JP2006343647A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of replacing deteriorated toner while suppressing the occurrence of a time for allowing an image output operation not to be performed. <P>SOLUTION: The image forming apparatus 100 includes; an image carrier 111; a developing device 1 for developing an electrostatic image formed on the image carrier 111 with toner; a supply means 40 for supplying the toner to the developing device 1. The developing device 1 has a discharge port 8 through which the toner in the developing device 1 is discharged with the toner supply operation by the supply means 40, and the image forming apparatus 100 is provided with a first supply mode where the toner corresponding to the toner consumption accompanying the developing operation by the developing device 1 is replenished from the supply means 40 to the developing device 1, and a second supply mode where the toner is supplied from the supply means 40 to the developing device 1 so that the supply ratio of the toner supplied from the supply means 40 in accordance with the toner consumption accompanying the developing operation by the developing device 1 in the second supply mode may become larger than that in the first supply mode. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that forms an image using an electrophotographic system or an electrostatic recording system, and more particularly to an image forming apparatus characterized by a toner replenishing method for a developing device.

  In general, a developing device provided in an image forming apparatus such as a copying machine, a printer, a FAX, or a multifunction machine having a plurality of functions for forming an image using an electrophotographic method or an electrostatic recording method includes toner particles. And a two-component developer mainly composed of carrier particles. In particular, in a color image forming apparatus that forms a full-color or multi-color image, most of the developing devices use a two-component developer.

  As is well known, the toner concentration of this two-component developer (that is, the ratio of the weight T of toner particles to the total weight D of carrier particles and toner particles, hereinafter also referred to as “T / D ratio”) is the image quality. It is an extremely important factor in stabilizing The toner particles of the two-component developer are consumed during development, and the toner density changes. Therefore, a developer replenishing device comprising developer concentration detecting means for detecting the toner concentration of the two-component developer in the developing device, and control means for causing the developing device to replenish toner in accordance with the detected signal. To maintain the toner concentration of the two-component developer constant.

  Conventionally, there are the following methods as the developer replenishing device. In other words, a two-component developer is used (a developer reflected light detection method) that uses a toner concentration detection sensor of an optical reflection light amount detection method that detects the toner density by irradiating light to the two-component developer and receiving the reflected light amount. A method (inductance detection method) using an inductance detection type toner concentration detection sensor that detects the toner concentration by detecting the inductance of the agent is known. Further, a patch-like electrostatic image corresponding to a predetermined density is formed on an image carrier such as an electrophotographic photosensitive member, and a control reference image (patch image) which is a patch-like toner image obtained by developing the electrostatic image. There is also a method in which the toner density is detected by a toner density detection sensor of an optical reflection light quantity detection system (patch detection system). Regardless of which method is used, the toner concentration detection sensor calculates the toner concentration fluctuation amount of the two-component developer, converts this to the toner replenishment amount (replenishment time), and replenishes a predetermined amount of toner from the toner replenishment tank. (For example, refer to Patent Document 1).

  That is, FIG. 8 and FIG. 9 show an example of a conventional developing device 1 provided with a toner density detection sensor of an optical reflection light quantity detection method. The developing device 1 disposed opposite to the image carrier 111 such as a photoconductor and a dielectric has a developing container 10, and the inside thereof is a developing chamber (first chamber) by a partition wall 4 extending in the vertical direction. 2 and a stirring chamber (second chamber) 3. The upper part of the partition wall 4 is open, and the two-component developer that has become excessive in the developing chamber 2 is collected on the stirring chamber 3 side. The developing chamber 2 and the agitating chamber 3 contain a two-component developer (developer) including a non-magnetic toner (toner) and a magnetic carrier (carrier). In the developing chamber 2 and the stirring chamber 3, first and second screws 12 and 13, which are screw-type developer stirring and conveying members, are arranged, respectively. The developer is circulated and conveyed through the developing container 10 by the first and second screws 12 and 13. The developing chamber 2 is opened at a position corresponding to the developing area facing the image carrier 111, and the developing sleeve 5 as a developer carrier can be rotated so as to be partially exposed to the opening 6. Has been placed. Inside the developing sleeve 5, a magnet 8 as a magnetic field generating means is fixed. The developing sleeve 5 carries and conveys a layer of two-component developer whose layer thickness is regulated by the blade 11, and develops the developer by adhering the developer to the latent image of the image carrier 11 in a development region facing the image carrier 111.

  The toner concentration detection sensor 20 of the optical reflected light amount detection method includes, for example, an LED 21 as a light emitting element and, for example, a photodiode 22 as a light receiving element. Light is emitted from the LED 21 to the two-component developer carried on the developing sleeve 5, and the reflected light whose reflection amount changes according to the change in the toner amount is detected by the photodiode 22 and converted into an electrical signal. Then, the difference between the signal value and the reference value is taken, and an amount of developer, that is, toner determined according to the difference is supplied from the supply port 7 to the stirring chamber 3. In order to correct the change of the output value due to the temperature change of the light emitting element and the light receiving element, a bidirectional light emitting type LED and two photodiodes are used, and the direct light from this LED is received by the second photodiode. In many cases, the detected output is used as a reference signal.

  10 and 11 show an example of a conventional developing device provided with an inductance detection type toner density detection sensor. The toner density detection sensor of the inductance detection system is installed at a fixed place of developer flow and compression on the side surface and bottom surface of the developer container 10 where the change in inductance can be detected stably. Further, since it detects a change in toner density, it is installed downstream of the developing chamber 2. Therefore, normally, an inductance detection type toner density detection sensor (inductance head) 28 is installed on the bottom surface of the developing device downstream of the developing chamber 2. And the inductance which changes according to the change of the toner amount of the two-component developer is detected, and the toner density is detected.

  As shown in FIG. 12, in the patch detection method, a patch-like electrostatic image corresponding to a predetermined density is formed on the image carrier 11 and developed to develop a patch-like control reference. An image (reference image) 30 is assumed. Then, the control reference image 30 is irradiated with light from the LED 32 of the toner density detection sensor 31 of the optical reflection light quantity detection method as described above, and the reflected light is received by the photodiode 33 to thereby adjust the density of the control reference image 30. Detect. This density corresponds to the toner density of the two-component developer in the developing device 1. From this, the detected density is compared with a reference value, a difference is calculated, and the toner density fluctuation amount is calculated from the difference, converted into a toner supply amount (replenishment time), and a predetermined amount from the toner supply tank. Replenish toner.

  Further, there is also known a method (video count method) in which an image information signal is added to predict a toner consumption amount, and toner is replenished sequentially based on the estimated consumption amount.

  The developer reflected light detection method, inductance detection method, patch detection method, and video count method described above may be used in combination of at least two of them.

  On the other hand, conventionally, a method is known in which a developing device (mainly a carrier) is saved by replacing a developing device (mainly a carrier) by supplying a carrier together with toner (see Patent Document 2). This is called a trickle structure or the like, and a carrier replenishing device and a toner replenishing device are provided separately or integrally with the developing device, and a developer overflow portion is provided on the side wall of the housing (developing container) of the developing device, A new developer is replenished little by little by a replenishing device, and an old developer (mainly carrier) is automatically discharged from the developer leakage portion.

  By the way, in the conventional image forming apparatus, the image ratio is as low as 5%, for example, when the whole surface solid image (the image having the highest density level in the entire image forming area) is set to 100%, and the toner consumption amount is small. When the image is continuously output, there is a problem in that the image quality is deteriorated such as the deterioration in the low density portion and the decrease in the density.

  “Deterioration of roughness” means that the developing device is driven without replacement of the toner in the developing device, so that the external additive added to the toner is embedded in or released from the toner, causing the toner to deteriorate. It occurs by doing. That is, “deterioration of roughness” occurs when toner is classified and developability and transferability deteriorate. In addition, the toner charge-up occurs when the toner in the developing device is hardly replaced and the charge accumulation amount of the toner increases. This toner charge-up causes a decrease in density.

  Therefore, conventionally, there are means for judging the size of the image ratio and means for forcibly consuming the toner without outputting it as an image, and forcibly consuming the toner when the image ratio is lower than a predetermined value. An image forming apparatus is known (see Patent Document 3). As shown in FIG. 13, the number of output images is set (S201), and when image formation is started (S202), the input image data is read (S203), and the image ratio is calculated (S204). Next, one image is output (S205, 206). If the image ratio is equal to or less than the predetermined value (S207), a latent image is formed and developed over the entire axial direction of the photosensitive drum so as to consume a predetermined amount of toner, and a corresponding amount of toner is supplied (S208). ). If the number of output images has not reached the designated number (S209), the above process is repeated. If the number has reached the designated number, the image formation is terminated (S210).

  As described above, conventionally, image deterioration is prevented by control that forcibly consumes (discharges) toner when the image ratio is lower than a predetermined value.

However, according to such conventional control, particularly when speeding up the image output, the time during which the image output operation cannot be performed, so-called down time, may be a problem.
JP-A-5-303280 Japanese Patent Publication No. 2-21591 JP-A-9-34243

  An object of the present invention is to provide an image forming apparatus capable of replacing deteriorated toner while suppressing occurrence of time during which an image output operation cannot be performed.

  The above object is achieved by the image forming apparatus according to the present invention. In summary, the present invention includes an image carrier, a developing device that develops an electrostatic image formed on the image carrier with toner, and a replenishing unit that replenishes toner to the developing device. In the image forming apparatus having a discharge port through which the toner in the developing device is discharged in accordance with the toner replenishing operation from the replenishing unit, the developing device is an amount corresponding to the amount of toner consumed in the developing operation of the developing device. The first replenishment mode in which the toner is replenished to the developing device from the replenishing means, and the ratio of the toner replenishing amount from the replenishing means to the toner consumption amount associated with the developing operation of the developing device is the first replenishing mode. And a second replenishment mode in which toner is replenished from the replenishing unit to the developing device so as to be larger than the ratio in the mode.

  According to the present invention, it is possible to replace deteriorated toner while suppressing occurrence of time during which an image output operation cannot be performed.

  The image forming apparatus according to the present invention will be described below in more detail with reference to the drawings.

Example 1
[Overall Configuration and Operation of Image Forming Apparatus]
First, the overall configuration and operation of the image forming apparatus of this embodiment will be described with reference to FIG. FIG. 1 shows a schematic cross section of an image forming apparatus 100 of the present embodiment. The image forming apparatus 100 according to the present exemplary embodiment is a multifunction machine having both a copying function, a printer function, and a FAX function, and includes a printer unit 110 that performs image forming processing on a recording material, and an image reading apparatus 120. (Main unit). A full-color image is formed by an electrophotographic method in accordance with document image information read by the image reading device 120 or an image information signal from an external device such as a personal computer or a digital camera connected to the device main body so as to be communicable. can do.

  The printer unit 110 includes first, second, third, and fourth image forming units for forming images of toners of yellow, magenta, cyan, and black, respectively, as a plurality of image forming units serving as image forming units. There are four image forming portions of portions Sa, Sb, Sc, and Sd.

  In other words, the printer unit 110 is provided with four cylindrical electrophotographic photosensitive members as image carriers, that is, photosensitive drums 111a, 111b, 111c, and 111d. Each of the four photosensitive drums 111a to 111d is provided with a developing device 1a, 1b, 1c, 1d loaded with a developer having a different spectral characteristic. In this embodiment, the developing device 1 is loaded with a two-component developer (developer) used by mixing toner and carrier. The image forming portions Sa to Sd including the combination of one photosensitive drum and one developing device are arranged along the surface movement direction of the intermediate transfer belt 131 as an intermediate transfer member provided in the intermediate transfer unit 130 as a transfer device. They are arranged in series.

  In this embodiment, the basic configuration and operation of each image forming unit are substantially the same. Therefore, in the following, when there is no need to distinguish between them, the subscripts a, b, c, and d given to the reference numerals to indicate that they are elements for any color will be omitted and described collectively.

  In the image forming unit S, a drum-shaped photoconductor (photosensitive drum) 111 as an image carrier is supported so as to be rotatable in the direction of an arrow in the figure. Around the photosensitive drum 111, a corona charger 112 as a charging unit for charging the photosensitive drum 111, a laser exposure optical system 113 as an exposure unit that scans and exposes the photosensitive drum 111 according to image information, and a photosensitive drum 111. A developing device 1 as a developing unit that supplies toner and forms a toner image, a primary transfer roller 132 as a primary transfer unit disposed opposite to the photosensitive drum 111 via an intermediate transfer belt 131, and the photosensitive drum 111 A cleaner 114 is disposed as a cleaning means for collecting toner.

  The intermediate transfer belt 131 as an intermediate transfer member is wound around three rollers of a driving roller 133, a driven roller 134, and a secondary transfer counter roller 135 in this embodiment as a plurality of rollers. When the driving force is transmitted to the driving roller 133, the intermediate transfer belt 131 rotates in the direction indicated by the arrow in the drawing. The photosensitive drums 111a to 111d are arranged so as to face a transfer surface, which is the same plane portion formed on the intermediate transfer belt 131 by being stretched by two rollers 133 and 134. In addition, primary transfer rollers 132a to 132d as primary transfer units are disposed at portions facing the respective photosensitive drums 111a to 111d with the intermediate transfer belt 131 interposed therebetween. At the position of the primary transfer roller 132, the intermediate transfer belt 131 comes into contact with the photosensitive drum 111, and a primary transfer portion (primary transfer nip) N1 is formed. A secondary transfer roller 136 as a secondary transfer unit is disposed at a position facing the secondary transfer counter roller 135 via the intermediate transfer belt 131. The secondary transfer roller 136 contacts the intermediate transfer belt 131 to form a secondary transfer portion (secondary transfer nip) N2. The intermediate transfer unit 130 is configured by the intermediate transfer belt 131, the primary transfer roller 132, the belt stretching rollers 133, 134, 135, the secondary transfer roller 136, and the like.

  For example, when a full color image is output, the photosensitive drums 111a to 111d of the image forming units Sa to Sd rotate in the direction of the arrow shown in the drawing. The rotating photosensitive drum 111 is uniformly charged by the charger 112. Next, for example, according to the image information read by the image reading device 120, a light image is irradiated on each photosensitive drum 111 for each separated color. Thereby, an electrostatic image (latent image) is formed on each photosensitive drum 111.

  The electrostatic image formed on the photosensitive drum 111 is reversely developed by the developing device 1. That is, in this embodiment, the toner charged to the same polarity as the charged polarity of the surface of the photosensitive drum 111 adheres to the image portion (exposed portion) whose charge is attenuated by exposure, and the resin and the pigment are put on the photosensitive drum 111. A developer image (toner image) is formed as a substrate. At this time, a developing bias is applied to the developing device.

  The toner image formed on the photosensitive drum 111 is transferred (primary transfer) onto an intermediate transfer belt 132 as a transfer medium (transfer body) by a primary transfer roller 132. At this time, the primary transfer roller 132 has a polarity opposite to the normal charging polarity (negative polarity in this embodiment) of the toner from a primary transfer bias power source (not shown) as a primary transfer bias output unit. A primary transfer bias is applied.

  At the time of full color image output, the above-described operation is performed in the first, second, third, and fourth image forming units Sa to Sd. Then, the toner images formed on the photosensitive drums 111 a to 111 d in the respective image forming units Sa to Sd are sequentially primary transferred onto the intermediate transfer belt 131 so as to be superimposed on the intermediate transfer belt 131. As a result, a full color toner image is formed on the intermediate transfer belt 131.

  Thereafter, the full-color toner image on the intermediate transfer belt 131 is collectively transferred (secondary transfer) to the recording material P at the secondary transfer portion N2. At this time, a secondary transfer bias having a polarity opposite to the normal charging polarity of the toner is applied to the secondary transfer roller 135 by a secondary transfer bias power source (not shown) as a secondary transfer bias output unit.

  The recording material P is conveyed from the recording material supply unit 140 to the secondary transfer unit N2. That is, in the recording material supply unit 140, the recording material P stored in the recording material storage unit (cassette) 141 is sent out one by one by a pickup roller 142 as a recording material supply unit. Next, the recording material S is conveyed to the secondary transfer portion N2 by the registration roller 143 at a desired timing.

  The recording material P onto which the toner image has been transferred by the secondary transfer unit N2 passes through the transport unit and is transported to a heat roller fixing device 150 serving as a fixing unit. The toner image is fixed on the recording material P by the fixing device 150. Thereafter, the recording material P is discharged to a discharge tray or a recording material post-processing device (not shown).

  When images are formed on both surfaces of the recording material P, an image is automatically formed on the second surface of the recording material P on which the image is formed on the first surface by a double-sided image forming unit (not shown). It is possible. That is, immediately after the recording material P passes through the fixing device 150, the conveyance path switching guide is driven, and the recording material P is once guided to the reverse path through the conveyance vertical path. Thereafter, the recording material P is retreated from the reversing path in the direction opposite to the feeding direction with the rear end when the recording material P is fed into the reversing path as the head by the reverse rotation of the reversing roller, and is sent to the double-sided conveyance path. Thereafter, the recording material P is passed through a double-sided conveyance path, skew correction and timing are performed by a double-sided conveyance roller, and conveyed to a registration roller at a desired timing. Then, the image is transferred again to the second surface of the recording material P by the above-described image forming process, and then fixed.

  The transfer residual toner remaining on the intermediate transfer belt 131 after the secondary transfer process is cleaned by the transfer cleaning device 137. Thereby, the intermediate transfer belt 131 is again subjected to the primary transfer process in each of the image forming portions Sa to Sd. That is, the intermediate transfer belt 131 is driven by the drive roller 133 upstream of the first image forming unit Sa (downstream of the secondary transfer unit) in the moving direction. A transfer cleaning device 137 is detachably disposed at a position facing the drive roller 133 with the intermediate transfer belt 131 interposed therebetween. The transfer cleaning device 137 provided so as to face the drive roller 133 is pressurized toward the drive roller 133 that faces the transfer roller 133 after the toner images for the necessary colors are overlaid on the intermediate transfer belt 131. Then, the transfer cleaning device 137 cleans the transfer residual toner remaining on the intermediate transfer belt 131 after the toner image is transferred to the recording material P. After the cleaning is completed, the transfer cleaning device 137 is separated from the intermediate transfer belt 131.

  Further, of the driving roller 133 and the driven roller 134 that form the transfer surface of the intermediate transfer belt 131, toner on the intermediate transfer belt 131 is placed at a position facing the driven roller 134 that is downstream in the moving direction of the intermediate transfer belt 131. A sensor 138 for detection is arranged. The sensor 138 detects the positional deviation and density of images transferred from the photosensitive drums 111a to 111d of the image forming units Sa to Sd.

[Developer]
Next, the developing device 1 used in this embodiment will be described with reference to FIGS.

  The developing device 1 disposed opposite to the photosensitive drum 111 has a developing container 10, and the inside thereof has a developing chamber (first chamber) 2 and a stirring chamber (second chamber) by a partition wall 4 extending in the vertical direction. ) It is divided into three. The upper part of the partition wall 4 is open, and the two-component developer that has become excessive in the developing chamber 2 is collected on the stirring chamber 3 side. The developing chamber 2 and the agitating chamber 3 contain a two-component developer (developer) including a non-magnetic toner (toner) and a magnetic carrier (carrier).

  The developing chamber 2 and the stirring chamber 3 are respectively provided with first and second screws 12 and 13 which are screw type developer stirring and conveying members. The first screw 12 stirs and conveys the developer in the developing chamber 2. The second screw 13 agitates and conveys the toner supplied via the replenishing port 7 provided at the upper portion of the second screw 13 and the developer already in the agitating chamber 3, and the toner concentration To equalize. The replenishing port 7 is disposed in the vicinity of the upstream end in the developer conveyance direction in the stirring chamber 3.

  Developer passages 14 and 15 are formed at both ends of the partition wall 4 in the longitudinal direction so that the developing chamber 2 and the stirring chamber 3 communicate with each other. Due to the conveying force of the first and second screws 12 and 13 in the directions of arrows A and B, the developer in the developing chamber 2 in which the toner is consumed due to the development and the toner concentration is reduced is discharged from one passage 14 through the stirring chamber. Move into 3. Further, the developer whose toner concentration has been recovered in the stirring chamber 3 moves from the other passage 15 into the developing chamber 2 by the conveying force of the first and second screws 12 and 13 in the directions of arrows A and B. . Thus, the developer is circulated and conveyed in the developing container 10.

  The developing chamber 2 is opened at a position corresponding to the developing area facing the photosensitive drum 111, and a developing sleeve 5 as a developer carrying member is rotatably disposed so as to be partially exposed to the opening 6. ing. The developing sleeve 5 is made of a nonmagnetic material, and rotates in the direction of the arrow C in the drawing operation. That is, in this embodiment, the developing sleeve 5 and the photosensitive drum 111 rotate so that the surface movement directions of the developing sleeve 5 and the photosensitive drum 111 are the same. Inside the developing sleeve 5, a magnet (magnet roll) 8, which is a magnetic field generating means, is fixed to the developing container 10.

  The developing sleeve 5 carries and transports a two-component developer layer whose layer thickness is regulated by a blade 11 as a developer regulating member. Then, in the developing region facing the photosensitive drum 111, a developer spike (magnetic brush) formed on the developing sleeve 5 is brought close to or in contact with the photosensitive drum 111 by a magnetic field generated by the magnet 8. As a result, the toner in the developer adheres to the photosensitive drum 11 in accordance with the electrostatic image on the photosensitive drum 111 and is developed. In order to improve the development efficiency, that is, the application rate of toner to the latent image, a development bias voltage in which a DC voltage and an AC voltage are superimposed is applied to the development sleeve 5 from a power source 14 as a development bias output means. .

  Further, as will be described in detail later, the toner in the developing devices 1a to 1d of the image forming units Sa to Sd is supplied with supply mechanisms 40a, 40b, 40c, and 40d as supply means provided for each color (FIG. 1). The toner concentration (or toner amount) in the developing device 1 is normally kept constant from the replenishing tanks (hoppers, replenisher storage units) 41a, 41b, 41c, 41d of the developing container 10 through the replenishing port 7 of the developing container 10. It is replenished from time to time at appropriate timing.

  In this embodiment, the carrier is supplied together with the toner from the supply mechanism 40 to the developing device 1. In particular, in this embodiment, the replenishment mechanism 40 replenishes the developing device 1 with a replenisher in which toner and a carrier are mixed in advance. However, the toner and the carrier may be replenished separately at a predetermined ratio. The developer increased in the developing container 10 is discharged from the developing container 10 by a so-called trickle structure. That is, the developing device 1 is disposed near the second screw 13, more specifically, at a predetermined height position on the side wall of the developing container 10 in the vicinity of the downstream end of the developer in the stirring chamber 3. It has. When the replenishment agent including toner and carrier is replenished from the replenishment port 7 and the volume of the developer in the developing container 10 is increased, the discharge port 8 is set so that the amount of the developer in the developing container 10 becomes a predetermined amount. The developer is discharged from. Thereby, the amount (height) of the developer in the developing container 10 is kept constant.

  By replenishing the carrier together with the toner from the replenishing mechanism 40 to the developing device 1, normally, new developer is replenished little by little, and mainly the old developer (mainly carrier) is automatically supplied from the discharge port 8. Are exhausted. For this reason, the trouble of replacing the developer (mainly carrier) deteriorated due to durability can be saved. Further, as will be described in detail later, by providing the discharge port 8, it is possible to perform control for promoting the replacement of toner when forming an image with a low image ratio while suppressing the occurrence of downtime. It has become.

  The developer discharged from the discharge port 8 is accommodated in a collection container (not shown), and is taken out from the image forming apparatus 100 together with the collection container or transferred to another container at an appropriate time.

[Developer supply]
Conventionally, in a developer replenishing device, for example, a toner concentration detection sensor using an optical reflection light amount detection method or an inductance detection type toner concentration detection sensor that detects the toner concentration by detecting the inductance of a two-component developer is used. Is detected. Then, the toner replenishment amount is adjusted based on the detection signal value of the toner concentration detection sensor, and control is performed so as to make the toner concentration constant.

  However, as described above, when images with a low image ratio are output continuously, the amount of toner consumed is small, the amount of replenished toner is reduced, and the same toner is conveyed in the developing device. For this reason, toner deterioration and charge up of the toner tribo (charged charge amount) due to an increase in the number of contacts occur. In addition, image defects such as deterioration of toner due to toner deterioration and density reduction due to toner charge-up occur.

  In order to solve the above-described problems, there has been a system in which toner replacement is frequently performed by providing a toner consumption mode in which toner is forcibly consumed (discharged). However, in such a method, particularly in a high-speed image forming apparatus, a time during which an image output operation cannot be performed, so-called down time, may be a problem.

  That is, one of the objects of the present invention is to suppress the occurrence of time during which an image output operation cannot be performed, suppress toner charge-up and deterioration, and suppress image defects such as deterioration of roughness and decrease in density. An image forming apparatus is provided.

  Therefore, in this embodiment, in the image forming apparatus 100, the developing device 1 has the discharge port 8 through which the toner in the developing device 1 is discharged in accordance with the toner replenishing operation from the replenishing mechanism 40. As operations, a first replenishment mode (normal replenishment mode) in which an amount of toner corresponding to the amount of toner consumed by the developing operation of the developing device 1 is replenished from the replenishing mechanism 40 to the developing device 1, and a developing operation of the developing device 1 The toner is replenished from the replenishing mechanism 40 to the developing device 1 so that the ratio of the toner replenishing amount from the replenishing mechanism 40 to the toner consumption accompanying the increase is greater than the ratio in the first replenishing mode (normal replenishing mode). 2 replenishment modes (forced replenishment mode). In the normal replenishment mode, a replenisher containing toner and carrier is replenished to the developing device 1 from the replenishment mechanism 40 according to information corresponding to the toner consumption. In the forced replenishment mode, a replenisher containing toner and carrier is replenished to the developing device 1 from the replenishment mechanism 40 so that more toner than the toner consumption amount is replenished.

  At least in the forced supply mode, excess toner is discharged from the discharge port 8 as the toner is supplied from the supply mechanism 40 to the developing device 1. In this embodiment, since the carrier is supplied together with the toner, the carrier is discharged from the supply port 8 together with the excess toner. In the forced replenishment mode, toner can be replenished from the replenishment mechanism 40 to the developing device 1 regardless of the amount of toner consumed by the developing device 1. Alternatively, in the forced replenishment mode, the toner can be replenished from the replenishment mechanism 40 to the developing device 1 such that the smaller the toner consumption by the developing device 1 is, the larger the ratio of the replenishing amount to the toner consumption is.

  Further, in this embodiment, switching between the normal supply mode and the forced supply mode, that is, switching of the ratio of the supply amount to the toner consumption amount is determined based on the video count number of the density signal of the image information signal. More specifically, in this embodiment, the toner consumption amount is the forced supply mode when the predicted toner consumption amount for one output image is less than a predetermined value, and the predicted toner consumption amount is the predetermined value. In the above case, the toner is supplied from the supply mechanism 40 to the developing device 1 in the normal supply mode. This toner consumption amount prediction value is obtained from the video count number of the density signal of the image information signal. In particular, in this embodiment, the image ratio in one output image corresponding to the predicted toner consumption amount for one output image is calculated from the video count number. The developer supply operation is executed in the forced supply mode when the image ratio is less than the predetermined value, and in the normal supply mode when the image ratio is equal to or higher than the predetermined value. This will be described in more detail below.

[Toner consumption estimation means]
FIG. 4 shows a schematic control block of the image forming apparatus of this embodiment. The image forming apparatus 100 according to the present exemplary embodiment includes a toner consumption amount estimation unit that estimates a toner amount consumed by the developing device 1 by a toner image forming operation. First, the toner consumption amount estimation means will be described.

  At the time of image output, for example, an image of a document is read by the image reading device 120, and the obtained analog image signal is input to the image processing unit 163. In the image processing unit 163, the analog image signal is converted into a digital image signal by, for example, 8 bits (0 to 255 gradations) by an A / D converter. This digital image signal is γ-corrected by a density gradation correction unit included in the image processing unit using a γ correction table (in this embodiment, density conversion is performed using a lookup table (LUT) method) 166. Thereafter, the data is input to the image formation control unit 162. Thus, the analog image signal is converted into a pixel image signal which is a digital image signal having an output level corresponding to the density of the pixel for each pixel.

  The image formation control unit 162 comprehensively controls the operation of each unit of the image forming apparatus 100 and controls a laser light emitting element (such as a semiconductor laser) (not shown) included in the laser exposure optical system 3 to form an electrostatic latent image. The laser for is emitted. The pixel image signal input to the image formation control unit 162 is transmitted to a pulse width modulation circuit included in the image formation control unit 162. This circuit generates, for each pixel image signal, a laser driving pulse having a width (time length) corresponding to the level. That is, a wider driving pulse is formed for the high density pixel, a narrower driving pulse is formed for the low density pixel, and an intermediate driving pulse is formed for the medium density pixel. The semiconductor laser is driven to blink by the drive pulse. Therefore, the semiconductor laser is lit for a longer time for high density pixels and for a shorter time for low density pixels. Therefore, the photosensitive drum 111 is exposed to a longer range in the main scanning direction for high density pixels. That is, the dot size of the latent image is different according to the pixel density. Therefore, as a matter of course, the toner consumption for the high density pixel is larger than that for the low density pixel.

  In this embodiment, the amount of toner consumed by the developing device 1 in the image output operation is estimated by a video count method. That is, the video counter 164 as a toner consumption amount estimation unit usually measures the laser lighting time for each output image, and estimates the toner consumption amount from the measured value.

  More specifically, the video counter 164 accumulates the number of clock pulses corresponding to the width of each laser drive pulse generated by the pulse width modulation circuit, that is, the number of clock pulses corresponding to the density of each pixel. . Here, this integrated value is called the video count number of the output image. The number of video counts integrated for one output image corresponds to the amount of toner consumed by the developing device 1 to form one output image.

  Further, the ratio (percentage display) of the video count number of each image to the video count number of the entire solid image (image in which the entire imaging area is the highest density level) is called an image ratio of the image. The image ratio is calculated by the replenishment control unit 161 as a control unit. Naturally, the image ratio calculated for one output image corresponds to the amount of toner consumed by the developing device 1 to form one output image.

[Developer replenishment operation]
Next, the developer supply operation in this embodiment will be described. In the present embodiment, the developer replenishment operation for each developing device 1 provided in the plurality of image forming units Sa to Sd is the same. The developer replenishing operation for each developing device 1 may be performed independently or in conjunction.

-Normal replenishment mode-
In the present embodiment, the replenishment control unit 161 serving as a control unit calculates an image ratio from the video count number obtained by the video counter 164, and the image ratio is equal to or greater than a predetermined value, in particular, 5% or greater in the present embodiment. In some cases, the developer supply operation is executed in the normal supply mode.

  More specifically, the supply control unit 161 calculates the image ratio based on the video count every time the image output operation for one recording material P is completed. Then, when the calculated image ratio is 5% or more, the replenishment control unit 161 is predetermined with respect to the toner consumption amount predicted from the video count number at the previous image output operation in the next image output operation. The replenisher is replenished from the replenishing mechanism 40 to the developing device 1 at a ratio of (approximately 1: 1). That is, in the normal replenishment mode, the replenishment control unit 161 causes the replenishment mechanism 40 to replenish the replenishment agent from the replenishment mechanism 40 so that toner corresponding to the predicted toner consumption is replenished.

  That is, in this embodiment, the replenishing mechanism 40 includes a replenishing tank 41, a replenishing screw 42 as a replenishing member that replenishes the developing device 1 with a replenisher containing toner and carrier in the replenishing tank 40, and a replenishing screw 42. And a motor 43 as a driving means for transmitting a driving force. The replenishment control unit 161 calculates the rotation driving time of the replenishment screw 42 necessary for replenishing the developing device 1 with an amount of toner corresponding to the toner consumption amount. Then, the replenishment control unit 161 sends a control signal to the motor 43 so as to drive the motor 43 for that time. Therefore, when the video count number is large, the driving time of the motor 43 is longer, and when the video count number is small, the driving time of the motor 43 is shorter.

-Forced replenishment mode-
On the other hand, the replenishment control unit 161 calculates the image ratio from the video count number obtained by the video counter 164, and when the image ratio is less than a predetermined value, particularly less than 5% in this embodiment, forced replenishment. The developer supply operation is executed in the mode.

  FIG. 5 shows an example of the relationship (replenishment table) between the image ratio (corresponding to the predicted toner consumption amount for one output image) and the toner replenishment amount calculated based on the video count. . That is, in the present embodiment, the replenishment control unit 161 sets the ratio of the replenishment amount ratio to the toner consumption amount when the image ratio in one output image is less than 5% when the full-color image is 100%. As shown in FIG. 5, the consumption amount is set so as to satisfy the replenishment amount. In this embodiment, as shown in FIG. 5, toner corresponding to an image ratio of 5% is supplied regardless of the calculated image ratio (that is, toner consumption) in one output image. In consideration of ease of toner charge-up, the ratio of the replenishment amount to the toner consumption amount may be increased as the calculated image ratio in one output image is lower.

  In this way, the T / D ratio of the developer in the developing device 1 is set high, and the replenisher replenishment amount is forcibly increased. Thereby, it is possible to prevent the same toner from circulating in the developing device 1 and to prevent charge-up and deterioration of the toner.

  Here, in the image forming apparatus 100 according to the present exemplary embodiment, when the estimated toner consumption is small, particularly when the image ratio is less than 5%, the developer is the same as when the image ratio is 5% or more. When the replenishment operation is performed, the speed of charge-up and deterioration of the toner that causes the image defect is remarkably increased. For this reason, in this embodiment, the predetermined image ratio (threshold value) that determines execution of the developer supply operation in the forced supply mode is set to 5%. However, the present invention is not limited to this, and an optimal image ratio threshold may be selected according to the configuration of the image forming apparatus.

  In this embodiment, the replenishment control unit 161 calculates the image ratio based on the video count number of the density signal of the image information signal for each image output operation for one recording material P. Then, when the calculated image ratio is less than 5%, the replenishment control unit 161 increases the amount of toner that is larger than the toner consumption estimated from the video count during the previous image output operation at the next image output operation. In this embodiment, the replenisher is replenished to the developing device 1 from the replenishment mechanism 40 so that the toner corresponding to the image ratio of 5% is replenished regardless of the toner consumption amount.

  The developer increased in the developing device 1 is discharged by the trickle configuration. That is, when the replenishment agent including toner and carrier is replenished from the replenishing port 7 and the developer in the developer container 10 becomes a predetermined amount or more, the developer in the developer container 10 becomes a predetermined amount. The developer is discharged from the discharge port 8.

  Here, the toner concentration in the replenishing agent, that is, the ratio of the weight of the toner in the replenishing agent to the weight of the replenishing agent is preferably 50% or more. However, as will be described later, the present invention can be applied to a system that substantially replenishes only toner as a replenisher, for example, a system that uses a one-component developer. That is, the ratio of the weight of the toner in the replenisher to the weight of the replenisher is preferably 50% or more and 100% or less.

  Since the developing device 1 has a trickle configuration, even if the developer in the developing device 1 increases due to an increase in the T / D ratio, the developing device 1 is immediately discharged from the discharge port 8. When the developing device 1 does not have a trickle configuration, the developer is clogged and the screw is locked due to packing, or the stirrability of the replenished toner is decreased due to an increase in the developer amount, and the fog phenomenon (to the toner) There is an adverse effect such as a phenomenon in which toner adheres to non-image portions due to insufficient charging.

  As described above, in this embodiment, when the image ratio of the output image is low and the toner consumption is small, the T / D ratio of the developer in the developing device 1 is set high, but the developer is always supplied and discharged. Is done. As a result, toner charge-up is reduced and toner deterioration can be prevented. Further, the transition of the T / D ratio of the developer in the developing device 1 to a high level itself leads to a reduction in stress on the toner in the vicinity of the blade 11. Therefore, a large amount of toner with respect to the carrier also leads to suppression of toner charge-up.

[Density gradation correction]
Furthermore, in this embodiment, by executing the developer replenishment operation in the forced replenishment mode, the image density variation due to the increase in the T / D ratio of the developer in the developing device 1 is detected, and the density and gradation of the output image are adjusted. Correction is performed by density gradation correction control to be corrected. In this embodiment, a control reference image is formed on the photosensitive drum 111 in response to the supply of toner from the supply mechanism 40 to the developing device 1 in the forced supply mode. Then, based on the result of detecting the toner amount of the reference image for control, a γ correction table is determined as a density / tone correction means for determining a rule for correcting the density / tone of the output image.

  More specifically, as shown in FIGS. 4 and 12, the image forming apparatus 100 according to the present embodiment has an optical reflection amount detection type image density sensor 31 as an image density detection unit facing each photosensitive drum 111. . The image density sensor 31 includes, for example, an LED 32 as a light emitting element and, for example, a photodiode 33 as a light receiving element.

  In response to the execution of the developer replenishment operation in the forced replenishment mode, an electrostatic image (patch latent image) having a predetermined potential is formed on the photosensitive drum 111, and this latent image is subjected to predetermined development conditions. In this way, a patch-like control reference image (patch image) that is a pattern of a toner image having a reference density is formed. Light is emitted from the LED 32 of the image density sensor 31 to the patch image 30 formed on the photosensitive drum 111, and reflected light whose reflection amount changes according to the toner amount of the patch image 30 is detected by the photodiode 33 and converted into an electrical signal. Convert. This detection signal is input to the γ correction table determination unit 165 as density gradation correction table determination means.

  In this embodiment, the image information of the patch latent image is stored in a storage unit built in or connected to the γ correction table determination unit 165. The image formation control unit 162 uses this information to form the patch image 30 on the photosensitive drum 111. The toner loading amount of the patch image 30 is detected by the image density sensor 31. The patch image 30 may be single or plural. When a plurality of patch images are formed, patch images corresponding to different density levels can be formed.

  In this embodiment, a γ correction table (look-up table: LUT) corresponding to the applied toner amount, which is the density detection result of the patch image 30 by the image density sensor 31, is prepared in advance. Then, the detection result of the toner application amount of the patch image 30 is fed back, a γ correction table corresponding to the toner application amount of the patch image 30 is determined, and the density gradation characteristic of the output image is set to the toner application amount of the patch image 30. Change to the corresponding γ.

  In other words, the γ correction table defines a rule for correcting the density of the output image, and in this embodiment, the input signal level and the output signal level are related with 0 to 255 gradations. Using this γ correction table, the image processing unit 163 corrects the input image signal so that an ideal linear gradation characteristic is obtained in the output image, and the density of the image information signal for each image. A level signal is generated and sent to the image formation control unit 162. In this embodiment, a plurality of γ correction tables are stored in advance in a storage unit built in or connected to the γ correction table determination unit 165 in association with the detection result of the applied toner amount of the patch image 30. Then, the γ correction table determination unit 165 selects a γ correction table that corrects the deviation of the density tone characteristics when the patch image 30 is actually measured from the ideal density tone characteristics (straight line). To do.

  As a result, the image processing unit 163 uses the γ correction table 166 determined by the γ correction table determination unit 165, so that the density of the image information signal according to the T / D ratio of the developer in the current developing device 1. A level signal can be generated and sent to the image formation controller 162. Therefore, the density fluctuation of the output image due to the increase in the T / D ratio of the developer in the developing device 1 can be suppressed.

  As described above, according to this embodiment, the time during which the image output operation cannot be performed, that is, the so-called downtime, is suppressed, the toner charge-up and deterioration are suppressed, and the image defects such as the deterioration of the roughness and the density decrease are suppressed. can do.

Example 2
Next, another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus of the present embodiment are the same as those of the first embodiment. Accordingly, elements having the same or corresponding functions and configurations as those of the image forming apparatus according to the first exemplary embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In this embodiment, as the toner consumption amount, when the average toner consumption amount prediction value for a predetermined number of output images is less than the predetermined value, the forced replenishment mode is used, and when the average toner consumption amount prediction value is a predetermined value or more. In the normal supply mode, toner is supplied from the supply mechanism 40 to the developing device 1. This average toner consumption prediction value is obtained from the video count number of the density signal of the image information signal and the image output number. In particular, in this embodiment, the average image ratio converted per output image corresponding to the average toner consumption predicted value converted per output image is calculated from the video count number and the number of formed images. To do. The developer supply operation is executed in the forced supply mode when the average image ratio is less than a predetermined value, and in the normal supply mode when the average image ratio is equal to or higher than the predetermined value. Hereinafter, in particular, the forced supply mode in the present embodiment will be described in more detail.

  FIG. 6 shows a schematic control block of the image forming apparatus 100 of the present embodiment. In this embodiment, the image forming apparatus 100 includes a page counter 167 as an image output number detection unit. For example, the page counter 167 accumulates the number of image outputs each time an image output operation is performed on one recording material P from an image formation start instruction. The supply control unit 161 can read the number of image outputs accumulated by the page counter 167 at a predetermined timing. In this embodiment, the user designates an operation unit (operation panel) 168 provided in the image forming apparatus main body or an operation unit (not shown) of a device connected to the image forming apparatus main body so as to be communicable. Information regarding the number of formed images is input to the supply control unit 161.

Here, n is the cumulative image output number from the image formation start instruction (when the copy button is ON), and the cumulative image ratio of the image information signal determined on the basis of the video count number (the ratio of the whole solid image in one output image is (The integrated value of the image ratio when 100%) is a, the average image ratio converted per output image is the following formula:
Average image ratio (%) = a / 100 / n × 100
Is calculated by

Alternatively, when the image ratio of each image is α when the image ratio of the entire solid image is 100% in one output image, the average image ratio converted per output image is expressed by the following formula:
Average image ratio (%) = {(Σα / 100) / n} × 100
Is calculated by

  In this embodiment, the supply control unit 161 calculates the average image ratio from the integrated image output number n read from the page counter 167 at a predetermined timing and the video count number of each image read from the video counter 164. Alternatively, the replenishment control unit 161 calculates the average image ratio from the designated image forming number n input from the operation unit 168 and the video count number of each image read from the video counter 164.

  Then, when the average image ratio is less than 5, the replenishment control unit 161 supplies the toner to the developing device 1 from the replenishment mechanism 40 so that the toner is replenished more than the toner consumption predicted from the average image ratio. Supply replenisher. That is, when the average image ratio is less than 5%, the ratio of the replenisher replenishment amount to the calculated average image ratio (that is, the average toner consumption amount) is the same as that when the average image ratio is 5% or more. Make it larger than that ratio.

  In this way, the T / D ratio of the developer in the developing device 1 is set high, and the replenisher replenishment amount is forcibly increased. Thereby, it is possible to prevent the same toner from circulating in the developing device 1 and to prevent charge-up and deterioration of the toner.

  Here, the reason why the predetermined average image ratio (threshold) for deciding to execute the developer supply operation in the forced supply mode is set to 5% is the same as the reason described in the first embodiment.

  For example, it is assumed that 10 images with an image ratio of 5% are formed and then 10 images with an image ratio of 1% are formed. In this case, n = 20 and a = 60, and the average image ratio is 3%. FIG. 7 shows an example of the relationship between the replenishment table at this time, that is, the average image ratio (corresponding to the predicted average toner consumption amount) calculated based on the video count and the toner replenishment amount.

  A straight line L1 in FIG. 7 shows a replenishment table (linear) when the average image ratio is 5% or more (shown extending over less than 5%). A straight line L2 in FIG. 7 indicates a replenishment table (non-linear) with an average image ratio of less than 5%. At this time, in the present embodiment, the inclination of the straight line L2 takes into account the ease of charge-up, and the lower the calculated average image ratio, the difference in the replenishment amount from the straight line L1 (that is, the toner consumption amount). The ratio of the replenishing amount with respect to the amount) is set to be large. Note that the toner may be replenished at a ratio of the replenishment amount to the predetermined toner consumption amount regardless of the calculated average image ratio (that is, average toner consumption amount).

  In the above example, the integrated image output number n is 60, but the present invention is not limited to this, and changes depending on, for example, the configuration of the image forming apparatus, the developer, the environment, and the like. Further, the average image ratio (that is, average toner consumption) may be calculated for each image output job (a series of image output operations performed in response to one image output operation start instruction) for a plurality of recording materials P. Alternatively, it may be calculated for each predetermined number of image outputs.

  Also in the present embodiment, as in the first embodiment, the increased amount of developer in the developing device 1 is discharged by the trickle configuration. Also in the present embodiment, similarly to the first embodiment, the amount of applied toner of the patch image formed on the photosensitive drum 111 corresponding to the execution of the developer replenishment operation in the forced replenishment mode is detected. The γ correction table 166 is switched according to the result. As a result, the same effects as described in the first embodiment can be obtained.

  As described above, according to the present exemplary embodiment, as in the first exemplary embodiment, the time during which the image output operation cannot be performed, that is, the occurrence of so-called down time, is suppressed, the toner charge-up and deterioration are suppressed, Image defects such as lowering can be suppressed, and control of the developer replenishment amount is collectively performed for a plurality of image outputs, thereby simplifying the control.

  As mentioned above, although this invention was demonstrated according to the specific Example, it should be understood that this invention is not limited to the above-mentioned embodiment.

  4 and 6, the functional blocks of the image forming apparatus are schematically shown. However, the replenishment control unit 161, the image formation control unit 162, the γ correction table determination unit 165, the image processing unit 163, and the video counter 164 are illustrated. All or part of the page counter 167 or the like may be realized by one unit such as a controller (CPU or the like) including a storage unit, a calculation unit, and / or a control unit. Further, all or part of these functions may be a program executed by a unit such as a CPU.

  In each of the above embodiments, the developer replenishment amount itself in the normal replenishment mode and the forced replenishment mode is described as being controlled based on the video count. That is, in the normal replenishment mode, the replenisher is replenished to the developing device 1 from the replenishment mechanism 40 so that the toner corresponding to the toner consumption estimated from the video count number is replenished. In the forced replenishment mode, replenisher is replenished from the replenishment mechanism 40 to the developing device 1 so that more toner than the toner consumption estimated from the video count is replenished. However, the present invention is not limited to this. For example, the developer supply amount itself can be controlled by any one of the conventionally known developer reflected light detection method, inductance detection method, patch detection method, or a combination thereof.

  That is, as described above, the toner density of the developer in the developing device 1 is directly detected by the developer reflected light detection method or the inductance detection method, or the toner loading amount of the patch image is detected by the patch detection method. Thus, the toner concentration of the developer in the developing device 1 is indirectly detected. In the normal replenishment mode, the replenishment mechanism 40 supplies the developing device so that the toner corresponding to the estimated consumption is replenished based on the detection result (that is, the detected toner density is constant). 1 can be replenished. On the other hand, in the forced replenishment mode, development is performed from the replenishment mechanism 40 so that more toner than the estimated consumption is replenished based on the detection result (that is, the detected toner density is greater than a predetermined value). A replenisher can be supplied to the device 1.

  In each of the above embodiments, the detection result of the amount of applied toner of the patch image formed on the photosensitive drum 111 is used for determining the γ table. However, the present invention is not limited to this, and the density detection result of the patch image formed on the intermediate transfer belt 131 may be used. In this case, a sensor 138 (FIG. 1) provided opposite to the intermediate transfer belt 131 and having the same configuration as that of the above-described image density sensor 31 may be used. Similarly, in the case of a direct transfer type image forming apparatus, the detection result of the amount of applied toner of a patch image formed on a recording material carrier (such as a conveyance belt) can be used as a transfer medium (transfer body).

  Here, as is well known to those skilled in the art, the direct transfer type image forming apparatus is, for example, a recording material used as a conveyance belt in place of the intermediate transfer belt 131 provided in the image forming apparatus 100 of each of the above embodiments. It has a carrier. The toner images formed by the respective image forming portions on the recording material carried on the recording material carrier in the same manner as the image is transferred onto the intermediate transfer belt 131 in the image forming apparatus 100 of each embodiment described above. Are sequentially transferred. The present invention is equally applicable to such a direct transfer type image forming apparatus.

  Further, in each of the above embodiments, the γ correction table determination unit 165 has been described as selecting an appropriate one from a plurality of γ correction tables prepared in advance. You may make it create. In this case, the γ correction table determination unit 165 normally forms a plurality of reference images corresponding to a plurality of density levels based on reference data having a predetermined density level. Further, the γ correction table determination unit 165 causes the image density sensor 31 to measure the density of the reference image. Then, the γ correction table determining unit 165 compares the measurement result of each reference image with the standard density corresponding to each density level of each reference image. Based on the result, a γ correction table 166 is created so that the relationship between the density level of the image data before correcting the density and the density of the output image is ideally linear. In other words, a correction table is created that corrects the deviation of the density gradation characteristic when the density correction image is actually measured from the ideal density gradation characteristic (straight line). By using the γ correction table 166 created in this way in the same manner as in the above embodiments, the density fluctuation of the output image due to the increase in the T / D ratio of the developing device in the developing device 1 in the forced replenishment mode. Can be suppressed.

  Furthermore, the present invention is a developing device using a two-component developing device including a toner and a carrier, and is particularly effective in an image forming apparatus having a developing device having a trickle configuration. However, the present invention can also be applied to an image forming apparatus having a developing device that uses a one-component developer consisting essentially of toner, and charging up and deteriorating toner due to repeated use of the same toner. It is possible to suppress image defects caused by the above. When the developing device uses a one-component developer, the toner concentration of the developer in the developing device corresponds to the amount of toner in the developing device. In this case, only the toner is substantially discharged from the discharge port of the developing device.

1 is a cross-sectional view of an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a cross-sectional view of a developing device provided in the image forming apparatus of FIG. 1. FIG. 3 is a plan view of the developing device in FIG. 2. FIG. 3 is a control block diagram according to the first embodiment. FIG. 6 is a graph illustrating an example of a relationship between an image ratio and a toner supply amount. FIG. 6 is a control block diagram of Embodiment 2. 6 is a graph illustrating an example of a relationship between an average image ratio and a toner supply amount. FIG. It is sectional drawing of the conventional developing device for demonstrating an example of the toner concentration detection sensor of an optical reflected light quantity detection system. It is a top view of the developing device of FIG. It is a cross-sectional view of a conventional developing device for explaining an example of an inductance detection type toner density detection sensor. It is sectional drawing of the horizontal direction of the image development apparatus of FIG. FIG. 6 is a schematic diagram for explaining an example of a patch detection type toner density detection sensor. It is a chart figure which shows an example of the conventional control which performs toner discharge.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Developing apparatus 7 Supply port 8 Discharge port 40 Supply mechanism (supply means)
111 Photosensitive drum (image carrier)
112 Corona charger (charging means)
113 Laser exposure optical system (exposure means)
114 Cleaner (cleaning means)
131 Intermediate transfer belt (transfer medium)
161 Supply control unit (control means)
162 Image formation control unit 163 Image processing unit 164 Video counter (toner consumption estimation unit)
165 γ correction table determination unit 166 γ correction table 167 Page counter (image output number detection means)
168 Operation panel (operation unit)

Claims (13)

An image bearing member; a developing device that develops the electrostatic image formed on the image bearing member with toner; and a replenishing unit that replenishes toner to the developing device. The developing device includes the replenishing unit In the image forming apparatus having a discharge port through which the toner in the developing device is discharged along with the toner replenishment operation from
A first replenishment mode in which an amount of toner commensurate with a toner consumption amount associated with a developing operation of the developing device is replenished from the replenishing means to the developing device; and the toner consumption amount associated with the developing operation of the developing device. And a second replenishment mode in which toner is replenished from the replenishing means to the developing device such that the ratio of the toner replenishment amount from the replenishing means is greater than the ratio in the first replenishment mode. Image forming apparatus.   In the second replenishment mode, toner is replenished from the replenishing unit to the developing device such that the smaller the toner consumption by the developing device, the larger the ratio of the replenishment amount to the toner consumption amount. The image forming apparatus according to claim 1, wherein:   The image forming apparatus according to claim 1, wherein switching between the first supply mode and the second supply mode is determined based on a video count number of a density signal of an image information signal. .   As the toner consumption amount, when the predicted toner consumption amount for one output image is less than a predetermined value, the second replenishment mode is used. When the predicted toner consumption amount is not less than the predetermined value, The image forming apparatus according to claim 1, wherein toner is supplied from the supply unit to the developing device in the first supply mode.   The image forming apparatus according to claim 4, wherein the toner consumption amount prediction value is obtained from a video count number of a density signal of an image information signal.   When the average toner consumption predicted value for a predetermined number of output images is less than a predetermined value, the toner consumption is in the second supply mode, and the average toner consumption predicted value is greater than or equal to the predetermined value. 3. The image forming apparatus according to claim 1, wherein toner is supplied from the supply unit to the developing device in the first supply mode.   The image forming apparatus according to claim 6, wherein the predicted average toner consumption amount is obtained from a video count number of a density signal of an image information signal and an image output number.   The number of image outputs is determined by information designating the number of images formed from an operation unit provided in the apparatus main body or connected to the apparatus main body, or a detection result of the image output number detection means provided in the apparatus main body. The image forming apparatus according to claim 7.   A control reference image on the image carrier or on a transfer body on which a toner image is transferred from the image carrier in response to the supply of toner from the supply means to the developing device in the second supply mode. The image forming apparatus according to claim 1, wherein the image forming apparatus is formed.   The developing device contains a developer including toner and a carrier, the replenishing means replenishes the developing device with a carrier together with the toner, and the carrier is discharged together with the toner from the discharge port. The image forming apparatus according to any one of 1 to 9.   The image forming apparatus according to claim 10, wherein a ratio of a weight of toner in the replenishing agent to a weight of the replenishing agent replenished to the developer from the replenishing unit is 50% or more.   The amount of toner replenished from the replenishing means to the developing device is controlled by the density detection result of a control reference image formed on the image carrier or a transfer body onto which a toner image is transferred from the image carrier. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   The amount of toner replenished from the replenishing unit to the developing device is controlled by a detection result of toner density or toner amount in the developing device. Image forming apparatus.

Images