JP4566809B2 - Image forming apparatus and developing apparatus - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, and various printers, and a developing device used therefor, and more particularly to an image forming apparatus and a developing device provided with a supply mechanism for an anti-missing agent. .

  In the electrophotographic transfer process employed in various image forming apparatuses, first, a charged toner is electrostatically attached (developed) to an electrostatic latent image formed on a photosensitive drum, and then a bias voltage is applied. A technique of transferring onto a sheet using a roller is employed. At this time, it is necessary to transfer the toner on the photosensitive drum to a predetermined position on the paper without omission, but due to the deterioration of the releasability of the toner from the surface of the photosensitive drum, for example, the center of the line image There may be an image defect in which a toner non-transfer area such as a hole occurs in such a portion (such an image defect is referred to as “blank” in this specification).

Conventionally, in order to suppress such voids, for example, Patent Document 1 discloses a developing method in which a void preventing agent made of a metal soap such as zinc stearate is added to a toner. Such an anti-missing agent functions as a lubricant between the photosensitive drum and the toner, and improves the transfer efficiency because it improves the releasability of the developed toner from the surface of the photosensitive drum. Thus, the hollowing out phenomenon is suppressed.
Japanese Patent No. 3173321

  According to the method disclosed in Patent Document 1, the toner is provided with a void-preventing agent together with the toner, and the toner is secured on the surface of the photosensitive drum by ensuring that the toner releasability is secured. It is. That is, the supply amount of the anti-blading agent depends on the toner supply amount to the photosensitive drum. Accordingly, when images with low density (such as images with many white backgrounds) are continuously formed, the amount of toner supplied to the photoconductive drum is reduced and the amount of supply of the anti-blading agent is reduced. In this case, a blade or the like is brought into contact with the surface of the photosensitive drum, and the hollowing out preventive agent attached to the surface is gradually scraped off. , There was a problem that the desired effect of preventing the lack of a streak could not be obtained.

  Accordingly, the present invention provides an image forming apparatus and a developing device that can supply a void-preventing agent from the developing device to the photosensitive drum without excess or deficiency according to the amount of toner consumed, thereby preventing the occurrence of image defects due to voids. The purpose is to do.

  According to a first aspect of the present invention, a toner to which a predetermined anti-missing agent is added is supplied onto the photosensitive drum, and the toner is attached to the electrostatic latent image formed on the photosensitive drum. An image forming apparatus comprising: a developing device; and a transfer device that transfers a toner image formed on the photosensitive drum in accordance with the electrostatic latent image onto a predetermined transfer material, wherein An anti-deleting agent replenishing unit that stores and is capable of supplying an anti-deleting agent to the developing device; and a toner consumption detecting unit that detects a consumption amount of toner supplied onto the photosensitive drum; Based on the consumption amount of the toner, a supply amount of the anti-missing agent to the photosensitive drum is obtained, determination means for determining whether the supply amount satisfies a predetermined threshold, and the supply amount is predetermined. Is determined not to meet the threshold Case, characterized by comprising a supply control means for replenishing the inhibitor incomplete toner from anti replenishing means dropout during the said developing device.

  According to this configuration, when the determination unit determines whether or not replenishment of the anti-missing agent is necessary based on the toner consumption actually used in the image forming apparatus, and the determination unit determines that replenishment is necessary, A developing agent is supplied to the developing device from the anti-missing agent supply means. As a result, the inside of the developing device can be rich in the ratio of the anti-missing agent to the toner, and a state in which the supply amount of the anti-missing agent to the photosensitive drum can be increased can be formed.

  In the above-described configuration, the toner consumption amount detection unit may be configured to obtain the toner consumption amount per fixed driving time based on the dot count number of the image data formed with the image and the driving time of the image forming apparatus. (Claim 2). According to this configuration, it is possible to quantitatively grasp the toner consumption based on the dot count number and indirectly determine the adhesion state of the anti-missing agent to the surface of the photosensitive drum by considering the driving time. become.

  Further, a mode switching unit that selectively switches between a normal operation mode in which a normal image forming operation is performed in the image forming apparatus and a replenishment operation mode in which the developing device is replenished with the anti-missing agent from the anti-missing agent replenishing unit. It is desirable that the replenishment control means is configured to run at least the developing device and the photosensitive drum when the replenishment operation mode is selected (claim 3). According to this configuration, it is possible to execute the replenishment operation mode in which the normal operation mode is divided and the dropout preventing agent is replenished. In the replenishment operation mode, the developing device and the photosensitive drum are rotated and operated so that the anti-missing agent can be dispersed substantially uniformly in the developing device, and the anti-missing agent is applied to the photosensitive drum. It becomes possible to replenish.

  According to a fourth aspect of the present invention, there is provided a developing device main body having a housing structure for supplying toner added with a predetermined anti-missing agent onto a photosensitive drum, and the predetermined anti-missing agent. A toner container for storing the toner added with the toner, and a hollow-out preventing agent container for storing the hollow-out preventing agent, wherein the developing device main body receives a toner supplied from the toner container. A replenishment hole and a second replenishment hole that receives the hollow out prevention agent supplied from the hollow out prevention agent container are provided, and the replenishment operation of the hollow out prevention agent through the second replenishment hole is performed by the development. It is controlled by a replenishment control means for determining whether or not replenishment of the anti-blading agent is necessary based on the consumption amount of toner supplied from the apparatus main body onto the photosensitive drum.

  According to this configuration, while the toner to which the anti-missing agent is added is always supplied from the toner container to the main body of the developing device, when the anti-missing agent is insufficient, the anti-missing agent container From this, it is possible to supply only the anti-missing agent to the main body of the developing device. As a result, when it is determined that it is necessary to supply the anti-missing agent, the anti-missing agent can be made rich in the ratio relative to the toner inside the developing device main body, and the anti-missing agent for the photosensitive drum can be reduced. A state in which the supply amount is increased can be formed.

  According to the first and fourth aspects of the present invention, the anti-missing agent is determined according to the toner consumption amount, that is, it is determined from the current state of the toner consumption that the anti-missing agent is insufficient. Occasionally, the anti-missing agent is supplied from the developing device to the photosensitive drum. Therefore, since the state where the anti-missing agent is insufficient is corrected, it is possible to prevent the occurrence of image defects due to the omission.

  According to the second aspect of the present invention, it is possible to accurately determine the adherence state of the anti-missing agent to the surface of the photosensitive drum with easy measurement parameters such as the dot count number and the driving time.

  According to the third aspect of the present invention, it is possible to reliably eliminate the shortage prevention agent in the photosensitive drum through the replenishment operation mode.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic side cross-sectional view showing a color image forming apparatus 10 of a four-tandem development system that is an example of an image forming apparatus (developing apparatus) according to the present invention. As shown in FIG. 1, an image forming apparatus 10 includes an image forming unit 11 that plays a central role in image formation, a transfer belt unit 12 disposed below the image forming unit 11, and the transfer belt unit. 12, a paper storage unit 14 that stores paper to be fed between the image forming unit 11 and the transfer belt unit 12 via the paper supply unit 13, and the image forming unit 11. The fixing unit 15 disposed on the downstream side (left side in FIG. 1) of the transfer belt unit 12 is built in a box-shaped device main body 16 having a rectangular parallelepiped shape in appearance.

  The image forming unit 11 performs a toner image transfer process on the paper supplied from the paper storage unit 14 via the paper supply unit 13, and in the present embodiment, on the upstream side (right side in FIG. 1). Yellow unit 11Y, magenta unit 11M, cyan unit 11C, and black unit 11K, which are sequentially arranged from the downstream side to the downstream side. Each of the units 11Y, 11M, 11C, and 11K is positioned in a predetermined relative positional relationship with respect to the device main body 16 and each part, and is mounted in the device main body 16.

  Each unit 11Y, 11M, 11C, and 11K includes a developing device 20 and a photosensitive drum 111, respectively. Each photoconductor drum 111 is supplied with toner from the corresponding developing device 20 and rotates in the clockwise direction in FIG. 1 (the direction of arrow a in the figure).

  A charger 112 is disposed at a predetermined position on the outer peripheral portion of each photoconductive drum 111 so as to face the surface of the photoconductive drum 111, and an exposure device is disposed at a position downstream of the photoconductive drum 111 in the rotation direction. 113 are provided. Each photosensitive drum 111 is charged uniformly by the charger 112, and light based on image data input from a document image reading device (not shown) is charged from each exposure device 113. By irradiating the peripheral surface of each photoconductive drum 111, an electrostatic latent image is formed on the peripheral surface of each photoconductive drum 111. When toner is supplied from the developing device 20 to such a photosensitive drum 111, the toner adheres to the electrostatic latent image, and a toner image is formed on the peripheral surface of the photosensitive drum 111.

  The exposure device 113 is configured to include, for example, an LED array head, and each LED of the LED array head emits light to the photosensitive drum 111 in accordance with print data (dot image) generated according to document image data. Dot light is irradiated, whereby an electrostatic latent image is formed on the photosensitive drum 111. Here, the dot image corresponds to the density of the document image, and the number of dots increases for a document with a high density. Therefore, there is a relationship that the toner consumption increases when the count value (dot count number) of the dot number increases, and since the light emitted from the LED forms such a dot, the LED is turned on. By counting the number of times (emitted), the toner consumption can be estimated almost accurately.

  The transfer belt unit 12 (transfer device) is provided at a position below the image forming unit 11 so as to correspond to each photosensitive drum 111. The transfer belt unit 12 includes a base 121 mounted on the paper feeding unit 13 and a transfer belt 122 supported by the base 121 and rotating in the counterclockwise direction in FIG. The transfer belt 122 is transferred to a slightly upper position between the driving roller 133 provided at the left end of the base 121 in FIG. 1, the driven roller 134 provided at the right end, and between the driving roller 133 and the driven roller 134. The belt 122 is wound around a plurality of transfer rollers 135 disposed opposite to the respective photosensitive drums 111 via a belt 122, and circulates by the rotational driving of the driving roller 133.

  Each of the transfer rollers 135 is pressed against the corresponding photosensitive drum 111 via the transfer belt 122, so that the transfer from the photosensitive drum 111 to the sheet conveyed by the transfer belt 122 is reliably performed. It has become. Further, a cleaning device 114 for removing residual toner on the circumferential surface of the photosensitive drum 111 and cleaning the photosensitive drum 111 is provided at a lower left position in FIG. 1 of each photosensitive drum 111. The peripheral surface of the photosensitive drum 111 cleaned by the cleaning device 114 is directed to the charger 112 for a new charging process.

  The paper feed unit 13 picks up one sheet at a time from a bundle of paper loaded in the paper storage unit 14 and sends it between the photosensitive drum 111 and the transfer belt 122. In this embodiment, the transfer belt unit 12 is inserted into and removed from the device main body 16 integrally. The sheet feeding unit 13 is disposed at a position facing a predetermined pair of conveying rollers 131 for conveying the uppermost sheet picked up from the sheet bundle in the sheet storage unit 14 and the transfer belt 122 and the photosensitive drum 111. In addition, a registration roller pair 132 and the like for feeding the paper after positioning the paper are provided.

  Then, the paper picked up from the paper storage unit 14 is supplied onto the transfer belt 122 via the conveying roller pair 131 and the registration roller pair 132, and the image forming unit 11 and the transfer belt unit are rotated along the circumference of the transfer belt 122. 12 and the toner images on the photosensitive drums 111 of the image forming units 11Y, 11M, 11C, and 11K are sequentially transferred onto the paper during the passage.

  The sheet on which the toner image has been transferred is introduced into a fixing unit 15 having a fixing roller pair 151, and the color on which toner is fixed on the sheet by a heat fixing process by passing between the heated fixing roller pair 151. An image is formed. The sheet with the color image for which the fixing process has been completed is discharged to a discharge unit 161 formed on the top of the apparatus main body 16 through a predetermined conveyance path.

  2 and 3 are perspective views showing an embodiment of the developing device 20 (developing device main body) applied to such an image forming apparatus 10, and FIG. FIG. 3 shows a state in which the lid 22 is removed from the main body housing part 21. As shown in these drawings, the developing device 20 includes a main body housing portion 21 and a lid body 22 that closes the upper surface opening of the main body housing portion 21. As shown in FIG. 3, an upper screw feeder 23 and a developing roller 26 as shown in FIG. 3, and a lower screw feeder 24 and a pumping roller 25 as shown in FIGS. Are arranged in a predetermined positional relationship.

  A developer is loaded into the main body casing 21. For example, in the case of the two-component development system, this developer is composed of a blend containing toner and magnetic carrier as main components and a predetermined additive added thereto. What is added as such an additive is a hollow-out preventing agent for preventing the above-mentioned hollow-out phenomenon. As such a hollow-out preventing agent, metal soap such as zinc stearate, titanium oxide, strontium oxide, strontium titanate and the like are used.

  The upper surface opening of the main body housing portion 21 is closed by the lid body 22. The lid 22 has a toner replenishment hole 221 (first replenishment hole) for receiving toner supplied from a predetermined toner container in which the developer is stored, and a predetermined replenishment in which the anti-missing agent is stored. A hollow-out preventing agent replenishing hole 222 (second replenishing hole) that receives the hollow-out preventing agent supplied from the hollow-out preventing agent replenishing device (a hollow-out preventing agent container) is provided.

  A predetermined opening / closing mechanism is attached to a portion where the toner supply hole 221 is installed. This opening / closing mechanism opens the opening / closing plate in conjunction with the mounting operation when the toner container is mounted on the lid 22. On the other hand, the opening / closing plate is closed by removing the toner container from the lid 22. In addition, a fixed amount supply mechanism including an electrically controllable shutter mechanism provided in the hollow-out prevention agent replenishing device is opposed to the installation portion of the hollow-out prevention agent replenishment hole 222. When a preventive agent replenishment instruction signal is given, the shutter is "opened" for a predetermined period of time so that the anti-missing agent can be introduced into the main body casing portion 21.

  4 is a front view showing a state in which the toner container 30 and the hollow-out preventing agent replenishing device 40 are mounted on the upper portion of the developing device 20, and FIG. 5 is a cross-sectional view taken along the line AA in FIG. FIG. 4 shows a sectional view taken along line BB in FIG. The internal configuration of the developing device 20 will be briefly described with reference to FIGS.

  The upper screw feeder 23 includes a spiral blade formed in a spiral shape on the outer peripheral surface of the screw shaft, and is accommodated in the upper stirring chamber 211 of the main body casing 21. The upper screw feeder 23 is rotated in the direction of the arrow in the figure, and the developer replenished as appropriate from the toner container 30 and the developer pumped up from the pumping roller 25 from the end side where the toner replenishment hole 221 is installed. Transport toward the center. Similarly, the lower screw feeder 24 includes spiral blades formed in a spiral shape on the outer peripheral surface of the screw shaft, and is housed in the lower stirring chamber 212 of the main body housing portion 21. The spiral blades of the lower screw feeder 24 are spirals in the opposite direction to the spiral blades of the upper screw feeder 23, so that the developer can be conveyed in the direction opposite to the upper screw feeder 23.

  The pumping roller 25 shown in FIG. 5 pumps the developer from the lower stirring chamber 212 (see FIG. 6) and pumps it to the upper stirring chamber 211 through the conveying path 213 and the communication opening 214, and can rotate around the axis. A magnetic pole roller is externally fitted so as to be rotatable integrally with a pumping roller shaft installed on the shaft. In this magnetic pole roller, magnetic poles composed of a plurality of sets of N poles and S poles are formed on the outer peripheral surface at an equal pitch in the circumferential direction, and the developer is formed between these N poles and S poles. It is attracted to the outer peripheral surface of the pumping roller 25 in a state along the magnetic field lines. That is, when the pumping roller 25 rotates, the magnetic carrier in the developer is attracted to the outer peripheral surface thereof, and the toner is accompanied with the magnetic carrier, and eventually the developer composed of the magnetic carrier and the toner is pumped up and conveyed 213. The water is pumped up to the upper stirring chamber 211 through. Accordingly, the developer is circulated by the upper screw feeder 23, the lower screw feeder 24 and the pumping roller 25 inside the developing device 20.

  The developing roller 26 includes a developing roller shaft and a developing roller main body that is concentrically fitted to the developing roller shaft and is externally fitted so as to be integrally rotatable. In the developing roller body, a plurality of magnetic poles are formed over the entire circumference along the peripheral surface from the inside, and the magnetic carrier is attracted by the attracting force of these magnetic poles, and the toner is developed by entraining the toner in the magnetic carrier. The roller 26 is substantially uniformly attached to the peripheral surface. As shown in FIG. 6, the developing roller 26 rotates in the counterclockwise direction indicated by an arrow in the drawing, and is disposed opposite to the circumferential surface of the photosensitive drum 111 that rotates clockwise around the axis. Yes. Then, a part of the developer laminated on the peripheral surface of the developing roller body 26 and regulated to a predetermined layer thickness by the developer regulating blade 261 is supplied to the photosensitive drum 111 along the electrostatic latent image. On the other hand, the carrier and the remaining toner in the developer are collected in the lower stirring chamber 212 while adhering to the peripheral surface of the developing roller body 26.

  FIG. 7 is a functional block diagram showing a functional configuration of the image forming apparatus 10 that extracts portions deeply related to the present invention. The image forming apparatus 10 includes a dot counter 51, a drive time detection unit 52, an overall control unit 60, a ROM (Read Only Memory) 71, a RAM (Random Access Memory) 72, and a dropout prevention agent supply drive unit 80. .

  The dot counter 51 measures the number of lighting dots irradiated by the exposure device 113 corresponding to the print data. Specifically, the dot counter 51 detects an on / off signal that is a light emission control signal given to the LED array head, and accumulates and counts the number of lit dots each time an on signal is detected. The driving time detection unit 52 includes a timer device and the like, and counts the driving time of the image forming unit in the image forming apparatus 10. These dot number count value and drive time count value are sent to the overall control unit 60, and are used for calculation of the toner consumption and the supply amount of the anti-missing agent.

  The overall control unit 60 includes a CPU (Central Processing Unit) and the like, and generates various control signals for controlling the operation of each unit of the image forming apparatus 10, and in addition to the present invention, a toner consumption amount detection unit 61. The determination unit 62, the replenishment control unit 63, and the mode switching unit 64 are provided.

  The toner consumption amount detection unit 61 calculates the toner consumption amount within a predetermined drive time based on the dot number count value detected by the dot counter 51 and the drive time count value detected by the drive time detection unit 52. Perform the operation. As described above, since the dot number count value and the toner consumption amount supplied to the photosensitive drum 111 are proportional, the toner consumption amount detection unit 61 calculates the preset dot number count value and the toner consumption amount. By referring to the associated table, a process of converting the dot count value per predetermined driving time into toner consumption is performed.

  The determination unit 62 obtains the supply amount of the anti-missing agent to the photosensitive drum 111 based on the toner consumption amount obtained by the toner consumption amount detection unit 61, and the supply amount satisfies a predetermined threshold value. It is a functional unit that determines whether or not there is. Since the anti-missing agent moves along with the toner, the amount of toner supplied to the photosensitive drum 111 and the amount of anti-missing agent supplied to the photosensitive drum 111 are in a certain proportional relationship. Accordingly, the determination unit 62 first calculates the supply amount of the anti-missing agent to the photosensitive drum 111 from the toner consumption amount per predetermined driving time. Then, it is determined whether the supply amount of the anti-missing agent obtained in this way satisfies a predetermined threshold value regarding the proper holding amount of the anti-missing agent in the photosensitive drum 111.

  That is, in the case of a document with a high density (a document with a lot of black background), the number of dots increases (the dot count value becomes relatively large). In this case, the toner consumption increases. In this case, since the anti-missing agent is supplied in accordance with the supply of toner to the photosensitive drum 111, the holding amount of the anti-missing agent in the photosensitive drum 111 is maintained at an appropriate amount. On the other hand, in the case of a document having a low density (a document having a lot of white background), the number of dots is naturally reduced (the dot count value is relatively small). The amount of toner consumed within the driving time is reduced. In this case, since the supply amount of the anti-missing agent is reduced, the holding amount of the anti-missing agent of the photosensitive drum 111 is decreased. When the retention amount of the anti-missing agent falls below a certain value, the defect in the formed image is generated. Accordingly, the determination unit 62 determines that the hollow-out prevention agent is held on the photosensitive drum 111 at a level that can prevent the hollow-out defect based on the supply amount of the hollow-out prevention agent estimated from the toner consumption. It is to determine whether or not.

  When the determination unit 62 determines that the supply amount of the anti-missing agent does not satisfy a predetermined threshold, the replenishment control unit 63 (replenishment control means) A control signal for causing the developing device 20 to supply a predetermined amount of the anti-missing agent stored in the anti-missing agent replenishing device 40 (see FIGS. 4 and 6) is generated. That is, when it is determined that the holding amount of the anti-missing agent on the photosensitive drum 111 is in an insufficient state, the anti-missing agent is supplied from the anti-missing agent replenishing device 40 to the developing device 20 so as to compensate for the insufficient amount. The middle drop prevention agent replenishment drive unit 80 is controlled to replenish.

  The mode switching unit 64 has a normal operation mode in which a normal image forming operation is performed in the image forming apparatus 10, and a replenishment operation mode in which the developing device 20 is replenished with the void prevention agent supply driving unit 80. Selectively switch. Such mode switching is performed automatically when the determination unit 62 determines that the retention amount of the anti-missing agent is in an insufficiency state or in the sleep mode after it is determined to be in an insufficiency state. The replenishment control unit 63 performs a replenishment operation of the anti-missing agent when the operation mode is switched to the replenishment operation mode by the mode switching unit 64.

  When the replenishment operation mode is selected by the mode switching unit 64, the replenishment control unit 63 not only replenishes the dropout prevention agent by the dropout prevention agent replenishment drive unit 80, but also causes the developing device 20 and the photosensitive drum 111 to function. Let it run idle. This idling operation is performed by driving the upper screw feeder 23, the lower screw feeder 24, the pumping roller 25, and the developing roller 26 in the developing device 20, and the already-supplemented anti-drop agent and the already-supplemented agent in the developing device 20. The developer that has been filled is stirred and mixed. As a result, a state in which the developing device 20 is filled with the developer rich in the anti-missing agent is formed, and the supply amount of the anti-missing agent to the photosensitive drum 111 can be increased. In the replenishment operation mode, it is desirable to form a dummy electrostatic latent image on the photosensitive drum 111 and forcibly replenish the anti-missing agent.

  The ROM 71 stores a control program and the like for operating the image forming apparatus 10. The control program stored in the ROM 71 is appropriately read and executed by the overall control unit 60, so that the image forming apparatus 10. Each part operates. In addition to temporarily storing print data for image formation, the RAM 72 also temporarily stores the dot number count value and the drive time count value described above. A predetermined threshold value related to the amount of data stored is also stored.

  The dropout prevention agent replenishment drive unit 80 is controlled by the replenishment control unit 63 and is a mechanism for replenishing the dropout prevention agent from the dropout prevention agent replenishment device 40 to the developing device 20 through the fallout prevention agent replenishment hole 222. Is operated, and an operation for sending out the anti-missing agent by an amount corresponding to the supply control value given from the supply control unit 63 is performed.

  The operation of the image forming apparatus 10 configured as described above will be described. FIG. 8 is a flowchart for explaining the operation of supplying the anti-missing agent. First, when the image forming apparatus 10 is operated in the normal operation mode, it is sequentially detected what density state image forming output is being performed (step S1). What is detected here is the dot count value detected by the dot counter 51 and the drive time count value detected by the drive time detector 52.

  Next, the determination unit 62 obtains a toner consumption amount per predetermined driving time from the dot number count value detected in step S1 and the driving time count value, and based on the toner consumption amount, the photosensitive drum 111 is loaded. A calculation for estimating the supply amount of the anti-missing agent is performed (step S2). Then, a process for comparing the estimated value of the supplied amount of the anti-missing agent and the predetermined threshold value stored in the RAM 72 is executed, and the holding amount of the anti-missing agent in the photoconductive drum 111 becomes insufficient. It is determined whether or not there is (step S3).

  When the retained amount of the anti-missing agent is within the normal range (NO in step S3), the process returns to step S1 and the process is repeated as it is. On the other hand, if it is determined that the retention amount of the anti-missing agent is insufficient (YES in step S3), it is necessary from the estimated value of the anti-missing agent supply amount obtained in step S2 by the replenishment control unit 63. The replenishment amount of the anti-missing agent is calculated (step S4).

  Thereafter, the mode switching unit 64 switches the operation mode of the image forming apparatus 10 from the normal operation mode to the replenishment operation mode (step S5). As a result, the normal image forming operation is prohibited. Subsequently, the replenishment control unit 63 generates a control signal for driving the anti-missing agent supply driving unit 80, and a predetermined amount of anti-missing agent is supplied from the anti-missing agent supply device 40 that stores the anti-missing agent to the developing device. 20 is replenished (step S6). Substantially in parallel with this replenishment operation, the replenishment control unit 63 performs the idling operation of the image forming unit, and the developer and the newly supplied drop-out preventing agent are agitated (step S7). In addition, an anti-missing agent is supplied to the photosensitive drum 111 through the toner, for example, by forming a dummy electrostatic latent image on the photosensitive drum 111.

  Next, it is confirmed whether or not the supply of the predetermined amount of the anti-missing agent is completed (step S8). If the completion of the supply is confirmed (YES in step S8), the supply controller 63 stops the idling operation. Then, the operation mode is switched from the replenishment operation mode to the normal operation mode by the mode switching unit 64 (step S9), and the process returns to step S1 and is repeated.

  In the following, as in the above-described embodiment, a hollow-out prevention agent replenishing device 40 is provided separately from the developer-containing toner container 30 in which a predetermined amount of zinc stearate as a hollow-out prevention agent is blended. When the toner is replenished according to the amount of toner consumed (Example) and when only the toner container containing the developer containing a predetermined amount of zinc stearate is used and the developer is appropriately replenished according to the toner consumption (Comparative Example) ) Was evaluated for the occurrence of hollow defects.

  For the evaluation, we prepared six types of simulated manuscripts with different density grades (simulated manuscripts with a black space ratio of 0.5%, 1%, 5%, 10%, 20%, 30% in white background manuscripts). The image forming operation is executed, and the density ID, the fog amount FD, and the charge amount of the image formed at the start of the image formation, the density ID, the fog amount FD, the charge amount of the image formed after printing 30000 sheets, The situation of the occurrence of voids was conducted. For each of the example and the comparative example, a continuous image forming operation (Example 1, Comparative Example 1) and an intermittent image forming operation (Example 2, Comparative Example 2) with a certain interval are used. Both sides were evaluated. The density ID was measured using a reflection densitometer TC-6DS manufactured by Tokyo Denshoku Co., Ltd., and the occurrence of a void was dependent on visual observation using a loupe.

  First, Table 1 and Table 2 show the evaluation results of Example 1 and Example 2. As is apparent from these data, even after continuous printing of 30,000 sheets regardless of continuous or intermittent image forming operation, a defect in the middle of a 0.5% original document having a low original density grade and a 1% original document are not defective. It was not recognized and it was confirmed that a good image was formed. Furthermore, it was confirmed that the charge amount is in the normal range (10 to 20 μC / g), so-called charge-up (a phenomenon in which the charge amount is increased due to deterioration of toner sliding properties. When charge-up occurs, toner separation becomes worse, It was also confirmed that the formed image has an effect of suppressing density).

  Next, Table 3 and Table 4 show the evaluation results of Comparative Example 1 and Comparative Example 2. In Comparative Example 1, a missing defect occurs in a 0.5% original and 1% original having a low original density grade after 30,000 sheets are printed. In Comparative Example 2, a 0.5% original, 1% original, and 5% are generated. It was confirmed that a missing defect occurred in the manuscript. In addition, in these document density grades, a charge-up phenomenon in which the charge amount exceeds 20 μC / g was also confirmed.

  As mentioned above, although embodiment of this invention was described, it is not limited to this, It can implement in the aspect variously deformed. For example, the present invention can be applied to a monochrome printer, a copying machine, a facsimile machine, and a complex machine thereof. Various methods other than counting the number of dots can be employed for the toner consumption detection method.

1 is a side cross-sectional view showing a four-tandem color image forming apparatus that is an example of an image forming apparatus according to the present invention. FIG. 2 is a perspective view illustrating an embodiment of a developing device incorporated in the image forming apparatus, and illustrates a state where a lid is attached to a main body housing portion of the developing device. Similarly, it is a perspective view showing one embodiment of a developing device, and shows a state where a lid is removed from a main body casing. FIG. 6 is a front view showing a state in which a toner container and a dropout preventing agent replenishing device are mounted on the upper part of the developing device. It is the sectional view on the AA line of FIG. It is the BB sectional view taken on the line of FIG. FIG. 2 is a functional block diagram showing a functional configuration of an image forming apparatus that extracts a part deeply related to the present invention. 5 is a flowchart for explaining a supply operation of a hollow-out preventing agent in the image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 111 Photosensitive drum 12 Transfer belt unit (transfer means)
135 Transfer Roller 20 Developing Device 21 Main Body Housing 22 Lid 221 Toner Supply Hole (First Supply Hole)
222 Hole prevention agent supply hole (second supply hole)
26 Developing roller 30 Toner container 40 Stalling agent replenisher replenishment device (spinning prevention agent replenishing means / slipping agent preventing container)
51 dot counter 52 drive time detection unit 60 overall control unit 61 toner consumption amount detection unit (toner consumption amount detection means)
62 determination unit (determination means)
63 Supply control unit (Supply control means)
64 mode switching unit (mode switching means)
80 Stalling agent replenishment drive unit

Claims (4)

A developing device that supplies toner to which a predetermined anti-missing agent is added to the photosensitive drum and attaches the toner to an electrostatic latent image formed on the photosensitive drum, and the electrostatic on the photosensitive drum. An image forming apparatus comprising a transfer device that transfers a toner image formed according to a latent image onto a predetermined transfer material,
A hollow-out preventing agent replenishing means that stores the hollow-out preventing agent and is capable of replenishing the developing device with a hollow-out preventing agent;
Toner consumption detecting means for detecting consumption of toner supplied onto the photosensitive drum;
Determining means for determining a supply amount of the anti-missing agent to the photosensitive drum based on the consumption amount of the toner, and determining whether the supply amount satisfies a predetermined threshold;
An image forming system comprising: a replenishment control unit that replenishes the developing device with a blowout prevention agent from the blowout prevention agent replenishment unit when it is determined that the supply amount does not satisfy a predetermined threshold value. apparatus.   2. The toner consumption amount detection unit obtains a toner consumption amount per fixed driving time based on a dot count number of image data formed with an image and a driving time of the image forming apparatus. The image forming apparatus described. A normal operation mode for performing a normal image forming operation in the image forming apparatus;
A mode switching means for selectively switching between a replenishment operation mode in which the developing device is replenished with the anti-missing agent from the anti-missing agent replenishing means;
3. The image forming apparatus according to claim 1, wherein the replenishment control unit idles at least the developing device and the photosensitive drum when the replenishment operation mode is selected. A developing device main body having a housing structure for supplying toner to which a predetermined anti-missing agent is added onto the photosensitive drum;
A toner container for storing toner to which the predetermined anti-missing agent is added;
A hollow-out preventing agent container for storing the hollow-out preventing agent;
The developing device main body is provided with a first supply hole for receiving the toner supplied from the toner container and a second supply hole for receiving the anti-missing agent supplied from the anti-missing agent container. ,
In the supply operation of the anti-missing agent through the second supply hole, replenishment for determining whether or not the anti-missing agent needs to be supplied based on the consumption amount of toner supplied from the developing device main body onto the photosensitive drum. A developing device controlled by a control means.

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