JP2004046015A - Image forming device - Google Patents

Abstract

An image forming apparatus capable of reliably and efficiently removing a developer adhered to a transfer member is provided.
An image forming apparatus applies a voltage having the same polarity as toner to the transfer device and re-transfers the toner attached on the transfer device onto the photoreceptor. A high-voltage unit 9, a first optical sensor 6 for detecting at least one of the toner concentration and the toner amount of the toner image adhered on the photoconductor 1 after the transfer of the toner image, and a first optical sensor 6 on the photoconductor 1 after the transfer of the toner image; And a control unit 8 for adjusting retransfer conditions by the high-voltage unit 9 based on the detection value of the first optical sensor 6. The control unit 8 predicts the amount of toner on the transfer belt 14 from the detection result of the first optical sensor 6, and adjusts the retransfer condition based on the prediction result.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus such as a printer, a copying machine, a facsimile machine, or the like, which employs an electrophotographic system.
[0002]
[Prior art]
2. Description of the Related Art Generally, an image forming apparatus such as a printer, a copying machine, a facsimile machine, or the like, which employs an electrophotographic method, has a cylindrical or endless belt-shaped photosensitive member, and a toner image (a developer) formed on the photosensitive member. The image is transferred to a sheet (transfer material) to form a copy image, and a transfer device that arranges a charger wire and performs corona discharge is employed. Since the transfer device generates ozone during corona discharge, an ozone filter for removing ozone is disposed near an exhaust port of the image forming apparatus. Air containing ozone inside the image forming apparatus passes through an ozone filter, and is exhausted after ozone is removed.
[0003]
However, the exhaust method of passing through the ozone filter cannot remove all ozone. Therefore, an image forming apparatus employing a transfer device having a transfer belt or a transfer roller (hereinafter, referred to as a transfer body) instead of the transfer device having the charger wire is increasing.
[0004]
The transfer member is disposed so as to approach or contact the surface of the photoconductor. Then, by applying a high-voltage bias (DC) to the transfer body, the toner image formed on the photoconductor is transferred to a sheet.
[0005]
The use of a transfer device having such a transfer body not only makes it possible to suppress the amount of ozone generated, but also to prevent transfer deviation when a toner image is transferred.
[0006]
In addition, various members (for example, a photosensitive member, an exposure source, a developing device, a transfer member, a cleaning blade, and the like) related to image formation of an image forming apparatus employing an electrophotographic method deteriorate with time. The quality (image quality) of a copy image formed on a sheet greatly depends on the degree of deterioration of these various members and environmental changes such as temperature and humidity.
[0007]
For this reason, a control method for preventing the change in image quality is adopted. As the control method, for example, after a test toner image (toner patch) is formed on a photoconductor under a predetermined condition, at least one of the density of the test toner image on the photoconductor and the toner adhesion amount (hereinafter referred to as toner amount) is used. And the like, and a control method of adjusting the image quality by feeding back the detection result to the image forming process is adopted. As a result, it is possible to prevent a change in image quality, and it is possible to always form an image having an appropriate image quality.
[0008]
Japanese Patent Application Laid-Open No. H11-219045 discloses an image forming apparatus provided with a transfer device using a transfer roller. The image forming apparatus disclosed in this publication has a photoconductor 21 and a transfer roller 22 as shown in FIG.
[0009]
The transfer roller 22 and the photoconductor 21 are arranged so as to be in contact with each other, and the transfer roller 22 rotates following the rotation of the photoconductor 21. For this reason, when the toner image (toner patch) formed on the photoconductor 21 contacts the transfer roller 22, the toner that is a part of the toner image (toner patch) falls on the surface of the transfer roller 22 and May adhere to the surface. Therefore, as a method for preventing this, a voltage having the same polarity as the charging polarity of the toner is applied to the transfer roller 22.
[0010]
However, even when a voltage having the same polarity as that of the toner is applied to the transfer roller 22, the amount of toner adhering to the photoconductor 21 is reduced by the voltage applied to the transfer roller 22. If the repulsion is too large, the toner on the photoconductor 21 may fall on the surface of the transfer roller 22 and the toner may adhere to the surface of the transfer roller 22. In this case, the amount of toner adhering to the surface of the transfer roller 22 depends on changes in the environment around the installation location of the image forming apparatus and in the apparatus, deterioration of the photoreceptor 21 and the transfer roller 22, etc. It changes with changes.
[0011]
When the sheet passes through the transfer roller 22 in a state where the toner adheres to the surface of the transfer roller 22 in this way, the toner adheres to the back side of the sheet, and so-called back stain occurs.
[0012]
There is known a method of removing toner attached to the transfer roller 22 in order to prevent back stains. In this method, a voltage having the same polarity as that of the toner is applied to the transfer roller 22, and the toner adhered to the transfer roller 22 is retransferred to the photoconductor 21 to remove the toner.
[0013]
[Problems to be solved by the invention]
However, the conventional image forming apparatus always applies a predetermined voltage to the transfer roller for a predetermined time. For this reason, in the conventional image forming apparatus, it is necessary to set the time for applying the voltage longer than the time when the removal of the toner is expected to be completed.
[0014]
In this case, when the toner adhesion amount is larger than the expected amount, that is, when the set voltage application time is short, the toner removal process is performed even though all the toner adhered to the transfer roller has not been removed. It ends. For this reason, the toner remaining on the transfer roller causes back contamination of the paper.
[0015]
On the other hand, when the toner adhesion amount is smaller than the expected amount, that is, when the set voltage application time is long, the toner is unnecessarily necessary despite the fact that all the toner adhering to the transfer roller has been removed. A removal step will be performed.
[0016]
In this case, various members related to the toner removal are driven uselessly. Then, there is a possibility that problems such as deterioration of various members, generation of abnormal sound, and component replacement due to component trouble may occur. For example, when a cylindrical photosensitive drum is used as the photosensitive member, the photosensitive material (photosensitive layer) applied to the drum tube is gradually scraped, and the life is shortened. Further, the reduction in the thickness of the photosensitive layer affects the image quality of the reproduced image.
[0017]
On the other hand, designing in consideration of the life of the parts increases the cost of each part, which may affect the price of the device or the price of the replacement part, and is difficult to implement.
[0018]
The present invention has been proposed to solve the above problem, and provides an image forming apparatus capable of reliably and efficiently removing a developer adhered to a transfer body (a transfer belt, a transfer roller, or the like). The purpose is to do.
[0019]
[Means for Solving the Problems]
An image forming apparatus according to the present invention includes an image carrier (for example, a photoconductor such as a photoconductor drum or a photoconductor belt) on which a developer image is formed, and a developer image formed on the image carrier. A transfer unit (for example, a transfer member (transfer device) such as a transfer belt or a transfer roller) for transferring a toner image (for example, a toner image) to a transfer material (for example, transfer paper) and a voltage having the same polarity as the developer are applied to the transfer unit. Voltage applying means (for example, a high-voltage unit) for applying the developer which has been applied to the transfer means to re-transfer the developer onto the image carrier; and a visual image attached to the image carrier after transfer. First detection means (for example, an optical sensor) for detecting at least one of the density of the developer image and the amount of the developer, and developer removing means for removing the developer adhering to the image carrier after transfer (E.g., a cleaning device) and a detection value of the first detection unit. There are, is characterized in that it has an adjusting means for adjusting (e.g., a central processing unit controller such as a) the re-transfer conditions by the voltage application means.
[0020]
According to the above configuration, by adjusting the retransfer condition by the voltage applying means by the adjusting means, the voltage (cleaning) can be applied to the transferring means under a condition corresponding to the amount of the developer adhered to the transferring means. Bias) can be applied. For this reason, according to the configuration, it is possible to reliably and efficiently apply a voltage necessary for retransferring the developer adhered to the transfer unit to the image carrier, to the transfer unit. The developer adhered to the transfer means can be efficiently and reliably removed (cleaned). Therefore, as in the prior art, the transfer material is not sufficiently cleaned, and the backing of the transfer material, deterioration of various members caused by performing the cleaning operation more than necessary, generation of abnormal noise, replacement of parts due to parts trouble, etc. Can be avoided, and the life of components can be prolonged and the quality of reproduced images can be improved. Further, according to the above configuration, it is not necessary to perform a design in consideration of the life of the component due to the useless cleaning operation, and it is possible to provide an inexpensive image forming apparatus.
[0021]
The image forming apparatus according to the present invention is characterized in that, in addition to the above configuration, the first detecting means is a first optical sensor.
[0022]
According to the arrangement, since the first detection means is an optical sensor (first optical sensor), the density and the amount of the developer image adhered to the image carrier after the transfer are obtained. Can be optically detected, and the density and the amount of the developer image can be accurately and simply detected without being affected by environmental changes such as temperature and humidity.
[0023]
The image forming apparatus according to the present invention is characterized in that, in addition to the above configuration, the first detecting means is provided downstream of the transfer means in the rotation direction of the image carrier.
[0024]
According to the above configuration, after the developer on the image carrier passes through the transfer unit, the image carrier comes into contact with the transfer unit or the developer falls from the image carrier onto the transfer unit, so that the transfer is performed. It is possible to efficiently detect the density of the developer image or the developer amount attached to the means.
[0025]
The image forming apparatus according to the present invention, in addition to the above-described configuration, further includes a developing agent image before transfer formed on the image carrier, on the upstream side in the rotation direction of the image carrier with respect to the transfer unit. The image forming apparatus further includes a second detecting unit that detects at least one of a density and a developer amount before transfer attached to the image carrier. The adjusting unit includes a detection value of the second detecting unit and the detection value of the second detecting unit. The amount of the developer adhered to the transfer unit is predicted from the detection value of the first detection unit, and the retransfer condition is adjusted based on the prediction result.
[0026]
According to the above configuration, it is possible to detect the density and / or the amount of the developer before the developer on the image carrier passes through the transfer unit. For this reason, it is possible to detect the concentration and / or the amount of the developer before and after the developer on the image carrier passes through the transfer unit, in combination with the detection value of the first detector. By comparing the detection values before and after passing through the transfer unit, the amount of the developer adhered to the transfer unit can be easily and accurately predicted. Therefore, according to the configuration, it is possible to more reliably and efficiently apply a voltage necessary for retransferring the developer adhered to the transfer unit to the image carrier, to the transfer unit. The developer adhered to the transfer means can be efficiently and reliably removed (cleaned).
[0027]
The image forming apparatus according to the present invention is characterized in that, in addition to the above configuration, the second detecting means is a second optical sensor.
[0028]
According to the above configuration, since the second detection unit is an optical sensor (second optical sensor), the developer on the image carrier before the developer on the image carrier passes through the transfer unit. The density and amount of developer can be optically detected, and the density and amount of developer can be accurately and accurately determined without being affected by environmental changes such as temperature and humidity. It can be easily detected.
In the image forming apparatus according to the present invention, in addition to the above configuration, the adjusting unit adjusts the retransfer condition so that the retransfer is repeated until a desired detection result is obtained by the first detecting unit. Features.
[0029]
According to the above configuration, the retransfer, that is, the cleaning operation of the transfer unit is repeated, so that a voltage (retransfer bias) having the same polarity as the developer is applied to the transfer unit, and the image carrier is applied to the image carrier. Since the change in the amount of the developer to be retransferred is read by the first detection means, the change in the retransfer amount from the transfer means to the image carrier, that is, the amount of toner adhering to the transfer means gradually decreases. The above-mentioned retransfer can be performed while confirming the state of decrease. Therefore, the developer remaining (adhering) on the transfer means can be surely removed even by the retransfer, and the retransfer can be prevented from being repeated more than necessary. The developer adhered on the transfer means can be efficiently retransferred to the image carrier.
[0030]
In the image forming apparatus according to the present invention, in addition to the above-described configuration, the transfer unit includes an endless transfer belt or a transfer roller, and the first detection unit is configured to detect a position of the image carrier and the transfer unit. The circumference in the rotation direction of the image carrier from the contact point to the point where the first detection means detects the density or the amount of the developer image on the image carrier is larger than the circumference of the transfer means. Is also provided to be shorter.
[0031]
According to the above configuration, the developer adhered to the transfer unit moves with the rotation of the transfer unit after coming into contact with the image carrier, and then moves until it comes into contact with the image carrier again. The first detecting means can detect the concentration of the developer or the amount of the developer on the image carrier. Therefore, according to the above configuration, the detection of the density of the developer image on the image carrier and / or the amount of the developer is performed immediately after the developer on the image carrier passes through the transfer unit. Therefore, the adjustment of the retransfer conditions can be promptly performed. Therefore, the retransfer can be performed more efficiently.
[0032]
In the image forming apparatus according to the present invention, in addition to the above-described configuration, the adjusting unit adjusts at least one of a voltage value applied by the voltage applying unit to the transfer unit and a voltage application time as the retransfer condition. Features.
[0033]
According to the configuration, it is possible to apply a voltage (cleaning bias) according to the amount of the developer adhered to the transfer unit to the transfer unit. For this reason, according to the configuration, it is possible to reliably and efficiently apply a voltage necessary for retransferring the developer adhered to the transfer unit to the image carrier, to the transfer unit. The developer adhered to the transfer means can be efficiently and reliably removed (cleaned).
[0034]
BEST MODE FOR CARRYING OUT THE INVENTION
[Embodiment 1]
A first embodiment of the present invention will be described with reference to FIGS.
[0035]
As shown in FIG. 1, the image forming apparatus according to the present embodiment includes a photoconductor 1 (image carrier), a charging device 2, an exposure device 3, a developing device 4, a transfer device 5 (transfer unit), An optical sensor 6 (first detecting unit), a cleaning device 7 (developing agent removing unit), a control unit 8 (adjusting unit), a high-pressure unit 9 (voltage applying unit), and a paper feed roller pair 11 are provided.
[0036]
The photoconductor 1 is a photoconductor drum that is driven to rotate in the direction of arrow A (clockwise), and an electrostatic latent image and a toner image for image formation are formed on the surface thereof. FIG. 1 shows a configuration around the photoconductor 1. As shown in FIG. 1, around the photoconductor 1, from the irradiation position of the laser beam 16 from the exposure device 3, the exposure device 3, the developing device 4, the transfer device 5, One optical sensor 6, the cleaning device 7, and the charging device 2 are arranged in this order.
[0037]
The charging device 2 includes a charging roller 12 disposed so as to be in contact with the photoreceptor 1. The charging roller 12 is driven by the rotation of the photoreceptor 1 to rotate in the direction of rotation of the photoreceptor 1 (in the direction of arrow A in FIG. 1). ), The surface of the photoreceptor 1 from which the residual charges have been removed is uniformly charged to a predetermined potential by rotating in the direction opposite to the direction (arrow B in FIG. 1).
[0038]
The exposure device 3 has a laser light source, is arranged at a position separated from the photoconductor 1, and is image information input from a scanner unit (document reading device) (not shown) or a host computer (not shown) connected to the outside, or A laser beam 16 modulated based on digital data (image signal) indicating image information such as facsimile information sent by communication or the like is emitted, and the photosensitive device is charged to a predetermined level (reference level) by the charging device 2. By exposing (scanning) the surface of the body 1, an electrostatic latent image is formed on the photoconductor 1.
[0039]
The developing device 4 includes a developing roller 13b that supplies the toner (developing agent) stored in the developing tank 13a to the photoconductor 1, and is formed on the photoconductor 1 by exposing the laser beam 16 by the exposure device 3. The electrostatic latent image is formed into a visible image (toner image) by toner. The developing roller 13b is in contact with the photoconductor 1, and rotates in a direction opposite to the rotation direction of the photoconductor 1 following the rotation of the photoconductor 1.
[0040]
The transfer device 5 transfers the toner image formed on the photoreceptor 1 to the transfer material 10 by making contact with the photoreceptor drum via the transfer material 10. The transfer device 5 has a configuration in which an endless transfer belt 14 (transfer member) having a peripheral length shorter than the peripheral length of the photoconductor 1 is supported by support rollers 17a and 17b. Reference numeral 14 is such that one of the support rollers 17a and 17b is pressed against the photosensitive member 1 via the transfer material 10 by one of the support rollers 17a. As a result, the transfer belt 14 rotates following the rotation of the photoconductor 1 in a direction opposite to the rotation direction of the photoconductor 1.
[0041]
In the present embodiment, the first photosensor 6 is located downstream of the transfer device 5 in the rotation direction of the photoconductor 1 and upstream of the cleaning device 7 in the rotation direction of the photoconductor 1. 1 and spaced apart from each other. Accordingly, the first optical sensor 6 irradiates the photoconductor 1 with light, so that the toner image formed on the photoconductor 1 adheres to the photoconductor 1 after passing through the transfer device 5. At least one of the toner density (reflectance) and the toner amount of the transferred toner image, that is, at least one of the toner density and the toner amount of the toner image adhered on the photoconductor 1 after the transfer is detected. By using an optical sensor to detect the toner concentration and the toner amount, the toner concentration and the toner amount can be optically detected, and the toner concentration and the toner amount can be detected without being affected by environmental changes such as temperature and humidity. And the amount of toner can be detected accurately and easily. As the first optical sensor 6, an optical sensor similar to an optical sensor conventionally used for process control can be used.
[0042]
The cleaning device 7 includes a cleaning roller 15a and a cleaning blade 15b. The cleaning roller 15 a is provided so as to be in contact with the photoconductor 1, and follows the rotation of the photoconductor 1 and rotates in the opposite direction to the rotation direction of the photoconductor 1, thereby removing the surface of the photoconductor 1. It is supposed to. On the other hand, the cleaning blade 15b is made of an elastic material, and is brought into direct contact with the photoreceptor 1 to scrape off the toner adhering to the photoreceptor 1, thereby remaining on the surface of the photoreceptor 1 after the transfer of the toner image (adhesion). ) Is removed and collected.
[0043]
The control unit 8 performs control related to image formation, that is, drive control of each member and adjustment of image quality and bias. Further, the control unit 8 performs control related to cleaning (re-transfer) of the transfer device 5 in addition to the above control. Specifically, the control unit 8 changes the re-transfer condition by the high-voltage unit 9 based on the detection value of the first optical sensor 6 to the first optical sensor 6 after removing the toner by the cleaning device 7. Is adjusted so that the detected value is smaller than or equal to a predetermined value. That is, the controller 8 adjusts the retransfer conditions so that the toner adhering to the transfer device 5 is reliably and efficiently removed. Preferably, the toner adhering to the transfer device 5 is completely removed. It is adjusted to be removed. As the control unit 8, for example, a central processing unit (CPU) can be used.
[0044]
The high-voltage unit 9 switches and applies a transfer bias or a re-transfer bias (cleaning bias) to the transfer belt 14 based on a control signal transmitted from the control unit 8. The transfer bias is a voltage applied to transfer the toner image on the photoconductor 1 to the transfer material 10. On the other hand, the retransfer bias is a voltage applied to retransfer the toner on the transfer belt 14 to the photoconductor 1.
[0045]
The paper feed roller pair 11 transports the transfer material 10 between the photoconductor 1 and the transfer device 5. The paper feed roller pair 11 conveys the transfer material 10 by rotating while sandwiching the transfer material 10 between two rollers.
[0046]
On the upstream side in the transport direction of the transfer material 10 with respect to the paper feed roller pair 11, a paper feed device (not shown) that stocks the transfer material 10 and supplies the transfer material 10 to the paper feed roller pair 11 is provided. ing. Further, a fixing device (not shown) for fusing and fixing the toner image transferred onto the transfer material 10 is provided downstream of the transfer device 5 in the transport direction of the transfer material 10.
[0047]
An image forming method in the image forming apparatus according to the present embodiment having the above configuration will be described.
[0048]
First, the surface of the photoconductor 1 is uniformly charged by the charging device 2. The exposure device 3 emits a laser beam 16 modulated based on image information to be formed. An electrostatic latent image is formed on the photoreceptor 1 by sequentially exposing the surface of the photoreceptor 1 charged uniformly with the laser beam 16 in a line unit in the main scanning direction. The electrostatic latent image formed on the photoconductor 1 passes through the developing device 4, and the toner in the developing device 4 is electrostatically attracted to the electrostatic latent image on the photoconductor 1 at that time. The electrostatic latent image is visualized as a toner image. The transfer device 5 transfers the toner image formed on the photoreceptor 1 to a transfer material 10 fed from a pair of feed rollers 11. Thereafter, the transfer material 10 is transported to a fixing device (not shown), and the toner image is fixed on the transfer material 10 by the fixing device, and is made a permanent visible image.
[0049]
In performing the above-described image forming process, the image quality of an image to be formed is adjusted in advance. The image quality adjustment is performed by the controller 8 adjusting the output such as the charging level, the exposure level, the developing bias or the transfer level, and the output adjustment is called process control.
[0050]
Image quality adjustment by process control is performed by the following method. A toner pattern image is formed on the surface of the photoconductor 1 on a trial basis under predetermined conditions, and the first optical sensor 6 detects the amount of toner adhering to the photoconductor 1. The image quality is adjusted by controlling at least a part of the image forming apparatus (electrophotographic process) based on the detection result.
[0051]
Specifically, first, the charging device 2 uniformly (uniformly) charges the surface of the photoconductor 1 to a predetermined level (reference level). The laser beam 16 modulated so as to form a pattern image (toner image) of a specific shape exposes (scans) the surface of the charged photoconductor 1. An electrostatic latent image is formed on the exposed portion of the surface of the photoconductor 1, and the electrostatic latent image is visualized by the developing device 4 as a toner pattern image having a specific shape. After the visualized toner pattern image of the specific shape passes through the transfer device 5, the first optical sensor 6 detects the amount of toner attached (toner density) on the surface of the photoconductor 1. The detection signal is transmitted to the control unit 8, and the control unit 8 adjusts the image quality formed based on the detection result. Thus, an image whose image quality has been adjusted can be formed.
[0052]
It should be noted that the image data (electrophotographic data) to be formed can be subjected to image processing to correct the image quality (such as density correction) based on the detection data detected by the first optical sensor 6.
[0053]
Next, an example of a process in which the controller 8 adjusts the retransfer conditions to remove the toner adhered on the transfer belt 14 will be described.
[0054]
First, after the toner image formed on the surface of the photoconductor 1 passes through the transfer belt 14, that is, after the transfer, the first optical sensor 6 adheres (remains) on the photoconductor 1 after the transfer. The density of the existing toner image or the toner adhesion amount is detected. This detection result (detection value) is sent to the control unit 8 as a density detection signal (toner amount detection signal).
[0055]
The control unit 8 compares the density detection signal with a toner density detection signal (toner amount detection signal) of the toner density or the toner adhesion amount of the toner pattern image detected at the time of the process control, so that the control unit 8 adheres to the transfer belt 14. The amount of adhered toner is predicted, and the voltage (re-transfer bias) applied to the transfer belt 14 is adjusted based on the prediction result so that the toner adhered to the transfer belt 14 is reliably and efficiently removed. (Set, change).
[0056]
The high-voltage unit 9 transfers a voltage (re-transfer bias) having the same polarity as that of the toner based on the re-transfer condition set (changed) by the control unit 8 according to a signal (control signal) from the control unit 8. Apply to belt 14. As a result, the toner adhered to the transfer belt 14 is retransferred to the photoconductor 1. The toner re-transferred onto the photoconductor 1 is removed from the photoconductor 1 by the cleaning device 7. Thus, the transfer belt 14 can be cleaned.
[0057]
A specific method of estimating the amount of adhered toner is performed by calculation or by referring to a table. For example, the method is predicted by the following means. First, image formation is performed under predetermined conditions. At this time, the toner adhesion amount on the photoreceptor 1 is obtained by an experiment or the like, and is recorded in the control unit 8 in advance (predicted adhesion amount). On the other hand, a detection signal based on the toner concentration on the photoconductor 1 detected by the first optical sensor 6 is input to the control unit 8 via communication means such as an interface. Know the amount (detected adhesion amount). The control unit 8 estimates the toner adhesion amount on the surface of the transfer belt 14 by comparing these. That is, “predicted adhesion amount−detected adhesion amount = toner adhesion amount”.
[0058]
The control unit 8 adjusts the retransfer conditions, that is, controls the high-pressure unit 9, by controlling the transfer belt 14 predicted based on the toner density detection signal (toner amount detection signal) detected by the first optical sensor 6. The control unit 8 changes the voltage value or the voltage application time of the retransfer bias applied to the transfer belt 14 in accordance with the above toner adhesion amount. For example, when it is predicted that the toner adhesion amount on the transfer belt 14 is large, the application level such as voltage and time is set to be large, and conversely, when the toner adhesion amount on the transfer belt 14 is predicted to be small, , The application level is set low.
[0059]
Here, the relationship between the application time of the retransfer bias applied to the transfer belt 14 and the voltage will be described. FIG. 2 is a timing chart showing the relationship between the increase and decrease of the time for re-transferring the toner adhered on the transfer belt 14 to the photosensitive member 1 and the magnitude of the voltage level applied to the transfer belt 14. In FIG. 2, what is indicated by a solid line is the lowest level voltage application condition, and indicates that the voltage is increased stepwise or linearly (linearly) as the toner adhesion amount increases.
[0060]
Specifically, the retransfer bias to the transfer belt 14 is applied, and at the same time, the retransfer of the toner adhered on the transfer belt 14 to the photoconductor 1 is started (C1 in FIG. 2). Then, after the re-transfer time set in advance by the control unit 8 has elapsed (C2 in FIG. 2), the application of the re-transfer bias is stopped after a predetermined time has passed (C3 in FIG. 2). This is to ensure that the toner is retransferred. In addition, since the time and voltage to be applied are controlled according to the predicted amount of toner, when the predicted amount of toner is large, the retransfer time is naturally long as shown by the dotted line in FIG. As the voltage increases, the applied voltage also increases. In this case, similarly to the above, after the retransfer time has elapsed (C4 in FIG. 2), the application of the retransfer bias is stopped after a predetermined time has passed (C5 in FIG. 2).
[0061]
As described above, in the present embodiment, after the transfer step, the control unit 8 determines the transfer device 5 based on the amount of toner adhering to the transfer device 5 (transfer belt 14) obtained from the detection value of the first optical sensor 6. The re-transfer conditions, that is, the cleaning conditions, are adjusted so that the cleaning state (toner adhesion state) becomes a desired state. The retransfer condition is adjusted, for example, so that the toner adhered to the back surface of the transfer material 10 after the transfer becomes inconspicuous. More specifically, the re-transfer condition is determined, for example, from the amount of toner adhering to the transfer device 5 obtained from the above-described detection value of the first optical sensor 6 and the detection by the first optical sensor 6 after removing the toner. The value is adjusted so that the value is equal to or less than a predetermined value. More preferably, the retransfer condition is such that the toner adhering to the transfer device 5 is removed from the amount of toner adhering to the transfer device 5 obtained from the detection value of the first optical sensor 6 (the first transfer sensor 5). The amount of toner determined from the value detected by the optical sensor 6 is removed. By adjusting the re-transfer conditions based on the toner adhesion amount obtained from the detection value of the first optical sensor 6 as described above, it is possible to prevent noticeable toner adhesion on the back surface of the transfer material 10 after the transfer. .
[0062]
Note that the cleaning state is also affected by the environment such as temperature or humidity. Therefore, as the image forming apparatus, for example, a temperature detection unit (a temperature measurement unit such as a thermometer or a temperature input unit) and / or a humidity detection unit Means (humidity measuring means such as a hygrometer or humidity input means), and the control section 8 detects the value detected by the first optical sensor 6 and the temperature detected by the temperature detecting means and / or the humidity detecting means. It is more preferable to have a configuration for adjusting the retransfer conditions based on the temperature and / or humidity. That is, it is more preferable that the retransfer conditions are adjusted (set) in consideration of temperature, humidity, and the like.
[0063]
As described above, according to the present embodiment, the control unit 8 transmits the application time and the applied voltage value of the retransfer bias to the high-voltage unit 9, and the high-voltage unit 9 transmits the application condition transmitted from the control unit 8. By applying the re-transfer bias to the transfer belt 14, a voltage necessary for re-transferring the toner adhered to the transfer belt to the photoconductor 1 is applied to the transfer belt 14. This makes it possible to retransfer the toner on the transfer belt 14 to the photoconductor 1, that is, to remove (clean) the toner attached to the transfer belt 14.
[0064]
In addition, by using the above-described toner retransfer method, it is possible to execute the cleaning process according to the amount of the toner adhered to the transfer belt 14, so that the transfer belt 14 can be reliably and efficiently cleaned. This can be performed, and the back contamination of the transfer material 10 can be prevented.
[0065]
As described above, the bias application level is not only set by switching between high and low in accordance with, for example, a difference in toner adhesion amount, but also, for example, bias application of a plurality of levels (multiple stages) is performed in accordance with an assumed toner adhesion amount. The level may be set, and the level may be switched according to the assumed amount of toner adhesion.
[0066]
[Embodiment 2]
A second embodiment of the present invention will be described with reference to FIGS. Further, for convenience of explanation, members having the same functions as those described in the first embodiment are given the same numbers, and descriptions thereof are omitted. In the present embodiment, differences from the above-described first embodiment will be mainly described.
[0067]
As shown in FIG. 3, the image forming apparatus according to the present embodiment includes a photoconductor 1, a charging device 2, an exposure device 3, a developing device 4, a transfer device 5, a first optical sensor, as in the first embodiment. 6, a cleaning device 7, a control unit 8, a high-pressure unit 9, and a paper feed roller pair 11.
[0068]
In FIG. 3, P1 denotes a point at which the photosensitive member 1 contacts the transfer belt 14, and P2 denotes a point at the photosensitive member 1 at which the first optical sensor 6 detects the toner density on the photosensitive member 1. It is. L1 is the circumferential length of the transfer belt 14, and L2 is the photosensitive length from the contact point between the photosensitive member 1 and the transfer belt 14 to the point where the first optical sensor 6 detects the amount of toner on the photosensitive member 1. The circumferential length of the body 1 in the rotation direction. That is, it is the length of the outer circumference of the photoconductor 1 from P1 to P2.
[0069]
In the present embodiment, L1 and L2 are set such that L1> L2. That is, the toner adhering to the transfer belt 14 comes into contact with the photoreceptor 1 repeatedly at a constant period (peripheral length of the transfer belt 14), but the first light is located at a position where L1> L2. By disposing the sensor 6, when the photoconductor 1 and the transfer belt 14 come into contact with each other at P1 after the transfer process, a part of the toner attached on the transfer belt 14 is retransferred to the photoconductor 1. The first optical sensor 6 determines the toner density re-transferred onto the photoconductor 1 until the remaining toner adhering on the transfer belt 14 comes into contact with the photoconductor 1 again as the transfer belt 14 rotates. It can be detected.
[0070]
This makes it possible to quickly execute the control of the retransfer bias according to the detection result.
[0071]
Specifically, as shown in FIG. 4, after the toner on the transfer belt 14 comes into contact with the photoconductor 1 and before it comes into contact with the photoconductor 1 again (L1 in FIG. 4), the first optical sensor 6 (L2 in FIG. 4). T1 to T4 represent toner pattern images (test toner images) on the photoreceptor 1 to which the toner on the transfer belt 14 has been re-transferred, and time elapses from T1 to T4. That is, T1 to T4 represent toner pattern images on the photoconductor 1 for each retransfer.
[0072]
First, the density of the toner pattern image T1 retransferred to the photoconductor 1 is detected by the first optical sensor 6 until the toner on the transfer belt 14 is retransferred to the photoconductor 1 next time. A retransfer bias controlled based on the detection result is applied to the transfer belt 14. Then, the toner on the transfer belt 14 is re-transferred to the photoreceptor 1 again to form a toner pattern image T2. Similarly, the toner density of the toner pattern image T2 is detected by the first optical sensor 6 until the toner on the transfer belt 14 is re-transferred to the photoconductor 1, and the re-transfer is controlled to the transfer belt 14. A bias is applied.
[0073]
The detection of the toner density of the toner pattern image thus re-transferred, the adjustment of the re-transfer bias, and the application of the re-transfer bias are performed quickly, so that the toner pattern image repeatedly re-transferred to the photoconductor 1 is obtained. The toner density gradually decreases (from T1 to T4 in FIG. 4). Thus, the toner on the transfer belt 14 can be removed in a minimum time. The re-transfer is repeated, and is terminated after it is confirmed by the output of the first optical sensor that the density of the toner pattern image Tn (where n is a natural number of 2 or more) has become equal to or less than a predetermined level. I do.
[0074]
As described above, in the above-described retransfer process, after the toner image formed on the surface of the photoreceptor 1 has passed through the transfer belt 14, that is, after the transfer, the transfer belt having a part of the toner image adhered to the surface is transferred. While applying a bias (retransfer bias) of the same polarity as the toner to the photoconductor 14, the density change (change in the amount of adhered toner) of the toner pattern image (test toner image) retransferred to the photoconductor 1 is determined by the first method. The density of the toner pattern image read by the optical sensor 6 and the density (toner adhesion amount) of the toner pattern image read by the first optical sensor 6, that is, the toner pattern until the detection value of the first optical sensor 6 becomes a predetermined value or less. The cleaning operation (removal of toner) is repeatedly performed by repeating the creation (retransfer) of the image and the detection of the density (toner adhesion amount) of the toner pattern image. That is, in the re-transfer process, the control unit 8 adjusts the re-transfer condition based on the detection value of the first optical sensor 6 to the transfer device 5 based on the detection value of the first optical sensor 6. The presence or absence of the adhered toner and the level of the amount of the toner adhered to the transfer device 5 are determined, and the cleaning state (toner adhered state) of the transfer device 5 is set to a desired state. This shows that the retransfer conditions are adjusted so that the toner attached to the transfer device 5 is removed. Specifically, for example, the retransfer conditions are adjusted (set or changed) so that the value detected by the first optical sensor 6 after removing the toner by the cleaning device 7 is equal to or less than a predetermined value.
[0075]
In the present embodiment, the adjustment of the retransfer conditions in the control unit 8, that is, the control of the high-voltage unit 9, is performed based on the toner density detection signal (toner amount detection signal) detected by the first optical sensor 6. This is performed by setting whether or not to perform the cleaning operation (retransfer operation). At this time, the applied voltage value and the voltage application time by the high-voltage unit 9 may be adjusted (changed) at the same time. The high-voltage unit 9 transfers a voltage (re-transfer bias) having the same polarity as that of the toner based on the re-transfer condition set (changed) by the control unit 8 according to a signal (control signal) from the control unit 8. Apply to belt 14. As a result, the toner adhered to the transfer belt 14 is retransferred to the photoconductor 1. In this embodiment, the toner retransferred onto the photoconductor 1 is also removed from the photoconductor 1 by the cleaning device 7. Thus, the transfer belt 14 can be cleaned.
[0076]
The cleaning method of the transfer belt 14 using the toner retransfer method in the present embodiment has an advantage that the cleaning of the transfer belt 14 is more reliable in that the cleaning of the transfer belt 14 is repeatedly performed. are doing.
[0077]
[Embodiment 3]
A third embodiment of the present invention will be described with reference to FIGS. Further, for convenience of explanation, members having the same functions as those described in the first embodiment are given the same numbers, and descriptions thereof are omitted. In this embodiment, differences from the first and second embodiments will be mainly described.
[0078]
As shown in FIG. 5, the image forming apparatus according to the present embodiment includes a photoconductor 1, a charging device 2, an exposure device 3, a developing device 4, a transfer device 5, a first optical sensor 6, a cleaning device 7, A second optical sensor 18 (second detecting means) is further provided in addition to the unit 8, the high-pressure unit 9, and the sheet feeding roller pair 11.
[0079]
The second optical sensor 18 is located downstream of the cleaning device 7 and the developing device 4 in the rotational direction of the photoconductor 1 and upstream of the transfer device 5 in the rotational direction of the photoconductor 1. It is arranged in the position where it was done. Thereby, the second optical sensor 18 irradiates the photoconductor 1 with light, so that the toner image formed on the photoconductor 1 is transferred onto the photoconductor 1 before passing through the transfer device 5. At least one of the toner density (reflectance) of the formed toner image and the amount of toner attached to the photoconductor 1 before transfer, that is, the toner image before transfer formed on the photoconductor 1 At least one of the toner density and the amount of toner attached to the photoconductor 1 before transfer is detected. Also in this case, by using the optical sensor for detecting the toner concentration and the toner amount, the toner concentration and the toner amount can be optically detected, and the optical sensor is affected by environmental changes such as temperature and humidity. In addition, the toner concentration and the toner amount can be accurately and simply detected. As the second optical sensor 18, an optical sensor similar to the first optical sensor 6 can be used.
[0080]
According to the present embodiment, the first optical sensor 6 and the second optical sensor 18 allow the toner density (toner amount) on the photoconductor 1 before passing through the transfer device 5 and the photosensitive density after passing through the transfer device 5. It is possible to detect the toner concentration (toner amount) on the body 1.
[0081]
Therefore, by comparing the two toner concentrations (toner amounts), the toner concentration and / or amount of the toner adhered to the transfer belt 14 from the photoreceptor 1 can be estimated. The toner concentration of the toner adhered to the transfer belt 14 from the photoreceptor 1 is, for example, the following expression: “toner concentration detected by the second optical sensor 18−toner concentration detected by the first optical sensor 6 = adhered to the transfer belt 14” Can be predicted (calculated) from the “toner density”.
[0082]
Next, the step of removing the toner attached on the transfer belt 14 using the first optical sensor 6 and the second optical sensor 18 will be described in more detail.
[0083]
As shown in FIG. 6, the toner density of the toner image Ta formed on the photoconductor 1 is detected by the second optical sensor 18. When the toner image Ta passes through the transfer belt, a part of the toner of the toner image adheres to the transfer belt. The toner density on the photoreceptor 1 is reduced by a part of the toner adhering to the transfer belt 14, and the density is detected by the first optical sensor 6.
[0084]
The density of the toner attached to the transfer belt 14 is accurately predicted (calculated) by comparing the toner density detected by the second optical sensor 18 with the toner density detected by the first optical sensor 6. Can be. From this prediction result, the control unit 8 can determine (adjust) the application conditions (retransfer conditions) such as the application level of the retransfer bias applied to the transfer belt 14. The adjustment of the retransfer conditions in the control unit 8, that is, the control of the high-pressure unit 9 can be performed in the same manner as in the first embodiment. Then, in the same process as in the first embodiment, a controlled retransfer bias is applied to the transfer belt 14 to retransfer the toner on the transfer belt 14 to the photoconductor 1. Thereby, the toner on the transfer belt 14 can be removed.
[0085]
In the cleaning method of the transfer belt 14 using the toner retransfer method in the present embodiment, the toner density (toner amount) on the photoconductor 1 before and after the toner image on the photoconductor 1 passes through the transfer device 5 is detected. Therefore, the density (toner amount) of the toner adhered on the transfer belt 14 can be accurately predicted. Therefore, according to the present embodiment, the cleaning of the transfer belt 14 can be performed more reliably than in the first embodiment.
[0086]
The above-described methods for cleaning the transfer belt 14 according to the first to third embodiments can also be performed by combining the respective embodiments.
[0087]
In the first to third embodiments, an example in which a cylindrical photoconductor drum is used as the photoconductor 1 has been described. However, the present invention is not limited to this. For example, an endless photoconductor belt may be used. May be used.
[0088]
Further, in the first to third embodiments, the example in which the transfer belt is used as the transfer unit has been described, but the present invention is not limited to this, and for example, a transfer roller may be used.
[0089]
Further, in the first to third embodiments, an example in which an optical sensor is used as the first and second detection means has been described. However, the present invention is not limited to this, and other known sensors may be used. May be used.
[0090]
An image forming apparatus according to the present invention includes a transfer belt that transfers a toner image on a photoconductor to a transfer material, and a first belt that detects at least one of a density of a toner image formed on the photoconductor and a toner adhesion amount. And a voltage of the same polarity as the toner can be applied to the transfer belt to clean the toner adhered to the transfer belt, and based on a detection value from the first optical sensor, A configuration for controlling the cleaning operation of the transfer belt may be employed.
[0091]
【The invention's effect】
As described above, the image forming apparatus according to the present invention includes an image carrier on which a developer image is formed on a surface, and a transfer unit that transfers the developer image formed on the image carrier to a transfer material. Voltage applying means for applying a voltage of the same polarity as the developer to the transfer means to retransfer the developer adhered on the transfer means onto the image carrier; and First detecting means for detecting at least one of the density of the developer image adhered thereon and the amount of the developer, and a developer image for removing the developer adhered on the image carrier after transfer The present invention is configured to include an agent removing unit and an adjusting unit that adjusts a retransfer condition by the voltage applying unit based on a detection value of the first detecting unit.
[0092]
Therefore, according to the above configuration, the voltage (cleaning bias) can be applied to the transfer unit under conditions corresponding to the amount of the developer adhering to the transfer unit. This has an effect that the developing agent can be efficiently and reliably removed (cleaned).
[0093]
In the above-described image forming apparatus, the first detection unit may be a first optical sensor.
[0094]
According to the configuration, it is possible to optically detect the density of the developer image and the amount of the developer adhered on the image carrier after the transfer, and the density and the developer of the developer image can be detected. The effect is that the amount can be accurately and simply detected without being affected by environmental changes such as temperature and humidity.
[0095]
In the above-described image forming apparatus, the first detection unit may be provided downstream of the transfer unit in the rotation direction of the image carrier.
[0096]
According to the above configuration, after the developer on the image carrier passes through the transfer unit, the image carrier comes into contact with the transfer unit or the developer falls from the image carrier onto the transfer unit, so that the transfer is performed. This has the effect that the density or the amount of the developer attached to the means can be detected efficiently.
[0097]
Further, in the image forming apparatus according to the present invention, in the above-described image forming apparatus, the microscopic image before transfer formed on the image carrier at a position upstream of the transfer unit in the rotation direction of the image carrier. The image forming apparatus further includes a second detecting unit configured to detect at least one of a density of an image agent image and an amount of a developing agent attached to the image carrier before transfer. The amount of the developer adhering to the transfer unit may be predicted from the detected value and the detection value of the first detection unit, and the retransfer condition may be adjusted based on the prediction result.
[0098]
According to the above configuration, it is possible to detect the concentration and / or the amount of the developer before and after the developer on the image carrier passes through the transfer unit. By comparing the values, the amount of the developer adhered on the transfer means can be easily and accurately predicted. Therefore, according to the configuration, it is possible to more reliably and efficiently apply a voltage necessary for retransferring the developer adhered to the transfer unit to the image carrier, to the transfer unit. There is an effect that the developer adhered to the transfer unit can be efficiently and reliably removed (cleaned).
[0099]
In the above-described image forming apparatus, the second detection unit may be a second optical sensor.
[0100]
According to the above configuration, before the developer on the image carrier passes through the transfer unit, the density and the amount of the developer on the image carrier can be optically detected. The effect is obtained that the density of the developer image and the amount of the developer can be accurately and simply detected without being affected by environmental changes such as temperature and humidity.
[0101]
In the above-described image forming apparatus, the adjustment unit may adjust the retransfer condition so that the retransfer is repeated until a desired detection result is obtained by the first detection unit.
[0102]
According to the above configuration, the retransfer can be performed while confirming a change in the retransfer amount from the transfer unit to the image carrier, that is, a state in which the amount of toner attached to the transfer unit gradually decreases. Therefore, the developer remaining (adhering) on the transfer means can be surely removed by the retransfer, and the retransfer can be prevented from being repeated more than necessary. This has the effect that the toner adhering to the transfer belt can be re-transferred to the photoreceptor.
[0103]
In the above-described image forming apparatus, the transfer unit includes an endless transfer belt or a transfer roller, and the first detection unit detects the first detection from a contact point between the image carrier and the transfer unit. Means is provided such that the circumference in the rotation direction of the image carrier is shorter than the circumference of the transfer means up to a point at which the density or the amount of the developer is detected on the image carrier. May be adopted.
[0104]
According to the above configuration, the detection of the density and / or the amount of the developer on the image carrier can be performed immediately after the developer on the image carrier passes the transfer unit. Therefore, the adjustment of the retransfer conditions can be performed promptly. Therefore, there is an effect that the retransfer can be performed more efficiently.
[0105]
In the above-described image forming apparatus, the adjusting unit may adjust at least one of a voltage value applied by the voltage applying unit to the transfer unit and a voltage application time as the retransfer condition.
[0106]
According to the above configuration, a voltage (cleaning bias) according to the amount of the developer adhered to the transfer unit can be applied to the transfer unit. Can be efficiently and reliably removed (cleaned).
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically showing a configuration of a main part of an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a time chart illustrating a relationship between a retransfer time and a retransfer bias.
FIG. 3 is a sectional view schematically showing a configuration of a main part of an image forming apparatus according to another embodiment of the present invention.
FIG. 4 is a schematic diagram illustrating a change in density every time a toner image on a photosensitive member is retransferred.
FIG. 5 is a sectional view schematically showing a configuration of a main part of an image forming apparatus according to still another embodiment of the invention.
FIG. 6 is a schematic diagram illustrating a change in the density of the developer image before and after the developer image on the photoconductor passes through a transfer belt.
FIG. 7 is a sectional view schematically showing a configuration of a main part of a conventional image forming apparatus.
[Explanation of symbols]
1 Photoconductor (image carrier)
2 Charging device
3 Exposure equipment
4 Developing device
5 Transfer device
6. First optical sensor (first detecting means)
7. Cleaning device (developing agent removing means)
8 control part (adjustment means)
9 High voltage unit (voltage applying means)
10 Transfer material
11 Paper feed roller pair
12 Charging roller
13a Development tank
13b developing roller
14. Transfer belt (transfer means)
15a Cleaning roller
15b Cleaning blade
16 Laser light
17a Support roller
17b Support roller
18. Second optical sensor (second detecting means)

Claims (8)

An image carrier on which a developer image is formed,
Transfer means for transferring the developer image formed on the image carrier to a transfer material,
Voltage applying means for applying a voltage of the same polarity as the developer to the transfer means and retransferring the developer adhered on the transfer means onto the image carrier;
First detection means for detecting at least one of the density of the developer image and the developer amount attached to the image carrier after the transfer,
A developer removing means for removing the developer adhering on the image carrier after the transfer, and an adjustment for adjusting the retransfer condition by the voltage applying means based on a detection value of the first detecting means. And an image forming apparatus. The image forming apparatus according to claim 1, wherein the first detection unit is a first optical sensor. The image forming apparatus according to claim 1, wherein the first detection unit is provided downstream of the transfer unit in a rotation direction of the image carrier. On the upstream side in the rotation direction of the image carrier with respect to the transfer means, the density of the developer image formed on the image carrier before transfer and the density of the developer image adhered on the image carrier before transfer. Further comprising a second detecting means for detecting at least one of the developer amount of
The adjusting means predicts the amount of the developer adhering to the transfer means from the detection value of the second detection means and the detection value of the first detection means, and based on the prediction result, 4. The image forming apparatus according to claim 3, wherein a transfer condition is adjusted. The image forming apparatus according to claim 4, wherein the second detection unit is a second optical sensor. 4. The apparatus according to claim 1, wherein the adjusting unit adjusts the retransfer condition so that the retransfer is repeated until a desired detection result is obtained by the first detecting unit. The image forming apparatus as described in the above. The transfer means is constituted by an endless transfer belt or a transfer roller,
The first detecting means is provided between a contact point between the image carrier and the transfer means to a point at which the first detecting means detects the density or the amount of the developer image on the image carrier. The image forming apparatus according to claim 1, wherein a circumference of the image carrier in a rotation direction is shorter than a circumference of the transfer unit. The apparatus according to claim 1, wherein the adjustment unit adjusts at least one of a voltage value applied to the transfer unit and a voltage application time by the voltage application unit as the re-transfer condition. 9. The image forming apparatus as described in the above.

Images