JP2018136530A - Image forming device - Google Patents

Abstract

An object of the present invention is to suppress adverse effects on images caused by injection charging. A photosensitive drum for carrying a developer, a charging roller that contacts the photosensitive drum with a speed difference and charges the photosensitive drum, and a developer image on the photosensitive drum. Roller 5, which transfers developer onto the recording material R, a developer that supplies developer to the photoconductor drum 1, and collects the developer remaining on the photoconductor drum 1 after transfer, and a developing roller 41, which transfers the photoconductor drum 1 from the charging roller 2. Detecting means 9 for detecting information on injection charging in which electric charges are injected into the photosensitive drum 1, and determining the amount of developer (fogging developer) to be supplied to the non-image forming portion of the photosensitive drum 1 during image formation based on the information. An image forming apparatus 100 comprising: a controller 8 for controlling an image forming apparatus according to information detected by a detecting unit while suppressing an amount of developer collected in a developing sleeve 41; During, and controlling the amount of fog developer. [Selection diagram] Fig. 1

Description

  The present invention relates to an image of a copying machine, a printer, or the like that performs image formation by applying an image forming process including a step of charging an image carrier such as an electrophotographic photosensitive member or an electrostatic recording dielectric to a predetermined polarity or potential. The present invention relates to a forming apparatus.

  Conventionally, in an image forming apparatus using an electrophotographic system, a process cartridge system is often used. In this device, a rotatable photosensitive member and a process means acting on the photosensitive member are integrally formed into a cartridge so that it can be attached to and detached from the main body of the image forming apparatus.

  According to this process cartridge system, the maintenance of the apparatus can be performed by the user himself / herself without depending on the service person, so that the operability can be remarkably improved. Therefore, this process cartridge system is widely used in electrophotographic image forming apparatuses.

  Image forming apparatuses such as laser beam printers and copiers that employ an electrophotographic method first irradiate light (laser light, etc.) corresponding to image information onto a uniformly charged photoreceptor by a charging roller. An electrostatic latent image is formed. Thereafter, a developer (toner) is supplied to the electrostatic latent image by a developing device so as to be visualized as a developer image (toner image). Further, by transferring an image from the photosensitive member to a recording material such as paper, an image is formed on the recording material and output.

  In such a transfer type image forming apparatus, there is also an apparatus in which a transfer residual developer remaining on a photoconductor after transfer is removed from the surface of the photoconductor by a cleaner (cleaning device) to be a waste developer. It is desirable that this waste developer does not come out from the viewpoint of environmental protection. Therefore, there is an apparatus configuration in which the cleaner is eliminated, and the untransferred developer on the photosensitive member after transfer is removed from the photosensitive member by “development simultaneous cleaning” by the developing device, and collected and reused in the developing device. That is, the image forming apparatus is a developer recycling process.

  The simultaneous development cleaning is a method in which the developer remaining on the photosensitive member after transfer is recovered by a residual toner recovery bias at the time of development after the next step. That is, the fog removal potential difference Vback, which is the potential difference between the DC voltage applied to the developing device and the surface potential of the photoreceptor, is used. According to this method, the untransferred developer is collected in the developing device and reused after the next step. Therefore, it is possible to eliminate the waste developer and reduce troubles in maintenance. In addition, a so-called cleanerless image forming apparatus in which a transfer residual developer is collected by a developing device has a great space advantage. That is, since there is no need to provide a cleaning device, there is an advantage that the image forming apparatus can be greatly reduced in size.

  By the way, in an image recording apparatus using a contact-type charging member (charging roller), the charging member that contacts the image carrier may pick up residual developer on the surface of the image carrier and adhere to the surface of the charging member. For this reason, there is a possibility that the charging performance is deteriorated due to the repeated printing (durability) and the amount of the developer attached to the charging member.

  In particular, in a cleanerless image forming apparatus, when image formation is performed, the transfer residual developer is likely to enter the charging nip portion, which is the contact portion between the contact charging member and the image carrier, and the surface of the contact charging member. Developer adheres. When the developer is present on the contact-type charging member, the charged potential of the image carrier varies depending on the amount of developer attached. This phenomenon may appear as a change in halftone image density that is a halftone.

JP 2016-14863 A

  In order to solve such a problem, a circumferential speed difference is provided between the contact charging member and the photosensitive member, the developer is charged by friction between the charging member and the photosensitive member, and the developer adhered to the surface of the contact charging member is exposed to light. A configuration to return to the body has been proposed. On the other hand, in the configuration in which the contact charging member and the photosensitive member are provided with a peripheral speed difference, charges are injected on the surface of the photosensitive member in the nip with the contact charging member separately from charging due to discharge under high humidity. May cause charging. Such injection charging behavior is not only the problem that the photoreceptor surface potential fluctuates due to fluctuations in the humidity environment, but also the injection quantity varies depending on the amount of toner interposed between the photoreceptor and the charging roller. May cause harmful effects.

  Further, it is known as a property of the injection charging component that when the amount of the fog developer on the photoconductor is increased, the contact area between the photoconductor and the charging member is reduced, so that the injection charge amount is decreased. Therefore, in a system in which such injection charging can occur, it may be possible to avoid the adverse effects caused by injection charging by controlling the amount of fog developer supplied to the white background. However, as described above, in the image forming apparatus that simultaneously collects development, the fog developer is also collected by the development apparatus and reused. Therefore, when the fog developer amount increases, there is a problem that the deterioration of the developer proceeds. There is.

  It has been a problem to achieve both the adverse effects of the image due to such injection charging and the suppression of the deterioration of the developer.

In order to achieve the above object, the present invention provides:
An image carrier for carrying a developer;
A charging member that moves in the same direction as the image carrier at the contact portion, contacts the image carrier with a speed difference, and charges the image carrier;
Transfer means for transferring the developer image on the image carrier to a transfer target;
A developer carrier for supplying a developer to the image carrier and recovering the developer remaining on the image carrier after the transfer;
Detecting means for detecting information relating to injection charging in which electric charge is injected from the charging member into the image carrier;
An image forming apparatus comprising: a control unit that controls an amount of developer supplied to a non-image forming portion of the image carrier based on the information at the time of image formation;
The control means controls the amount of developer supplied to the non-image forming portion of the image carrier during image formation according to the information detected by the detection means.

  According to the present invention, in a configuration in which a speed difference is provided between the image carrier and the charging member, it is possible to suppress image deterioration due to injection charging while suppressing deterioration of the developer.

The figure which shows the injection charging which becomes a subject by this invention 1 illustrates an image forming apparatus according to a first exemplary embodiment. FIG. 3 is an enlarged view of a part of the image forming apparatus according to the first exemplary embodiment. A diagram showing the relationship between the amount of fog toner and injection charging The figure showing the relationship between the fog developer amount and the fog removal potential difference Vback

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be exemplarily described in detail with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be appropriately changed according to the configuration of the apparatus to which the invention is applied and various conditions. That is, it is not intended to limit the scope of the present invention to the following embodiments.

(Image forming device and cleanerless image forming process)
FIG. 2 is a diagram showing a schematic configuration of a printer 100 as an embodiment of the image forming apparatus according to the present invention. FIG. 6 is a cross-sectional view when viewed along the axial direction of the image carrier in a normal installation state. The top and bottom on the drawing are the vertical direction, and the left and right are the horizontal direction.

The image forming operation will be described below with reference to FIGS.
When the image forming operation is started, the photosensitive drum 1 as an image carrier is rotated by a drive motor that drives the photosensitive drum 1 in the direction of the arrow in FIG. 2 at a peripheral speed of 150 mm / sec.
A charging roller 2 is used as a charging member that charges the surface of the photosensitive drum 1. When the image forming operation described below is performed, a process for stabilizing the charging potential is already performed. A voltage (Vpri) of −1500 V is applied to the charging roller 2 at a predetermined timing from a charging power source 2 a (FIG. 3), whereby the photosensitive member is uniformly charged at −800 V.

  A laser exposure unit 3 as an exposure device that exposes the charged photosensitive drum 1 exposes the photosensitive drum 1 using a laser beam in accordance with image data. The laser beam repeats exposure in the main scanning direction (photosensitive member rotation axis direction) and also performs exposure in the sub-scanning direction (photosensitive member surface movement direction) to form an electrostatic latent image.

  The developing device 4 as the developing means is detachably disposed on the main body of the image forming apparatus, and can be replaced with another new developing device 4 after the lifetime. The developing device 4 can develop the electrostatic latent image formed on the photosensitive member with a developing sleeve to which a developing bias (Vdc) -500 V is applied from the developing bias power source 4a (FIG. 3).

  Here, the developing device 4 will be described. The developing sleeve 41 is rotatably supported by the developing device 4 and is driven to rotate with respect to the photosensitive drum 1 at a peripheral speed of 140%. The developing sleeve 41 is provided with a conductive elastic rubber layer around a hollow aluminum tube. The surface of the conductive elastic rubber layer is a rough surface having a surface roughness Ra of 1.0 μm to 2.0 μm for conveying developer. Is provided. In the developing sleeve 41, a magnet roller 43, which is a magnet, is fixed and arranged. The magnetic one-component developer (negative charging characteristic) T as the developer in the developing device 4 is stirred by the stirring member 44 in the developing container, and this stirring causes the magnetic force of the magnet roller 43 in the developing device 4. It is supplied to the surface of the developing sleeve 41. The developer T supplied to the surface of the developing sleeve 41 passes through the developing blade 42 which is a regulating member that regulates the thickness of the developer layer, and is negatively charged by uniform thinning and frictional charging. A negative bias (Vbld) −800V is applied to the developing blade 42 with respect to the developing sleeve 41, and a potential difference (ΔVbld) with respect to the developing roller is −300V. Thereafter, the toner is conveyed to a developing position where it contacts the photosensitive drum 1, and the electrostatic latent image is developed.

The developer image visualized on the photosensitive drum 1 (on the image carrier) is further sent to a contact portion with a transfer roller 5 as a transfer means, and is recorded as a transfer target conveyed at the same timing. Transferred onto the material R. A transfer bias is applied between the transfer roller 5 and the photosensitive drum 1 by a power source 5a (FIG. 3). The transfer material is not limited to the recording material described above, and an intermediate transfer material such as an endless transfer belt can also be employed.

  The recording material R to which the developer image has been transferred is sent to the fixing device 7. In the fixing device 7, heat and pressure are applied to the recording material R, and the transferred developer image is fixed to the recording material R.

  The controller 8 is a control unit that controls the operation of the image forming apparatus 100, controls transmission / reception of various electrical information signals, drive timing, and the like, and controls predetermined image forming sequence control and the like.

  On the other hand, after transfer, the untransferred developer remaining on the photosensitive drum 1 without being transferred is conveyed toward the charging roller 2. At this time, a voltage (−1500 V) for charging the photosensitive drum 1 is applied to the charging roller 2. When the transfer residual developer is conveyed to the vicinity of the nip portion C, most of the transfer residual developer together with the photosensitive drum 1 is negatively charged by the discharge from the charging roller 2. That is, most of the untransferred developer is forcibly negatively charged, so that the developer passes through the charging roller 2 without being attached to the charging roller 2 by the electric field between the charging roller 2 and the negatively charged photosensitive drum 1. To do. As described above, most of the developer is negatively charged by the discharge from the charging roller 2, but there remains a developer that cannot be slightly negative, and this developer adheres to the charging roller 2. Sometimes. In order to alleviate such adhesion of the developer, the charging roller 2 is rotated in the same direction with respect to the photosensitive drum 1 by a gear at a peripheral speed of 110%, and the peripheral speed is made higher than that of the photosensitive drum 1. Yes. That is, the charging roller 2 is configured to contact the photosensitive drum 1 with a speed difference. At this time, the surface of the photosensitive drum 1 and the surface of the charging roller 2 rotate in the same direction at the nip portion C which is a contact portion. In this way, the developer is negatively charged by friction between the charging roller 2 and the photosensitive drum 1, and the developer is returned to the photosensitive drum 1 by an electric field. The peripheral speed of the charging roller 2 is preferably 110% to 140% with respect to the peripheral speed of the photosensitive drum 1. Thus, normally, the developer adhering to the charging roller 2 is reduced by the negative charging of the developer by the discharge from the charging roller 2 and the negative charging by the friction by the difference in peripheral speed.

  The untransferred developer that has passed through the charging roller 2 is then transported to the development position as the photosensitive drum 1 rotates. In this state, in the non-image forming portion, the potential difference (Vback) −300V between the photosensitive drum 1 surface dark portion potential (Vd) −800V and the developing bias (Vdc) −500V. Therefore, the transfer residual developer adheres to the developing sleeve 41 and is collected in the developing device 4. This is called simultaneous development cleaning. Here, the developing sleeve 41 constitutes a developer carrying member that supplies the developer to the photosensitive drum 1 and collects the developer remaining on the photosensitive drum 1 after the transfer. In the image forming portion, the residual transfer developer does not adhere to the developing sleeve 41 due to the electric field of the photosensitive drum 1 surface bright portion potential (Vl) -100V and the developing bias (Vdc) -500V. However, since this portion is originally a portion where image formation is performed, it remains on the photosensitive drum 1 as it is and is then transferred. An image forming operation is executed by repeating such steps.

  In the configuration in which the charging roller 2 and the photosensitive drum 1 are provided with peripheral speeds, as shown in FIG. 1, the photosensitive drum 1 surface dark portion potential is not only due to discharge, but also at the surface of the photosensitive drum 1, particularly under high humidity. Charge may be generated by injecting electric charge into the substrate. Such injection charging behavior is not only due to the problem that the surface potential of the photosensitive drum 1 fluctuates due to fluctuations in the humidity environment, but also varies depending on the amount of developer interposed between the photosensitive drum 1 and the charging roller 2. In some cases, such as ghost images may cause image problems.

(Configuration of this embodiment)
Therefore, in this embodiment, the developing bias is increased so as to increase the amount of fog developer that is a developer supplied to the non-image forming portion (white background) of the photosensitive drum 1 under the temperature and humidity conditions where the injection charging can occur. It is characterized by controlling. Therefore, in this embodiment, it is necessary to detect the temperature and humidity in the vicinity of the charging device as environmental information in the vicinity of the image carrier, and the temperature and humidity sensor 9 is mounted on the apparatus main body. The humidity is not limited to relative humidity, and absolute humidity or absolute water content can also be adopted. In the case of the configuration of the present embodiment described above, an injection charging component was generated in a high temperature and high humidity environment as shown in Table 1.

  As described above, it is known as a characteristic of the injection charge component that the injection charge amount decreases as the fog developer amount increases. In this embodiment, the relationship between the charged injection component and the fog toner amount is as shown in FIG. Therefore, for example, the injection charging component 30V in an environment of 40 degrees and 95% can be eliminated if the fog developer amount on the photosensitive drum 1 is 20%. On the other hand, as shown in FIG. 5, the fog developer amount has a large correlation with the fog removal potential difference Vback. In this embodiment, the amount of the fog developer on the photosensitive drum 1 at the time of normal image formation described above was about 2% when Vback at the time of normal image formation was −300 V in all temperature and humidity regions. Therefore, the developing bias (Vdc) applied to the developing sleeve 41 is changed from -500V to -400V to Δ100V. The difference Vback between the photosensitive drum 1 surface dark portion potential (Vd) −800V and the developing bias (Vdc) −400V is −400V. As a result, the fog developer increased to 20%, and the charged injection component in an environment of a temperature of 40 degrees and a humidity of 95% disappeared. Therefore, it is conceivable to apply the developing bias to the entire environment. However, if the amount of fog developer is increased, the developer may be deteriorated in the image forming apparatus for simultaneous development recovery. Therefore, it is desirable to control the amount of the fog developer as small as possible.

Therefore, in the case of this example, in order to eliminate the injection charging component shown in Table 1, the bias control shown in Table 2 was performed. That is, control is performed to change the developing bias according to the temperature and humidity detected by the temperature / humidity sensor 9 while suppressing the amount of developer collected in the developing device 4 by adhering to the developing sleeve 41. ing. Specifically, when both the temperature and humidity detected by the temperature / humidity sensor 9 increase, the developing bias is changed so that the amount of fog developer increases.

  In this embodiment, a memory 45a as a storage means is provided in the apparatus main body, and a memory 45b is provided in the charging device, respectively, and writing and reading are possible at any time. The nonvolatile memory can store the stored data even when the main body power is turned off. In the present embodiment, the development bias control value at the temperature and humidity shown in Table 2 is stored as information in the nonvolatile memory 45b, and the bias information is stored in the main body memory 45a when the main body power is on or in standby. That is, the first control information relating the temperature and humidity to the development bias is stored in the memory 45b as the first storage means. Furthermore, a temperature / humidity sensor for reading the temperature and humidity around the charging device is provided in the image forming apparatus main body. With these two pieces of information, it is possible to control the developing bias required to eliminate the injection charge amount of the charging device. In this embodiment, the development bias is controlled every time when a print signal is sent to the apparatus main body, and the development bias shown in Table 2 is determined in light of the temperature and humidity information at that time.

  As described above, the development bias can be changed to increase the fog developer from the information of the temperature / humidity sensor installed in the main body of the image forming apparatus and the value of the charged injection component under each environment stored in advance in the memory. This is a feature of the present embodiment. By performing the control according to the present embodiment, injection charging under a necessary environment can be optimally eliminated, and as a result, image defects due to injection charging can be suppressed.

(Modification)
In this embodiment, the optimum amount of fog developer for eliminating the charged injection component is controlled by changing the developing bias. However, the means is not limited as long as the amount of fog developer can be controlled.

  For example, if the absolute value of the difference (regulation member bias) ΔVbld applied to the developing blade 42 and the developing sleeve 41 is reduced, the fog developer can be increased. Also by this, the injection charging component can be controlled, and in the case of this modification, the above-described Table 2 can be changed as shown in Table 3 below. That is, by changing the potential ΔVbld between the developing sleeve 41 and the developing blade 42, the amount of fog developer can be controlled.

Also in this modification, the second control information relating the temperature and humidity and the potential ΔVbld between the developing sleeve 41 and the developing blade 42 may be stored in the memory 45b as the second storage unit. Good.

In this embodiment, the charged injection component is measured and controlled.
As shown in FIG. 1, the charged injection component can be measured by applying the bias (Vpri) applied to the charging roller 2 to the discharge start voltage (Vth), in this embodiment 600V. As a measuring method, in addition to measuring the surface potential of the photosensitive drum using a surface potential meter installed in the apparatus main body, there is a method of measuring a current value flowing through the charging roller using a galvanometer. In this example, a surface electrometer installed in the main body of the apparatus was used, and a time for measurement during the pre-rotation was provided. That is, the development bias is changed according to the injected charging component detected by the surface potential meter or the galvanometer while suppressing the amount of the developer collected in the developing device 4 by adhering to the developing sleeve 41. Control is in progress. Specifically, the developing bias is changed so that the amount of fog developer increases when the injection charge component increases. Further, as shown in the modification of the first embodiment, the amount of fog developer may be controlled by changing the potential ΔVbld between the developing sleeve 41 and the developing blade 42.

In this case, unlike the first embodiment, it is not necessary to mount the temperature / humidity sensor 9 on the image forming apparatus main body. In this embodiment, the development bias control data shown in Table 4 is stored in the memory 45a as the storage means, and the feedback amount to the development bias is directly controlled from the measured injection charge amount. That is, the third control information relating the injection charging component (injection charge amount) and the developing bias is stored in the memory 45a as the third storage unit. Further, as shown in the modification of the first embodiment, the fourth control information relating the injection charging component (injection charge amount) and the potential ΔVbld between the developing sleeve 41 and the developing blade 42 is the fourth control information. You may make it memorize | store in the memory 45a as a memory | storage means.

DESCRIPTION OF SYMBOLS 1 ... Photosensitive drum, 2 ... Charging roller, 5 ... Transfer roller, 8 ... Controller, 9 ... Temperature / humidity sensor, 41 ... Developing sleeve, 42 ... Developing blade, 45a ... Memory, 45b ... Memory, R ... Recording material

Claims (14)

An image carrier for carrying a developer;
A charging member that moves in the same direction as the image carrier at the contact portion, contacts the image carrier with a speed difference, and charges the image carrier;
Transfer means for transferring the developer image on the image carrier to a transfer target;
A developer carrier for supplying a developer to the image carrier and recovering the developer remaining on the image carrier after the transfer;
Detecting means for detecting information relating to injection charging in which electric charge is injected from the charging member into the image carrier;
An image forming apparatus comprising: a control unit that controls an amount of developer supplied to a non-image forming portion of the image carrier based on the information at the time of image formation;
The image forming apparatus characterized in that the control means controls the amount of developer supplied to the non-image forming portion of the image carrier during image formation according to the information detected by the detecting means. The information detected by the detection means is environmental information including absolute humidity, relative humidity or absolute moisture amount near the image carrier, and temperature.
The control means supplies the non-image forming portion of the image carrier at the time of image formation when the absolute humidity, the relative humidity and / or the absolute water content near the image carrier and the temperature both increase. The image forming apparatus according to claim 1, wherein the amount of developer to be controlled is controlled to increase.   The control means determines the development bias to be applied to the developer carrier when the absolute humidity, the relative humidity or the absolute water content near the image carrier and / or the temperature both increase. The image forming apparatus according to claim 2, wherein the absolute value is changed to be small. First storage means for storing first control information relating information detected by the detection means and a developing bias applied to the developer carrier;
The image forming apparatus according to claim 1, wherein the control unit controls the developing bias based on first control information stored in the first storage unit. A regulating member for regulating the developer carried on the developer carrying body;
Applying a regulating member bias for the developer carrier to the regulating member,
When the absolute humidity, the relative humidity or the absolute water content near the image carrier and the temperature both increase, the control means sets the regulating member bias to the regulating member bias. The image forming apparatus according to claim 2, wherein the absolute value is changed to be small. Second storage means for storing second control information relating information detected by the detection means and the restriction member bias;
6. The control unit according to claim 5, wherein the control unit changes a potential between the developer carrying member and the regulating member based on second control information stored in the second storage unit. Image forming apparatus.   The image forming apparatus according to claim 1, wherein the information detected by the detection unit is an injection charging component of a potential of the image carrier. The control means controls the amount of developer supplied to a non-image forming portion of the image carrier to be increased during image formation when the injection charge component increases. 8. The image forming apparatus according to 7.   9. The control unit according to claim 8, wherein when the injection charging component increases, the developing bias applied to the developer carrying member is changed so that the absolute value of the developing bias becomes small. Image forming apparatus. Third storage means for storing third control information relating the injection charging component and the development bias;
The image forming apparatus according to claim 9, wherein the control unit controls the developing bias based on third control information stored in the third storage unit. A regulating member for regulating the developer carried on the developer carrying body;
Applying a regulating member bias for the developer carrier to the regulating member,
The image forming apparatus according to claim 8, wherein the control unit changes the regulating member bias so that an absolute value of the regulating member bias becomes small when the injection charging component increases. Fourth storage means for storing fourth control information relating the injection charging component and the regulating member bias;
The image forming apparatus according to claim 11, wherein the control unit controls the regulating member bias based on fourth control information stored in the fourth storage unit.   The image forming apparatus according to claim 1, wherein the transfer target is a recording material. The image forming apparatus according to claim 1, wherein the transfer target is an intermediate transfer member.

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