JP2017090676A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable an image forming apparatus that selectively drives members for supplying toners of different colors by common driving means to maintain an appropriate toner supply volume as long as possible thereby to form satisfactory images.SOLUTION: In a toner supply unit 11ab in which first and second toners are supplied to first and second developing devices that form toner images of different colors, the driving power of a motor 111ab is switched over with a clutch 122ab to drive supply screws of toner conveying pipes (116a and 116b), and the toners are supplied to the developing devices from hoppers 115a and 115b. When consecutive image formation is to be done, a controller (CPU 501) so alters, according to the quantity of shortage of toner supply relative to the required quantity for toner image formation, the conditions of image formation pertaining to the pertinent consecutive image formation that the shortage can be eliminated during the period from a certain phase of image formation until a succeeding phase of image formation.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an image forming apparatus having a toner replenishing portion that selectively drives toner supply members for different recording colors by a common driving means.

  In an image forming apparatus that forms an electrostatic latent image on an image carrier such as a photosensitive drum and develops the latent image using a developer such as toner, the developer in the developing device is consumed as the developer is consumed. A configuration in which the developer is appropriately replenished from the developer container to the developing device is widely adopted.

  In particular, in the case of a developing device that uses a two-component developer mainly composed of a non-magnetic toner and a magnetic carrier as a developer, the toner supply to the developing device is managed in order to maintain the toner concentration in the developer. In an image forming apparatus for forming a color image, many configurations for superposing a plurality of toner images of different colors such as yellow (Y), magenta (M), cyan (C), and black (Bk) are proposed and implemented. Has been. In such a configuration, since the toner consumption amount of each color developing device is different, a configuration including an independent toner supply member for each color and a driving means for driving the toner supply member is general.

  On the other hand, for example, for the purpose of reducing the size and weight and reducing the price, a technique of driving a plurality of toner supply members with a single driving unit has been proposed (for example, Patent Document 1 below). The apparatus described in Patent Document 1 has a configuration in which the driving force of one motor is transmitted to one of two supply members, and the transmission of the driving force is appropriately switched between the two supply members to thereby develop two developing devices. Supply developer.

Registered Utility Model 3060562

  However, in a configuration in which toner supply to a plurality of developing devices is performed by switching transmission of driving force using a common driving unit as in Patent Document 1, toner supply may not follow toner consumption. is there.

  Here, in an image forming apparatus including four developing devices of yellow, magenta, cyan, and black, consider a configuration in which toner supply to, for example, yellow and magenta developing devices is performed while switching drive transmission with a common motor. In this case, toner replenishment to the yellow and magenta developing devices cannot be performed simultaneously. Therefore, as compared with the case where each color has an independent motor, if the motor performance and the reduction ratio of the drive system are the same, the amount of toner that can be replenished to the developing device within a certain time is naturally reduced. Further, a case where the total amount of toner to be replenished to the yellow and magenta developing devices exceeds the replenishment capability is likely to occur, and there is a possibility that toner replenishment may not be in time for toner consumption. If the toner supply amount is insufficient as described above, there is a possibility that an image of the intended recording color cannot be formed.

  In view of the above, an object of the present invention is to maintain a proper toner supply amount as much as possible in an image forming apparatus that selectively drives a toner supply member for different recording colors by a common driving unit, and achieves a good image. It is to be able to form.

  In order to solve the above problems, in the present invention, a first developing device and a second developing device that form toner images of different colors with the first toner and the second toner, the first developing device, A first toner container for supplying toner to the second developing device; a second toner container; a first supply member for supplying the first toner from the first toner container to the first developing device; A second supply member for supplying the second toner from the two toner container to the second developing device; a drive means for generating a drive force for the first supply member and the second supply member; and the drive means. Switching means for switching between transmitting the driving force to the first supply member or the second supply member, and controlling image formation using the first developing device and the second developing device. A control unit, wherein the control unit calculates a necessary supply amount of the first and second toners necessary for image formation of the toner image, and the switching unit according to the calculated necessary supply amount And the driving means to supply the first and second toners to the first developing device and the second developing device, respectively, and to form a continuous image with the first developing device and the second developing device. When performing, the shortage amount between the first image forming apparatus and the second image formation is determined according to the shortage amount of the first and second toner supplyable amounts with respect to the necessary supply amount. A configuration is adopted in which the image forming conditions relating to the continuous image formation are changed so as to be supplied to the developing device.

  According to the above configuration, the image forming condition, for example, the image forming interval (inter-paper distance), or the driving for driving the first and second supply members according to the shortage of the supplyable amount with respect to the necessary supply amount of toner. Change the driving speed of the means. As a result, toner replenishment can follow the toner consumption, the possibility of image defects occurring can be reduced, and good image formation can be achieved. In other words, in an image forming apparatus that selectively drives toner supply members of different colors by a common driving unit, there is an excellent effect that an appropriate toner supply amount is maintained as much as possible and good image formation can be performed.

In Embodiments 1 and 2 of the present invention, it is an explanatory view showing a main part of an image forming mechanism. FIG. 3 is a configuration cross-sectional view of an image forming unit according to first and second embodiments of the present invention. FIG. 10 is an explanatory diagram showing a toner replenishment unit of yellow and magenta image forming units (stations) according to the first and second exemplary embodiments of the present invention from above the rear side of the image forming apparatus (the back side in FIG. 10). FIG. 3 is an explanatory diagram showing a toner replenishing portion of yellow and magenta image forming portions (stations) in Embodiments 1 and 2 of the present invention from the back side of the image forming apparatus. FIG. 6 is an explanatory diagram illustrating a toner replenishing portion of yellow and magenta image forming portions (stations) according to Embodiments 1 and 2 of the present invention from the right side of the image forming apparatus (right side in FIG. 10). It is the flowchart figure which showed the control procedure of the paper distance control sequence in Example 1 of this invention. FIG. 5 is a table showing the relationship between the number of insufficient blocks and the required inter-paper distance in the inter-paper distance control sequence of Example 1 of the present invention. In Example 2 of the present invention, (A) is a table showing the relationship among the number of missing blocks, the distance between sheets, and the converted productivity, and (B) is the number of missing blocks and necessary sheets in the sheet distance control sequence. It is the table | surface figure which showed the relationship between the distances. It is the flowchart figure which showed the control procedure of the paper distance control sequence in Example 2 of this invention. It is explanatory drawing which showed schematic structure of the image formation which can apply Example 1, 2 of this invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to embodiments shown in the accompanying drawings. The following embodiment is merely an example, and for example, a detailed configuration can be appropriately changed by those skilled in the art without departing from the gist of the present invention. Moreover, the numerical value taken up by this embodiment is a reference numerical value, Comprising: This invention is not limited.

<Example 1>
<Overall configuration of image forming apparatus>
FIG. 10 shows a schematic configuration of the image forming apparatus according to the embodiment of the present invention. The image forming apparatus illustrated in FIG. 10 is a digital full-color electrophotographic image forming apparatus using an intermediate transfer member.

  The image forming apparatus 200 is a so-called intermediate transfer tandem type image forming apparatus in which four color image forming units are arranged side by side on the intermediate transfer belt 7. This intermediate transfer tandem system has become a mainstream structure in recent years because it can cope with high productivity and transport of various media.

  The image forming mechanism of the image forming apparatus 200 is accommodated in, for example, a box-shaped housing. For example, a recording material storage C for storing the recording material S is provided in the lower part thereof, and the recorded recording material S is provided in the upper part from the center. Is disposed (so-called “in-body discharge” type arrangement). On the upper part of the apparatus, an operation panel 60 composed of a display or a keyboard is arranged. Further, an image scanner (not shown in detail) is disposed above the discharge tray 63, for example, if the product has a copying function.

  In the upper right part of the image forming apparatus 200 in FIG. 10, a configuration block of a control apparatus 500 that is a control system of the image forming apparatus 200 is shown. The control device 500 includes a CPU 501, a ROM 502, a RAM 503, and interfaces 504 and 505, which are general-purpose microprocessors. The interface 504 is used for the CPU 501 to communicate with, for example, active components (motors, solenoids, etc.) and various sensors of each part of the apparatus. The interface 505 is, for example, a network interface or various printer port communication means, and is used for communication with an external host device (for example, a personal computer or various servers). When the interface 505 is constituted by a network interface or the like, the interface 505 can also be used as a communication means for installing or updating a control program (part or all) described later. Necessary electric power is supplied from the power supply device 506 to the control device 500, a motor for the conveyance system of the recording material S described later, and other drive sources.

  Hereinafter, each part of the image forming apparatus 200 will be described in more detail along the flow of the image forming process. In FIG. 10, the direction perpendicular to the paper surface corresponds to the front to back direction of the image forming apparatus 200.

<Recording material transport process>
The recording material S made of an arbitrary sheet material such as paper or resin is stored in a form of being stacked on the recording material storage C, and is fed in accordance with the image formation timing by a paper feed roller 61 adopting a friction separation method. Is done. The recording material S sent out by the paper feed roller 61 passes through the transport path and is transported to the position of the transport roller 62. After skew correction and timing correction (so-called registration) are performed by the transport roller 62, the recording material S is sent to the secondary transfer portion T2. The secondary transfer portion T2 is a transfer nip portion formed by the opposing secondary transfer inner roller 9 and secondary transfer outer roller 10, and on the recording material S by applying a predetermined pressure and an electrostatic load bias. The toner image is adsorbed to the toner.

<Image formation process>
With respect to the conveyance process of the recording material S up to the secondary transfer unit T2 described above, a process for forming an image sent to the secondary transfer unit at the same timing will be described. In FIG. 10, stations Pa to Pd constitute an image forming unit that forms an image with each of the recording colors of yellow, magenta, cyan, and black. These stations Pa to Pd are mainly photosensitive drums 1a to 1d, chargers 2a to 2d, exposure devices 3a to 3d, developing devices 4a to 4d, developing containers 101a to 101d, primary transfer devices T1a to T1d, and photosensitive drum cleaners. 6a-6d.

  The surfaces of the photosensitive drums 1a to 1d are uniformly charged in advance by the chargers 2a to 2d while being driven to rotate (the rotation directions are R1 to R4, respectively) by a drive system (not shown). The exposure devices 3a to 3d are constituted by, for example, a laser light source and a deflection device. The exposure devices 3a to 3d are driven based on a signal of image information to be recorded, and the recording light is irradiated through a diffraction unit as appropriate, thereby forming electrostatic latent images on the photosensitive drums 1a to 1d. .

  The electrostatic latent images formed on the photosensitive drums 1a to 1d are manifested as toner images through toner development by the developing devices 4a to 4d. Thereafter, predetermined pressurizing force and electrostatic load bias are applied by the primary transfer devices T1a to T1d, and the toner image is transferred onto the intermediate transfer belt 7. Finally, the transfer residual toner slightly remaining on the photosensitive drums 1a to 1d is collected by the photosensitive drum cleaners 6a to 6d, and is again prepared for the next image forming process.

  When the amount of toner in the developing devices 4a to 4d at the stations Pa to Pd decreases, toner is replenished from toner storage containers Ta to Td (FIG. 10) of a toner replenishing device (FIGS. 3 to 5) described later. For example, yellow (Y), magenta (M), cyan (C), and black (Bk) toner (two-component developer) is stored in the toner storage containers Ta to Td (FIG. 10). The toner storage containers Ta to Td in FIG. 10 correspond to, for example, toner bottles 119a, 119b (...) Shown in a toner supply device (FIGS. 3 to 5) described later.

  In FIG. 10, only a replenishment route for the station Pa in a toner replenishing device (FIGS. 3 to 5) described later is indicated by reference numeral 20a. 10 corresponds to, for example, a portion of the hopper 115a in a toner replenishing device (FIGS. 3 to 5) described later. The other stations Pb, Pc, and Pd are also provided with a toner replenishing device including a similar replenishment path, but these are not explicitly shown in FIG. 10 for simplification.

  The configuration of the toner replenishing device including the toner storage containers Ta to Td (toner bottles) will be described in detail with reference to FIGS.

  As described above, in the case of FIG. 1, the stations Pa to Pd (image forming units) are arranged in four sets corresponding to the respective recording colors of yellow (Y), magenta (M), cyan (C), and black (Bk). Has been. In the following, the above abbreviations in alphabet may be used to refer to the recording color. Note that the number of colors is not limited to four, and the order of colors is not limited to this. In addition, a two-component developer in which a nonmagnetic toner and a magnetic carrier are mixed in advance is accommodated in the developing devices 4a to 4d of the stations Pa to Pd. In the present embodiment, a configuration in which such a two-component developer (initial agent) is accommodated will be described. However, the control described later can be performed even in the case of a one-component developer using only magnetic toner or non-magnetic toner. is there.

  The intermediate transfer belt 7 is installed on an intermediate transfer belt frame (not shown). The intermediate transfer belt 7 is configured as an endless belt stretched by a secondary transfer inner roller 8 that also serves as a drive transmission means to the intermediate transfer belt, a tension roller 17, and a secondary transfer upstream roller 18.

  The intermediate transfer belt 7 is transported and driven in the direction of arrow R7 in the figure by a drive system (not shown). The image forming process of each color processed in parallel by the stations Pa to Pd of Y, M, C, and Bk is performed at the timing of sequentially superimposing on the upstream color toner image primarily transferred onto the intermediate transfer belt 7. As a result, a full-color toner image is finally formed on the intermediate transfer belt 7 and conveyed to the secondary transfer portion T2. The transfer residual toner after passing through the secondary transfer portion T2 is collected by the transfer cleaner device 110.

<Process after secondary transfer>
By the above-described transport process and image forming process, the timings of the recording material S and the full-color toner image coincide with each other, and the secondary transfer is performed in the secondary transfer unit. The recording material S is conveyed to the fixing device 13. The fixing device 13 applies a predetermined pressure and heat amount to the passing recording material S in a fixing nip formed by opposing rollers, and melts and fixes the toner image on the recording material S. For this reason, the fixing device 13 includes a heater serving as a heat source, and is controlled so that the optimum temperature is always maintained. The recording material S after image fixing is discharged onto a discharge tray 63 via a conveyance path not shown in detail, or is conveyed to a reverse conveyance device (detail not shown) when double-sided recording is required.

  FIG. 1 shows the configuration of the image forming apparatus around the intermediate transfer belt 7, and FIG. 2 shows the configuration of a yellow (Y) station Pa (image forming unit) in more detail.

  As shown in FIG. 1, below the intermediate transfer belt 7, four stations Pa, Pb, Pc, and Pd (image forming units) that are configured in a similar manner are arranged side by side. The four stations Pa, Pb, Pc, and Pd correspond to recording colors of yellow (Y), magenta (M), cyan (C), and black (Bk), respectively.

  Since these four stations Pa, Pb, Pc, and Pd have almost the same configuration, the yellow (Y) station Pa will be described as an example with reference to FIG. Regarding the other color stations, the following description of the yellow (Y) station Pa applies to the other stations Pb, Pc and Pd as well.

  FIG. 2 shows a cross-sectional configuration of the yellow (Y) station Pa. The image forming unit includes a drum-shaped photosensitive drum 1a (hereinafter referred to as a photosensitive drum 1a) that is rotatably disposed around a central axis. The center has a support shaft (not shown), and is driven to rotate in the direction of arrow R1 about the support shaft by a drive means (not shown).

  Around the photosensitive drum 1a, process means such as a charger 2a, a developing device 4a, a primary transfer roller 5a, and a blade of a photosensitive drum cleaner 6a are arranged. Among these, the photosensitive drum 1a, the charger 2a, the developing device 4a, and the photosensitive drum cleaner 6a can be unitized into, for example, one cartridge. When these members are integrated with the cartridge, they can be attached to and detached from the image forming apparatus 200 by exchanging the cartridge.

  The charger 2a is in contact with the surface of the photosensitive drum 1a to uniformly and uniformly charge the surface to a predetermined potential, and is configured as a roller as a whole (hereinafter referred to as a charger 2a). The charger 2a includes a conductive roller (core metal) disposed in the center and a conductive layer formed on the outer periphery thereof, and both ends of the core metal are rotatably supported by a bearing member (not shown). These are arranged in parallel to the photosensitive drum 1a. The bearing members at both ends are urged in the direction of the photosensitive drum 1a by urging means (not shown). As a result, the charger 2a is pressed against the surface of the photosensitive drum 1a with a predetermined pressing force, and is driven to rotate as the photosensitive drum 1a rotates in the direction of arrow R1. A predetermined bias voltage is applied to the cored bar of the charger 2a by a power source, thereby uniformly and uniformly charging the surface of the photosensitive drum 1a. In this embodiment, for example, only a DC voltage is applied to the charger. For example, when a voltage of about -1350V is applied to the core of the charger, the photosensitive drum is charged to about -750V. The recording light modulated in accordance with the image signal of the yellow component color of the recording image is made negative by the charger 2a through the scanning means such as a polygon mirror (not shown) from the laser scanner constituting the exposure devices 3a to 3d. The light is projected onto the charged photosensitive drum 1a. As a result, a potential drop occurs in the photosensitive portion of the photosensitive drum 1a irradiated with the recording light, and an electrostatic latent image corresponding to the recorded image is formed on the surface of the photosensitive drum.

  The developing device 4a disposed on the downstream side in the R1 direction of the charger 2a supplies developer to the surface of the photosensitive drum on which the electrostatic latent image is formed, and develops the electrostatic latent image as a toner image. As described above, in this embodiment, a two-component developer mainly composed of a nonmagnetic toner and a magnetic carrier is used.

  A developing sleeve 41a as a developer carrying member is disposed at a position facing the photosensitive drum. In the developing sleeve 41a, a magnet as a magnetic field generating means is fixedly disposed inside a rotatable nonmagnetic element tube, and the toner (two-component developer) in the developing device 4a is developed by the magnetic force of the magnet. Supported on. Next, the toner on the developing sleeve 41a is regulated to a predetermined value by a regulating blade 45a as a developer regulating member, and is conveyed to a developing area facing the photosensitive drum 1a as the developing sleeve 41a rotates. The

  The magnetic pole of the magnet of the developing sleeve 41a is arranged so that toner as a two-component developer forms a so-called magnetic brush in the developing area. By bringing a magnetic brush formed on the developing sleeve 41a into contact with the photosensitive drum 1a, toner is supplied to the electrostatic latent image portion. At this time, a predetermined bias is applied from the developing bias power source (not shown) to the developing sleeve 41a so that the toner is selectively attracted only to the region where the bright portion potential is formed on the photosensitive drum 1a. Thereby, the electrostatic latent image on the photosensitive drum 1a is visualized and becomes a toner image. In this embodiment, for example, a developing bias in which an AC voltage having a peak-to-peak voltage of about 1750 V is superimposed on a DC voltage of about −600 V is used.

  A primary transfer roller 5a is disposed on the downstream side in the R1 direction of the developing device 4a. Both ends of the primary transfer roller 5a are urged toward the photosensitive drum 1a by a pressing member such as a spring (not shown). As a result, the primary transfer roller 5a is pressed against the photosensitive drum 1a with a predetermined pressing force to form the primary transfer portion. When the toner image reaches the primary transfer portion where the photosensitive drum 1a and the intermediate transfer belt 7 come into contact with the rotation of the photosensitive drum 1a, the yellow toner image on the photosensitive drum 1a is transferred to the intermediate transfer belt 7 by the primary transfer bias. Is transferred to.

  Thereafter, as the photosensitive drum 1a further rotates, residual toner on the photosensitive drum 1a is removed by the photosensitive drum cleaner 6a disposed on the downstream side in the R1 direction of the primary transfer portion.

  The other stations Pb, Pc, and Pd have the same configuration as that of the (yellow) station Pa. The difference between Pa and Pb, Pc, and Pd is that each of the toner images is yellow, magenta, cyan, and black. It is a point that forms. The intermediate transfer belt 7 carrying the yellow toner image is then conveyed to the position of the primary transfer portion of the magenta station Pb. By this time, at the magenta station Pb, a magenta toner image has been formed on the photosensitive drum 1b in the same manner as the (yellow) station Pa, and this magenta toner image is transferred onto the yellow toner image. . Thereafter, a cyan toner image and a black toner image are sequentially superimposed and transferred onto the intermediate transfer belt by a similar process.

  On the other hand, in FIG. 1, the conveyance control is performed so that the recording material S taken out from the recording material storage C by the paper feed roller 61 waits in a state where the leading end stops at the position of the conveyance roller 62, for example. Then, the image formed on the intermediate transfer belt 7 is fed by the conveying roller 62 at a timing so that the image can be transferred to a predetermined position of the recording material. As a result, the recording material S reaches the secondary transfer position where the secondary transfer inner roller 8 and the secondary transfer outer roller 9 are in contact with each other via the intermediate transfer belt 7. At this secondary transfer position, the four color toner images on the intermediate transfer belt 7 are collectively transferred onto the recording material S by the secondary transfer bias applied to the secondary transfer outer roller 10.

  The four color toner images transferred to the recording material S are fixed on the recording material S by fixing device rollers 14 and 15 (FIG. 10). The obtained (recorded) recording material S as a final product is discharged onto a discharge tray 63 via a conveyance path (not shown in detail), or a reverse conveying device (detailed It is conveyed to the figure.

<Toner supply system>
3, 4 and 5 show the configuration of the toner replenishing portion 11ab of the stations Pa and Pb corresponding to the yellow and magenta recording colors in this embodiment. Among these, FIG. 3 shows the toner replenishing portion 11ab from the upper side of the back side of the image forming apparatus (the back side in FIG. 10). 4 shows the toner supply unit 11ab from the back side of the image forming apparatus 200, and FIG. 5 shows the toner supply unit 11ab from the right side of the image forming apparatus 200 (right side in FIG. 10). In FIG. 3 to FIG. 5, the suffix “a” or “b” as a reference symbol indicates that the member is a member of the stations Pa and Pb (for). In these drawings, the suffix “ab” as a reference symbol indicates that the corresponding member is a member provided in common for the stations Pa and Pb.

  In the present embodiment, the toner replenishing portion 11ab is provided in common for the two stations Pa and Pb. In the toner replenishing portion 11ab, members such as the gear 112ab and the motor 111ab are provided in common for the stations Pa and Pb (not provided respectively).

  Although not shown in the drawing, it is assumed that a toner replenishing section (for example, 11 cd) configured similarly is provided for the (cyan) station Pc and the (black) station Pd. The configuration of the toner replenishing unit (for example, 11 cd) for the stations Pc, Pd is, for example, “a”, “b”, “ab”, etc., which are suffixes of reference numerals in FIGS. This corresponds to a configuration read as “d”, “cd”, or the like.

  3 to 5, for the sake of simplification, with regard to the developing devices 4a and 4b, only the stirring and conveying screws 42a, 42b, 43a, and 43b related to toner conveyance are illustrated, and the other members are not illustrated. It is shown.

  As shown in FIGS. 3 to 5, driving force transmitting means such as hoppers 115 a and 115 b and gear trains 113 a and 113 b are arranged on the back side of the image forming apparatus of the developing devices 4 a and 4 b. Hereinafter, description will be made with reference to a member in which “a” is added as a suffix to the reference numeral on the (yellow) station Pa side. (Magenta) With regard to members on the station Pb side, an explicit explanation is omitted except for a part, but if the suffix of the reference sign in the following explanation is replaced with “b”, the member on the station Pb side (magenta) The explanation is valid as it is.

  3 to 5, the hopper 115a has, for example, a hollow shape in which an upper portion is opened and a box shape that is recessed downward. To the hopper 115a, (yellow) toner is supplied from a toner bottle 119a disposed above. The hopper 115a corresponds to a first toner container for (temporarily) storing toner to be supplied to the developing device 4a. On the other hand, the hopper 115b is supplied with (magenta) toner from the toner bottle 119b. The hopper 115b corresponds to a second toner container for (temporarily) storing toner to be supplied to the developing device 4b.

  As shown in FIG. 5, a toner conveying pipe 116a projects in the horizontal direction below the developing device 4a and extends above the developing device 4a. The toner transport pipe 116a communicates with the inside of the hopper 115a. A replenishing screw (not shown) is rotatably disposed inside the toner transport pipe 116a, and the replenishing screw is connected to the gear 114a.

  Further, although not explicitly shown in FIG. 5, a similar toner transport pipe is also provided in the hopper 115b. The structure of the toner transport pipe 116b is the same as that of the toner transport pipe 116a. Hereinafter, the toner transport pipe of the hopper 115b may be referred to as a toner transport pipe 116b for convenience.

  On the other hand, in the station Pb on the magenta side, the replenishing screw for the hopper 115b similarly configured is connected to the gear 114b. Gears 114a and 114b for driving these hoppers 115a and 115b mesh with a gear train 113a or a gear train 113b described later, and are driven by a motor 111ab via these gear trains.

  At the left end of the toner conveying pipe 116a (FIG. 5), for example, a replenishment hole is formed that opens to face the upper opening of the developing device 4a developing container (101a: FIG. 10). When the driving force is transmitted to the gear 114a, the toner in the toner transport pipe 116a is transported by the replenishing screw and falls into the developing device 4a. In this way, (yellow) toner is supplied from the hopper 115a to the developing device 4a. On the other hand, when the driving force is transmitted to the gear 114b, (magenta) toner is supplied from the hopper 115b to the developing device 4b.

  A toner bottle 119a is rotatably disposed above the hopper 115a. The toner to be supplied to the hopper 115a is stored in the toner bottle 119a. Screw-shaped ribs (projections) are formed on the inner side surface of the toner bottle 119a. When the toner bottle 119a is rotated, the internal (yellow) toner is conveyed along the screw-shaped rib toward the tip of the toner bottle 119a (front side in FIG. 3, right side in FIG. 5), and the discharge port at the tip Falls into the lower hopper (arrow in FIG. 5). This configuration and operation is the same for the (magenta) toner bottle 119b.

  3 to 5, the driving mechanism of the toner replenishing portion 11ab is configured as follows. The structure of the drive mechanism for the two recording colors, yellow and magenta stations Pa and Pb described below, is the same as that for the cyan and black stations Pc and Pd.

  A motor 111ab is disposed below the toner supply unit 11ab. The gear 112ab transmits the driving force of the motor 111ab to either the gear train 113a or the gear train 113b. As described above, the gear trains 113a and 113b mesh with the gears 114a that drive the replenishing screws of the toner transport pipes (116a to 116b) that transport the toner from the hoppers 115a and 115b to the developing devices 4a and 4b, respectively. In this embodiment, whether the driving force of the motor 111ab is transmitted to the gear train 113a or the gear train 113b is determined by, for example, the CPU 501 switching the electromagnetic clutch 122ab (FIGS. 3 and 4). Further, for example, the rotational drive direction of the motor 111ab is also switched in conjunction with each other as follows according to the arrangement and meshing relationship of each gear.

  Here, it is assumed that the torsion directions of the replenishing screws driven by the gear trains 113a and 113b inside the toner transport pipe 116a (or 116b) are the same. When the gear trains 113a and 113b are driven, these gear trains need to be driven so that both yellow and magenta toners are conveyed in the direction of the developing device. Therefore, for example, in the gear arrangement as shown in FIG. 4, the CPU 501 controls the driving force to be transmitted to the gear train 113a when the motor 111ab rotates in the positive direction and to the gear train 113b when the motor 111ab rotates in the negative direction. That is, the CPU 501 controls the rotation direction of the motor 111ab and the transmission direction by the electromagnetic clutch 122ab, for example, in the above combination, depending on which station needs toner conveyance.

  In this way, when the motor 111ab is rotating forward, the gear 114a rotates the supply screw of the toner transport pipe 116a of the (yellow) station Pa via the gear train 113a. When the motor 111ab rotates in the reverse direction, the replenishing screw of the toner transport pipe (for example, 116b) of the (magenta) station Pb is rotated through the gear train 113b.

  Similarly, the drive mechanism of the toner bottles 119a and 119b has a common drive source motor 118ab. The gear 121ab driven by the motor 118ab can be engaged with the gear train 120a or 120b by the electromagnetic clutch 122ab. As shown in FIGS. 3 and 5, the spiral directions of the ribs inside the toner bottles 119a and 119b are the same, and the rotational drive directions in which the toner can be carried out are the same in the toner bottles 119a and 119b.

  Further, if the gear 121ab and the gear trains 120a and 120b are meshed as shown in FIGS. 3 and 4, the rotation direction of the motor 111ab and the electromagnetic clutch (not shown) depending on which bottle needs toner conveyance. Are used in combination with a specific relationship. For example, the CPU 501 controls the toner bottle 119a of the station Pa to rotate when the motor 118ab rotates forward (yellow), and the toner bottle 119b of the station Pb rotates when it rotates reversely (magenta). That is, as a result, both the toner bottles 119a and 119b can be driven in the direction of carrying out the toner.

  Here, for example, it is assumed that the developing devices 4a and 4b at the stations Pa and Pb having the recording colors of yellow and magenta have a first developing device for forming different color toner images with the first and second toners, and a first developing device, respectively. 2 Correspond to the developing device.

  Then, with respect to the stations Pa and Pb, a toner replenishing section 11ab in which motors 111ab and 118ab and gears 112ab and 121ab driven by them are made common is arranged.

  The hoppers 115a and 115b for supplying toner to the developing devices 4a and 4b (first and second developing devices) respectively correspond to a first toner container and a second toner container.

  The toner replenishing section 11ab includes toner transport pipes 116a and 116b for supplying toner from the hoppers 115a and 115b (first and second toner containers) to the developing devices 4a and 4b (first and second developing devices), respectively. Is provided. These toner transport pipes 116a and 116b incorporate supply screws that are driven through the gear train 113a and gear 114a, and the gear train 113b and gear 114b, respectively. The toner transport pipes 116a and 116b correspond to, for example, a first supply member and a second supply member that supply the respective color toners to the first and second developing devices.

  The motor 111ab corresponds to a driving unit that generates a driving force for the toner transport pipes 116a and 116b (first and second supply members).

  Further, the CPU 501 of the control system switches via the electromagnetic clutch 122ab whether the driving force generated by the motor 111ab, which is the driving means, is transmitted to the toner transport pipes 116a, 116b (first or second supply member). . This configuration corresponds to switching means for switching whether the driving force generated by the motor 111ab (driving means) is transmitted to the toner transport pipe 116a or 116b (first or second supply member).

  Further, the CPU 501 as a control unit switches the driving force generated by the motor 111ab and supplies toner to the developing device 4a or 4b (first or second developing device). In this case, for example, the necessary supply amounts of the first and second toners necessary for forming the toner image are calculated by software executed by the CPU 501, and the driving force generated by the motor 111ab according to the necessary supply amount. Switch. That is, according to the required supply amount calculated by the required supply amount calculation unit realized by software executed by the CPU 501, the transmission direction of the driving force of the motor 111ab and the rotation direction of the motor 111ab are controlled, for example. And controlling the supply of the second toner.

  However, in the configuration in which the driving force generated by the common motor 111ab is switched and the toner is supplied to the developing device 4a or 4b (first or second developing device), for example, depending on the image forming conditions, toner replenishment with respect to toner consumption May not be in time.

  Therefore, in this embodiment, particularly when continuous image formation is performed, the image forming conditions related to the continuous image formation are changed according to the shortage of the supplyable amounts of the first and second toners. For example, the CPU 501 serving as the control unit causes the shortage amount between the first image forming apparatus and the subsequent image formation to be short between the first developing device and the subsequent image formation in accordance with the shortage amount of the first and second toner supplyable amounts with respect to the necessary supply amount. The image forming conditions are changed so as to be supplied to the second developing device.

  For example, in the following control example, the change of the image formation condition for the continuous image formation is performed by changing the image formation interval (inter-paper distance control) from a certain image formation to the subsequent image formation.

<Toner supply control>
In this embodiment, the CPU 501 serving as a control unit controls the entire image forming process using the developing device 4a or 4b (first or second developing device).

  As shown in FIGS. 3 to 5, the toner replenishing unit 11ab has a configuration in which a part of the motor, for example, a driving unit that generates a driving force for supplying toner with respect to two recording colors is shared. . Then, the CPU 501 serving as the control unit controls the transfer of the driving force generated by the motor 111ab (or the rotational driving direction) so that the toner that needs to be supplied is conveyed.

  For example, the CPU 501 serving as the control unit calculates a required supply amount (hereinafter also referred to as a supply amount) of the first and second toners necessary for forming the toner image. Then, according to the calculated required supply amount, the electromagnetic clutch 122ab (switching means) and the rotation drive of the motor 111ab as the drive means are driven so that the toner that needs to be supplied among the first and second toners is conveyed. Control the direction. As a result, of the first and second toners, the toner that needs to be supplied is supplied to the first developing device and the second developing device, respectively.

  In such a configuration in which the toner replenishing unit 11ab is controlled in a time-sharing manner and two colors of toner are conveyed, there is a possibility that the toner supply may be insufficient when continuous image formation is performed in a print job including a plurality of pages. There is. Therefore, in this embodiment, when the continuous image formation is performed by the developing device 4a or 4b (first or second developing device), the CPU 501 determines the supply amount of the first and second toners with respect to the calculated required supply amount. Calculate the deficiency. Then, in accordance with the calculated shortage amount, the continuous image formation is performed so that the shortage amount is supplied to the developing device 4a or 4b (first or second developing device) between a certain image formation and the subsequent image formation. Change the image forming conditions. In the following, an example in which the image forming conditions related to continuous image formation are changed by changing the image formation interval (inter-paper distance control) from one image formation to the subsequent image formation will be described.

  Hereinafter, the details of the toner replenishment (supply) control will be described in more detail.

<Calculation of toner replenishment amount (necessary supply amount)>
A so-called ATR (automatic toner supply) technique is known as a technique for controlling the toner replenishment amount. In ATR (automatic toner supply), the CPU 501 determines the necessary supply amount to be supplied to the developing device, that is, the replenishment toner amount, according to the content of the image signal to be recorded and the state of the toner in the developing device. Since basic control of this ATR (automatic toner supply) is well known, detailed description thereof will be omitted below.

  On the other hand, the dimensions and pitch of the replenishing screw of the toner transport pipe 116a or 116b (first or second supply member) are known from the design conditions. Further, the CPU 501 can naturally grasp the drive rotation speed of the replenishment screw. Therefore, the CPU 501 can calculate the supplyable amount of the toner transport pipe 116a or 116b (first or second supply member) at the drive rotational speed based on the design condition of the supply screw and the drive rotational speed.

  In this embodiment, the CPU 501 determines a necessary supply amount to be supplied to the developing device, that is, a replenishment toner amount, by control using both the video count ATR and the ATR based on inductance detection. When an image signal to be recorded arrives, the CPU 501 calculates a toner amount (specific color) necessary for recording the image by video count ATR processing according to the content of the image signal. In the ATR based on inductance detection, the CPU 501 measures the magnetic permeability of the developer by an inductance sensor (not shown) installed in the developing device, and calculates the toner amount in the developing device (particularly the developing container).

  For example, the basic supply amount Rv is determined by the video count ATR, and the supply correction amount Ri is determined by the ATR based on the inductance detection. Of these, the basic supply amount Rv can be considered as, for example, the amount of toner consumed by image recording of a specific image signal, and the supply correction amount Ri is, for example, an insufficient amount of toner actually occurring in the developing device. Therefore, for example, the CPU 501 obtains the total replenishment amount R of the toner to be supplied to the developing device at a certain point of time by calculating the sum (Rv + Ri) of the basic replenishment amount Rv and the replenishment correction amount Ri (Rv + Ri). Rv + Ri)).

  In the video count ATR, the amount of toner consumed at each color station Pa to Pd is estimated from pixel information of an image to be recorded. In the present embodiment, the basic replenishment amount is calculated by calculating the video count value of each color of the image from the integrated value of the density of each pixel of the document and using the relationship between the video count value stored in advance in the table memory and the replenishment toner amount. Rv is obtained. The table memory for this purpose can be stored in an external storage device (not shown) such as a ROM 502 or HDD, for example, and can be referred to at the storage location or expanded on the RAM 503. Good.

  However, in the video count ATR, when the cumulative number of recorded sheets increases, an error in the replenishment amount may be gradually accumulated. Therefore, the toner replenishment amount can be determined by combining with the ATR based on inductance detection.

  In the ATR based on inductance detection, the magnetic permeability of the developer is measured by an inductance sensor (not shown) installed in the developing device. This inductance sensor uses, for example, an event in which the magnetic flux density induced when a high frequency voltage is applied to a built-in coil depends on the magnetic permeability around the coil. By measuring the self-inductance of the coil with this inductance sensor, the magnetic permeability around the coil can be detected as an electric signal. The magnetic permeability of the developer varies depending on the mixing ratio of the toner (developer) magnetic carrier and the non-magnetic toner. For this reason, for example, by installing an inductance sensor in the developer conveyance path, the proportion of non-magnetic toner in the developer (hereinafter referred to as T / D ratio) can be monitored.

  In the ATR based on the inductance detection, the replenishment correction amount Ri is calculated using a table of the relationship between the difference between the detected inductance and the reference inductance (for example, the inductance at the initial setting) and the replenishment toner amount. The table memory storing the table data is also referred to on the external storage device such as the ROM 502 and HDD, or is expanded in the RAM 503 and referred to in the same manner as described above.

  However, in the ATR based on inductance detection, there is a case where the T / D ratio is erroneously detected due to a change in apparent permeability when the bulk density of the developer changes due to long-term standing or the like. Therefore, for example, control using only the video count ATR is performed for a predetermined number of times after the power of the image forming apparatus main body is turned on, and after that, it is considered that the state of the developer has recovered, and ATR based on inductance detection is used again. Toner replenishment control is performed.

<Paper distance control sequence>
In the following, the toner replenishing section 11ab of the (yellow) station Pa and the (magenta) station Pb will be described as an example. However, as a matter of course, the following description is similarly applied to the (cyan) station Pc and the (black) station Pd in which the motors (111cd, 118cd) and the gears (112cd, 121cd) driven by them are shared. To do.

  In this embodiment, the toner supply amount is managed in units of blocks. As described above, the toner replenishment amount and the rotation amount of the toner replenishment screw of the toner transport pipe 116a or 116b (first or second supply member) are in a proportional relationship. Accordingly, the CPU 501 can obtain the replenishment amount of the desired number of blocks by controlling the number of rotations of the motor (111ab) that drives the toner replenishment screw, for example. For example, the design constants such as the size and pitch of the toner supply screw of the toner transport pipe 116a or 116b are constant. Therefore, the CPU 501 can obtain the number of blocks corresponding to the toner supplyable amount from the number of rotations of the motor (111ab) driving the toner supply screw.

  On the other hand, the necessary supply amount to be supplied to the developing device calculated as described above, that is, the replenishment toner amount is the above-described total replenishment amount R. The CPU 501 once converts this total supply amount R into the number of supply blocks. In this embodiment, for example, one block corresponds to about 15 mg of toner.

  As described above, the toner replenishing portion 11ab provided in common for the yellow and magenta stations Pa and Pb is driven while switching appropriately using the common motor 111ab. For this reason, there is an upper limit to the total amount of yellow toner and magenta toner that can be replenished within a certain time. That is, the amount of toner that is replenished when the motor 111ab is continuously rotated at a specific maximum rotational speed is the maximum value that can be replenished.

  In this embodiment, it is assumed that the inter-paper distance, which is the default image formation interval (distance) on the intermediate transfer belt 7 during continuous image formation, is 40 mm, for example. At this default distance between sheets, in the present embodiment, the toner supply unit 11ab supplies a maximum of 4 blocks of yellow and magenta toners (first and second toners) while outputting one A4 image. It shall be possible.

  FIG. 6 shows the flow of the inter-paper distance control sequence in this embodiment. The control procedure of FIG. 6 can be stored in, for example, the ROM 502 as a program executed by the CPU 501. In FIG. 6, the necessary supply amount and the supplyable amount of toner described above are both expressed by the number of blocks. For example, hereinafter, a value obtained by converting the total supply amount R (required supply amount) obtained based on the ATR control based on video count and inductance detection into a block is referred to as the number of supply blocks. Further, the number of blocks corresponding to the supplyable amount determined by the rotational speed of the motor (111ab) that drives the toner supply screw is referred to as the number of replenishable blocks. In the present embodiment, the required supply amount and the supply possible amount of toner are evaluated in units of image formation of one A4 image.

  In FIG. 6, when the CPU 501 receives an image formation start signal via the interface 505 or the like, the CPU 501 refers to the supply block numbers of the yellow and magenta stations Pa and Pb in step S11, and calculates the total amount (required supply amount). Ask.

  Next, in step S12, it is confirmed whether or not the total replenishment block number exceeds the replenishable block number (four blocks in this embodiment). If the total number of replenishment blocks is less than or equal to the number of replenishable blocks, the T / D ratio can be maintained without adjusting the inter-sheet distance, and the process proceeds to step S13, where image formation is performed within the normal operation range. To replenish toner.

  On the other hand, if the total number of replenishment blocks exceeds the number of replenishable blocks in step S12, toner replenishment for maintaining the T / D ratio cannot be completed by the next page image formation. . In this case, the process proceeds from step S12 to S16, and the toner supply to the next image is performed by increasing the image formation interval on the intermediate transfer belt 7 to the next image, that is, the inter-paper distance, while keeping the image formation speed constant. Can be completed.

  In the control example of FIG. 6, in step S16, the difference between the total number of replenishment blocks and the number of replenishable blocks is calculated. Then, the inter-paper distance is determined based on a memory table that defines the relationship between the number of insufficient blocks stored in advance in the memory in the image forming apparatus main body and the inter-paper distance necessary to complete the toner supply amount.

  An example of table data storing the relationship between the number of insufficient blocks and the distance between sheets is shown in FIG. The table memory that stores the table data is referred to on an external storage device such as the ROM 502 or HDD, or is expanded and stored in the RAM 503. In the table memory of FIG. 7, 701 is the number of missing blocks and 702 is a paper distance field, and the number of short blocks and the paper distance are related by one line record in the figure.

  In FIG. 7, the table data is configured so that the default distance of 40 mm is selected when the number of insufficient blocks is 1 to 4. On the other hand, when the number of insufficient blocks exceeds 4, a distance between sheets of 125 mm is selected when the number of insufficient blocks is 5, and when the number of insufficient blocks is 6, a paper distance of 210 mm is selected. That is, the distance between the sheets on the intermediate transfer belt 7 is increased from the default of 40 mm, the development timing up to the next toner is advanced, and the required supply amount of toner can be conveyed to the developing device during that time.

  In step S17, the control parameters (image forming conditions) of each part of the apparatus are changed so that image formation is performed at the inter-paper distance obtained by performing the table calculation according to the number of insufficient blocks in step S16. Specifically, the selection of the inter-paper distance can be realized by controlling the drive timing of the conveyance system for carrying the recording material S into the intermediate transfer belt 7. After changing the inter-paper distance in step S17, control proceeds to step S13.

  When image formation for one page is executed in step S13, it is determined in step S14 whether the formed image is the last page of a job in continuous image formation. If it is determined in step S14 that the formed image is not the last page, the process returns to step S11, and the above operation is repeated with reference to the number of supply blocks corresponding to the subsequent image. On the other hand, if the formed image is the last page of the job, the distance between sheets is returned to the default setting (40 mm) in step S15, and the image forming operation is terminated.

  As described above, according to the control example of FIG. 7, the total number of replenishment blocks is calculated, and the inter-sheet distance is controlled according to the number of insufficient blocks with respect to the number of replenishable blocks. As a result, it is possible to control the developing device so that the toner supply is completed by the next image. For example, it is possible to reduce or prevent the probability of image defects such as insufficient image density and uneven recording. it can. That is, there is a possibility that the toner replenishment may not follow the toner consumption even when the toner replenishment unit (11ab) having a common driving means is used to switch the drive transmission and replenish the toner to the developing devices of a plurality of colors. Can be reduced.

  In the above, the control related to the toner replenishing portion 11ab for the stations Pa and Pb of the yellow and magenta recording colors is shown. Of course, the same control as described above can be performed for the toner replenishing section (11cd) for cyan and black recording colors Pc and Pd. In that case, there may be a case where it is determined that the distance between the sheets should be increased by only one of the two toner replenishing units (11ab, 11cd) according to the shortage of toner supply. Alternatively, there may be a calculation result that causes a difference in the distance between sheets to be enlarged. As described above, when there is a difference between the paper distances to be selected by the two toner replenishing units (11ab, 11cd) according to the shortage of toner supply, the CPU 501 naturally sets the larger one of the two paper distances. It is sufficient to perform control to select and shift to image formation for the next page. In other words, the CPU 501 controls all the toner replenishing units by adopting the control condition of the inter-paper distance of the toner replenishing units among the plurality of toner replenishing units where the more serious (large) toner supply shortage occurs. . Such control can be performed even when three or more toner replenishing units sharing a part of the drive system are arranged.

<Example 2>
In the first embodiment, when the driving rotation number (driving speed) of the motor (111ab) for driving the toner replenishing screw is constant and the supplyable amount is insufficient with respect to the necessary supply amount of toner, the image forming condition In particular, the control for adjusting the inter-paper distance (image forming interval) is shown. On the other hand, when the supplyable amount is insufficient with respect to the required supply amount of toner, the drive rotation speed of the motor 111ab for driving the toner supply screw of the toner transport pipe 116a or 116b is increased (if possible). Configuration is conceivable.

  For example, when the toner supply shortage amount is the first shortage amount, the drive speed of the motor 111ab that drives the toner supply screw of the toner transport pipe 116a or 116b is set as the first drive speed. When the toner supply deficiency is the second deficiency larger than the first deficiency, the driving speed of the motor 111ab that drives the toner supply screw of the toner transport pipe 116a or 116b is set to the first drive. The driving speed is changed to a second driving speed larger than the speed. Such a driving speed can be selected by comparing the number of toner deficient blocks with a specific threshold as described below, for example.

  As described above, it is considered that the shortage of the supplyable amount with respect to the necessary supply amount of the toner can be compensated for by changing the driving speed of the driving means of the supply member for supplying the toner.

  Hereinafter, in this embodiment, when the number of insufficient blocks exceeds a predetermined threshold, the time until the toner supply is completed is shortened by temporarily increasing the number of rotations of the motor 111ab, thereby reducing productivity. A control example for suppressing the above will be described. Also in this embodiment, the overall configuration of the image forming apparatus shown in FIG. 10, the station in FIG. 2, the configuration of the toner replenishment system driving force transmission in FIGS. Suppose that it is common with Example 1.

  However, if the rotational speed of the motor 111ab for driving the toner replenishing screw is constantly increased, there is a risk that the durability of the replenishing screw will be shortened and noise may be generated. Therefore, in this embodiment, the number of rotations is controlled to be temporarily increased when the number of insufficient blocks exceeds a predetermined threshold.

  In the control according to the first embodiment, when the number of blocks to be replenished exceeds the number of replenishable blocks for each image, the paper distance is adjusted and toner is replenished to the developing device until the next image. Controlled to complete. However, there is a possibility that productivity of image formation per hour is lowered by increasing the distance between sheets.

  Here, FIG. 8A shows an example of change in conversion productivity (703) when the inter-paper distance (702) is changed in accordance with the number of insufficient blocks (701). The combination of the number of insufficient blocks (701) and the inter-paper distance (702) in FIG. 8A is the same as that in FIG. If the process speed is the same, as shown in the figure, naturally, if the inter-paper distance (702) is increased, the conversion productivity (703) will decrease accordingly. Here, the converted productivity (703) is indicated by the number of images per minute (ppm). In the control shown in this specification, the distance between sheets can be changed for each image, and the productivity of image formation is not constant. For this reason, in FIG. 8, a quantity called conversion productivity (703) calculated from the distance between sheets is used.

<Paper distance control sequence>
FIG. 9 shows the flow of the inter-paper distance control sequence in this embodiment. The control procedure in FIG. 9 can be stored in, for example, the ROM 502 as a program executed by the CPU 501. As in the first embodiment, in this embodiment, both the necessary supply amount and the supplyable amount of toner are handled according to the number of blocks.

  FIG. 8B shows an example of table data defining the relationship between the number of insufficient blocks (701) and the inter-paper distance (702) to be applied when increasing the rotation speed of the motor 111ab that drives the toner supply screw. Is shown. The table memory that stores the table data is referred to on an external storage device such as the ROM 502 or HDD, or is expanded and stored in the RAM 503.

  In this embodiment, the threshold of the number of insufficient blocks for increasing the number of rotations of the motor 111ab that drives the toner supply screw is 5 blocks or more. If the number of insufficient blocks is equal to or greater than the threshold value (5), the table data in FIG. 8B is used. On the other hand, when the threshold of the number of insufficient blocks is less than 5 blocks, the table data of FIG. 8A configured in the same manner as FIG. 7 of the first embodiment is used. The table data in FIG. 8A includes the cases where the number of insufficient blocks is 5 and 6 as in FIG. 7, but this shows the same control as in FIG. (B) This is for easy comparison with table data. The two records corresponding to the shortage block numbers of 5 and 6 in FIG. 8A are not actually used by the threshold value control.

  Table data for increasing the number of rotations of the motor 111ab for driving the toner replenishing screw is such that the distance between sheets is 40 mm when the number of insufficient blocks (701) is 1 to 5 as shown in FIG. 8B. The Further, when the number of insufficient blocks (701) is six blocks, the distance between sheets is selected to be 93 mm.

  In this embodiment, when the shortage block is equal to or greater than the threshold (5), the rotation speed of the motor 111ab is increased to the default of about 130%, and the tables illustrated in FIGS. 8A and 8B are exemplified. Data is created based on this speed increasing condition.

  In FIG. 9, when the CPU 501 receives an image formation start signal via the interface 505 or the like, the CPU 501 refers to the number of replenishment blocks of the yellow and magenta stations Pa and Pb in step S11 and determines the total amount (necessary supply amount). Ask.

  Next, in step S12, it is confirmed whether or not the total replenishment block number exceeds the replenishable block number (four blocks in this embodiment). If the total number of replenishment blocks is less than or equal to the number of replenishable blocks, the T / D ratio can be maintained without adjusting the inter-sheet distance, and the process proceeds to step S13, where image formation is performed within the normal operation range. To replenish toner.

  On the other hand, if the total number of replenishment blocks exceeds the number of replenishable blocks in step S12, the control in steps S21 to S24 is performed in this embodiment.

  In step S21, it is determined whether or not the number of insufficient blocks is greater than or equal to a threshold value (6). When the number of insufficient blocks is less than the threshold (6), the process proceeds from step S21 to S22, and the distance between sheets to the image of the next page is selected using the table of FIG. Then, control is performed so that the toner supply can be completed until the next image formation.

  On the other hand, if the shortage block is greater than or equal to the threshold value (6), in step S23, a setting is made to increase the rotation speed of the motor 113ab. As a result, the amount of toner that can be replenished to the developing device per unit time increases, and the number of insufficient blocks and the distance between sheets necessary for completing toner replenishment until the next image change. In consideration of this point, the table data of FIG. 8B is configured to select a distance between sheets of 93 mm when the number of insufficient blocks is six.

  If the number of insufficient blocks is greater than or equal to the threshold value (6) in step S21, following step S23, in step S24, the table data of FIG. 8B is used instead of the table data of FIG. The distance between papers to the image is determined.

  The control after step S17 and step S13 is the same as the control procedure of FIG. That is, if there is a shortage of toner supply in step S12, the distance between sheets determined by the table data in FIG. 8A (step S22) or FIG. 8B (step S24) is set in step S17. Is done. Also in this embodiment, subsequent to the image formation (S13), the continuous image formation is controlled via the final page processing determination (step S14). When the final page is processed, step S15 is executed. In step S15 of this embodiment, both the inter-paper distance and the rotation speed of the motor (111ab) that drives the toner supply screw are returned to the default values.

  In the above control, when the rotation speed of the motor 111ab in the present embodiment is a default setting (FIG. 8A), and when the rotation speed of the motor 111ab is increased (FIG. 8B), each table data includes The field of conversion productivity (703) is shown. Comparing the table data of FIG. 8A where the motor 111ab is not accelerated (equivalent to FIG. 7) and the converted productivity (703) of FIG. It can be seen that when the threshold value is 5 or more, there is little decrease in the conversion productivity (703). This is because in the state where the number of insufficient blocks is 5 and 6, the motor 111ab for transporting the toner is accelerated and the toner supply capability is increased, so that the necessary supply amount is replenished even if the amount of increase in the inter-paper distance is small. This is because it can.

  As described above, according to the control example of FIG. 9, the total number of replenished blocks is calculated, and the inter-sheet distance is controlled according to the number of insufficient blocks with respect to the number of replenishable blocks. As a result, it is possible to control the developing device so that the toner supply is completed by the next image. For example, it is possible to reduce or prevent the probability of image defects such as insufficient image density and uneven recording. it can. If the number of insufficient blocks is equal to or greater than the predetermined threshold value (5), the drive speed of the motor (111ab) that drives the toner supply screw serving as the toner supply means is increased. The table data for determining the inter-sheet distance according to the shortage block indicates that when the number of shortage blocks is less than the threshold value (5) (FIG. 8A), the number of shortage blocks is equal to or greater than the threshold value (5) and In the case of increasing the driving speed (FIG. 8B), the configuration is different.

  With such a configuration, in continuous image formation, toner replenishment can be completed with certainty until image formation for the next page is performed. In addition, the drive speed of the motor (111ab) that drives the toner supply screw is increased according to the number of toner deficient blocks, and the table data for determining the inter-sheet distance is changed according to the deficient blocks. For this reason, when the driving speed of the motor (111ab) is increased, it is not necessary to greatly increase the distance between sheets, and the reduction in conversion productivity of image formation can be reduced.

  As described above, according to the present embodiment, toner supply to a plurality of recording color stations is performed by switching driving force transmission (and driving direction) using a common driving unit. Therefore, the possibility that toner replenishment will not follow can be greatly reduced. Thereby, the occurrence of image defects can be reduced, and the productivity of image formation can be kept above a certain level.

  Also in this embodiment, the control related to the toner replenishing portion 11ab for the stations Pa and Pb of the yellow and magenta recording colors is shown. Also in the present embodiment, the same control as described above can be performed for the toner replenishing section (11cd) for cyan and black recording color stations Pc and Pd. In this case, different calculation results can be obtained for the inter-paper distance control and the increase in the driving speed of the motor (111ab) with only one of the two toner replenishing units (11ab, 11cd) according to the shortage of toner supply. there is a possibility. Therefore, also in the present embodiment, the CPU 501 determines the distance between the sheets of the toner replenishing unit and the driving speed of the motor (111ab) where a more serious (large) toner supply shortage occurs among the plurality of toner replenishing units. All the toner replenishing units may be controlled by adopting the control conditions. Such control can be performed even when three or more toner replenishing units sharing a part of the drive system are arranged.

  Further, in this embodiment, an example in which the threshold value of the insufficient block is 5 blocks (or more) is shown. In addition, an example in which the rotation speed of the motor 111ab is 130% as a default when the shortage block is equal to or greater than the threshold value (5) is shown. However, those setting values can be changed to other values by those skilled in the art depending on the specifications of the image forming apparatus.

  In the above description, the electromagnetic clutch 122ab is used to select which of the gear trains 113a and 113b is to transmit the driving force from the gear 112ab to the toner transport driving of the hoppers 115a and 115b (FIG. 4). ). However, the electromagnetic clutch 122ab is not necessarily used to control the transmission destination of the toner conveyance driving force of the gear 112ab. For example, it is conceivable that the rotation shaft of the gear 112ab is supported by a long hole (not shown) or the like and this gear is configured as a so-called peristaltic gear. In this case, the gear 112ab is oscillated by the rotational moment of the gear on the drive source side and transmits the rotational driving force to either of the gear trains 113a and 113b. The switching of the transmission destination of the driving force can be selected by reversing the rotational driving direction of the motor 111ab. Also, those skilled in the art may use an electromagnetic clutch 122ab or an appropriate switching mechanism other than the above-described peristaltic gear configuration.

  In FIG. 9, an example of performing a combination of two image forming conditions, that is, a paper distance control and a change in the driving speed of the motor (111ab) for driving the toner supply screw according to the shortage of toner supply. showed that. However, in the case where a design condition is used in which the remaining capacity of the transport mechanism is sufficiently secured, only the change of the driving speed of the motor (111ab) that drives the toner supply screw is changed to compensate for the shortage of toner supply. It can be considered. In that case, for example, table data (corresponding to FIGS. 7 to 8B) that associates the number of insufficient blocks of toner supply with the driving speed of the motor (111ab) that drives the corresponding toner replenishing screw is used. A configuration to prepare is conceivable. Thus, the driving speed of the motor (111ab) for driving the toner replenishing screw is selected according to the number of insufficient blocks of toner supply, and control is performed so that the toner supply necessary for the next image formation can be performed in continuous image formation. Can do.

  In the first and second embodiments, the necessary toner supply amount (replenishment amount) is calculated by ATR (automatic toner supply) based on video count and inductance detection. In the above description, the toner conveyance control is described based on the concept of “necessary supply amount” (replenishment amount). However, this “required supply amount” (replenishment amount) may be considered as the “consumption amount” of toner. . For example, the video count ATR can be considered as control for predicting the amount of toner consumed to form an image of certain image data.

  For example, in the above-described first embodiment, when continuous image formation is performed by the developing devices 4a and 4b (first and second developing devices), the image forming interval (inter-paper distance) is controlled according to the amount of toner consumption. Technology. And the control technique of Example 1 is comprised as follows. In other words, in the first exemplary embodiment, the CPU 501 (control unit) has the first consumption amount corresponding to the specific number of insufficient blocks in the consumption amount of the (first and second) toners supplied by the toner supply unit 11ab. In this case, continuous image formation is performed at the first image formation interval. Further, when the consumption amount of the (first and second) toners is the second consumption amount larger than the first consumption amount, the second image formation interval is larger than the first image formation interval. The image forming interval is controlled so as to form an image. The table data shown in FIG. 7 is configured to perform such image formation interval (inter-paper distance) control.

  In the second embodiment, the driving speed of the motor 111ab serving as a driving unit that generates driving force for the toner transport pipes 116a and 116b (first and second supply members) is controlled according to the amount of toner consumed. Is done. The control technology for the driving speed of the motor 111ab according to the second embodiment is configured as follows. That is, the CPU 501 (control unit), when the consumption amount of the (first and second) toners supplied by the toner replenishment unit 11ab is the first consumption amount corresponding to the specific number of insufficient blocks, the motor 111ab. (Drive means) is controlled to the first drive speed. Further, when the consumption amount of the (first and second) toner is the second consumption amount larger than the first consumption amount, the motor 111ab (driving means) is set to the second consumption rate larger than the first driving speed. Control to drive speed. Such driving speed control of the motor 111ab (driving means) can be realized by, for example, control using the threshold shown in FIG. 9, and as described above, FIG. 7, FIG. 8 (A), (B) It can also be realized using table data in the same format as above. For example, table data in which the consumption amount of toner (for example, expressed by the number of toner shortage blocks) and the driving speed of the motor 111ab (driving unit) are associated is prepared in the memory. By using this table data, the motor 111ab (driving means) is driven at a first driving speed or a second driving speed higher than the first driving speed in accordance with (expected) toner consumption. Can be controlled.

  Pa to Pd: Station (image forming unit), S: Recording material, Ta to Td ... Toner container, 1a to 1d ... Photosensitive drum, 3a to 3d ... Exposure device, 4a to 4d ... Development device, 7 ... Intermediate transfer belt 11ab (11cd) ... toner replenishing unit, 13 ... fixing device, 41a ... developing sleeve, 42a, 42b ... stirring and conveying screw, 111ab ... motor, 112ab ... gear, 113a, 113b ... gear train, 116a (116b) ... toner conveying Pipe, 119a, 119b ... Toner bottle, 122ab ... Electromagnetic clutch, 500 ... Control device, 501 ... CPU, 502 ... ROM, 503 ... RAM, 504, 505 ... Interface.

Claims (8)

A first developing device and a second developing device for forming toner images of different colors by the first toner and the second toner,
A first toner container and a second toner container for supplying toner to the first developing device and the second developing device, respectively;
A first supply member for supplying the first toner from the first toner container to the first developing device;
A second supply member for supplying the second toner from the second toner container to the second developing device;
Driving means for generating driving force for the first supply member and the second supply member;
Switching means for switching between transmitting the driving force generated by the driving means to the first supply member or transmitting to the second supply member;
A controller for controlling image formation using the first developing device and the second developing device;
With
The control unit calculates a necessary supply amount of the first and second toners necessary for image formation of the toner image, and according to the calculated necessary supply amount, the switching unit, the driving unit, When the first and second toners are supplied to the first developing device and the second developing device, respectively, and continuous image formation is performed by the first developing device and the second developing device, the required supply amount The shortage amount is supplied to the first development device and the second development device between a certain image formation and the subsequent image formation according to the shortage amount of the first and second toners that can be supplied. An image forming apparatus for changing image forming conditions related to the continuous image formation.   The image forming apparatus according to claim 1, wherein the first and second toners are developers containing a magnetic carrier and a non-magnetic toner.   The image forming apparatus according to claim 1, wherein the image forming condition that the control unit changes according to the shortage is an image forming interval from a certain image formation to a subsequent image formation.   The controller performs continuous image formation at a first image forming interval when the shortage amount is the first shortage amount, and the second shortage amount is larger than the first shortage amount. 4. The image forming apparatus according to claim 3, wherein the image forming interval is changed to a second image forming interval that is larger than the first image forming interval.   5. The image forming apparatus according to claim 1, wherein the image forming condition that the control unit changes according to the shortage amount is a driving speed of the driving unit.   The control unit sets the driving speed as the first driving speed when the shortage amount is the first shortage amount, and the shortage amount is a second shortage amount larger than the first shortage amount. The image forming apparatus according to claim 5, wherein the driving speed is changed to a second driving speed that is higher than the first driving speed. A first developing device and a second developing device for forming toner images of different colors by the first toner and the second toner,
A first toner container and a second toner container for supplying toner to the first developing device and the second developing device, respectively;
A first supply member for supplying the first toner from the first toner container to the first developing device;
A second supply member for supplying the second toner from the second toner container to the second developing device;
Driving means for generating driving force for the first supply member and the second supply member;
Switching means for switching between transmitting the driving force generated by the driving means to the first supply member or transmitting to the second supply member;
The switching means and the driving means are controlled, the first and second toners are supplied to the first developing device and the second developing device, and the first developing device and the second developing device are used. A control unit for controlling image formation;
With
In the case where continuous image formation is performed by the first developing device and the second developing device, the control unit determines the first image forming interval when the consumption amounts of the first and second toners are the first consumption amount. In the case where the continuous image formation is performed, and the consumption amount of the first and second toners is the second consumption amount larger than the first consumption amount, the second image larger than the first image formation interval. An image forming apparatus that controls an image forming interval so as to perform continuous image formation at the forming interval. A first developing device and a second developing device for forming toner images of different colors by the first toner and the second toner,
A first toner container and a second toner container for supplying toner to the first developing device and the second developing device, respectively;
A first supply member for supplying the first toner from the first toner container to the first developing device;
A second supply member for supplying the second toner from the second toner container to the second developing device;
Driving means for generating driving force for the first supply member and the second supply member;
Switching means for switching between transmitting the driving force generated by the driving means to the first supply member or transmitting to the second supply member;
The switching means and the driving means are controlled, the first and second toners are supplied to the first developing device and the second developing device, and the first developing device and the second developing device are used. A control unit for controlling image formation;
With
When continuous image formation is performed by the first developing device and the second developing device, the control unit controls the first driving unit when the consumption amount of the first and second toners is the first consumption amount. And when the consumption amount of the first and second toners is a second consumption amount larger than the first consumption amount, the drive means is larger than the first drive speed. An image forming apparatus controlled to a second driving speed.

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