer, respectively. One device for reading the image after transfer and one for reading the image after transfer may be provided in common.

In the above-described embodiment, a visible image is formed on the photosensitive member, that is, the photosensitive drum 42, the density of the developed image is detected, and then the image is transferred to a transfer paper, that is, a recording paper. The subsequent transfer residual density is detected, and the transfer rate is determined from the visible image density and the transfer residual density. However, the present invention is not limited to this.
Create a visible image on the photoreceptor, detect the density of the visible image, then create the same visible image on the photoreceptor, transfer the image to transfer paper, and detect the residual transfer density after transfer do it,
The transfer rate may be determined from the visible image density and the transfer residual density, or a visible image is created on a photoconductor, the image is transferred to transfer paper, and the transfer residual density after transfer is detected. Then, the same visible image may be formed on the photoconductor, the density of the visible image may be detected, and the transfer rate may be determined from the remaining transfer density and the visible image density.

The transfer rate may be measured a plurality of times at different transfer current values, and an optimum transfer current value may be determined from the obtained transfer rate data.

Further, the separation current value may be determined according to the determined optimum transfer current value.

The transfer paper used for image formation, ie, the recording paper, varies depending on the user, and the transfer rate is as follows.
It also changes depending on the difference of the transfer paper.

Therefore, in this embodiment, the transfer conditions can be made different for each transfer sheet, that is, for each recording sheet, and the optimum transfer conditions can be selected. That is, for example, by performing the above-mentioned steps by using a transfer sheet frequently used by the user, it is possible to select an optimum transfer condition for the transfer.

When the optimum transfer conditions are determined for each type of transfer paper, the storage means provided in the control unit 22 of the digital copying machine 2 stores the type of transfer paper and the optimum transfer conditions (for example, the transfer current value and the transfer current value). (A separation current value).

In actual image formation, when the user selects the type of transfer paper to be used, the control unit 22 refers to a table stored in the storage means and automatically sets transfer conditions. Alternatively, the user may be able to manually select the transfer conditions.

Meanwhile, when measuring the transfer rate, M
When the / A is sampled with a tape, the photoconductor is damaged with the tape and the measurement takes a long time, so that the evaluation is difficult.

Therefore, in the present embodiment, the following 1) to
4) The transfer rate is determined by such a method so that the transferability can be easily measured. This can be used for correction / adjustment / abnormality detection. 1) Baseline correction is performed by the patch detection sensor.
That is, the density of the surface of the photosensitive drum 42 before the formation of a visible image is detected, and this is defined as DATA0. 2) A predetermined SGU (gradation) pattern is formed as a visible image on the photosensitive drum 42, and its density is detected by a patch detection sensor. 3) The pattern of the above 2) is transferred to a transfer sheet, and the density of the remaining toner after the transfer is detected by a patch detection sensor. 4) The obtained data is converted into a printing rate, and the transfer rate is determined from the ratio.

[0044]

## EQU1 ## Density = -log10 (reflectance)

[0045]

D1 = -LN (DATA1 / DATA0) D2 = -LN (DATA2 / DATA0)

[0046]

R = blackening ratio × developer reflectance + (1−blackening ratio) ×
Blank paper reflectance Here, for example, developer reflectance = 0.035481

[0047]

## EQU4 ## R1 = 10^-D1  R2 = 10^-D2

[0048]

## EQU5 ## Black ratio 1 (print ratio 1) = R1 / developer reflectance Black ratio 2 (print ratio 2) = R2 / developer reflectance

[0049]

## EQU6 ## Transfer ratio = (blackening ratio 1-blackening ratio 2) / blackening ratio 1 That is, D1 and D2 are obtained as shown in Expression 2 based on the above basic expressions of Expressions 1 and 3, and thereafter, Equation 4, Equation 5,
The transfer rate can be obtained through Equation 6.

By the way, in the toner recycling system that collects and recycles the toner by the cleaning unit 50 as in the digital copying machine 2 of the present embodiment, the developer is reused. The deterioration of the agent proceeds. That is, as a problem due to the reuse, there is a decrease in the transfer rate due to an increase in the reuse developer.

The developer to be reused is an image formed on the photosensitive member (developer), the remaining developer not transferred to a transfer sheet, that is, a recording sheet, or an image formed for image density correction or the like. , A developer collected without being transferred. As the untransferred developer (transfer residual developer), a developer that is difficult to be transferred in the transfer device is selected and reused, so that a developer that is difficult to transfer remains, so to speak. Become. For this reason, as the use of the image forming apparatus progresses, the amount of reused developer increases, whereby the transfer rate deteriorates, which causes a phenomenon such as a decrease in image density.

Further, since the developer remaining after transfer varies depending on the environment such as temperature and humidity and external factors such as the quality of recording paper, it is difficult to properly evaluate the deterioration of the reused developer. is there.

In the present embodiment, in response to this, after the user starts using the digital copying machine 2, the transfer rate is determined at any time (periodically or at an arbitrary timing). When the transfer rate is worse than a predetermined value, it is assumed that the developer has deteriorated. Alternatively, when the residual toner after transfer becomes larger than a predetermined value, it may be estimated that the developer has deteriorated.

In electrophotography in which electrostatic transfer is performed, discharge is performed to attract a toner image to transfer paper, that is, recording paper. However, this is usually corotron discharge, and the required accuracy is severe. If the specified performance is not achieved due to an installation error or the like, or the toner that durably floats or the paper dust of the recording paper passing through will be attracted, the WIRE and the unit will be stained, and the discharge characteristics will change. Occurs, and sufficient performance cannot be exhibited. For this reason, an expensive high-speed machine or the like that performs high-speed printing periodically performs automatic cleaning, but a relatively inexpensive popular machine class cannot perform automatic cleaning due to cost.

For this reason, in the conventional spread-period class, the timing of cleaning cannot be grasped, and image defects such as transfer unevenness and density reduction occur, and after this image defect occurs, WIRE and units must be cleaned. Did not.

In the present embodiment, in response to this, after the user starts using the digital copying machine 2, the transfer rate is determined at any time (regularly or at an arbitrary timing). It is possible to check the performance, evaluate the performance degradation due to transfer unit abnormalities (assembly mistakes) and durability, and notify the user or maintenance staff of the performance degradation when the performance is degraded. Before that, maintenance can be performed.

[0057]

As described above, according to the present invention,
It is possible to provide an image forming apparatus capable of adjusting transfer conditions according to use conditions of individual users.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a digital copying machine according to an embodiment of the present invention.

[Explanation of symbols]

 2 Digital Copier 20 Scanner Unit 22 Control Unit 24 Image Forming Unit 26 Paper Feeding Unit 28 Fixing Unit 30 Discharge Unit 41 Charger 42 Photosensitive Drum 46 Exposure Unit 48 Developing Device 49 Transfer Charging Unit 51 Separator Charger 50 Cleaning Unit 53 Fixing vessel

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tomoya Motoyoshi 2970, Ishikawacho, Hachioji-shi, Tokyo Konica Corporation (72) Inventor Motoki 2970, Ishikawacho, Hachioji-shi, Tokyo Konica Corporation (72) ) Inventor Eiji Anzai 2970 Ishikawacho, Hachioji-shi, Tokyo F-term in Konica Corporation (reference) 2H027 DA01 DA09 DA10 DA44 DC02 DC19 DE02 EA03 EA18 EF09 HA03 HB02 HB16 2H200 FA18 GA01 GA15 GA23 GA34 GA44 GB12 GB25 GB41 HA12 HB03 HB28 JA02 JA29 JA30 JB10 PA02 PA19 PA22 PA23 PA25 PA26 PB17 PB18 PB19 PB20 PB25 PB39

Claims (30)

[Claims] 1. An electrophotographic image forming apparatus, comprising:
A sensor for detecting a visible image on the photoreceptor detects the visible image density before transfer and the visible image density of the transfer residue, and measures the transfer rate based on the detected densities. An image forming apparatus comprising: a control unit that controls to select and determine an appropriate transfer condition based on the transfer condition. 2. The transfer rate is determined for each type of transfer paper,
2. The image forming apparatus according to claim 1, wherein an optimum transfer condition is determined for each type of the transfer paper. 3. The image forming apparatus according to claim 2, further comprising storage means for storing a table in which the type of the transfer paper is associated with the optimum transfer condition. 4. When a user selects a transfer sheet, the control unit refers to a table stored in the storage unit and automatically sets an optimal transfer condition corresponding to the selected transfer sheet. The image forming apparatus according to claim 3, wherein: 5. The image forming apparatus according to claim 3, wherein the transfer condition can be manually set by a user. 6. The image forming apparatus according to claim 1, wherein the control unit repeatedly measures the transfer rate and determines the transfer condition at a predetermined timing. 7. The image forming apparatus according to claim 6, wherein the predetermined timing is for each maintenance of the apparatus. 8. The image forming apparatus according to claim 6, wherein the predetermined timing is every predetermined number of prints. 9. The image forming apparatus according to claim 6, wherein the deterioration of the developer is estimated based on a comparison result between the measured transfer rate and a predetermined value. 10. The image forming apparatus according to claim 6, wherein deterioration of the developer is estimated based on a change in the transfer rate obtained by measuring the transfer rate at the predetermined timing. apparatus. 11. The image forming apparatus according to claim 1, wherein an abnormality of the transfer unit is estimated based on a comparison result between the measured transfer rate and a predetermined value. 12. The method according to claim 1, wherein the transfer rate is measured a plurality of times at different transfer current values, and an optimum transfer current value is determined based on the obtained transfer rate data.
12. The image forming apparatus according to 2, 6, or 11. 13. According to the determined transfer current value,
3. The method according to claim 1, wherein a separation current value is determined.
12. The image forming apparatus according to 6 or 11. 14. The image forming apparatus according to claim 1, wherein the sensor is a reflection type sensor. 15. The method according to claim 15, wherein a difference between an output of the sensor when reading a visible image before transfer and an output of the sensor when reading a visible image after transfer is used as the transfer rate. Item 12. The image forming apparatus according to Item 1, 2, 6, or 11. 16. The method according to claim 16, wherein a ratio between an output of the sensor when reading a visible image before transfer and an output of the sensor when reading a visible image after transfer is used as the transfer rate. Item 12. The image forming apparatus according to Item 1, 2, 6, or 11. 17. The method according to claim 1, wherein before the image density is read by the sensor, the reflectance of the surface of the photoconductor is constant.
7. The method according to claim 1, wherein an amount of emitted light is adjusted.
Or the image forming apparatus according to 11. 18. A reflection density conversion based on an output of the sensor and a log value of an amount of light reflected on the surface of the photoconductor, and a difference between an image density before transfer and an image density after transfer is used as the transfer rate. Claim 1, 2, 6, or 11
4. The image forming apparatus according to claim 1. 19. A reflection density conversion based on an output of the sensor and a log value of a light amount reflected on the surface of the photoconductor, and a ratio between an image density before transfer and an image density after transfer is used as the transfer rate. Claim 1, 2, 6, or 11
4. The image forming apparatus according to claim 1. 20. The image forming apparatus according to claim 1, wherein the visible image is a highest image density pattern. 21. The image forming apparatus according to claim 1, wherein the visible image is an intermediate density pattern. 22. The image forming apparatus according to claim 1, wherein the visible image is a resolution pattern. 23. The image forming apparatus according to claim 1, wherein the visible image is an area gradation pattern. 24. The image forming apparatus according to claim 1, wherein the visible image is a plurality of visible images. 25. The image forming apparatus according to claim 1, wherein the visible image is a plurality of visible images having a gradation property. 26. The sensor according to claim 1, wherein at least one sensor for reading a visible image before transfer and one for reading a visible image after transfer are provided as the sensor. 12. The image forming apparatus according to item 11. 27. The apparatus according to claim 1, wherein the sensor is provided with only one for reading an image before transfer and one for reading an image after transfer.
12. The image forming apparatus according to 2, 6, or 11. 28. A developed image is formed on the photoreceptor, the result of detecting the density of the developed image by the sensor is defined as the developed image density before the transfer, and then the image is transferred to a transfer paper. 2. The method according to claim 1, wherein a residual image density after transfer is detected by the sensor as a visible image density of the residual image.
12. The image forming apparatus according to 2, 6, or 11. 29. A visible image is formed on the photoconductor, and the result of detecting the density of the visual image with the sensor is defined as the visual image density before the transfer, and thereafter, the same as the visual image on the photoconductor. And generating a new visible image, transferring the generated visible image to a transfer sheet, and detecting the residual transfer density after the transfer by the sensor as the residual residual visible image density. 12. The image forming apparatus according to 1, 2, 6, or 11. 30. A visible image is formed on the photoreceptor, the image is transferred to a transfer paper, and a result of detecting the residual transfer density after the transfer by the sensor is defined as the visible image density of the residual transfer. Forming a visible image identical to the visible image on the photoreceptor, and detecting the density of the generated visible image with the sensor as the visible image density before the transfer. 12. The image forming apparatus according to 2, 6, or 11.