Image forming apparatus

Abstract

This reduces or prevents the occurrence of abnormal images in which white areas appear as vertical streaks. [Solution] An image forming apparatus comprising: a developing device that thins the developer in a developing unit (12) supplied to a developer carrier (51) on the developer carrier (51) using a layer thickness regulating member (53), and then develops the latent image on a latent image carrier in a developing region using the thinned developer; and a notification means (91) that notifies prompt information to encourage the user to replenish the developer used in the developing unit (12), wherein the notification means (91) notifies when the height of the developer water level is higher than a first height which is the height of the contact point (A) of the layer thickness regulating member (53) with the developer carrier (51).

Description

Technical Field

[0001] The present invention relates to an image forming apparatus.

Background Art

[0002] Conventionally, there has been known an image forming apparatus including a developing device that thins a developer in a developing unit supplied to a developer carrier by a layer thickness regulating member and then develops a latent image on a latent image carrier in a developing area with the thinned developer, and notification means for notifying urging information that prompts a user's replenishment operation of the developer used in the developing device with respect to the developing device.

[0003] For example, in Patent Document 1, in such a developing device, when an index correlated with a ratio of the amount of paper dust collected by a developer carrier mixed in the developer in the developing container to the amount of the developer in the developing container does not exceed a preset first threshold value, replenishment information (urging information) is notified based on information regarding the amount of the developer in the developing container or information regarding the consumption amount of the developer due to development.

[0004] According to this, it is said that it is possible to reduce a fogged image caused by a decrease in the toner charge amount due to paper dust, which occurs when paper dust accumulates in the developing container and the remaining amount of toner in the developing container is small.

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present inventors have confirmed that when using a developing device in which paper dust is mixed into a developing container, an abnormal image with vertical streaks of white streaks may occur. Patent Document 1 does not describe such an abnormal image, and there is a possibility that the abnormal image may occur in the device described in Patent Document 1.

Means for Solving the Problems

[0006] To solve the above-mentioned problems, the present invention provides an image forming apparatus comprising: a developing apparatus that thins the developer in a developing unit supplied to a developer carrier on the developer carrier using a layer thickness regulating member, and then develops a latent image on a latent image carrier in a developing region using the thinned developer; and a notification means that notifies prompt information to encourage the user to replenish the developer used in the developing unit, wherein the notification means notifies when the height of the developer water level is higher than a first height which is the height of the contact point of the layer thickness regulating member with the developer carrier. [Effects of the Invention]

[0007] According to the present invention, it is possible to reduce or prevent the occurrence of abnormal images in which white areas appear in the shape of vertical streaks. [Brief explanation of the drawing]

[0008] [Figure 1] A schematic diagram of a printer, which is an image forming apparatus according to this embodiment. [Figure 2] A cross-sectional view showing the schematic configuration of the developing apparatus provided in the image forming apparatus. [Figure 3] A cross-sectional view showing the height relationship of the detection point A in the regulating blade contact area of ​​the developing device. [Figure 4] A cross-sectional view showing the toner transport mechanism installed within the developing device. [Figure 5] A cross-sectional view showing the toner stirring mechanism installed within the developing apparatus. [Figure 6] A schematic diagram of the developing apparatus shown in Figure 5, viewed from above. [Figure 7] A diagram illustrating a cleanerless system. [Figure 8] Diagram illustrating the state after Figure 7. [Figure 9] Diagram illustrating the state after Figure 8. [Figure 10] An explanatory diagram of the state after Figure 9. [Figure 11] Diagram illustrating the occurrence of a malfunction. [Modes for carrying out the invention]

[0009] The following describes embodiments of the present invention applied to a so-called cleanerless electrophotographic image forming apparatus, in which there is a high possibility of paper dust entering the developing unit. First, a general description of a so-called cleanerless electrophotographic image forming apparatus will be given.

[0010] In electrophotographic image forming apparatuses, a photoreceptor is charged using a charging component such as a charging roller, toner is supplied to the photoreceptor by a developing mechanism, and the toner on the photoreceptor is transferred to the recording material. After the transfer, any remaining toner adhering to the photoreceptor was cleaned off using a cleaning mechanism such as a cleaning blade. In recent years, from the perspective of miniaturizing the apparatus, a so-called cleanerless system has been proposed, which does not have a dedicated cleaning mechanism for cleaning the photoreceptor.

[0011] In cleanerless image forming machines, residual toner remaining on the photoreceptor after transfer is typically recovered in a developing unit. Because this cleanerless system recovers and reuses the residual toner, waste toner is reduced. This simplifies user maintenance and eliminates the need for a waste toner container, thus reducing waste.

[0012] However, in cleanerless image forming machines, abnormal images sometimes occur with vertical streaks of white. Upon investigating the cause, the following was discovered.

[0013] In image forming apparatuses employing a cleanerless system, paper dust transferred from the surface of the recording paper in the transfer section adheres to the photoreceptor. This paper dust, like the toner, is collected into the developing unit via the developing roller (developer carrier). Inside the developing unit, a regulating blade (layer thickness regulating member) is provided in contact with the developing roller to form a thin layer of toner. If paper dust enters this contact area (hereinafter referred to as the regulating blade contact area), it may become trapped between the developing roller and the regulating blade and become impossible to remove.

[0014] The toner on the developing roller is in contact with the toner in the developing unit in the area until it reaches the regulating blade contact portion by the rotation of the developing roller, and is mixed by the disturbing effect due to the friction between the toners. Therefore, since paper dust is also mixed in the toner and diffused into the developing unit, most of the paper dust does not enter the regulating blade contact portion.

[0015] FIG. 11(a) is a schematic diagram showing the state of diffusion of this paper dust. Reference numeral 51 denotes a developing roller, reference numeral 53 denotes a regulating blade, reference numeral A denotes a regulating blade contact portion, and reference numeral T denotes a toner contact surface. In the illustrated example, a supply roller 52 for supplying toner to the developing roller 51 is also provided. In a state where the toner contact surface T is at a position higher than the regulating blade contact portion A, a flow F of toner in the developing unit is generated by the rotation of the supply roller 52 and the developing roller 51, and by disturbing the toner held on the surface of the developing roller 51, the paper dust P is卷入 and carried away, and diffused into the hopper.

[0016] However, as printing continues, the toner in the developing unit decreases because the toner is consumed. And when the toner contact surface becomes lower than the regulating blade contact portion, the above-described disturbing effect does not occur, so that the paper dust cannot be diffused into the developing unit.

[0017] FIG. 11(b) shows the state when the toner contact surface T is at a position lower than the regulating blade contact portion A. Since the flow of toner in the hopper cannot be generated, the paper dust P remains included in the toner held on the surface of the developing roller 51 and enters the regulating blade contact portion A.

[0018] As described above, the paper dust is carried to the regulating blade contact portion, and since the paper dust is sandwiched between the developing roller and the regulating blade to inhibit the formation of a thin toner layer, vertical streak image defects occur. It has been found that vertical streak image defects occur due to the above reasons.

[0019] Particularly, this is likely to occur in a developing device using a sequential toner supply method. That is, in a stationary type developing device that supplies toner from a detachably attached toner cartridge (replenishing developer container) into the developing unit, and when the toner cartridge becomes empty, replaces the toner cartridge with a new one and repeats the toner supply again, the paper dust existing in the developing unit continues to increase, and the probability of occurrence of vertical streak-like image defects becomes extremely high.

[0020] Once this image defect occurs, the paper dust sandwiched between the regulating blade contact portions cannot be removed, so even if the toner cartridge is replaced, the image defect cannot be cured.

[0021] The image forming apparatus of the present embodiment adopts the following configuration in an image forming apparatus adopting a cleanerless method in order to prevent the paper dust mixed in the developing unit from entering the regulating blade contact portion and suppressing the occurrence of vertical streak-like image defects.

[0022] That is, in a developing device provided in an image forming apparatus adopting a cleanerless method, when the toner level T in the developing container is higher than the regulating blade contact portion A during the process of the toner in the developing container decreasing, additional toner is supplied from the toner cartridge through the toner supply port, or when the toner cartridge is empty, a cartridge replacement is notified. According to this, since the toner level T in the developing container does not become lower than the position of the regulating blade contact portion A, the intrusion of paper dust into the regulating blade contact portion A can be prevented.

[0023] FIG. 1 is a schematic configuration diagram of a printer which is an image forming apparatus according to an embodiment. In FIG. 1, this image forming apparatus includes a paper feeding unit 1, a registration roller pair 2, a photosensitive drum 3 as an image carrier, a transfer roller 4, a fixing device 5, and the like. The paper feeding unit 1 includes a paper feeding tray 6 that houses recording paper 101 as a recording material, and a paper feeding roller 7 and the like that separate and send out the recording paper 101 housed in the paper feeding tray 6 one by one. The recording paper 101 sent out by the paper feeding roller 7 is once stopped by the registration roller pair 2 and sent to the transfer area N3 at a predetermined timing.

[0024] Around the photoreceptor drum 3, in the order of the rotational direction indicated by the arrows, are a charging roller 11 as a charging means, a developing device 12 equipped with a developing roller 51, and a transfer roller 4. The developing device 12 is equipped with a removable toner cartridge 13 for storing toner as a developer. Between the charging roller 11 and the developing device 12, exposure light L is irradiated from the exposure device 8 onto the surface of the photoreceptor drum 3, causing it to be scanned. The developing device 12 itself is a developing container; therefore, when referring to the developing device, it means the developing container.

[0025] When the photoreceptor drum 3 begins to rotate, a charging bias voltage is applied to the charging roller 11, uniformly charging the photoreceptor surface in the charging region N1. Based on the image information, exposure light L is irradiated onto the surface of the photoreceptor drum 3 from the exposure device 8, and an electrostatic latent image is formed by de-staticizing the portion of the photoreceptor surface corresponding to the image to be created. This electrostatic latent image moves to the developing region N2 as the photoreceptor drum 3 rotates, and at this time, a developing bias voltage is applied to the developing roller 51 provided in the developing device 12.

[0026] In the developing region N2, the negatively charged toner held on the developing roller is supplied from the developing roller 51 to the photoreceptor drum 3 according to the potential difference between the potential of the electrostatic latent image and the developing bias voltage, forming a toner image on the photoreceptor drum 3. The toner image formed on the photoreceptor drum 3 moves to the transfer region N3 due to the rotation of the photoreceptor drum 3, and at this time, the transfer bias voltage applied to the transfer roller 4 transfers the toner image onto the recording paper 101 that has entered the transfer region N3.

[0027] The recording paper 101 carrying the toner image is transported toward the fuser 5, where it is fixed and then discharged to the output tray. The residual toner that remains on the photoreceptor drum 3 without being transferred to the recording material in the transfer region N3 moves toward the charged region N1 as the photoreceptor drum 3 rotates. In the charged region N1, the residual toner becomes negatively charged due to a minute discharge of the charging bias voltage applied to the charging roller 11 and is returned to the developing region N2. In the developing region N2, the residual toner moves toward the developing roller 51 according to the potential difference between the potential of the areas not exposed by the exposure device 8 and the developing bias voltage, and is collected into the developing device 12.

[0028] Specific examples of potential settings, such as the charging potential, for the image forming apparatus using the cleanerless method of this embodiment will be described in detail later.

[0029] Figure 2 is a cross-sectional view showing the schematic configuration of a developing device 12 provided in the image forming apparatus of the present invention. The developing device 12 is a contact one-component developing device and is installed inside the main body of the image forming apparatus. The developing device 12 contains toner as a non-magnetic or magnetic one-component developing agent and comprises a developing housing 50, a developing roller 51 as a developing agent carrier that carries the toner, a supply roller 52 as a developing agent supply member that supplies toner to the developing roller 51, and a regulating blade 53 as a regulating member that regulates the amount of toner carried on the developing roller 51.

[0030] The developing roller 51 rotates counterclockwise in the figure, transporting the toner held on its surface to a position opposite the regulating blade 53 and the photoreceptor drum 3. The developing roller 51 is positioned to contact the photoreceptor drum 3 and forms a toner image by supplying toner to the electrostatic latent image on the photoreceptor drum 3.

[0031] The developing roller 51 is made of a core metal formed of a conductive metal material such as stainless steel, with an elastic layer made of an elastic material having conductive rubber on top, and its thickness is adjusted so that the Asker C hardness of its outer surface is 70 to 80 degrees.

[0032] Since the image forming apparatus of this embodiment employs a cleanerless system, the developing roller 51 is required to collect toner remaining on the photoreceptor drum 3 into the developing device 12. For this reason, the developing roller 51 has a cross-section perpendicular to the axis of rotation that is serrated on its outer circumference. By defining the rotation direction of the developing roller 51 so that the steep surfaces of the serrated shape collide with the surface of the photoreceptor drum 3, the ability to scrape off residual toner from the photoreceptor drum 3 is enhanced.

[0033] The supply roller 52 is positioned in contact with the developing roller 51 and supplies toner from the developing device 12 to the surface of the developing roller 51. The rotation direction is defined so that the direction of movement at the contact point is opposite, and by setting the surface speeds of the developing roller 51 and the supply roller 52 to be approximately the same, a good toner supply function is ensured. The supply roller 52 is made of a core metal formed of a conductive metal material such as stainless steel, on which a foamed polyurethane layer having an electrical resistance of about 3 to 8 is laminated.

[0034] The regulating blade 53 is a plate-shaped member with a thickness of approximately 0.1 mm made of a metal material such as stainless steel, and is provided with its tip in contact with the surface of the developing roller 51. The toner supplied onto the developing roller 51 by the supply roller 52 is thinned and simultaneously frictionally charged as it passes through the regulating blade contact portion A where the regulating blade 53 is in contact with the developing roller 51.

[0035] A toner cartridge 13, which contains replenishment toner, is detachably mounted on the top of the developing unit 12. For this reason, a replenishment port 54 is formed on the top of the developing unit 12 for supplying toner from the toner cartridge 13 into the developing unit 12.

[0036] The toner detection sensor 55 is provided inside the developing device 12 as a means for detecting the remaining amount of toner. Here, an example is given in which an optical sensor is used as the toner detection sensor 55 for detecting the remaining amount of toner inside the developing device 12. This toner detection sensor 55 consists of a light emission sensor 71, a first light guide 72 and a second light guide 73 made of a highly transparent resin material or the like, and a light receiving sensor 74.

[0037] In this toner detection sensor 55, light emitted by the light emission sensor 71 enters through the entrance of the first light guide 72 located on the side of the main body of the developing device 12, and is guided into the interior of the developing device 12 by transmitting through the body of the first light guide 72. The light guided into the interior of the developing device 12 enters through the internal space of the developing device 12 from the exit of the first light guide 72 and is guided to the entrance of the second light guide 73 by transmitting through the body of the second light guide 73 and is guided to the outside of the developing device 12. Subsequently, the light guided to the outside of the developing device 12 is received by a light receiving sensor 74 located near the exit of the second light guide 73. The light receiving sensor 74 converts the amount of received light into a voltage to detect the presence or absence of light.

[0038] The toner detection sensor 55 controls light emission by applying a voltage to the light emission sensor 71 when toner level detection is performed, and the output of the light receiving sensor 74 makes it possible to detect the presence of toner in the internal space of the developing device 12.

[0039] Therefore, the detection location B where the toner detection sensor 55 detects the presence or absence of toner is the spatial region where the exit of the first optical guide 72 and the inlet of the second optical guide 73 face each other. The toner detection sensor 55 is positioned such that detection location B is higher than the regulating blade contact area A. As a result, even when toner is consumed from within the developing device 12 and the amount of toner decreases, and the toner detection sensor 55 detects that there is no toner at detection location B, the toner draft level within the developing device 12 can remain higher than the regulating blade contact area A.

[0040] The toner level detection result is transmitted to the control unit 91 in the image forming apparatus, and the result is reflected in the control of the toner replenishment operation of the toner cartridge 13. Specifically, when the toner detection sensor 55 detects that there is no toner at detection point B, the control unit 91 drives the toner discharge roller 56 of the toner cartridge 13 for a preset time. As a result, a predetermined amount of toner is replenished from the toner cartridge 13 to the developing device 12.

[0041] When the toner in the toner cartridge 13 runs out, the toner detection sensor 55 detects that there is no toner at detection point B. After this, the toner in the developer unit 12 continues to decrease because toner is not replenished, and even if toner level detection is performed, the detection result of "no toner" will be repeated. For example, detection is repeated at intervals of a few seconds. When a decrease is detected, the toner discharge roller 56 starts rotating to replenish the toner. If the detection after a few seconds still detects that there is no toner, the replenishment rotation continues. This detection of "no toner" accompanied by replenishment rotation will continue for a predetermined number of consecutive times.

[0042] If the "no toner" detection result occurs a predetermined number of times consecutively, the control unit 91 determines that the toner cartridge 13 is empty and prompts the user to replace the toner cartridge 13. As a method of prompting the user to replace the toner cartridge 13, for example, a toner cartridge replacement sign can be displayed using a panel 93 or lamp provided on the image forming apparatus. The printer and the PC using it as an output device may also be notified that the toner is empty, that is, to prompt the user to replace the toner cartridge.

[0043] Figure 3 is a cross-sectional view showing the height relationship between the regulating blade contact area A and the detection area B. When the control unit 91 determines that the toner cartridge 13 is empty, a counter 92 provided in the image forming apparatus starts counting the amount of toner lost in the developing apparatus 12. The counter 92 includes a dot counter that counts the number of dots corresponding to the number of pixels during image formation, a consumption counter that estimates the amount of toner consumed due to fogging from the number of rotations of the developing roller 51, a sheet counter that counts the number of sheets of recording paper used for image formation, and a forced consumption counter when forced toner consumption control is performed to refresh the toner on the developing roller 51 when not forming an image.

[0044] Within the developing device 12, the amount of toner C that may exist in the space between the height of the regulating blade contact area A and the height of the detection area B is calculated in advance. When the amount of toner reduction approaches the amount of toner C, the image forming apparatus is stopped to prevent the start of a new printing operation. In addition to this control to prevent the start of a new printing operation, it is preferable to issue a warning to prompt the user to replace the toner cartridge 13. This warning can also be issued to the panel 93 or a personal computer. Since it is a warning, it is preferable that it be in a different form from the aforementioned notification that simply prompts replacement. For example, on a panel, the display could be either "Please replace" or a display that emphasizes urgency, such as "Please replace immediately." If a lamp is used, it should be distinguished between flashing and continuous illumination.

[0045] Figure 4 is a cross-sectional view showing the toner transport mechanism installed in the developing device. The toner transport mechanism is installed in the area through which the detection light passes, transporting the toner in the longitudinal direction of the developing roller. If the amount of toner present in the developing device 12 is uneven or varies from place to place, there is a risk that the toner remaining amount may not be detected accurately. Therefore, a toner transport screw 82 is installed close to the first light guide 72 and the second light guide 73 to move the toner in the axial direction of the developing roller 51, thereby leveling out any unevenness in the amount of toner within the developing device 12.

[0046] Figure 5 is a cross-sectional view showing a toner stirring means installed in the developing device. Figure 6 is a schematic diagram showing the arrangement of components inside the developing device when viewed from above. If toner or foreign matter adheres to the outlet surface of the first light guide 72 or the inlet surface of the second light guide 73, it will block the transmitted light when toner level detection is performed, causing false detection. Therefore, a rotating blade 81 is provided in the space area where the outlet of the first light guide 72 and the inlet surface of the second light guide 73 face each other, and adhesion is prevented by flowing the toner. Furthermore, it is preferable to provide a cleaning mechanism in which a cleaning material such as a sheet material is attached to the rotating blade 81 and the adhering material is removed by rubbing it against the outlet surface of the first light guide 72 and the inlet surface of the second light guide 73.

[0047] Figures 7 to 10 are explanatory diagrams illustrating specific potential setting examples, such as the charging potential, of an image forming apparatus using the cleanerless method of this embodiment. In Figure 7, the charging roller 11 is positioned in contact with the photoreceptor drum 3, and a charging bias voltage of -1100V is applied to charge the surface of the photoreceptor drum 3 to approximately -500V. The exposure apparatus 8 exposes the photoreceptor drum 3 to exposure light L, forming an electrostatic latent image on the photoreceptor drum 3. A developing bias voltage of -300V is applied to the developing roller 51 provided in the developing apparatus 12, supplying toner 200 to the photoreceptor drum 3. This forms a toner image on the photoreceptor drum 3. The developing apparatus 12 has a supply roller 52, which supplies toner from within the developing apparatus 12 onto the developing roller 51.

[0048] The transfer roller 4 transfers the toner image on the photoreceptor drum 3 to the recording paper 101. The static elimination lamp 20 eliminates the potential of the photoreceptor drum 3. The surface of the photoreceptor drum 3 is de-staticized to approximately -50V by irradiation with the static elimination light QL.

[0049] The toner flow in Figure 7 is as follows: The developing roller 51 carries the toner 200, and the toner 200 carried on the developing roller 51 is supplied to the photoreceptor drum 3. The toner 201 supplied to the photoreceptor drum 3 forms a toner image according to the electrostatic latent image. The toner 201 on the photoreceptor drum 3 is transferred to the recording paper 101. The toner 202 transferred to the recording paper 101 is fixed to the recording paper 101 in a later process. Toner that was not transferred in the transfer process remains on the photoreceptor drum 3 as residual toner 203. After the static discharge process, the residual toner 203 adheres to the charging roller 11 at the contact point between the photoreceptor drum 3 and the charging roller 11. Of the residual toner 203, there is also toner 206 that does not adhere to the charging roller 11, and this toner 206 remains on the photoreceptor drum 3. This toner 206 is recovered by the developing roller 51.

[0050] Figures 8, 9, and 10 illustrate an example of a method for recovering residual toner in a cleanerless image forming apparatus. Figure 8 is a schematic diagram illustrating the state after Figure 7, and schematically shows the state during printing. "During printing" here means the state in which the apparatus is in operation, and includes not only the process of transferring toner to the recording paper, but also the process of preparing to transfer toner to the recording paper. Figure 8 illustrates the process performed between the transfer to the previous recording paper and the transfer to the next recording paper.

[0051] As explained in Figure 7, toner that is not transferred during the transfer process remains on the photoreceptor drum 3 as transfer residue toner 203. In Figure 8, the transfer residue toner 203 remains on the photoreceptor drum 3 downstream of the transfer roller 4. After the transfer is performed on the previous recording paper 101, the surface of the photoreceptor drum 3 is discharged by the static discharge lamp 20. This widens the potential difference between the charging roller 11 and the photoreceptor drum 3, causing a discharge to occur between the charging roller 11 and the photoreceptor drum 3 before charging. The discharge is schematically illustrated in the figure.

[0052] Due to the discharge before charging, the residual toner 203 becomes negatively charged. In the residual toner 203, due to the discharge before charging, some remains negatively charged, while others remain slightly positively charged. The slightly positive residual toner 203 adheres to the charging roller 11 at the point where it comes into contact with the photoreceptor drum 3. The toner adhering to the charging roller 11 is shown as toner 204. Arrow A in the figure schematically illustrates the adhesion of residual toner 203 on the photoreceptor drum 3 to the charging roller 11.

[0053] Of the transfer residue toner 203 on the photoconductor drum 3, the negatively charged toner does not adhere to the charging roller 11 and remains on the photoconductor drum 3. This toner is shown as toner 206. Both toner 203 and toner 206 are transfer residue toner. The toner 206 remaining on the photoconductor drum 3 is collected by the developing roller 51 due to the potential difference between the photoconductor drum 3 and the developing roller 51 as it passes between the photoconductor drum 3 and the developing roller 51. Arrow B in the figure schematically illustrates the collection of toner 206 on the photoconductor drum 3 by the developing roller 51, and the toner collected by the developing roller 51 is shown as toner 208.

[0054] As described above, one way to recover the material with the developing roller 51 is to adjust the potential of each component. For example, the surface of the photoreceptor drum 3 after static discharge may be set to -50V, the potential of the charging roller to -1100V, the surface of the photoreceptor drum 3 after charging to -500V, and the potential of the developing roller 51 to -300V. Figure 8 illustrates the potentials in this example, but it is not limited to this.

[0055] Next, using Figures 9 and 10, we will explain the movement of toner during device shutdown and an example of toner recovery. As explained in Figure 8, the positively charged residual toner 203 (and similarly toner 206) that did not become negative during the discharge before charging adheres to the charging roller 11. The minutely positively charged toner 205 moves to the photoreceptor drum 3 due to the potential difference between the charging roller 11 and the photoreceptor drum 3. This is indicated by arrow C in the figure. This moved toner is shown as toner 209 in the figure. Note that during device shutdown, the photoreceptor drum 3 is not discharged by the static discharge lamp 20, so the potential difference between the charging roller 11 and the photoreceptor drum 3 is adjusted to account for this.

[0056] The positively charged toner 209 on the photoreceptor drum 3 is not collected by the developing roller 51, but passes directly to the opposite side of the developing roller 51. Furthermore, the toner 209 also passes to the opposite side of the transfer roller 4. Thus, when the device is shut down, positively charged toner 209 remains on the photoreceptor drum 3. In Figures 8 to 10, toners 203, 206, and 209 are shown on the photoreceptor drum 3. These are all considered as transfer residue toner. Toner 209 is formed when transfer residue toner 203 adheres to the charging roller 11 and then moves back onto the photoreceptor drum 3; however, such toner may also be included in the transfer residue toner.

[0057] To allow the toner to move as shown in the example in Figure 9, one method is to adjust the potential of each component. For example, the potential of the charging roller 11 could be set to -350V, the potential of the surface of the photoreceptor drum 3 to -500V, and the potential of the developing roller 51 to +250V, but this is not the only method.

[0058] Next, we will explain, using Figure 10, how toner on the photoreceptor drum 3 is recovered during the shutdown of the device. Figure 10 is a continuation of Figure 9. As shown in the figure, the photoreceptor drum 3 is discharged by the static discharge lamp 20 at a predetermined timing. By performing static discharge, the potential difference between the charging roller 11 and the photoreceptor drum 3 widens, and a discharge occurs between the charging roller 11 and the photoreceptor drum 3. The discharge is schematically illustrated in the figure. Note that the static discharge shown is not static discharge performed for image formation, but static discharge performed for toner recovery.

[0059] As a result of the discharge described above, the toner 209 becomes negatively charged. As in Figure 8, the toner 209 that does not become negatively charged and remains positively charged adheres to the charging roller 160 (arrow D in the figure). The toner 209 that has become negatively charged due to the discharge described above remains on the photoreceptor drum 3 without moving to the charging roller 11. The negatively charged toner 209 is then collected by the developing roller 51 to which a developing bias is applied (arrow E in the figure). The toner collected by the developing roller 51 is shown as toner 208 in the figure.

[0060] To allow the toner to move as shown in the example in Figure 10, one method is to adjust the potential of each component. For example, the potential of the charging roller 11 could be set to -1100V, the surface of the photoreceptor drum 3 after static discharge to -50V, the potential of the surface of the photoreceptor drum 3 to -500V, and the potential of the developing roller 51 to -300V. Figure 10 illustrates the potentials in this example, but it is not limited to this.

[0061] <Confirmation of the effects in this embodiment> Two RICOH P501 printers, modified to a cleanerless system, were prepared, and one image forming apparatus for this embodiment and one for the comparative example were created. Print durability tests were conducted on these two image forming apparatuses to confirm their effectiveness in preventing vertical streak-like image defects caused by paper dust getting trapped in the regulating blade contact area A.

[0062] The toner used is a non-magnetic, one-component developer toner with an average particle size of 7 mm, produced by a pulverization method, and is used with negative polarity charge. The toner consists of toner matrix particles and external additives. The toner matrix particles contain a binder resin, a charge control agent, a colorant such as carbon black, and a release agent such as wax, while the external additives contain inorganic fine particles such as silica.

[0063] In this embodiment, the image forming apparatus is configured to replace the toner cartridge 13 immediately after the control unit 91 determines that the toner cartridge 13 is empty based on the detection result of the toner detection sensor 55. On the other hand, in the comparative example, the image forming apparatus continues printing without replacing the toner cartridge 13 even after the control unit 91 determines that the toner cartridge 13 is empty based on the detection result of the toner detection sensor 55, and the settings of the counter 92 are intentionally changed so that the toner cartridge 13 is replaced when the height of the toner draft T in the developing unit 12 becomes approximately 4 cm lower than the height of the regulating blade contact part A.

[0064] The print durability test involved continuously printing with a print area ratio of 2%, and counting the number of sheets until vertical streaks appeared in the image. Ricoh MyPaper was used as the recording paper. As a result, while vertical streaks appeared on the image after 7,000 sheets in the comparative example's image forming apparatus, no vertical streaks appeared in the image forming apparatus of this embodiment even after 50,000 sheets. Thus, by maintaining the height of the toner water level T in the developing apparatus 12 higher than the regulating blade contact area A, it is possible to suppress the intrusion of paper dust into the regulating blade contact area A and prevent vertical streaks in the image.

[0065] Although preferred embodiments of the present invention have been described above, the present invention is not limited to these specific embodiments, and unless otherwise specifically limited in the above description, various modifications and changes are possible within the scope of the spirit of the present invention as described in the claims. For example, although an embodiment using a one-component toner as a one-component developer has been described, it can also be applied to a developing apparatus using a two-component developer, which may cause paper dust clogging in the gap between the image carrier and the developer layer restricting member. The effects described in the embodiments of the present invention are merely a list of the most preferred effects arising from the present invention, and the effects of the present invention are not limited to those described in the embodiments of the present invention.

[0066] The above description is merely an example, and the present invention provides specific effects for each of the following embodiments. In the description of the embodiments, the symbols in parentheses after the component names are examples of corresponding components and are not limited to these examples.

[0067] (Aspect 1) An image forming apparatus comprising: a developing device that thins the developer in a developing unit (12) supplied to a developer carrier (51) on the developer carrier (51) using a layer thickness regulating member (53), and then develops the latent image on a latent image carrier in a developing area using the thinned developer; and a notification means (91) that notifies prompt information to encourage the user to replenish the developer used in the developing unit (12), wherein the notification means (91) notifies when the height of the developer water level is higher than a first height which is the height of the contact point (A) of the layer thickness regulating member (53) with the developer carrier (51). Here, the user's replenishment operation of the developer used in the developing unit (12) refers to a direct replenishment operation in a direct developer replenishment method, or an operation to replace the replenishment developer container in a sequential developer replenishment method. According to this method, the developer level can be kept above the contact point, thus preventing paper dust from clogging the contact point.

[0068] (Aspect 2) The image forming apparatus according to Embodiment 1 is further equipped with a user notification means (91) that provides notification to the user based on prompting information from a notification means (91), wherein the notification means (91) provides notification when the developer draft height is higher than a first height, and also when it reaches the first height, and the user notification means (91) that receives the latter notification provides user notification in a different manner than when it receives the former notification. Here, the "different notification" is a manner that allows the user to perceive a higher degree of urgency for replenishment.

[0069] (Aspect 3) The image forming apparatus according to embodiment 1 or 2 is characterized in that, after prompt notification, when the height of the developer draft reaches a first height, the start of subsequent image forming operations is stopped by image forming stop control. This makes it possible to avoid printing in which abnormal images occur.

[0070] (Aspect 4) In the image forming apparatus according to any one of embodiments 1 to 3, the developing apparatus is a sequential developer supply method in which developer is supplied to the developing unit (12) sequentially from a replenishment developer container, and the sequential developer supply method is characterized in that it is performed in such a way as to maintain a predetermined height higher than the first height. This sequential replenishment method involves, for example, providing a detection means for detecting the amount of developer in the developing unit (12), and maintaining the developer level at or above the second height based on the detection means detecting a drop in the developer draft from a predetermined second height that is higher than the first height. The present invention is applicable not only to developing devices using the sequential developer replenishment method, but also to developing devices using the direct developer replenishment method.

[0071] (Appendix 5) An image forming apparatus according to any one of embodiments 1 to 4 is provided with a detection means for detecting the amount of developer in the developing unit (12), and the notification means (91) is characterized in that it notifies based on the detection result of the detection means. Unlike this embodiment, the present invention can also be applied to an image forming apparatus that, without providing a detection means, estimates and determines the amount of developer by calculating the amount of developer consumed, which is predicted from image information (pixel information) formed thereafter, from the amount of developer in the developing unit (12) when the amount of developer is known.

[0072] (Aspect 6) In the image forming apparatus described in Embodiment 5, the detection means detects a drop in the developer draft from a predetermined second height that is higher than the first height, and the notification means (91) is characterized in that, after the detection means detects a drop from the second height, it notifies at a predetermined timing that is higher than the first height.

[0073] (Aspect 7) In the image forming apparatus described in Embodiment 5, the detection means is an optical detection means, and a developer transport means is provided at the location through which the detection light passes, for transporting the developer in the longitudinal direction of the developer carrier (51).

[0074] (Pattern 8) In the image forming apparatus described in Embodiment 7, the developer transport means is characterized by being a rotating screw member.

[0075] (Aspect 9) In the image forming apparatus described in Embodiment 5, the detection means is an optical detection means in which a first light guide that guides light from a light-emitting element and a second light guide that guides light to a light-receiving element are provided such that the light-emitting part of the former and the light-receiving part of the latter are spaced apart and facing each other in the developing container, and a developer stirring means is provided between the light-emitting part and the light-receiving part.

[0076] (Aspect 10) An image forming apparatus according to any one of embodiments 1 to 9, wherein the apparatus has a supply rotating body that supplies the developer in the developing unit (12) to the developer carrier (51), and the developer carrier (51) is characterized in that it collects the transfer residue toner on the latent image carrier. In this embodiment, a supply rotating body is used, but the developer may be supplied to the developer carrier by other means. Furthermore, although this embodiment is a cleanerless image forming apparatus, it can also be applied to an image forming apparatus with a cleaner and a recycling system that returns the transfer residue toner recovered by the cleaner to the developer container. [Explanation of Symbols]

[0077] 1:Paper feeding means 2: Resistroller vs. 3: Photoconductor drum 4: Transfer roller 5: Fixing device 6: Paper feed tray 7: Paper feed roller 8: Exposure equipment 11: Electrostatic roller 12: Developing equipment 13: Toner Cartridge 20: Static electricity removal lamp 50: Developing Housing 51: Developing roller 52: Supply roller 53: Regulatory Blade 54: Supply port 55: Toner detection sensor 56: Toner ejection roller 71: Light-emitting sensor 72: First Optical Guide 73: The Second Light Guide 74: Light receiving sensor 81: Rotating blades 82: Toner transport screw 91: Control Unit 92: Counter 101: Recording paper 160: Electrostatic roller A: Regulating blade contact area B: Detection location C: Toner quantity L: Exposure light N1: Charged region N2:Development area N3: Transcription region P:Paper powder QL: Static elimination light T: Toner draft [Prior art documents] [Patent Documents]

[0078] [Patent Document 1] Patent No. 7286358

Claims

1. A developing apparatus that, after thinning the developer in the developing unit supplied to the developer carrier using a layer thickness regulating member, develops the latent image on the latent image carrier in the developing area using the thinned developer, A notification means for providing prompt information to encourage the user to replenish the developer used in the developing device, In an image forming apparatus equipped with, The image forming apparatus is characterized in that the notification means provides notification when the height of the developer draft is higher than a first height which is the height of the contact point of the layer thickness regulating member with the developer carrier.

2. In the image forming apparatus according to claim 1, The system includes a user notification means that provides notification to the user based on prompting information from the aforementioned notification means, The image forming apparatus is characterized in that the notification means provides notification when the developer draft is higher than the first height, and also provides notification when it reaches the first height, and the user notification means, upon receiving the latter notification, provides user notification in a different manner than when it received the former notification.

3. In the image forming apparatus according to claim 1, An image forming apparatus characterized by performing image forming stop control to stop the subsequent image forming operation when the height of the developer draft reaches the first height after the prompt notification.

4. In the image forming apparatus according to claim 1, The developing apparatus uses a sequential developer supply method, in which developer is supplied to the developing unit sequentially from a replenishment developer container. The image forming apparatus is characterized in that the sequential replenishment method of the developer is performed in such a way that it maintains a predetermined height higher than the first height.

5. In the image forming apparatus according to claim 1, The device is equipped with a detection means for detecting the amount of developer in the developing unit, The image forming apparatus is characterized in that the notification means provides notification based on the detection result of the detection means.

6. In the image forming apparatus according to claim 5, The detection means detects a drop in the developer draft from a predetermined second height that is higher than the first height. The notification means is characterized by providing notification at a predetermined timing, which is higher than the first height, after the detection means has detected a drop from the second height.

7. In the image forming apparatus according to claim 5, The aforementioned detection means is an optical detection means, An image forming apparatus characterized by having a developer transport means provided at the location through which detection light passes, for transporting the developer in the longitudinal direction of the developer carrier.

8. In the image forming apparatus according to claim 7, The image forming apparatus is characterized in that the developer transport means is a rotating screw member.

9. In the image forming apparatus according to claim 5, The detection means is an optical detection means in which a first light guide that guides light from a light-emitting element and a second light guide that guides light to a light-receiving element are provided such that the light-emitting part of the former and the light-receiving part of the latter are spaced apart and facing each other within the developing container. An image forming apparatus characterized by having a developer stirring means provided between the light emitting section and the light receiving section.

10. In the image forming apparatus according to any one of claims 1 to 9, An image forming apparatus having a supply rotating body that supplies the developer in the developing unit to the developer carrier, wherein the developer carrier recovers the transfer residue toner on the latent image carrier.

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